Compensation of thermal deformations induced by the operation under thermal control during the manufacturing of optical elements during operation

Abstract

A method for manufacturing an optical element (1) of an optical system, which optical element has a target surface shape (1a) and / or a target optical effect during operation of the optical system, wherein the optical element (1) has an average operating temperature (F), which is controlled by at least one thermal manipulator (2) during operation of the optical system. The invention also relates to an optical element for an optical system and to an optical system for a semiconductor technology device.

Description

Technical Field

[0001] This invention relates to a method for manufacturing an optical element for an optical system, the optical element having a target surface shape and / or a target optical effect during operation of the optical system. Furthermore, this invention relates to an optical element for an optical system and an optical system for a semiconductor technology device.

[0002] The subject matter of German Patent Application No. 102023210727.9 is incorporated herein by reference. Background Technology

[0003] For example, semiconductor technology equipment includes projection exposure equipment for fabricating microstructures or nanostructures for microelectronics or microsystems technologies. To accurately fabricate nanoscale and micrometer-scale structures, the corresponding projection exposure equipment must be able to precisely image the structure contained within a master mask onto a substrate such as a wafer. However, the radiation from the operating light of the projection exposure equipment heats the optical elements within it, potentially causing aberrations. Driven by the current demand for increased throughput, radiation sources are becoming increasingly powerful, especially in EUV projection exposure equipment, thus increasing the power within the optical system. Since even the best coatings for EUV optics cannot achieve near 100% reflectivity, the resulting increase in the amount of power absorbed by the optical elements leads to thermal deformation, resulting in a significant deterioration in the imaging quality of the optical system.

[0004] In the DE 10 2010 030 913 A1 process, attempts were made to predict and compensate for deformation caused by high temperatures during EUV projection exposure equipment operation. However, the optical components of the optical system in projection exposure equipment are typically not continuously illuminated over time. Instead, the operating temperature fluctuates significantly with the operation of the scanner. Therefore, the temperature load on the optical components and the resulting aberrations may vary, especially due to changes in illumination settings and / or imaging of different mask masters. Summary of the Invention

[0005] Therefore, the problem solved by this invention is to develop a method for manufacturing an optical element for an optical system, the optical element having a target surface shape and / or target optical effect during operation of the optical system, such that the optical element reliably has said target surface shape and / or said target optical effect under various usage scenarios of the optical system, especially under different illumination settings. Another problem solved by this invention is to provide advantageous optical elements and advantageous optical systems.

[0006] According to a first teaching of the present invention, a method for manufacturing an optical element for an optical system solves the above-mentioned problems, wherein the optical element has a target surface shape and / or a target optical effect during operation of the optical system, by virtue of having an average operating temperature during operation of the optical system. The optical element is controlled by at least one thermal manipulator, and the method includes the following steps:

[0007] - Determine the average operating temperature of the optical element. The actual surface shape and / or actual optical effect of the optical element at the average operating temperature. The actual surface shape and / or actual optical effect deviate from the average operating temperature. The target surface shape and / or target optical effects; and

[0008] The purpose of processing this optical element is to adjust its operation based on the average operating temperature of the optical element. The determined actual surface shape and / or actual optical effect at the average operating temperature The actual surface shape and / or actual optical effect of the optical element are adapted to the target surface shape and / or target optical effect.

[0009] The optical element can be an optical element used in an optical system in semiconductor technology equipment. For example, the optical element is a reflective optical element, such as a mirror or mask. The optical element may include a substrate having a substrate surface. For example, the substrate may include SiSiC, Schott AG's Zerodur®, or Corning Inc.'s ULE® and / or quartz glass or any other type of glass. Furthermore, the optical element may include a coating. In particular, the optical element includes a coating suitable for reflecting light from the EUV wavelength range (1-20 nm), especially 13.5 nm.

[0010] The optical system can be a projection system for semiconductor technology devices, such as a photolithography lens. The optical system includes at least one optical element. Preferably, the optical system includes multiple optical elements. The optical system may include an optical element configuration for manipulating and / or shaping light to create, magnify, and / or correct images. For example, the optical system may include various optical elements, such as lens elements, mirrors, prisms, and / or filters, which are specifically configured and positioned for the purpose of focusing, deflecting, scattering, and / or filtering light beams.

[0011] During operation of the optical system, the optical element at least substantially possesses the target surface shape and / or the target optical effect. Specifically, during operation of the optical system, the optical element operates at an average operating temperature... The optical element must at least substantially possess a target surface shape and / or a target optical effect. For example, during operation of the optical system, the target surface shape and / or target optical effect of the optical element can be predetermined by optical design. For example, it is conceivable that during operation of the optical system, the target surface shape and / or target optical effect of the optical element at least substantially corresponds to the surface shape or target optical effect according to the basic optical design.

