Optical system and method of operating the optical system

Abstract

The present invention relates particularly to an optical system in a microlithographic projection exposure apparatus and a method for operating the optical system. According to one aspect of the present invention, the optical system comprises at least one mirror (100, 200, 300, 400, 500, 600) having an optically effective surface (101, 201, 301, 401, 501, 601) and a mirror substrate (110, 210, 310, 410, 510, 610), a plurality of temperature-controlled zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) arranged within the mirror substrate, and a temperature-controlled device (150, 250, 350, 450, 550, It includes 650), and the temperature in each temperature-controlled zone can be controlled independently of each other by the temperature-controlled device, and the temperature-controlled zones are arranged in at least two planes at different distances from the optically effective surface, and the temperature-controlled zones within the at least two planes are composed of cooling channels through which a cooling fluid of a variable, adjustable cooling fluid temperature can flow independently of each other.

Description

Technology Field

[0001] This application claims priority to German patent application DE 10 2021 200 788.0 filed on January 28, 2021, and German patent application DE 10 2021 207 580.0 filed on July 16, 2021. The contents of the said German applications are incorporated by reference into this application.

[0002] The present invention relates particularly to an optical system in a microlithographic projection exposure device and a method for operating the optical system. Background Technology

[0003] Microlithography is used to produce microstructured components, such as integrated circuits or LCDs. The microlithography process is performed in a device referred to as a projection exposure apparatus, which includes an illumination device and a projection lens. An image of a mask (=reticle) illuminated by the illumination device is projected by the projection lens onto a substrate (e.g., a silicon wafer) coated with a photosensitive layer (photoresist) to transfer the mask structure onto the photosensitive coating of the substrate, and is aligned within the image plane of the projection lens.

[0004] For projection lenses designed for the EUV range, that is, for example at a wavelength of approximately 13 nm or approximately 7 nm, mirrors are used as optical components for the imaging process due to the lack of availability of suitable light-transmitting refractive materials.

[0005] One problem that actually occurs is that, among other reasons, as a result of the absorption of radiation emitted by the EUV light source, the EUV mirror heats up and undergoes associated thermal expansion or deformation, which can subsequently have an adverse effect on the imaging characteristics of the optical system.

[0006] Various approaches are known to avoid surface deformation and associated optical aberrations caused by thermal input into EUV mirrors. It is particularly known to use a material having ultra-low thermal expansion ("ultra-low expansion material"), for example, titanium quartz glass sold by Corning Inc. under the designation ULE™, as a mirror substrate material, and to set a known zero-crossing temperature within the region near the optically effective surface. For example, for ULE™, approximately At this zero-crossing temperature of 30°C, the coefficient of thermal expansion has a zero-crossing point of the mirror substrate material in its temperature dependence, and near there, no thermal expansion occurs or only negligible thermal expansion occurs.

[0007] Other possible approaches to avoid surface deformation caused by thermal input to the EUV mirror include active direct cooling or the use of a heating array based, for example, on infrared radiation. With such a heating array, active heating of the mirror can be performed at a phase where the absorption of EUV radiation is relatively low, and said active heating of the mirror is correspondingly reduced as the absorption of EUV radiation increases. In this regard, the current heating state of the EUV mirror is typically checked using one or more temperature sensors attached to the EUV mirror. Active heating of the mirror can be performed, in particular, to maintain the average mirror temperature close to the aforementioned zero-crossing temperature.

[0008] However, in this regard, other problems actually arise, primarily due to the spatial distribution of zero-crossing temperatures within the mirror substrate material and the undesirable thermal input into the optical system by the heating array used. Furthermore, the temperature measured at each location of the temperature sensor ultimately deviates from the relevant temperature (e.g., the temperature at the optically effective surface of the EUV mirror or the average mirror temperature), and consequently, the control of heating power based on this results in only insufficient avoidance of thermally induced surface deformation or optical aberrations. means of solving the problem

[0009] The object of the present invention is to provide an optical system and a method for operating the optical system that enables effective avoidance of thermally induced deformation while at least mitigating the problems described above.

