DE102023200933B4 - Cooling device for cooling a position-sensitive component of a lithography system and lithography system - Google Patents

Abstract

Cooling device (200) for cooling a position-sensitive component (102) of a lithography system (1), comprising:
a liquid line (208) for transporting a cooling liquid (206),
a silencer device (216) for damping a pressure fluctuation of the cooling liquid (206), wherein the silencer device (216) has a liquid chamber (218) fluidly connected to the liquid line (208), a gas chamber (220) for receiving a gas (222) and an elastic separating membrane (224) separating the gas chamber (220) from the liquid chamber (218),
a gas line (230) fluidly connected to the gas chamber (220), and
a sound absorption element (234) arranged within the gas line (230).

Description

The present invention relates to a cooling device for cooling a position-sensitive component of a lithography system and a lithography system with a corresponding cooling device.

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 positioned in the image plane of the projection system. This transfers 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.

The demands on the accuracy and precision of the imaging properties of lithography systems are constantly increasing. From a dynamic perspective, it is important to minimize the influence of interference on the movement of various position-sensitive components of the lithography system.

For example, very precise positioning of optical components, especially mirrors, of the lithography system is required. Dynamic disturbances in optical components can be generated, for example, by the movement of other components of the lithography system or by acoustic disturbances. Acoustic disturbances can be transmitted as pressure fluctuations of a coolant in the cooling lines of a cooling device of the lithography system to cooled, position-sensitive components of the lithography system. Pressure fluctuations in the coolant are generated, for example, by flow-induced vibrations (FIV).

With the further increase in the complexity of lithography systems, further dynamic disturbances within and outside the system are to be expected, making additional mechanisms for their suppression or compensation desirable and necessary. Conventional solutions for reducing disturbance excitation of mirrors in a lithography system due to flow-induced vibrations are known, for example, from WO 2021 013 441 A1 known.

Further state of the art in this field are the US 6 002 987 A , the DE 103 54 453 A1 , the US 3 061 039 A , the US 3 038 553 A as well as the US 2 233 804 A .

Against this background, it is an object of the present invention to provide an improved cooling device for a lithography system and a corresponding lithography system.

• eine Flüssigkeitsleitung zum Transportieren einer Kühlflüssigkeit,
• eine Schalldämpfereinrichtung zum Dämpfen einer Druckschwankung der Kühlflüssigkeit, wobei die Schalldämpfereinrichtung eine mit der Flüssigkeitsleitung fluidverbundene Flüssigkeitskammer, eine Gaskammer zum Aufnehmen eines Gases und eine die Gaskammer von der Flüssigkeitskammer abtrennende elastische Trennmembran aufweist,
• eine mit der Gaskammer fluidverbundene Gasleitung, und ein innerhalb der Gasleitung angeordnetes Schallabsorptionselement.

Accordingly, a cooling device for cooling a position-sensitive component of a lithography system is proposed. The cooling device comprises:

• a liquid line for transporting a cooling liquid,
• a silencer device for damping a pressure fluctuation of the cooling liquid, the silencer device comprising a liquid chamber fluidly connected to the liquid line, a gas chamber for receiving a gas, and an elastic separating membrane separating the gas chamber from the liquid chamber,
• a gas line fluidly connected to the gas chamber, and a sound absorption element arranged within the gas line.

The silencer device enables the damping of pressure fluctuations in the coolant by changing the volume available for the coolant. In particular, the elastic separating membrane of the silencer device is designed to deform, thereby changing the volume of the liquid chamber at the expense of the volume of the gas chamber. This can significantly reduce the propagation of pressure fluctuations through the coolant.

The gas line connected to the gas chamber of the silencer device is used to supply gas to and discharge gas from the gas chamber. The gas line can be used to adjust and/or monitor the gas pressure in the gas chamber. For example, the gas pressure of a gas absorbed by the gas chamber can be adjusted and/or monitored for the first time. which can be readjusted or regulated after/during an operating period.

However, the gas line also provides an acoustic coupling to the silencer device, through which vibrations can be transmitted. The sound absorption element located within the gas line can prevent or reduce acoustic interference via the gas line to the silencer device and thus to the coolant and the position-sensitive component. For example, additional standing waves and resonance peaks can be avoided.

The position-sensitive component of the lithography system can be an optical or mechanical component of the lithography system, e.g., a projection optics of the lithography system. The position-sensitive component is, in particular, a component that must be held in a precise position with only small tolerances during operation of the lithography system.

The position-sensitive component of the lithography system is, for example, a mirror of the lithography system, e.g., a mirror of the projection optics of the lithography system. The mirrors of the projection optics of an EUV lithography system are typically movably mounted on a support frame by means of actuators to enable the position of the respective mirror to be precisely adjusted.

