CN116830003A - Optical system and method for operating an optical system - Google Patents
Optical system and method for operating an optical system Download PDFInfo
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- CN116830003A CN116830003A CN202180088266.4A CN202180088266A CN116830003A CN 116830003 A CN116830003 A CN 116830003A CN 202180088266 A CN202180088266 A CN 202180088266A CN 116830003 A CN116830003 A CN 116830003A
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- 230000003287 optical effect Effects 0.000 title claims abstract description 61
- 238000000034 method Methods 0.000 title claims abstract description 16
- 239000000758 substrate Substances 0.000 claims abstract description 83
- 238000001816 cooling Methods 0.000 claims abstract description 62
- 239000012809 cooling fluid Substances 0.000 claims abstract description 52
- 239000000463 material Substances 0.000 claims description 31
- 238000010438 heat treatment Methods 0.000 claims description 24
- 238000005286 illumination Methods 0.000 claims description 12
- 230000033228 biological regulation Effects 0.000 claims description 4
- 230000005670 electromagnetic radiation Effects 0.000 claims description 4
- 230000001105 regulatory effect Effects 0.000 claims description 4
- 230000005855 radiation Effects 0.000 description 17
- 230000003044 adaptive effect Effects 0.000 description 9
- 230000000694 effects Effects 0.000 description 7
- 238000006073 displacement reaction Methods 0.000 description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 4
- 230000004075 alteration Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000003384 imaging method Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 238000001393 microlithography Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000006735 deficit Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000003574 free electron Substances 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 229920002120 photoresistant polymer Polymers 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 230000011218 segmentation Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
- G03F7/70858—Environment aspects, e.g. pressure of beam-path gas, temperature
- G03F7/70883—Environment aspects, e.g. pressure of beam-path gas, temperature of optical system
- G03F7/70891—Temperature
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/18—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors
- G02B7/181—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation
- G02B7/1815—Mountings, adjusting means, or light-tight connections, for optical elements for prisms; for mirrors with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation with cooling or heating systems
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- Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
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- Life Sciences & Earth Sciences (AREA)
- Atmospheric Sciences (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Epidemiology (AREA)
- Public Health (AREA)
- Lenses (AREA)
- Optical Elements Other Than Lenses (AREA)
- Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
- Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
Abstract
The present application relates to an optical system and a method for operating an optical system, in particular an optical system in a microlithographic projection exposure apparatus. According to one aspect of the present application, an optical system includes: at least one mirror (100, 200, 300, 400, 500, 600) having an optically active surface (101, 201, 301, 401, 501, 601) and a mirror substrate (110, 210, 310, 410, 510, 610); a plurality of temperature adjustment regions (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) arranged in the mirror substrate; and a temperature adjustment device (150, 250, 350, 450, 550, 650) by which the temperature present in each temperature adjustment zone can be adjusted independently of one another, the temperature adjustment zones being arranged in at least two planes at different distances from the optically effective surface, and the temperature adjustment zones in the at least two planes being configured as cooling channels through which cooling fluid at a variably adjustable cooling fluid temperature can flow independently of one another.
Description
Cross Reference to Related Applications
The present application claims priority from German patent application DE 10 2021 200 788.0 filed on 1 month 28 of 2021 and German patent application DE 10 2021 207 580.0 filed on 7 month 16 of 2021. The content of said german application is incorporated by reference into the text of the present application.
Technical Field
The present application relates to an optical system and a method for operating an optical system, in particular in a microlithographic projection exposure apparatus.
Background
Microlithography is used for the production of microstructured components such as integrated circuits or liquid crystal displays. The microlithography process is carried out in an apparatus known as a projection exposure apparatus, which comprises an illumination device and a projection lens. Here, an image of a mask (=reticle) illuminated by the illumination device is projected by a projection lens onto a substrate (for example a silicon wafer) coated with a photosensitive layer (photoresist) and arranged in the image plane of the projection lens, so that the mask structure is transferred onto the photosensitive coating of the substrate.
In projection lenses designed for the EUV range, namely: at wavelengths of, for example, about 13nm or about 7nm, mirrors are used as optical components of the imaging process due to the lack of suitable light transmissive refractive materials available.
One problem that arises in practice is that, in particular due to absorption of the radiation emitted by the EUV light source, the EUV mirror heats up and undergoes a related thermal expansion or deformation, which in turn can adversely affect the imaging properties of the optical system.
