TWI706695B - Undulators, magnetic field sensors, undulator modules, free electron lasers, lithographic systems, and methods for determining a magnetic field strength of an undulator module - Google Patents

Abstract

Apparatus and associated methods for determining a magnetic field strength of an undulator module are disclosed. One such apparatus comprises an undulator module and a magnetic field sensor. The magnetic field sensor comprises a body and a sensing element operable to measure a magnetic field. The undulator module comprises a support structure and a plurality of periodic magnetic structures. The periodic structures are supported by the support structure and being arranged around and extending parallel to a central axis. The undulator module is provided with at least one opening for receiving the sensing element of the magnetic field sensor. The undulator module and the magnetic field sensor comprise complementary alignment features that provide releasable engagement between the magnetic field sensor and the undulator module such that the sensing element of the magnetic field sensor can be repeatably positioned within the undulator module in substantially the same position relative to the central axis.

Description

The undulator, magnetic field sensor, undulator module, free electron laser, lithography system, and method for determining the magnetic field strength of the undulator module

The invention relates to a device and an associated method for determining the magnetic field in the undulator. In detail, but not exclusively, the undulator can form part of a free electron laser, which can be used by a lithography system to generate radiation.

A lithography device is a machine that is constructed to apply a desired pattern to a substrate. The lithography device can be used, for example, in the manufacture of integrated circuits (IC). The lithography device can, for example, project a pattern from a patterned device (for example, a photomask) onto a layer of radiation sensitive material (resist) provided on the substrate.

The wavelength of the radiation used by the lithography device to project the pattern onto the substrate determines the smallest size of the feature that can be formed on that substrate. Compared to conventional lithography devices (which can, for example, use electromagnetic radiation with a wavelength of 193 nm), lithography devices that use EUV radiation, which is electromagnetic radiation with a wavelength in the range of 4 nm to 20 nm, can be used Small features are formed on the substrate.

One potential source of the radiation beam used for lithography is a free electron laser. The free electron laser guides the focused electron beam through the periodic magnetic field in the undulator to stimulate the coherent emission of radiation. The output power of a free electron laser depends on the periodic magnetic field generated by the undulator, which can change over time. Therefore, it is necessary to periodically monitor the periodic magnetic field in the undulator of the free electron laser.

One objective of the present invention is to prevent or alleviate at least one problem of the prior art technology. question.

According to a first aspect of the present invention, there is provided a device including a undulator module and a magnetic field sensor. The magnetic field sensor includes: a body; and a sensor operable to measure a magnetic field Test element; the undulator module includes: a support structure; and a plurality of periodic magnetic structures, the periodic structures are supported by the support structure, and are arranged around a central axis and extend parallel to the central axis Wherein the undulator module has at least one opening for receiving the sensing element of the magnetic field sensor; wherein the undulator module and the magnetic field sensor include complementary alignment features, which are in the magnetic field A releasable engagement is provided between the sensor and the undulator module, so that the sensing element of the magnetic field sensor can be repeatedly positioned on the undulator module in substantially the same position relative to the central axis s.

The device of the first aspect allows the sensing element of the magnetic field sensor to move between the following two: (a) in an accurate position in the undulator module, which is in the undulator mode Near the central axis of the group, so that the strength and/or direction of the magnetic field at that location can be determined; and (b) at a location outside the undulator module, where the sensing element is not subject to significant level radiation or radioactivity. It will be appreciated that a position within the undulator module near the central axis of the undulator module can be sufficiently close to the central axis to allow the measurement of the magnetic field from that position to the center Any position on the axis where the magnetic field (strength and/or direction) makes useful judgments. The sensing element of the magnetic field sensor can, for example, be periodically and accurately positioned near the central axis of the undulator module, while no electron beam passes through the undulator module. In addition, it can be positioned near the central axis of the undulator module for a relatively short period of time, for example, only long enough to take a measurement. This allows the magnetic field to be measured periodically near the central axis of the undulator module, while limiting the level of radioactivity experienced by the sensing element. Allowing the magnetic field sensor to be removed from the opening defined by the undulator module will allow it to be recalibrated between measurements and limit the amount of damage it can withstand due to radioactivity.

The undulator module can form a part of a free electron laser. The plurality of periodic magnetic structures are operable to generate a periodic magnetic field for guiding an electron beam along a periodic path, so that the electrons in the electron beam interact with the radiation in the undulator module Function to stimulate the emission of coherent radiation to provide a radiation beam. An area around the central axis of a undulator module can be regarded as a "good field area". The good field area may be a volume around the central axis, wherein for a given position along the central axis of the undulator module, the magnitude and direction of the magnetic field in the volume are substantially constant. The electron beam is close to the central axis of the undulator module (ie, in the good field region) and propagates in a region maintained under high vacuum (for example, in an evacuated beam tube).

High-energy electrons from the electron beam can be scattered by residual gas molecules in this region, for example, by Rutherford scattering. These scattered electrons can be incident on the periodic magnetic structures of the undulator module to generate electromagnetic showers or cascades of one of lower energy electrons and photons, which can cause the magnetic structures to be partially demagnetized . Over time, this demagnetization of the magnetic structures results in deformation of the trajectory followed by the electrons passing through the undulator module, thereby causing loss of conversion efficiency. It is necessary to periodically monitor the magnetic field strength along the central axis of the undulator module. Once the conversion efficiency of the free electron laser drops below an acceptable level, the periodic magnetic structures can be retuned (remagnetized) or replaced.

From one or more measurements of the magnetic field intensity near the axis of the undulator module, the magnetic field intensity on the central axis can be determined, for example, by modeling or extrapolation. In order to accurately determine the magnetic field intensity at the central axis of the undulator module, it is important to locate the magnetic sensor in the substantially same position relative to the undulator module for each measurement.测Components. This is achieved by the alignment features.

The first aspect of the present invention allows sampling the magnetic field in the undulator module without disassembling the undulator module, because the at least one opening allows the sensing element of the magnetic field sensor Located in the undulator. This can be advantageous because the undulator The disassembly of the module can be time-consuming. In addition, the components of the undulator module closer to the central axis can be radioactive for a period of time after the electron beam has been switched off. Because the disassembly of the undulator module can expose these components of the undulator module, it must contain generated radiation, or the undulator module should be allowed to cool for a period of time before disassembly. This increases the disassembly complexity of the undulator module and/or increases the downtime of the free electron laser. The at least one opening and the central axis of the undulator module face a relatively small solid angle, and therefore, the amount of radiation that can be emitted from the undulator module through the at least one opening is small.

The position of the sensing element of the magnetic field sensor can be specified by three coordinates in any suitable coordinate system.

The alignment features can be configured to allow the sensing element of the magnetic field sensor to be positioned within the opening within a specified tolerance distance relative to the fixed position of the undulator module. The specified tolerance distance may be 10 microns or less, for example, 2 microns or less. Each of the three coordinates specifying the position of the sensing element relative to the fixed position may be less than the specified tolerance distance.

The complementary alignment features may include one or more protrusions on one of the magnetic field sensor and the undulator module, and the other of the magnetic field sensor and the undulator module One or more complementary recesses on the person.

The releasable engagement between the magnetic field sensor and the undulator module provided by the complementary alignment features allows the sensing element of the magnetic field sensor to be reproducibly positioned in substantially the same orientation In the undulator module.

This may be advantageous when, for example, the sensing element is operable to determine the component of the magnetic field in a single sensing direction (relative to the magnetic field sensor). For example, the sensing element may include a single Hall probe. In order to accurately determine the magnetic field strength at the central axis of the undulator module, it may be important to locate the sensing element of the magnetic sensor in substantially the same orientation for each measurement of the magnetic field ( This allows the sensing element to determine the same component of the magnetic field for each measurement). This can be achieved by the alignment features to make. In an alternative embodiment, the sensing element is operable to determine the magnitude of the magnetic field. For example, the sensing element may include a plurality of Hall probes (for example, three), each of which is operable to determine a different component of the magnetic field, from which the magnitude of the magnetic field can be determined.

The orientation of the sensing element of the magnetic field sensor can be specified by three angles. The at least one opening for receiving the sensing element of the magnetic field sensor may extend along an opening axis. The orientation of the sensing element of the magnetic field sensor can be specified by each of the following: the body of the magnetic field sensor rotates around the opening axis; and if the body of the magnetic field sensor is relative to the opening axis The two tilt angles. By requiring the position of the sensing element of the magnetic field sensor to be within the specified tolerance distance, the two inclination angles of the body of the magnetic field sensor with respect to the opening axis can be well constrained. By requiring the position of the sensing element of the magnetic field sensor to be within the specified tolerance distance, the rotation angle of the body of the magnetic field sensor around the opening axis can be less affected than the two tilt angles constraint.

The alignment features may be configured to allow the sensing element of the magnetic field sensor to be positioned inwardly within the opening in a specified volume of a desired orientation. The specified capacity limit may be 1 milliradian or less, for example, 0.1 milliradian. Each of the three angles that specify the orientation of the sensing element relative to the desired orientation may be smaller than the specified tolerance direction.

The complementary alignment features can be configured such that when the magnetic field sensor is engaged with the undulator module, the sensing element of the magnetic field sensor is in one of a limited number of fixed orientations. The alignment features can provide any number of fixed orientations.

For example, in some embodiments, the alignment features can provide a single fixed orientation. This prevents, for example, the magnetic field sensor and the undulator module with the sensing element from engaging in two different orientations for two different measurements, thus ensuring that the measurements are consistent.

Alternatively, the alignment features may provide two or more fixed orientations. This may allow the magnetic field sensor and the undulator module with the sensing element to engage in two or more different orientations, thereby allowing for (for example) determination of two or more of the magnetic field Weight. This can improve the accuracy with which the magnetic field on the central axis can be determined. Compared with the embodiment in which the magnetic field sensor can only be engaged with the undulator module with the sensing element in a single orientation, the magnetic field sensor is allowed to interact with the undulator module with the sensing element. The meshing of the groups in two different orientations provides a significant improvement. Compared with the embodiment in which the magnetic field sensor can only be engaged with the undulator module with the sensing element in two different orientations, it allows the magnetic field sensor to interact with the undulator with the sensing element The engagement of the device modules in three or more different orientations can provide a minor improvement.

The undulator module can have a plurality of openings for receiving the sensing element of a magnetic field sensor.

This allows the magnetic field to be sampled in a plurality of different positions within the undulator module.

The device may include a plurality of magnetic field sensors.