[0012] During operation of the optical system, the optical element has an average operating temperature. During the operation of this optical system, the average operating temperature is... It is controlled by at least one thermal actuator. This at least one thermal actuator controls the operating temperature. The distribution over time t, and selectively used as location. The function of [the system's operating temperature]. During operation of the optical system, and with the aid of at least one thermal manipulator, the operating temperature can be reached and / or maintained at the desired target temperature. For example, the average operating temperature. It at least substantially corresponds to the target temperature. This at least one thermal manipulator is particularly useful for controlling the average operating temperature. This results in the average operating temperature This corresponds at least substantially to the target temperature, specifically to a target temperature ±0.5 K, and particularly ± <0.5 K. For example, one can conceive of this average operating temperature. This corresponds to a target temperature ±0.5 K, specifically ± <0.5 K. For example, the target temperature and / or average operating temperature. Between 25°C and 30°C. Specifically, the average operating temperature during the operation of this optical system is... The temperature is maintained constant by at least one thermal manipulator. For example, the at least one thermal manipulator may be a heater, particularly an IR heater, or a segmented heater or a water-cooled component. Specifically, the thermal manipulator is adapted to locally control the temperature of the optical element such that the temperature distribution is selected to produce the same temperature distribution on the optical element for all various lighting settings. Preferably, the temperature distribution on the optical element may be selected such that the temperature at each location on the optical element is greater than or equal to the maximum temperature produced in the optical element by radiation from a radiation source (e.g., a semiconductor technology device), for one of the lighting settings of the lighting unit and / or for one of the imaging settings of the optical system. During operation of the optical system, particularly the semiconductor technology device containing the optical system, the temperature distribution can be maintained constant over time. For example, electromagnetic radiation can be used to control the temperature of the optical element. The radiation intensity can be selected such that the absorbed radiation intensity distribution on the optical element has a distribution at each location on the optical element that is greater than or equal to the maximum absorbed radiation intensity generated in the optical element, the radiation of which comes from a radiation source for one of the illumination settings for the illumination unit and / or the imaging settings for the optical system, wherein the absorbed radiation intensity distribution remains constant over time, particularly during the operation of the optical system (especially semiconductor technology equipment).

[0013] The method may include determining the optical element at an average operating temperature. The actual surface shape of the optical element. Alternatively or additionally, the method may include determining the optical element at an average operating temperature. The actual optical effect of the optical element at an average operating temperature. The determined actual surface shape and / or determined actual optical effect may deviate, in particular, from the average operating temperature. The target surface shape and / or the target optical effects. For example, determination can be understood as confirmation, measurement and / or calculation or simulation.

[0014] The method also includes processing the optical element, the purpose of which is to adjust the optical element to operate at an average temperature depending on the optical element. The actual surface shape and / or actual optical effect determined below, at the average operating temperature The actual surface shape and / or actual optical effect of the optical element are adapted to the target surface shape and / or target optical effect. The optical element can be based on an average operating temperature... The actual surface shape is determined and processed such that the actual surface shape at least substantially corresponds to the surface shape at the average operating temperature. The target surface shape is defined below. The optical element can be fabricated based on the determined actual optical effects, resulting in an average operating temperature. The actual optical effect at this temperature corresponds at least substantially to the average operating temperature. The target optical effect. For example, the processing of the optical element may include polishing the optical element.

[0015] This method has proven to allow for the fabrication of reliable optical elements with the target surface shape and / or target optical effects in various applications of optical systems. This is due to the average operating temperature of the optical element. The optical element is controlled, particularly kept constant, and reliably maintained at an average operating temperature during its manufacture, thanks to at least one thermal manipulator during operation of the optical system. The target surface shape and / or target optical effects are considered. If no thermal manipulator is present in the optical system, the operating temperature of the optical element is primarily increased by radiation from the radiation source, and the operating temperature may vary depending on different illumination settings, such as adjustments made by the optical system user according to the desired structure. Therefore, heat-induced deformation of the optical element, particularly the optical system, during operation is typically time-dependent. However, the average operating temperature of the optical element... Advantageously, the temperature can be controlled, and in particular maintained, by the assistance of at least one thermal manipulator. This at least one thermal manipulator allows the operating temperature to be modified such that the required correction for thermal deformation becomes insensitive to fluctuations in parameters such as pressure, cooling water temperature, material properties, particularly the zero-crossing temperature (ZCT) of thermal expansion, and / or power. Specifically, the at least one manipulator can be designed so that the corrected temperature distribution is as universally effective as possible for the user during operation. For example, this method allows for targeted reworking of optical elements during manufacturing. The method used to process the optical element can be used to correct the optical element, particularly correcting the surface shape and / or optical effects of the optical element.

[0016] Based on the advantageous construction of the method taught in the first teaching, the optical element operates at an average temperature The actual surface shape and / or actual optical effects of the optical element are determined through simulation. Specifically, the optical element operates at an average temperature of... The actual surface shape and / or actual optical effects can be determined by simulation, without actually needing to set the average operating temperature during the manufacturing of the optical element. In other words, the average operating temperature of the optical element can be determined using simulation. The expected surface shape and / or expected optical effects of the optical element will be determined. For example, the actual surface shape and / or actual optical effects of the optical element can be determined by means of finite element simulation.

[0017] For example, as a basis for simulation, the optical element can first be determined at the measurement temperature T. M Lower deviation from average operating temperature And especially the manufacturing temperature T F Spatial resolution material data. For example, the spatial resolution material data of this optical element can be obtained by measuring the optical element at temperature T. M The optical interference and / or ultrasonic measurements are used to determine this. Specifically, realistic material models can be considered, such as thermal hysteresis, nonlinear expansion characteristics, and / or specifically measured homogeneity and / or inhomogeneity data. For example, the optical element may contain materials with non-zero homogeneous and / or non-homogeneous coefficients of thermal expansion, particularly glass-ceramics such as Zerodur® or titanium-doped quartz glass such as ULE, and / or have other local variations, such as variations in refractive index. For example, the characteristics of the optical element, particularly material properties, can be considered during simulation.