Various methods are known to avoid surface deformations and the optical aberrations associated therewith caused by the heat input to the EUV mirror. In particular, it is known to use materials with ultra-low thermal expansion ("ultra-low expansion materials"), such as the one sold by corning inc (corning inc.) under the name ULE TM As a mirror substrate material, and a so-called zero crossing temperature is set in a region near the optically effective surface. At the zero crossing temperature (e.g. for ULE TM For example, the zero crossing temperature is located at approximately θ=30℃), the thermal expansion coefficient has a zero crossing in its temperature dependence, in the vicinity of which no thermal expansion or only a negligible thermal expansion of the mirror substrate material occurs.
Other possible ways of avoiding surface deformations caused by heat input to the EUV mirror include active direct cooling or the use of heating means, for example based on infrared radiation. With such a heating device, active mirror heating may occur in a relatively low absorption phase of the EUV use radiation, which active mirror heating decreases correspondingly with increasing absorption of the EUV use radiation. In this regard, one or more temperature sensors attached to the EUV mirror are typically used to determine the current heating state of the EUV mirror. Active heating of the mirror may in particular be performed with the aim of maintaining the average mirror temperature around the above zero crossing temperature.
However, in this respect, other problems occur in practice, in particular due to the spatial distribution of the zero crossing temperature in the mirror substrate material and to the undesired heat input to the optical system by the heating means used. Furthermore, the temperatures measured at the locations of the respective temperature sensors deviate from the final relevant temperature (e.g. the temperature at the optically effective surface of the EUV mirror or the average mirror temperature), with the result that the adjustment of the heating power on this basis is ultimately insufficient to avoid thermally induced surface deformations or optical aberrations.
Disclosure of Invention
It is an object of the present application to provide an optical system and a method for operating an optical system which are capable of effectively avoiding thermally induced deformations while at the same time at least alleviating the above-mentioned problems.
This object is achieved according to the features of the optional independent patent claims.
According to one aspect of the present application, an optical system includes:
at least one mirror having an optically active surface and a mirror substrate, wherein a plurality of temperature control zones are disposed in the mirror substrate; and
temperature control means via which the temperatures respectively present in the temperature control zones can be set independently of each other;
wherein the temperature control zones are arranged in at least two planes at different distances from the optically effective surface; and is also provided with
Wherein the temperature control zones in the at least two planes are in the form of cooling channels through which cooling fluid having a variably settable cooling fluid temperature can flow independently of one another.
The application is based in particular on the following concepts: an adaptive mirror with a selectively deformable optically active surface is produced by providing temperature control zones which are located at different distances from the optically active surface and whose temperatures can be set independently of one another, wherein the following facts are exploited in a manner analogous to the so-called "bimetallic effect": the different thermal expansions in the different planes of the temperature control zone are eventually converted into surface deformations of the mirror.
In other words, the present application relates to the following principle: the surface deformations of the associated mirror are actively generated during the setting of the temperature differences in at least two different planes in a selectively spatially resolved manner, which differ from each other in terms of their distance from the optically active surface, and in this connection, in particular, an additional degree of freedom is also provided when setting the wavefront properties of the optical system comprising the mirror.
Since the temperatures of the different temperature control zones can be set in a spatially variable manner at this time, or since the temperatures of the individual temperature control zones can be set independently of one another, the abovementioned degrees of freedom can be achieved not only in the different planes but also in the same plane, in particular also in the form of local degrees of freedom (which is particularly useful in setting the wavefront properties of the optical system). For this purpose, the respective temperatures in the temperature control zones assigned to the different planes are appropriately selected so that they may approximately have the following effects: due to the local mechanical stress, the effective surface deformation eventually occurs only at one lateral position on the optically effective surface, while no such deformation occurs in the remaining area of the optically effective surface.
In general, the principle utilized according to the application makes it possible to achieve a particularly precise setting of the deformation profile in the adaptive mirror, and also to correct disturbances in the optical properties of the relevant mirror or of the optical system comprising the mirror, which disturbances have a relatively high frequency in terms of part. In particular, such disturbances with low spatial wavelengths (e.g. in the order of 1 mm) may be disturbances caused by the spatial distribution of the zero crossing temperature in the mirror substrate material.
According to one embodiment, the optical system further comprises an adjustment unit for time-variable adjustment of the temperatures respectively set by the temperature control means in the temperature control zones.
