Device, method and system for calibrating the temperature measurement on an optical element for semiconductor lithography

Abstract

A device (1), a method, and a system for calibrating the temperature measurement of an optical element (6) for semiconductor lithography are presented and described. To improve the accuracy of the temperature measurement of an optical element (6), it is proposed to provide at least one secondary temperature sensing device (3) for spatially resolved detection of the thermal radiation (WR1) of the first reference element (4), and / or a second reference element (5), wherein the second reference element (5) is arranged such that thermal radiation (WR2) emanating from the second reference element (5) can be detected by the primary temperature sensing device (2).

Description

[0001] The invention relates to a device for calibrating the temperature measurement on an optical element for semiconductor lithography comprising: at least one primary temperature sensing device for spatially resolved detection of the thermal radiation of an optical element, a first reference element, wherein the first reference element is arranged such that thermal radiation emanating from the first reference element and reflected from the surface of the optical element can be detected by the primary temperature sensing device.

[0002] The invention further relates to a method for calibrating the temperature measurement of an optical element for semiconductor lithography, comprising the following steps: a) providing an optical element, b) providing a device for calibrating the temperature measurement of an optical element for semiconductor lithography, in particular according to one of claims 1 to 5, wherein the device for calibrating the temperature measurement of an optical element for semiconductor lithography comprises at least one primary temperature sensing device for spatially resolved detection of the thermal radiation of the optical element and a first reference element, wherein the first reference element is arranged such that thermal radiation emanating from the first reference element and reflected from the surface of the optical element can be detected by the primary temperature sensing device.wherein the device for calibrating the temperature measurement on an optical element for semiconductor lithography comprises at least one secondary temperature sensing device for spatially resolved detection of the thermal radiation of the first reference element and / or a second reference element, wherein the second reference element is arranged such that thermal radiation emanating from the second reference element can be detected by the primary temperature sensing device, c) spatially resolved detection of the thermal radiation emanating from the optical element by means of the primary temperature sensing device, wherein the method comprises at least one of the following steps d), e) and / or f): d) spatially resolved detection of the thermal radiation emanating from the first reference element by means of the secondary temperature sensing device, e) detection, preferably spatially resolved detection,the thermal radiation emanating from the second reference element by means of the primary temperature sensing device, wherein in step e) the temperature of the second reference element is kept substantially constant, f) detection, preferably spatially resolved detection, of the thermal radiation emanating from the second reference element by means of the primary temperature sensing device, wherein in step f) the temperature of the second reference element is varied.

[0003] The invention also relates to a system for calibrating the temperature measurement on an optical element for semiconductor lithography comprising: a device for calibrating the temperature measurement on an optical element for semiconductor lithography according to any one of claims 1 to 5, and an optical element.

[0004] Projection exposure systems for semiconductor lithography are used to create extremely fine structures, particularly on semiconductor devices or other microstructured components. The operating principle of these systems is based on the creation of extremely fine structures down to the nanometer range by means of a generally reduced-size image of structures on a mask, a so-called reticulum, onto a wafer, which is coated with photosensitive material. The minimum dimensions of the generated structures depend directly on the wavelength of the light used. Recently, light sources with emission wavelengths in the nanometer range, for example between 1 nm and 120 nm, particularly in the 13.5 nm range, have been increasingly used. The wavelength range around 13.5 nm is also known as the EUV range. The microstructured components are used, among other things, for... EUV systems can also be used with the established DUV systems with wavelengths between 100 nm and 400 nm, especially 193 nm. With the introduction of the EUV range and the resulting ability to produce even smaller structures, the requirements for optical correction of DUV systems with a wavelength of 193 nm have increased further.

[0005] In addition, with each new generation of projection imaging systems, regardless of wavelength, throughput increases to improve efficiency. This typically leads to greater thermal stress and thus to increased thermally induced aberrations. To correct these aberrations, optical assemblies, such as manipulators, can be used. These assemblies change the position and orientation of the optical elements or influence the imaging properties of the optical elements, especially mirrors, by deforming their optical surfaces. An optical surface is defined as the portion of an optical element's surface that receives the useful light for imaging structures. Alternatively, the optical elements of the assemblies, which are designed as mirrors, can be cooled by direct water cooling.The mirrors incorporate recesses designed as cooling channels, arranged in one or more planes at varying distances from the optical surface, through which temperature-controlled water flows. Accurate measurement of the surface temperature is advantageous for both approaches.

[0006] To improve the accuracy of optical elements during production and thus minimize aberrations even before use, pre-aging of the optical elements can be performed. For pre-aging, the optical element can preferably undergo heat treatment, such as annealing. This involves heating the optical element to temperatures above its normal operating temperature for an extended period, thereby anticipating changes to the surface shape of the optical element that would occur during operation at the customer's site. Precise measurement of the surface temperature of the optical element is also advantageous to ensure uniform heat treatment across essentially the entire surface, particularly the optically active area.

[0007] Devices and methods for detecting the temperature on the surface of an optical element can be found, for example, in DE 10 2020 203 753 A1 or DE 10 2020 203 750 A1.

