DE102024205635A1 - OPTICAL SYSTEM AND LITHOGRAPHY SYSTEM WITH AN OPTICAL SYSTEM - Google Patents

Abstract

An optical system (100) for a lithography system (1), comprising a circuit board (200) formed from a composite material, which circuit board has a flexible region (211), wherein the circuit board (200) has a conductor loop (220) for detecting a magnetic field (B _y , B _z ) acting on the flexible region (211).

Description

The present invention relates to an optical system and a lithography system comprising such an optical system.

Microlithography is used to manufacture microstructured components, such as integrated circuits. The microlithography process is carried out using a lithography system equipped with an illumination system and a projection system. The image of a mask (reticle) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection system in order to transfer the mask structure to the light-sensitive coating of the substrate.

Driven by the pursuit of ever smaller structures in the production of integrated circuits, EUV lithography systems are currently being developed that use light with a wavelength in the range of 0.1 nm to 30 nm, particularly 13.5 nm. Since most materials absorb light at this wavelength, such EUV lithography systems must use reflective optics, i.e., mirrors, instead of the previously used refractive optics, i.e., lenses.

A variety of actuator/sensor devices, such as sensors and actuators, are installed in lithography systems. In general, an actuator/sensor device is suitable for displacing an optical element associated with the actuator/sensor device, such as a mirror, and/or detecting a parameter of the associated optical element, such as a position of the associated optical element or a temperature of the associated optical element. For control and evaluation, such an actuator/sensor device must be electrically connected to an electronic component, in particular to an integrated circuit (IC). Flexible printed circuit boards, also called flexible printed circuit cards or flex PCBs, are used for this purpose. For example, the international patent application PCT/ EP2023/070433 an optical system for a lithography system having a printed circuit board formed from a composite material with a pliable or flexible region.

However, it is possible that magnetic fields within the optical system of the lithography system may act on the circuit board, inducing a voltage in the circuit board and thus detrimentally causing errors in the signal transmission through the circuit board. Conventionally, magnetic fields can be shielded by shielding in such a way that they cause no or hardly any errors on the circuit board. However, such shields require space, which is often insufficient in the optical systems of lithography systems. Furthermore, the use of shields also disadvantageously involves increased design effort and increased costs.

Against this background, it is an object of the present invention to provide an improved optical system.

According to a first aspect, an optical system for a lithography system is proposed, which comprises a circuit board formed from a composite material and having a flexible region, wherein the circuit board has a conductor loop for detecting a magnetic field acting on the flexible region.

By using the conductor loop to detect a magnetic field acting on the flexible region of the circuit board, a voltmeter that can be coupled to the conductor loop can measure the electrical voltage induced by the magnetic field acting on the flexible region of the circuit board, in particular by the magnetic flux passing through the conductor loop. Depending on the measured induced electrical voltage, a magnetic field change, in particular an average magnetic field change, in the flexible region of the circuit board can be determined. The determined magnetic field change can advantageously be used to compensate for a magnetic error caused by the magnetic field. In this case, magnetic errors caused by the magnetic field can therefore be compensated without the use of conventional shielding. This advantageously reduces the space required by the circuit board, which has particular advantages within optical systems in a lithography system.

In this case, the printed circuit board can also be referred to as a printed circuit card. In particular, the printed circuit board has two rigid areas, between which the flexible area is arranged. The flexible area of the printed circuit board can also be referred to as the flexible area.

By using the flexible area of the circuit board, the flexibility during installation of the circuit board in the lithography system is significantly increased. This is particularly advantageous in light of the prevailing space limitations in the lithography system. Printed circuit boards are installed in the lithography system in a bent state. This advantageously reduces or prevents potential interference with components or electronic components integrated into the printed circuit board. Such potential interference includes environmental influences and/or interference caused by generated heat, cold, mechanical interference, and electromagnetic interference.

Due to the flexibility of the flexible circuit board, it is possible to minimize the length of the electrical wires required to connect the components housed in the circuit board housing and other components, such as actuator/sensor devices. Such a minimization of the length of the electrical wires also reduces signal run lengths, thus reducing the impact of potential interference during data transmission and control.

The optical system is preferably a projection optics system of the lithography system or projection exposure system. However, the optical system can also be an illumination system. The projection exposure system can be an EUV lithography system. EUV stands for "Extreme Ultraviolet" and refers to a wavelength of the working light between 0.1 nm and 30 nm. The projection exposure system can also be a DUV lithography system. DUV stands for "Deep Ultraviolet" and refers to a wavelength of the working light between 30 nm and 465 nm.