The position-sensitive component of the lithography system can also be a frame structure that serves as a (e.g., optical) reference. The position-sensitive component can, for example, be a sensor frame of the lithography system, e.g., the projection optics of the lithography system. A sensor frame typically has a sensor device for measuring a current position of one or more optical components of the lithography system relative to the sensor frame. The sensor frame is mounted, for example, in a vibration-decoupled manner with respect to a support frame of the optical component(s). The sensor device comprises, for example, one or more sensors, such as interferometers and/or other measuring devices for detecting a position of the optical component(s). The optical component(s) can, for example, have reflector elements for reflecting light emitted by the sensors (e.g., laser light). For example, the one or more sensors serve to detect a position of the optical component(s) in six degrees of freedom. The six degrees of freedom include, in particular, three translational degrees of freedom (e.g. in three mutually perpendicular spatial directions) and three rotational degrees of freedom (e.g. with respect to a rotation around the three mutually perpendicular spatial directions).

The proposed cooling device with the silencer device, which provides a compressible gas volume by means of the elastic separating membrane, can dampen pressure fluctuations in the coolant and reduce or prevent transmission to the position-sensitive component. Furthermore, acoustic interference via the gas line is also reduced or prevented by the sound absorption element arranged in the gas line. Consequently, greater precession of the position and thus of the optical properties or reference properties of the position-sensitive component can be achieved. Consequently, the imaging properties of the lithography system can be improved. Furthermore, interference excitations can be better compensated, even in increasingly complex lithography systems with a growing number of interference sources.

The lithography system is, for example, an EUV or DUV lithography system. EUV stands for "extreme ultraviolet" (EUV) and refers to a wavelength of the working light in the range of 0.1 nm to 30 nm, specifically 13.5 nm. Furthermore, DUV stands for "deep ultraviolet" (DUV) and refers to a wavelength of the working light between 30 nm and 250 nm.

The EUV or DUV lithography system comprises an illumination system and a projection system. In particular, the EUV or DUV lithography system projects the image of a mask (reticle) illuminated by the illumination system onto a substrate coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection system, for example, a silicon wafer, using the projection system to transfer the mask structure to the light-sensitive coating of the substrate.

The liquid line (“cooling line”) is, for example, a pipe for conducting the cooling liquid. The liquid line comprises, for example, a metal pipe and/or a stainless steel pipe. The liquid line can, for example, have a circular cross-section. The cooling liquid is or comprises, for example, water. The liquid line serves, for example, to transport the cooling liquid to and/or from the position-sensitive component. The liquid line serves, for example, to transport the cooling liquid from a cooling unit of the cooling device to the position-sensitive component and/or from the position-sensitive component. (back) to the cooling unit. The cooling device may also have more than one liquid line.

The cooling device is used in particular to avoid high temperatures and temperature fluctuations of the position-sensitive component.

In particular, mirrors in EUV lithography systems (as an example of position-sensitive components) heat up due to the absorption of high-energy EUV radiation. The resulting high temperatures and temperature fluctuations in the mirror and the associated thermal deformation of the mirror can lead to wavefront aberrations and thus impair the imaging properties of the mirrors. To prevent thermally induced deformations, mirrors in the lithography system can be actively cooled.

The cooling device can also be used (in addition to or instead of) cooling, for example, a sensor frame (as an example of a position-sensitive component). This can prevent the sensor frame from heating up due to thermal radiation. Thermal radiation is caused in particular by working light of the lithography system absorbed by mirror surfaces or structural elements. Other heat sources can be, for example, actuators and heating heads. With the help of the cooling device, a stable temperature environment can be created for the sensor frame. This allows a position measurement of the mirror or the multiple mirrors to be carried out with greater accuracy using the sensor device held by the sensor frame.

The cooling device further comprises, for example, a cooling unit for cooling the cooling liquid, one or more pumps for generating a required coolant flow rate of the cooling liquid and one or more valves for controlling the cooling flow.

Cooling requires a specific coolant flow rate, which is achieved via a pump system. This results in dynamic disturbances, as each pump generates local pressure fluctuations. These are transmitted through the entire cooling circuit via coolant sound (water sound, longitudinal water sound wave). Furthermore, every change in cross-section and every deflection of the liquid line, as well as every installed valve in the cooling circuit, can represent a source of disturbance that causes local pressure fluctuations in the liquid. This type of dynamic disturbance is also called flow-induced vibrations (FIV). The water sound transmits the disturbance to the cooled position-sensitive component. This causes the position of the position-sensitive component to deviate from a target position. In particular, a pressure surge from the coolant acts on surfaces of the cooled position-sensitive component. The pressure surge is converted into a force on the surfaces it acts on. This force causes the position of the position-sensitive component to deviate from the target position.

