Contactless temperature sensor for a mirror, projection objective, and method for measuring the temperature of a mirror

Abstract

The invention relates to a mirror device (100) for a microlithography projection exposure system (600, 700), comprising at least one mirror (101). The mirror (101) has a mirror body (102) and a reflective surface (103) formed on the mirror body (102). At least one depression (104) is provided which extends from the rear face of the mirror body (102), said rear face facing away from the reflective surface (103), in the direction of the reflective surface (103) through the mirror body (102), wherein the depression (104) has a measuring surface (105), which is thermally connected to the reflective surface (103), on the end facing the reflective surface (103). The mirror device also comprises a sensor unit (106). The sensor unit (106) is produced in the form of an infrared temperature sensor and is designed to determine the temperature of the measuring surface (105) in a contactless manner relative to the measuring surface (105).

Description

[0001] Non-contact temperature sensor for a mirror, projection lens and method for measuring the temperature of a mirror

[0002] This application claims priority from German patent application 102023205 090.0 filed on May 31, 2023. The entire disclosure of this patent application is incorporated into this application by reference.

[0003] The invention relates to a mirror device for a microlithographic projection exposure system, comprising at least one mirror, wherein the mirror has a mirror body and a reflective surface formed on the mirror body, wherein at least one recess is present which extends from a rear side of the mirror body facing away from the reflective surface through the mirror body in the direction of the reflective surface, wherein the recess has a measuring surface thermally connected to the reflective surface at the end facing the reflective surface, and comprising a sensor unit. The invention further relates to a projection lens and a method for measuring the temperature of a mirror.

[0004] Projection exposure systems are used to create extremely fine structures, particularly on semiconductor devices or other microstructured components. The operating principle of these systems is based on creating extremely fine structures down to the nanometer range by means of a generally reduced-size image of structures on a mask, a so-called reticle, on an element to be structured, a so-called wafer, which is provided with photosensitive material. The minimum dimensions of the created structures depend directly on the wavelength of the light used. This light is shaped in an illumination optics for optimal illumination of the reticle. Recently, light sources with an emission wavelength in the range of a few nanometers, for example between 1 nm and 120 nm, particularly in the range of 13.5 nm, have been increasingly used. This wavelength range is also referred to as the EUV range.In addition to systems operating in the EUV range, microstructured components are also manufactured using the market-established DUV systems with a wavelength between 100 nm and 300 nm, particularly 193 nm. With the demand for ever smaller structures, the requirements for optical correction in the systems have continued to increase. With each new generation of projection exposure systems operating in the EUV or DUV range, throughput is increased to increase cost-effectiveness.

[0005] The projection exposure system comprises several mirrors that reflect the radiation. The mirrors have a precisely defined shape and are precisely positioned to ensure that the image of the mask onto the lithographic object is of sufficient quality. During operation, the projection exposure system is exposed to influences that affect the quality of the image. For example, if thermal expansion leads to a change in the geometric shape of a mirror, the wavefront of the radiation reflected by the mirror changes. To ensure optimal use of the mirrors, it is therefore necessary to precisely know the temperature on the active mirror surface, i.e. the area of ​​the reflective surface exposed to electromagnetic radiation. Typically, holes are drilled into the back of the mirror body, into which temperature sensors are then inserted.The temperature sensors are typically based on electrical effects and are glued into the bore. To read the temperature sensors, electrically conductive cables are used wherever possible, but these lead to a mechanical coupling between the mirror body and the environment. This can disrupt mirror performance, which is why very thin and therefore very sensitive cables are used. This, in turn, increases the demands on the manufacturing and operation of the mirror device. The temperature information can, for example, be used to control a heating or cooling device to maintain the temperature of the entire mirror at a constant value, or to appropriately adjust the projection exposure system after a temperature change.Therefore, it is an object of the present invention to enable accurate temperature measurement at the active mirror surface and to reduce the above-mentioned disadvantages.

[0006] The object is achieved with a mirror device according to claim 1. Advantageous embodiments with expedient further developments are specified in the subclaims.