[0018] According to another advantageous construction of the method taught in the first teaching, the optical element operates at an average temperature The determination of the actual surface shape and / or the actual optical effect may include: at at least one measurement temperature T M The measurement of the actual surface shape and / or actual optical effect of the optical element, and at the average operating temperature The interpolation or extrapolation of the actual surface shape and / or actual optical effect of the optical element is then performed. In this case, it is specifically based on the optical element at at least one measurement temperature T. M The measured actual surface shape and / or actual optical effect of the optical element are applied at the average operating temperature. The interpolation or extrapolation of the actual surface shape and / or actual optical effects. In the case of extrapolation, the function values ​​outside the interval can be determined at least approximately based on the known function values ​​within the interval. In the case of interpolation, a continuous interpolation mapping the measured values ​​can be determined based on at least two measured values.

[0019] For example, at the first measurement temperature T M1 and at least one second measuring temperature T M2 The actual surface shape and / or actual optical effect of the optical element are measured at the first measurement temperature T. M1 and the second measured temperature T M2 The actual surface shape and / or actual optical effect of the optical element measured below can be interpolated or extrapolated to the optical element at the average operating temperature T. X̅ The actual surface shape and / or the actual optical effect. Specifically, the at least one measuring temperature T M Deviation from this average operating temperature For example, one might imagine that at the first measurement temperature T... M1 The actual surface shape and / or actual optical effect of the optical element are measured at the first measurement temperature T.M1 The temperature is 22℃ + 5K; and at the second measurement temperature T M2 During the measurement, the second measuring temperature T M2 The initial temperature is 22°C + 10K. Starting from this, it can be interpolated to, for example, 22°C + 7K or extrapolated to 22°C + 12K. For example, the at least one measuring temperature T can be set using a measuring device containing at least one thermal manipulator. M The optical element is heated (preferably only temporarily) to at least one measuring temperature T by means of the thermal manipulator. M Additionally, it can be considered that at least one temperature T should be measured. M To manufacture temperature T F .

[0020] According to another advantageous construction of the method taught in the first teaching, the optical element operates at an average temperature The determination of the actual surface shape and / or actual optical effects at the average operating temperature can be included in the determination of the actual surface shape and / or actual optical effects at the average operating temperature. The actual surface shape and / or actual optical effect of the optical element are measured. For example, it is conceivable that the actual surface shape and / or actual optical effect of the optical element corresponds to the average operating temperature. The measurement is performed at ambient temperature. Therefore, the environment in which the measurement is conducted (e.g., a cleanroom) can be heated to the average operating temperature. .

[0021] Alternatively, it can be conceivable that the actual surface shape of the optical element and / or the actual optical effect at the average operating temperature The measurement is performed using a suitable measuring device. For example, the measuring device may include at least one thermal manipulator, wherein the optical element is preferably heated only temporarily to its average operating temperature with the assistance of the thermal manipulator. For example, it is conceivable that the measuring device includes an optical heat source, such as a heater, particularly an IR heater, similar to an oven or bath with controllable water temperature. The optical element can be heated by means of the measuring device to achieve an average operating temperature. Specifically, the thermal manipulator of the optical system is regenerated as much as possible in the measuring device. Furthermore, the measuring device may include measuring equipment, particularly measuring sensors, for measuring the surface shape of the optical element and / or measuring the optical effect of the optical element.

[0022] The surface shape and / or optical effect of the optical element can be determined at the average operating temperature of the optical element. Measurements are performed simultaneously with heating, for example, via an IR heater. Alternatively, it is conceivable to utilize an actuated and / or de-actuated thermal actuator to perform the corresponding measurements, thus allowing differences between measurements to affect the optical element, particularly its surface. The surface shape of the optical element can be measured absolutely or relative to a reference surface. Specifically, the measuring apparatus may include measuring devices for measuring the surface shape of the optical element absolutely or relative to a reference surface. For example, measurements can be performed relative to a reference surface, and the machining of the optical element may involve machining the differences relative to the reference surface into the surface of the optical element. For example, this process is repeated until convergence, i.e., until the measured surface corresponds to the reference surface.

[0023] According to another advantageous construction based on the method taught in the first teaching, it is possible to manufacture at a temperature T F The optical element is then processed at a temperature of T. F Deviation from average operating temperature More than 0.5K, preferably more than 1K, even more than 2K, and particularly preferably more than 5K. Additionally, it is conceivable that the manufacturing temperature T... F With average operating temperature The tolerance can be 10 to 20 K. For example, the manufacturing temperature T... F It can be at room temperature. For example, the manufacturing temperature T. F The temperature is 22°C. For example, the average operating temperature can be set during the manufacturing of the optical element only during the determination of its surface and / or optical effects, particularly during measurement. Specifically, the optical element can be repeatedly tested at an average operating temperature. The determination of the actual surface shape and / or actual optical effects, especially at the manufacturing temperature T. F The purpose of processing this optical element is to achieve an average operating temperature. The actual surface shape and / or actual optical effect of the optical element are adapted to the target surface shape and / or target optical effect.

[0024] According to another advantageous construction based on the method taught in the first teaching, it is possible to achieve an average operating temperature. The optical element is then processed. For example, it is conceivable that the optical element operates at a temperature corresponding to the average operating temperature. The processing is carried out at ambient temperatures. Therefore, the environment in which the processing is performed (e.g., a cleanroom) can be heated to the average operating temperature. Thus, the average operating temperature This can be set during the manufacturing process of the optical element. This allows the optical element to be manufactured directly with compensation. Furthermore, due to the expected average operating temperature... The optical element is processed directly, eliminating the need to wait for temperature control for measurement purposes and preventing inaccuracies caused by incomplete preheating due to insufficient waiting time. However, it should be noted that all processing verification measurements must also be performed at the average operating temperature. The following will proceed.