According to one embodiment, the printed circuit board comprises a plurality N of parallel layers forming the composite material, comprising two outer layers and N-2 inner layers arranged between the two outer layers, with N ≥ 3. The N-2 inner layers are formed by an alternating sequence of conductor layers and insulator layers. The respective layer can itself be formed by multiple layers.

According to a further embodiment, the N-2 inner layers are formed by an alternating sequence of metal layers or metal structures and insulator layers. The metal layers are formed, for example, from copper. The insulator layers are formed, for example, from a glass fiber substrate or an epoxy resin. According to a further embodiment, the outer layers are formed as metal layers suitable for heat spreading. The respective outer layer or layer can also be formed as an insulation layer, preferably as an outgassing-resistant plastic film, or as a varnish.

According to a further embodiment, the conductor loop is arranged in the flexible region such that it is suitable for detecting a magnetic field parallel to the width of the flexible region. Simulations by the applicant show a significantly higher sensitivity between the signals transmitted via the circuit board and magnetic fields that run parallel to the width of the flexible or bendable region of the circuit board. Consequently, in embodiments, it is advantageous to arrange the conductor loop in the circuit board such that it can detect such magnetic fields running parallel to the width of the flexible region.

According to a further embodiment, the conductor loop is formed by a first conductor layer of the N-2 inner layers, by a second conductor layer of the N-2 inner layers and by a conductor connecting the first conductor layer and the second conductor layer.

According to a further embodiment, the first conductor layer and the second conductor layer are two adjacent conductor layers of the N-2 inner layers. These are preferably arranged in the outer region of the stack of the N-2 inner layers.

According to a further embodiment, the conductor connects a first end of the first conductor layer and a first end of the second conductor layer opposite the first end in the stack of N-2 inner layers. The conductor is preferably arranged perpendicular to the first conductor layer and the second conductor layer.

According to a further embodiment, a voltmeter is coupled to the conductor loop, which is configured to measure an electrical voltage induced by the magnetic field acting on the flexible region of the circuit board.

According to a further embodiment, the flexible region has a number M of slots for increasing the flexibility of the flexible region, with M ≥ 1. The flexible region is divided by the M slots into a plurality M+1 of fingers.

According to a further embodiment, each of the M+1 fingers has a respective conductor loop for detecting the magnetic field acting on the flexible region. The smaller the area enclosed by the conductor loop, the smaller the magnetic flux and thus the measured induced voltage. For very small areas and thus very small induced voltages, the relative error becomes larger. To reduce the relative error, a conductor loop is preferably installed in each finger. and the conductor loops are preferably connected in series, so that the total area is increased.

According to a further embodiment, the M+1 conductor loops of the M+1 fingers are coupled to a voltmeter. The voltmeter is configured to measure the electrical voltages induced in the conductor loops by the magnetic field acting on the flexible region.

According to a further embodiment, each of the M+1 conductor loops of the M+1 fingers is coupled to a respective voltmeter, wherein the respective voltmeter is configured to measure the electrical voltage induced in the associated conductor loop by the magnetic field acting on the flexible region. Based on separate measurements of the magnetic flux by induced voltages in the conductor loops and subsequent software-based compensation by a computing unit, a reduction of errors due to external influences can be achieved.

According to a further embodiment, the optical system comprises a plurality X of printed circuit boards formed from a composite material, with X ≥ 2. Each printed circuit board has a flexible region with a conductor loop for detecting a magnetic field acting on the flexible region. The X conductor loops of the X printed circuit boards are connected to one another by conductors.

According to a further embodiment, the circuit board has a first rigid region and a second rigid region. The flexible region is arranged between the first rigid region and the second rigid region, wherein the conductor loop is arranged in the flexible region such that it is suitable for detecting a magnetic field perpendicular to the width of the flexible region. In particular, the conductor loop is preferably laid across the entire width of the flexible region in order to maximize the area used in determining the magnetic field. The reason for this is that for very small regions and thus very small induced voltages, the relative error becomes larger, which is advantageously reduced in the present case by laying the conductor loop across the entire width of the flexible region.

According to a further embodiment, the optical system comprises a vacuum housing in which the circuit board is arranged.

According to a further embodiment, the vacuum housing is designed such that a pressure of 1013.25 hPa to 10 ^-3 hPa prevails in its interior. This pressure range can be referred to as normal pressure to fine vacuum.

According to a further embodiment, the vacuum housing is designed such that a pressure of 10 ^-3 to 10 ^-8 hPa prevails in its interior. This pressure range can be referred to as a fine vacuum to high vacuum.