[0007] The mirror device is characterized in that the sensor unit is designed as an infrared temperature sensor and is configured to determine the temperature of the measuring surface without contact with the measuring surface. By measuring the temperature of the measuring surface, which is thermally connected to the reflective surface, by means of non-contact detection of the infrared radiation emitted by the measuring surface, the temperature of the reflective surface can be determined in specific areas. By non-contact detection of the measurement signal, i.e., the infrared radiation emitted by the measuring surface, the temperature of the measuring surface and thus the temperature of the reflective surface or the active mirror surface can be determined, with as little intervention as possible in the mirror device and its configuration.Contactless detection with respect to the measuring surface means that at least the measuring surface and the temperature sensor are mechanically decoupled from one another, and the temperature measurement therefore takes place without contact with the measuring surface. In other words, the temperature sensor is mechanically completely or at least partially decoupled from the mirror, with no direct mechanical connection between the temperature sensor and the measuring surface. The infrared temperature sensor is preferably sensitive to long-wave IR radiation with wavelengths between 7 pm and 14 pm. The measuring surface can correspond to the entire base area of ​​the recess, although it is preferred if the measuring surface only corresponds to a partial area of ​​the base area. In particular, the size of the measuring surface can be between 1 pm. 2 and 1 mm 2 For example, the measuring area can be smaller than 5 mm 2 , preferably less than 2 mm 2, preferably less than 1 mm 2 be.

[0008] Furthermore, it is preferred if the recess extends through the mirror body almost to the reflection surface. Furthermore, the recess can also be stepped, i.e., have different diameters along its length. The closer the measuring surface is to the reflection surface, the more accurately the temperature of the reflection surface can be determined from the temperature measurement of the measuring surface. The recess is preferably formed as a bore.

[0009] The mirror's reflective surface can be designed for high reflectivity of EUV and / or DUV radiation. EUV radiation refers to electromagnetic radiation in the extreme ultraviolet spectral range with wavelengths between 5 nm and 100 nm, particularly wavelengths between 5 nm and 30 nm. DUV radiation lies in the deep ultraviolet spectral range and has a wavelength between 100 nm and 300 nm. The reflective surface can be formed by a highly reflective coating. This can be a multilayer coating, particularly a multilayer coating with alternating layers of molybdenum and silicon. With such a coating, approximately 70% of the incident EUV radiation can be reflected. The remaining approximately 30% is absorbed and leads to heating of the EUV mirrors.

[0010] Furthermore, it is advantageous if the sensor unit is arranged in such a way that the temperature measurement takes place without contact with the mirror body, i.e. there is complete decoupling between the sensor unit and the mirror body. For this purpose, in one embodiment the mirror body can be suspended from a frame, wherein the suspension can be movable so that the position of the mirror body relative to the frame can be adjusted. The sensor unit is preferably arranged or fastened to the frame. Alternatively, it is possible in this context for the mirror body to be mounted on a bearing, wherein the sensor unit is fastened to the bearing. This in turn enables decoupling of the sensor unit from the mirror body and thus enables more precise temperature measurement and interference-reduced and thus improved operation of the mirror device.

[0011] In a further alternative embodiment, the sensor unit can also be attached to the mirror body itself. In particular, it can be provided that the sensor unit is attached to a fastening means that is connected or connectable to the mirror body. This makes it possible to reduce the distance between the sensor unit and also between the mirror body and a frame.

[0012] Furthermore, it is preferred if the sensor unit comprises an optical system, an infrared detector and electronics associated with the infrared detector, wherein the optical system is arranged in the beam path between the measuring surface and the infrared detector. By means of the optical system, the measurement signal, i.e. the infrared radiation emitted by the measuring surface, is imaged from the measuring surface onto the infrared detector. The infrared detector converts the IR measurement signal by means of electronics into an electrical signal, which is transmitted in analog or digital form via an external interface to a control unit for display or further processing. Furthermore, it is advantageous if the optical system comprises at least one lens, in particular a converging lens, wherein the optical system can also comprise several lenses / converging lenses or alternatively also an aperture.The sensor unit preferably has a housing to which the sensor unit is attached to the frame, the bearing, or the mirror body. The infrared sensor unit can be designed as an image sensor, so that the infrared radiation emitted by the mirror body can be detected with spatial resolution. The infrared detector can be designed as a bolometer, thermopiles, or semiconductor sensors (e.g., InSb, HgCdTE).

[0013] In a particularly simple embodiment, the sensor unit can also comprise exclusively an infrared detector and electronics, i.e. can be formed without an additional optical system.