[0025] According to another advantageous configuration of the method taught in the first teaching, the method may include determining the optical element at an average operating temperature. The actual surface shape and / or actual optical effect of the optical element at the average operating temperature The method may include determining the difference between the target surface shape and / or the target optical effect. For example, the method may include determining the optical element at an average operating temperature. The actual surface shape and / or the actual optical effect of the optical element at the average operating temperature The method addresses the deviation between the target surface shape and / or the target optical effect. Specifically, the method may include determining the required surface correction for the optical element at an average operating temperature. The actual surface shape and / or the actual optical effect are adapted to the optical element at the average operating temperature. The target surface shape and / or the target optical effect. Specifically, the fabrication of the optical element may depend on the average operating temperature of the optical element. The actual surface shape and / or the actual optical effect of the optical element at the average operating temperature The determined difference between the target surface shape and / or the target optical effect. For example, it is conceivable that the method includes determining compensation that improves the objective function for optimizing the optical effect (particularly aberration state) of the optical element (particularly the optical system), relative to the uncompensated state, such as the expected change in surface shape resulting from temperature differences determined by opposite signs.

[0026] In another advantageous embodiment of the method according to the first teaching of the invention, the method may include partially compensating for the differences between the actual surface shape and the target surface shape and / or the actual optical effect and the target optical effect by means of a correction member and / or at least one additional manipulator. Specifically, the at least one additional manipulator may be a rigid body manipulator. For example, it is conceivable that the differences can be partially corrected by a correction member, such as a mask master or semiconductor substrate stage available in an optical system, and / or at least one additional manipulator (which, for example, causes rigid body movement and / or deformation of optical elements).

[0027] The purpose of fabricating this optical element is to achieve an average operating temperature. The process involves adapting the actual surface shape and / or actual optical effect of the optical element to a target surface shape and / or target optical effect. This process can be considered to partially compensate for the differences between the actual surface shape and the target surface shape and / or the actual optical effect and the target optical effect by means of a correction component and / or at least one additional manipulator. For example, it is conceivable to calculate a predefined objective function based on one or more residual error images and determine the required compensation in the optical element, particularly surface variations, in a manner that at least an improvement in the objective function is obtained.

[0028] According to a second teaching of the present invention, the aforementioned problems are solved by a method for manufacturing an optical element for an optical system, the optical element having a target surface shape and / or target optical effect during operation of the optical system, and the optical element having an average operating temperature. The optical system is controlled by at least one thermal manipulator during operation, and the method includes the following steps:

[0029] - Determine the manufacturing temperature T of this optical element. F The actual surface shape and / or actual optical effects;

[0030] -Due to manufacturing temperature T F With average operating temperature temperature difference between To determine the actual surface shape and / or changes in the actual optical effect of the optical element; and

[0031] The purpose of fabricating this optical element is to operate at an average temperature. The method by which the actual surface shape and / or actual optical effect of the optical element is adapted to the target surface shape and / or target optical effect depends on the manufacturing temperature T. F The actual surface shape and / or actual optical effect determined below, and depending on the average operating temperature With manufacturing temperature T F temperature difference between The determined variations in the actual surface shape and / or actual optical effects.

[0032] The method may include determining the optical element at a manufacturing temperature T. F The actual surface shape of the optical element at a manufacturing temperature T. Alternatively or additionally, the method may include determining the optical element at a manufacturing temperature T. F The actual optical effects under the specified conditions. Specifically, the manufacturing temperature T. F Deviation from average operating temperature This method can further incorporate the effect of manufacturing temperature T. F With average operating temperature temperature difference between This involves determining the variation in the actual surface shape of the optical element. Alternatively or additionally, the method may include adjustments based on the manufacturing temperature T. F With average operating temperature temperature difference between To determine the changes in the actual optical effect of the optical element.

[0033] The method further includes fabricating the optical element, the purpose of which is to achieve an average operating temperature. The actual surface shape and / or actual optical effect of the optical element are then adapted to the target surface shape and / or target optical effect. The fabrication of the optical element may depend on the manufacturing temperature T. F The actual surface shape and / or the actual optical effect determined below, and the factors depending on the average operating temperature. With manufacturing temperature T F temperature difference between The determined changes in the actual surface shape and / or the actual optical effect.

[0034] According to the advantageous construction of the second aspect of the method, due to the manufacturing temperature T F With average operating temperature temperature difference between Determining the variation of the actual surface shape and / or actual optical effect of the optical element includes: the optical element at manufacturing temperature T F The actual surface shape and / or actual optical effect of the optical element at the average operating temperature Determining the difference between the target surface shape and / or the target optical effect. Specifically, the method may include determining the required surface modification, the purpose of which is to adjust the optical element at an average operating temperature. The actual surface shape and / or actual optical effect are adapted to the optical element at the average operating temperature. The target surface shape and / or target optical effects.

[0035] According to another advantageous configuration of the second aspect of the method, the actual surface shape and / or changes in the actual optical effect of the optical element are determined based on a mathematical model used to determine local deformation under temperature variations. For example, the method may include determining the optical element at an average operating temperature based on simulation calculations. The surface shape and / or optical effects of the optical element at the manufacturing temperature T F A comparison of the actual surface shape and / or actual optical effects under different operating conditions is performed. To determine the changes in the actual surface shape and / or actual optical effects of the optical element, the optical element can be simulated at an average operating temperature. The surface shape and / or optical effects of the optical element are determined, particularly through finite element simulation. In other words, the optical element's performance at its average operating temperature... The desired surface shape and / or desired optical effects can be determined by simulation without needing to set the average operating temperature. Similarly, in this case, for example at manufacturing temperature T... F Optical interferometry and / or ultrasonic measurements of optical components can initially be performed based on simulations to determine spatially resolvable material data. These simulations can be based on the usage scenario that generates a static temperature distribution within the optical component. Then, mathematical models, particularly finite element simulations, can be used to determine the average operating temperature of the optical component. The surface shape below. For example, in this case, one can also derive information about the optical element at the average operating temperature. The conclusion regarding the optical effects is as follows. It can be assumed that this optical element operates at an average temperature... Optical effects, such as optical aberrations, can be determined by simulation, especially computation.