According to one embodiment, the optical system further comprises means for determining the cooling power output when the cooling fluid flows through the cooling channel.
According to one embodiment, based on the adjustment, the determination of the respective current heating state of the mirror is performed in dependence on the cooling power output by the cooling fluid when flowing through the cooling channel.
In this case, the application is based on the following further considerations: given a known flow rate and a known heat transfer coefficient in the region of the respective cooling channel wall, the power output of the cooling fluid flowing in the cooling channel ultimately constitutes a measure of the temperature gradient that is present on average in the mirror substrate material and thus of the current heating state of the mirror.
For cooling fluid flowing through cooling channelsThe cooling power output by the cooling fluid is suitable for:
P Cool ＝α·A·ΔT (1)
where α denotes the heat transfer coefficient in the region of the respective cooling channel walls, a denotes the contact surface of the mirror substrate with respect to the mirror substrate material, and Δt denotes the temperature difference between the mirror substrate material and the cooling fluid. The temperature difference between the inlet and outlet of the relevant cooling channel is created by integrating the local cooling power along the cooling section and dividing by the heat capacity C of the cooling fluid:
T Inlet -T Outlet ≈-∫dlP Cool (l)/(C·L) (2)
where L denotes the position along the cooling section and L denotes the total length of the cooling section. The flow rate can be used to determine the mass flow per unit time, whereby the value of C can be determined using the specific heat capacity of the cooling fluid. Accordingly, the average temperature difference Δt between the mirror substrate material and the cooling fluid can be determined, whereby in turn an estimate of the temperature distribution in the mirror substrate material can be obtained.
Based on the cooling power output by the cooling fluid as it passes through the cooling channel, the temperature field present in the mirror substrate material can be determined with relatively high accuracy, so that the adjustment of the temperature respectively set by the temperature control means can also be performed with higher accuracy based on this temperature information (e.g. compared to conventional ways of determining the heating state of the mirror based on a temperature sensor or a wavefront sensor in an optical system located at the back of the mirror). In this connection, it is advantageous according to the application to determine the heating state of the mirror on the basis of the power output of the cooling fluid, in particular when the mirror substrate material exhibits a temperature-dependent nonlinear distribution of deformations, since then the absolute knowledge of the respective current mirror temperature is also relevant.
The above-described concept of determining the current heating state of the mirror on the basis of the cooling power output when the cooling fluid flows through the cooling channels is also advantageous, irrespective of the above-described arrangement principle of the temperature control zones in different planes within the mirror substrate.
Accordingly, the present application also relates to an optical system comprising:
at least one mirror having an optically active surface and a mirror substrate, wherein a plurality of temperature control zones are arranged in the mirror substrate, wherein the temperature control zones are in the form of cooling channels through which a cooling fluid having a variable cooling fluid temperature can flow independently of one another;
means for determining a cooling power output when the cooling fluid flows through the cooling channel; and
and a regulating unit for the time-variable regulation of the temperatures respectively set in the temperature control zones by the temperature control device, wherein, based on this regulation, a determination of the respective current heating state of the mirror is carried out as a function of the determined cooling power output when the cooling fluid flows through the cooling channel.
According to one embodiment, the mirror substrate has a first mirror substrate portion made of a first mirror substrate material and at least one second mirror substrate portion arranged on a side of the first mirror substrate portion facing away from the optically active surface, and the second mirror substrate portion is made of a second mirror substrate material different from the first mirror substrate material.
According to one embodiment, two planes with temperature control zones are assigned to different mirror substrate portions.
According to one embodiment, the average coefficient of thermal expansion of the first mirror substrate material is lower than the average coefficient of thermal expansion of the second mirror substrate material.
In the above configuration, the present application takes advantage of the fact that: for a temperature control zone in the mirror substrate at a relatively large depth with respect to the optically active surface, it is absolutely desirable that its thermal expansion is larger than that of the temperature control zone closer to the optically active surface, so that a possibly more pronounced effect is achieved in terms of the desired deformation of the optically active surface in a manner similar to the so-called bimetallic effect. Furthermore, this configuration allows for a relatively inexpensive (e.g., with ULE TM Compared with the prior art) (e.g. quartz glass, siO) 2 ) The mirror substrate is partially fabricated.
According to one embodiment, a respective plurality of temperature control zones is arranged in at least one of the two planes, wherein the temperatures of the temperature control zones located in the respective planes can be set independently of each other.