For example, for an embodiment including a plurality of different openings, a different magnetic field sensor can be used for each of the plurality of openings. Alternatively, a single magnetic field sensor may be used for more than one of the plurality of openings. For example, a single magnetic field sensor can be used for all of the plurality of openings. Alternatively, the plurality of openings may include a plurality of openings, and a different single magnetic field sensor may be used for each different set of openings. Each different set of openings can have different alignment features. The central axis can form a reference axis for a cylindrical coordinate system of the undulator module. Therefore, a point in the undulator module can be specified by an axial position, a radial position and an azimuthal position. The axial position of a point can be the (signed) vertical distance between that point and a selected reference plane perpendicular to the central axis. The radial position of a point can be the vertical distance between that point and the central axis. The azimuth position of a point may be an angle between a plane passing through the central axis and the other point and a plane passing through the central axis and a reference line.

At least one of the openings for accommodating the sensing element of a magnetic field sensor can be provided in the supporting structure, and can be between the azimuth angle positions of the two of the periodic magnetic structures It extends radially at the azimuth position.

This allows the sensing element of a magnetic field sensor to extend through the opening and between two adjacent periodic magnetic structures. Advantageously, this allows the sensing element to be positioned close to the central axis of the undulator module (e.g., adjacent to an evacuated beam tube).

Each of the periodic magnetic structures may include a plurality of magnets, and each of the plurality of magnets is operable to generate a magnetic field, wherein the sensing elements of a magnetic field sensor At least one of the openings is at substantially the same azimuth position as one of the periodic magnetic structures and at the substantially same axial position as one of the magnets of the periodic magnetic structure Extend radially.

This allows the sensing element of a magnetic field sensor to be placed adjacent to one of the magnets of one of the periodic magnetic structures, where the magnetic field is dominated by the magnetic field of the other magnet. Therefore, this allows monitoring of the magnetic field of a separate magnet.

A plurality of magnets of a given periodic structure may extend axially, so that the polarization directions of the plurality of magnets form a repeating pattern in an axial direction along a length of the periodic magnetic structure. For example, in one embodiment, in the axial direction, the polarization directions of the plurality of magnets alternate between a positive axial direction and a negative axial direction. In another embodiment, the plurality of magnets are configured to form a Halbach array.

Each of the periodic magnetic structures may further include a plurality of ferromagnetic elements configured to direct the magnetic field generated by the plurality of magnets toward the central axis of the undulator module. For example, the plurality of ferromagnetic elements may be alternately arranged with the plurality of magnets in an axial direction.

At least one of the openings for receiving the sensing element of a magnetic field sensor may include a bore in one of the ferromagnetic elements extending to one of the periodic magnetic structures hole. For example, at least one of the openings used to receive the sensing element of a magnetic field sensor may be at substantially the same azimuth position and period with one of the periodic magnetic structures One of the ferromagnetic elements of the sexual magnetic structure Extend radially at the same axial position qualitatively. The magnetic field is stronger inside the ferromagnetic elements, and therefore the accuracy of the measurement can be increased (using the same sensing element).

The opening may include a hole in the supporting structure of the undulator module.

The undulator module can be a plane undulator module including two periodic magnetic structures. Alternatively, the undulator module may be a spiral undulator module including one of four periodic magnetic structures.

According to a second aspect of the present invention, there is provided a magnetic field sensor, including: a body; and a sensing element operable to measure a magnetic field; wherein the magnetic field sensor includes an alignment feature, which A releasable engagement is provided between the magnetic field sensor and a undulator module, so that the sensing element of the magnetic field sensor can be repeatedly positioned in the undulator in substantially the same position relative to the central axis Inside the module.

According to a third aspect of the present invention, there is provided a undulator module including: a supporting structure; and a plurality of periodic magnetic structures, the periodic structures being supported by the supporting structure and surrounding a central axis And are arranged and extend parallel to the central axis; wherein the undulator module has at least one opening for receiving a sensing element of a magnetic field sensor; wherein the undulator module includes an alignment feature, It provides a releasable engagement between the magnetic field sensor and the undulator module, so that the sensing element of the magnetic field sensor can be repeatedly positioned at the same position relative to the central axis. Inside the undulator module.

According to a fourth aspect of the present invention, there is provided a undulator module. The undulator module includes a plurality of periodic magnetic structures. The periodic structures are arranged around a central axis and parallel to the central axis. It is extended and operable to generate a periodic magnetic field for guiding an electron beam along a periodic path, so that the electrons in the electron beam interact with the radiation in the undulator module to stimulate coherence The emission of radiation provides a beam of radiation; wherein each of the periodic magnetic structures includes a plurality of magnets and a plurality of ferromagnetic elements, each of the plurality of magnets is operable to generate a magnetic field, and the Each of the plurality of ferromagnetic elements is configured to guide the magnetic field generated by the plurality of magnets Towards the central axis; wherein at least one of the ferromagnetic elements of at least one of the periodic magnetic structures is provided with a device for determining the permeability of the ferromagnetic element.

The magnetic permeability of the ferromagnetic elements depends on the magnetic field applied by the plurality of magnets. Therefore, the device for determining the permeability of the ferromagnetic elements of the second aspect of the invention provides an indirect measurement of the magnetic field provided by the magnets.

The undulator module can form a part of a free electron laser. The plurality of periodic magnetic structures are operable to generate a periodic magnetic field for guiding an electron beam along a periodic path, so that the electrons in the electron beam interact with the radiation in the undulator module Function to stimulate the emission of coherent radiation to provide a radiation beam. An area around the central axis of a undulator module can be regarded as a "good field area". The good field area may be a volume around the central axis, wherein for a given position along the central axis of the undulator module, the magnitude and direction of the magnetic field in the volume are substantially constant. The electron beam is close to the central axis of the undulator module (ie, in the good field region) and propagates in a region maintained under high vacuum (for example, in an evacuated beam tube).

High-energy electrons from the electron beam can be scattered by residual gas molecules in this region, for example, via Rutherford scattering. These scattered electrons can be incident on the periodic magnetic structures of the undulator module, thereby generating an electromagnetic shower or cascade of one of lower energy electrons and photons. This in turn can cause the magnetic structures to be at least partially demagnetized and/or can change one or more properties of the ferromagnetic materials (for example, the magnets and the ferromagnetic elements) in the magnetic structures, and thus change the The magnetic field on the central axis of the undulator module. Over time, these effects cause deformation of the trajectory followed by the electrons passing through the undulator module, causing loss of conversion efficiency. Therefore, it is necessary to periodically monitor the magnetic field strength along the central axis of the undulator module. Once the conversion efficiency of the free electron laser drops below an acceptable level, the periodic magnetic structures can be retuned (remagnetized) or replaced.

From one or more measurements of the magnetic permeability of the ferromagnetic elements, the magnetic field strength on the central axis of the undulator module can be determined, for example, by modeling or extrapolation.

The device for determining the permeability of the ferromagnetic element may include: a coil set including one or more coils of wires wound around the ferromagnetic element; and a power supply that is operable to An alternating current is applied to a coil of the coil set; and a device configured to determine an inductance of a coil of the coil set or a voltage induced in a coil of the coil set.

When the power supply applies an alternating current to one of the coils of the coil group, an alternating magnetic field is generated in the ferromagnetic element. This in turn will induce a voltage in any coils wound around the ferromagnetic element. The inductance and the induced voltage depend on the permeability of the ferromagnetic element. Therefore, by determining the inductance from a coil of the coil group or a voltage induced in a coil of the coil group, the permeability of the ferromagnetic element can be determined.

The coil of the coil group whose inductance is determined can be the same coil as the coil to which the alternating current is applied by the power supply. Alternatively, the AC power can be applied to a first coil by the power supply, and the inductance of a second coil or the induced voltage in the second coil can be determined.

According to a fifth aspect of the present invention, there is provided a free electron laser, which includes: an electron source for generating an electron beam including a plurality of relativistic electron beams; and a undulator, which is configured To receive the electron beam and guide the electron beam along a periodic path, so that the electron beam interacts with the radiation in the undulator, thereby stimulating the emission of radiation and providing a radiation beam, wherein the wave The undulator includes the device according to the first aspect of the invention or the undulator module according to the fourth aspect of the invention.

According to a sixth aspect of the present invention, there is provided a lithography system comprising: a free electron laser according to the fifth aspect of the present invention; and at least one lithography device, one of the at least one lithography device Each is configured to receive at least a portion of at least one radiation beam generated by the free electron laser.

According to a seventh aspect of the present invention, there is provided a method for determining the strength of a magnetic field of a undulator module, the method comprising: a magnetic field sensor including a sensing element Inserted into an opening in the undulator module so that an alignment feature on the magnetic field sensor cooperates with a complementary alignment feature on the undulator module, so that the sensing element is relative to the A central axis of the undulator module is accurately positioned at a measurement position; the sensing element is used to measure a magnetic field at the measurement position; and the opening in the undulator module is removed Magnetic field sensor.

The method may include: inserting a magnetic field sensor including a sensing element into each of the plurality of openings in the undulator module, so that an alignment feature on the magnetic field sensor and A complementary alignment feature on the undulator module cooperates so that the sensing element is accurately positioned at one of a plurality of measurement positions with respect to a central axis of the undulator module; using the sensor The measuring element measures a magnetic field at the measuring position; and the magnetic field sensor is removed from each of the plurality of openings in the undulator module.

A different magnetic field sensor can be used for each of the plurality of openings. Alternatively, a single magnetic field sensor may be used for more than one of the plurality of openings. For example, a single magnetic field sensor can be used for all of the plurality of openings. Alternatively, the plurality of openings may include a plurality of openings, and a different single magnetic field sensor may be used for each different set of openings. Each different set of openings can have different alignment features.

For the embodiment in which the method uses a plurality of magnetic field sensors, the different magnetic field sensors can be inserted substantially simultaneously. Alternatively, the different magnetic field sensors can be inserted sequentially.

The method may further include: determining a magnetic field at a central axis of the undulator module from the measured magnetic field at the or each measurement position.

For example, the magnetic field strength on the central axis can be determined by modeling or extrapolation.

According to an eighth aspect of the present invention, there is provided a method for determining the magnetic field strength of an undulator module including a plurality of periodic magnetic structures, the periodic structures being arranged around a central axis and parallel to Extending from the central axis, the periodic magnetic junctions Each of the structures includes a plurality of magnets alternately arranged with a plurality of ferromagnetic elements, and the method includes: determining the magnetism of at least one of the ferromagnetic elements of at least one of the periodic magnetic structures Conductivity.

The permeability of the ferromagnetic elements depends on the magnetic field applied by the plurality of magnets and the properties of the materials used to form the ferromagnetic elements. Therefore, determining the permeability of the ferromagnetic elements provides an indirect measurement of the magnetic field provided by the magnets. Additionally or alternatively, the change in the permeability of the ferromagnetic elements when the magnetic field provided by the magnets remains constant may indicate a change in one or more of the properties of the ferromagnetic elements.

