Method for manufacturing a main body of an optical element for semiconductor lithography, main body, optical element, and projection exposure apparatus

Abstract

The present invention relates to a method for manufacturing a body of an optical element (Mx, 117) for semiconductor lithography, which comprises, firstly, a step of generating a mixed material containing at least two material components, and secondly, a step of manufacturing an intermediate from the mixed material, the mixed material containing at least one first material component which is the material of the subsequent body, and the mixed material containing a second material component which serves to mechanically stabilize the intermediate, and thirdly, a step of manufacturing the body from the intermediate by means of temporary heating and at least partial removal of the second material component. The present invention also relates to an optical element (Mx, 117), a body, an optical element (Mx, 117), and a projection exposure apparatus (1, 101) for semiconductor lithography provided with the optical element (Mx, 117) manufactured by the method according to the present invention.

Description

Technical Field

[0001] This application claims the priority of the following German patent applications, the contents of which are hereby incorporated by reference in their entirety. German Patent Application No. 10 2022 208 286.9, filed on August 9, 2022 German Patent Application No. 10 2022 116 694.5, filed on July 5, 2022 German Patent Application No. 10 2022 116 695.3, filed on July 5, 2022

[0002] The present invention relates to a method for manufacturing a body of an optical element of a projection exposure apparatus for semiconductor lithography, an optical element manufactured by this method, the body, and the projection exposure apparatus.

Background Art

[0003] Projection exposure apparatuses for semiconductor lithography exhibit highly temperature-dependent behavior with respect to their imaging quality. Elements that are not directly involved in optical imaging, such as mounts and holders or housing parts, and both the optical elements themselves, such as lens elements or mirrors in the case of EUV lithography, change in size or surface shape during heating or cooling, which is directly reflected in the quality of the imaging performed by the system on a semiconductor substrate, a so-called wafer, and a lithography mask thereon, for example a phase mask, a so-called reticle.

[0004] Heating of the individual components of the operating apparatus is caused by the absorption of a part of the radiation, also referred to as the used radiation, which is used for imaging the reticle onto the wafer. This radiation is generated by a light source, also referred to hereinafter as the used light source. In the case of EUV lithography, the used light source is a relatively complex plasma source, in which case a plasma that emits electromagnetic radiation in the desired short-wavelength frequency range is generated by irradiating tin particles with a laser.

[0005] Generally, a projection exposure apparatus is designed for a steady state during operation, i.e., a state in which the temperature of the apparatus components is not expected to change significantly over time. This temperature can vary for each optical element depending on the arrangement of the optical system. In order to minimize the above-described deformation or change over time of the optical element, particularly the mirror, a material with a low coefficient of thermal expansion is used for the main body of the mirror. For example, it is possible to set the coefficient of thermal expansion of fused silica to be 0 at a specific temperature, so-called zero-crossing temperature, by adding, for example, titanium oxide. The coefficient of thermal expansion itself depends on temperature, increasing as the temperature rises, i.e., being negative at temperatures lower than the zero-crossing temperature and positive at temperatures higher than the zero-crossing temperature.

[0006] The main body of each mirror is generally set such that the zero-crossing temperature corresponds to a constant temperature during operation. Further, in order to minimize the influence of the deviation from the zero-crossing temperature on the surface shape of the mirror as much as possible, an attempt is made to make the gradient of the coefficient of thermal expansion as flat as possible.

[0007] Furthermore, since the power of the light source used increases from generation to generation, it is necessary to control the temperature of at least each mirror by means of a flow path provided in the main body. Although the prior art discloses a method for manufacturing a main body incorporating a flow path, it has the drawbacks that it is not suitable for materials having a predetermined zero-crossing temperature and a small coefficient of thermal expansion gradient, or that a large expenditure is necessarily involved in implementation.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] An object of the present invention is to identify a method for eliminating the drawbacks known from the prior art. Another object of the present invention is to identify an improved optical element and an improved main body for semiconductor lithography, and an improved projection exposure apparatus.

MEANS FOR SOLVING THE PROBLEMS

[0009] This object is achieved by a method and an apparatus having the features described in the independent claims. The dependent claims relate to advantageous developments and variants of the invention.

[0010] A method for manufacturing a body of an optical element for semiconductor lithography according to the invention comprises: First, generating a hybrid material comprising at least two material components; Second, manufacturing an intermediate from the hybrid material, wherein the hybrid material comprises at least one first material component that forms the material of the subsequent body, and the hybrid material comprises a second material component that serves to mechanically stabilize the intermediate; and third, manufacturing the body from the intermediate by means of temporary heating and at least partial removal of the second material component. It includes.

[0011] In one embodiment of the method, the at least one first material component may include quartz glass powder, in particular quartz glass powder doped with titanium oxide. The second material component may include at least one polymer. The first material component may also have a plurality of different titanium oxide concentrations each mixed with the second material component.

[0012] Titanium oxide reduces the thermal expansion coefficient of the first material and, by extension, the composite material, which can ideally be zero at the operating temperature of the optical element, i.e., the average temperature that occurs during operation. The temperature at which the temperature-dependent thermal expansion coefficient becomes zero is also referred to as the zero-crossing temperature. Various measures can be used to affect both the zero-crossing temperature and the gradient of the thermal expansion coefficient with temperature change. The level of the thermal expansion coefficient largely depends on the percentage of titanium oxide in the material mainly containing silicon oxide. The higher the titanium oxide content, the lower the thermal expansion coefficient of the composite material, i.e., the body, i.e., the curve of the thermal expansion coefficient versus temperature shifts downward along the y-axis. As a result, simultaneously, the zero-crossing temperature of the composite material shifts to the high-temperature side. By heat-treating the body at a temperature of 900°C to 1200°C, on the one hand, the curve of the thermal expansion coefficient can be shifted in the positive y-direction, i.e., upward, resulting in a decrease in the zero-crossing temperature, and on the other hand, the gradient of the curve can be advantageously reduced, resulting in a reduction in the change in the thermal expansion coefficient in the case of temperature change near the zero-crossing.

[0013] In one embodiment of the present invention, the powder can be produced by grinding a starting material having a predetermined physical property of the body or can be made to correspond to the predetermined physical property of the body after the manufacturing method according to the present invention.

[0014] Furthermore, the tool for grinding the starting material can be made of the material of the first material component. This has the advantage that the first material component is not contaminated by wear of the tool by other substances that affect the physical properties of the body.

[0015] Alternatively, the starting material can be ground non-contact, for example, by an ultrasonic method.

[0016] In yet another embodiment, the powder can be produced by a soot method.

[0017] Furthermore, the titanium oxide content in the powder produced by grinding or non-contact manufacturing has a deviation of less than 5%, preferably less than 0.5%, particularly preferably less than 0.05% per 1 g of the sample from the average titanium oxide content of the main body. This can be achieved, for example, by better mixing of the powder and / or mixing of different powder batches compared to conventional direct deposition or soot deposition. This has the advantage that as a result, the variation in the titanium oxide content in the subsequent main body can be made smaller than possible with existing manufacturing methods. This is advantageous in that it reduces the variation in the coefficient of thermal expansion in the main body.

[0018] The smaller the deviation, the smaller the local non-uniformity of the coefficient of thermal expansion, particularly depending on the titanium oxide content. The coefficient of thermal expansion is affected by the heat treatment method carried out during or after temporary heating of the main body, and is locally affected by the titanium oxide content varying according to the particle size and the uniformity of the particle size in the mixed material. Therefore, in order to set a predetermined coefficient of thermal expansion, it is possible to initially set the non-uniformity of the titanium oxide content in the powder to be small, and finally set the coefficient of thermal expansion by a subsequent heat treatment method.

[0019] In yet another embodiment, the soot method can be carried out in an oxygen-deficient state to improve the subsequent heat treatment process, and as a result, the formation of oxygen defects in the silicon oxide (Si2O) produced by this method increases. In this way, the generation of silicon-silicon bonds (Si-Si) increases, adding possible bond angles, increasing the possibility of relaxation at high temperatures, and thus improving the heat treatability.

[0020] In particular, in the soot method, at least one additional substance that covalently bonds can be added to change the physical properties of the first material component. Sodium (Na) is particularly suitable for this. Alternatively, in order to enhance the heat treatability of the main body, fluorine doping can be carried out by treatment with a fluorine-containing gas or liquid.

[0021] In addition to the chemical composition, it is possible to set the particle size of the powder, which can be particularly in the range of 100 nm to 500 μm. The particle size variation can be defined, for example, such that 90% of the particles in a given range are at least half and at most twice the average value.

[0022] Furthermore, the powder can be dried to reduce the OH content to less than 100 ppm, preferably less than 30 ppm, and particularly preferably less than 10 ppm. If the OH content is low, the risk caused by the diffusion of OH during the subsequent sintering process, which results in locally different coefficients of thermal expansion within the body, is minimized. In this case, as a result of the heat treatability being impaired, the curve of the coefficient of thermal expansion also becomes difficult to increase as described above.

[0023] In this case, by reducing the titanium oxide content by 0.1% to 0.5%, it is possible to compensate in advance for the deviation in the level of the coefficient of thermal expansion or the position of the curve of the coefficient of thermal expansion with respect to temperature.

[0024] This method has the advantage that the zero-crossing temperature can be predicted very easily from the titanium oxide content, and thus at least minimize the time-consuming heat treatment method for setting.