[0008] A disadvantage of the known devices, methods, and systems, however, is that the accuracy of the temperature measurement on the surface of the optical element varies considerably between different temperature measurements, especially when the temperature is measured successively on different optical elements. For example, differences in surface properties or differences in the geometry of different optical elements being measured can lead to a loss of temperature measurement accuracy between measurements. Similarly, the surface temperature of the optical element may be inhomogeneous and / or unknown at the beginning of the temperature measurement, which can also lead to inaccuracies or errors in the temperature measurement.

[0009] The invention is therefore based on the objective of providing a device, a method and a system for calibrating the temperature measurement on an optical element for semiconductor lithography, which improves the accuracy of the temperature measurement on an optical element.

[0010] This problem is solved in a device according to the preamble of claim 1 in that the device for calibrating the temperature measurement on an optical element for semiconductor lithography comprises at least one secondary temperature sensing device for spatially resolved detection of the thermal radiation of the first reference element and / or a second reference element, wherein the second reference element is arranged such that thermal radiation emanating from the second reference element can be detected by the primary temperature sensing device.

[0011] The device for calibrating the temperature measurement on an optical element for semiconductor lithography is intended, in particular, to calibrate the surface temperature measurement on an optical element. For this purpose, the devices and components involved in the temperature measurement are calibrated, preferably at least one temperature sensing device, and in particular the primary temperature sensing device. The optical element on which the temperature measurement is performed preferably has reflective properties, at least on the surface to be measured, in particular the optical surface. The optical element can, in particular, be a mirror or an optical lens.

[0012] The device for calibrating the temperature measurement of an optical element comprises at least one primary temperature sensing device for spatially resolving the thermal radiation of the optical element. The temperature, in particular the surface temperature, of the optical element can then be determined from the thermal radiation detected by the primary temperature sensing device. The primary temperature sensing device is preferably configured to detect the thermal radiation of the surface of the optical element to be measured, in particular the optical surface of the optical element. By spatially resolving the thermal radiation with the primary temperature sensing device, the thermal radiation can be individually detected for each point on the surface of the optical element to be measured, in particular the optical surface.This makes it possible to determine the precise temperature distribution on the surface of the optical element to be measured and thus to identify any temperature inhomogeneity on the surface of the optical element. The detection field of the primary temperature detection device is aligned with the surface of the optical element to be measured, in particular the optical effective surface. The primary temperature detection device is preferably designed such that it can detect essentially the entire surface of the optical element facing the primary temperature detection device, in particular essentially the entire optical effective surface of the optical element.Advantageously, the device for calibrating the temperature measurement on an optical element for semiconductor lithography can comprise at least two primary temperature sensing devices, preferably a plurality of primary temperature sensing devices.

[0013] In this context, outgoing thermal radiation is understood to mean, in particular, the thermal radiation that is emitted and / or reflected by the corresponding component.

[0014] The thermal radiation emanating from the optical element and detected by the primary temperature sensing device includes not only thermal radiation emitted by the optical element itself, but also, in particular, thermal radiation merely reflected by the optical element. To ensure that the thermal radiation not directly emitted by the surface of the optical element to be measured, especially its optical surface, and detected by the primary temperature sensing device, originates from, and is specifically emitted by, an element whose temperature, and thus its thermal radiation, is known and / or controllable, a first reference element is provided. This first reference element thus simplifies the determination of the thermal radiation not emitted by the optical element itself, particularly its optical surface.The thermal radiation emanating from, and in particular emitted by, the first reference element can then be easily subtracted from the thermal radiation detected by the primary temperature sensing device. To enable the primary temperature sensing device to detect the known and / or controllable thermal radiation of the first reference element, the first reference element is arranged such that the thermal radiation emitted by the first reference element and reflected from the surface of the optical element can be detected by the at least one primary temperature sensing device. The first reference element preferably has substantially homogeneous surface properties.The first reference element can also be designed such that radiation, in particular thermal radiation, is reflected diffusely, and in particular substantially completely diffusely, and the surface of the first reference element has a low reflectance, preferably a reflectance of less than 20%, and in particular less than 5%. This is intended to prevent radiation, preferably thermal radiation, from being reflected by the first reference element and heating the optical element and / or from being reflected by the optical element and detected by the primary temperature sensing device. This also improves the temperature measurement accuracy.

[0015] To determine the thermal radiation emitted by the first reference element with particular accuracy, and thus improve the accuracy of the temperature measurement of the optical element, the device for calibrating the temperature measurement on an optical element for semiconductor lithography comprises at least one secondary temperature sensing device for spatially resolved detection of the thermal radiation from the first reference element. The thermal radiation emitted by the first reference element, and optionally reflected by the optical element, can thus be detected directly at the first reference element. This, in turn, allows for a very precise determination of the proportion of thermal radiation emitted by the optical element that originates from the first reference element.This portion of the thermal radiation is also detected by the primary temperature sensing device and can then be easily subtracted from the total thermal radiation detected by the primary device. The spatially resolved detection of the thermal radiation from the first reference element by the secondary temperature sensing device also contributes to the accuracy of the temperature measurement.In this way, preferably taking into account the surface properties of the optical element and / or the first reference element and / or taking into account the arrangement of the optical element, the first reference element, the primary temperature sensing device and / or the secondary temperature sensing device, the outgoing thermal radiation at individual points of the first reference element can be assigned to the outgoing thermal radiation at individual points of the optical element and thus, for each point of the optical element, the proportion of thermal radiation emanating from the first reference element and optionally reflected by the optical element into the primary temperature sensing device can be determined very accurately.Changes in the local emission of thermal radiation of the first reference element, for example due to local heating, can thus be compensated, especially in real time, during a temperature measurement of the surface of the optical element by the primary temperature sensing device.