[0014] Particularly preferably, the sensor unit is at least partially accommodated in the recess, with at least 50% of the longitudinal extent of the sensor unit, preferably 75%, and particularly preferably 80% of the longitudinal extent of the sensor unit being accommodated in the recess. The recess is thus designed to be externally accessible from the rear side of the mirror body facing away from the reflection surface, so that the sensor unit can be at least partially inserted into the recess from there. The diameter of the sensor unit is therefore smaller than the diameter of the recess.

[0015] In order to be able to determine the temperature as accurately as possible and to keep the distance between the measuring surface and the optical system as small as possible, it is preferred if the optical system is designed as a light guide that is at least partially accommodated in the recess or extends through the recess in the direction of the measuring surface. The light guide guides the infrared measurement signal from the measuring surface to the infrared detector. In this case, the infrared detector and the electronics associated with the infrared detector can preferably be attached to the frame or to a bearing, while the light guide is connected to the detector at one end and projects into the recess or extends through the recess.This allows decoupling of the sensor unit from the mirror body and at the same time the distance between the measuring surface and the sensor unit is chosen to be so small that infrared background radiation, for example from a frame of the mirror device or from an adjacent housing, is suppressed.

[0016] In an alternative embodiment, it is preferred if the sensor unit is arranged outside the recess, and that a deflecting mirror is additionally arranged outside the recess, such that the measurement signal is deflected from the measuring surface to the optical system and / or the infrared detector. This also enables decoupling of the sensor unit from the mirror body, so that the mechanical properties of the mirror, such as its natural frequency and, for example, the control bandwidth of the position control and / or the maximum travel range, are not influenced or are influenced only to a minor extent. The deflecting mirror and the optical system, i.e. the at least one lens, as well as the infrared detector and the electronics, are preferably attached to the frame or to a bearing.

[0017] In order to increase the measurement signal, it is advantageous if a target is formed on the measuring surface which has a higher emissivity for infrared radiation than an inner wall of the depression or a region of the depression free of a measuring surface. In order to be able to determine the temperature of the reflection surface of the entire active mirror surface region, it is preferred if a plurality of depressions are arranged at a distance from one another and extend from the rear side of the mirror body in the direction of the reflection surface, and if a sensor unit formed as an infrared temperature sensor is assigned to or arranged in each depression. The depressions can be arranged in any desired manner relative to one another. For example, the depressions can be arranged at regular distances from one another. Alternatively, a first region of the reflection surface can have a higher number of depressions than a second region of the same size.

[0018] The invention also relates to a projection exposure objective for a microlithographic projection exposure apparatus, in which a mask is imaged onto a lithography object using a plurality of mirror devices, wherein at least one of the mirror devices is designed as a mirror device according to the invention.

[0019] The advantages and embodiments of the mirror device can be transferred to the projection lens comprising the mirror device.

[0020] The invention can also be used in an illumination device for a microlithographic projection exposure apparatus having a light source, wherein at least one mirror device is designed as a mirror device according to the invention.

[0021] The advantages and embodiments of the mirror device are transferable to the lighting device comprising the mirror device.

[0022] The invention also relates to a method for measuring the temperature of a mirror of a microlithographic projection exposure system, in which the mirror has a mirror body and a reflection surface formed on the mirror body, wherein a recess extending from the rear side of the mirror body in the direction of the reflection surface is formed in the mirror body, at the end of which recess facing the reflection surface a measuring surface is arranged, at which an infrared temperature sensor detects an infrared measurement signal without contact, and a temperature value of the measurement surface is derived from the infrared measurement signal. The temperature value is preferably transmitted to a control unit. The temperature measurement value can be further processed by the control unit, for example by controlling a temperature control element as a function of the measured temperature value in order to keep the temperature of the mirror constant.

[0023] The invention can also be used for optical elements other than mirrors, for example lenses.

[0024] Further features, properties, and advantages of the present invention are described in more detail below using embodiments with reference to the accompanying figures. All features described so far and below are advantageous both individually and in any combination. The embodiments described below are merely examples and do not limit the subject matter of the invention. They show:

[0025] Figure 1a is a schematic representation of a microlithographic projection exposure system designed for operation in the EUV,

[0026] Figure 1 b is a schematic representation of a microlithographic projection exposure system designed for operation in DUV,

[0027] Figure 2 is a schematic representation of a first embodiment of a mirror device,

[0028] Figure 3 is a schematic representation of a second embodiment of a mirror device,

[0029] Figure 4 is a schematic representation of a third embodiment of a mirror device, and

[0030] Figure 5 is a schematic representation of a fourth embodiment of a mirror device.