The liquid line, e.g., a liquid chamber of the liquid line, is designed for the flow of the cooling liquid. Since the liquid chamber of the liquid line is fluidically connected to the liquid chamber of the silencer device, the cooling liquid can also penetrate into the liquid chamber of the silencer device. Due to the elastic separating membrane, which separates the liquid chamber of the silencer device from its gas chamber, the volume of the liquid chamber and the gas chamber are variable, while the total volume of the liquid and gas chambers remains constant. Consequently, the elastic separating membrane can change the volume and thus the pressure of the cooling liquid depending on the volume and pressure of the gas in the gas chamber.

The gas line connects, for example, the gas chamber of the silencer device to a gas supply device. The gas supply device includes, for example, a gas pump, a gas reservoir, one or more valves, etc. The gas line can also connect the silencer device to one or more other silencer devices of the cooling device.

The gas in the gas chamber and gas line includes, for example, air, clean air, nitrogen, helium, and/or another gas. Clean air is, for example, air according to one of the purity classes 1 to 9 of the ISO standard. ISO 8573-1:2010 .

For example, the sound absorption element completely fills the gas line in cross-section. The geometric shape of the sound absorption element is adapted to the internal cross-section of the gas line.

More than one sound absorption element can also be arranged in the gas line. For example, the multiple sound absorption elements are spaced apart from one another and/or arranged at different locations in the gas line.

According to one embodiment, the sound absorption element comprises a gas-permeable, porous absorber material.

The material structure of the porous absorber material slows down the vibration energy of the gas particles in the gas line, resulting in friction effects. Thus, the sound energy of the gas is at least partially converted into heat energy.

The porous absorber material comprises, for example, an open-pore material, a foam material, melamine foam, PUR foam, ceramic, silicon carbide, porous silicon carbide ceramic material, metal, rock wool and/or glass wool.

According to a further embodiment, the porous absorber material comprises a porous foam and/or a fibrous material.

According to a further embodiment, the sound absorption element is attached to the gas line and/or to an inner wall of the gas line.

For example, the sound absorption element is clamped into the gas line (e.g. elastically) and/or glued, welded, screwed or otherwise mechanically attached to the inner wall of the gas line.

According to a further embodiment, the silencer device comprises a resonance absorber, a Helmholtz resonator, and/or a neck portion which fluidly connects the liquid line to the liquid chamber of the silencer device.

This achieves sound damping, i.e. the damping of a coolant pressure fluctuation, based on a resonance effect.

A Helmholtz resonator is a particular example of a resonance absorber. A Helmholtz resonator has a resonator volume, which in this case is provided by the volume of the liquid chamber. Furthermore, a Helmholtz resonator has a resonator neck (neck section) that is fluidly connected to the resonator volume. A pressure wave from the cooling liquid in the line excites the cooling liquid in the resonator neck to vibrate, with the portion of cooling liquid in the resonator neck vibrating against the portion of cooling liquid in the liquid chamber. Sound dampening is achieved analogously to a mass-spring system.

A resonance absorber is, for example, from the DE 10 2008 009 600 A1 known.

According to a further embodiment, the cooling device comprises a plurality of silencer devices, each comprising a liquid chamber fluidly connected to the liquid line, a gas chamber, and an elastic separating membrane separating the gas chamber from the liquid chamber, wherein the gas line is fluidly connected to a plurality of gas chambers of the plurality of silencer devices.

Consequently, the gas chambers of multiple silencer devices can be connected to the same gas line. Thus, the gas chambers of multiple silencer devices can be supplied with gas using a single gas supply unit. Furthermore, the gas pressure in multiple gas chambers of multiple silencer devices can be adjusted and/or monitored using a single control/regulating device.

The plurality of silencer devices each serve in particular to dampen a pressure fluctuation of the cooling liquid in the liquid line.

The gas line is also fluidly connected in particular to several gas chambers of the several silencer devices for supplying and discharging gas into and from the corresponding gas chambers.

For example, the sound absorption element arranged in the gas line can prevent or reduce acoustic coupling between several sound absorption elements via the gas line.

According to a further embodiment, the sound absorption element is arranged in a section of the gas line which fluidly connects a gas chamber of a first silencer device and a gas chamber of a second silencer device.

This means that the first silencer device and the second silencer device can be supplied via the same gas line and yet be at least partially acoustically decoupled.

According to a further embodiment, the cooling device comprises a control and/or regulating device for controlling and/or regulating a gas pressure of a gas in the gas chamber of the one or more silencer devices, wherein the control and/or regulating device is configured to control and/or regulate a gas supply and/or a gas discharge into or from the gas chamber of the one or more silencer devices.