The method may include determining the permeability of the ferromagnetic elements of the periodic magnetic structures.

The method may include: determining the magnetic field at a central axis of the undulator module from the measured magnetic permeability of the plurality of the ferromagnetic elements of the plurality of the periodic magnetic structures.

For example, the magnetic field strength on the central axis can be determined by modeling or extrapolation.

The various aspects and features of the present invention explained above or below can be combined with various other aspects and features of the present invention, which will be readily apparent to those familiar with the art.

8: opening

10: Faceted field mirror device

11: Faceted pupil mirror device

13: Mirror

14: Mirror

21: Injector

22: Linear accelerator

23: buncher compressor

24: undulator

26: Electronic reducer

40: beam fittings

41: Central axis

42a: Periodic magnetic structure

42b: Periodic magnetic structure

42c: Periodic magnetic structure

42d: Periodic magnetic structure

44: Magnet

46: spacer element

48: Ferromagnetic element

50: Supporting structure

52: recessed part

53: recessed part

54: recessed part

62: cooling channel

62a: Connector

64: cooling channel

64a: connector

100: beam cutoff

200: undulator module

210: open

211: Opening axis

220: opening

221: opening axis

230: opening

231: Opening axis

300: Magnetic field sensor

302: body

302a: Meshing part

302b: Protruding part

304: sensing element

306: protrusion

310: Magnetic field sensor

312: Body

312a: Meshing part

312b: Protruding part

314: sensing element

316: protrusion

320: Magnetic field sensor/magnetic sensor

322: body

322a: meshing part

322b: Protruding part

324: sensing element

326: protruding part

400: Coil

410: Groove

B: Extreme ultraviolet radiation beam

BDS: beam delivery system

B _a : branch radiation beam

B _a ': patterned radiation beam

B _b : branch radiation beam

B _n : branch radiation beam

E: electron beam

FEL: Free Electron Laser

IL: lighting system

LA _a : Lithography device

LA _b : Lithography device

LA _n : Lithography device

LS: Lithography System

MA: Patterned device

MT: supporting structure

PS: Projection system

SO: radiation source

WT: substrate table

W: substrate

The embodiment of the present invention will now be described with reference to the accompanying schematic drawings as an example only. In these drawings:-Figure 1 is an example of a lithography system including a free electron laser according to an embodiment of the present invention Schematic illustration;-FIG. 2 is a schematic illustration of a lithography device forming part of the lithography system of FIG. 1;-FIG. 3 is a schematic illustration of a free electron laser forming part of the lithography system of FIG. 1; -Figure 4 is a schematic illustration of a cross-sectional view of a part of the undulator module in a plane parallel to the axis of the undulator module, the undulator module forming part of the free electron laser of Figure 3; -Figure 5 is a schematic illustration of a cross-sectional view of a portion of the undulator module of Figure 4 in a plane perpendicular to the axis of the undulator module;-Figure 6A shows the undulator adjacent to that shown in Figure 5 The enlarged part of the magnetic field sensor of the cross-sectional view of the part of the undulator module;-Figure 6B shows the cross-sectional view of the part adjacent to the undulator module similar to the undulator module shown in Figure 5 The enlarged part of another magnetic field sensor;-Figure 7 shows the enlarged part of the magnetic field sensor adjacent to the cross-sectional view of the part of the undulator module shown in Figure 5;-Figure 8A shows that waves can be formed The ferromagnetic element of the part of the oscillator module; and-Fig. 8B shows the ferromagnetic element of Fig. 8A with a device for determining its permeability.

Fig. 1 shows a lithography system LS according to an embodiment of the present invention. The lithography system LS includes a radiation source SO, a beam delivery system BDS, and a plurality of lithography devices LA _a to LA _n (for example, eight lithography devices). The radiation source SO is configured to generate an extreme ultraviolet (EUV) radiation beam B (which may be referred to as the main beam).

The beam delivery system BDS includes beam splitting optics, and optionally includes beam expansion optics and/or beam shaping optics. The main radiation beam B is split into a plurality of radiation beams B _a to B _n (which can be called branch beams), and each of the plurality of radiation beams B _a to B _n is directed to the lithography by the beam delivery system BDS One of the devices LA _a to LA _n is different.

The selected beam expansion optics (not shown in the figure) are configured to increase the cross-sectional area of the radiation beam B. Advantageously, this reduces the thermal load on the mirror surface downstream of the beam expansion optics. This allows the mirror surface downstream of the beam expansion optics to be of lower specifications, with less cooling and Therefore it is less expensive. Additionally or alternatively, it may allow the downstream mirror to be closer to normal incidence. For example, the beam expansion optics may be operable to expand the main beam B from about 100 microns to more than 10 cm before the main beam B is split by the beam splitting optics.

In an embodiment, the branch radiation beams B _a to B _n are each directed through a respective attenuator (not shown in the figure). Each attenuator to a respective branch in the radiation beam B _a is configured to transfer to its corresponding B _n lithography apparatus LA _a branch prior to the adjustment of the radiation beam LA _n B _a to B _n of intensity.

The radiation source SO, the beam delivery system BDS, and the lithography devices LA _a to LA _n can all be constructed and configured such that they can be isolated from the external environment. Vacuum can be provided in at least part of the radiation source SO, the beam delivery system BDS, and the lithography devices LA _a to LA _n in order to minimize the absorption of EUV radiation. Different parts of the lithography system LS may have vacuums at different pressures (ie, maintained at different pressures below atmospheric pressure).

2, the lithography apparatus LA _a includes an illumination system IL, a support structure MT configured to support a patterned device MA (for example, a photomask), a projection system PS, and a substrate table WT configured to support a substrate W . The illumination system IL is configured to adjust the branch radiation beam B _a received by the lithography device LA _a before the branch radiation beam B _{a is} incident on the patterning device MA. The projection system PS is configured to project the radiation beam B _a ′ (now patterned by the patterning device MA) onto the substrate W. The substrate W may include a previously formed pattern. In this situation, the lithography device aligns the patterned radiation beam B _a ′ with the pattern previously formed on the substrate W.

The received by the lithography apparatus LA _a branch B _a radiation beam from a beam delivery system enclosure through the BDS is transmitted to the structure of the illumination system IL in the opening 8 of the illumination system IL. Optionally, the branch radiation beam _Ba may be focused to form an intermediate focus at or near the opening 8.

The illumination system IL may include a faceted field mirror device 10 and a faceted pupil mirror device 11. The faceted field mirror device 10 and the faceted pupil mirror device 11 together provide a desired cross-sectional shape and _a desired angular distribution to the radiation beam Ba. The radiation beam B _{a is} transmitted from the illumination system IL, and is incident on the patterned device MA held by the support structure MT. The patterned device MA reflects and patterns the radiation beam to form a patterned beam _Ba '. In addition to the faceted field mirror device 10 and the faceted pupil mirror device 11 or instead of the faceted field mirror device 10 and the faceted pupil mirror device 11, the illumination system IL may also include other mirror surfaces or devices. For example, the illumination system IL may include an array of independently movable mirrors. The independently movable mirror can, for example, be less than 1 mm wide. The independent movable mirror may, for example, be a microelectromechanical system (MEMS) device.

After being redirected (eg, reflected) from the patterned device MA, the patterned radiation beam Ba′ enters the projection system PS. The projection system PS includes a plurality of mirrors 13, 14 configured to project the radiation beam _Ba ′ onto the substrate W held by the substrate table WT. The projection system PS can apply a reduction factor to the radiation beam to form an image with features smaller than the corresponding features on the patterned device MA. For example, a reduction factor of 4 can be applied. Although the projection system PS has two mirrors in FIG. 2, the projection system may include any number of mirrors (for example, six mirrors).

The lithography device LA _{a is} operable to impart a pattern to the radiation beam B _{a in} the cross-section of the radiation beam B _a and project the patterned radiation beam onto a target portion of the substrate, thereby exposing the target portion of the substrate to the Patterned radiation. The lithography device LA _a can be used, for example, in a scanning mode, in which when the pattern imparted to the radiation beam B _a 'is projected onto the substrate W, the support structure MT and the substrate table WT are simultaneously scanned (ie, dynamic exposure ). The speed and direction of the substrate table WT relative to the support structure MT can be determined by the reduction ratio and image reversal characteristics of the projection system PS.

Referring again to FIG. 1, the radiation source SO is configured to generate an EUV radiation beam B having sufficient power to supply each of the lithography devices LA _a to LA _n . As mentioned above, the radiation source SO may include a free electron laser.

3 is a schematic description of a free electron laser FEL including an injector 21, a linear accelerator 22, a buncher compressor 23, an undulator 24, an electronic reducer 26, and a beam stopper 100.

The injector 21 is configured to generate a focused electron beam E, and includes an electron source (for example, a thermionic cathode or a photocathode) and an accelerating electric field. The electrons in the electron beam E are further accelerated by the linear accelerator 22. In one example, the linear accelerator 22 may include: a plurality of radio frequency cavities, which are axially spaced apart along a common axis; and one or more radio frequency power sources, which are operable to transfer the electron beams therebetween. Control the electromagnetic field along the common axis to accelerate each electron beam. The cavity may be a superconducting radio frequency cavity. Advantageously, this allows: a relatively large electromagnetic field to be applied in a high-action interval cycle; a larger beam aperture, thereby causing less loss due to the wake field; and increased transmission to the beam (as opposed to dissipating through the cavity wall) ) The fraction of radio frequency energy. Alternatively, the cavity is conventionally conductive (ie, not superconducting), and may be formed of, for example, copper. Other types of linear accelerators can be used, such as, for example, a laser wake field accelerator or an anti-free electron laser accelerator.

Optionally, the electron beam E passes through the buncher compressor 23 arranged between the linear accelerator 22 and the undulator 24. The buncher compressor 23 is configured to spatially compress the existing electron bunches in the electron beam E. One type of buncher compressor 23 includes a radiation field directed transverse to the electron beam E. The electrons in the electron beam E interact with radiation and converge with other nearby electrons. Another type of buncher compressor 23 includes a magnetic orbital curve, where the length of the path followed by the electron as it passes through the orbital curve depends on the energy of the electron. This type of bunching compressor can be used to compress the bunch of electrons that have been accelerated by a plurality of resonant cavities in the linear accelerator 22.

The electron beam E then passes through the undulator 24. Generally, the undulator 24 includes a plurality of modules. Each module includes a periodic magnetic structure that is operable to generate a periodic magnetic field and is configured to guide the relativity generated by the injector 21 and the linear accelerator 22 along the periodic path within the module Electron beam E. The periodic magnetic field generated by each undulator module causes the electrons to follow an oscillation path around the central axis. Therefore, in each undulator module, electrons generally radiate electromagnetic radiation in the direction of the center axis of the other undulator module.

