Method for processing a workpiece

Abstract

The invention relates to a method for processing a workpiece (17) in a processing process, preferably a photolithographic structuring process, in which the processing of the workpiece (17) comprises controlling the temperature of the workpiece (17), in which the temperature of the workpiece (17) is controlled by flowing a fluid (27) through at least one channel (26) formed in the workpiece (17).

Description

[Technical field]

[0001] [Reference to Related Applications] This application claims priority from German patent application No. 10 2022 202 059.6 filed on March 1, 2022, the entire disclosure content of which is incorporated herein by reference.

[0002] The present invention relates to a method for processing a workpiece in a processing process, preferably a lithographic structuring process, wherein the processing of the workpiece comprises controlling the temperature (heating and / or cooling) of the workpiece. [Background technology]

[0003] During the processing process, for example during structuring of the workpiece, it is often necessary to control the temperature of the workpiece. If the workpiece is processed in the processing process and heat is introduced into the workpiece, the temperature control can take the form of cooling, in particular by means of compressed air nozzles. If the processing process includes a step by heat treatment (tempering), for example, the temperature control can also involve heating of the workpiece. Such a heat treatment can be carried out on the workpiece itself or on a resist layer that has been freshly applied to the workpiece and still contains residual amounts of solvent, so that the resist layer can be baked to drive off the solvent. The resist layer can be, for example, a photoresist layer that is baked in a so-called soft bake or pre-bake step of a photolithography process (see, for example, "https: / / imicromaterials.com / technical / lithography-process-overview" or "http: / / www.lithoguru.com / scientist / lithobasics.html") and then structured.

[0004] To bake such a photoresist layer, the workpiece, in this case usually a wafer, can be introduced into a convection oven or heated with a so-called hotplate (a hot, usually metal plate). In the case of heating with a hotplate, the wafer is placed on the hotplate or held slightly away from its surface, i.e. the heat transfer occurs by conduction and is therefore relatively rapid. In contrast, heating of a wafer in a convection oven is much slower, see "https: / / www.microchemicals.com / technical_information / softbake_photoresist.pdf".

[0005] For thick resist layers, drying in a convection oven is generally not advisable, since the dry resist surface does not allow the solvent to evaporate quickly enough. In this case, the use of a hotplate is advantageous, since the solvent is driven out from under the resist layer (see "https: / / www.allresist.de / faqphotoresists-0080temperungnachbeschichtung / ").

[0006] US Patent No. 5,399,633 discloses a method for forming a binary germanosilicate glass on a wafer containing integrated circuits. In this method, a solution containing a solvent is deposited on the wafer, and the wafer is spun until excess solution is shaken off the wafer and the remaining solution is in equilibrium. The wafer and remaining solution are baked until the solvent is driven off and the binary germanosilicate glass is formed. The baking step can be one bake step at 400° C. or higher to drive off all the solvent and produce the oxide of the binary glass.

[0007] US Patent No. 5,399,633 discloses an X-ray lithography mask having a mask carrier in the form of a thin film of absorbing material, which contains aluminum nitride, which is particularly useful for enabling very precise heat treatment or baking, since the thermal expansion coefficient of aluminum nitride is approximately the same as that of the substrate to be subjected to the heat treatment.

[0008] To control the temperature of the workpiece, it is usually necessary to introduce the workpiece into an apparatus especially provided for this purpose, such as an oven, and therefore the workpiece generally cannot remain in the processing machine where the processing process or a step of the processing process (e.g. resist coating, developing, etching, etc.) is performed in order to control the temperature. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] European Patent No. 0 206 938 [Patent Document 2] German Patent No. 3539201 Summary of the Invention [Problem to be solved by the invention]

[0010] It is an object of the invention to provide a method which allows a particularly efficient control of the temperature of a workpiece in a machining process. [Means for solving the problem]

[0011] This object is achieved by a method of the aforementioned type, which comprises the step of controlling the temperature of the workpiece by flowing a (temperature-controlled) fluid, i.e. a (temperature-controlled) liquid or a (temperature-controlled) gas, through at least one flow passage formed in the workpiece.