[0025] Alternatively, the powder can be moistened to increase the OH content to 700 ppm to 1200 ppm by weight ratio. Thereby, the heat treatability of the body formed by the above manufacturing method can be further improved.

[0026] Therefore, for the first material component, when selecting the OH content of the powder, an optimum value must be found between setting the gradient of the coefficient of thermal expansion due to temperature during heat treatment and the zero-crossing temperature, i.e., setting the absolute value of the coefficient of thermal expansion, and setting the uniformity of the coefficient of thermal expansion of the body.

[0027] The heat treatment required for setting the coefficient of thermal expansion, its gradient, and the zero-crossing temperature can be carried out after or during the temporary heating of the intermediate body in the third method step of manufacturing the body.

[0028] In particular, during the heat treatment, the operation can be carried out at a cooling rate of 0.2 K / h to 20 K / h.

[0029] The coefficient of thermal expansion of the material of the body is set by the manufacturing method according to the present invention so that all the mirrors have a zero coefficient of thermal expansion at a predetermined temperature, so-called zero-crossing temperature. Further, the gradient of the coefficient of thermal expansion with respect to temperature is made as flat as possible. In order to affect the zero-crossing temperature and the gradient of the coefficient of thermal expansion, in addition to the measures already described, other measures can be used.

[0030] In the case of manufacturing a powder having oxygen defects, it is conceivable to sinter the body in oxygen gas, and this oxygen converts the oxygen defects into the normal matrix bond of (Si-O-Si). Since this occurs at the sintering temperature, the matrix has limited fluidity, so that the conversion preferably occurs at a place where local deformation increases, thereby inducing advantageous relaxation in the body.

[0031] Furthermore, during the temporary heating process, a static pressure can be applied to the intermediate body. During so-called sintering, the intermediate body made of powder preformed in advance by pressure or the above method is heated to a temperature close to the melting temperature of the material, so that the bonding between the individual grains of the powder by fusion can be obtained in order to obtain at least a substantially pore-free body.

[0032] In yet another method carried out under static pressure, so-called hot isostatic pressing, a powder or solid, or a preformed intermediate body is combined with static pressure and simultaneous heating, e.g., inside a pressure vessel, to obtain a pore-free body. In the case of a powder, it can be poured into a deformable airtight container so that the static pressure acts only from the outside on the powder or the subsequent body. If an intermediate body already exists, it can be placed directly into the pressure vessel, but the intermediate body must have an airtight outer layer. It is also possible to trap residual bubbles in a body that is already fully sintered.

[0033] Furthermore, at least one functional surface, such as an optically effective surface of an optical element made of a cured composite material of the body, can be reprocessed by a polishing method. The intermediate body can be at least partially manufactured by a 3D printing method.

[0034] In particular, the titanium oxide concentration can vary over the volume of the parts of the intermediate body produced by the 3D printing method. Variations in the titanium oxide concentration can be set by using composite materials with different titanium oxide concentrations. Depending on the method, for each layer, within a layer, or for each deposition of a further composite material, e.g., in droplet form as in the PolyJet method described in more detail below, it is thus possible to set the titanium oxide concentration of the composite material. By mixing the composite materials alternately or continuously for each layer or for each partial deposition within a layer, it is possible to set a predetermined titanium oxide concentration.

[0035] Furthermore, the intermediate body can be manufactured using a mold, in particular it can be printed into the mold by a 3D printing method. The mold can already include an approximate surface shape of the optically effective surface of the optical element to be obtained. In this case, during sintering, a gas-impermeable layer advantageous for subsequent method steps, e.g., hot isostatic pressing, can be formed on the material of the body at the interface with the mold.

[0036] The body of the optical element according to the invention, e.g., a multilayer mirror, can in particular be manufactured by one of the above-described embodiments of the method.

[0037] The body may be characterized in that the OH content of the body material is less than 100 ppm, preferably less than 30 ppm, particularly preferably less than 10 ppm by weight. As a result of this method, thereby, at 20 °C 1.5 ppb / K 2 and 2.3 ppb / K 2 a gradient of the coefficient of thermal expansion of the body material in the range of is obtained.

[0038] Furthermore, the titanium oxide content of the body material can be at least 5% to 15%, particularly 6.7% to 8.5% by weight. As described above, especially in the case of a dry powder mixture, it is possible to set the zero-crossing temperature by reducing the titanium oxide content.

[0039] In yet another embodiment, the body can be formed in layers, and at least the shape of the outer layer can be adapted to the shape of the surface of the body in at least a specific region.

[0040] In the case of a projection exposure apparatus for semiconductor lithography provided with an optical element according to the present invention, the body of the optical element can be formed in layers. There may be non-uniformities in material properties such as the coefficient of thermal expansion within the body. This non-uniformity can be caused by the distribution of material components in the mixed material and / or the manufacturing method. If there is a preferential direction of non-uniformity, such as by a 3D printing method, in a plane parallel to the optically effective surface, it is advantageous if the optical element is arranged in the projection exposure apparatus such that the direction in which the non-uniformity is maximum extends substantially perpendicular to the scanning direction of the projection exposure apparatus. This has the advantage that imaging aberrations caused by the non-uniformity can be at least partially advantageously averaged during the scanning operation.

[0041] In the method according to the present invention, simple manufacturing of complex shapes in combination with setting the coefficient of thermal expansion and the zero-crossing temperature is possible, and there are various parameters that have the opposite effect. The possibilities and scope of the above combination are not exhaustive.

[0042] Yet another method for manufacturing the body of the optical element by an additive method according to the present invention is Preparing a first hybrid material including a first carrier material and a first structural material; Preparing a second hybrid material including a second carrier material and a second structural material; The carrier material includes at least one monomer and / or at least one oligomer, and the structural materials have different compositions; Forming an intermediate by fusing the hybrid materials to polymerize the carrier material; Finishing at least a part of the body by heating the intermediate to thermally bond the structural material and removing the carrier material; and including.

[0043] In this regard, it should be understood that the carrier material is a material that temporarily absorbs the structural material and provides an initially mechanically stable structure for further processing. In contrast, the structural material is a material that remains in the body or forms the body after finishing the body. The above-mentioned initially mechanically stable structure is obtained by polymerization of the monomers and / or oligomers of the carrier material. Since the intermediate is produced by fusing the hybrid materials, it becomes possible to obtain specific desired properties of the intermediate and thus the subsequent body in a specific region. The heating of the intermediate to obtain the body does not necessarily have to be performed in a single step. It is naturally conceivable to first heat the intermediate to such an extent that the formed polymer is removed by combustion, and in the same step, to provide, albeit partially, the first bond between the individual particles of the structural material.

[0044] The solid body can subsequently be produced in a subsequent sintering step. It is obvious that in order to manufacture subsequent optical elements, additional sub-bodies manufactured by the described method, in particular a method different from the conventional method, can also be provided to the body thus obtained.

[0045] The formation of the intermediate can be carried out using a polyjet printing method.

[0046] The polyjet method enables the mixing of mixed materials with each other at any desired settable ratio at any location in the structure of the intermediate. This method is equivalent to the method used in the case of an inkjet printer that can print full colors, usually by setting the mixing ratios of the three primary colors (red, yellow, blue) and black. In the case of the above method, a liquid carrier material containing slurry particles in the form of micro-droplets is applied and cured immediately after application by ultraviolet irradiation. Furthermore, by using the polymerization of the carrier material, a complex intermediate structure can also be easily manufactured.

[0047] In order to obtain the body for the optical element, it is advantageous if at least one of the structural materials contains glass powder. The glass powder can contain, for example, quartz glass, especially glass known under the trade names ULE or Zerodur.

[0048] Furthermore, at least one of the structural materials can contain additives.

[0049] For example, the first structural material can contain only one of the above glasses in powder form, while the second structural material is formed only by appropriate additives in the extreme case. It is also conceivable that the types of additives of the two structural materials are different.

[0050] The structural materials can also have different additive concentrations.

[0051] The additives can include, in particular, the following substances or compounds: titanium, titanium oxide, lithium, aluminum, OH compounds.

[0052] The above additives are particularly suitable for setting the zero-crossing temperature of the thermal expansion coefficient of the material of the resulting body. The effect of titanium is, for example, to enable the setting of the thermal expansion coefficient so that it can be zero or virtually zero at least in a predetermined temperature range. Other additives can, for example, protect the material from embrittlement by electromagnetic radiation.

[0053] This expands the possibility of setting the substance distribution during the production of the intermediate body such that the concentration of the additive in the body corresponds to the temperature distribution of the body that occurs during the use of the optical element.

[0054] In other words, the zero-crossing temperature can be adapted in a specific region such that, for the temperature distribution of the body expected during the operation of the associated projection exposure apparatus, the zero-crossing temperature is, as far as possible, the respective zero-crossing temperature over the entire body. Thereby, in the case of a temperature change near the zero-crossing temperature, it is possible to ensure that only a slight shape change occurs due to the temperature change over most of the volume of the body. Similarly, the optically effective surface can be formed to correspond to the target surface region in the case of the same temperature distribution.

[0055] In addition to focusing on the temperature distribution typical for setting the coefficient of thermal expansion in the body, this temperature distribution can also be varied such that the deviation of the optically effective surface from its target surface region is minimized for a plurality X of possible temperature distributions. In this case, instead of the spatial distribution of the additive in the body being selectively optimized for a specific temperature distribution, an acceptable thermal expansion behavior of the body is ensured over the above temperature distribution, although not completely.