[0010] This objective is achieved according to the features of alternative independent patent claims.

[0011] According to one aspect of the present invention, the optical system is:

[0012] - At least one mirror having an optically effective surface and a mirror substrate, wherein a plurality of temperature control zones are arranged within the mirror substrate; and

[0013] - Includes a temperature control device that enables temperatures existing in each temperature control zone to be set independently of each other;

[0014] - The temperature control zones are arranged within at least two planes at different distances from the optically effective surface; and

[0015] - The temperature control zones within these at least two planes are in the form of cooling channels, through which a cooling fluid having a cooling-fluid temperature that can be set independently and variably can flow.

[0016] The present invention is particularly based on the concept of producing an adaptive mirror having an optically effective surface that is selectively deformable by providing temperature control zones that are at different distances from the optically effective surface and can be set independently of each other in terms of temperature, wherein the fact that different thermal expansions in different planes of the temperature control zones are ultimately converted into surface deformation of the mirror is utilized in a manner similar to that referred to as the "bimetal effect."

[0017] In other words, the present invention includes a principle that actively generates surface deformation of a relevant mirror in the process of setting a temperature difference in a spatially resolved manner in at least two different planes that are different from each other in terms of distance from an optically effective surface, and in this regard, provides additional degrees of freedom, particularly when setting the wavefront characteristics of an optical system including such a mirror.

[0018] By the fact that the temperatures of different temperature control zones can be set in a spatially variable manner, or independently of each other for individual temperature control zones, respectively, not only in different planes but also within a single same plane, it is possible to realize the aforementioned degrees of freedom in particular also in the form of local degrees of freedom (which is particularly useful when setting wavefront characteristics of an optical system). To this end, the appropriate selection of each temperature within the temperature control zones assigned to different planes makes it possible to have an effect such that effective surface deformation ultimately occurs only at one lateral location on the optically effective surface due to local mechanical stress, while such deformation does not occur in the remaining area of ​​the optically effective surface.

[0019] Overall, the principle used according to the present invention makes it possible to realize a particularly precise setting of the deformation profile in an adaptive mirror, and also makes it possible to correct disturbances having relatively high frequencies from a local perspective in the optical properties of the relevant mirror or an optical system including this mirror. In particular, such disturbances having a low spatial wavelength (e.g., a size of about 1 mm) may be disturbances caused by the spatial distribution of zero-crossing temperatures within the mirror substrate material.

[0020] According to one embodiment, the optical system also includes a control unit for time-variable control of the temperature, each set in a temperature control zone by a temperature control device.

[0021] According to one embodiment, the optical system also includes a device for verifying the cooling power output when a cooling fluid flows through a cooling channel.

[0022] According to one embodiment, the determination of the current heating state of each mirror, which forms the basis of the control, is performed based on the cooling power output by the cooling fluid flowing through the cooling channel.

[0023] In this case, the present invention is based on the additional consideration that, given a known flow rate and a known heat transfer coefficient in the region of each cooling channel wall, the cooling power output of the cooling fluid flowing within the cooling channel ultimately constitutes a measure of the temperature gradient existing within the mirror substrate material on average and thus a measure of the current heating state of the mirror.

[0024] Cooling fluid in cooling channel ( For the cooling power output by the cooling fluid when flowing through ), the following equation holds true.

[0025]

[0026] Here, α represents the heat transfer coefficient in the region of each cooling channel wall, A represents the contact surface of the mirror substrate with respect to the mirror substrate material, and △T represents 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 calculated by integrating the local cooling force along the cooling section and dividing by the heat capacity (C) of the cooling fluid to provide the following equation.

[0027]

[0028] Here, l represents a position along the cooling section, and L represents the total length of the cooling section. The flow rate can be used to determine the mass flow per unit time, and from this, it is possible to determine the value of C using the specific heat capacity of the cooling fluid. Correspondingly, it is possible to determine the average temperature difference (△T) between the mirror substrate material and the cooling fluid, from which an estimation of the temperature distribution within the mirror substrate material can be obtained.