According to a further embodiment, the vacuum housing is designed such that a pressure of 10 ^-8 to 10 ^-11 hPa prevails in its interior. This pressure range can be referred to as high vacuum to extremely high vacuum.

In embodiments, a vacuum-tight housing in an interior region of the circuit board can be formed by the composite material, in which a number of active and/or passive components are arranged.

The active and/or passive components may also be referred to as active and/or passive components, silicon-based elements, electronic components, or electronic components. In embodiments, the number of active and/or passive components includes an integrated circuit, a processor, a microprocessor, an FPGA, an analog-to-digital converter, a digital-to-analog converter, a transistor, in particular a MOSFET, a silicon-based component, a capacitor, a resistor, and/or an inductor.

By embedding the vacuum-tight housing inside the circuit board, the active and/or passive components can be housed in the vacuum housing of the optical system without the influence of the adjacent/surrounding vacuum. The composite material of the circuit board forms the vacuum-tight housing, which completely encloses the active and/or passive components, either in a vacuum or in a controlled atmosphere.

Because electronic logic based on active and/or passive components can be installed in the vacuum housing in the smallest possible space and close to the optical elements of the lithography system, electrical signals can be further processed locally. The resulting reduction in the required signal path lengths and signal interfaces in and out of the system has advantages in terms of the required energy input and the signal-to-noise ratio. Furthermore, in applications, electrically converted signals can be provided for long transmission distances in the vacuum range using the components embedded in the circuit board. Furthermore, the proposed circuit board with the integrated vacuum-tight housing for electronic components advantageously eliminates the need for additional mechanical separating elements between vacuum and non-vacuum, in particular, the conventionally required metal housings.

According to a further embodiment, the flexible region of the circuit board is arranged, in particular installed, in a bent state in the optical system. Such a bent state provides space-specific advantages in applications. Furthermore, the bent state can advantageously reduce or prevent potential interference with an actuator/sensor device connected to the integrated circuit.

According to a further embodiment, the optical system comprises a number of actuator/sensor devices that are electrically connected to the circuit board. The respective actuator/sensor device is, for example, an actuator (or actuator) for actuating an optical element, a sensor for sensing an optical element or an environment in the optical system, or an actuator and sensor device for actuating and sensing in the optical system. The sensor is, for example, a temperature sensor. The actuator is preferably an actuator using the electrostrictive effect or an actuator using the piezoelectric effect, for example a PMN actuator (PMN; lead magnesium niobate) or a PZT actuator (PZT; lead zirconate titanate). The actuator is, in particular, configured to actuate an optical element of the optical system. Examples of such an optical element include lenses, mirrors, and adaptive mirrors.

According to a further embodiment, the optical system is designed as an illumination optics or as a projection optics of a lithography system.

According to a second aspect, a lithography system is proposed which has an optical system according to the first aspect or according to one of the embodiments of the first aspect.

In this case, "one" is not necessarily limited to exactly one element. Rather, multiple elements, such as two, three, or more, may also be included. Any other counting term used here should also not be understood as implying a limitation to the exact number of elements stated. Rather, numerical deviations, both upward and downward, are possible unless otherwise stated.

Further possible implementations of the invention also include combinations of features or embodiments described above or below with respect to the exemplary embodiments that are not explicitly mentioned. In this case, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

• 1 zeigt einen schematischen Meridionalschnitt einer Projektionsbelichtungsanlage für eine EUV-Projektionslithographie;
• 2A zeigt eine schematische Schnittansicht einer ersten Ausführungsform einer Leiterplatte eines optischen Systems;
• 2B zeigt eine zu der 2A orthogonale schematische Schnittansicht der ersten Ausführungsform der Leiterplatte;
• 3A zeigt eine schematische Schnittansicht einer zweiten Ausführungsform einer Leiterplatte eines optischen Systems;
• 3B zeigt eine zu der 3A orthogonale schematische Schnittansicht der zweiten Ausführungsform der Leiterplatte;
• 4A zeigt eine schematische Schnittansicht einer dritten Ausführungsform einer Leiterplatte eines optischen Systems;
• 4B zeigt eine zu der 4A orthogonale schematische Schnittansicht der dritten Ausführungsform der Leiterplatte;
• 5 zeigt eine schematische Schnittansicht einer vierten Ausführungsform einer Leiterplatte eines optischen Systems; und
• 6 zeigt eine schematische Schnittansicht einer Ausführungsform eines optischen Systems mit einer Mehrzahl von Leiterplatten.

Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention will be explained in more detail below using preferred embodiments with reference to the accompanying figures.