[0056] In an advantageous variant of the invention, the concentration of the additive can decrease as the distance from the side of the body that becomes the optical surface increases.

[0057] The gradient of the concentration can be adjusted, for example, in accordance with the heat flux specific to the material, and thus deformation can be reduced regardless of the specific temperature distribution.

[0058] Furthermore, the concentration of the additive can continue to decrease as the distance from the side of the body that becomes the optical surface to the cooled layer of the body increases.

[0059] This applies, for example, to the case of an additive containing titanium when the optical element including a fluid line for temperature control of the body is cooled at a certain distance from the optically effective surface. The temperature control can be adjusted, for example, to keep the temperature of the body constant below, i.e., on the side of the fluid line opposite to the optically effective surface, regardless of the heat absorbed by the optically effective surface. In that case, the heat transfer coefficient in this region becomes constant compared to the region between the optically effective surface and the fluid line.

[0060] It is also advantageous if the concentration of the additive in the partial region of the body is set such that the coefficient of thermal expansion of the predetermined partial region of the body is greater than that of the remaining part of the body volume.

[0061] This always applies when intentionally thermally deforming the lower region of the body away from the optically effective surface side. This predetermined adjusted deformation extends through the body up to the optically effective surface and, at the same time, no parasitic deformation of the optically effective surface occurs even in the presence of heating of the optically effective surface by absorption and electromagnetic radiation.

[0062] The method according to the invention can be used in particular for the production of optical elements of projection exposure apparatuses for semiconductor lithography.

[0063] The body according to the invention for an optical element is at least partially manufactured by an additive method, and the zero-crossing temperature of the linear coefficient of thermal expansion changes continuously in at least a partial region of the body.

[0064] In other words, the change in the zero-crossing temperature is selected such that no abrupt change occurs in the above partial region of the body. As a result, the corresponding partial region of the body can have locally different coefficients of thermal expansion, but there is no distinct boundary between the regions with different coefficients of thermal expansion. Furthermore, as a result, in the case of a temperature change, the reaction of the body is locally different, but no stress peak occurs at the boundary between the regions with different coefficients of thermal expansion.

[0065] In particular, the change in the zero-crossing temperature exceeds 1 K / mm in the range of 20 °C to 65 °C.

[0066] In an advantageous embodiment of the invention, the zero-crossing temperature that varies at least partially across the body corresponds to the temperature distribution of the body that occurs during use of the optical element.

[0067] By means of the measures described, when there is such a temperature distribution, the body can have a temperature of approximately zero-crossing temperature everywhere. Thereby, as described above, the length change due to heat in the body is minimized. The above change in the zero-crossing temperature in the material of the body can be adapted in particular to the known intensity distribution of the electromagnetic radiation of the optical element, i.e., as a result of a known setting. The corresponding adaptation can also be carried out in the region of the body adjacent to the optically effective surface.

[0068] However, using the above setting of the coefficient of thermal expansion, it is not only possible to minimize the length change due to heat of the material of the body. It is also conceivable to selectively create regions of the body where the coefficient of thermal expansion is large relative to the surrounding region.

[0069] In this case, it is possible to selectively deform the effective surface of the optical element by heating or cooling the corresponding region.

[0070] A projection exposure apparatus for semiconductor lithography that includes an optical element whose body is designed as described is characterized by high robustness with respect to thermal effects.

[0071] Yet another body of an optical element according to the invention, comprising at least one actuator and / or sensor, is characterized in that at least one actuator component of the actuator and / or one sensor component of the sensor are at least incorporated into an additively manufactured partial structure of the body. This has the advantage that the actuator component and / or the sensor component can be arranged close to other functional elements such as the optically effective surface or the flow path of the body. Thereby, it is possible to enable direct detection of the deformation of the optically effective surface, and as a result, the accuracy and, in the case of a thermal sensor, the response time to temperature changes on the optically effective surface are also advantageously improved.

[0072] In particular, the actuator component and / or the sensor component can be a conductive element. The conductive element can be in the form of, for example, an electric wire, particularly a heating wire, or can include conductive particles. The electric wire can be inserted at a predetermined location, for example, during the manufacture of the body, by means of a 3D printing method during the printing process. In the case of the 3D printing method described below, the particles can be directly incorporated into one of the composite materials used for printing and printed at a predetermined location of the body. In yet another variant of the present invention, the actuator component and / or the sensor component can include conductive component parts. It should be understood that the conductive component parts are incorporated into the material of the body without further contact connections, particularly as small plates or short electric wires or conductor portions. The only difference between these and the above-mentioned particles is that they are generally too large to be directly printed because they are considerably larger than the particles. However, of course, there is a possibility of incorporating the component parts into the material of the body during the deposition of two layers by an additive method. For example, it is possible to interrupt the 3D printing for a while, insert the corresponding component parts, and then continue the printing.

[0073] When the component is used as an actuator, it is possible to generate an electric current in the conductive element so that the element is heated by its ohmic resistance. As a result, the material of the body in the surrounding area of the conductive element is also heated and deformed, particularly expanded, so that deformation can be obtained at the desired location of the body. For example, in the case of a heating wire, it is possible to directly galvanically connect the heating wire to a voltage source to generate the required electric current. In the case of using particles or component parts without a galvanic contact connection to the voltage source, there is an option of generating the required electric current by induction. For this purpose, it is also possible to incorporate an induction coil into the body that generates an alternating magnetic field when an AC voltage is applied, thus generating eddy currents in the particles or component parts.

[0074] In yet another advantageous embodiment of the present invention, the actuator component and / or the sensor component includes a magnetic element. These magnetic elements may have a form similar to that of the above-described particles or component parts. Since their magnetic properties and electrical conductivity are not mutually exclusive, they can particularly match the above-described particles or component parts. In the case of a magnetic element, a desired deformation can be achieved by generating a magnetic field in the region of the magnetic element. This can be achieved, for example, by applying a DC voltage to an induction coil near the magnetic element to form a temporally stable magnetic field in the region of the magnetic element, and then the element is subjected to a magnetic force and the surrounding material is deformed. In this case, the induction coil is used like an electromagnet. Therefore, in principle, it is also possible to achieve deformation due to thermal expansion on the one hand and deformation due to magnetic force on the other hand using the same arrangement of the coil and the conductive / magnetic element. When a magnetic element and a conductive element are involved, during the operation of the coil as an induction coil, it is necessary to ensure that the frequency of the applied AC voltage is sufficiently far from the mechanical natural frequency of the body to avoid unnecessary mechanical vibrations of the body.

[0075] When the above element operates as a sensor, there are various possibilities. For example, when using a heating wire, it is possible to measure the current resistance value of the heating wire at a specific time point by utilizing the temperature dependence of the ohmic resistance, and then estimate the temperature of the surrounding area from it. Since the incorporated particles or component parts also exhibit a temperature-dependent behavior of their electrical properties in particular, it is also conceivable in principle to use them as sensor components. For example, the inductance of an induction coil arranged in the region of the particle or component part depends to a certain extent on the magnetic permeability of the adjacent particles or component parts and the surrounding material, and this magnetic permeability depends on temperature. Based on the measurement of the current inductance of the coil, conclusions can be drawn about the temperature in the region of the coil or in the region of the particle or component part.

[0076] Furthermore, the actuator component and / or the sensor component may be a heat conduction or heat generating element. This may be in the form of a heat pipe, a thermocouple, or a copper wire. The heat conduction element may be connected to a heat source and / or a heat sink and used as a thermal actuator. It is similarly possible to simply use the incorporated heat conduction element as an extension of a temperature sensor.

[0077] Yet another method for manufacturing the body of the optical element by an additive method according to the present invention is manufacturing at least a partial body of a predetermined structure of the body in the form of a connection shape by a polyjet method, wherein the hybrid material used for manufacturing the body includes a carrier structure containing at least one monomer and / or oligomer and a structural material containing glass powder heating the body polymerized in the previous method step to thermally bond the glass powder component and burn the polymer sintering the body and including.

[0078] By this method, virtually any desired shape can be manufactured, and the transition portions between the layers formed during printing of the structure are not detectable in the final product.

[0079] Furthermore, two different hybrid materials can be used for manufacturing the body. Thereby, the characteristics of different regions of the body can be adapted to different requirements such as a low coefficient of thermal expansion, high elasticity, or high rigidity.

[0080] In particular, it is possible to manufacture a partial structure including the actuator component and / or the sensor component of the body and the body from two different hybrid materials. Thereby, for example, a connection shape such as the above-described separation element together with its connection element can be manufactured from a first hybrid material having high elasticity. The remaining part of the body can be manufactured from a second hybrid material having high rigidity.

[0081] In particular, the body may comprise a second sub-structure that can be manufactured by conventional manufacturing methods. The individual sub-structures can be interconnected in a form-fitting or material-fitting manner to obtain the body.

[0082] Exemplary embodiments and variants of the present invention will be explained in detail below with reference to the drawings.

Brief Description of the Drawings

[0083]

Figure 1

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Mode for Carrying Out the Invention

[0084] In the following text, the essential components of the microlithography projection exposure apparatus 1 will first be explained by way of example with reference to FIG. 1. The description of the basic design of the projection exposure apparatus 1 and its components should not be understood here as being restrictive.