[0016] The detection field of the secondary temperature sensing device is specifically aligned with the surface of the first reference element to be measured. The secondary temperature sensing device is preferably designed such that it can detect substantially the entire surface of the first reference element facing the secondary temperature sensing device. Advantageously, the device for calibrating the temperature measurement on an optical element for semiconductor lithography can comprise at least two secondary temperature sensing devices, preferably a plurality of secondary temperature sensing devices.

[0017] Alternatively or additionally to the secondary temperature sensing device, the device for calibrating the temperature measurement on an optical element for semiconductor lithography can include a second reference element, wherein the second reference element is arranged such that thermal radiation emanating from the second reference element can be detected by the primary temperature sensing device. By using a suitable second reference element, the thermal radiation of a surface with a known and / or controllable temperature and / or thermal radiation can be directly detected by the primary temperature sensing device. This, in turn, allows deviations, in particular errors, in the characteristic curve of the primary temperature sensing device, such as an offset, a slope error, a linearity error, and / or a hysteresis error, to be determined.Alternatively or additionally, drifts in deviations, in particular drifts in offset, slope error, linearity error, and / or hysteresis error, can be determined. This allows for precise calibration of the temperature measurement, especially the temperature measurement by the primary temperature sensing device, at the optical element, thus improving the accuracy of the temperature measurement.

[0018] The calibration of the temperature measurement using the present device for calibrating the temperature measurement of an optical element for semiconductor lithography can be performed before, during, and / or after a temperature measurement of the optical element. Alternatively or additionally, the calibration can be performed before, during, and / or after exposure of the optical element to electromagnetic radiation. Exposure to electromagnetic radiation can occur during the fabrication or processing of the optical element, preferably during annealing of the optical element, and / or during a photolithographic process in which the optical element is used.

[0019] The thermal radiation in question is, in particular, infrared radiation. Consequently, the primary temperature sensing device is designed for the spatially resolved detection of the infrared radiation from the optical element, the primary temperature sensing device is designed for the, preferably spatially resolved, detection of the infrared radiation from the second reference element, and / or the secondary temperature sensing device is designed for the spatially resolved detection of the infrared radiation from the first reference element.

[0020] The device for calibrating the temperature measurement of an optical element for semiconductor lithography can also include a receptacle for receiving the optical element. Alternatively or additionally, the device for calibrating the temperature measurement of an optical element for semiconductor lithography can include at least two first reference elements, preferably a plurality of first reference elements, and / or at least two second reference elements, preferably a plurality of second reference elements.

[0021] The device for calibrating the temperature measurement of an optical element for semiconductor lithography can also include a second reference element. This second reference element is preferably configured like the second reference element already described. In particular, the second reference element is arranged such that thermal radiation emanating from it can be detected by the primary temperature sensing device. The second reference element can be detachably connected to the device for calibrating the temperature measurement of an optical element for semiconductor lithography. Alternatively or additionally, the second reference element can be arranged in the receptacle for holding the optical element. Such a second reference element is particularly suitable, for example, for certain calibrations that are only performed at longer intervals.

[0022] The designation as first or second reference element and as primary or secondary temperature sensing device serves here only to distinguish the respective elements or devices.

[0023] According to one embodiment of the device, the at least one primary temperature sensing device and / or the at least one secondary temperature sensing device are designed as thermal imaging cameras. This allows for very precise detection of thermal radiation and / or determination of the temperature, in particular the surface temperature.

[0024] According to a further embodiment, the device is characterized in that the second reference element has a first reference surface and / or that the second reference element has a second reference surface, and preferably, that the second reference surface is configured such that its emissivity is > 95%. By providing such reference surfaces, particularly accurate temperature measurement can be achieved, as these reference surfaces provide excellent radiation references. Since the second reference surface has an emissivity > 95%, the thermal radiation emitted by the second reference surface depends essentially only on the temperature of the second reference surface and not on other properties of the second reference surface.The second reference surface thus provides an excellent radiation reference for calibrating the temperature measurement, particularly the temperature measurement by the primary temperature sensing device, on an optical element. The emissivity of > 95% of the second reference surface is particularly high within the detection wavelength range of the primary temperature sensing device. The second reference surface can also be configured as a so-called blackbody radiator. Furthermore, the first reference surface of the second reference element can be configured such that at least the emissivity, reflectivity, and / or transmittance of the first reference surface of the second reference element and the surface of the optical element, in particular the optical surface of the optical element, are essentially identical.This also provides a very good radiation reference for calibrating the temperature measurement, in particular the temperature measurement by the primary temperature sensing device, on an optical element. This allows, in particular, the influence of the optical element's surface properties on the temperature measurement to be taken into account. Preferably, it can also be provided that the first reference surface, together with the surface of the optical element, in particular the optical surface of the optical element, has been processed before the temperature measurement and / or the calibration of the temperature measurement. This ensures that the first reference surface and the surface of the optical element, in particular the optical surface of the optical element, have the same properties.The first reference surface can in particular be formed by a sample of the optical element, the sample being received by the second reference element.