With the help of the control/regulating device, a gas pressure (“preload pressure”) in the gas chamber must be set before the cooling device is put into operation.

In addition, a gas pressure changed due to a leak, a change in temperature, etc., for example during operation, can be set or regulated to a setpoint.

According to a further embodiment, the cooling device comprises a sensor device for detecting a gas pressure of a gas in the gas chamber of the one or more silencer devices.

For example, in the case where the cooling device comprises a plurality of silencer devices, the sensor device is configured to detect the gas pressure in a plurality of or all gas chambers of the plurality of silencer devices.

The sensor device comprises, for example, one or more pressure sensors. The pressure sensors are in particular in fluid communication with the gas in the gas chamber and/or the gas line. The pressure sensors include, for example, piezoelectric pressure sensors, microphone transducers, or other pressure measuring devices for measuring gas pressure.

According to a further embodiment, the silencer device is arranged upstream of the position-sensitive component with respect to a flow direction of a cooling liquid in the liquid line.

For example, the respective silencer device is arranged immediately and/or directly in front of a respective position-sensitive component with respect to the flow direction.

The term "direct" is to be understood here as meaning that there are no (significant) sources of FIV between the position-sensitive component and the silencer device. Significant sources of FIV include, for example, pumps, valves, changes in line cross-section, line deflections, and/or line bends.

This allows acoustic interference to the position-sensitive component to be reduced even further.

According to a further embodiment, a first silencer device is arranged upstream (e.g., immediately and/or directly upstream) of the position-sensitive component with respect to a flow direction of a cooling liquid in the liquid line, and a second silencer device is arranged downstream (e.g., immediately and/or directly downstream) of the position-sensitive component with respect to the flow direction.

According to a further embodiment, a section of the fluid line between the silencer device and the position-sensitive component is free of FIV sources, pumps, valves, line cross-sectional changes, line deflections and/or line bends.

FIV sources are sources of flow-induced/flow-induced vibrations (FIV).

This prevents significant acoustic disturbances from being induced in the coolant downstream of the silencer. Consequently, dynamic vibration excitation of the position-sensitive component caused by pressure waves from the coolant can be minimized.

According to a further embodiment, the one or more silencer devices are each configured to dampen pressure fluctuations of the cooling liquid in a frequency range of 1 Hz to 2 kHz, 1 Hz to 1 kHz, 1 to 800 Hz, 1 to 500 Hz, 1 to 400 Hz, 1 to 200 Hz, 1 to 100 Hz and/or 50 to 150 Hz.

According to a further embodiment, the sound absorption element in the gas line is designed to dampen pressure fluctuations of the gas in a frequency range of 1 Hz to 2 kHz, 1 Hz to 1 kHz, 1 to 800 Hz, 1 to 500 Hz, 1 to 400 Hz, 1 to 200 Hz, 1 to 100 Hz and/or 50 to 150 Hz.

According to a further aspect, a lithography system is proposed. The lithography system comprises a position-sensitive component and a cooling device as described above for cooling the position-sensitive component.

The cooling device and/or the position-sensitive component is preferably part of the projection system of the projection exposure system. However, the cooling device and/or the position-sensitive component can also be part of an illumination system of the projection exposure 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 250 nm.

In this case, "one" is not necessarily limited to exactly one element. Rather, multiple elements, such as two, three, or more, may 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 die EUV-Projektionslithographie;
• 2 zeigt ein optisches System mit einer optischen Komponente der Projektionsbelichtungsanlage aus 1 gemäß einer Ausführungsform;
• 3 zeigt eine Kühlvorrichtung zum Kühlen der optischen Komponente aus 2 gemäß einer Ausführungsform;
• 4 zeigt einen Abschnitt einer Gasleitung der Kühlvorrichtung aus 3;
• 5 zeigt eine Teilansicht einer Kühlvorrichtung zum Kühlen der optischen Komponente aus 2 gemäß einer weiteren Ausführungsform; und
• 6 zeigt eine Kühlvorrichtung zum Kühlen der optischen Komponente aus 2 gemäß einer weiteren Ausführungsform.

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;
• 2 shows an optical system with an optical component of the projection exposure system from 1 according to one embodiment;
• 3 shows a cooling device for cooling the optical component of 2 according to one embodiment;
• 4 shows a section of a gas line of the cooling device from 3 ;
• 5 shows a partial view of a cooling device for cooling the optical component of 2 according to a further embodiment; and
• 6 shows a cooling device for cooling the optical component of 2 according to a further embodiment.