[0031] Figure 1a shows a schematic representation of an exemplary projection exposure system 600 designed for operation in the EUV, in which the present invention can be implemented.

[0032] According to Fig. 1a, an illumination device in a projection exposure system 600 designed for EUV comprises a field facet mirror 603 and a pupil facet mirror 604. The light from a light source unit, which comprises a plasma light source 601 and a collector mirror 602, is directed onto the field facet mirror 603. A first telescopic mirror 605 and a second telescopic mirror 606 are arranged in the light path downstream of the pupil facet mirror 604. A deflection mirror 607 is arranged downstream in the light path, which deflects the radiation incident upon it onto an object field in the object plane of a projection objective comprising six mirrors 651-656. At the location of the object field, a reflective structure-bearing mask 621 is arranged on a mask table 620, which is imaged by means of the projection lens into an image plane in which a substrate 661 coated with a light-sensitive layer (photoresist) is located on a wafer table 660.

[0033] The invention can also be used in a DUV system, as shown in Figure 1b. A DUV system is essentially constructed like the EUV system described above in Figure 1a, whereby mirrors and lenses can be used as optical elements in a DUV system, and the light source of a DUV system emits useful radiation in a wavelength range from 100 nm to 300 nm.

[0034] The DUV lithography system 700 shown in Figure 1b has a DUV light source 701. An ArF excimer laser, for example, can be provided as the DUV light source 701, which emits radiation 702 in the DUV range at, for example, 193 nm. A beam-shaping and illumination device 703 directs the DUV radiation 702 onto a photomask 704. The photomask 704 is designed as a transmissive optical element and can be arranged outside the beam-shaping and illumination device 703. The photomask 704 has a structure that is imaged in a reduced size onto a wafer 706 or the like by means of the projection system 705. The projection system 705 has a plurality of lenses 707 and / or mirrors 708 for imaging the photomask 704 onto the wafer 706. Individual lenses 707 and / or mirrors 708 of the projection system 705 can be arranged symmetrically to the optical axis 709 of the projection system 705.It should be noted that the number of lenses 707 and mirrors 708 of the DUV lithography system 700 is not limited to the number shown. More or fewer lenses 707 and / or mirrors 708 may also be provided.

[0035] In particular, the beam-shaping and illumination device 703 of the DUV lithography system 700 comprises a plurality of lenses 707 and / or mirrors 708. Furthermore, the mirrors are typically curved at their front side for beam shaping. An air gap 710 between the last lens 707 and the wafer 706 can be replaced by a liquid medium having a refractive index > 1. The liquid medium can be, for example, ultrapure water. Such a setup is also referred to as immersion lithography and exhibits increased photolithographic resolution.

[0036] Figure 2 shows a mirror device 100 for the microlithographic projection exposure apparatus 600, 700, with a mirror 101, wherein the mirror

[0037] 101 has a mirror body 102 and a reflection surface 103 formed on the mirror body 102. Furthermore, there is a recess 104 which extends from a rear side of the mirror body facing away from the reflection surface 103

[0038] 102 extends through the mirror body 102 in the direction of the reflection surface 103, wherein the recess 104 has, at the end facing the reflection surface 103, a measuring surface 105 thermally connected to the reflection surface 103. The recess 104 is formed here as a bore. To determine the temperature of the mirror body 102 or the active surface of the mirror 101, a sensor unit 106 is provided, which is formed as an infrared temperature sensor and is configured to determine the temperature of the measuring surface 105 without contact with the measuring surface 105. The mirror 101 of the mirror device 100 can be formed as a mirror of the projection lens or as a mirror of the illumination device of the microlithographic projection exposure system 600, 700.

[0039] In order to be able to perform the most accurate temperature measurement possible and to minimize the influence of the sensor unit and the measuring process on the mirror 101, the sensor unit 106 is arranged decoupled from the mirror body 102. In the present case, the sensor unit 106 is attached to a frame 107, with the mirror body 102 preferably being movably suspended from the frame 107. Alternatively—and not shown here—in a frameless mirror 101, the mirror body 102 can also be mounted on a bearing, with the sensor unit 106 being arranged on the bearing. The sensor unit 106 comprises an optical system 108, an infrared detector 109, and electronics 110 assigned to the infrared detector, with the optical system 108 being arranged between the measuring surface 105 and the infrared detector 109. The optical system 108 is formed in the present case as at least one lens 111.By means of the optical system 108, the measurement signal emitted by the measuring surface 105, i.e., the infrared radiation, is imaged onto the infrared detector 109. The optical signal is converted into an electronic signal by the electronics 110 of the infrared detector and can be transmitted digitally or analogously to a control unit or display (not shown in detail) via an external interface 116.