According to one embodiment, the temperature control device has a plurality of peltier elements assigned to the respective temperature control zones.
According to one embodiment, the temperature control device has a plurality of radiant heaters assigned to respective temperature control zones.
According to one embodiment, the mirror is designed for an operating wavelength of less than 30nm, in particular less than 15 nm.
According to one embodiment, the optical system is a projection lens or an illumination device of a microlithographic projection exposure apparatus.
The application further relates to a method for operating an optical system, wherein the optical system comprises at least one mirror having an optically active surface and a mirror substrate, wherein a plurality of temperature zones are arranged in at least two planes in the mirror substrate at different distances from the optically active surface, wherein the temperatures respectively present in the temperature control zones are set independently of one another.
In this regard, according to one aspect, the setting of the temperature in the temperature control zone is performed such that the deformation of the optically effective surface caused by the different thermal expansions of the temperature control zones belonging to different planes corresponds to the desired deformation.
According to another aspect, the setting of the temperature in the temperature control zone is performed such that thermally induced deformations of the mirror associated with the application of electromagnetic radiation to the optically effective surface are at least partially compensated for by thermal expansion of the temperature control zone.
According to one embodiment, the temperatures respectively set by the temperature control means in the temperature control zones are adjusted in a time-variable manner.
According to one embodiment, the temperature control zone is in the form of a cooling channel through which a cooling fluid having a variably settable cooling fluid temperature can flow independently of one another.
According to one embodiment, based on the adjustment, the determination of the respective current heating state of the mirror is performed in dependence on the cooling power output when the cooling fluid flows through the cooling channel.
The application further relates to a method for operating an optical system, wherein the optical system comprises at least one mirror having an optically active surface and a mirror substrate, wherein a plurality of temperature control areas are arranged in the mirror substrate, which temperature control areas are in the form of cooling channels through which a cooling fluid having a cooling fluid temperature that can be set variably can flow independently of one another, wherein the temperatures respectively set in the temperature control areas are adjusted in a time-variable manner, and wherein, based on the adjustment, a determination of the respective current heating state of the mirror is performed as a function of a determination of the cooling power output when the cooling fluid flows through the cooling channels.
Further configurations of the application are evident from the description and the dependent claims.
The application will be explained in more detail below on the basis of exemplary embodiments shown in the drawings
Drawings
In the accompanying drawings:
FIG. 1 shows a schematic diagram for illustrating a possible structure of a mirror according to one embodiment of the present application;
FIGS. 2-6 show schematic diagrams for illustrating possible configurations of mirrors according to other embodiments of the application; and is also provided with
Fig. 7 shows a schematic diagram of a possible structure of a microlithographic projection exposure apparatus designed for operation in EUV.
Detailed Description
Fig. 7 shows, firstly, schematically a meridional section of a possible structure of a microlithographic projection exposure apparatus designed for operation in EUV.
According to fig. 7, the projection exposure apparatus 1 comprises an illumination device 2 and a projection lens 10. An embodiment of the illumination device 2 of the projection exposure apparatus 1 has, in addition to the light source or radiation source 3, an illumination optical unit 4 for illuminating an object field 5 in an object plane 6. In alternative embodiments, the light source 3 may also be provided as a module separate from the rest of the lighting device. In this case, the lighting device does not comprise a light source 3.
The reticle 7 arranged in the object field 5 is exposed here. The reticle 7 is held by a reticle holder 8. The reticle carrier 8 can be displaced by a reticle displacement drive 9, in particular in the scanning direction. For illustration purposes, a Cartesian xyz coordinate system is shown in FIG. 7. The x-direction extends perpendicular to the plane of the drawing. The y-direction extends horizontally and the z-direction extends vertically. The scanning direction extends along the y-direction in fig. 7. The z-direction extends perpendicular to the object plane 6.
The projection lens 10 is used to image the object field 5 into an image field 11 in an image plane 12. The structures on the reticle 7 are imaged onto a photosensitive layer of a wafer 13, the wafer 13 being arranged in the region of the image field 11 in the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer carrier 14 is displaced by a wafer displacement drive 15, in particular in the y-direction. The displacement of the reticle 7 by the reticle displacement drive 9 and the displacement of the wafer 13 by the wafer displacement drive 15 can be carried out synchronously with one another.