[0085] One embodiment of the illumination system 2 of the projection exposure apparatus 1 has, in addition to the radiation source 3, an illumination optical unit 4 that illuminates the object field of view 5 of the object plane 6. In an alternative embodiment, the light source 3 can also be provided as a module separate from the rest of the illumination system. In this case, the illumination system does not include the light source 3.

[0086] The reticle 7 disposed in the object field of view 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.

[0087] For the sake of explanation, a Cartesian xyz coordinate system is shown in FIG. 1. The x direction extends perpendicular to the plane of the figure. 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.

[0088] The projection exposure apparatus 1 includes a projection optical unit 10. The projection optical unit 10 functions to image the object field of view 5 onto the image field of view 11 of the image plane 12. The image plane 12 extends parallel to the object plane 6. Alternatively, an angle other than 0° is also possible between the object plane 6 and the image plane 12.

[0089] The structure on the reticle 7 is imaged onto the photosensitive layer of the wafer 13 disposed in the region of the image field of view 11 of the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is displaceable, in particular in the y direction, by a wafer displacement drive 15. On the one hand, the displacement of the reticle 7 by the reticle displacement drive 9 and, on the other hand, the displacement of the wafer 13 by the wafer displacement drive 15 can be performed in synchronization with each other.

[0090] The radiation source 3 is an EUV radiation source. The radiation source 3 emits, in particular, EUV radiation 16, also referred to hereinafter as used radiation, illumination radiation, or illumination light. In particular, the used radiation has a wavelength in the range of 5 nm to 30 nm. The radiation source 3 can be a plasma source such as a laser-produced plasma (LPP) source or a gas-discharge plasma (GDPP) source. This can also be a synchrotron-based radiation source. The radiation source 3 can be a free-electron laser (FEL).

[0091] The illumination radiation 16 emitted from the radiation source 3 is focused by the collector 17. The collector 17 can be a collector having one or more elliptical reflecting surfaces and / or hyperbolic reflecting surfaces. The illumination radiation 16 can be incident obliquely (GI) on at least one reflecting surface of the collector 17, that is, at an incident angle greater than 45° with respect to the direction of the normal to the mirror surface, or normally incident (NI), that is, at an incident angle less than 45°. The collector 17 can be structured and / or coated, firstly, to optimize the reflectivity with respect to the useful radiation and, secondly, to suppress extraneous light.

[0092] Downstream of the collector 17, the illumination radiation 16 propagates through the intermediate focal point of the intermediate focal plane 18. The intermediate focal plane 18 can be the separation point between the radiation source module including the radiation source 3 and the collector 17 and the illumination optical unit 4.

[0093] The illumination optical unit 4 includes a deflection mirror 19 and a first facet mirror 20 arranged downstream thereof in the beam path. The deflection mirror 19 can be a planar deflection mirror or a mirror having a beam influence effect exceeding a pure deflection effect. Alternatively or additionally, the deflection mirror 19 can be in the form of a spectroscopic filter that separates the useful wavelength of the illumination radiation 16 from extraneous light of different wavelengths. When the first facet mirror 20 is arranged in the plane of the illumination optical unit 4 that is optically conjugated to the object plane 6 as the field plane, this facet mirror is also referred to as the field facet mirror. The first facet mirror 20 includes a plurality of individual first facets 21, which are also referred to as field facets hereinafter. FIG. 1 shows only some of the facets 21 as examples.

[0094] The first facet 21 can be in the form of a macroscopic facet, particularly in the form of a rectangular facet, or in the form of a facet having an arcuate edge contour or a partial circular edge contour. The first facet 21 can be in the form of a planar facet or in the form of a convexly or concavely curved facet.

[0095] As is known, for example, from German Patent Application Publication No. 10 2008 009 600, the first facet 21 itself can also be composed of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirror 20 can be embodied in particular as a microelectromechanical system (MEMS system). For details, reference may be made to German Patent Application Publication No. 10 2008 009 600.

[0096] Between the collector 17 and the deflection mirror 19, the illumination radiation 16 travels horizontally, i.e., in the y direction.

[0097] In the beam path of the illumination optical unit 4, a second facet mirror 22 is arranged downstream of the first facet mirror 20. When the second facet mirror 22 is arranged on the pupil plane of the illumination optical unit 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be arranged away from the pupil plane of the illumination optical unit 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US Patent Application Publication No. 2006 / 0132747, European Patent No. 1 614 008, and US Patent No. 6,573,978.

[0098] The second facet mirror 22 includes a plurality of second facets 23. In the case of a pupil facet mirror, the second facet 23 is also referred to as a pupil facet.

[0099] Similarly, the second facet 23 can be a macroscopic facet that may have a boundary, for example, circular, rectangular, or hexagonal, or a facet composed of micromirrors. In this regard, reference may similarly be made to German Patent Application Publication No. 10 2008 009 600.

[0100] The second facet 23 can have a planar reflecting surface or a reflecting surface curved convexly or concavely.

[0101] Therefore, the illumination optical unit 4 forms a dual-facets system. This basic principle is also referred to as a fly-eye integrator.

[0102] It may be advantageous not to arrange the second facet mirror 22 exactly in a plane optically conjugate to the pupil plane of the projection optical unit 10. In particular, the pupil facet mirror 22 can be arranged inclined with respect to the pupil plane of the projection optical unit 10, as described, for example, in German Patent Application Publication No. 10 2017 220 586.

[0103] Using the second facet mirror 22, the individual first facets 21 are imaged onto the object field of view 5. The second facet mirror 22 is the last beam shaping mirror in the beam path upstream of the object field of view 5 or the actual final mirror for the illumination radiation 16.

[0104] In yet another embodiment (not shown) of the illumination optical unit 4, a transfer optical unit, which particularly contributes to the imaging of the first facet 21 onto the object field of view 5, can be arranged in the beam path between the second facet mirror 22 and the object field of view 5. The transfer optical unit can have exactly one mirror or two or more mirrors arranged one after another in the beam path of the illumination optical unit 4. The transfer optical unit can particularly include one or two normal incidence mirrors (NI mirrors) and / or one or two grazing incidence mirrors (GI mirrors).

[0105] In the embodiment shown in FIG. 1, downstream of the collector 17, the illumination optical unit 4 has exactly three mirrors, specifically, the deflection mirror 19, the field facet mirror 20, and the pupil facet mirror 22.

[0106] In yet another embodiment of the illumination optical unit 4, the deflection mirror 19 can also be omitted. In that case, downstream of the collector 17, the illumination optical unit 4 can have exactly two mirrors, specifically, the first facet mirror 20 and the second facet mirror 22.

[0107] The imaging of the first facet 21 onto the object plane 6 by means of the second facet 23 or by using the second facet 23 and the transfer optical unit is generally only an approximate imaging.

[0108] The projection optical unit 10 includes a plurality of mirrors Mi, which are assigned consecutive numbers according to their arrangement in the beam path of the projection exposure apparatus 1.

[0109] In the example shown in FIG. 1, the projection optical unit 10 includes six mirrors M1 to M6. Replacements with 4, 8, 10, 12, or any other number of mirrors Mi are likewise possible. The penultimate mirror M5 and the final mirror M6 each have a passage aperture for the illumination radiation 16. The projection optical unit 10 is a double shielding optical unit. The projection optical unit 10 has a numerical aperture on the image side that is greater than 0.5, may be greater than 0.6, and can be, for example, 0.7 or 0.75.

[0110] The reflective surface of the mirror Mi can be in the form of a freeform surface without an axis of rotational symmetry. Alternatively, the reflective surface of the mirror Mi can be in the form of an aspherical surface with exactly one axis of rotational symmetry of the reflective surface shape. Similar to the mirrors of the illumination optical unit 4, the mirror Mi can have a highly reflective coating for the illumination radiation 16. These coatings can in particular be in the form of multilayer coatings having alternating layers of molybdenum and silicon.

[0111] The projection optical unit 10 has a large object-image offset in the y direction between the y coordinate of the center of the object field 5 and the y coordinate of the center of the image field 11. This object-image offset in the y direction can be approximately the same size as the z distance between the object plane 6 and the image plane 12.

[0112] The projection optical unit 10 can have a particularly anamorphic configuration. In particular, this has different imaging scales βx, βy in the x- and y-directions. The two imaging scales βx, βy of the projection optical unit 10 are preferably (βx, βy) = (+ / -0.25, + / -0.125). A positive imaging scale β means imaging without image inversion. A negative sign of the imaging scale β means imaging with image inversion.

[0113] As a result, the projection optical unit 10 reduces the size in the x-direction, i.e., in the direction perpendicular to the scanning direction, by a ratio of 4:1.

[0114] The projection optical unit 10 reduces the size in the y-direction, i.e., by a factor of 8:1 in the scanning direction.

[0115] Other imaging scales are likewise possible. Imaging scales with the same sign and the same absolute value in the x- and y-directions, for example an absolute value of 0.125 or 0.25, are also possible.

[0116] The number of intermediate image planes in the x- and y-directions in the beam path between the object field 5 and the image field 11 may be the same or may differ depending on the design of the projection optical unit 10. An example of a projection optical unit with different numbers of such intermediate images in the x- and y-directions is known from US Patent Application Publication No. 2018 / 0074303.