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. 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 conjugate 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 As is known, the first facets 21 themselves can also be composed of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirror 20 can in particular be designed as a microelectromechanical system (MEMS system). For details, reference is made to 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 B1 .

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 beam-forming or actually the last mirror for the illumination radiation 16 in the beam path in front of 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.

Reflection surfaces of the mirrors Mi can be designed as freeform surfaces without a rotational symmetry axis. Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one rotational symmetry axis 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 with the aid of the first facets 21. The first facets 21 generate a plurality of images of the intermediate focus on the second facets 23 respectively 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.

It is possible that the projection optics 10 have different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided 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.

2 shows an optical system 100 with an optical component 102 (as an example of a position-sensitive component) according to one embodiment.

The optical component 102 is, for example, a mirror of the projection exposure system 1 (lithography system), in particular of the projection optics 10, made of 1 The optical component 102 is, for example, one of the mirrors M1-M6. In the following, the position-sensitive component 102 is described as a mirror; however, in other examples, it may also be an optical or mechanical component other than a mirror.

As in 2 As shown, the mirror 102 comprises a coating 104 with an optically active surface 106. The mirror 102 also comprises a substrate 108. Cooling lines 110 are arranged in the substrate 108, through which a cooling liquid 112, such as water, is passed in order to actively cool the mirror 102. Cooling of the mirror 102 serves to prevent thermal deformations of the mirror 102, for example upon irradiation with high-energy EUV radiation 16 ( 1 ), to avoid.

The mirror 102 is movably mounted on a support frame 116 by means of an actuator device 114. The actuator device 114 includes, for example, a plurality of actuators 118 and a drive unit (not shown). The actuator device 114 serves, for example, to position the mirror 102 with respect to six degrees of freedom (translation in the X, Y, and Z directions and rotation about the X, Y, and Z directions).

The optical system 100 further comprises a sensor device 120 for detecting a current position of the mirror 102. The sensor device 120 is 2 only indicated schematically. The sensor device 120 has a or multiple sensors, such as interferometers. The sensors of the sensor device 120 are attached, for example, to a sensor frame (not shown). The sensor frame is attached, for example, in a vibration-decoupled manner to the support frame 116. For example, a current position of the mirror 102 is detected using laser beams 122. The sensor device 120 is configured, for example, to detect the position of the mirror 102 in the six degrees of freedom.

In 3 A cooling device 200 for cooling a position-sensitive component 102 (e.g., the mirror 102) is shown. The cooling device 200 has a cooling circuit 202. The cooling device 200 includes a cooling unit 204 for cooling a cooling liquid 206 and a liquid line 208 (cooling line 208) for transporting the cooling liquid 206. The cooling device 200 also includes one or more pumps 210 for generating a required coolant flow rate of the cooling liquid 206. The cooling device 200 further includes one or more valves 212 for controlling the cooling flow.

The cooling device 200 can also serve to cool several position-sensitive components 102, 102', 102" of the lithography system 1 ( 6 ).

Pumps of the cooling device 200, such as pump 210, cause local pressure fluctuations in the coolant 206. These pressure fluctuations are transmitted through the entire cooling circuit 202 via longitudinal water sound waves. Furthermore, cross-sectional changes (not shown) of the cooling line 208, deflections 214 of the cooling line 208, and valves 212 of the cooling device 200 can also represent sources of interference that cause local pressure fluctuations in the coolant 206. Water sound transmits such acoustic interference to the cooled position-sensitive component 102 (e.g., the mirror 102). This can lead to an undesirable change in the position of the position-sensitive component 102, causing its actual position to deviate from a desired position.

In the in the 3 , 5 and 6 In the examples shown and the following description, the cooling device 200, 300, 400 serves, for example, to cool a mirror 102. In other examples, however, the cooling device 200, 300, 400 can also serve to cool other position-sensitive components, such as other mirrors and/or a sensor frame (not shown) of the projection exposure apparatus 1 (lithography apparatus).

To dampen pressure fluctuations of the cooling liquid 206, the cooling device 200 includes a silencer device 216. The silencer device 216 has a liquid chamber 218 for receiving the cooling liquid 206 and a gas chamber 220 for receiving a gas 222. The liquid chamber 218 is separated from the gas chamber 220 by an elastic separating membrane 224. Furthermore, the liquid chamber 218 is fluidly connected to the liquid line 208 (i.e., to a liquid space 226 within the liquid line 208). Thus, the cooling liquid 206 can penetrate from the liquid line 208 into the liquid chamber 218 of the silencer device 216.