The radiation source 3 is an EUV radiation source. The radiation source 3 emits in particular EUV radiation, which is also referred to as usage radiation or illumination radiation in the following. In particular, radiation is used having a wavelength in the range between 5nm and 30 nm. The radiation source 3 may be, for example, a plasma source, a synchrotron-based radiation source or a Free Electron Laser (FEL). Illumination radiation 16 emitted from the radiation source 3 is focused by a collector 17 and propagates into the illumination optical unit 4 through an intermediate focus in an intermediate focus plane 18. The illumination optical unit 4 includes a deflection mirror 19, a first facet mirror 20 (with a schematically shown facet 21) and a second facet mirror 22 (with a schematically shown facet 23) arranged downstream of the deflection mirror in the optical path.
The projection lens 10 comprises a plurality of mirrors Mi (i=1, 2, …), which are numbered in sequence according to their arrangement in the light path of the projection exposure apparatus 1. In the example shown in fig. 7, the projection lens 10 includes six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or any other number of mirrors Mi are equally possible. The penultimate mirror M5 and the last mirror M6 each have a through-opening for the illumination radiation 16. The projection lens 10 is a doubly-blocked optical unit. The image-side numerical aperture of the projection lens 10 may be greater than 0.5 or greater than 0.6, for example, 0.7 or 0.75.
During operation of the microlithographic projection exposure apparatus 1, electromagnetic radiation incident on the optically effective surface of the mirror is partially absorbed and, as explained in the introduction, leads to heating and an associated thermal expansion or deformation, which in turn can lead to impairment of the imaging properties of the optical system. The concept according to the application can be applied particularly advantageously to any desired mirror in the microlithographic projection exposure apparatus 1 of fig. 7. This may be implemented to avoid or compensate for thermally induced deformations of the associated mirror itself (e.g. to compensate for spatial distribution of zero crossing temperatures), or to provide an additional degree of freedom in setting the wavefront properties of the entire optical system, that is to say without or with the corrective action achieved by the associated mirror.
The application is not limited to use in projection exposure apparatuses designed for operation under EUV. In particular, the application can also be used advantageously for projection exposure apparatuses designed for operation at DUVs (i.e. wavelengths of less than 250nm, in particular less than 200 nm), or also for other optical systems.
Fig. 1 shows only one possible mirror 100 according to the applicationSchematic of the examples. The mirror 100 has a mirror substrate 110 (e.g., made of ULE TM Made) and a reflective layer system 120 (e.g., in the form of a multi-layer coating stack of molybdenum (Mo) -silicon (Si). Within the mirror substrate 110, there are a plurality of temperature control zones 131-136 and 141-146 arranged in two planes at different distances from the optically active surface 101. In certain exemplary embodiments, the temperature control zones 131-136 and 141-146 are in the form of cooling channels through which cooling fluid having a variably settable cooling fluid temperature may flow independently of one another.
"150" denotes a temperature control device by means of which the temperatures respectively present in the temperature control zones 131-136, 141-146 can be set independently of one another. For example only, the temperature control device 150 may have a plurality of peltier elements assigned to respective temperature control zones.
Although the present application in the exemplary embodiment of fig. 1 is implemented through the corresponding cooling channels through which the cooling fluid may flow, the present application is not limited thereto. Rather, in other embodiments, the target selective setting of different temperatures in different temperature control zones may also be performed in other suitable ways, for example by means of radiant heaters with different focal depths or by means of resistive heating elements.
Setting different temperatures in the temperature control zones 131-136 and 141-146, respectively, at first different distances from the optically active surface 101 results in a deformation of the optically active surface 101 due to different thermal expansions of the mirror substrate material in the relevant plane, similar to the so-called bimetallic effect. This in turn can be used to provide an additional degree of freedom in setting the wavefront characteristics of an optical system comprising the mirror 100, for example the projection exposure apparatus 1 in fig. 7.
For one part, the temperature setting according to the application may be performed in a temperature control zone, thereby setting the desired deformation of the optically active surface 101 (e.g. in order to compensate for disturbances or aberrations present elsewhere in the optical system). Alternatively, the temperature setting may also be performed so as to compensate for thermally induced deformations of the mirror 100 itself. In the latter case, the temperature control zones 141-146 can thus be used in particular to avoid expansion or deformation of the mirror 100 in connection with the (cooling) operation of the temperature control zones 131-136. Thus, with this approach, temperature control zones 131-136 are used to release heat generated by absorption of electromagnetic radiation incident on optically active surface 101, while temperature control zones 141-146 are used to compensate for otherwise induced deformations of temperature control zones 131-136 by the flow of cooling fluid.