[0117] Each of the pupil facets 23 is assigned exactly one of the field facets 21 to form an illumination channel for illuminating the object field 5. Thereby, illumination according to the Koehler principle can be obtained in particular. The far field is decomposed into a plurality of object fields 5 using the field facets 21. The field facets 21 generate a plurality of images of the intermediate focus for the pupil facets 23 assigned to them.

[0118] The field facet 21 is imaged onto the reticle 7 overlappingly by the assigned pupil facet 23 to illuminate the object field of view 5. The illumination of the object field of view 5 is particularly uniform as much as possible. It is preferable that the uniformity error is less than 2%. The field uniformity can be obtained by superimposing different illumination channels.

[0119] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the arrangement of the pupil facets. By selecting the light guiding illumination channels, particularly a subset of the pupil facets, the intensity distribution at the entrance pupil of the projection optical unit 10 can be set. This intensity distribution is also referred to as the illumination setting.

[0120] Similarly preferable pupil uniformity in the region of the defined illumination portion of the illumination pupil of the illumination optical unit 4 can be achieved by redistribution of the illumination channels.

[0121] Further aspects and details of the illumination of the object field of view 5, particularly the entrance pupil of the projection optical unit 10, will be described below.

[0122] The projection optical unit 10 can particularly have a concentric entrance pupil. This can be made accessible. This can also be made inaccessible.

[0123] The entrance pupil of the projection optical unit 10 generally cannot be accurately illuminated using the pupil facet mirror 22. In the case of imaging of the projection optical unit 10 that images the center of the pupil facet mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, it is possible to find the surface where the distance obtained for the pair of aperture rays is minimized. This surface represents the entrance pupil or the surface conjugate to it in the real space. In particular, this surface exhibits a finite curvature.

[0124] In the projection optical unit 10, the position of the entrance pupil may be different in the tangential beam path and the sagittal beam path. In this case, the imaging element, particularly the optical component of the transfer optical unit, should be provided between the second facet mirror 22 and the reticle 7. Using this optical element, the difference in the positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

[0125] In the arrangement of the components of the illumination optical unit 4 shown in FIG. 1, the pupil facet mirror 22 is arranged on a plane conjugate to the entrance pupil of the projection optical unit 10. The field facet mirror 20 is arranged inclined with respect to the object plane 6. The first facet mirror 20 is arranged inclined with respect to the arrangement plane defined by the deflection mirror 19.

[0126] The first facet mirror 20 is arranged so as to be inclined with respect to the arrangement plane defined by the second facet mirror 22.

[0127] FIG. 2 schematically shows a meridian cross section of yet another projection exposure apparatus 101 for DUV projection lithography in which the present invention can similarly be used.

[0128] The design and imaging principle of the projection exposure apparatus 101 are equivalent to the design and procedure described in FIG. 1. The same components are denoted by reference numerals with values increased by 100 from those in FIG. 1. Therefore, the reference numerals in FIG. 2 start from 101.

[0129] Unlike the EUV projection exposure apparatus 1 described with reference to FIG. 1, since the wavelength of the DUV radiation 116 used as the light to be used is large in the range of 100 nm to 300 nm, particularly about 193 nm, refractive, diffractive, and / or reflective optical elements 117 such as lens elements, mirrors, prisms, end plates, etc. can be used for imaging or illumination in the DUV projection exposure apparatus 101. In this case, the projection exposure apparatus 101 essentially includes an illumination system 102, a reticle holder 108 that houses and accurately positions a reticle 107 whose structure is provided and determines the subsequent structure on the wafer 113, a wafer holder 114 that holds, moves, and accurately positions the wafer 113, and a projection lens 110 having a plurality of optical elements 117. The optical elements 117 are held by a mount 118 in a lens housing 119 of the projection lens 110.

[0130] The illumination system 102 supplies the DUV radiation 116 necessary for imaging the reticle 107 onto the wafer 113. A laser, a plasma source, etc. can be used as the source of this radiation 116. The radiation 116 is shaped by optical elements in the illumination system 102 so that the DUV radiation 116 has desired characteristics regarding diameter, polarization, wavefront shape, etc. when incident on the reticle 107.

[0131] In addition to using additional refractive optical elements 117 such as lens elements, prisms, end plates, etc., the configuration of the downstream projection optical unit 101 having a lens housing 119 is basically the same as the configuration described with reference to FIG. 1, and thus will not be described in further detail.

[0132] FIG. 3 shows a flow diagram of a possible manufacturing method of the body of an optical element for semiconductor lithography that can be used, for example, in one of the two apparatuses described in the previous figure.

[0133] In a first method step 31, a mixed material containing at least two material components is produced.

[0134] In the second method step 32, an intermediate is produced from the mixed material, which mixed material comprises at least a first material component that will later form the material of the body, and the mixed material comprises a second material component that serves to mechanically stabilize the intermediate.

[0135] In the third step 33, the body is produced from the intermediate by means of temporary heating and at least partial removal of the second material component. The first material component, which comprises fused silica, in particular fused silica doped with titanium oxide, is supplied to the mixed material as a powder. This can be produced by grinding the starting material such that the physical properties of the powder correspond to the physical properties of the subsequent body, or can be provided such that the desired physical properties of the body are obtained after the manufacturing method according to the invention.

[0136] The tool used for grinding the starting material is advantageously produced from the same material as the material of the first material component or from the material used for the first material component, thereby making it possible to avoid contamination of the first material component due to wear of the tool. Furthermore, the starting material can also be comminuted using a non-contact method such as the ultrasonic method.

[0137] As an alternative, the first material component can be produced by what is known as the soot method, in which sand is first reduced with carbon and the silicon obtained is then reacted with chlorine to form silicon tetrachloride. Subsequently, in a high-temperature pyrolysis, a homogeneous mixture of vaporous silicon tetrachloride, hydrogen, oxygen, and an inert gas is burned using a burner in a cooled combustion chamber. What is first formed in the flame are droplet-shaped silicon dioxide particles, which adhere to one another in chains and form three-dimensional secondary particles by branching. These particles then aggregate to form tertiary particles, which precipitate as a powder in the chamber.

[0138] The burner flame used in the soot method can be intentionally generated in an oxygen-deficient state, and as a result, the formation of oxygen defects in the silicon dioxide (Si2O) generated by this method increases. Thus, the generation of silicon-silicon bonds (Si-Si) increases, adding possible bond angles, increasing the possibility of relaxation at high temperatures, and therefore improving the heat treatability. This facilitates the setting of the physical properties of the body regarding the coefficient of thermal expansion and the above zero-crossing temperature. The coefficient of thermal expansion of the body material is set by the manufacturing method according to the present invention so that all mirrors have a zero coefficient of thermal expansion at a predetermined temperature, the so-called zero-crossing temperature.

[0139] Furthermore, the gradient of the coefficient of thermal expansion with respect to temperature is made as flat as possible. Various measures can be used to affect the zero-crossing temperature and the gradient of the coefficient of thermal expansion. The level of the coefficient of thermal expansion largely depends on the percentage of titanium oxide in the material mainly containing silicon dioxide. The more the titanium oxide content, the smaller the coefficient of thermal expansion of the mixed material, that is, the body, that is, the curve of the coefficient of thermal expansion with respect to temperature shifts in the negative y direction. As a result, at the same time, the zero-crossing temperature of the mixed material shifts to the high-temperature side. It is advantageous to heat-treat the body at a temperature of 900 °C to 1200 °C. On the one hand, the curve of the coefficient of thermal expansion shifts in the positive y direction, that is, upward, and as a result, the zero-crossing temperature decreases. On the other hand, the gradient of the curve decreases.

[0140] It is also conceivable to sinter the body in oxygen gas, and this oxygen converts oxygen defects into the normal matrix bonds of (Si-O-Si). Since this occurs at the sintering temperature, the matrix has limited fluidity, and as a result, the conversion preferably occurs at locations where local deformation increases, thereby inducing relaxation in the body.

[0141] Furthermore, it is conceivable to add a covalently bonding metal in the soot method. In particular, sodium (Na) is suitable for this. Alternatively, in order to enhance the heat treatability of the body, it is possible to dope the powder with fluorine by treatment with a fluorine-containing gas or liquid.

[0142] Alternatively, by operating the flame with excess oxygen, peroxide centers, i.e., regions having Si-O=O-Si bonds, can be formed. By reducing these by sintering in a reducing atmosphere such as a hydrogen atmosphere, normal matrix bonds and water vapor can be formed, and the water vapor can escape before the completion of sintering, particularly when sintering is carried out under reduced pressure or at least a very low water vapor pressure. In addition to a hydrogen atmosphere, it is also possible to carry out sintering in a vacuum or an atmosphere of carbon monoxide (CO) or ammonia (NH3) as an alternative.

[0143] In particular, when the powder has an OH content of 150 ppm to 300 ppm by weight ratio after the soot method, it is possible to make the OH content 700 ppm to 1200 ppm by wetting the powder, and as a result, furthermore, the heat treatability of the body created by the above manufacturing method is improved.