[0025] According to a further embodiment of the device, the first reference element and / or the second reference element are temperature-controlled, in particular the first reference surface and / or the second reference surface of the second reference element. This temperature control allows a predetermined and known thermal radiation to be emitted by the reference elements, enabling a simple comparison of the thermal radiation detected by the temperature sensing devices with the thermal radiation and / or temperature emitted by the reference elements. This allows for a particularly precise calibration of the temperature measurement, especially the temperature measurement by the primary temperature sensing device, and thus a very accurate temperature measurement at the optical element.The first reference element and / or the second reference element, in particular the first reference surface and / or the second reference surface, can be temperature-controlled to a constant temperature and / or to varying temperatures, i.e., different temperatures.

[0026] Another embodiment of the device provides that the device for calibrating the temperature measurement on an optical element for semiconductor lithography includes a data processing device, in particular a control device. This allows the calibration of the temperature measurement to be carried out essentially automatically.

[0027] The aforementioned problem is also solved by the method according to claim 6.

[0028] The preceding descriptions of the device can be applied to the method. Likewise, the following descriptions of the method can be applied to the device.

[0029] The procedure includes step a) providing an optical element. The optical element is, in particular, a mirror or an optical lens. The optical element is the optical element on which the temperature measurement to be calibrated is to be performed.

[0030] The method further comprises step b) providing a device for calibrating the temperature measurement on an optical element for semiconductor lithography, in particular according to one of claims 1 to 5, wherein the device for calibrating the temperature measurement on an optical element for semiconductor lithography comprises at least one primary temperature sensing device for spatially resolved detection of the thermal radiation of the optical element and a first reference element, wherein the first reference element is arranged such that thermal radiation emanating from the first reference element and reflected from the surface of the optical element can be detected by the primary temperature sensing device.The device for calibrating the temperature measurement of an optical element for semiconductor lithography comprises at least one secondary temperature sensing device for spatially resolved detection of the thermal radiation of the first reference element and / or a second reference element, wherein the second reference element is arranged such that thermal radiation emanating from the second reference element can be detected by the primary temperature sensing device. A particularly precise calibration and thus a particularly accurate temperature measurement of the optical element can be achieved by such a device. For the precise design and effects of this device, reference is made to the preceding descriptions of the device for calibrating the temperature measurement of an optical element for semiconductor lithography.

[0031] The device for calibrating the temperature measurement of an optical element for semiconductor lithography can also include a second reference element. This second reference element is arranged such that thermal radiation emanating from it can be detected by the primary temperature sensing device. The second reference element can be detachably connected to the device for calibrating the temperature measurement of an optical element for semiconductor lithography. Such a second reference element is particularly useful, for example, for certain calibrations that are only performed at longer intervals.

[0032] The method further comprises step c) spatially resolved detection of the thermal radiation emitted by the optical element using the primary temperature detection device. This allows the primary temperature detection device to detect the thermal radiation primarily used to determine the temperature, in particular the surface temperature, of the optical element. However, the thermal radiation detected by the primary temperature detection device does not exclusively include thermal radiation emitted by the optical element itself, but also, among other things, thermal radiation merely reflected by the optical element. Therefore, at least one further step is performed to achieve the most accurate temperature measurement possible, which is attained through calibration of the temperature measurement, in particular the temperature measurement by the primary temperature detection device.

[0033] The procedure in this case still includes at least one of steps d), e) and / or f). Any combination of steps d), e) and / or f) is possible.

[0034] Step d) comprises spatially resolved acquisition of the thermal radiation emanating from the first reference element using the secondary temperature sensing device. Based on the thermal radiation acquired in step d), the proportion of thermal radiation emanating from the first reference element to the thermal radiation emanating from the optical element can be determined. Thus, the thermal radiation emanating from the first reference element, particularly its emission, can be subtracted from the thermal radiation acquired by the primary temperature sensing device in step c), thereby improving the accuracy of the temperature measurement. Furthermore, changes in the local emission of the thermal radiation from the first reference element, for example, due to local heating, can be compensated for by the spatially resolved acquisition, particularly in real time, during a temperature measurement of the surface of the optical element by the primary temperature sensing device.