Fig. 2 shows another embodiment of an adaptive mirror 200, wherein similar or functionally substantially identical components compared to fig. 1 are denoted by reference numerals increased by "100". The embodiment of fig. 2 differs from the embodiment of fig. 1 in that the mirror substrate 210 is composed of different mirror substrate portions 210a, 210b, wherein the mirror substrate portion 210a arranged closer to the optically active surface 201 is made of a mirror substrate material having a relatively low average coefficient of thermal expansion. In certain exemplary embodiments, the mirror substrate material of the first mirror substrate portion 210a may be ULE TM While the mirror substrate material of the second mirror substrate portion 210b may be quartz glass (SiO 2 )。
Fig. 3 shows another embodiment of an adaptive mirror 300 according to the application, wherein components similar or functionally substantially identical to fig. 2 are in turn denoted by reference numerals increased by "100". The exemplary embodiment of fig. 3 differs from that of fig. 2 in that the mirror substrate 310 is composed of three different mirror substrate parts 310a, 310b and 310c, wherein the walls of the respective cooling channels acting as temperature control zones 331-336, 341-346 have been introduced into these mirror substrate parts in a manner that is advantageous from a manufacturing technology point of view. In particular, a first mirror substrate portion 310a (which in turn may be formed by ULE TM Manufactured) acts as a top portion of a cooling channel for the temperature control regions 331-336, the second mirror substrate portion 310b (which may be made of, for example, quartz glass (SiO) 2 ) Manufactured) acts as the bottom of the cooling channels forming temperature control regions 341-346. The third mirror substrate portion 310c is arranged between the first and second mirror substrate portions 310a and 310b while functioning as a formation temperature control regionBottom of cooling channels 331-336 and top of cooling channels forming temperature control zones 341-346, and may be defined by the ULE according to specific conditions TM Or quartz glass (SiO) 2 ) Is prepared.
Use of a relative ULE on the side of the mirror substrate portion 210b in the embodiment of fig. 2 or the mirror substrate portion 310b or 310c in the embodiment of fig. 3 TM Materials having a relatively high coefficient of thermal expansion are advantageous because, in order to achieve a significant deformation effect in the adaptive mirror according to the application, it is clearly desirable to have a greater thermal expansion in the region of these mirror substrate portions (relative to the first mirror substrate portions 210a and 310a, respectively, which are closer to the optically active surface). At the same time, in certain areas, the adaptive mirror can thus be made of a relatively inexpensive material (relative to the ULE TM ) Manufacturing.
Fig. 4 shows another embodiment of an adaptive mirror 400, wherein similar or functionally substantially identical components compared to fig. 1 are denoted by reference numerals increased by "300". The embodiment of fig. 4 differs from the embodiment of fig. 1 in that instead of the temperature control zones 131-136, there is only a single temperature control zone 431 (which is continuous or not divided into a plurality of separate temperature control zones) in the relevant plane within the mirror substrate 410. In the arrangement according to fig. 4, with respect to this undivided temperature control zone 431, the spatial resolution in the transverse direction achievable by the division is deliberately omitted in order to in turn reduce the total number of cooling fluid ports required, thereby firstly reducing the structural outlay and secondly also preventing the risk of sealing defects or leaks occurring in the region of the cooling channels.
Fig. 5 shows another embodiment of an adaptive mirror 500, wherein similar or functionally substantially identical components compared to fig. 1 are denoted by reference numerals increased by "400". The embodiment of fig. 5 differs from the embodiment of fig. 1 in that instead of arranging the temperature control zones 141-146 in a plane at a relatively large distance from the optically active surface 101 according to the embodiment of fig. 1, only a single temperature control zone 541 (which is continuous or not divided into a plurality of separate temperature control zones) is provided. In other words, in the embodiment according to fig. 5, the segmentation or lateral spatial resolution is not omitted in a plane closer to the optically active surface, but in a plane further away from the optically active surface or a temperature control zone there, compared to the embodiment of fig. 4. With this configuration, reducing the total number of required cooling fluid ports also has the effect of simplifying the structure from a design perspective and reducing the risk of leakage.