[0144] Alternatively, the powder can be dried to have an OH content of less than 100 ppm, preferably less than 30 ppm, particularly preferably less than 10 ppm. If the OH content is low, the risk caused by the diffusion of OH during the subsequent sintering process, that is, the occurrence of locally different thermal expansion coefficients within the body, is minimized. In this case, as a result of the heat treatability being impaired, the curve of the thermal expansion coefficient also becomes difficult to increase as described above. The deviation in the magnitude of the thermal expansion coefficient can be compensated in advance by reducing the titanium oxide content by 0.1% to 0.5% compared to conventionally manufactured materials. This method has the advantage that the zero-crossing temperature can be predicted very easily from the titanium oxide content, and thus at least minimize the time-consuming heat treatment method for setting the zero-crossing temperature. Therefore, for the first material component, when selecting the OH content of the powder, an optimum value must be found between setting the gradient of the thermal expansion coefficient due to temperature during heat treatment and setting the zero-crossing temperature, i.e., the absolute value of the thermal expansion coefficient, and setting the uniformity of the thermal expansion coefficient of the body.

[0145] In the exemplary embodiments described herein, the intermediate body can be manufactured from a mixed material by a so-called polyjet method equivalent to the inkjet printing method. The intermediate body is formed in layers, and the minimum resolution varies according to the layer thickness created by the printer. The layer thickness is determined on the one hand by the particle size of the material components and, in the case of the polyjet method, by the metering of the liquid mixed material.

[0146] It is advantageous that the titanium oxide concentration of the mixed material used can be reset for each deposition using at least two print heads, thereby enabling the selective setting of the titanium oxide concentration over the volume of the optical element. As a result, it is possible to set different zero-crossing temperatures in various regions of the body, which can be estimated from the temperature distribution within the body that occurs during operation.

[0147] In particular, in the case of the polyjet method, due to the substantially desired configuration of the body, the last layer of the intermediate body can be formed parallel to the subsequent optical active surface.

[0148] Alternatively, to mention some possibilities, the intermediate body can also be created in layers by laser powder bed sintering or stereolithography.

[0149] In each of these methods, and also in the case of still other possible manufacturing methods such as injection molding, conventional molding methods, or embossing methods, a mixed material is utilized. The first material component that will later form the body is the same except for the requirements specific to each method such as the above-mentioned moisture and / or titanium oxide concentration. In contrast, the second material component determines the physical properties required for this method, such as being liquid or solid, or in the case of injection molding, the melting temperature of the important mixed material, and varies greatly.

[0150] As yet another variant, 3D printing can also be carried out directly with a mold in the form of a shell. Thereby, for example, the shape of the surface of the body on which the optically effective surface is formed in a subsequent process of the method can be predetermined. Printing into or onto the shell has the advantage that during the sintering process, an airtight layer required for a subsequent hot isostatic pressing process is already formed at the interface with the shell.

[0151] In the case of the 3D printing method, when the layers are also formed simultaneously with the subsequent optically effective surface, in addition to the vertical stacking, it is also possible to form horizontal stacks in a raster pattern within the vertical layer and parallel to the mirror surface. As a result, non-uniformities in the coefficient of thermal expansion occur in both the printing direction and the direction perpendicular thereto. For example, the direction in which the non-uniformity, which can be determined by measurement, is maximum is perpendicular to the scanning direction of the projection exposure apparatus shown in FIGS. 1 and 2, and thus the effect on the imaging quality is determined by the scanning.

[0152] The intermediate is sintered, whereby, in the described embodiment, the second material component in the form of a polymer burns and the individual grains of the powder of the first material component bond together to obtain the body. Alternatively, the burning of the second material component and the bonding of the grains of the first material component that results in the body can also be carried out in two separate method steps. In the first step, the second material component is burned (pyrolyzed) and the powder grains are already bonded at specific points. In the second step, the body is sintered to produce a pore-free body from the already bonded grains. Furthermore, the removal of the first part of the polymer such as polyethylene glycol from the intermediate can also be achieved by insertion into an aqueous liquid, and the removal of other parts such as polyvinyl butyral can be achieved by subsequent burning (pyrolysis). The two-step method for the removal of various materials of the second material component has the advantage that, as a result of the formation of an open-pore structure after the release of polyethylene glycol, the mass removed by pyrolysis is reduced and it can be removed from deeper layers, so that the wall thickness of the body can be advantageously increased.

[0153] The residual porosity after the sintering process can be closed by hot isostatic pressing (HIP), and for this purpose, it is necessary to hermetically close the surface of the body. This can preferably be done by flowing a hot gas containing an inert gas over the surface.

[0154] Alternatively, the intermediate can also be immersed in a suitable aqueous solution, which only penetrates up to a depth of a few micrometers to 1 mm, and subsequently a gas-tight surface layer is formed that stabilizes at the temperature used during the hot isostatic pressing process as a result of drying or reaction. Instead of the solution, it is also possible to use a mixed glass, for example a melt of sodium silicate, and as a result, it is also possible to form a gas-tight surface layer. After the combustion of the second material component by the above method, it is also conceivable to apply a gas-tight surface layer to the intermediate and omit the sintering of the intermediate. This has the advantage that due to the high pressure during the hot isostatic pressing process, the bonding of the powder of the first material component to obtain a non-porous glass body is achieved at a low temperature. Thereby, it is advantageous that the risk of displacement and / or deformation of the flow path, which is caused by the pressure during the bonding of the powder that also acts on the flow path that may be incorporated in the intermediate and may partially have an inner diameter of several μm, is minimized.

[0155] As described above, the heat treatment for setting the gradient of the heat transfer coefficient and the zero-crossing temperature can also be carried out with a predetermined cooling rate that can be in the range of 0.2 K / h to 20 K / h during the hot isostatic pressing process. A further advantage of the hot isostatic pressing process is that as the use temperature is further away from the melting temperature of the material of the body, the dimensional stability of the material is higher, and as a result, the structure introduced into the body, such as the shape and position of the flow path, is maintained.

[0156] The shrinkage of the body with respect to the intermediate that occurs during sintering and / or hot isostatic pressing due to the bonding of the grains and the release of the second material component is in the range of 5% to 20%, particularly 5% to 10%, depending on the proportion as a percentage of the first material component in the mixed material. It is also possible to compensate for the non-linear shrinkage caused by the non-uniformity of the mixed material or by the method based on tests on the specific shape of the body.

[0157] FIG. 4 shows an optical element according to the invention having a body 130 in the form of mirrors Mx, 117 and having an optical region 134 including three connecting portions 132.1, 132.2, 132.3 and an optically effective surface 131. The body 130 also includes material regions 133.1 to 133.9 obtained at least in part by the manufacturing method described below. These have different compositions of the structural materials used during the manufacture of the material regions 133.1 to 133.9, and it is possible to mix structural materials having different compositions by the manufacturing method described below to produce any desired distribution of titanium oxide in the body 130. The zero-crossing temperature, i.e., the temperature at which the coefficient of thermal expansion of the corresponding region of the body is equal to zero, is determined by the titanium oxide concentration in the body. By the method of the present invention, it is possible to adapt the zero-crossing temperature in the body 130 to the temperature distribution during the operation of the associated projection exposure apparatus. This has the advantage that, when the coefficient of thermal expansion is zero, the body 130 can be operated even if a temperature gradient occurs in the body 130, so that there is no or virtually no deformation of the optically effective surface 131 formed in the body 130 due to a deviation from the set temperature. Therefore, temperature fluctuations of the body 130 do not affect the imaging quality of the projection exposure apparatuses 1, 101 shown in FIGS. 1 and 2.

[0158] FIG. 5 shows a 3D printer 40 used in a method of manufacturing an optical element according to the present invention. This includes an object stage 41 on which the structure of the optical element is printed. The object stage 41 is connected to a guide 46 in the z direction, and as a result, the distance between the object stage 41 and the print head 42 of the 3D printer 40 can be set. The movement range of the object stage 41 along the z-axis corresponds to the maximum thickness of the optical element that can be achieved by printing. In the embodiment shown in FIG. 4, the print head 42 includes two nozzle arrays (not shown) for printing two different hybrid materials. The two nozzle arrays can be operated so that the two hybrid materials can be mixed at any desired mixing ratio at any time, so that the transition of the materials in the structure can be either constant or abrupt. The design and method are equivalent to an inkjet printer. The number of nozzle arrays can be increased virtually as desired, so that additional hybrid materials can be used. The hybrid materials 43, 44 used for printing include a carrier material and a structural material, are liquid, and are thus printable. The structural material is a powder made of glass or other sinterable substances, and usually has a particle size of 50 μm to 150 μm. The hybrid material is determined by the substance used for generating the powder. The carrier material includes monomers and / or oligomers and a photoinitiator, which usually include onium compounds such as aryldiazonium, diaryliodonium, or triarylsulfonium. As already described, the hybrid material of the carrier material and the structural material forms a printable liquid. Since the print head 42 can be moved in the xy plane, the optical element can be printed using substantially the entire object stage 41. A UV light 45 in the form of a curtain is also arranged behind the moving direction of the nozzle array on the print head 42, which has the same width as the nozzle array in the example shown. Thus, as a result of the hybrid materials 43, 44 being polymerized by the UV light 45 immediately after being applied, the structure is formed in layers. The photoinitiator usually initiates cationic polymerization by absorption of light, thereby advantageously assisting and accelerating the polymerization process and usually being destroyed.