[0035] Step e) comprises detecting, preferably with spatial resolution, the thermal radiation emitted by the second reference element using the primary temperature sensing device, wherein in step e) the temperature of the second reference element is kept essentially constant. By keeping the temperature constant, the second reference element emits constant and known thermal radiation. This allows an offset, in particular a zero-point deviation, of the characteristic curve of the primary temperature sensing device to be determined. The thermal radiation of the second reference element, which can be determined from the predetermined temperature of the second reference element and is therefore known, can then be compared to the thermal radiation detected by the primary temperature sensing device, and thus, if necessary, a deviation of the characteristic curve of the primary temperature sensing device can be determined.This, in turn, enables a precise determination of the temperature distribution on the surface of the optical element to be measured, particularly on the optical surface of the optical element. The characteristic curve of the primary temperature sensing device indicates the relationship between the input and output variables of the primary temperature sensing device and is also referred to as the actual characteristic curve or real characteristic curve. Since, in this case, spatially resolved detection of thermal radiation is preferably performed, the primary temperature sensing device preferably has several characteristic curves and / or a separate characteristic curve for each location detected by the primary temperature sensing device. The deviation of the characteristic curve(s) is relative to a target characteristic curve, also called an ideal characteristic curve.

[0036] Furthermore, in step e) it may be provided that the thermal radiation emanating from the second reference element is detected with spatial resolution using the primary temperature detection device.

[0037] Step f) comprises detecting, preferably with spatial resolution, the thermal radiation emitted by the second reference element using the primary temperature sensing device, wherein the temperature of the second reference element is varied in step f). This variation causes the second reference element to emit different, but known, thermal radiation. This allows, in particular, the determination of the sensitivity of the characteristic curve of the primary temperature sensing device. The sensitivity of the characteristic curve is also referred to as the characteristic curve's sensitivity or slope. The sensitivity is the quotient of the change in the output variable to the change in the input variable that causes it. Possible slope errors, i.e., deviations of the slope or sensitivity of the primary temperature sensing device's characteristic curve from the target characteristic curve, can thus be determined.Alternatively or additionally, linearity errors and / or hysteresis errors of the characteristic curve of the primary temperature sensing device can also be determined using the information obtained in step f).

[0038] Furthermore, in step f) it may be provided that the thermal radiation emanating from the second reference element is detected with spatial resolution using the primary temperature detection device.

[0039] If steps c), d), e) and / or f) are performed before the optical element is exposed to electromagnetic radiation, particularly before annealing, the thermal radiation detected and, in particular, the information obtained from it can be used for pre-calibration. If steps c), d), e) and / or f) are performed during the optical element's exposure to electromagnetic radiation, particularly during annealing, the thermal radiation detected and, in particular, the information obtained from it can be used for real-time correction of the temperature measurement calibration and, furthermore, for process control.

[0040] The calibration of the temperature measurement using the present method can be performed before, during, and / or after a temperature measurement of the optical element. Alternatively or additionally, the calibration can be performed before, during, and / or after exposure of the optical element to electromagnetic radiation. This exposure to electromagnetic radiation can occur during the manufacture or processing of the optical element, preferably during annealing, and / or during a photolithographic process in which the optical element is used.

[0041] The temperature of the second reference element in step e) and / or step f) can be at least room temperature, for example at least 20 °C, and / or up to 80 °C, preferably up to 130 °C. This temperature can correspond approximately to the target temperature of the optical element during heat treatment, in particular annealing. Alternatively or additionally, the temperature of the second reference element in step e) and / or step f) can be at least 200 °C.

[0042] Step e) can be performed before step f), or step f) can be performed before step e). Steps d), e), and / or f) can also be performed before step a). Furthermore, step c) can be performed at least temporarily, and in particular substantially completely, simultaneously with step d) and / or step e), or step c) can be performed at least temporarily, and in particular substantially completely, simultaneously with step d) and / or step f). Step a) and / or step b) are preferably performed before step c), step d), step e), and / or step f).

[0043] According to one embodiment, the method comprises the following step: g) Determining the proportion of the thermal radiation emanating from the first reference element to the thermal radiation emanating from the optical element using the thermal radiation detected in step c) by the primary temperature sensing device and the thermal radiation detected in step d) by the secondary temperature sensing device. This allows for a particularly accurate temperature measurement, since the proportion of thermal radiation emanating from the first reference element can thus be easily subtracted from the thermal radiation emanating from the optical element and detected by the primary temperature sensing device.

[0044] Another embodiment of the method comprises the following step: h) Determining an offset, in particular the zero-point deviation, of the characteristic curve of the primary temperature sensing device using the thermal radiation detected by the primary temperature sensing device in step e) and the temperature of the second reference element in step e) and / or using the thermal radiation detected by the primary temperature sensing device in step f) and the temperature of the second reference element as varied in step f). The offset determined in this step then allows for precise calibration of the temperature measurement, in particular the temperature measurement by the primary temperature sensing device.In this context, it is particularly advantageous to use the thermal radiation of the second reference element, detected by the primary temperature sensing device in step e), and the temperature of the second reference element in step e) to determine the offset. Because the temperature of the second reference element is kept constant in step e), it emits constant and known thermal radiation. This known thermal radiation forms a very precise radiation reference for the primary temperature sensing device. The method can also include the following step: h1) Calibrating the primary temperature sensing device using the offset of the primary temperature sensing device's characteristic curve determined in step h).Since the offset of the characteristic curve or curves of the primary temperature sensing device can drift, it is also advantageous to perform step h) and / or h1) before, during and / or after a temperature measurement, in particular by the primary temperature sensing device, on the optical element.