[0012] In the method according to the invention, it is proposed to pass a fluid through channels, e.g. cooling channels, in the workpiece or formed in the workpiece specifically for this purpose, during at least one step of the processing process, which are usually adapted to pass a fluid during the operation of the workpiece. In this case, the fluid flowing through the channels, which is itself temperature-controlled, i.e. has a predefined temperature, is used to control the temperature of the workpiece. In this way, the channels, which are in any case provided in the workpiece, can be used in one or more steps of the processing process to control the temperature of the workpiece. The workpiece can thus remain in the respective processing machine, e.g. for baking, developing, etching, etc. of the workpiece, and its temperature can be controlled without further processing. In this way, the value stream is simplified and the machines are minimized.

[0013] In one variant of the invention, a layer is applied to the workpiece, which is baked in at least one baking step during control of the temperature of the workpiece. The baking may for example serve to interconnect two or more components of the layer, as is the case for example of binary glasses as described in US Pat. No. 5,399,991. To ensure good heat transfer from the fluid to the layer, one or more channels are preferably formed in the workpiece, in this case close to the layer.

[0014] In a development of this variant, the layer is a photoresist layer that is to be structured in a photolithographic structuring process. For baking such a photoresist layer, temperatures of the order of about 100° C. are generally sufficient, and these temperatures can be easily reached using fluid-type heating means, in particular liquid-type heating means. The liquid flowing through the channels can in this case be, for example, water.

[0015] In a development of this variant, a baking step is carried out before the exposure step in which the photoresist layer is exposed to light in order to drive off the solvent from the photoresist layer, the baking step being in this case a so-called soft bake, which is carried out on the unstructured layer before the exposure step, before the development step which follows the exposure step and before the etching step which follows the development step.

[0016] In the case of temperature control by flow of a fluid through one or more channels, the thermal energy comes from the workpiece itself and not from the surrounding area as in the case of temperature control in an oven. It is much more efficient to drive the solvent out of the layer from the depth of the layer towards the surface of the layer than in the opposite direction. Such drive of the solvent from the bottom to the top of the layer also occurs in the case of baking on a hotplate as described above, but baking on a hotplate can usually only be carried out with layers deposited on flat and relatively small surfaces. In contrast, the flow of a fluid through channels formed in the workpiece according to the invention can also be carried out on large workpieces. Furthermore, in the case of the method according to the invention, the surface to which the layer is applied can be curved or freeform.

[0017] In yet another variant, a baking step is carried out after an exposure step in which the photoresist layer is exposed to light. In this case, the baking step is a so-called post-exposure bake step or a hard bake step. A post-exposure bake step may be necessary to increase the diffusion in the photoresist layer after the exposure step. The exposure step and the (optional) post-exposure bake step are followed by a development step, which is followed by a hard bake step in which residual solvent is driven off and the photoresist layer is hardened. Even during the hard bake step, the temperature of the layer is of the order of about 100° C., so that it is generally easily possible to flow a correspondingly temperature-controlled fluid through the channel or channels.

[0018] In yet another variation, the workpiece is in the form of a mirror, and the layer to be baked is preferably applied to an optical surface of the mirror, that is the surface of the mirror on which the radiation it reflects is incident. A reflective coating may be applied to the optical surface, although this is not necessary, depending on the material of the mirror and the wavelength of the incident radiation.

[0019] In yet another variant, the mirror has a substrate in which at least one channel is formed. The substrate in which the channel or channels are formed can be, for example, glass, glass ceramic or another material, for example metal. The channel or channels in this case usually serve to cool the mirror during its operation, i.e. it is a directly cooled mirror, as described in DE 10 2019 217 530 A1. In the case of such mirrors, the cooling channels usually run close to the optical surface, thus allowing a fast and efficient control of the temperature of the layer applied to the optical surface.

[0020] In yet another variant, the structuring of the layer produces a structure on the surface of the mirror, in particular a grating structure and / or at least one marking. The layer applied to the surface of the mirror or substrate, in this case a photoresist layer, is structured using a lithographic structuring process to produce a structure, for example a grating structure or a marking. The grating structure can be a binary structure, a so-called blazed structure. A reflective coating, for example in the form of a multilayer coating, can be applied to the grating structure in a subsequent coating process. The grating structure can perform different functions depending on the application. The marking(s) on the surface of the mirror can serve, for example, for adjustment or alignment / positioning of the mirror. Other types of structures can also be produced on the surface of the mirror.