The path followed by the electrons can be sinusoidal and planar, where the electrons periodically traverse the central axis. Alternatively, the path may be helical, where the electrons rotate around a central axis. The type of oscillation path can affect the polarization of the radiation emitted by the free electron laser. For example, a free electron laser that causes electrons to propagate along a spiral path can emit elliptically polarized radiation, which may be ideal for exposing the substrate W by some lithography devices.

As electrons move through each undulator module, they interact with the electric field of the radiation, thereby exchanging energy with the radiation. Generally speaking, unless conditions are close to resonance conditions, the amount of energy exchanged between electrons and radiation will oscillate rapidly. Under resonance conditions, the interaction between the electrons and the radiation causes the electrons to bunch together into micro bunches that are modulated by the wavelength of the radiation in the undulator, and stimulate the coherent emission of the radiation along the central axis. The resonance condition can be given by the following formula:

Where λ _em is the wavelength of radiation, λ _u is the undulator period of the undulator module through which the electron is propagating, γ is the Lorentz factor of the electron, and K is the undulator parameter. A depends on the geometry of the undulator 24: for a helical undulator that generates circularly polarized radiation, A = 1; for a plane undulator, A = 2; and for generating elliptically polarized radiation (that is, neither Circular polarization, also nonlinear polarization) helical undulator, 1< A <2. In practice, each electron beam will have an energy spread, but this spread can be minimized as much as possible (by generating an electron beam E with low emissivity). The undulator parameter K is usually about 1 and is given by:

Where q and m are charge and electron mass, respectively, B ₀ is the amplitude of the periodic magnetic field, and c is the speed of light.

The resonance wavelength λ _em is equal to the first harmonic wavelength spontaneously radiated by electrons moving through each undulator module. Free electron laser FEL can be operated in self-amplified spontaneous emission (SASE) mode. Operation in the SASE mode may require the low energy spread of the electron beams in the electron beam E before the electron beam E enters each undulator module. Alternatively, the free electron laser FEL may include a seed radiation source that can be amplified by stimulated emission in the undulator 24. The free electron laser FEL can be operated as a recirculating amplifier free electron laser (RAFEL), where part of the radiation generated by the free electron laser FEL is used to inoculate the further generation of radiation.

The electrons moving through the undulator 24 can cause the amplitude of the radiation to increase, that is, the free electron laser FEL can have a non-zero gain. The maximum gain can be achieved when the resonance conditions are met or when the conditions are close but slightly off resonance.

The electrons that meet the resonance condition as they enter the undulator 24 will lose (or gain) energy as they emit (or absorb) radiation, so that the resonance condition is no longer satisfied. Therefore, in some embodiments, the undulator 24 may be tapered. That is, the amplitude of the periodic magnetic field and/or the undulator period λ _u may vary along the length of the undulator 24 so as to converge the electron beams as they are guided through the undulator 24 Stay at or close to resonance. The taper can be achieved by varying the amplitude of the periodic magnetic field and/or the undulator period λ _u within each undulator module and/or between different modules. Additionally or alternatively, the taper can be achieved by varying the helicity of the undulator 24 (thereby varying the parameter A) within each undulator module and/or between different modules.

The area surrounding the central axis of each undulator module can be regarded as a "good field area". The good field area may be a volume around the central axis, wherein for a given position along the central axis of the undulator module, the magnitude and direction of the magnetic field within the volume are substantially constant. The bunch of electrons propagating in the good field region can satisfy the resonance condition of equation (1) and will therefore amplify the radiation. In addition, the electron beam E propagating in the good field region should not experience significant unexpected damage due to the uncompensated magnetic field. That is, electrons propagating through the good field area should be kept in the good field area.

Each undulator module can have an acceptable initial trajectory range. The electrons entering the undulator module with the initial trajectory within the acceptable initial trajectory range can satisfy the resonance condition of equation (1), and interact with radiation in the other undulator module to stimulate the emission of coherent radiation. In contrast, electrons entering the undulator module with other trajectories may not stimulate significant emission of coherent radiation.

For example, generally, for a helical undulator module, the electron beam E should be substantially aligned with the center axis of the undulator module. The inclination or angle (in radians) between the electron beam E and the central axis of the undulator module should generally not exceed ρ /10 , where ρ is the FEL Pierce parameter. Otherwise, the conversion efficiency of the undulator module (that is, the part of the energy of the electron beam E converted into radiation in that module) can be reduced below the required amount (or can be reduced to almost zero). In one embodiment, the FEL Pierce parameter of the EUV spiral undulator module can be about 0.001, which indicates that the inclination angle of the electron beam E with respect to the central axis of the undulator module should be less than 100 microradians.

For the plane undulator module, a larger initial trajectory range may be acceptable. If the electron beam E keeps the magnetic field substantially perpendicular to the plane undulator module and stays within the good field area of the plane undulator module, then the coherent emission of radiation can be stimulated.

As the electrons of the electron beam E move through the drift space between each undulator module, the electrons do not follow a periodic path. Therefore, in this drift space, although the electrons spatially overlap with the radiation, they do not exchange any significant energy with the radiation, and therefore are actually decoupled from the radiation. The focused electron beam E has a finite emissivity and therefore will increase in diameter unless it is refocused. Therefore, the undulator 24 may further include a mechanism for refocusing the electron beam E between one or more pairs of adjacent undulator modules. For example, a quadrupole magnet can be provided between each pair of adjacent modules. The quadrupole magnet reduces the size of the electron bunch. This improves the coupling between the electrons and the radiation in the next undulator module, thereby increasing the stimulation of radiation emission.

The undulator 24 may further include an electron beam between each adjacent pair of undulator modules The steering unit is configured to provide fine adjustment of the electron beam E as the electron beam E passes through the undulator 24. For example, each beam steering unit can be configured to ensure that the electron beam remains within the good field area and enters the other undulator mode with a trajectory from the acceptable initial trajectory range for the next undulator module. group.

After leaving the undulator 24, the electron beam E is absorbed by the stopper 100. The stopper 100 may contain a sufficient amount of material to absorb the electron beam E. The material can have a threshold energy for inducing radioactivity. The electrons entering the cut-off device 100 with an energy lower than the threshold energy can only generate gamma-ray showers, but will not induce any significant level of radioactivity. The material can have a high threshold energy for inducing radioactivity by electron impact. For example, the beam stop may include aluminum (Al), which has a threshold energy of about 17 MeV. It may be necessary to reduce the energy of the electrons in the electron beam E before they enter the stopper 100. This removal or at least reduces the need to remove and dispose of radioactive waste from the cut-off device 100. This is advantageous because the removal of radioactive waste requires periodic shutdown of the free electron laser FEL, and the disposal of radioactive waste can be expensive and can have serious environmental impacts.

The energy of the electrons in the electron beam E can be reduced before they enter the stopper 100 by guiding the electron beam E through the speed reducer 26 disposed between the undulator 24 and the beam stopper 100.

In one embodiment, the electron beam E emitted from the undulator 24 can be decelerated by passing the electrons back through the linear accelerator 22, wherein the phase difference with respect to the electron beam generated by the injector 21 is 180 degrees. Therefore, the RF field in the linear accelerator is used to decelerate the electrons output from the undulator 24 and accelerate the electrons output from the injector 21. As the electrons decelerate in the linear accelerator 22, some of their energy is transferred to the RF field in the linear accelerator 22. The energy from the decelerating electrons is thus recovered by the linear accelerator 22 and can be used to accelerate the electron beam E output from the injector 21. This configuration is called an energy recovering linear accelerator (ERL).

4 and 5 illustrate the undulator module 200 according to an embodiment of the present invention (which may Two different cross-sectional views of parts forming part) of the undulator 24. The undulator module 200 includes a tube 40 for the electron beam E, a supporting structure 50, and four periodic magnetic structures 42a to 42d (FIG. 5). The periodic structures 42 a to 42 d are supported by the supporting structure 50, are arranged around the central axis 41 of the undulator module 200 and extend parallel to the central axis 41 of the undulator module 200. The four periodic magnetic structures 42a to 42d are operable together to generate a periodic magnetic field for guiding the electron beam along a periodic path, so that the electrons in the electron beam interact with the radiation in the undulator module 200 To stimulate the emission of coherent radiation to provide a radiation beam.

The undulator module 200 is a long and narrow structure extending along the axis 41 and passing through the center of the tube 40. The central axis 41 may form a reference axis for the cylindrical coordinate system of the undulator module 200. Therefore, the points in the undulator module 200 can be specified by the axial position, the radial position and the azimuth position. The axial position of a point can be the (signed) vertical distance between that point and the selected reference plane perpendicular to the central axis. The radial position of a point can be the vertical distance between that point and the central axis. The azimuth position of a point can be the angle between the plane passing through the central axis and the other point and the plane passing through the central axis and the reference line.

The tube 40 is configured so that in use, the electron beam E enters one end of the tube 40, passes through the end substantially along the central axis 41 of the undulator module 200, and exits the opposite end of the tube 40. In use, the tube 40 is kept under vacuum. Therefore, the tube 40 may be formed of a material that does not suffer from outgassing. For example, the tube 40 may be formed of stainless steel. Alternatively, the tube 40 may be formed of aluminum alloy. For the embodiment in which the tube 40 is formed of aluminum alloy, the tube 40 can be manufactured by extrusion. The cross section of the tube 40 in a plane perpendicular to the axis 41 of the undulator 24 may be substantially circular. The two cooling channels 62 and 64 extend parallel to the pipe 40 and are connected to the pipe 40 by radially extending connectors 62 a and 64 a. The connectors 62a, 64a form a thermal link between the cooling channels 62, 64 and the pipe 40. In use, a coolant flow is provided through the cooling channels 62, 64, which is used to cool the tube 40 via the connectors 62a, 64a.

The inside of the tube 40 provides a suitable environment for the electron beam E to propagate through. In detail, the tube 40 is kept under vacuum. In an alternative embodiment, the undulator module 200 does not include the tube 40, but the electron beam propagates through the channel defined by the magnetic structures 42a to 42d. In this embodiment, the entire undulator module 200 can maintain a suitable environment (for example, a vacuum) for the electron beam E to propagate through.

The pipe 40 can extend through a plurality of undulator modules. Alternatively, each undulator module may be provided with a corresponding tube, and two adjacent tubes of the undulator module may be connected in any suitable manner.