[0159] Figure 6 shows a schematic view of the structure 49 printed from the mixed materials 43, 44 before and after polymerization by the UV light 45. The mixed materials 43, 44 each contain a monomer 50, an oligomer 51, and a photoinitiator 52 already described in FIG. 4 as a carrier material. In both mixed materials 43, 44, this carrier material contains different glass powders 53, 54, which have different titanium concentrations according to the present invention. The titanium concentration in the structure 49 determines the zero-crossing temperature, that is, the temperature at which the coefficient of thermal expansion becomes zero, as described above. The printed structure 49 contains both glass powders 53, 54 from the two mixed materials 43, 44. The glass powder 53 is distributed throughout the structure 49, and the glass powder 54 is present only on the left side of the structure 49. This is intended to show the possibility of any desired combination of the two mixed materials 43, 44 in 3D printing. The right side of FIG. 5 shows the structure after polymerization of the monomer 50 and the oligomer 51, and the cross-links generated by the UV light 45 are shown by connecting them to each other with lines. The photoinitiator 52 is destroyed by the UV light 45, and the glass powders 53, 54 remain at the printing positions. This state is called a compacted body and is a solid plastic body having dimensional stability filled with the glass powders 53, 54. In a further process of the process for manufacturing the optical element Mx, 117, the compacted body is heated to about 600°C. At 600°C, the plastic burns, and the glass powder portions dispersed in the plastic sinter together and thus bond to each other, so that a shape with minimal shrinkage is given to the structure. The thing called this sintered body is sintered in a convection furnace or a microwave oven at about 1300°C to obtain an optical element. Depending on the ratio as a percentage of the glass powders 53, 54 in the mixed materials 43, 44, the shrinkage is 5% to 20%, particularly 7% to 15.6%.

[0160] Figure 7 describes a method for manufacturing the body 30 of the optical element Mx, 117.

[0161] In the first method step 61, a first mixed material including a first carrier material and a first structural material is prepared.

[0162] In the second method step 62, a second mixed material including a second carrier material and a second structural material is prepared.

[0163] In the third method step 63, an intermediate is formed by fusing the mixed materials to polymerize the carrier material.

[0164] In the fourth method step 64, at least a part of the body is manufactured by heating the intermediate to thermally bond the structural material and removing the carrier material.

[0165] FIG. 8 shows a body 230 of an optical element in the form of a mirror Mx, 117 that can be used in the projection exposure apparatus shown in FIGS. 1 and 2 according to the first embodiment of the present invention. The mirror Mx, 117 includes a body 230 having an optically effective surface 231. Under the optically effective surface 231 of the body 230, during operation, for example, during operation of the associated projection exposure apparatus, a cooling channel 233 for controlling the temperature of the optical element Mx, 117 is formed. Under the cooling channel 233 of the body 230, an actuator element in the form of a heating wire 234 incorporated by an additive manufacturing method of the body 230 such as 3D printing or stereolithography is arranged. A current is applied to the heating wire 234 via an actuator (not shown), and the heating wire 234 acts as a resistive actuator 241 as a whole. Due to the ohmic resistance of the heating wire 234, a region to be heated in the body 230 is generated, and as a result, thermal expansion of the heated region is caused to reach the optically effective surface 231 and deformation occurs there. By selectively operating and adjusting the temperature distribution of the region of the body 230 that houses the heating wire 234, it is possible to set a predetermined deformation 235 of the optically effective surface 231 using the resistive actuator 241 and correct the imaging error. During temperature control, the cooling channel 233 acts as a heat sink and blocks parasitic heat transfer in the direction from the body 230 toward the optically effective surface 231.

[0166] FIG. 9 shows yet another embodiment of the body 230 of an optical element in the form of mirrors Mx, 117 and includes a cooling channel 233 disposed under the optically effective surface 231 similar to the optical elements Mx, 117 shown in FIG. 8. In contrast to the optical element shown in FIG. 3, instead of the heating wire 234, conductive particles 235 or conductive component parts 236 such as electric wires or plates are incorporated into the body 230. When the body 230 is manufactured by a 3D printer using the polyjet method, the particles 235 can be selectively printed at predetermined positions of the body 230 in one mixed material printed by the 3D printer. In this way, it is possible to intentionally set the concentration of the particles 235 according to the mixing ratio of at least two mixed materials used in the polyjet method. Thereby, it is possible to individually form regions with high concentration, low concentration, or no regions of the particles 235 in the body 230.

[0167] Furthermore, it is also possible to incorporate the component part 236 into the body 230 by inserting the conductive component part 236 during 3D printing using the polyjet method. Alternatively, the component part 236 can also be incorporated into the body 230 using another 3D printing method that can process only one mixed material such as stereolithography. The induction coil 238 is disposed near the particles 235 and the component part 236 within the recess 237 of the body 230. When an alternating current is applied by an actuator (not shown), a current is induced in the particles 235 and / or the component part 236, and thus they are heated by ohmic resistance. As a result, the adjacent regions of the body 230 are also heated, causing a predetermined deformation of the body 230 and thus the optical element 231.

[0168] FIG. 10 shows yet another embodiment of the body 230 of an optical element in the form of a mirror Mx, 117, including a cooling channel 233 disposed below the optically effective surface 231, similar to the optical elements Mx, 117 shown in FIGS. 8 and 9. Further, the body 230 also includes the particles 235 and / or component parts 236 already shown in FIG. 9. Instead of the induction coil 238, the body 230 includes an electromagnet 239, which is disposed immediately adjacent to the particles 235 and component parts 236 within the recess 237 of the body 230, similar to the induction coil 238 shown in FIG. 9. The electromagnet 239 is housed in a receptacle 240 formed in the recess 237 and acts as an electromagnetic actuator 243 together with the magnetizable particles 235 and component parts 236. The electromagnetic actuator 243 causes a predetermined deformation of the optically effective surface 231 to correct the imaging aberration, similar to the thermal actuators 241, 242 described above.

[0169] FIG. 11 describes a method of manufacturing the body 230 of the optical elements Mx, 117.

[0170] In a first method step 251, a predetermined structure of the body 230 is manufactured using at least two different hybrid materials, the hybrid materials including a carrier material containing at least one monomer and / or oligomer and a structural material containing at least one glass powder, and the hybrid materials being different at least in two different glass powders of the structural material.

[0171] In a second method step 252, the body 230 polymerized in the previous method step 251 is heated to thermally bond the glass powder components and burn off the polymer.

[0172] In a third method step 253, the body 230 is sintered.

[0173] The actuator elements 234, 235, 236, 238, 239 and the actuators 241, 242, 243 shown in FIGS. 8 to 10 cause deformation of the body 230 by heating or magnetic force in a specific region of the body 230, which propagates to the optically effective surface 231. This effect is enhanced in the case of the thermal actuators 241, 242 by the large coefficient of thermal expansion of the regions of the incorporated actuator elements 234, 235, 236. In combination with the low coefficient of thermal expansion in the region of the optically effective surface 231 of the body 230, i.e., a zero-crossing temperature of zero or virtually zero, a predetermined deformation by the actuators 241, 242, 243 is maximized and parasitic deformation due to absorption of electromagnetic radiation incident on the optically effective surface is minimized. The coefficient of thermal expansion or the zero-crossing temperature can be varied in any desired manner throughout the body 230 by the manufacturing method described in FIG. 11. The body 230 can alternatively be used as an object stage for measuring equipment or a coordinate measuring instrument and for any other application that requires a surface and / or a surface region with high thermal stability and / or high precision.

Explanation of Signs

[0174] 1 Projection exposure apparatus 2 Illumination system 3 Radiation source 4 Illumination optical unit 5 Object field of view 6 Object plane 7 Reticle 8 Reticle holder 9 Reticle displacement drive 10 Projection optical unit 11 Image field of view 12 Image plane 13 Wafer 14 Wafer holder 15 Wafer displacement drive 16 EUV radiation 17 Collector 18 Intermediate focal plane 19 Deflection mirror 20 Facet mirror 21 Facet 22 Facet mirror 23 Facet 31 First method step 32 Second method step 33 Third method step 30 Body 131 Optically effective surface 132 Connection part 133 Material area 34 Optical region 40 3D printer 41 Object stage 42 Print head 43 Mixed material A 44 Mixed material B 45 UV light 46 X-axis guiding means 47 Y-axis guiding means 48 Z-axis guiding means 49 Structure 50 Monomer 51 Oligomer 52 Photoinitiator 53 Glass powder A 54 Glass powder B 61 Method step 1 62 Method step 2 63 Method step 3 64 Method step 4 101 Projection exposure device 102 Lighting system 107 Reticle 108 Reticle holder 110 Projection optical unit 113 Wafer 114 Wafer holder 116 DUV radiation 117 Optical element 118 Mount 119 Lens housing M1~M6 Mirrors 130 Body 134 Optical region 230 Body 231 Optically effective surface 232 Deformation 233 Cooling channel 234 Heating wire 235 particles 236 component parts 237 recess 238 induction coil 239 electromagnet 240 receptacle for electromagnet 241 resistance actuator 242 induction actuator 243 electromagnetic actuator 251 method step 1 252 method step 2 253 method step 3

Claims

1. A method for manufacturing the body of an optical element (Mx, 117) for semiconductor lithography, comprising: First, generating a mixed material containing at least two material components; Second, manufacturing an intermediate from the mixed material, wherein the mixed material contains at least one first material component that will form the material of the subsequent body, and the mixed material contains a second material component that functions to mechanically stabilize the intermediate; Third, manufacturing the body from the intermediate by means of temporary heating and at least partial removal of the second material component. A method comprising the above steps.