[0021] In yet another variant, the structuring of the layer forms at least one structured conductive or electrically insulating layer on at least one surface of the mirror. In this variant, the baked layer is also a photoresist layer, which is usually structured during a photolithography process. The photoresist layer can form a conductive or electrically insulating layer by itself, but it is also possible for the photoresist layer to be applied to an underlying layer of conductive or electrically insulating material. In this case, during the etching operation, not only a part of the photoresist layer but also a part of the underlying layer is removed for structuring. As a rule, the photoresist layer is completely removed after the etching operation, leaving only a structured layer of conductive or electrically insulating material remaining on the surface.

[0022] The structured conductive layer can form conductor tracks or other conductive structures that can serve for example to actuate electromechanical components. It is also possible for the structuring to serve to electrically insulate the conductive structures on one or more surfaces of the mirror. In this case, an electrical insulating layer is used to create an insulator layer that usually serves to electrically insulate adjacent or underlying conductive structures. The structured conductive or electrically insulating layer can be applied to any desired surface of the mirror, even to the optical surface, but only if this layer or the conductive or electrically insulating structures are positioned outside the reflective coating applied thereto.

[0023] In one variant, the structuring of the layer results in the formation of at least one structured passivation layer on at least one surface of the mirror. Within the meaning of the present application, a passivation layer is understood to mean a protective layer that protects the covered substrate regions against oxidation or hydrogen-induced outgassing (HIO). The structured passivation layer can be a photoresist layer that is sintered during a baking operation, for example a photoresist that is sintered to form SiO2 (for example the photoresist "Medusa 82", see https: / / www.allresist.com / allresist-presents-medusa-82-at-the-mne-2019-in-rhodes / ). However, the passivation layer can also be a layer that is arranged under the photoresist layer and partly removed during the structuring of the photoresist layer. Such a passivation layer can be a polymer layer, for example a layer made of polyimide, for example Durimide® from Fujifilm. As mentioned above, the photoresist layer is generally completely removed during or after the structuring of the polymeric layer, so that only the structured polymeric layer remains on the surface.

[0024] In yet another variant, the mirror is designed for use in an EUV lithography apparatus, and the grating structure preferably forms a spectral filter. The radiation emitted by the EUV radiation source contains, in addition to radiation in the EUV wavelength range, also radiation in other wavelength ranges, in particular in the IR wavelength range, which is undesirable to propagate through the EUV lithography apparatus. The grating structure can serve to suppress undesirable spectral components of the radiation emitted by the EUV radiation source. The mirror can be a collector mirror, which serves to focus the EUV radiation emitted by the EUV radiation source. However, it is also possible to provide other mirrors of the EUV lithography apparatus, for example mirrors of the illumination system or the projection system of the EUV lithography apparatus, with grating structures serving as spectral filters or for another purpose.

[0025] To produce the grating structures forming the spectral filter, a structured layer can be applied to the substrate of the collector mirror, as described in DE 10 2018 220 629 A1, the contents of which are incorporated herein by reference in their entirety. As described in said document, the structured layer can be a layer of photoresist structured by a lithographic method. In this case, in order to control the temperature of the substrate, and more particularly to heat it, each baking step of the photolithographic method can be carried out in the manner described above, i.e. by flowing a fluid through one or more cooling channels formed in the substrate. The substrate in which the cooling channels are formed can be, for example, amorphous silicon (a-Si), silicon dioxide (SiO2), Ti, Pt, Au, Al TiO2, Ni, Cu, NiP, Ag, Ta or Al2O3. As described in DE 10 2018 220 629 A1, the substrate itself can also be structured to produce the grating structures. A collector mirror having a substrate that is coated and processed to form a structured external light portion is also described in DE 10 2019 200 698 A1.

[0026] In yet another variant, the fluid flowing through the flow channel has a temperature between 60°C and 120°C, preferably between 80°C and 110°C. The temperature of the fluid decreases as it flows through the flow channel from the flow channel inlet to the flow channel outlet. The temperature of the fluid is in the temperature range specified above throughout the flow channel, i.e. from the flow channel inlet to the flow channel outlet. As mentioned above, a temperature of the resist layer within the temperature range specified above is sufficient for baking the resist layer. The temperature in the specified temperature range can be reached, for example, by flowing water through the flow channel. Solvents, for example alcohol or oil, are also considered as liquids flowing through the flow channel. A temperature-controlled gas or a mixture of temperature-controlled gases can also serve as a fluid flowing through the flow channel.