[0036] For example, it is conceivable that the method according to the first and / or second teachings includes determining compensation, which improves the objective function for optimizing the optical effects (especially aberration states) of the optical element (especially the optical system), relative to the uncompensated state, such as the expected change in surface shape resulting from temperature changes determined by the opposite sign.

[0037] The methods described in the first and / or second teachings may include the calculation of temperature distribution within the optical element. For example, simulation allows for the calculation of the average temperature distribution generally present within the optical element based on predicted operation of the optical element. From this, surface deformation that must be considered during the manufacture of the optical element can be calculated. This method may include the calculation of surface deformation of the optical element and / or the extraction of required surface corrections. In this case, local variations in material parameters within the optical element, such as changes in refractive index and / or coefficients of thermal expansion, can be considered. In particular, if the material of the optical element (e.g., Zerodur®) exhibits thermal hysteresis, the temporal distribution of temperature and deformation during operation of the optical element can be considered, at least partially, when selecting the optimal compensation for operation.

[0038] In another advantageous embodiment of the method according to the second teaching of the invention, the method may include partially compensating for determined variations in the actual surface shape and / or actual optical effects of the optical element by means of a correction member and / or at least one additional manipulator. Specifically, the at least one additional manipulator may be a rigid body manipulator. For example, it is conceivable that the variations can be partially corrected by means of a correction member, such as a mask master or semiconductor substrate stage available in an optical system, and / or at least one additional manipulator, which, for example, causes rigid body movement and / or deformation of the optical element.

[0039] The optical element is fabricated (its purpose is to operate at an average temperature). The actual surface shape and / or actual optical effect of the optical element (adapted to the target surface shape and / or target optical effect) can be partially compensated for by means of the correction member and / or the at least one additional manipulator. For example, it is conceivable to calculate a predefined objective function based on one or more residual error images and to determine the required compensation in the optical element, particularly the surface variation, in a manner that at least improves the objective function.

[0040] According to the advantageous configuration of the method taught in the second aspect of the invention, at a manufacturing temperature T F The optical element can be processed at the following temperature. For example, the manufacturing temperature T... F Deviation from average operating temperature The temperature is above 0.5K, preferably above 1K, even better than 2K, and exceptionally good than 5K. Additionally, it is conceivable that the manufacturing temperature T... F With average operating temperature The tolerance can be 10 to 20 K. For example, the manufacturing temperature T... F It can be at room temperature. For example, the manufacturing temperature T. F The temperature is 22°C. Specifically, the optical element can be repeatedly tested at its average operating temperature. Determining the actual surface shape and / or actual optical effects at the manufacturing temperature T; and at the manufacturing temperature T F The purpose of processing this optical element is to achieve an average operating temperature. The actual surface shape and / or actual optical effect of the optical element are adapted to the target surface shape and / or target optical effect.

[0041] According to an advantageous configuration of the method taught in the first or second invention, the method may include determining the optical effects of the optical system. Specifically, the method may include determining the aberrations and / or wavefront of the optical system. The method may include determining the optical element at an average operating temperature in a manner dependent on the determined optical effects of the optical system. The target surface shape and / or target optical effect are considered. For example, it is conceivable that, in order to determine the target surface shape and / or target optical effect of the optical element, particularly to determine the required surface correction of the optical element, specific or all optical elements, degrees of freedom, and / or manipulators are considered. For example, this method can be used to reduce thermally induced aberrations during the operation of the optical system. For example, selected or all manipulators of the optical system can be considered in the optimization. Specifically, this includes thermal manipulators, by means of which the temperature of the optical element can be adapted during operation. For example, a direct result of this concept is that all manipulators are separated from the travel of the mean absolute value compensation during operation, and thus the travel can be used to improve the correction effect.

[0042] Specifically, this method can be used to account for average deformation in the surface design of optical elements, and therefore for compensation of thermal aberrations. In this case, compensation is not limited to a specific optical element; instead, thermally induced aberrations can be corrected on one or more other optical elements. In other words, it is not necessary to correct the error on the same optical element where the error occurred. The optical element is fabricated (its purpose being to operate at an average temperature...) Adapting the surface shape and / or optical effects of optical elements to the target surface shape and / or target optical effects can, for example, take into account partial aberration compensation already implemented within the optical system via at least one correction member and / or the at least one manipulator. For example, it is conceivable that the method includes determining compensation that improves an objective function used to optimize the aberration state of the optical system with optical elements relative to an uncompensated state. In principle, details of individual optical systems and / or optical elements, such as material parameters like ZCT and / or reflectivity, can be considered to reduce performance fluctuations.

[0043] According to a third teaching of the present invention, an optical element for an optical system solves the aforementioned problems, wherein the optical element has a target surface shape and / or a target optical effect during the operation of the optical system, by means of the fact that the optical element at a measurement temperature T M Especially the manufacturing temperature T F Below, having a first surface shape, and at an average operating temperature The optical element has a target surface shape and / or target optical effect, wherein the optical element has an average operating temperature controlled by at least one thermal manipulator during operation of the optical system. Specifically, the optical element is manufactured according to the method taught in the first or second invention.