• 1 shows a schematic meridional section of a projection exposure system for EUV projection lithography;
• 2A shows a schematic sectional view of a first embodiment of a circuit board of an optical system;
• 2B shows one to the 2A orthogonal schematic sectional view of the first embodiment of the printed circuit board;
• 3A shows a schematic sectional view of a second embodiment of a circuit board of an optical system;
• 3B shows one to the 3A orthogonal schematic sectional view of the second embodiment of the printed circuit board;
• 4A shows a schematic sectional view of a third embodiment of a circuit board of an optical system;
• 4B shows one to the 4A orthogonal schematic sectional view of the third embodiment of the printed circuit board;
• 5 shows a schematic sectional view of a fourth embodiment of a circuit board of an optical system; and
• 6 shows a schematic sectional view of an embodiment of an optical system with a plurality of circuit boards.

In the figures, identical or functionally equivalent elements are provided with the same reference numerals unless otherwise stated. Furthermore, it should be noted that the representations in the figures are not necessarily to scale.

1 shows an embodiment of a projection exposure system 1 (lithography system), in particular, an EUV lithography system. One embodiment of an illumination system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, an illumination optics 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the remaining illumination system 2. In this case, the illumination system 2 does not include the light source 3.

A reticle 7 arranged in the object field 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 can be displaced via a reticle displacement drive 9, in particular in a scanning direction.

In the 1 For explanation purposes, a Cartesian coordinate system is shown with an x-direction x, a y-direction y and a z-direction z. The x-direction x runs perpendicular to the plane of the drawing. The y-direction y runs horizontally and the z-direction z runs vertically. The scanning direction runs in the 1 along the y-direction y. The z-direction z runs perpendicular to the object plane 6.

The projection exposure system 1 comprises a projection optics 10. The projection optics 10 serves to image the object field 5 into an image field 11 in an image plane 12. The image plane 12 runs parallel to the object plane 6. Alternatively, an angle other than 0° between the object plane 6 and the image plane 12 is also possible.

A structure on the reticle 7 is imaged onto a light-sensitive layer of a wafer 13 arranged in the image plane 12 in the region of the image field 11. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be displaced, in particular along the y-direction y, via a wafer displacement drive 15. The displacement of the reticle 7, on the one hand, via the reticle displacement drive 9, and the displacement of the wafer 13, on the other hand, via the wafer displacement drive 15, can be synchronized with each other.

The light source 3 is an EUV radiation source. The light source 3 emits, in particular, EUV radiation 16, which is also referred to below as useful radiation, illumination radiation, or illumination light. The useful radiation 16 has, in particular, a wavelength in the range between 5 nm and 30 nm. The light source 3 can be a plasma source, for example an LPP source (Laser Produced Plasma) or a DPP source (Gas Discharged Produced Plasma). It can also be a synchrotron-based radiation source. The light source 3 can be a free-electron laser (FEL).

The illumination radiation 16 emanating from the light source 3 is focused by a collector 17. The collector 17 can be a collector with one or more ellipsoidal and/or hyperboloidal reflection surfaces. The at least one reflection surface of the collector 17 can be exposed to the illumination radiation 16 at grazing incidence (GI), i.e., at angles of incidence greater than 45°, or at normal incidence (NI), i.e., at angles of incidence less than 45°. The collector 17 can be structured and/or coated, on the one hand, to optimize its reflectivity for the useful radiation and, on the other hand, to suppress stray light.

After the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 can represent a separation between a radiation source module, comprising the light source 3 and the collector 17, and the illumination optics 4.

The illumination optics 4 comprises a deflecting mirror 19 and, downstream of this in the beam path, a first facet mirror 20. The deflecting mirror 19 can be a flat deflecting mirror or, alternatively, a mirror with a beam-influencing effect beyond the pure deflection effect. Alternatively or additionally, the deflecting mirror 19 can be designed as a spectral filter that separates a useful light wavelength of the illumination radiation 16 from stray light of a different wavelength. If the first facet mirror 20 is arranged in a plane of the illumination optics 4 that is optically conjugated to the object plane 6 as the field plane, it is also referred to as a field facet mirror. The first facet mirror 20 comprises a plurality of individual first facets 21, which can also be referred to as field facets. Of these first facets 21, 1 only a few examples are shown.

The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or partially circular edge contour. The first facets 21 can be designed as flat facets or, alternatively, as convexly or concavely curved facets.

As for example from the DE 10 2008 009 600 A1 is known, the first The first facet mirror 20 can be designed in particular as a microelectromechanical system (MEMS system). For details, refer to the DE 10 2008 009 600 A1 referred to.

Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction y.