[0027] In yet another variant, the temperature and / or flow rate of the fluid flowing through at least one flow path is adjusted or set to a predetermined value. The temperature of the fluid is generally set when the fluid flowing through the flow path is not conveyed in a closed circuit. In this case, the fluid is heated to a desired value before passing through the flow path. When the fluid is conveyed in a closed circuit, it is generally expedient to monitor the temperature of the fluid by means of one or more temperature sensors in order to adjust the temperature of the fluid to the desired (set) value. In this way, by controlling the temperature of the fluid, the workpiece and in particular the layer applied thereto can be brought to and kept at a very precisely predetermined temperature. In addition to the temperature of the fluid, the flow rate of the fluid through the flow path is also a parameter that can be controlled in an open or closed loop in order to affect the temperature of the workpiece as desired. Needless to say, the temperature of the workpiece can also be changed over time by setting the temperature and / or flow rate of the fluid, if this is expedient for the respective processing process.

[0028] Further features and advantages of the invention emerge from the following description of exemplary embodiments of the invention, with reference to the figures of the drawing which show the essential details of the invention, and from the claims. Each of the individual features can be implemented alone or in any combination of several in a variant of the invention.

[0029] Exemplary embodiments are shown in the schematic drawings and explained in the following description. [Brief description of the drawings]

[0030] [Figure 1] 1 shows a schematic meridian section of a projection exposure apparatus for EUV projection lithography; [Figure 2a] 1 shows a schematic diagram of a collector mirror having channels through which liquid can flow to control the temperature of the substrate during a bake step of a lithographic structuring process. [Figure 2b] 2 shows a schematic view of a collector mirror during an exposure step of a lithographic structuring process. [Figure 2c] FIG. 2 shows a schematic diagram of the collector mirror after the etching step of the lithographic structuring process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] In the following description of the drawings, the same reference numbers are used for components that are the same or have the same function.

[0032] The essential components of an optical apparatus for EUV lithography in the form of a microlithography projection exposure apparatus 1 are described below by way of example with reference to Fig. 1. The description of the basic arrangement of the projection exposure apparatus 1 and its components should not be understood here as limiting.

[0033] An embodiment of the illumination system 2 of the projection exposure apparatus 1 comprises, in addition to the light source or radiation source 3, an illumination optical unit 4, which illuminates an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the rest of the illumination system. In this case, the illumination system does not include the light source 3.

[0034] A reticle 7 arranged in the object field 5 is illuminated. The reticle 7 is held by a reticle holder 8. The reticle holder 8 is displaceable in particular in the scanning direction by a reticle displacement drive 9.

[0035] For illustrative purposes, a Cartesian xyz coordinate system is shown in Fig. 1. The x direction extends perpendicular to the plane of the drawing. The y direction extends horizontally and the z direction extends vertically. In Fig. 1, the scanning direction extends in the y direction. The z direction extends perpendicular to the object plane 6.

[0036] The projection exposure apparatus 1 comprises a projection system 10, which serves to image the object field 5 into an image field 11 in an image plane 12. A structure on a reticle 7 is imaged onto a photosensitive layer of a wafer 13, which is arranged in the region of the image field 11 in the image plane 12. The wafer 13 is held by a wafer holder 14, which is displaceable in particular along the y direction by a wafer displacement drive 15. The displacement of the reticle 7 firstly by the reticle displacement drive 9 and the displacement of the wafer 13 secondly by the wafer displacement drive 15 can be synchronized with respect to one another.

[0037] The radiation source 3 is an EUV radiation source. The radiation source 3 in particular emits EUV radiation 16, also referred to in the following as working radiation, illumination radiation or illumination light. In particular, the working radiation has a wavelength in the range of 5 nm to 30 nm. The radiation source 3 may be a plasma source, for example an LPP (Laser Produced Plasma) source or a GDPP (Gas Discharge Plasma) source. It may also be a synchrotron-based radiation source. The radiation source 3 may be a Free Electron Laser (FEL).

[0038] The illumination radiation 16 leaving the radiation source 3 is focused by a collector mirror 17. The collector mirror 17 may be a collector mirror with one or more ellipsoidal and / or hyperbolic reflecting surfaces. The illumination radiation 16 may be incident on at least one reflecting surface of the collector mirror 17 at grazing incidence (GI), i.e. at an angle of incidence greater than 45°, or at normal incidence (NI), i.e. at an angle of incidence smaller than 45°. The collector mirror 17 may be structured and / or coated, on the one hand, to optimize its reflectivity for the radiation used and, on the other hand, to suppress extraneous light.