In the 3 In the state shown, the separating membrane 224 is in a resting state. The resting state is a relaxed, undeformed state of the separating membrane 224. By deforming the separating membrane 224, a volume of the liquid chamber 218 can be changed at the expense of a volume of the gas chamber 220. For example, an increase in pressure of the cooling liquid 206 can be dampened by expanding the cooling liquid 206 and compressing the gas 222 in the gas chamber 220. Accordingly, periodic pressure fluctuations of the cooling liquid 206 can also be dampened using the compressible gas chamber 220.

As in 3 As shown, the silencer device 216 can have a neck portion 228 that fluidly connects the liquid space 226 of the liquid line 208 to the liquid chamber 218 of the silencer device 216. The silencer device 216 corresponds, for example, to a resonance absorber and/or a Helmholtz resonator, in which the sound damping or sound absorption is achieved through a resonance effect. In particular, a portion of the cooling liquid 206 held in the neck portion 228 can vibrate against a portion of the cooling liquid 208 held in the liquid chamber 218, so that the damping occurs based on mass-spring damping.

The silencer device 216 also includes a gas line 230. The gas line 230 serves, for example, to supply the gas chamber 220 with gas 222 and to monitor a gas pressure P _G of the gas 222 in the gas chamber 220.

The reference number 232 in 4 denotes a gas supply device. The gas supply device 232 can be, for example, a gas pump 354, a gas reservoir 356, one or more valves, etc. ( 5 ) include.

In order to reduce and/or avoid the transmission of acoustic disturbances through the gas line 230 to the silencer device 216, a Sound absorption element 234 arranged as in 4 shown. The sound absorption element 234 is gas-permeable and sound-absorbing.

The sound absorption element 234 is, for example, a porous absorber material 236 such as an open-pore PUR foam or the like. However, the absorber material 236 can also be another suitable absorber material.

4 shows an enlarged partial section of the gas line 230 with the sound absorption element 234. The sound absorption element 234, for example, completely fills the gas line 230 when viewed in cross-section. In other words, an outer surface 240 of the sound absorption element 234 lies directly against an inner surface 242 of the gas line 230. In particular, a geometric shape of the sound absorption element 234 is adapted, for example, to a cross-sectional shape of the gas line 230. Because there is no gap between the sound absorption element 234 (i.e., its outer surface 240) and the gas line 230 (i.e., its inner surface 242), the gas 222 is transmitted completely through the sound absorption element 234, whereby sound absorption is very good.

As in 4 As shown, the gas line 230 has, for example, a circular cross-section. In this case, the sound absorption element 234 accordingly has, for example, a cylindrical shape. In other examples, however, the gas line 230 may also have a cross-section other than circular. Furthermore, the sound absorption element 234 may also have a shape adapted to a different cross-section of the gas line 230.

Furthermore, the sound absorption element 234 is mounted, for example, within the gas line 230. In the 4 In the example shown, the sound absorption element 234 is a deformable foam 236 that is elastically clamped into the gas line 230. In other examples, a sound absorption element 234 may also be glued, welded, screwed, or otherwise mechanically attached to the inner surface 242 (inner wall 242) of the gas line 230.

5 shows a partial section of a cooling device 300 according to a further embodiment. In the following, only differences to the cooling device 200 from 3 described, the other features of the cooling device 300 correspond to those of the cooling device 200.

The cooling device 300 also has a silencer device 316 with a liquid chamber 318 and a gas chamber 320. Furthermore, the cooling device 300 has a gas line 330 for monitoring a gas pressure P _G in the gas chamber 320. Within the gas line 330, similar to the embodiment of 3 , a sound absorption element 334 is arranged.

The gas line 330 is connected to the gas chamber 320 of the silencer device 316 by means of a valve 350.

The cooling device 300 also has a gas supply device 332. The gas supply device 332 comprises a hydraulic unit 352 with a pump 354 and a gas reservoir 356. Furthermore, the gas supply device 332 comprises a control and regulating device 358 for controlling and regulating the gas pressure P _G of the gas 222 in the gas chamber 320.

Furthermore, the cooling device 300 comprises a sensor device 360 for detecting the gas pressure P _G of the gas 222 in the gas chamber 320.

The control and regulating device 358 is configured, for example, to regulate the gas pressure P _G in the gas chamber 320 to a predetermined target value based on an actual value of the gas pressure P _G in the gas chamber 320 detected by the sensor device 360. The control and regulating device 358 receives, for example, a sensor signal A from the sensor device 360. Furthermore, the control and regulating device 358 sends, for example, a control signal B, C to the valve 350 and/or to the pump 354 for supplying gas 222 from the reservoir 356 to the gas chamber 320 or for discharging gas 222 from the gas chamber 320 into the reservoir 356.