[0044] According to the fourth teaching of the present invention, the aforementioned problem is solved by an optical system for a semiconductor technology device, the optical system comprising: at least one optical element according to the third teaching, and at least one control for the average operating temperature of the optical element. Thermal manipulator. For example, the semiconductor technology equipment can be a projection exposure device, a wafer inspection device, or a mask master inspection device.

[0045] Based on the advantageous construction of the optical system taught in the fourth teaching, a predetermined state is provided, wherein the average operating temperature of the optical element is... and the average operating temperature of at least one other optical element The aberrations are at least 1K apart from each other, and have at least substantially the same temperature as the optical element and the at least one other optical element, resulting in a reduction of at least one aberration by at least 20%, preferably at least 25%, and particularly at least 30%.

[0046] For example, at least one aberration may be distortion, focusing error, astigmatism, coma (asymmetric error), a specific value in the wavefront expansion according to Zernike polynomials, and / or the root mean square (RMS) value of the wavefront deviation, such as field dependence. Specifically, the aberration may be Zernike RMS5 and / or, depending on the use of semiconductor technology devices for a predetermined combination of illumination and structure, distortion (overlap), and / or target / actual deviation of the focus. Furthermore, this may be a stray light contribution (flare). The at least two optical elements may be, in particular, the first and last optical elements in an optical system, and / or at least have a first optical element with nearly perpendicular incidence and preferably a largest optical element with grazing incidence.

[0047] The exemplary constructions of the invention described above in this specification should also be understood as being disclosed in all combinations thereof. Individual features of each teaching can be combined with any or all desired features of the other teachings in each case. Specifically, features (particularly steps) of a method according to a first teaching can be combined with features (particularly steps) of a method according to a second teaching. For example, in a measurement-based method, one can start with an actual surface that is already very close to its optimal design state due to simulation-based correction or fabrication under heated conditions. Such a combination allows for reduction of errors that may occur in the process chain. Another possible combination is to assist simulation-based correction by measurement, using measurements as sampling points for interpolation, extrapolation, or simulation calibration. This is particularly interesting when the desired operating state cannot be obtained through measurement.

[0048] Further construction and advantages of the invention will be explained with reference to the accompanying drawings, which describe several exemplary embodiments of the invention in detail below. Attached Figure Description

[0049] Exemplary embodiments and variations of the invention will now be described in detail with reference to the accompanying drawings. Various aspects of the invention will be better understood from the following detailed description taken in conjunction with the accompanying drawings. The drawings are schematic and simplified; they show only details to improve understanding of the claims, while other details are omitted. The same reference numerals are always used for the same or corresponding parts. Individual features of each aspect may, in every case, be combined with any or all features of other aspects. These and other aspects, features, and / or technical effects will become clear from the accompanying drawings described below, and will be illustrated by the drawings themselves, wherein...

[0050] Figure 1a , 1b This shows the manufacturing temperature T F and operating temperature T B The optical element is manufactured using methods according to existing technology;

[0051] Figure 2a , 2b This shows the manufacturing temperature TF and operating temperature T B The optical element below, which has been manufactured according to the method taught in the first or second invention; and

[0052] Figure 3 The method shown is used to determine the average operating temperature of an optical element within the scope of the first teaching. A measuring device for the surface shape and / or optical effects of a surface. Detailed Implementation

[0053] Figure 1a This illustrates an optical element 1' designed as an EUV reflector from existing technology. The optical element 1' is manufactured at a temperature T of approximately 22°C. F Manufacturing at the following temperature. Optical element 1' is manufactured at manufacturing temperature T. F The target surface shape 1a' is present below. Although the surface shape of the optical element 1' is optimally polished relative to the designed surface within the process range, however... Figure 1b As shown, during operation of the optical system using optical element 1', the surface shape changes due to thermal deformation in the high-temperature region (brighter region). At an operating temperature T > 22°C (e.g., 30°C) B Below, the optical element 1' has a surface shape 1b' that deviates from the target surface shape 1a'.

[0054] Optical element 1 is shown in Figure 2a Manufacturing temperature T F Place, and in Figure 2b Average operating temperature T B The element is manufactured according to the method taught in the first or second invention. Although optical element 1 is manufactured at a temperature T... F The optical design during manufacturing results in a deviation from the target surface shape, but optical element 1 operates at an average temperature T. B The target surface shape 1a is provided below. The manufacturing process has taken into account the average operating temperature T. B With manufacturing temperature T F The thermal deformation caused by the difference between them.

[0055] For example, optical element 1 is manufactured according to a method for manufacturing optical elements of an optical system, wherein the average operating temperature of the optical element during operation of the optical system is controlled by at least one type of thermal manipulator 2. The method comprises: determining the optical element 1 at a manufacturing temperature T, having a target surface shape and / or target optical effect. F The actual surface shape 1b and / or actual optical effects are determined by the manufacturing temperature T. F With average operating temperature temperature difference between The variation of the actual surface shape 1b and / or actual optical effect of the optical element 1; and the fabrication of the optical element 1, the purpose of which is to adapt the actual surface shape 1b and / or actual optical effect of the optical element 1 to the average operating temperature. The target surface shape 1a and / or target optical effects are determined by the manufacturing temperature T. F The determined actual surface shape 1b and / or actual optical effects, and the factors depending on the average operating temperature With manufacturing temperature T F temperature difference between The determined variations in the actual surface shape 1b and / or the actual optical effects.