[0029] Based on the cooling force output by the cooling fluid as it passes through the cooling channel, it is possible to identify the temperature field present in the mirror substrate material with relatively high accuracy; consequently, it is also possible to perform the control of the temperature set by the temperature control device based on this temperature information with higher precision (for example, compared to the conventional determination of the heating state of the mirror based on a temperature sensor or wavefront sensor of an optical system located on the rear side of the mirror). In this regard, the determination of the heating state of the mirror based on the cooling force output of the cooling fluid according to the present invention is particularly advantageous when the mirror substrate material exhibits a nonlinear profile of the temperature dependence of deformation, as absolute knowledge of the current mirror temperature is also involved.

[0030] The aforementioned concept of determining the current heating state of the mirror based on the cooling power output by the cooling fluid flowing through the cooling channel is also advantageous regardless of the aforementioned principle of arranging temperature control zones within different planes within the mirror substrate.

[0031] Therefore, the present invention also additionally,

[0032] - an optically effective surface and a mirror substrate - at least one mirror having a plurality of temperature control zones arranged within 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 each other;

[0033] - A device for verifying the cooling power output when a cooling fluid flows through cooling channels; and

[0034] - A control unit for temporally variable control of the temperature set in each temperature control zone by a temperature control device - The determination of each current heating state of the mirror, which forms the basis of the control, is performed based on the identified cooling power output when a cooling fluid flows through a cooling channel - The present invention relates to an optical system comprising: - a control unit for temporally variable control of the temperature set in each temperature control zone by a temperature control device - the determination of each current heating state of the mirror, which forms the basis of the control, is performed based on the identified cooling power output when a cooling fluid flows through a cooling channel.

[0035] 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, wherein the second mirror substrate portion is arranged on the side of the first mirror substrate portion facing away from the optically effective surface and is made of a second mirror substrate material different from the first mirror substrate material.

[0036] According to one embodiment, two planes of the temperature control zone are assigned to different mirror substrate parts.

[0037] According to one embodiment, the first mirror substrate material has a lower average coefficient of thermal expansion than the second mirror substrate material.

[0038] In the above configuration, the present invention utilizes the fact that greater thermal expansion for a temperature-controlled zone at a relatively greater depth in the mirror substrate compared to the optically effective surface than for a temperature-controlled zone closer to the optically effective surface is absolutely desirable to achieve a significant effect in terms of the desired deformation of the optically effective surface in a manner similar to what is referred to as the bimetallic effect. Furthermore, this configuration makes it possible to partially manufacture the mirror substrate from relatively inexpensive materials (e.g., quartz glass, SiO2) (compared to, for example, ULE™).

[0039] According to one embodiment, each of the plurality of temperature control zones is arranged on at least one of two planes, and the temperature for the temperature control zones located on each plane can be set independently of each other.

[0040] According to one embodiment, the temperature control device has a plurality of Peltier elements assigned to each temperature control zone.

[0041] According to one embodiment, the temperature control device has a plurality of radiant heaters assigned to each temperature control zone.

[0042] According to one embodiment, the mirror is designed for an operating wavelength of less than 30 nm, particularly less than 15 nm.

[0043] According to one embodiment, the optical system is a projection lens or a lighting device of a microlithographic projection exposure device.

[0044] The present invention also relates to a method for operating an optical system, wherein the optical system comprises at least one mirror having an optically effective surface and a mirror substrate, and a plurality of temperature zones are arranged in at least two planes at different distances from the optically effective surface within the mirror substrate, and the temperatures present in each temperature control zone are set independently of each other.

[0045] In this regard, according to one embodiment, the setting of the temperature within the temperature control zone is performed in such a way that the deformation caused by different thermal expansions of the temperature control zones belonging to different planes of the optically effective surface corresponds to the desired deformation.

[0046] According to another embodiment, the setting of the temperature within the temperature control zone is performed in such a way that thermally induced deformation associated with the application of electromagnetic radiation to the optically effective surface of the mirror is at least partially compensated by the thermal expansion of the temperature control zone.