[0040] The temperature of the measuring surface 105 thus determined can be further processed by the control unit. For example, a cooling system or temperature control system (not shown in detail) can be present in the mirror body 102, which, if the measured temperature deviates from a predetermined or predeterminable temperature, takes appropriate heating or cooling measures to keep the temperature of the mirror 101 constant. To amplify the measurement signal, a target 114 is formed on the measuring surface 105. This target has a higher emissivity for infrared radiation than the inner wall 115 of the recess 104 or the region of the recess 104 without a measuring surface.

[0041] In order to perform the most accurate temperature measurement possible, the sensor unit 106 is at least partially, in this case largely, accommodated in the recess 104. This enables accurate temperature measurement because the measurement is performed very close to the measuring surface 105, so that background effects, such as the infrared background radiation of the frame 107, are negligible. Furthermore, by decoupling the sensor unit 106 from the mirror body 102, no mechanical transmissions from the sensor unit 106 to the mirror body occur, or these are reduced.

[0042] Figure 3 shows a further example of a sensor unit 106 that is decoupled from the mirror body 102 and measures contactlessly with the mirror body 102 and the measuring surface 105. The optical system 108 of the sensor unit 106 is formed as a light guide 112 that is at least partially accommodated in the recess 104 or extends through the recess 104 toward the measuring surface 105. The light guide 112 is arranged in a protective housing (not shown in detail) and is connected at one end to the infrared detector 109.

[0043] Figure 4 shows a further embodiment of a mirror device 100, which differs in that the sensor unit 106 is arranged outside the recess 104, and that a deflecting mirror 113 is additionally arranged outside the recess 104, such that the measurement signal 117 is deflected from the measurement surface 105 to the optical system 108 and / or the infrared detector 109. In the present case, the sensor unit 106 is also arranged or attached to the frame 107 or to a bearing not shown in detail, so that the sensor unit 106 is mechanically decoupled from the mirror body 102. In an alternative embodiment, however, it is also possible for the sensor unit 106 to be mounted on the mirror body 102.

[0044] Figure 5 shows a further embodiment of a mirror device 100, which differs in that the sensor unit 106 detects the measurement signal without contact with the measurement surface 105, but that the sensor unit 106 is fastened to the mirror body 102. The sensor unit 106 is completely accommodated in the recess 104 and attached to a fastening means 118 on the rear side of the mirror body 102. In order to be able to determine the temperature of a larger area of ​​the active mirror surface, all of the embodiments shown in Figures 2 to 5 can also have a plurality of recesses 104 arranged at a distance from one another and extending from the rear side of the mirror body 102 in the direction of the reflection surface 103. A sensor unit 106 designed as an infrared temperature sensor is assigned to or arranged in each recess 104.

[0045] LIST OF REFERENCE SYMBOLS

[0046] 100 mirror device

[0047] 101 Mirrors

[0048] 102 mirror bodies

[0049] 103 Reflection surface

[0050] 104 Deepening

[0051] 105 measuring area

[0052] 106 Sensor unit (infrared temperature sensor)

[0053] 107 frames

[0054] 108 optical system

[0055] 109 Infrared detector

[0056] 110 Electronics

[0057] 111 lens

[0058] 112 light guides

[0059] 113 Deflecting mirrors

[0060] 114 Target

[0061] 115 inner wall (recess)

[0062] 116 external interface

[0063] 117 measurement signal

[0064] 600 projection exposure system

[0065] 601 plasma light source

[0066] 602 collector mirror

[0067] 603 Field facet mirror (illumination device)

[0068] 604 Pupillary facet mirror (illumination device)

[0069] 605 first telescope mirror (illumination device)

[0070] 606 second telescope mirror (illumination device)

[0071] 607 Deflecting mirror (lighting device)

[0072] 620 Mask table

[0073] 621 Mask

[0074] 651 Mirror (projection lens)

[0075] 652 mirror (projection lens)