The structures of all periodic magnetic structures 42a to 42d are substantially similar. In detail, each of the periodic magnetic structures 42a to 42d has substantially the same period, that is, the (axial) distance the magnetic field of the periodic magnetic structures 42a to 42d repeats thereafter. The undulator period λ _{u of the} undulator module 200 (that is, the axial distance that the magnetic field of the undulator module 200 repeats thereafter) is equal to the period of each of the periodic magnetic structures 42a to 42d. Each of the periodic structures 42a to 42d is separated from the axis 41 in a direction substantially perpendicular to the axis 41 of the undulator 24 (which may be referred to as a radial direction).

Each of the periodic structures 42 a to 42 d includes a plurality of magnets 44, a plurality of ferromagnetic elements 48 and a plurality of spacer elements 46. In an alternative embodiment, each of the periodic structures 42a to 42d may be substantially in the form of a Halbach array. That is, each periodic structure may include a linear array of permanent dipole magnets configured so that the magnetic field of the permanent dipole magnets constructively interfere on one side of the periodic array and break on the opposite side of the array Sexually interfere.

Each of the plurality of magnets 44 is operable to generate a magnetic field. Each of the plurality of magnets 44 is a dipole magnet and has a substantially constant polarization direction. The polarization of each of the plurality of magnets 44 is substantially in the positive axial direction or the negative axial direction. In FIG. 4, the north pole N and the south pole S of each of the magnets 44 are shown. It will be understood that, by convention, the polarization direction of each magnet 44 can be the one extending from the south pole S of the magnet 44 to the north pole N of the magnet 44 direction. It can be seen from FIG. 4 that the plurality of magnets 44 of a given periodic structure are configured such that the polarization of the magnet 44 alternates between the positive axial direction and the negative axial direction along the length of the periodic magnetic structure 42a to 42d.

Each of the plurality of magnets 44 is formed of a relatively hard ferromagnetic material that is relatively difficult to demagnetize. Hard ferromagnetic materials are ferromagnetic materials with relatively large remanence and relatively wide hysteresis curve. For example, the magnet 44 may be a rare earth magnet, which is a relatively strong permanent magnet. The magnets may be samarium-cobalt (SmCo) magnets formed from an alloy of samarium and cobalt. These magnets include SmCo 1:5 series (SmCo ₅ ) and SmCo 2:17 series (Sm ₂ Co ₁₇ ). Alternatively, the magnet 44 may be a neodymium magnet (FeNdB) formed of iron, neodymium, and boron.

The plurality of ferromagnetic elements 48 are configured to guide the magnetic field generated by the plurality of magnets 44 toward the central axis 41 of the undulator module 200. In detail, the ferromagnetic elements 48 and the magnets 44 are alternately arranged in the axial direction. Each of the plurality of ferromagnetic elements 48 is formed of a relatively soft ferromagnetic material. Soft ferromagnetic materials are easily magnetized and demagnetized due to relatively small remanence, narrow hysteresis loop (ie, low coercive magnetic field strength), high permeability, and high magnetic saturation induction. Each of the plurality of ferromagnetic elements 48 may be formed of a soft ferromagnetic material having a coercive magnetic field strength of less than 500 A/m and a maximum relative permeability greater than 1000. In some embodiments, the ferromagnetic element 48 is formed of soft iron or iron-cobalt.

Each of the periodic magnetic structures 42a to 42d generates a periodic magnetic field, where the period λ _u is the length of the two magnets 44 and the two ferromagnetic elements 48.

Each of the plurality of magnets 44 is separated from the pipe 40 by a spacer element 46. That is, the spacer element 46 is provided radially inside the magnet 44. Each spacer element 46 has substantially the same axial extent as its corresponding magnet 44. In terms of cross section (in a plane perpendicular to the central axis 41), the spacer element 46 may have any suitable shape. The spacer 46 may be formed of a non-magnetic material.

Each ferromagnetic element 48 separates an adjacent pair of magnets 44 and extends farther toward the tube 40 than each of the magnets 44.

Although the tube 40 is maintained in a high vacuum, high-energy electrons from the electron beam E can be scattered by residual gas molecules in the tube 40, for example, by Rutherford scattering. These scattered electrons can be incident on the periodic magnetic structures 42a to 42d of the undulator module 200 to generate electromagnetic showers or cascades of lower energy electrons and photons, which can cause the magnet 44 to be partially demagnetized. As time goes by, this demagnetization of the magnet 44 causes deformation of the trajectory followed by the electrons passing through the undulator module 200, thereby causing a loss in the conversion efficiency of the free electron laser. Therefore, it is necessary to periodically monitor the magnetic field strength along the central axis 41 of the undulator module 200. Once the conversion efficiency of the free electron laser drops below an acceptable level, the periodic magnetic structures 42a to 42d can be retuned (for example, by remagnetizing the magnet 44).

The use of the ferromagnetic element 48 allows the magnet 44 to be positioned away from the tube 40 without significant loss of magnetic field strength at the central axis 41. This is because the ferromagnetic element 48 is magnetized by the magnet 44 and guides the magnetic field applied by the magnet 44 toward轴41. In fact, the geometry of the undulator module 200 can be selected so that the ferromagnetic element 48 provides sufficient focus to provide the magnetic field along the axis 41 with an amplitude B greater than that in a conventional oscillator with a magnet of the same strength ₀ . This spatial separation of the permanent magnet 44 and the pipe 40 allows a spacer element 46 to be placed between the magnet 44 and the pipe 40. The spacer element 46 may be formed of a material that will absorb a large fraction of high-energy electrons and photons originating from the beam tube 40. In this way, the permanent magnet 44 can be shielded from this electromagnetic radiation, and the life of the undulator module 200 can be prolonged. The sensitivity of the magnetization of the ferromagnetic element 48 to radiation damage is significantly lower than the sensitivity of the magnetization of the magnet 44 to radiation damage. For example, for an embodiment in which the ferromagnetic element 48 is formed of soft iron-cobalt, the magnetization of the ferromagnetic element 48 is at least 100 times less sensitive to radiation damage than the magnetization of the magnet 44 to radiation damage. Therefore, the magnetization of the ferromagnetic element 48 is not significantly affected by high-energy electrons or photons.

The electromagnetic shower caused by high-energy electrons entering the spacer element 46 will generate a significant number of photons. This in turn increases the number of photonuclear reactions within the spacer element 46, which can cause the emission of neutrons from the nucleus. Therefore, in the embodiment of the present invention, the magnet 44 is preferably It is impossible to be formed from magnetic materials that are demagnetized by high energy neutrons. For this reason, samarium-cobalt (SmCo) magnets may be better than neodymium magnets (FeNdB) because the demagnetization effect of neutrons is five orders of magnitude smaller for SmCo magnets than for FeNdB magnets.

In some embodiments, the undulator module 200 may be provided with a neutron absorbing material on, for example, an outer radial surface. This can protect the magnet from, for example, neutrons generated by other parts of the free electron laser.

The spacer element 46 may be provided with a cooling channel (not shown in the figure) through which the coolant can circulate. In some embodiments of the present invention, a small gap (not shown in the figure) may be provided between the spacer element 46 and the tube 40 on one side and between the magnet 44 and the ferromagnetic element 48 on the other side. Advantageously, this gap can at least partially thermally insulate the magnet 44 from the spacer element 46 and the pipe 40 (protection against conduction). This can help stabilize the temperature of the magnet 44 and stabilize the magnetic field generated along the central axis 41. The gap can be kept under vacuum, which can improve the level of thermal insulation. This can be achieved, for example, by placing the entire undulator module 200 in a chamber that can be kept at a low pressure. In addition, a low emissivity film can be used to coat one or more surfaces of the spacer element 46, the tube 40, the magnet 44, and the ferromagnetic element 48 that define the gap. The low emissivity film may include, for example, gold. Advantageously, this low emissivity film can at least partially thermally insulate the magnet 44 from the spacer element 46 and the tube 40 (protection against infrared radiation). This can provide further stability to the temperature of the magnet 44 and in turn provide further stability to the magnetic field generated along the central axis 41.

Each of the periodic magnetic structures 42a to 42d extends axially across the tube 40 (that is, parallel to the central axis 41). In a plane perpendicular to the axis 41 of the undulator module 200, four periodic magnetic structures are substantially evenly distributed around the tube 40. The first pair of magnetic structures 42 a and 42 b are symmetrically arranged on the opposite sides of the tube 40. Each magnet 44 of the periodic magnetic structure 42a is opposed to one of the magnets 44 of the periodic magnetic structure 42b, and each ferromagnetic element 48 of the periodic magnetic structure 42a and the ferromagnetic element 48 of the periodic magnetic structure 42b One of them is opposite. The polarization direction of each magnet 44 of the periodic magnetic structure 42a is in a direction opposite to the polarization direction of the opposing magnet 44 of the periodic magnetic structure 42b. That is, the first pair of magnetic structures 42a, 42b are configured to be out of phase by half the period λ _u of the undulator.

The second pair of magnetic structures 42c, 42d are configured to be out of phase up to half of the undulator period λ _u , and are symmetrically configured on the opposite sides of the tube 40. The second pair of magnetic structures 42c, 42d is rotated by 90° around the central axis 41 relative to the first pair 42a, 42b. The first pair 42a, 42b may be axially displaced relative to the second pair 42c, 42d, so that the first pair 42a, 42b is out of phase with the second pair 42c, 42d. The amount of shift can determine the polarization of the radiation generated by the undulator module 200. For example, in FIG. 4 and FIG. 5 shows the embodiment, the first pair 42a, 42b relative to the second pair 42c, 42d axially displaced a quarter wave oscillator the period λ _u. That is, the magnet 44 of the first pair of periodic magnetic structures 42a, 42b and the ferromagnetic element 48 of the second pair of magnetic structures 42c, 42d are arranged at substantially the same axial position. That is, in the case of azimuthal movement around the central axis 41 of the undulator module 200, each periodic magnetic structure (that is, in a sequence 42a, 42d, 42b, 42c) relative to the previous periodic magnetic structure axis Shift to the ground by the same amount of +λ _u /4 or -λ _u /4. This configuration can generate circularly polarized radiation as the electron beam E propagates through this configuration, and can be referred to as a helical undulator module 200. The polarization state of circularly polarized radiation depends on whether each periodic magnetic structure (in the sequence 42a, 42d, 42b, 42c) is axially displaced with respect to the previous periodic magnetic structure by +λ _u /4 or -λ _u / 4.

In an alternative embodiment, in the case of an azimuthal movement around the central axis 41 of the undulator module 200, the difference between each magnetic structure and the previous periodic magnetic structure (in the sequence 42a, 42d, 42b, 42c) The axial displacement alternates between +λ _u /4 and -λ _u /4. This configuration can generate linearly polarized radiation as the electron beam E propagates through this configuration, and can be referred to as a plane undulator module 200. Other axial displacements between the four periodic magnetic structures 42a, 42b, 42c, 42d can produce elliptically polarized radiation.