[0047] According to one embodiment, the temperature set in each temperature control zone by the temperature control device is controlled in a time-varying manner.

[0048] According to one embodiment, the temperature control zone is in the form of a cooling channel, through which a cooling fluid having a cooling-fluid temperature that can be variably set independently of each other can flow.

[0049] According to one embodiment, the determination of the current heating state of each mirror, which forms the basis of the control, is performed based on the cooling power output when the cooling fluid flows through the cooling channel.

[0050] The present invention also relates to a method for operating an optical system, wherein the optical system comprises at least one mirror having an optically effective surface and a mirror substrate, and a plurality of temperature control zones are arranged within the mirror substrate such that a cooling fluid having a cooling-fluid temperature that is independently and variablely setable can flow through each of the cooling channels, and the temperature set in each of the temperature control zones is controlled in a time-varying manner, and the determination of the current heating state of each mirror, which forms the basis of this control, is performed based on the verification of the cooling power output when the cooling fluid flows through the cooling channel.

[0051] Other configurations of the present invention are apparent from the detailed description and dependent claims.

[0052] The present invention is described in more detail below based on exemplary embodiments illustrated in the accompanying drawings. Brief explanation of the drawing

[0053] In the drawing: FIG. 1 illustrates a schematic diagram for explaining a possible structure of a mirror according to one embodiment of the present invention; FIGS. 2 to 6 illustrate schematic diagrams for explaining possible structures of a mirror according to another embodiment of the present invention; and Figure 7 illustrates a schematic diagram of a possible structure of a microlithographic projection exposure device designed to operate in EUV. Specific details for implementing the invention

[0054] Figure 7 schematically illustrates a meridional cross-section of a possible structure of a microlithographic projection exposure device designed to operate in EUV.

[0055] According to FIG. 7, the projection exposure device (1) includes a lighting device (2) and a projection lens (10). One embodiment of the lighting device (2) of the projection exposure device (1) has, in addition to a light source or radiation source (3), a lighting optical unit (4) for illuminating an objective field (5) within an objective plane (6). In an alternative embodiment, 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 include the light source (3).

[0056] Here, a reticle (7) arranged in an objective field (5) is exposed. The reticle (7) is held by a reticle holder (8). The reticle holder (8) can be displaced, particularly in the scanning direction, by a reticle displacement drive (9). For the purpose of explanation, a Cartesian xyz coordinate system is shown in FIG. 7. The x direction proceeds perpendicular to the plane of the drawing. The y direction proceeds horizontally, and the z direction proceeds perpendicularly. The scanning direction proceeds along the y direction in FIG. 7. The z direction proceeds perpendicular to the objective plane (6).

[0057] The projection lens (10) serves to image the objective field (5) within the image field (11) in the image plane (12). A structure on the reticle (7) is imaged onto the photosensitive layer of a wafer (13) arranged in the area of ​​the image field (11) within the image plane (12). The wafer (13) is held by a wafer holder (14). The wafer holder (14) can be displaced, particularly along the y-direction, through a wafer displacement driver (15). On one hand, the displacement of the reticle (7) through the reticle displacement driver (9) and on the other hand, the displacement of the wafer (13) through the wafer displacement driver (15) may be performed in a manner synchronized with each other.

[0058] The radiation source (3) is an EUV radiation source. The radiation source (3) emits EUV radiation, specifically referred to as radiation or illumination radiation as used below. Specifically, the radiation used has a wavelength in the range of 5 nm to 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 condenser (17) and propagates into an illumination optical unit (4) through an intermediate focus within an intermediate focus plane (18). The illumination optical unit (4) includes a deflection mirror (19) and a first faceted mirror (20) [having a schematically shown facet (21)] and a second faceted mirror (22) [having a schematically shown facet (23)] arranged downstream therefrom within the beam path.