[0039] Downstream of the collector 17 mirror, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 may represent a separation between the source module, including the radiation source 3 and the collector mirror 17, and the illumination optics unit 4.

[0040] The illumination optical unit 4 comprises a deflection mirror 19 and a first facet mirror 20 arranged downstream thereof in the beam path. The deflection mirror 19 can be a plane deflection mirror or a mirror with a beam-influencing effect beyond a pure deflection effect. Alternatively or additionally, the deflection mirror 19 can be in the form of a spectral filter which separates the used optical wavelength of the illumination radiation 16 from extraneous light of wavelengths outside it. The first facet mirror 20 comprises a number of individual first facets 21, also referred to as field facets in the following. FIG. 1 shows only some of said facets 21 by way of example. In the beam path of the illumination optical unit 4, a second facet mirror 22 is arranged downstream of the first facet mirror 20. The second facet mirror 22 comprises a number of second facets 23.

[0041] The illumination optical unit 4 therefore forms a double-facet system. This basic principle is also called a fly's eye integrator. By means of a second facet mirror 22, the individual first facets 21 are imaged into the object field 5. The second facet mirror 22 is the last beam-shaping mirror in the beam path upstream of the object field 5 or indeed the final mirror for the illumination radiation 16.

[0042] The projection system 10 comprises a number of mirrors Mi, which are consecutively numbered according to their position in the beam path of the projection exposure apparatus 1 .

[0043] In the example shown in Fig. 1, the projection system 10 comprises six mirrors M1-M6. Four, eight, ten, twelve or any other number of mirrors Mi are equally possible. The penultimate mirror M5 and the final mirror M6 each have a passing aperture for the illumination radiation 16. The projection system 10 is a double-shielded optical unit. The projection optical unit 10 has an image-side numerical aperture which may be greater than 0.4 or 0.5, may be greater than 0.6, and may for example be 0.7 or 0.75.

[0044] Like the mirrors of the illumination optical unit 4 , the mirror Mi may have a highly reflective coating for the illumination radiation 16 .

[0045] 2a-2c show three steps of a processing process in the form of a lithographic structuring process for a workpiece in the form of a collector mirror 17 shown in FIG. 1. The lithographic structuring process serves to structure a photoresist layer 25a applied to the substrate 24 of the collector mirror 17. The photoresist layer 25a was applied in a previous coating step (by spin coating) to the substrate 24, more particularly to the surface 24a of the substrate 24 which forms the optical surface of the collector mirror 17 on which the illumination radiation 16 is incident and from which the illumination radiation 16 is reflected. Two photoresist layers 25b, 25c which are likewise structured in the lithographic structuring process are also applied to the respective side surfaces 24b, 24c of the substrate 24. It goes without saying that the photoresist layer to be structured can also be applied to the rear side 25d of the substrate 24.

[0046] 2a shows the collector mirror 17 during a baking step for baking the photoresist layers 25a-25c (soft bake) in order to drive off the solvent from the photoresist layers 25a-25c. During the baking step, the photoresist layers 25a-25c are heated to a temperature T S 2a utilizes a liquid 27 flowing through a channel 26 in the substrate 24. The channel 26 is one of a number of cooling channels formed in the substrate 24. The cooling channels can be formed, for example, by milling or by the substrate 24 being constructed in two parts as described in DE 10 2019 217 530 A1, the contents of which are incorporated herein by reference in their entirety.

[0047] In the illustrated example, the substrate 24 is amorphous silicon (a-Si), but could be another material, such as silicon dioxide (SiO2), Ti, Pt, Au, AlTiO2, Ni, Cu, NiP, Ag, Ta, or Al2O3. A coolant, typically water, is passed through the channels 26 to cool the collector mirror 17 while the collector mirror 17 is in operation in the EUV lithography apparatus 1.