[0045] Another embodiment of the method comprises the following step: i) Determining the sensitivity of the characteristic curve of the primary temperature sensing device using the thermal radiation detected by the primary temperature sensing device in step e) and / or the temperature of the second reference element in step e) and / or using the thermal radiation detected by the primary temperature sensing device in step f) and / or the temperature of the second reference element varied in step f). The sensitivity determined in this step can then be used to precisely calibrate the temperature measurement. In this context, it is particularly advantageous to use the thermal radiation of the second reference element detected by the primary temperature sensing device in step f) and the temperature of the second reference element in step f) to determine the offset.Due to the temperature of the second reference element, which is varied in step f), thermal radiation of varying, but simultaneously known, intensity is emitted from the second reference element. This known thermal radiation forms a very precise radiation reference for the primary temperature sensing device. The method can also include the following step: i1) calibrating the primary temperature sensing device using the sensitivity of its characteristic curve determined in step i). Since the sensitivity of the characteristic curve(s) of the primary temperature sensing device can drift, it is also advantageous to perform step i) and / or i1) before, during, and / or after a temperature measurement, particularly by the primary temperature sensing device, on the optical element.The temperature of the second reference element in step e) and / or step f) can be at least room temperature, for example at least 20 °C, and / or up to 80 °C, preferably up to 130 °C. This temperature can correspond approximately to the target temperature of the optical element during heat treatment, in particular annealing. Alternatively or additionally, the temperature of the second reference element in step e) and / or step f) can be at least 200 °C.

[0046] According to a further embodiment of the method, the method comprises the following step: j) Exposing the optical element to electromagnetic radiation, in particular by means of at least one heating element. This calibrates the temperature measurement at the optical element at its processing temperature. Preferably, the temperature measurement at the optical element is calibrated during processing of the optical element, more preferably during annealing of the optical element, in particular of the optical surface of the optical element. Alternatively or additionally, the temperature measurement at the optical element can be calibrated during the execution of a photolithographic process using the optical element. The electromagnetic radiation can be thermal radiation and / or light.It may be provided that step j) occurs after step c), step d), step e), step f), step g), step h), step h1), step i) and / or step i1), that step j) occurs before step c), step d), step e), step f), step g), step h), step h1), step i) and / or step i1), and / or that step j) occurs at least temporarily, in particular substantially completely, simultaneously with step c), step d), step e), step f), step g), step h), step h1), step i) and / or step i1).

[0047] The aforementioned problem is also solved by the system according to claim 11.

[0048] The preceding descriptions of the device and / or the method can be applied to the system. Likewise, the following descriptions of the system can be applied to the device and / or the method.

[0049] The system comprises a device for calibrating the temperature measurement on an optical element for semiconductor lithography according to one of claims 1 to 5. Regarding the precise design and effects of this device, reference is made to the preceding descriptions of the device for calibrating the temperature measurement on an optical element for semiconductor lithography.

[0050] The system also includes an optical element. This optical element is, in particular, a mirror or an optical lens. The optical element is the optical element on which the temperature measurement to be calibrated is to be performed.

[0051] According to one embodiment of the system, the first reference surface of the second reference element is designed such that at least the emissivity, reflectivity, and / or transmittance of the first reference surface of the second reference element and the surface of the optical element are essentially identical. This provides a very good radiation reference for calibrating the temperature measurement, particularly the temperature measurement by the primary temperature sensing device, on an optical element. This allows, in particular, the influence of the surface properties of the optical element on the temperature measurement to be taken into account. Preferably, it can also be provided that the first reference surface, together with the surface of the optical element, especially the optical surface of the optical element, has been processed before the temperature measurement and / or the calibration of the temperature measurement.This ensures that the first reference surface and the surface of the optical element, in particular the optical effective surface of the optical element, have the same properties. The processing of the first reference surface need not include all the processing steps of the surface of the optical element, but can include only one or a subset of these steps. The first reference surface can, in particular, be formed by a sample of the optical element, which is then held by the second reference element.

[0052] The invention is explained in more detail below with reference to a drawing that illustrates only a preferred embodiment. The drawing shows: Fig. 1. A device for calibrating the temperature measurement on an optical element for semiconductor lithography in a front view, and Fig. 2 the device for calibrating the temperature measurement on an optical element for semiconductor lithography made of Fig. 1 in another front view.

[0053] In Fig. Figure 1 shows a device for calibrating the temperature measurement of an optical element for semiconductor lithography 1 in a front view. The device 1 comprises a primary temperature sensing device 2 and a secondary temperature sensing device 3. The secondary temperature sensing device 3 is aligned with a first reference element 4. The primary temperature sensing device 2 is in turn aligned with a second reference element 5 and an optical element 6, in particular the optical surface 7 of the optical element 6. The primary temperature sensing device 2 can detect the thermal radiation W emanating from the optical element 6. E spatially resolved measurement and the thermal radiation W emanating from the second reference element 5, in particular the emitted radiation R2The secondary temperature sensing device 3 can, in turn, detect the thermal radiation W emanating from the first reference element 4, preferably with spatial resolution. R1 capture.