In an alternative embodiment, the undulator module 200 may only include the first pair of magnetic structures 42a, 42b, that is, the second pair of magnetic structures 42c, 42d may not exist. This configuration can generate linearly polarized radiation as the electron beam E propagates through this configuration, and can be called a plane wave Dang device module 200.

Some embodiments of the present invention are related to devices and methods for determining the magnetic field strength of the undulator module.

One embodiment relates to a device including an undulator module 200 and a magnetic field sensor. The undulator module 200 and the magnetic field sensor are configured to be releasably engaged with each other, so that the magnetic field strength of the undulator module 200 can be measured.

The device may include a plurality of magnetic field sensors. Fig. 6A, Fig. 6B and Fig. 7 show three different magnetic field sensors 300, 310, 320, respectively. Each of the magnetic field sensors 300, 310, 320 includes: a body 302, 312, 322; and a sensing element 304, 314, 324 operable to measure a magnetic field. For example, the sensing elements 304, 314, and 324 may each include a Hall probe.

The undulator module 200 has a plurality of openings 210, 220, and 230 for receiving the sensing elements 304, 314, and 324 of the magnetic field sensors 300, 310, and 320. Each of the openings 210, 220, 230 includes a hole in the support structure 50 of the undulator module 200. Each of the openings 210, 220, 230 extends along the opening axis 211, 221, 231.

The body 302, 312, 322 of each of the magnetic field sensors 300, 310, 320 includes: engaging portions 302a, 312a, 322a, which are configured to engage with the undulator module 200; and protruding portions 302b, 312b , 322b, which extends away from the engaging portions 302a, 312a, 322a and is attached to the sensing element. The surfaces of the engaging portions 302a, 312a, and 322a are provided with protrusions 306, 316, and 326.

The surface of the support structure 50 of the undulator module 200 is provided with recesses 52, 53, 54 near each of the openings 210, 220, and 230. The recesses 52, 53, 54 are complementary to the protrusions 306, 316, and 326, and allow the body 302, 312, 322 of each of the magnetic field sensors 300, 310, and 320 to be supported by the undulator module 200 The structure 50 is releasably engaged.

In detail, the recesses 52, 53, 54 and the protrusions 306, 316, 326 are complementary alignment features that provide between each magnetic field sensor 300, 310, 320 and the undulator module 200 The engagement can be released so that the sensing elements 304, 314, and 324 of the magnetic field sensors 310, 320, and 330 can be repeatedly positioned in the undulator module 200 in substantially the same position relative to the central axis 41. These alignment features can be configured to allow the sensing element 304, 314, 324 of each magnetic field sensor 300, 310, 320 to be positioned in one of the openings 210, 220, 230, from the openings 210, 220, 230 is removed, and then repositioned in the openings 210, 220, 230 in substantially the same fixed position relative to the undulator module 200. For example, the alignment features can be configured to allow the sensing elements 304, 314, 324 of each magnetic field sensor 300, 310, 320 to be within a specified tolerance distance of the undulator module 200 in a fixed position. It is repeatedly positioned in one of the openings 210, 220, 230. In some embodiments, the specified tolerance distance may be 10 microns or less, for example, 2 microns or less.

The device allows the sensing elements 304, 314, and 324 of each magnetic field sensor 310, 320, and 330 to move between the following two: (a) The accurate position in the undulator module 200, which is oscillating Near the central axis 41 of the device module 200, so that the strength and/or direction of the magnetic field at that location can be determined; and (b) a location outside the undulator module 200, where the sensing element is not subject to significant levels Radiation or radioactivity. It will be understood that the position within the undulator module 200 near the central axis 41 of the undulator module 200 may be sufficiently close to the central axis 41 to allow the measurement of the magnetic field from that position to the central axis 41 Any position on the magnetic field (intensity and/or direction) for useful judgment. The sensing elements 304, 314, and 324 of the magnetic field sensors 300, 310, and 320 can, for example, be periodically and accurately positioned near the central axis 41 of the undulator module 200, while no electron beam E passes through The undulator module 200. In addition, it can be positioned near the central axis 41 of the undulator module 200 for a relatively short period of time, for example, only long enough to take a measurement. This allows periodic measurement of the magnetic field near the central axis 41 of the undulator module 200 while limiting the level of radioactivity experienced by the sensing elements 304, 314, and 324. Allowing the openings 210, 220, 230 defined by the free undulator module 200 to remove the magnetic field sensors 300, 310, 320 will allow them to be recalibrated between measurements. It also limits the damage to the magnetic field sensors 300, 310, 320 due to radiation. The amount of bad.

One or more measurements of the magnetic field intensity near the central axis 41 of the self-undulator module 200 can be used to determine the magnetic field intensity on the central axis 41 by, for example, modeling or extrapolation. In order to accurately determine the magnetic field strength at the central axis 41 of the undulator module 200, it is important to locate the magnetic sensors 300, 310 in substantially the same position relative to the undulator module 200 for each measurement. , 320 sensing elements 304, 314, 324. This is achieved by the alignment features (ie, recesses 52, 53, 54 and protrusions 306, 316, 326).

This device allows to sample the magnetic field in the undulator module 200 without disassembling the undulator module 200. This is because the openings 210, 220, 230 allow the sensing elements 204 of the magnetic field sensors 200, 210, 220 , 214, 224 are positioned in the undulator 200. This can be advantageous because the disassembly of the undulator module 200 can be time consuming. In addition, the components of the undulator module 200 closer to the central axis 41 may be radioactive for a period of time after the electron beam E has been turned off. Because the disassembly of the undulator module 200 can expose these components of the undulator module 200, it must contain generated radiation, or the undulator module 200 should be allowed to cool for a period of time before disassembly. This increases the disassembly complexity of the undulator module 200 and/or increases the downtime of the free electron laser FEL.

Providing a plurality of openings 210, 220, 230 allows the magnetic field to be sampled in a plurality of different positions within the undulator module 200. Measuring the magnetic field at a larger number of different positions in the undulator module 200 can increase the accuracy with which the magnetic field on the central axis 41 can be determined.

Releasable between the magnetic field sensor 300, 310, 320 and the undulator module 200 provided by complementary alignment features (ie, recesses 52, 53, 54 and protrusions 306, 316, 326) The engagement allows the sensing elements 304, 314, and 324 to be reproducibly positioned in the undulator module 200 in substantially the same orientation.

This may be advantageous when, for example, the sensing elements 304, 314, 324 are operable to determine the component of the magnetic field in a single sensing direction (relative to the magnetic field sensor 300, 310, 320). For example, for the sensing elements 304, 314, 324 including Hall probes example. In the case of these embodiments, in order to accurately determine the magnetic field strength at the central axis 41 of the undulator module 200, it is important to position the magnetic sensor in substantially the same orientation for each measurement of the magnetic field. The sensing elements 304, 314, and 324 of the sensors 300, 310, and 320 (so that the sensing elements 304, 314, and 324 determine the same component of the magnetic field for each measurement).

The alignment features (ie, recesses 52, 53, 54 and protrusions 306, 316, 326) may be configured to allow the sensing elements 304, 314, 324 of the magnetic field sensors 300, 310, 320 to be oriented The designated volume is positioned inwardly in the openings 210, 220, and 230. The specified tolerance direction can be 1 milliradian or less, for example, 0.1 milliradian.

The complementary alignment features (ie, the recesses 52, 53, 54 and the protrusions 306, 316, 326) can be configured such that when each magnetic field sensor 300, 310, 320 is engaged with the undulator module 200 At this time, the sensing elements 304, 314, and 324 of the magnetic field sensors 300, 310, and 320 are in one of a limited number of fixed orientations. The alignment features can provide any number of fixed orientations. For example, in some embodiments, the alignment feature may provide a single fixed orientation. This can prevent, for example, the magnetic sensors 300, 310, 320 and the undulator module 200 having the sensing elements 304, 314, 324 from engaging in two different orientations for two different measurements, and thus ensure that the The measurement is consistent. Alternatively, complementary alignment features may provide two or more fixed orientations. That is, the complementary alignment features can provide a plurality of discrete fixed orientations for the magnetic sensors 300, 310, 320. This may allow the magnetic field sensors 300, 310, 320 and the undulator module 200 with the sensing elements 204, 214, 224 to be engaged in one of two or more different orientations, so that, for example, Allows to determine two or more components of the magnetic field.

The complementary alignment features (ie, the recesses 52, 53, 54 and the protrusions 306, 316, 326) can be configured such that when each magnetic field sensor 300, 310, 320 is engaged with the undulator module 200 At this time, each magnetic field sensor 300, 310, 320 is in contact with the undulator module 200 at three or more contact points. That is, each magnetic field sensor 300, 310, 320 may have three or more protrusions 306, 316, 326, and the undulator module 200 may have three One or more recesses 52, 53, 54. This can improve the accuracy with which the position and orientation of the sensing elements 304, 314, and 324 can be controlled.

The openings 210, 220, and 230 can be positioned at a series of different (axial and azimuth) positions in the undulator module 200.

In some embodiments, at least one of the openings 220 (FIGS. 5 and 7) is provided in the support structure 50 at an azimuth position between the azimuth positions of two of the periodic magnetic structures 42a to 42d It extends radially. This allows the sensing element 324 of the magnetic field sensor 320 to extend through the opening 220 and between the two adjacent periodic magnetic structures 42a to 42d. Advantageously, this allows the sensing element 324 to be positioned near the central axis 41 of the undulator module 200 (eg, adjacent to the tube 40).

In some embodiments, at least one of the openings 230 and one of the periodic magnetic structures 42a to 42d are at substantially the same azimuth position and one of the magnets 44 of the periodic magnetic structures 42a to 42d Extend radially at substantially the same axial position. This allows the sensing element of the magnetic field sensor to be placed adjacent to one of the magnets 44 of one of the periodic magnetic structures 42a to 42d, where the magnetic field is dominated by the magnetic field of the other magnet 44. Therefore, this allows the magnetic field of the individual magnet 44 to be monitored.

In some embodiments, at least one of the openings 210 and one of the periodic magnetic structures 42a to 42d are at substantially the same azimuth position and are at the same azimuth position as that of the ferromagnetic element 48 of the periodic magnetic structures 42a to 42d. One extends radially at substantially the same axial position. At this position radially above one of the ferromagnetic elements 48, the magnetic field is substantially aligned with the radial direction (ie, the protrusions 302b, 312b, 322b of the body of the magnetic field sensor). This may be advantageous because it is easier to attach a sensing element (such as a Hall probe) to the protruding portions 302b, 312b, 322b of the body of the magnetic field sensor, so that the pair of sensing elements protrudes along The parts 302b, 312b, and 322b are sensitive to magnetic fields.