[0056] In this case, based on the mathematical model used to determine local deformation under temperature changes, the actual surface shape 1b of the optical element 1 and / or the change in actual optical effect are determined. For example, it is conceivable that the method includes the calculation of temperature distribution, the calculation of deformation, and / or the extraction of the required surface correction.

[0057] To determine the temperature distribution using the thermal equation (1), for example, the thermal coupling with the surrounding environment of the optical element 1 and / or the thermal material properties are determined. Based on the power incident on the optical element 1, the absorbed power at each location on the surface of the optical element 1 can be calculated using the material properties. This gives rise to the source of the thermal equation. In this case, The value is zero. Environmental factors surrounding optical element 1, such as air or other gases, pressure, distance from potentially adjacent components and / or components in direct contact with the optical element, particularly contact surfaces and materials, allow the thermal boundary conditions of thermal equation (1) to be determined according to equation (2). Additionally, thermal material parameters of the optical element, such as heat capacity c, thermal conductivity λ, and density ρ, are required.

[0058] To solve the equation, the 3-D space can be discretized using, for example, the finite element method (FEM). As for location... Temperature distribution as a function of time t The heat equation is given by the following formula.

[0059] (1)

[0060] Where thermal conductivity is and volume source Due to surface stress The boundary conditions also apply to all surface points on the optical element. :

[0061] (2)

[0062] in Let μ be the temperature of the adjacent material and μ be the heat transfer coefficient. It is the derivative in the direction of the surface normal. The change in heat due to thermal radiation is not explicitly listed here; however, it can generally be considered.

[0063] The relative volume change of each volume unit can be determined based on temperature and / or temperature distribution and by means of the coefficient of thermal expansion. Thus, the equilibrium point of mechanical forces due to mechanical boundary conditions and temperature gradients is determined by means of material parameters such as density, Young's modulus, and / or Poisson's number. Therefore, deformation is obtained at each point in optical element 1. In the case of a reflector, the optical surface... The points on the surface are particularly related to optical effects.

[0064] The design of the surface must be modified to a degree suitable for use on optical surfaces. Each position The calculated deformation along the normal direction is used to determine this. In this case, one option is to eliminate the inverse deformation. However, it is generally more advantageous to first consider the available manipulators: if the rigid body degrees of freedom of the optical element have multiple manipulators, it may be advisable to first correct the calculated surface deformation. Then, only the surface of the remaining parts is etched away.

[0065] Alternatively, it is conceivable that optical element 1 is manufactured according to a method for manufacturing optical elements for an optical system, wherein, according to the first teaching, the average operating temperature of the optical element is controlled by at least one thermal manipulator 2 during operation of the optical system. The target surface shape and / or target optical effect are present. For example, the method includes determining the optical element 1 at an average operating temperature. The actual surface shape 1b and / or actual optical effects, wherein the optical element 1 at the average operating temperature The actual surface shape 1b and / or actual optical effects deviate from the average operating temperature. The target surface shape 1a and / or target optical effect; and the processing of the optical element 1, the purpose of which is to achieve the target surface shape 1a and / or target optical effect at an average operating temperature. The actual surface shape 1b and / or actual optical effect of the optical element 1 are adapted to the target surface shape 1a and / or target optical effect, in a manner that depends on the average operating temperature of the optical element 1. The actual surface shape 1 and / or the actual target optical effect. In this case, for example, such as Figure 3 As shown, the optical element 1 is measured at its average operating temperature using measuring device 3. The actual surface shape 1b and / or actual optical effects are shown below.

[0066] Figure 3 The diagram shows the method for determining the average operating temperature of optical element 1. The measuring device 3 measures the actual surface shape 1b and / or the actual optical effect. The measuring device 3 includes a thermal manipulator 2, wherein the optical element 1 is temporarily heated to its average operating temperature during its manufacturing process by means of the thermal manipulator 2. For example, the thermal manipulator 2 is an IR heater. Furthermore, the measuring device 3 includes a measuring instrument 4, specifically a measuring sensor, for measuring the surface shape 1a of the optical element 1. When at the average operating temperature... When the optical element 1 is heated, the surface shape 1a of the optical element 1 is measured simultaneously. It is also envisioned that the corresponding measurement is performed using the actuated and de-actuated thermal manipulator 2, so that the difference between the measurements can act on the optical element 1, especially on the surface 1a of the optical element 1.

Claims

1. A method for generating an optical element (1) for an optical system, the optical element having a target surface shape (1a) and / or a target optical effect during operation of the optical system. Its features are: The optical element (1) has an average operating temperature controlled by at least one thermal manipulator (2) during the operation of the optical system. (2) The method includes the following steps: - Determine the optical element (1) at the average operating temperature The actual surface shape (1b) and / or actual optical effect of the optical element (1) at the average operating temperature The actual surface shape (1b) and / or the actual optical effect deviate from the average operating temperature. The surface shape of the target (1a) and / or the optical effects of the target; as well as - The optical element (1) is processed to achieve a temperature that depends on the average operating temperature of the optical element (1). The actual surface shape (1b) and / or actual optical effect of the optical element (1) are determined in such a way that the actual surface shape (1b) and / or actual optical effect are adapted to the average operating temperature. The surface shape of the target (1a) and / or the optical effect of the target.

2. The method as described in claim 1, Its features are: The optical element (1) was determined through simulation at its average operating temperature. The actual surface shape (1b) and / or the actual optical effect.