[0059] The projection lens (10) comprises a plurality of mirrors [Mi (i=1, 2, ...)] numbered consecutively according to an arrangement within the beam path of the projection exposure device (1). In the example illustrated in FIG. 7, the projection lens (10) comprises six mirrors (M1 to M6). Alternatives having 4, 8, 10, 12, or any other number of mirrors (Mi) are similarly possible. The second-to-last mirror (M5) and the last mirror (M6) each have a through-opening for the illumination radiation (16). The projection lens (10) is a double-shielded optical unit. The projection lens (10) has an image-side aperture number greater than 0.5 and can also be greater than 0.6, and may be, for example, 0.7 or 0.75.

[0060] During the operation of the microlithographic projection exposure device (1), electromagnetic radiation incident on the optically effective surface of the mirror is partially absorbed and causes heating and associated thermal expansion or deformation as described in the introduction, which may subsequently cause damage to the imaging characteristics of the optical system. The concept according to the present invention may be applied particularly advantageously to any desired mirror of the microlithographic projection exposure device (1) of FIG. 7. This may be implemented to avoid or compensate for thermally induced deformation of the relevant mirror itself (e.g., to compensate for the spatial distribution of zero-crossing temperatures), or in terms of setting the wavefront characteristics of the entire optical system, that is, to provide additional degrees of freedom with or without the corrective action achieved by the relevant mirror.

[0061] The present invention is not limited to use in projection exposure devices designed to operate in EUV. In particular, the present invention may also be advantageously used in projection exposure devices designed to operate in DUV (i.e., at wavelengths less than 250 nm, particularly less than 200 nm) or in other optical systems.

[0062] FIG. 1 illustrates merely a schematic diagram of one possible embodiment of a mirror (100) according to the present invention. The mirror (100) has a mirror substrate (110) (e.g., made of ULE™) and a reflective layer system (120) [e.g., in the form of a molybdenum (Mo)-silicon (Si) multi-coating stack]. 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 effective surface (101). In a particular exemplary embodiment, the temperature control zones (131-136 and 141-146) are in the form of cooling channels through which a cooling fluid having a variably settable cooling-fluid temperature can flow independently of each other.

[0063] "150" represents a temperature control device, through which the temperatures existing in each temperature control zone (131-136, 141-146) can be set independently of each other. As just an example, the temperature control device (150) may have a plurality of Peltier elements assigned to each temperature control zone.

[0064] Although in the exemplary embodiment of FIG. 1 the present invention is realized by each cooling channel through which a cooling fluid can flow, the present invention is not limited thereto. Rather, in other embodiments, the targeted selective setting of different temperatures in different temperature control zones may also be performed in other suitable ways, for example, through a radiant heater having different depths of focus or resistance heating elements.

[0065] Setting different temperatures within the regions of the temperature control zones (131-136) on one side and the temperature control zones (141-146) on the other, located at a first different distance from the optically effective surface (101), causes deformation of the optically effective surface (101) due to different thermal expansion of the mirror substrate material within the relevant plane in a manner similar to that referred to as the bimetallic effect. This can subsequently be used to provide additional degrees of freedom in terms of setting the wavefront characteristics of an optical system [e.g., the projection exposure device (1) from FIG. 7] including the mirror (100).

[0066] Temperature setting in the temperature control zone according to the present invention may be performed on one part to set a desired deformation of the optically effective surface (101) (e.g., to compensate for disturbances or aberrations present elsewhere in the optical system). Alternatively, the temperature setting may also be performed to compensate for thermally induced deformation within the mirror (100) itself. Thus, in the latter case, it is possible for the temperature control zone (141-146) to be used specifically to avoid protrusion or deformation of the mirror (100), or otherwise associated with the (cooling) operation of the temperature control zone (131-136). Thus, in this approach, the temperature control zone (131-136) serves to dissipate heat generated by the absorption of electromagnetic radiation incident on the optically effective surface (101), and the temperature control zone (141-146) serves to compensate for deformation caused in other aspects by the temperature control zone (131-136) through which the cooling fluid flows.