2. The method according to claim 1, wherein the first material component comprises quartz glass powder, particularly quartz glass powder doped with titanium oxide.

3. The method according to claim 2, wherein the quartz glass powder is manufactured by grinding a starting material having predetermined physical properties of the body.

4. The method according to claim 3, wherein the tool for grinding the starting material is made of the material of the first material component.

5. The method according to claim 2, wherein the quartz glass powder is manufactured without contact.

6. The method according to claim 5, wherein the quartz glass powder is manufactured by the soot method.

7. The method according to any one of claims 2 to 6, wherein the titanium oxide content in the powder, per 1 g of sample, has a deviation of less than 5%, preferably less than 0.5%, particularly preferably less than 0.05% from the average titanium oxide content of the body.

8. The method according to claim 6 or 7, wherein the soot method is carried out in an oxygen-deficient state to improve the subsequent heat treatment process.

9. The method according to any one of claims 6 to 8, wherein in the soot method, at least one additional substance is added to change the properties of the first material component.

10. The method according to any one of claims 2 to 9, wherein the particle size of the powder ranges from 100 nm to 500 μm.

11. The method according to any one of claims 2 to 10, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ A method characterized by drying the powder to reduce the OH content to less than 100 ppm, preferably less than 30 ppm, particularly preferably less than 10 ppm.

12. In the method according to any one of claims 2 to 10, A method characterized by wetting the powder to increase the OH content.

13. In the method according to any one of claims 1 to 12, A method characterized by using heat treatment after or during the temporary heating step in the third method step to set the coefficient of thermal expansion, gradient, and zero-crossing temperature of the coefficient of thermal expansion of the material of the body.

14. In the method according to claim 13, A method characterized by applying a cooling rate of 0.2 K / h to 20 K / h during the heat treatment.

15. In the method according to any one of claims 1 to 14, A method characterized by applying a static pressure to the intermediate during the temporary heating step.

16. In the method according to any one of claims 1 to 15, A method characterized by reprocessing at least one functional surface of the body made of the cured composite material by a polishing method.

17. In the method according to any one of claims 1 to 16, A method characterized in that the second material component contains at least one polymer.

18. In the method according to any one of claims 1 to 17, A method characterized in that the intermediate is at least partially manufactured by a 3D printing method.

19. In the method according to claim 18, A method characterized in that the titanium oxide concentration varies across the volume of the parts of the intermediate manufactured by the 3D printing method.

20. In the method according to any one of claims 1 to 19, A method characterized in that the intermediate is manufactured using a mold.

21. In the method according to claims 1 to 20, Preparing a first composite material (43) including a first carrier material and a first structural material; Preparing a second composite material (44) including a second carrier material and a second structural material, In these steps, the first carrier material and the second carrier material contain at least one monomer (50) and / or at least one oligomer (51), the first structural material and the second structural material have different compositions, and further, Forming an intermediate by fusing the first mixed material (43) and the second mixed material (44) and polymerizing the first carrier material and the second carrier material; Finishing at least a part of the main body (30) by heating the intermediate to thermally bond the first structural material and the second structural material and removing the first carrier material and the second carrier material; A method characterized by being an additive method, comprising:

22. In the method according to claim 21, The step of forming the intermediate is performed using a polyjet printing method. A method characterized by this.

23. In the method according to claim 21 or 22, At least one of the first structural material and the second structural material contains glass powder (53, 54). A method characterized by this.

24. In the method according to any one of claims 21 to 23, At least one of the first structural material and the second structural material contains an additive. A method characterized by this.

25. In the method according to claim 24, The first structural material and the second structural material are characterized in that the types of the additives are different. A method characterized by this.

26. In the method according to claim 24 or 25, The first structural material and the second structural material are characterized in that the concentrations of the additives are different. A method characterized by this.

27. In the method according to any one of claims 24 to 26, The additive includes the following substances or compounds: titanium, titanium oxide, lithium, aluminum, OH compounds. A method characterized by this.

28. In the method according to any one of claims 24 to 27, The concentration of the additive in the main body (30) corresponds to the temperature distribution of the main body (30) that occurs during the use of the optical element (117). A method characterized by this.

29. In the method according to any one of claims 24 to 28, The concentration of the additive decreases as the distance from the side that becomes the optical surface (131) of the main body (30) increases. A method characterized by this.

30. In the method according to claim 29, The concentration of the additive continues to decrease as the distance from the side that becomes the optical surface (131) of the main body (30) to the cooled layer of the main body (30) increases. A method characterized by this.

31. In the method according to any one of claims 21 to 30, A method for manufacturing an optical element (Mx, 117) of a projection exposure apparatus (1, 101) for semiconductor lithography, characterized by using this method.

32. An optical element (Mx, 117) for semiconductor lithography having a body, wherein the body is an optical element characterized by being manufactured by the method according to any one of Claims 1 to 31.

33. In the optical element (Mx, 117) according to Claim 32, an optical element characterized in that the OH content of the material of the body is less than 100 ppm, preferably less than 30 ppm, and particularly preferably less than 10 ppm by weight ratio.

34. In the optical element (Mx, 117) according to Claim 32 or 33, an optical element characterized in that the titanium oxide content of the material of the body is at least 5% to 15%, particularly 6.7% to 8.5% by weight ratio.

35. In the optical element (Mx, 117) according to any one of Claims 32 to 34, an optical element characterized in that the body is formed in layers, and at least the shape of the outer layer is adapted to the shape of the surface of the body in at least a specific region.

36. In the optical element (Mx, 117) according to any one of Claims 32 to 35, an optical element characterized in that the optical element is a multilayer mirror.

37. A body (30) of an optical element (Mx, 117), at least partially manufactured by an additive method, wherein the zero-crossing temperature of the linear thermal expansion coefficient changes in at least a partial region, a body characterized in that the change in the zero-crossing temperature is continuous in the partial region of the body (30).

38. In the body according to Claim 37, a body characterized in that the change in the zero-crossing temperature exceeds 1 K / mm in the range of 20°C to 65°C.

39. In the body (30) according to Claim 37 or 38, a body characterized in that the zero-crossing temperature that at least partially changes over the body (30) corresponds to the temperature distribution that occurs during the use of the optical element (117) of the body (30).

40. A body (230) of an optical element (Mx, 117) provided with at least one actuator (241, 242, 243) and / or a sensor, The body is characterized in that at least one actuator component (234, 235, 236) of the actuator (241, 242, 243) and / or one sensor component (234, 235, 236) of the sensor is at least incorporated into an additively manufactured partial structure of the body (230).

41. In the body (230) according to claim 40, the actuator component (234, 235, 236) and / or the sensor component (234, 235, 236) is a conductive element (234, 235, 236), characterized by the body.

42. In the body (230) according to claim 41, the actuator component (234, 235, 236) and / or the sensor component (234, 235, 236) includes at least one heating wire (234), characterized by the body.

43. In the body (230) according to claim 41 or 42, the actuator component (234, 235, 236) and / or the sensor component (234, 235, 236) includes conductive particles (235), characterized by the body.

44. In the body (230) according to any one of claims 41 to 43, the actuator component (234, 235, 236) and / or the sensor component (234, 235, 236) includes a conductive component part (236), characterized by the body.

45. In the body (230) according to any one of claims 40 to 44, the actuator component (234, 235, 236) and / or the sensor component (234, 235, 236) includes a magnetic susceptibility element (235, 236), characterized by the body.

46. In the body (230) according to any one of claims 40 to 45, the actuator component (234, 235, 236) and / or the sensor component (234, 235, 236) includes a heat conduction element, characterized by the body.

47. A projection exposure apparatus (1, 101) for semiconductor lithography, comprising an optical element (Mx, 117) according to claims 32 to 36 and / or an optical element (Mx, 117) having a body according to any one of claims 37 to 46, characterized by the projection exposure apparatus.

48. In the projection exposure apparatus (1, 101) for semiconductor lithography according to claim 47, the body of the optical element (Mx, 117) is formed in layers, there is non-uniformity in material properties within the body, and the optical element is arranged in the projection exposure apparatus (1, 101) such that the direction in which the non-uniformity is maximum extends substantially perpendicular to the scanning direction of the projection exposure apparatus (1, 101). A projection exposure apparatus characterized by this.

49. A method for manufacturing the body (230) of an optical element (Mx, 117) by an additive method, a step of manufacturing at least a partial structure of a predetermined structure of the body (230) by a polyjet method (251), wherein the mixed material used for manufacturing the body (230) includes a carrier structure containing at least one monomer and / or oligomer and a structural material containing glass powder; a step of heating the body (230) polymerized in the previous method step to thermally bond the glass powder component and burn the polymer; a step of sintering the body (230) A method comprising this.

50. In the method according to claim 49, A method characterized by using two different mixed materials for manufacturing the structure of the body (230).

51. In the method according to claim 50, A method characterized by manufacturing a partial structure including the actuator component (234, 235, 236) and / or the sensor component (234, 235, 236) of the body (230) and the body (230) from two different mixed materials.

52. In the method according to any one of claims 49 to 51, A method characterized in that the body (230) includes a second partial structure manufactured by a conventional manufacturing method.

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