3. The method as described in claim 1 or 2, Its features are: At this average operating temperature The determination of the actual surface shape (1b) and / or the actual optical effect of the optical element (1) includes at least one measurement temperature T. M The following measurements were taken of the actual surface shape (1b) and / or the actual optical effect of the optical element (1), and at the average operating temperature. The interpolation or extrapolation of the actual surface shape (1b) and / or the actual optical effect of the optical element (1) is then performed.

4. The method as described in any one of claims 1 to 3, Its features are: At this average operating temperature The determination of the actual surface shape (1b) and / or the actual optical effect of the optical element (1) includes the average operating temperature. The following is a measurement of the actual surface shape (1b) and / or the actual optical effect of the optical element (1).

5. The method as described in any one of claims 1 to 4, Its features are: The optical element (1) is manufactured at temperature T. F The next step is to process it.

6. The method as described in any one of claims 1 to 5, Its features are: The optical element (1) operates at an average temperature The next step is to process it.

7. The method as described in any one of claims 1 to 6, Its features are: The method includes determining the optical element (1) at the average operating temperature. The actual surface shape (1b) and / or the actual optical effect and the optical element (1) at the average operating temperature The surface shape of the target (1a) and / or the optical effect of the target.

8. The method as described in any one of claims 1 to 7, Its features are: The method further includes the following steps: - By means of a correction element and / or at least one additional manipulator, particularly a rigid manipulator, the difference between the actual surface shape (1b) and the target surface shape (1a) and / or the difference between the actual optical effect and the target optical effect is partially compensated; and - The purpose of processing the optical element is to adapt the actual surface shape (1b) and / or the actual optical effect of the optical element (1) to the average operating temperature. The target surface shape (1a) and / or the target optical effect are considered, while the difference between the actual surface shape (1b) and the target surface shape (1a) and / or the difference between the actual optical effect and the target optical effect are partially compensated by means of the correction member and / or the at least one other manipulator.

9. A method for manufacturing an optical element (9) for an optical system, the optical element having a target surface shape (1a) and / or a target optical effect during operation of the optical system. Its features are: The optical element (1) has an average operating temperature controlled by at least one thermal manipulator during operation of the optical system. (2) The method includes the following steps: - Determine the manufacturing temperature of the optical element (1). The actual surface shape (1b) and / or the actual optical effect; -Due to the manufacturing temperature T F With this average operating temperature temperature difference between Therefore, the actual surface shape (1b) of the optical element (1) and / or the change in the actual optical effect are determined; as well as The purpose of processing the optical element (1) is to adapt the actual surface shape (1b) and / or the actual optical effect of the optical element (1) to the average operating temperature. The surface shape (1a) of the target and / or the optical effect of the target, depending on the manufacturing temperature, are determined by the following: The determined actual surface shape (1b) and / or actual optical effect depend on the average operating temperature. With this manufacturing temperature temperature difference between The determined changes in the actual surface shape (1b) and / or the actual optical effect.

10. The method of claim 9, Its features are: The actual surface shape (1b) of the optical element (1) and / or the actual optical effect are affected by the manufacturing temperature. With this average operating temperature The temperature difference between The determination of the change includes the manufacturing temperature. The actual surface shape (1b) and / or the actual optical effect of the optical element (1) at the average operating temperature Determination of the difference between the target surface shape (1a) and / or the target optical effect of the optical element (1).

11. The method as described in claim 9 or 10, Its features are: Based on the mathematical model used to determine the local deformation under temperature changes, the actual surface shape (1b) of the optical element (1) and / or the change in the actual optical effect are determined.

12. The method as described in any one of claims 9 to 11, Its features are: The method further includes the following steps: - By means of a correction member and / or at least one other manipulator, particularly a rigid manipulator, the determined variation of the actual surface shape (1b) and / or the actual optical effect of the optical element (1) is partially compensated. as well as The purpose of processing the optical element (1) is to adapt the actual surface shape (1b) and / or the actual optical effect of the optical element (1) to the average operating temperature. The target surface shape (1a) and / or the target optical effect are considered, while taking into account the determined changes in the actual surface shape (1b) and / or the actual optical effect of the optical element (1) by means of the correction member and / or the at least one other manipulator.

13. The method as described in any one of claims 9 to 12, Its features are: The optical element (1) is manufactured at this temperature The next step is to process it.

14. The method as described in any of the preceding claims, Its features are: The method further includes the following steps: - Determine the optical effects of the optical system, especially the wavefront; and - Determine the optical element (1) at the average operating temperature The target surface shape (1a) and / or the target optical effect are determined by the optical system.

15. An optical element (1) for an optical system, the optical element having a target surface shape (1a) and / or a target optical effect during operation of the optical system, particularly manufactured by the method according to any one of claims 1 to 14. Its features are: The optical element (1) measures temperature. Especially in manufacturing temperatures Below, having a first surface shape; and at an average operating temperature Below, the optical element (1) has the target surface shape (1a) and / or target optical effect, wherein the optical element (1) has an average operating temperature controlled by at least one thermal manipulator (2) during operation of the optical system. .

16. An optical system for semiconductor technology equipment, comprising: - At least one optical element (1) as described in claim 15; as well as - At least one thermal manipulator (2) that controls the average operating temperature of the optical element (1). .

17. The optical system as claimed in claim 16, Its features are: Compared to a state in which the optical element (1) and the at least one other optical element are substantially at least at the same temperature, a predetermined state is defined in which the average operating temperature of the optical element (1) is... and the average operating temperature of at least one other optical element A deviation of at least 1K from each other results in a reduction of at least one aberration by at least 20%, preferably at least 25%, and especially at least 30%.

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