[0067] FIG. 2 illustrates another embodiment of an adaptive mirror (200), and components that are similar or substantially functionally identical to those in FIG. 1 are designated by reference numbers 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), and the mirror substrate portion (210a) arranged closer to the optically effective surface (201) is produced from a mirror substrate material having a relatively low average coefficient of thermal expansion. In a specific exemplary embodiment, the mirror substrate material of the first mirror substrate portion (210a) may be ULE™, and the mirror substrate material of the second mirror substrate portion (210b) may be quartz glass (SiO2).

[0068] FIG. 3 illustrates another embodiment of an adaptive mirror (300) according to the present invention, wherein components similar to or substantially functionally identical to FIG. 2 are designated by reference numbers increased by "100". The exemplary embodiment of FIG. 3 differs from the embodiment of FIG. 2 in that the mirror substrate (310) is composed of three different mirror substrate portions (310a, 310b, 310c), and the walls of each of the cooling channels serving as temperature control zones (331-336, 341-346) have already been introduced into these mirror substrate portions in a manner advantageous from a manufacturing technology perspective. Specifically, a first mirror substrate portion (310a) (which can be manufactured from ULE™) serves as an upper portion for a cooling channel that acts as a temperature control zone (331-336), and a second mirror substrate portion (310b) [which can be manufactured from, for example, quartz glass (SiO2)] serves as a lower portion for a cooling channel that forms a temperature control zone (341-346). A third mirror substrate portion (310c) is arranged between the first mirror substrate portion (310a) and the second mirror substrate portion (310b), and simultaneously serves as a lower portion for a cooling channel that forms a temperature control zone (331-336) and an upper portion for a cooling channel that forms a temperature control zone (341-346), and may be manufactured from ULE™ or quartz glass (SiO2) depending on specific conditions.

[0069] The use of a material having a relatively high coefficient of thermal expansion compared to ULE™ on the side of the mirror substrate portion (210b) of the embodiment of FIG. 2 or the mirror substrate portion (310b or 310c) of the embodiment of FIG. 3 is advantageous insofar as greater thermal expansion is clearly required [compared to each of the first mirror substrate portions (210a and 310a) closer to the optically effective surface] to achieve a significant deformation effect in the adaptive mirror according to the present invention in the region of these mirror substrate portions. At the same time, in a specific region, the adaptive mirror can be manufactured in this way with a relatively less expensive material (compared to ULE™).

[0070] FIG. 4 illustrates another embodiment of an adaptive mirror (400), and components that are similar or substantially functionally identical to those in FIG. 1 are designated by reference numbers increased by "300". The embodiment of FIG. 4 differs from the embodiment of FIG. 1 in that, instead of temperature control zones (131-136), only a single temperature control zone (431) (which is not divided into continuous or multiple individual temperature control zones) exists in the relevant plane within the mirror substrate (410). In the configuration according to FIG. 4, with respect to this undivided temperature control zone (431), the lateral spatial resolution achievable by the division is intentionally omitted to reduce the total number of required cooling fluid ports, thereby first reducing structural costs and, second, also preventing the risk of airtightness defects or leakage occurring in the area of ​​the cooling channels.

[0071] FIG. 5 illustrates another embodiment of an adaptive mirror (500), and components that are similar or substantially functionally identical to those in FIG. 1 are designated by reference numbers increased by "400". The embodiment of FIG. 5 differs from the embodiment of FIG. 1 in that, instead of temperature control zones (141-146) arranged in a plane at a relatively distant distance from the optically effective surface (101) according to the embodiment of FIG. 1, only a single temperature control zone (541) (not divided into continuous or multiple individual temperature control zones) is provided. In other words, in the embodiment according to FIG. 5, in contrast to FIG. 4, division or lateral spatial resolution is omitted for a plane or temperature control zone at a greater distance from the optically effective surface, rather than in a plane closer to the optically effective surface. Additionally, in this configuration, reducing the total number of required cooling fluid ports has the effect of simplifying the structure and reducing the risk of leakage from a design perspective.