In the beam path of the illumination optics 4, a second facet mirror 22 is arranged downstream of the first facet mirror 20. If the second facet mirror 22 is arranged in a pupil plane of the illumination optics 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be arranged at a distance from a pupil plane of the illumination optics 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US 2006/0132747 A1 , the EP 1 614 008 B1 and the US 6,573,978 .

The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

The second facets 23 can also be macroscopic facets, which can be round, rectangular or hexagonal, or alternatively facets composed of micromirrors. In this regard, reference is also made to the DE 10 2008 009 600 A1 referred to.

The second facets 23 may have planar or alternatively convex or concave curved reflection surfaces.

The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a fly's-eye integrator.

It may be advantageous not to arrange the second facet mirror 22 exactly in a plane that is optically conjugate to a pupil plane of the projection optics 10. In particular, the second facet mirror 22 may be arranged tilted relative to a pupil plane of the projection optics 10, as is shown, for example, in the DE 10 2017 220 586 A1 described.

With the help of the second facet mirror 22, the individual first facets 21 are imaged into the object field 5. The second facet mirror 22 is the last bundle-forming mirror or actually the last mirror for the illumination radiation 16 in the beam path before the object field 5.

In a further embodiment of the illumination optics 4 (not shown), a transmission optics can be arranged in the beam path between the second facet mirror 22 and the object field 5, which transmission optics contributes in particular to the imaging of the first facets 21 into the object field 5. The transmission optics can have exactly one mirror, but alternatively also two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 4. The transmission optics can in particular comprise one or two mirrors for normal incidence (NI mirrors, normal incidence mirrors) and/or one or two mirrors for grazing incidence (GI mirrors, grazing incidence mirrors).

The illumination optics 4 has in the version shown in the 1 As shown, after the collector 17 there are exactly three mirrors, namely the deflection mirror 19, the first facet mirror 20 and the second facet mirror 22.

In a further embodiment of the illumination optics 4, the deflection mirror 19 can also be omitted, so that the illumination optics 4 can then have exactly two mirrors after the collector 17, namely the first facet mirror 20 and the second facet mirror 22.

The imaging of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optics into the object plane 6 is usually only an approximate imaging.

The projection optics 10 comprises a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

In the 1 In the example shown, the projection optics 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or a different number of mirrors M1 are also possible. The projection optics 10 is a doubly obscured optic. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection optics 10 has an image-side numerical aperture that is greater than 0.5 and can also be greater than 0.6, for example, 0.7 or 0.75.

Reflecting surfaces of the mirrors Mi can be designed as free-form surfaces without rotational symmetry axis Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflection surface shape. The mirrors Mi, like the mirrors of the illumination optics 4, can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

The projection optics 10 has a large object-image offset in the y-direction y between a y-coordinate of a center of the object field 5 and a y-coordinate of the center of the image field 11. This object-image offset in the y-direction y can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

The projection optics 10 can, in particular, be anamorphic. It has, in particular, different magnifications βx, βy in the x and y directions x, y. The two magnifications βx, βy of the projection optics 10 are preferably (βx, βy) = (+/- 0.25, /+- 0.125). A positive magnification β means imaging without image inversion. A negative sign for the magnification β means imaging with image inversion.

The projection optics 10 thus leads to a reduction in the ratio 4:1 in the x-direction x, i.e. in the direction perpendicular to the scanning direction.

The projection optics 10 leads to a reduction of 8:1 in the y-direction y, i.e. in the scanning direction.

Other magnifications are also possible. Magnifications with the same sign and absolutely identical in the x and y directions (x, y), for example, with absolute values of 0.125 or 0.25, are also possible.

The number of intermediate image planes in the x- and y-directions x, y in the beam path between the object field 5 and the image field 11 can be the same or can be different, depending on the design of the projection optics 10. Examples of projection optics with different numbers of such intermediate images in the x- and y-directions x, y are known from US 2018/0074303 A1 .

Each of the second facets 23 is assigned to exactly one of the first facets 21 to form a respective illumination channel for illuminating the object field 5. This can, in particular, result in illumination according to the Köhler principle. The far field is divided into a plurality of object fields 5 using the first facets 21. The first facets 21 generate a plurality of images of the intermediate focus on the second facets 23 assigned to them.

The first facets 21 are each imaged onto the reticle 7 by an associated second facet 23, superimposed on one another, to illuminate the object field 5. The illumination of the object field 5 is, in particular, as homogeneous as possible. It preferably has a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

By arranging the second facets 23, the illumination of the entrance pupil of the projection optics 10 can be geometrically defined. By selecting the illumination channels, in particular the subset of the second facets 23 that guide light, the intensity distribution in the entrance pupil of the projection optics 10 can be adjusted. This intensity distribution is also referred to as the illumination setting or illumination pupil fill.