[0048] In the lithographic structuring process described herein, the substrate 24, and thus the layers 25a-25c, are heated to a desired temperature T S A liquid 27 is flowed through the flow channel 26 in order to heat it to a temperature T . For this purpose, the temperature of the liquid 27 flowing through the flow channel 26 is controlled, and the liquid is heated to a temperature T , typically between 60° C. and 120° C. or between 80° C. and 110° C. F The liquid 27 is heated to a temperature of 1000° C. A conventional heating device, for example in the form of a resistive heater, can be used to heat the liquid 27. The liquid 27 is supplied to the flow channel 26 via a liquid supply system, not shown, for example in the form of a flexible tube. Correspondingly, the liquid 27 leaving the flow channel 26 is discharged from the flow channel 26 or from the mirror 17 via a liquid discharge system, not shown, for example of the flexible tube type. Instead of a fluid in the form of a liquid 27, a fluid in the form of a (temperature-controlled) gas can also be used to flow through the flow channel 26.

[0049] The mirror 17, and thus the photoresist layers 25a-25c to be baked, are heated as precisely as possible to a predetermined temperature T S and maintain it at this temperature, the temperature T F can be set or adjusted to a predetermined value. F is typically regulated to a predetermined (set) value when the liquid 27 is conveyed in a closed loop to repeatedly pass through the flow path 26. In this case, there is generally at least one temperature sensor in the liquid circuit. The temperature can be set or regulated using a conventional open-loop or closed-loop controller. The temperature T of the mirror 17 or of each photoresist layer 25a-25c is S is the flow velocity v of the liquid 27 through the flow path 26 F The desired temperature T S To maintain the temperature T F The flow rate of liquid 27 is v F In the illustrated example, for simplicity, the photoresist layers 25a to 25c are heated to the same temperature T S The mixture shall be heated to 150°C.

[0050] As shown in Figure 2b, after baking the photoresist layer 25a applied to the optical surface 24a, the photoresist layer 25a is exposed, in which case it is irradiated with exposing radiation 29. The photoresist layer 25a is selectively exposed in this case only in those parts that are to be subsequently removed, a part 28 of which is shown by way of example in Figure 2b.

[0051] The exposure step shown in Fig. 2b is followed by a development step, not shown, during which the photoresist layer 25a is developed. The development step is followed by an etching step, during which the photoresist layer 25a is structured by etching away those parts 25a of the photoresist layer 25a which are the subject of removal. Fig. 2c shows the result of such removal, which forms a grating structure 30 in the collector mirror 17, only a detail of which is shown in Fig. 2c.

[0052] As can also be seen in Fig. 2c, beveled edges of the grating structure 30 are created during the etching process. As described in DE 10 2018 220 629 A1, this has proven advantageous for subsequently coating the grating structure 30 with a protective layer or a reflective coating.

[0053] As shown in Figure 2b, the photoresist layer 25a is also exposed in two further portions 28a, 28b near the edges of the optical surface 24a, which after a development step that develops the photoresist layer 25a and after an etching step that structures the photoresist layer 25a, form two position markings 32a, 32b on the optical surface 24a, as shown in Figure 2c, for the adjustment or alignment of the mirror 17. Structures other than the grating structure 30 or the markings 32a, 32b can also be formed on the optical surface 24a.

[0054] The photoresist layer 25b applied to the first side 24b of the substrate 24 is also structured by exposure of a plurality of portions 28c using a temperature-controlled lithographic structuring process as described above. A layer 33 made of a conductive material is applied to the side 24b of the substrate 24 below the photoresist layer 25b. During the structuring of the photoresist layer 25b, the conductive layer 33 underneath is also structured. In the example shown, the structured conductive layer forms two conductor tracks 33 which serve to actuate electromechanical components, not shown, for example actuators. As an alternative or in addition to the conductive layer 33, a structured electrically insulating layer can also be applied to the side 24b of the substrate 24, for example to electrically insulate the conductor tracks 33 from the surrounding area.

[0055] The photoresist layer 25c applied to the opposite side 24c of the substrate 24 is lithographically structured as described above by exposure of the portions 28d. As can be seen in FIG. 2c, during structuring, the passivation layer 34 applied below the photoresist layer 25c is also structured. The structured passivation layer 34 is a polymer layer, for example a layer made of polyimide in the form of Durimide®. It goes without saying that other materials that can be lithographically structured, in particular passivation layers made of polymers, can also be applied to the side 24c or to the other surfaces 24a, 24b, 24d of the substrate 24. The passivation layer 24 serves to protect the substrate 24 from environmental influences. The structuring of the passivation layer 34 allows, for example, that the parts of the substrate 24 not covered by the passivation layer 34 can be brought into direct contact with the attachment. As a possible alternative, the photoresist layer 25c itself may act as a passivation layer and may be, for example, a photoresist layer that can be sintered to form SiO2, such as the photoresist "Medusa 82".