[0072] FIG. 6 illustrates another embodiment of an adaptive mirror (600), and components that are similar or substantially functionally identical to those in FIG. 1 are designated by reference numbers increased by "500". The embodiment of FIG. 6 differs from the embodiment of FIG. 1 in that the temperature control zones (131-136 and 141-146) in two planes according to FIG. 1 are replaced by a single temperature control zone (631 and 641) each (which is not divided into a continuous and multiple individual temperature control zones). In this embodiment, the division or lateral resolution in the two planes within the area of ​​the temperature control zones (631, 641) is omitted, thereby minimizing the number of cooling fluid ports.

[0073] In all the aforementioned embodiments, water or any other suitable cooling fluid of choice may be used as the cooling fluid.

[0074] In another embodiment, the concept according to the present invention of cooling channels or temperature control zones in which cooling fluids flow independently of each other can also be used in combination with local heating of the optically effective surface of the relevant mirror (e.g., by a radiant heater).

[0075] In all embodiments described above based on FIGS. 1 to 6, the temperature set within each temperature control zone can be controlled in a time-varying manner. In this regard, the determination of the current heating state of each mirror, which forms the basis of this control, can also be performed particularly and advantageously based on the verification of the cooling power output when a cooling fluid flows through a cooling channel. To this end, for example, the temperature change of the cooling fluid flowing through the cooling channel can be measured using temperature sensors at the inlet and outlet, and then, given the known flow rate and known heat transfer coefficient at each cooling channel wall, a conclusion regarding the temperature gradient existing within the mirror substrate material can be drawn.

[0076] Although the present invention has been described based on specific embodiments, numerous variations and alternative embodiments will be apparent to those skilled in the art, for example, by combinations and / or exchanges of features of individual embodiments. Accordingly, it is obvious to those skilled in the art that such variations and alternative embodiments are also included in the present invention, and that the scope of the present invention is limited only to the meaning of the appended claims and their equivalents.