A likewise preferred pupil uniformity in the area of defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by redistributing the illumination channels.

Further aspects and details of the illumination of the object field 5 and in particular of the entrance pupil of the projection optics 10 are described below.

The projection optics 10 can, in particular, have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

The entrance pupil of the projection optics 10 cannot usually be precisely illuminated with the second facet mirror 22. When the projection optics 10 images the center of the second facet mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, a surface can be found in which the pairwise determined distance of the aperture rays is minimized. This surface represents the entrance pupil or a surface conjugate to it in spatial space. In particular, this surface exhibits a finite curvature.

The projection optics may have 10 different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element ment, in particular an optical component of the transmission optics, between the second facet mirror 22 and the reticle 7. With the help of this optical element, the different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

At the 1 In the illustrated arrangement of the components of the illumination optics 4, the second facet mirror 22 is arranged in a surface conjugate to the entrance pupil of the projection optics 10. The first facet mirror 20 is arranged tilted relative to the object plane 6. The first facet mirror 20 is arranged tilted relative to an arrangement plane defined by the deflection mirror 19. The first facet mirror 20 is arranged tilted relative to an arrangement plane defined by the second facet mirror 22.

2A shows a schematic sectional view of a first embodiment of a circuit board 200 of an optical system 4, 10 for a lithography system or projection exposure system 1, as shown for example in 1 is shown. In addition, the optical system can also be used in a DUV lithography system, for example. In addition, the 2B for this purpose one to the 2A orthogonal schematic sectional view of the first embodiment of the circuit board 200.

According to the 2A and 2B The printed circuit board 200 has a flexible region 211, which is arranged between a first rigid region 212 and a second rigid region 213. The first rigid region 212 and the second rigid region 213 are each designed, for example, as a connector. The flexible region 211 preferably forms a flexible part between the connectors 212, 213. Since the printed circuit board 200 has a flexible region 211, which is in particular significantly longer than the rigid regions 212, 213, the printed circuit board 200 can also be referred to as a flex PCB.

As the 2A and 2B As further shown, the circuit board 200 has a conductor loop 220 for detecting a magnetic field B _y acting on the flexible region 211. The circuit board 200 is formed from a composite material. Preferably, the circuit board 200 has a plurality N of parallel layers forming the composite material, with N ≥ 3. The parallel layers comprise two outer layers and N-2 inner layers arranged between the two outer layers, wherein the N-2 inner layers are formed by an alternating sequence of conductor layers and insulator layers.

As the 2A and 2B further show, the conductor loop 220 is coupled to a voltmeter V. The voltmeter V is configured to measure an electrical voltage induced by the magnetic field B _y acting on the flexible region 211 of the circuit board 200.

Furthermore, the optical system 4, 10 comprises a computing unit (not shown). The computing unit is configured to determine a magnetic field change, in particular an average magnetic field change, as a function of the measured induced electrical voltage. The determined magnetic field change can advantageously be used to compensate for a magnetic error caused by the magnetic field _By .

In the embodiment of the 2A and 2B The conductor loop 220 is arranged in the flexible region 211 such that it is suitable for detecting a magnetic field B _y parallel to the width of the flexible region 211. Simulations by the applicant have shown a significantly higher sensitivity between signals transmitted via the circuit board 200 and magnetic fields (B _y ) that run parallel to the width of the flexible region 211 than to magnetic fields running in other directions.

For example, the conductor loop 220 is connected by a first conductor loop 221 (see 2B) the N-2 inner layers, by a second conductor layer 222 (see 2B) of the N-2 inner layers and a conductor 223 connecting the first conductor layer 221 and the second conductor layer 222. In other words, two superimposed conductor tracks of the flex PCB 200 can be short-circuited on one side via the connector 212 to form the conductor loop 220. On the other side, the voltage induced in the conductor loop 220 can be measured using the connected voltmeter V.

As the 2A and 2B As shown in the drawings, the first conductor layer 221 and the second conductor layer 222 can be two adjacent conductor layers of the N-2 inner layers, which are preferably arranged in the outer region of the stack of the N-2 inner layers. In this case, the conductor 223 connects a first end of the first conductor layer 221 and a first end of the second layer 222 opposite the first end in the stack of the N-2 inner layers. The conductor 223 is arranged, in particular, perpendicular to the first conductor layer 221 and the second conductor layer 222.