[0054] The surface temperature of the optical element 6, in particular its effective surface, can be measured using the primary temperature sensing device 2. However, to obtain the most accurate measurement possible, it is advisable to calibrate the temperature measurement, especially the primary temperature sensing device 2 used for this purpose. For this, it must first be taken into account that the thermal radiation W emitted by the optical element 6 Edoes not exclusively include thermal radiation emitted by the optical element 6 itself, but also thermal radiation that is merely reflected by the optical element 6. Thus, the proportion of thermal radiation W not emitted by the optical element 6 itself in relation to the thermal radiation emanating from the optical element 6 is... E To enable simple determination, the first reference element 4 and the secondary temperature sensing device 3 are provided. The first reference element 4 is temperature-controlled and has a low reflectance. A significant proportion of the thermal radiation W emitted by the optical element 6 is not emitted by the optical element itself. E is thus determined by the thermal radiation W emanating from the first reference element 4, in particular the emitted radiation. R1 formed. The corresponding thermal radiation W R1The radiation of the first reference element 4 is reflected in this case by the optical element 6, in particular the optical effective surface 7 of the optical element 6, and then, as already mentioned, forms part of the thermal radiation W emanating from the optical element. E This is in Fig. 1 represented by corresponding arrows.

[0055] To measure the thermal radiation W emanating from the first reference element 4, in particular the emitted radiation R1 To enable precise, direct, and spatially resolved detection, the secondary temperature detection device 3 is provided. The thermal radiation W detected by the secondary temperature detection device 3 R1 The first reference element 4 can then be easily determined from the thermal radiation W emanating from the optical element 6. E be factored out.

[0056] The spatially resolved detection of the thermal radiation W emanating from the optical element 6 Eby the primary temperature sensing device 2 and the spatially resolved detection of the thermal radiation W emanating from the first reference element 4, in particular emitted, R1 The secondary temperature sensing device 3 can be used to measure temperature during the exposure of the optical element 6 to electromagnetic radiation ES from a radiation source 8. This exposure to electromagnetic radiation ES can, for example, be thermal radiation from a heating element, thereby annealing the optical element 6.

[0057] In Fig. 2 is the device for calibrating the temperature measurement on an optical element for semiconductor lithography made of Fig. 1 shown in another front view. In connection with Fig. 2. Further steps for calibrating the temperature measurement, in particular the primary temperature sensing device 2 used for temperature measurement, are now explained. These steps are carried out using the primary temperature sensing device 2 and the second reference element 5.

[0058] The second reference element 5 comprises a first reference surface 9 and a second reference surface 10. The first reference surface 9 is configured such that its emissivity, reflectivity, and / or transmittance are substantially the same as those of the optical surface 7 of the optical element 6. The second reference surface 10 is configured such that its emissivity is > 95%. The second reference element 5, and in particular the two reference surfaces 9 and 10, thus forms a very good radiation reference.

[0059] The second reference element 5, in particular the two reference surfaces 9, 10, are also designed to be temperature-controlled. For calibration, the temperature of the second reference element 5 is then either kept constant or varied. A known constant or varying thermal radiation W RZ This heat radiation W originates from the second reference element 5; in particular, it is emitted from the second reference element 5. R2 The temperature of the second reference element 5 is then detected by the primary temperature sensing device 2. If the temperature of the second reference element 5 is kept constant, an offset of the characteristic curve of the primary temperature sensing device 2 can be determined and used for calibration. Conversely, if the temperature of the second reference element 5 is varied, the sensitivity of the characteristic curve of the primary temperature sensing device 2 can be determined and used for calibration.

[0060] The detection, preferably with spatial resolution, of the thermal radiation W emanating from the second reference element 5 R2 The primary temperature sensing device 2 can, during the exposure of the optical element 6 to electromagnetic radiation ES by a radiation source 8, spatially resolve the thermal radiation W emanating from the optical element 6. E by the primary temperature sensing device 2 and / or the spatially resolved detection of the thermal radiation W emanating from the first reference element 4, in particular emitted thermal radiation R1 by the secondary temperature sensing device 3.

[0061] In the Fig. 1 and Fig. For the sake of clarity, 2 are the electromagnetic radiation ES and the thermal radiation W emanating from the first reference element 4, in particular the emitted radiation. R1 , the thermal radiation W emanating from the second reference element 5, in particular emittedR2 and the thermal radiation W emanating from the optical element 6 E Each is shown only schematically and for individual locations. Reference symbol list 1 Device for calibrating the temperature measurement on an optical element for semiconductor lithography 2 primary temperature sensing device 3 secondary temperature sensing devices 4 first reference element 5 second reference element 6 optical element 7 optical effective area 8 Radiation source 9 first reference surface 10 second reference surface ES electromagnetic radiation W E Thermal radiation emanating from the optical element W R1 Thermal radiation emanating from the first reference element W R2 Thermal radiation emanating from the second reference element QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 203 753 A1