In some embodiments, at least one of the openings may include a bore 48a in one of the ferromagnetic elements 48 extending into one of the periodic magnetic structures 42a to 42d. For example, as shown in FIG. 6B, the opening 210 may extend through the support structure and into one of the ferromagnetic elements 48. That is, the opening 210 may be substantially at the same azimuth position as one of the periodic magnetic structures 42a to 42d and substantially on the same axis as one of the ferromagnetic elements 48 of the periodic magnetic structures 42a to 42d. Extend radially to the position. Due to the relatively high magnetic permeability of the ferromagnetic element 48, the magnetic field is stronger inside the ferromagnetic element 48. Therefore, by measuring the magnetic field inside the ferromagnetic element 48, the accuracy of the measurement can be increased (using the same sensing element).

The device according to the present invention may include an undulator module 200 with at least one opening. For embodiments including a plurality of different openings, a different magnetic field sensor can be used for each of the plurality of openings. Alternatively, a single magnetic field sensor may be used for more than one of the plurality of openings. For example, a single magnetic field sensor can be used for all of the plurality of openings. Alternatively, the plurality of openings may comprise a plurality of groups of openings (for example, of different types, that is, located radially above the magnet 44, within the ferromagnetic element 48, or azimuthally between the two periodic magnetic structures 42a to 42d ), and a different single magnetic field sensor can be used for each different set of openings. Each different set of openings may have different alignment features (ie, recesses 52, 53, 54).

Another embodiment of the present invention that allows the measurement of the magnetic field strength of the undulator module 200 relates to an undulator module 200 in which one of the ferromagnetic elements 48 of at least one of the periodic magnetic structures 42a to 42d At least one of them has a device for determining the magnetic permeability of the ferromagnetic element 48.

The magnetic permeability of the ferromagnetic element 48 depends on the magnetic field applied by the plurality of magnets 44. Therefore, the device for determining the permeability of the ferromagnetic element 48 of this embodiment of the present invention provides an indirect measurement of the magnetic field provided by the magnet 44. From one or more measurements of the magnetic permeability of the ferromagnetic element 48, the magnetic field strength on the central axis 41 of the undulator module 200 can be determined, for example, by modeling or extrapolation.

Now referring to FIGS. 8A and 8B, the method for determining one of the ferromagnetic elements 48 will be described. Permeability device. The device for determining the magnetic permeability of the ferromagnetic element 48 includes: a coil set, which includes one or more coils 400 of wires wound around the ferromagnetic element 48; a power supply (not shown in the figure), which can Operates to apply alternating current to the coil 400 of the coil set; and a device (not shown in the figure), which is configured to determine the inductance of the coil 400 of the coil set.

When the power supply applies alternating current to the coil 400 of the coil assembly, an alternating magnetic field is generated in the ferromagnetic element 48. This in turn will induce a voltage in any coil 400 wound around the ferromagnetic element 48. The inductance and induced voltage depend on the magnetic permeability of the ferromagnetic element 48. Therefore, by determining the inductance of the coil 400 from the coil group, the permeability of the ferromagnetic element 48 can be determined.

In this embodiment, the coil 400 of the coil group whose inductance is determined is the same coil 400 as the coil to which the AC power is applied by the power supply. Alternatively, in another embodiment, two coils may be provided. For these embodiments, the AC power can be applied to the first coil by the power supply, and the inductance of the second coil can be determined.

Optionally, grooves 410 may be provided on the outer surface of the ferromagnetic element 48, and one or more coils 400 of the coil group may be accommodated in the grooves 410. This can facilitate easy installation and alignment of the coil 400 and the ferromagnetic element 48.

Any of the embodiments of the invention described above may be provided in combination or separately.

For example, some embodiments of the present invention may include one or more openings and one or more magnetic field sensors in the undulator module. The undulator module and the magnetic field sensor are included in the magnetic field sensor. Complementary alignment features for releasable engagement with the undulator module are provided. These embodiments may or may not further include a device for determining the permeability of at least one of the ferromagnetic elements of at least one of the periodic magnetic structures.

In addition, some embodiments of the present invention may include a device for determining the permeability of at least one of the ferromagnetic elements in at least one of the periodic magnetic structures of the undulator module. Set. These embodiments may or may not further include one or more openings and one or more magnetic field sensors in the undulator module. The undulator module and the magnetic field sensor are included in the magnetic field sensor and the undulator Complementary alignment features for releasable engagement are provided between the device modules.

The embodiments of the present invention have been described in which the undulator module and the magnetic field sensor include complementary alignment features that provide releasable engagement between the magnetic field sensor and the undulator module. It will be understood that in the context of this content, releasable engagement means that the magnetic field sensor and the undulator module can be engaged and disengaged. It does not mean that the magnetic field sensor and the undulator module have a locking mechanism to prevent or limit disengagement. In some embodiments, the magnetic field sensor and the undulator module may have this locking mechanism. In contrast, in some embodiments, the magnetic field sensor can be manually held to engage with the undulator module.

The embodiment of the present invention has been described in which the surface of the magnetic field sensor is provided with protrusions and the surface of the undulator module is provided with recesses, the recesses and protrusions are complementary and allow the magnetic field sensor and the undulator module Releasably engage. It will be appreciated that in alternative embodiments, the undulator module and the magnetic field sensor include different complementary alignment features that provide releasable engagement between the magnetic field sensor and the undulator module. For example, the surface of the magnetic field sensor may be provided with recesses and the surface of the undulator module may be provided with protrusions. Alternatively, the surface of the magnetic field sensor may be provided with a combination of protrusions and recesses, and the surface of the undulator module may be provided with complementary recesses and protrusions.

Although the embodiment of the radiation source SO has been described and depicted as including a free electron laser FEL, it should be understood that the radiation source may include any number of free electron laser FELs. For example, the radiation source may include more than one free electron laser FEL. For example, two free electron lasers can be configured to provide EUV radiation to a plurality of lithography devices. This is to allow some redundancy. This will allow a free electron laser to be used when another free electron laser is being repaired or undergoing maintenance.

Although the described embodiment of the lithography system LS includes eight lithography devices LA _a to LA _n , the lithography system LS may include any number of lithography devices. For example, the number of lithography devices forming the lithography system LS may depend on the amount of radiation output from the radiation source SO and the amount of radiation lost in the beam delivery system BDS. Additionally or alternatively, the number of lithography devices forming the lithography system LS may depend on the layout of the lithography system LS and/or the layout of the plurality of lithography systems LS.

Embodiments of the lithography system LS may also include one or more mask inspection devices MIA and/or one or more aerial inspection measurement systems (AIMS). In some embodiments, the lithography system LS may include a plurality of photomask detection devices to allow some redundancy. This may allow one reticle inspection device to be used when another reticle inspection device is being repaired or undergoing maintenance. Therefore, a photomask detection device is always available. The mask detection device can use a lower power radiation beam than the lithography device. In addition, it will be understood that the radiation generated using the free electron laser FEL of the type described herein can be used for applications other than lithography or lithography related applications.

It will be further understood that a free electron laser containing the undulator as described above can be used as a radiation source for several purposes, including but not limited to lithography.

The term "relativistic electron" should be interpreted as meaning electrons with relativistic energy. An electron can be considered to have relativistic energy when its kinetic energy is equal to or greater than its rest mass energy (511 keV, in natural units). In practice, the particle accelerator that forms the part of a free electron laser can accelerate electrons to an energy much greater than the energy of its rest mass. For example, a particle accelerator can accelerate electrons to energy >10MeV, >100MeV, >1GeV or greater.

The embodiments of the present invention have been described in the context of the free electron laser FEL outputting EUV radiation beams. However, the free electron laser FEL can be configured to output radiation of any wavelength. Therefore, some embodiments of the present invention may include free electrons that output radiation beams other than EUV radiation beams.

The term "EUV radiation" can be considered to encompass electromagnetic radiation having a wavelength in the range of 4 nanometers to 20 nanometers (eg, in the range of 13 nanometers to 14 nanometers). EUV radiation can Have a wavelength less than 10 nanometers, for example, in the range of 4 nanometers to 10 nanometers, such as 6.7 nanometers or 6.8 nanometers.

The lithography devices LA _a to LA _n can be used in IC manufacturing. Alternatively, the lithography devices LA _a to LA _n described herein may have other applications. Other possible applications include manufacturing integrated optical systems, guiding and detecting patterns for magnetic domain memory, flat panel displays, liquid-crystal displays (LCD), thin-film magnetic heads, and so on.

Different embodiments can be combined with each other. The features of the embodiment can be combined with the features of other embodiments.

Although specific embodiments of the present invention have been described above, it will be understood that the present invention may be practiced in other ways than those described. The above description is intended to be illustrative and not restrictive. Therefore, it will be obvious to those who are familiar with the art that the described invention can be modified without departing from the scope of the patent application set forth below. Other aspects of the present invention are illustrated in the numbered items below.

1. A device comprising a undulator module and a magnetic field sensor, the magnetic field sensor comprising: a body; and a sensing element operable to measure a magnetic field; the undulator module It includes: a support structure; and a plurality of periodic magnetic structures, the periodic structures are supported by the support structure, are arranged around a central axis and extend parallel to the central axis; wherein the undulator module has At least one opening for accommodating the sensing element of the magnetic field sensor; wherein the undulator module and the magnetic field sensor include complementary alignment features, which are positioned between the magnetic field sensor and the undulator module A releasable engagement is provided between the groups, so that the sensing element of the magnetic field sensor can be repeatedly positioned in substantially the same position relative to the central axis In the undulator module.

2. The device of clause 1, wherein the complementary alignment features include one or more protrusions on one of the magnetic field sensor and the undulator module, and the magnetic field sensor and the One or more complementary recesses on the other of the undulator modules.

3. The device of clause 1 or clause 2, wherein the releasable meshing system between the magnetic field sensor and the undulator module provided by the complementary alignment features makes the magnetic field sensor The sensing element can be positioned in the undulator module repeatedly in substantially the same orientation.

4. The device of any one of the preceding clauses, wherein the complementary alignment features are configured such that when the magnetic field sensor is engaged with the undulator module, the sensing element of the magnetic field sensor On one of a limited number of fixed orientations.

5. The device according to any one of the preceding items, wherein the undulator module is provided with a plurality of openings for receiving the sensing element of a magnetic field sensor.

6. The device according to any one of the preceding items, which comprises a plurality of magnetic field sensors.

7. The device according to any one of the preceding clauses, wherein at least one of the openings for receiving the sensing element of a magnetic field sensor is provided in the supporting structure, and the periodic magnetic The azimuth position between the two azimuth positions in the structure extends radially.