As the 2A further shows, the flexible area 211 has a number M of slots 231-235 to increase the flexibility of the flexible men area 211. Without loss of generality, M = 5 in 2A The M slots 231-235 divide the flexible region 211 into a plurality of M+1 fingers 241-246. For reasons of clarity, the fingers are no longer provided with the reference numerals 241-246 in the subsequent figures.

Furthermore, the 3A a schematic sectional view of a second embodiment of a circuit board 200 of an optical system 4,10, wherein the 3B one to the 3A orthogonal schematic sectional view of the second embodiment of the printed circuit board 200. The second embodiment of the printed circuit board 200 according to the 3A and 3B differs from the first embodiment according to the 2A and 2B in particular in that each of the M+1 fingers 241-246 of the flexible region 211 comprises a respective conductor loop 220 for detecting the magnetic field B _y acting on the flexible region 211. Without loss of generality, M - as in the 2A - also in the 3A equal to 5. Thus, the flexible area 211 of the 3A five slots 231-235 and six fingers. The six conductor loops 220 of the six fingers of the 3A and 3B coupled to a voltmeter V. The voltmeter V is configured to measure the electrical voltages induced by the magnetic field B _y acting on the flexible region 211 in the conductor loops 220 of the six fingers. Depending on the measured induced electrical voltages, a computing unit (not shown) can determine a magnetic field change, in particular an average magnetic field change. The determined magnetic field change can advantageously be used to compensate for a magnetic error caused by the magnetic field B _y .

Furthermore, the 4A a schematic view of a third embodiment of the circuit board 200 of an optical system 4, 10, wherein the 4B one to the 4A orthogonal schematic sectional view of the third embodiment of the printed circuit board 200. The third embodiment according to the 4A and 4B is based on the second embodiment according to the 3A and 3B and differs from this in that each of the M+1 conductor loops 220 is coupled to a respective voltmeter V. Here, the respective voltmeter V is configured to measure the electrical voltage induced in the associated conductor loop 220 by the magnetic field B _y acting on the flexible region 211. A computing unit (not shown) can then use the induced electrical voltages provided by the M+1 voltmeters V to determine a magnetic field change in the flexible region 211. The determined magnetic field change can in turn advantageously be used to compensate for a magnetic error caused by the magnetic field B _y .

The 5 shows a schematic sectional view of a fourth embodiment of a circuit board 200 of an optical system 4, 10. In the example of 5 the magnetic field B _z is perpendicular to the width of the flexible region 211. The conductor loop 220 is according to 5 arranged in the flexible region 211 such that it is suitable for detecting the magnetic field B _z perpendicular to the width of the flexible region 211. In particular, the conductor loop 220 is preferably laid across the entire width of the flexible region 211 in order to maximize the area used in determining the magnetic field B _z . The reason for this is that for very small regions and thus very small induced voltages, the relative error, in particular the measurement error of the voltage, becomes larger, which in the present case is achieved by laying the conductor loop 220 as in 5 shown, is advantageously prevented.

Furthermore, 6 a schematic sectional view of an embodiment of an optical system 4, 10 with a plurality of circuit boards 200. Without limiting the generality, the 6 two printed circuit boards 200. The respective printed circuit board 200 in the 6 is according to the first embodiment according to the 2A and 2B Alternatively, the respective circuit board 200 can also be designed according to the second embodiment according to the 3A and 3B or the third embodiment according to the 4A and 4B or the fourth embodiment according to 5 be trained.

As the 6 shows, the individual conductor loops 220 of the plurality of circuit boards 200 are connected by means of conductors 251, 252. Here, the induced voltage of a plurality of circuit boards 200 can be determined by the present series connection of the 6 be measured using a single voltmeter V and compensated as shown above.

Although the present invention has been described using exemplary embodiments, it can be modified in many ways.

LIST OF REFERENCE SYMBOLS

1

Projection exposure system

2

lighting system

3

light source

4

Lighting optics

5

Object field

6

Object level

7

Reticle

8

Reticle holder

9

Reticle displacement drive

10

Projection optics

11

Image field

12

Image plane

13

wafers

14

Wafer holder

15

Wafer relocation drive

16

Illumination radiation

17

collector

18

Intermediate focal plane

19

Deflecting mirror

20

first faceted mirror

21

first facet

22

second facet mirror

23

second facet

100

optical system

200

circuit board

211

flexible area of the circuit board

212

rigid area of the circuit board

213

rigid area of the circuit board

220

Conductor loop

221

first conductor layer

222

second conductor layer

223

Director

231

slot

232

slot

233

slot

234

slot

235

slot

241

finger

242

finger

243

finger

244

finger

245

finger

246

finger

251

Director

252

Director

By

Magnetic field (parallel to the width of the flexible area)