[0007] DE 10 2020 203 750 A1

[0007]

Claims

[1] Device for calibrating the temperature measurement on an optical element for semiconductor lithography (1) comprising: - at least one primary temperature detection device (2) for spatially resolved detection of the thermal radiation (W E ) of an optical element (6), - a first reference element (4), - wherein the first reference element (4) is arranged such that thermal radiation emanating from the first reference element (4) and reflected from the surface of the optical element (6) can be detected by the primary temperature detection device (2), characterized by - at least one secondary temperature detection device (3) for the spatially resolved detection of the thermal radiation (W R1 ) of the first reference element (4), and / or - a second reference element (5), wherein the second reference element (5) is arranged such that heat radiation (W R2) can be detected by the primary temperature detection device (2). [2] Device (1) according to claim 1, characterized by that the at least one primary temperature detection device (2) and / or the at least one secondary temperature detection device (3) is designed as a thermal imaging camera. [3] Device (1) according to claim 1 or claim 2, characterized by that the second reference element (5) has a first reference surface (9) and / or that the second reference element (5) has a second reference surface (10) and that, preferably, the second reference surface (10) is designed such that the emissivity of the second reference surface (10) is > 95%. [4] Device (1) according to one of claims 1 to 3, characterized bythat the first reference element (4) is temperature-controlled and / or that the second reference element (5) is temperature-controlled, in particular the first reference surface (9) and / or the second reference surface (10) of the second reference element (5) is temperature-controlled. [5] Device (1) according to one of claims 1 to 4, characterized by a data processing device, in particular a control device. [6] Method for calibrating the temperature measurement on an optical element (6) for semiconductor lithography, comprising the following steps: a) providing an optical element(6), b) providing a device for calibrating the temperature measurement on an optical element for semiconductor lithography (1), in particular according to one of claims 1 to 5, - wherein the device for calibrating the temperature measurement on an optical element for semiconductor lithography (1) comprises at least one primary temperature detection device (2) for spatially resolved detection of the thermal radiation (W E ) of the optical element (6) and a first reference element (4), - wherein the first reference element (4) is arranged such that thermal radiation emanating from the first reference element (4) and reflected from the surface of the optical element can be detected by the primary temperature detection device (2), - wherein the device for calibrating the temperature measurement on an optical element for semiconductor lithography (1) comprises at least one secondary temperature detection device (3) for spatially resolved detection of the thermal radiation (W R1) of the first reference element (4) and / or a second reference element (5), wherein the second reference element (5) is arranged such that heat radiation (W R2 ) can be detected by the primary temperature detection device (2), c) spatially resolved detection of the thermal radiation (W E ) by means of the primary temperature detection device (2), - wherein the method comprises at least one of the following steps d), e) and / or f): d) spatially resolved detection of the thermal radiation (W R1 ) by means of the secondary temperature detection device (3), e) detecting, preferably spatially resolved, the thermal radiation (W R2 ) by means of the primary temperature detection device (2), - wherein in step e) the temperature of the second reference element (5) is kept substantially constant, f) detecting, preferably spatially resolved, the thermal radiation (W R2 ) by means of the primary temperature detection device (2), - wherein in step f) the temperature of the second reference element (5) is varied. [7] Method according to claim 6, characterized by that the procedure includes the following step: g) Determining the proportion of thermal radiation (W R1 ) on the thermal radiation (W E ) using the thermal radiation detected in step c) by the primary temperature detection device (2) and the thermal radiation detected in step d) by the secondary temperature detection device (3). [8] Method according to claim 6 or claim 7, characterized bythat the procedure includes the following step: h) determining an offset, in particular the zero point deviation, of the characteristic curve of the primary temperature detection device (2) using the thermal radiation detected by the primary temperature detection device (2) in step e) and the temperature of the second reference element (5) in step e) and / or using the thermal radiation detected by the primary temperature detection device (2) in step f) and the temperature of the second reference element (5) varied in step f). [9] Method according to one of claims 6 to 8, characterized by that the procedure includes the following step: i) Determining the sensitivity of the characteristic curve of the primary temperature detection device (2) using the thermal radiation detected by the primary temperature detection device (2) in step e) and / or the temperature of the second reference element (5) in step e) and / or using the thermal radiation detected by the primary temperature detection device (2) in step f) and / or the temperature of the second reference element (5) varied in step f). [10] Method according to one of claims 6 to 9, characterized by that the procedure includes the following step: j) exposing the optical element (6) to electromagnetic radiation (ES), in particular by means of at least one heating element. [11] System for calibrating the temperature measurement on an optical element (6) for semiconductor lithography, comprising: - a device for calibrating the temperature measurement on an optical element for semiconductor lithography (1) according to one of claims 1 to 5, and - an optical element (6). [12] System according to claim 11, characterized by that the first reference surface (9) of the second reference element (5) is designed such that at least the emissivity and / or the reflectivity and / or the transmittance of the first reference surface (9) of the second reference element (5) and the surface of the optical element (6) substantially correspond.

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