[0076] 653 Mirror (projection lens)

[0077] 654 Mirror (projection lens) 655 Mirror (projection lens)

[0078] 656 mirrors (projection lens)

[0079] 660 wafer table

[0080] 661 coated substrate

[0081] 700 DUV lithography system

[0082] 701 DUV light source

[0083] 702 DUV radiation / beam path

[0084] 703 Beam shaping and illumination device (DUV)

[0085] 704 Photomask

[0086] 705 projection system

[0087] 706 wafers

[0088] 707 lens

[0089] 708 mirrors

[0090] 709 optical axis

Claims

CLAIMS 1. Mirror device (100) for a microlithographic projection exposure system (600, 700), with at least one mirror (101), wherein the mirror (101) has a mirror body (102) and a reflection surface (103) formed on the mirror body (102), wherein at least one depression (104) is provided which extends from a rear side of the mirror body (102) facing away from the reflection surface (103) in the direction of the reflection surface (103) through the mirror body (102), wherein the depression (104) has, at the end facing the reflection surface (103), a measuring surface (105) which is thermally connected to the reflection surface (103), and with a sensor unit (106), characterized in that the sensor unit (106) is formed as an infrared temperature sensor and is designed to measure the temperature of the measuring surface (105) in a contactless manner with respect to the measuring surface (105).

2. Mirror device (100) according to claim 1, characterized in that the at least one recess is formed as a bore.

3. Mirror device (100) according to claim 1 or 2, characterized in that the sensor unit (106) is arranged decoupled from the mirror body (102).

4. Mirror device (100) according to one of claims 1 to 3, characterized in that the mirror body (102) is suspended from a frame (107) and that the sensor unit (106) is arranged on the frame (107).

5. Mirror device (100) according to one of claims 1 to 3, characterized in that the mirror body (102) is mounted on a bearing, wherein the sensor unit (106) is arranged on the bearing.

6. Mirror device (100) according to one of claims 1 to 5, characterized in that the sensor unit (106) comprises an optical system (108), an infrared detector (109) and a Electronics (110), wherein the optical system (108) is arranged between the measuring surface (105) and the infrared detector.

7. Mirror device (100) according to claim 6, characterized in that the optical system (108) comprises at least one lens (111).

8. Mirror device (100) according to one of claims 1 to 7, characterized in that the sensor unit (108) is at least partially received in the recess (104).

9. Mirror device (100) according to one of claims 6 to 8, characterized in that the optical system (108) comprises a light guide (112) which is at least partially received in the recess (104) or extends through the recess (104) in the direction of the measuring surface (105).

10. Mirror device (100) according to one of claims 1 to 7, characterized in that the sensor unit (106) is arranged outside the recess (104), and that in addition a deflection mirror (113) is arranged outside the recess (104) such that the measurement signal is deflected from the measurement surface (105) to the optical system (108) and / or the infrared detector (109).

11. Mirror device (100) according to one of claims 1 to 10, characterized in that a target (114) is formed on the measuring surface (105), which target has a higher emissivity for infrared radiation than the inner wall (115) of the recess (104) or the base-free area of ​​the recess (104).

12. Mirror device (100) according to one of claims 1 to 11, characterized in that a plurality of recesses (104) are provided which are formed at a distance from one another and extend from the rear side of the mirror body (102) in the direction of the reflection surface (103), and in that each of the recesses (104) is assigned a sensor unit (106) formed as an infrared temperature sensor.

13. Projection exposure objective for a microlithographic projection exposure apparatus (600,700), in which a mask (621,704) is imaged onto a lithography object using a plurality of mirror devices (100), wherein at least one of the mirror devices is designed as a mirror device (100) according to one of claims 1 to 12.

14. A method for measuring the temperature of a mirror (101) of a microlithographic projection exposure system (600, 700), in which the mirror (101) has a mirror body (102) and a reflection surface (103) formed on the mirror body (102), wherein at least one depression (104) extending from the rear side of the mirror body (102) in the direction of the reflection surface (103) is formed in the mirror body (102), at the end of which depression facing the reflection surface (103) there is arranged a measuring surface (105) which is thermally connected to the reflection surface (103), at which measuring surface an infrared measuring signal is detected contactlessly with respect to the measuring surface 105 by means of a sensor unit (106) designed as an infrared temperature sensor, and a temperature value of the measuring surface is derived from the infrared measuring signal.

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