Fig. 6 shows another embodiment of an adaptive mirror 600, wherein similar or functionally substantially identical components compared to fig. 1 are denoted by reference numerals increased by "500". The embodiment of fig. 6 differs from that of fig. 1 in that the temperature control zones 131-136 and 141-146 lying in two planes according to fig. 1 are replaced by a single temperature control zone 631 and 641, respectively, which is continuous and not divided into a plurality of separate temperature control zones. In this embodiment, the split or lateral resolution in the two planes of the region with temperature control zones 631, 641 is omitted so that the number of cooling fluid ports is minimized.
In all of the above embodiments, water or any other suitable cooling fluid as desired may be used as the cooling fluid.
In a further embodiment, the concept of a cooling channel or temperature control zone according to the application can also be used in combination with the local heating of the optically active surface of the associated mirror (e.g. by means of a radiant heater), through which cooling fluid flows independently of each other.
In all of the embodiments described above on the basis of fig. 1-6, the temperatures respectively set in the temperature control zones can be adjusted in a time-variable manner. In this connection, on the basis of this adjustment, it is also possible in particular and advantageously to determine the current heating state of the respective mirror as a function of the determination of the cooling power output when the cooling fluid flows through the cooling channel. To this end, for example, temperature sensors at the inlet and outlet may be used to measure the temperature change of the cooling fluid flowing through the cooling channels, and then, given a known flow rate and a known heat transfer coefficient at the walls of the respective cooling channels, conclusions can be drawn about the temperature gradient present in the mirror substrate material.
While the application has been described in terms of specific embodiments, many variations and alternative embodiments will be apparent to those skilled in the art, such as by combinations and/or permutations of the features of the various embodiments. It will thus be apparent to those skilled in the art that such variations and alternative embodiments are encompassed by the present application, and that the scope of the application is limited only by the meaning of the appended patent claims and their equivalents.
Claims (19)
1. An optical system, comprising:
at least one mirror (100, 200, 300, 400, 500, 600) having an optically active surface (101, 201, 301, 401, 501, 601) and a mirror substrate (110, 210, 310, 410, 510, 610), wherein a plurality of temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) are arranged in the mirror substrate; and
temperature control means (150, 250, 350, 450, 550, 650) via which the temperatures respectively present in the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) can be set independently of each other;
wherein the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) are arranged in at least two planes at different distances from the optically active surface (101, 201, 301, 401, 501, 601); and is also provided with
Wherein the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) in the at least two planes are in the form of cooling channels through which cooling fluid having a variably settable cooling fluid temperature can flow independently of each other.
2. An optical system according to claim 1, further comprising an adjustment unit for the time-variable adjustment of the temperatures set in the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) by means of the temperature control means.
3. An optical system according to claim 1 or 2, further comprising means for determining the cooling power output when the cooling fluid flows through the cooling channel.
4. An optical system according to claim 2 or 3, characterized in that, based on the adjustment, the respective current heating state of the mirror is determined from the cooling power output when the cooling fluid flows through the cooling channel.
5. An optical system, comprising:
at least one mirror (100, 200, 300, 400, 500, 600) having an optically active surface (101, 201, 301, 401, 501, 601) and a mirror substrate (110, 210, 310, 410, 510, 610), wherein a plurality of temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) are arranged in the mirror substrate, wherein the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) are in the form of cooling channels through which a cooling fluid having a variable cooling fluid temperature can flow independently of each other;
means for determining a cooling power output when the cooling fluid flows through the cooling channel; and
and a regulating unit for the time-variable regulation of the temperatures respectively set in the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) by means of the temperature control device, wherein, on the basis of the regulation, the respective current heating state of the mirror is determined as a function of the determined cooling power output when the cooling fluid flows through the cooling channel.
6. The optical system according to one of the preceding claims, characterized in that the mirror substrate (210, 310) has a first mirror substrate portion (210 a, 310 a) made of a first mirror substrate material and at least one second mirror substrate portion (210 b, 310 b) arranged on a side of the first mirror substrate portion (210 a, 310 a) facing away from the optically effective surface (201, 301), and the second mirror substrate portion is made of a second mirror substrate material different from the first mirror substrate material.
7. The optical system according to claim 6, characterized in that the two planes of the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346) are assigned to different mirror substrate portions (210 a, 210b, 310a, 310 b).
8. The optical system of claim 6 or 7, wherein the first mirror substrate material has a lower average coefficient of thermal expansion than the second mirror substrate material.