8. The device of any one of the preceding clauses, wherein each of the periodic magnetic structures includes a plurality of magnets, and each of the plurality of magnets is operable to generate a magnetic field, wherein At least one of the openings of the sensing element of a magnetic field sensor and one of the periodic magnetic structures are at substantially the same azimuth position and the magnets of the periodic magnetic structure One of them extends radially at a substantially same axial position.

9. The device of clause 8, wherein the plurality of magnets of a given periodic structure extend axially such that the polarization direction of the plurality of magnets is along one of the periodic magnetic structures The length forms a repeating pattern in an axial direction.

10. The device of clause 8 or clause 9, wherein each of the periodic magnetic structures further comprises a plurality of ferromagnetic elements configured to direct the magnetic field generated by the plurality of magnets toward the wave The central axis of the oscillator module.

11. The device of clause 10, wherein at least one of the openings for receiving the sensing element of a magnetic field sensor includes the ferromagnetic materials extending to one of the periodic magnetic structures A bore in one of the components.

12. The device according to any one of the preceding clauses, wherein the openings comprise a hole in the support structure of the undulator module.

13. The device according to any one of the preceding clauses, wherein the undulator module is a plane undulator module including one of two periodic magnetic structures.

14. The device according to any one of the preceding clauses, wherein the undulator module is a spiral undulator module including one of four periodic magnetic structures.

15. A magnetic field sensor, comprising: a body; and a sensing element operable to measure a magnetic field; wherein the magnetic field sensor includes an alignment feature, which is in the magnetic field sensor and a wave A releasable engagement is provided between the undulator modules, so that the sensing element of the magnetic field sensor can be repeatedly positioned in the undulator module in substantially the same position relative to the central axis.

16. A undulator module, comprising: a support structure; and a plurality of periodic magnetic structures, the periodic structures are supported by the support structure and arranged around a central axis and parallel to the central axis Extension; wherein the undulator module has at least one opening for receiving a sensing element of a magnetic field sensor; wherein the undulator module includes an alignment feature, which is in the magnetic field sensor and the wave A releasable engagement is provided between the undulator modules, so that the sensing element of the magnetic field sensor can be repeatedly positioned in the undulator module in substantially the same position relative to the central axis.

17. A undulator module comprising a plurality of periodic magnetic structures, the periodic structures are arranged around a central axis and extend parallel to the central axis, and are operable to generate a period The sexual magnetic field is used to guide an electron beam along a periodic path, so that the electrons in the electron beam interact with radiation in the undulator module to stimulate the emission of coherent radiation to provide a radiation beam; Wherein each of the periodic magnetic structures includes a plurality of magnets and a plurality of ferromagnetic elements, each of the plurality of magnets can be operated to generate a magnetic field, and each of the plurality of ferromagnetic elements Are configured to guide the magnetic field generated by the plurality of magnets toward the central axis; wherein at least one of the ferromagnetic elements of at least one of the periodic magnetic structures is provided with a ferromagnetic element for determining the other The permeability of a device.

18. The undulator module of clause 17, wherein the device for determining the permeability of the ferromagnetic element includes: a coil set including one or more wires wound around the ferromagnetic element A coil; a power supply operable to apply an alternating current to a coil of the coil set; and a device configured to determine an inductance of a coil of the coil set or a coil in the coil set A voltage induced in.

19. A free electron laser, comprising: an electron source for generating an electron beam including a plurality of relativistic electron beams; and a undulator configured to receive the electron beam along A periodic path guide The electron beam is guided so that the electron beam interacts with the radiation in the undulator, thereby stimulating the emission of radiation and providing a radiation beam, wherein the undulator includes any one of clauses 1 to 14 Device or undulator module such as any one of clauses 17 to 18.

20. A lithography system, comprising: a free electron laser as in Clause 19; and at least one lithography device, each of the at least one lithography device is configured to receive the free electron laser generated At least part of at least one radiation beam.

21. A method for determining the strength of a magnetic field of a undulator module, the method comprising: inserting a magnetic field sensor including a sensing element into an opening in the undulator module such that An alignment feature on the magnetic field sensor cooperates with a complementary alignment feature on the undulator module, so that the sensing element is accurately positioned on a quantity relative to a central axis of the undulator module Measuring position; using the sensing element to measure a magnetic field at the measuring position; and removing the magnetic field sensor from the opening in the undulator module.

22. The method of clause 21, comprising: inserting a magnetic field sensor including a sensing element into each of a plurality of openings in the undulator module, so that the magnetic field sensor The first alignment feature cooperates with a complementary alignment feature on the undulator module, so that the sensing element is accurately positioned in one of a plurality of measurement positions relative to a central axis of the undulator module One; use the sensing element to measure a magnetic field at the measurement position; and remove the magnetic field sensor from each of the plurality of openings in the undulator module.

23. The method of clause 21 or clause 22, further comprising: determining a magnetic field at a central axis of the undulator module from the measured magnetic field at the or each measurement position field.

24. A method for determining the intensity of a magnetic field of an undulator module including a plurality of periodic magnetic structures, the periodic structures being arranged around a central axis and extending parallel to the central axis, the periods Each of the magnetic structures includes a plurality of magnets alternately arranged with a plurality of ferromagnetic elements, and the method includes: determining at least one of the ferromagnetic elements of at least one of the periodic magnetic structures The permeability.

25. The method of clause 24, which includes: determining the permeability of the ferromagnetic elements of the periodic magnetic structures.

26. The method of clause 24 or clause 25, comprising: determining the undulator module from the measured permeability of the plurality of the ferromagnetic elements of the plurality of the periodic magnetic structures The magnetic field at one of the central axis.

40: beam fittings

42b: Periodic magnetic structure

42d: Periodic magnetic structure

44: Magnet

46: spacer element

48: Ferromagnetic element

50: Supporting structure

53: recessed part

62: cooling channel

62a: Connector

64: cooling channel

64a: connector

320: Magnetic field sensor/magnetic sensor

322: body

322a: meshing part

322b: Protruding part

324: sensing element

326: protruding part

Claims (15)

An undulator includes a undulator module and a magnetic field sensor. The magnetic field sensor includes: a body; and a sensing element operable to measure a magnetic field; the undulator The device module includes: a support structure; and a plurality of periodic magnetic structures, the periodic magnetic structures are supported by the support structure, are arranged around a central axis and extend parallel to the central axis; wherein the undulation The device module is provided with at least one opening for receiving the sensing element of the magnetic field sensor; wherein the undulator module and the magnetic field sensor include complementary alignment features, which are arranged between the magnetic field sensor and the magnetic field sensor. A releasable engagement is provided between the undulator modules, so that the sensing element of the magnetic field sensor can be repeatedly positioned in the undulator module at substantially the same position relative to the central axis. The undulator of claim 1, wherein the complementary alignment features include one or more protrusions on one of the magnetic field sensor and the undulator module, and the magnetic field sensor and the One or more complementary recesses on the other of the undulator modules. The undulator of claim 1 or 2, wherein the releasable engagement system between the magnetic field sensor and the undulator module provided by the complementary alignment features makes the magnetic field sensor The sensing element can be positioned in the undulator module repeatedly in substantially the same orientation. Such as the undulator of claim 1 or 2, wherein the complementary alignment features are configured such that when the magnetic field sensor is engaged with the undulator module, the sensor of the magnetic field sensor The measuring element is in one of a limited number of fixed orientations. Such as the undulator of claim 1 or 2, wherein the undulator module is provided with a plurality of openings for receiving the sensing element of a magnetic field sensor. A magnetic field sensor, comprising: a body; and a sensing element operable to measure a magnetic field; wherein the magnetic field sensor includes an alignment feature, which is connected between the magnetic field sensor and a undulator Releasable engagement is provided between the modules, so that the sensing element of the magnetic field sensor can be repeatedly positioned in the undulator module in substantially the same position relative to the central axis. A undulator module comprising: a support structure; and a plurality of periodic magnetic structures, the periodic magnetic structures are supported by the support structure, are arranged around a central axis and extend parallel to the central axis Wherein the undulator module has at least one opening for receiving a sensing element of a magnetic field sensor; wherein the undulator module includes an alignment feature, which is in the magnetic field sensor and the wave Releasable engagement is provided between the undulator modules, so that the sensing element of the magnetic field sensor can be repeatedly positioned in the undulator module at substantially the same position relative to the central axis. A free electron laser, comprising: an electron source for generating an electron beam including a plurality of relativistic electron beams; and an undulator such as any one of claims 1 to 5, the undulator The device is configured to receive the electron beam and guide the electron beam along a periodic path so that the electron The beam interacts with radiation in the undulator, stimulates the emission of radiation and provides a radiation beam. A lithography system, comprising: a free electron laser as in claim 8; and at least one lithography device, each of the at least one lithography device is configured to receive at least one generated by the free electron laser At least part of a beam of radiation. A method for determining the strength of a magnetic field of a undulator module, the method comprising: inserting a magnetic field sensor including a sensing element into an opening in the undulator module so that the magnetic field An alignment feature on the sensor cooperates with a complementary alignment feature on the undulator module so that the sensing element is accurately positioned at a measurement position relative to a central axis of the undulator module Use the sensing element to measure a magnetic field at the measurement position; and remove the magnetic field sensor from the opening in the undulator module. The method of claim 10, comprising: inserting a magnetic field sensor including a sensing element into each of the plurality of openings in the undulator module, so that the magnetic field sensor An alignment feature cooperates with a complementary alignment feature on the undulator module, so that the sensing element is accurately positioned at one of a plurality of measurement positions relative to a central axis of the undulator module Use the sensing element to measure a magnetic field at the measurement location; and remove the magnetic field sensor from each of the plurality of openings in the undulator module. The method of claim 10 or 11, further comprising: determining a magnetic field at a central axis of the undulator module from the measured magnetic field at the or each measurement position. Such as the method of claim 10, wherein the undulator module includes a plurality of periodic magnetic structures, the periodic magnetic structures are arranged around a central axis and extend parallel to the central axis, in the periodic magnetic structures Each of them includes a plurality of magnets alternately arranged with a plurality of ferromagnetic elements, and wherein the method further includes: determining at least one of the ferromagnetic elements of at least one of the periodic magnetic structures Permeability. Such as the method of claim 13, which includes: determining the permeability of the ferromagnetic elements of the periodic magnetic structures. Such as the method of claim 13 or 14, which comprises: determining the central axis of the undulator module from the measured permeability of the plurality of the ferromagnetic elements of the plurality of the periodic magnetic structures The magnetic field.

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