Bz

Magnetic field (perpendicular to the width of the flexible area)

M1

Mirror

M2

Mirror

M3

Mirror

M4

Mirror

M5

Mirror

M6

Mirror

V

Voltmeter

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2023/070433 [0004]
• DE 10 2008 009 600 A1 [0052, 0056]
• US 2006/0132747 A1 [0054]
• EP 1 614 008 B1 [0054]
• US 6,573,978 [0054]
• DE 10 2017 220 586 A1 [0059]
• US 2018/0074303 A1 [0073]

Claims (15)

Optical system (4, 10) for a lithography system (1), comprising a circuit board (200) formed from a composite material, which circuit board has a flexible region (211), wherein the circuit board (200) has a conductor loop (220) for detecting a magnetic field (B _y , B _z ) acting on the flexible region (211). Optical system according to Claim 1 , wherein the printed circuit board (200) has a plurality N of parallel arranged layers forming the composite material, comprising two outer layers and N-2 inner layers arranged between the two outer layers, wherein the N-2 inner layers are formed by an alternating sequence of conductor layers and insulator layers, with N ≥ 3. Optical system according to Claim 1 or 2 , wherein the conductor loop (220) is arranged in the flexible region (211) in such a way that it is suitable for detecting a magnetic field (B _y ) parallel to the width of the flexible region (211). Optical system according to Claim 2 or 3 , wherein the conductor loop (220) is formed by a first conductor layer (221) of the N-2 inner layers, by a second conductor layer (222) of the N-2 inner layers and a conductor (223) connecting the first conductor layer (221) and the second conductor layer (222). Optical system according to Claim 4 , wherein the first conductor layer (221) and the second conductor layer (222) are two adjacent conductor layers of the N-2 inner layers, which are preferably arranged in the outer region of the stack of the N-2 inner layers. Optical system according to Claim 4 or 5 , wherein the conductor (223) connects a first end of the first conductor layer (221) and a first end of the second conductor layer (222) opposite the first end in the stack of N-2 inner layers and is arranged perpendicular to the first conductor layer (221) and the second conductor layer (222). Optical system according to one of the Claims 4 until 6 , wherein a voltmeter (V) is coupled to the conductor loop (220), which is designed to measure an electrical voltage induced by the magnetic field (B _y , B _z ) acting on the flexible region (211) of the circuit board (200). Optical system according to Claim 1 until 3 , wherein the flexible region (211) has a number M of slots (231-235) for increasing the flexibility of the flexible region (211), wherein the flexible region (211) is divided by the M slots (231-235) into a plurality M+1 of fingers (241-246), with M ≥ 1. Optical system according to Claim 8 wherein each of the M+1 fingers (241-246) comprises a respective conductor loop (220) for detecting the magnetic field (B _y ) acting on the flexible region (211). Optical system according to Claim 9 , wherein the M+1 conductor loops (220) of the M+1 fingers (241-246) are coupled to a voltmeter (V) which is designed to measure the electrical voltages induced in the conductor loops (220) by the magnetic field (B _y ) acting on the flexible region (211). Optical system according to Claim 9 , wherein each of the M+1 conductor loops (220) of the M+1 fingers (241-246) is coupled to a respective voltmeter (V), wherein the respective voltmeter (V) is arranged to measure the electrical voltage induced in the associated conductor loop (220) by the magnetic field (B _y ) acting on the flexible region (211). Optical system according to one of the Claims 1 until 11 , wherein the optical system (100) comprises a plurality X of printed circuit boards (200) formed from a composite material, with X ≥ 2, wherein the respective printed circuit board (200) has a flexible region (211) which has a conductor loop (220) for detecting a magnetic field (B _y ) acting on the flexible region (211), wherein the X conductor loops (220) of the X printed circuit boards (200) are connected to one another by means of conductors (251, 252). Optical system according to Claim 1 or 2 , the circuit board (200) has a first rigid region (212) and a second rigid region (213), wherein the flexible region (211) is arranged between the first rigid region (212) and the second rigid region (213), wherein the conductor loop (220) is arranged in the flexible region (211) in such a way that it is suitable for detecting a magnetic field (B _z ) perpendicular to the width of the flexible region (211). Optical system according to one of the Claims 1 until 13 , wherein the optical system (100) is designed as an illumination optics (4) or as a projection optics (10) of a lithography system (1). Lithography system (1) with an optical system (100) according to one of the Claims 1 until 14 .

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