Using the control and regulating device 358, for example, the gas pressure P _G can be set to a predetermined value before the cooling device 300 is first put into operation ("preload pressure"). This allows the compressibility of the gas 222 in the gas chamber 320 required for sound attenuation by the silencer device 316 to be preset.

Furthermore, a decrease in the gas pressure P _G during operation of the cooling device 300, for example due to a leak, can be detected by means of the sensor device 360 and regulated to a target value by means of the control and regulating device 358. In particular, a gas supply to the gas chamber 320 of the silencer device 316 can be controlled and/or regulated based on a manipulated variable determined by the control and regulating device 358.

In 6 a cooling device 400 according to a further embodiment is shown. In the following, only differences to the cooling device 200 according to 3 described, the other features of the cooling device 400 correspond to those of the cooling device 200.

The cooling device 400 is configured to cool a plurality of position-sensitive components 102, 102', 102" (e.g., a plurality of mirrors 102, 102', 102").

The cooling device 400 comprises, similar to the cooling device 200 in 3 , a cooling unit 404 for cooling a cooling liquid 206 ( 3 ) and a cooling line 408 for transporting the cooling liquid 206 to the mirrors 102, 102', 102". The cooling line 408 in the example of 6 In particular, a branched cooling line 408 is provided to cool the plurality of mirrors 102, 102', 102". The cooling device 400 also comprises, as the cooling device 200 in 3 , a pump 410 and several valves 412 for controlling a coolant flow rate.

Furthermore, the cooling device 400 is provided with a plurality of silencer devices 416, which are distributed over the cooling line 408. In particular, a silencer device 416 is arranged directly in front of each mirror 102, 102', 102" to be cooled in order to best prevent the transmission of an acoustic disturbance excitation to the corresponding mirror 102, 102', 102". The silencer devices 416 are arranged, in particular with respect to a flow direction S of the cooling liquid 206, directly in front of a corresponding mirror 102, 102', 102". Although in 6 not shown, a further silencer device 416 can also be arranged immediately after each mirror 102, 102', 102", as seen in the flow direction S. The term "immediately" is to be understood in the present case such that no (significant) FIV sources are arranged between a mirror 102, 102', 102" and the corresponding silencer device 416. Significant FIV sources can be considered, for example, the pump 410, the valves 412 and each line deflection 414 of the liquid line 408.

In addition, further silencer devices 416 can be arranged at any location in the cooling circuit 402. In particular, after FIV sources, with respect to the flow direction S of the cooling liquid 206, an arrangement of a silencer device 416 is particularly advantageous. For example, in 6 a further silencer device 416 is arranged immediately after the pump 410 and immediately after the line deflection 414.

The silencer devices 416 in 6 each show how the silencer devices 216 in 3 , a liquid chamber 418, a gas chamber 420 and a separation membrane 424.

The gas chambers 420 of the silencer devices 416 are connected via a gas line 430 to a gas supply device 432. In the example of 6 the gas chambers 420 of all shown silencer devices 416 are connected to the gas supply device 432 by means of a (branched) gas line 430.

In order to prevent acoustic coupling of the plurality of silencer devices 416 via the gas line 430, a plurality of sound absorption elements 434 are arranged within the gas line 430. The sound absorption elements 434 are 6 only schematically indicated. One, several or all of the sound absorption elements 434 in 6 is/are, for example, like the one in 4 shown sound absorption element 234.

By means of the sound absorption elements 434 arranged within the gas line 430, acoustic interference via the gas line 430 to the silencer device 416 and thus to the position-sensitive component 102, 102', 102" can be reduced or avoided.

Although the present invention has been described using exemplary embodiments, it is susceptible to numerous modifications. For example, the cooling device 200, 300, 400 can also be used in a DUV lithography system.

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

wafer

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

102, 102', 102"

position-sensitive component (mirror)

104

Coating

106

optically active surface

108

Substrat

110

Cooling line

112

coolant

114

Actuator device

116

Supporting frame

118

Actuator

120

Sensor device

122

laser beam

200

Cooling device

202

Cooling circuit

204

Cooling unit

206

coolant

208

Liquid line

210

pump

212

valve

214

redirection

216

Silencer device

218

liquid chamber

220

gas chamber

222

gas

224

Separation membrane

226

fluid space

228

neck section

230

gas pipeline

232

Gas supply facility

234

Sound absorption element

236

Absorber material

240

surface

242

surface

300

Cooling device

316

Silencer device

318

liquid chamber

320

gas chamber

330

gas pipeline

332

Gas supply facility

334

Sound absorption element

350

valve

352

hydraulic unit

354

pump

356

Gas reservoir

358

Control/regulating device

360

Sensor device

400

Cooling device

404

Cooling unit

408

Liquid line

410

pump

412

valve

414

redirection

416

Silencer device

418

liquid chamber

420

gas chamber

424

Separation membrane

430

gas pipeline

432

Gas supply facility

434

Sound absorption element

A

signal

B

signal

C

signal

M1

Mirror

M2

Mirror

M3

Mirror

M4

Mirror

M5

Mirror

M6

Mirror

PG

Gas pressure

S

Flow direction

Claims (15)