Claims

Claim 1 An optical system having an optically effective surface (101, 201, 301, 401, 501, 601) and a mirror substrate (110, 210, 310, 410, 510, 610), and at least one mirror (100, 200, 300, 400, 500, 600) having 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) arranged within the mirror substrate; and includes a temperature control device (150, 250, 350, 450, 550, 650) that enables temperatures existing in each of the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) to be set independently of each other; and 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 optically effective An optical system arranged in at least two planes at different distances from surfaces (101, 201, 301, 401, 501, 601); 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 a cooling fluid having a cooling-fluid temperature that can be variably set independently of each other can flow; and the optical system also has a device for verifying the cooling power output when the cooling fluid flows through the cooling channels. Claim 2 An optical system according to claim 1, further comprising a control unit for temporally variable control of a temperature set in each of 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 a temperature control device. Claim 3 An optical system according to claim 1 or 2, characterized in that the determination of the current heating state of each mirror, which forms the basis of the control, is performed based on the cooling power output by the cooling fluid when the cooling fluid flows through the cooling channel. Claim 4 An optical system having an optically effective surface (101, 201, 301, 401, 501, 601) and a mirror substrate (110, 210, 310, 410, 510, 610), 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) arranged within the mirror substrate, and temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) is in the form of a cooling channel, through which a cooling fluid having a variable cooling-fluid temperature can flow independently of each other, at least one mirror (100, 200, 300, 400, 500, 600); a device for verifying the cooling power output when the cooling fluid flows through the cooling channel; An optical system comprising a control unit for temporally variable control of a temperature set in each of 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 a temperature control device, wherein the determination of each current heating state of the mirror, which forms the basis of the control, is performed based on a confirmed cooling power output when a cooling fluid flows through a cooling channel. Claim 5 An optical system according to any one of claims 1, 2, or 4, wherein the mirror substrate (210, 310) has a first mirror substrate portion (210a, 310a) made of a first mirror substrate material and at least one second mirror substrate portion (210b, 310b), wherein the second mirror substrate portion is arranged on the side of the first mirror substrate portion (210a, 310a) facing away from the optically effective surface (201, 301) and is made of a second mirror substrate material different from the first mirror substrate material. Claim 6 An optical system according to claim 5, characterized in that 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 (210a, 210b, 310a, 310b). Claim 7 An optical system according to claim 5, characterized in that the first mirror substrate material has a lower average coefficient of thermal expansion than the second mirror substrate material. Claim 8 An optical system according to any one of claims 1, 2, or 4, characterized in that each of the plurality of temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 441-446, 531-536) is arranged within at least one of two planes, and the temperatures for the temperature control zones located in each plane can be set independently of each other. Claim 9 An optical system according to any one of claims 1, 2, or 4, wherein the temperature control device has a plurality of Peltier elements assigned to each temperature control zone (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641). Claim 10 An optical system according to any one of claims 1, 2, or 4, wherein the temperature control device has a plurality of radiant heaters assigned to each temperature control zone (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641). Claim 11 An optical system according to any one of claims 1, 2, or 4, characterized in that the mirror (100, 200, 300, 400, 500, 600) is designed for an operating wavelength of less than 30 nm or less than 15 nm. Claim 12 An optical system characterized in that, in any one of claims 1, 2, or 4, the optical system is a projection lens or a lighting device of a microlithographic projection exposure device (1). Claim 13 A method for operating an optical system, wherein the optical system has an optically effective surface (101, 201, 301, 401, 501, 601) and a mirror substrate (110, 210, 310, 410, 510, 610), and 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) arranged in at least two planes at different distances from the optically effective surface within the mirror substrate (110, 210, 310, 410, 510, 610), and at least one mirror (100, 200, 300), It includes 400, 500, 600), and the temperatures existing within each temperature control zone (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, and the setting of the temperatures within 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 optically effective caused by different thermal expansions of the temperature control zones belonging to different planes. A method in which deformation of the surface (101, 201, 301, 401, 501, 601) is performed in a manner corresponding to a desired deformation. Claim 14 A method for operating an optical system, wherein the optical system has an optically effective surface (101, 201, 301, 401, 501, 601) and a mirror substrate (110, 210, 310, 410, 510, 610), and 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) arranged in at least two planes at different distances from the optically effective surface within the mirror substrate (110, 210, 310, 410, 510, 610), and at least one mirror (100, 200, 300), 400, 500, 600, including temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641), and the setting of the temperature within the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, thermally induced mirror deformation associated with the application of electromagnetic radiation to the optically effective surface (101, 201, 301, 401, 501, 601) A method performed in such a way that it is at least partially compensated by the thermal expansion of the temperature control zones (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641), wherein the temperature set in each of the temperature control zones by the temperature control device is controlled in a time-varying manner. Claim 15 A method according to claim 13, characterized in that the temperature set in each temperature control zone (131-136, 141-146, 231-236, 241-246, 331-336, 341-346, 431, 441-446, 531-536, 541, 631, 641) by a temperature control device is controlled in a time-variable manner. Claim 16 A method according to any one of claims 13 to 14, 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 cooling-fluid temperature that can be variably set independently of each other can flow. Claim 17 A method according to claim 14 or 15, 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 cooling-fluid temperature that can be variably set independently of each other can flow, and the determination of each current heating state of the mirrors that form the basis of control is performed based on the verification of the cooling power output when the cooling fluid flows through the cooling channels. Claim 18 A method for operating an optical system, wherein the optical system has an optically effective surface (101, 201, 301, 401, 501, 601) and a mirror substrate (110, 210, 310, 410, 510, 610), and 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) in the form of cooling channels through which a cooling fluid having a cooling-fluid temperature that is independently and variably settable can flow, and at least one mirror (100), A method comprising 200, 300, 400, 500, 600), wherein the temperature set in each of 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 controlled in a time-varying manner, and the determination of each current heating state of the mirror, which forms the basis of this control, is performed based on the verification of the cooling power output when the cooling fluid flows through the cooling channel. Claim 19 delete

Images