[0056] After the exposure of each layer 25a-25c and before the development of each layer 25a-25c, a baking step in the form of a so-called post-exposure bake step is carried out in order to increase the diffusion of the developed layers 25a-25c. After the development of the layers 25a-25c and before the etching, a further baking step (hard bake) is usually carried out in order to drive off residual solvent and to harden the layers 25a-25c. During such a baking step (post-exposure bake or hard bake), the temperature of the collector mirror 17 can be controlled as described above in connection with FIG. 2a, i.e. by flowing a temperature-controlled liquid 27 through the collector mirror 17 or through the channels 26 formed therein. During each baking step, each structured layer 25a-25c is also heated to a temperature T S is heated to

[0057] By controlling the temperature using the channels 26 in the substrate 24, it is not necessary to remove the collector mirror 17 from each processing machine for temperature control or baking. For example, baking can be performed before exposure (soft bake) in the coating apparatus that deposits each layer 25a-25c on the substrate 24. One or more baking steps after exposure (post-exposure bake or hard bake) can be performed in the coating apparatus that exposes the layers 25a-25c, for example.

[0058] During processing steps of the collector mirror 17 where parasitic heat is generated, for example during an etching step after a hard bake step or during plasma cleaning, temperature control in the form of cooling of the collector mirror 17 can be performed. The cooling is performed by controlling the temperature T F The cooling process is carried out in the same manner as the heating process described above, except that the temperature is generally from about 10° C. to about 50° C. during the cooling process.

[0059] The above-described method is not limited to the machining of (collector) mirrors 17, but can also be advantageously used for other workpieces requiring temperature control. The machining of the workpiece does not necessarily have to be a photolithographic structuring of the workpiece. Other machining processes may also require temperature control of the workpiece, i.e. heating or cooling.

Claims

1. A method for processing a workpiece (17) by a photolithographic structuring process, wherein processing the workpiece (17) includes controlling the temperature of the workpiece (17), A method for controlling the temperature of a workpiece (17) by flowing a fluid (27) through at least one passage (26) formed in the workpiece (17).

2. 2. The method of claim 1, wherein at least one layer (25a-25c) is applied to the workpiece (17), which is baked in at least one baking step while controlling the temperature of the workpiece (17).

3. 3. The method of claim 2, wherein said layer is a photoresist layer (25a-25c) that is to be structured in said photolithographic structuring process.

4. 4. The method of claim 3, wherein the baking step is performed before the exposure step of exposing the photoresist layers (25a-25c) to light to drive off solvent from the photoresist layers (25a-25c).

5. 4. The method of claim 3, wherein the baking step is performed after an exposure step in which the photoresist layer (25a-25c) is exposed to light.

6. 3. The method of claim 2, wherein the workpiece is in the form of a mirror (17) and the layer (25a-25c) to be baked is applied to a surface (24a-24d) of the mirror (17), preferably to the optical surface (24a).

7. 7. The method of claim 6, wherein the mirror (17) comprises a substrate (24), and the at least one flow channel (26) is formed in the substrate (24).

8. 7. The method according to claim 6, wherein the structuring of the layer (25a) results in the formation of a structure, in particular a grating structure (30) and / or at least one marking (32a, 32b) on the surface (24a) of the mirror (17).

9. 7. The method of claim 6, wherein the structuring of the layer (25b) results in the formation of at least one structured conductive or electrically insulating layer (33) on at least one surface (24b) of the mirror (17).

10. 7. The method of claim 6, wherein the structuring of the layer (25c) results in the formation of at least one structured passivation layer (34) on at least one surface (24c) of the mirror (17).

11. 7. The method of claim 6, wherein the mirror (17) is designed for use in an EUV lithography apparatus (1) and the grating structure (30) preferably forms a spectral filter.

12. 2. The method according to claim 1, wherein the fluid (27) flowing through the at least one flow path (26) is at a temperature between 60°C and 120°C, preferably between 80°C and 110°C. A method having a temperature (TF) below 0°C.

13. 13. The method according to any one of claims 1 to 12, wherein the temperature (TF) and / or the flow velocity (vF) of the fluid (27) flowing through the at least one flow path (26) is adjusted or set to a predetermined value.

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