9. Optical system according to one of the preceding claims, characterized in that a respective plurality of temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 441-446, 531-536) are arranged in at least one of the two planes, wherein the temperatures of the temperature control zones located in the respective planes can be set independently of each other.
10. Optical system according to one of the preceding claims, characterized in that the temperature control device has a plurality of peltier elements assigned to the respective temperature control zone (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641).
11. Optical system according to one of the preceding claims, characterized in that the temperature control device has a plurality of radiant heaters assigned to the respective temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641).
12. Optical system according to one of the preceding claims, characterized in that the mirror (100, 200, 300, 400, 500, 600) is designed for an operating wavelength of less than 30nm, in particular less than 15 nm.
13. Optical system according to one of the preceding claims, characterized in that the optical system is a projection lens or an illumination device of a microlithographic projection exposure apparatus (1).
14. A method for operating an optical system, wherein the optical system comprises at least one mirror (100, 200, 300, 400, 500, 600) having an optically active surface (101, 201, 301, 401, 501, 601) and a mirror substrate (110, 210, 310, 410, 510, 610), wherein a plurality of temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) are arranged in at least two planes of the mirror substrate (110, 210, 310, 410, 510, 610) at different distances from the optically active surface,
wherein the temperatures respectively present in the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) are set independently of each other,
wherein the setting of the temperature in the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) is performed such that deformations of the optically effective surface (101, 201, 301, 401, 501, 601) caused by different thermal expansions of the temperature control zones belonging to different planes correspond to desired deformations.
15. A method for operating an optical system, wherein the optical system comprises at least one mirror (100, 200, 300, 400, 500, 600) having an optically active surface (101, 201, 301, 401, 501, 601) and a mirror substrate (110, 210, 310, 410, 510, 610), wherein a plurality of temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) are arranged in at least two planes of the mirror substrate (110, 210, 310, 410, 510, 610) at different distances from the optically active surface,
wherein the setting of the temperature in the temperature control zone (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) is performed such that the thermally induced deformations of the mirror associated with electromagnetic radiation applied to the optically active surface (101, 201, 301, 401, 501, 601) are at least partially compensated by the thermal expansion of the temperature control zone (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641).
16. A method according to claim 14 or 15, characterized in that the temperatures set in the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) respectively by the temperature control means are regulated in a time-variable manner.
17. A method according to any one of claims 14-16, characterized in that the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) are in the form of cooling channels through which cooling fluid having a variably settable cooling fluid temperature can flow independently of each other.
18. Method according to claims 16 and 17, characterized in that, based on the adjustment, the determination of the respective current heating state of the mirror is performed from the determination of the cooling power output when the cooling fluid flows through the cooling channel.
19. A method for operating an optical system, wherein the optical system comprises at least one mirror (100, 200, 300, 400, 500, 600) having an optically active surface (101, 201, 301, 401, 501, 601) and a mirror substrate (110, 210, 310, 410, 510, 610), wherein a plurality of temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) are arranged in the mirror substrate (110, 210, 310, 410, 510, 610) in the form of cooling channels through which a cooling fluid having a variably settable cooling fluid temperature can flow independently of one another,
wherein the temperatures respectively set in the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) are regulated in a time-variable manner and
wherein based on the adjustment, a determination of a respective current heating state of the mirror is performed from a determination of a cooling power output when the cooling fluid flows through the cooling channel.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102021200788.0 | 2021-01-28 | ||
| DE102021207580.0 | 2021-07-16 | ||
| DE102021207580.0A DE102021207580A1 (en) | 2021-07-16 | 2021-07-16 | Optical system and method for operating an optical system |
| PCT/EP2021/083360 WO2022161659A1 (en) | 2021-01-28 | 2021-11-29 | Optical system, and method for operating an optical system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116830003A true CN116830003A (en) | 2023-09-29 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202180088266.4A Pending CN116830003A (en) | 2021-01-28 | 2021-11-29 | Optical system and method for operating an optical system |
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| Country | Link |
|---|---|
| CN (1) | CN116830003A (en) |
| DE (1) | DE102021207580A1 (en) |
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2021
- 2021-07-16 DE DE102021207580.0A patent/DE102021207580A1/en active Pending
- 2021-11-29 CN CN202180088266.4A patent/CN116830003A/en active Pending
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| DE102021207580A1 (en) | 2023-01-19 |
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