A cooling device (200) for cooling a position-sensitive component (102) of a lithography system (1), comprising: a liquid line (208) for transporting a cooling liquid (206), a silencer device (216) for dampening a pressure fluctuation of the cooling liquid (206), wherein the silencer device (216) has a liquid chamber (218) fluidly connected to the liquid line (208), a gas chamber (220) for receiving a gas (222), and an elastic separating membrane (224) separating the gas chamber (220) from the liquid chamber (218), a gas line (230) fluidly connected to the gas chamber (220), and a sound absorption element (234) arranged within the gas line (230). Cooling device according to Claim 1 , wherein the sound absorption element (234) comprises a gas-permeable, porous absorber material (236). Cooling device according to Claim 2 , wherein the porous absorber material (236) comprises a porous foam and/or a fibrous material. Cooling device according to one of the Claims 1 until 3 , wherein the sound absorption element (234) is attached to the gas line (230) and/or to an inner wall (242) of the gas line (230). Cooling device according to one of the Claims 1 until 4 , wherein the silencer device (216) comprises: a resonance absorber, a Helmholtz resonator, and/or a neck portion (228) which fluidly connects the liquid line (208) to the liquid chamber (218) of the silencer device (216). Cooling device according to one of the Claims 1 until 5 , comprising a plurality of silencer devices (416), each having a liquid chamber (418) fluidly connected to the liquid line (408), a gas chamber (420) and an elastic separating membrane (424) separating the gas chamber (420) from the liquid chamber (418), wherein the gas line (430) is fluidly connected to a plurality of gas chambers (420) of the plurality of silencer devices (416). Cooling device according to Claim 6 , wherein the sound absorption element (434) is arranged in a section of the gas line (230) which fluidly connects a gas chamber (420) of a first silencer device (416) and a gas chamber (420) of a second silencer device (416). Cooling device according to one of the Claims 1 until 7 , comprising a control and/or regulating device (358) for controlling and/or regulating a gas pressure (P _G ) of a gas (222) in the gas chamber (220) of the one or more silencer devices (216), wherein the control and/or regulating device (358) is designed to control and/or regulating a gas supply and/or a gas discharge into the gas chamber (220) or out of the gas chamber (220) of the one or more silencer devices (216). Cooling device according to one of the Claims 1 until 8 , comprising a sensor device (360) for detecting a gas pressure (P _G ) of a gas (222) in the gas chamber (220) of the one or more silencer devices (216). Cooling device according to one of the Claims 1 until 9 , wherein the silencer device (216) is arranged upstream of the position-sensitive component (102) with respect to a flow direction (S) of a cooling liquid (206) in the liquid line (208). Cooling device according to one of the Claims 1 until 10 , wherein a first silencer device (416) is arranged upstream of the position-sensitive component (102) with respect to a flow direction (S) of a cooling liquid (206) in the liquid line (408), and a second silencer device (416) is arranged downstream of the position-sensitive component (102) with respect to the flow direction (S). Cooling device according to Claim 10 or 11 , wherein a section of the liquid line (208) between the silencer device (216) and the position-sensitive component (102) is free of FIV sources (210, 212, 214), pumps (210), valves (212), line cross-sectional changes, line deflections (214) and/or line bends. Cooling device according to one of the Claims 1 until 12 , wherein the one or more sound damper devices (216) are each configured to dampen pressure fluctuations of the cooling liquid (206) in a frequency range of 1 Hz to 2 kHz, 1 Hz to 1 kHz, 1 to 800 Hz, 1 to 500 Hz, 1 to 400 Hz, 1 to 200 Hz, 1 to 100 Hz and/or 50 to 150 Hz. Cooling device according to one of the Claims 1 until 13 , wherein the sound absorption element (234) in the gas line (230) is adapted to dampen pressure fluctuations of the gas (222) in a frequency range of 1 Hz to 2 kHz, 1 Hz to 1 kHz, 1 to 800 Hz, 1 to 500 Hz, 1 to 400 Hz, 1 to 200 Hz, 1 to 100 Hz and/or 50 to 150 Hz. Lithography system (1) with a position-sensitive component (102) and a cooling device (200) according to one of the Claims 1 until 14 for cooling the position-sensitive component (102).

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