Measuring device, lithography system, and method for calibrating a measuring device

Abstract

The invention relates to a measuring device (100) for measuring a resistance-dependent measurement variable (T) on or within an optical system (10) of a lithography system (1), said measuring device comprising: a current source (106) for generating a measurement current (I); a measurement line branch (114) and a reference line branch (116); a switching unit (118) for selectively connecting the current source, in a reference switching position (120), to the reference line branch, or, in a measurement switching position (122), to the measurement line branch; a connection unit (126) arranged on the measurement line branch for selectively electrically connecting a measuring resistor (104) or at least one calibration component (128, 130); a reference resistor (132) arranged on the reference line branch; a voltage detection unit (136) for detecting a voltage (UR, UM) selectively across the reference line branch or the measurement line branch; and a control unit (112) for determining a parasitic resistance value (RP) of the measuring device based on a reference voltage (UR) detected in the reference switching position (120) and a measurement voltage (UM) detected in the measurement switching position (122), in which one of the at least one calibration component (128, 130) is connected to the connection unit (126).

Description

[0001] Carl Zeiss SMT GmbH 1 MEASURING DEVICE, LITHOGRAPHING PLANT AND METHOD FOR CALIBRATING A MEASURING DEVICE The present invention relates to a measuring device for measuring a resistance-dependent measurand on or in an optical system of a lithography system, a lithography system with such a measuring device, and a method for calibrating such a measuring device of a lithography system. The content of priority application DE 10 2024 205 482.8 is fully incorporated by reference. Microlithography is used for the production of microstructured components, such as integrated circuits. The microlithography process is carried out with a lithography system.which comprises an illumination system and a projection system. The image of a mask (reticule) illuminated by the illumination system is projected by the projection system onto a substrate, for example a silicon wafer, coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection system, in order to transfer the mask structure onto the photosensitive coating of the substrate. Driven by the pursuit of ever smaller structures in the production of integrated circuits, EUV lithography systems are currently being developed that use light with a wavelength in the range of 0.1 nm to 30 nm, particularly 13.5 nm. Since most materials absorb light of this wavelength, such EUV lithography systems must use reflective optics, i.e., mirrors, instead of—as previously—refractive optics, i.e., lenses.Carl Zeiss SMT GmbH 2 Temperature sensors can be used in various areas of lithography systems. Such temperature sensors serve, for example, to quantify thermal deformations of mirrors due to absorption of the radiation emitted by the EUV light source. The optical deformations of the mirror can lead to impairments in the imaging using the projection lens. To counteract thermal deformations, a highly precise temperature measurement with an absolute accuracy better than 50 mK, or even better than 5 mK, is required. It is known to use thermal resistors (heat-dependent or temperature-dependent resistors) for temperature measurement. These provide a temperature-dependent resistance from which the temperature can be derived. In order to enable highly precise temperature measurement and reduce the influence of errors,EP 0120102 A1 proposes a measuring device in which reference resistors and measuring resistors are sequentially energized. A voltage across each resistor is detected and used to determine a temperature with high accuracy. Against this background, an object of the present invention is to improve the measurement of a resistance-dependent quantity at or in an optical system of a lithography system. According to a first aspect, a measuring device for measuring a resistance-dependent quantity at or in an optical system of a lithography system is proposed. The measuring device comprises: a current source for generating a measuring current, a measuring line branch and a reference line branch, and a switching unit for selectively connecting the current source in a reference switching position to the reference line branch or in a measuring switching position to the measuring line branch.Carl Zeiss SMT GmbH 3 a connection unit arranged on the measuring line branch for the optional electrical connection of a measuring resistor or at least one calibration component, a reference resistor arranged on the reference line branch, a voltage detection unit for detecting a voltage optionally on the reference line branch or the measuring line branch, and a control unit for determining a parasitic resistance value of the measuring device based on a reference voltage detected in the reference switching position and a voltage detected in the measuring switching position in which one of the at least one calibration component is connected to the connection unit,The measured voltage can be determined by calculating the parasitic resistance of the measuring device. This allows for more accurate measurement of resistance-dependent variables (e.g., temperature). For example, components integrated into the measuring path can introduce measurement errors. Even minute leakage currents from capacitors or insulation resistances can prevent the measuring current from flowing completely through the object being measured. Similarly, voltage drops caused by line resistances (e.g., conductor resistances) or connector contact resistances can lead to measurement errors.Regarding measurement errors. Using the proposed measuring device, such leakage resistances (i.e., also leakage currents) and line resistances can be determined and taken into account during a subsequent measurement of the resistance-dependent measurand (e.g., a temperature). Because the components used to measure the resistance-dependent measurand (e.g., the reference resistor, the reference line branch, and the measuring line branch) in the proposed measuring device are also used to determine the parasitic resistance value, the measuring device can be manufactured easily. Furthermore, calibration of the measuring device, i.e., determining the parasitic resistance value of the measuring device, is possible.This can be performed regularly and at short intervals between measurements of the resistance-dependent measurand during operation. This continuous recalibration thus enables more accurate measurements, especially in systems with dynamically changing environmental influences. Furthermore, the calibration component is connected to the same connection unit to which the measuring resistor is connected during the measurement of the resistance-dependent measurand. This means that the same current transmission path (e.g., the same conductor tracks and / or cables) is evaluated and calibrated up to the connection unit during the calibration process.which is also used in the subsequent measurement process for measuring the resistance-dependent quantity. In particular, the same current transmission path up to the connection unit is used continuously and in the same condition as in the subsequent measurement process during both the calibration and measurement processes. The lithography system (projection exposure system) is, for example, an EUV or a DUV lithography system. EUV stands for "extreme ultraviolet" and refers to a wavelength of the working light in the range of 0.1 nm to 30 nm, specifically 13.5 nm. Furthermore, DUV stands for "deep ultraviolet".DUV) and denotes a wavelength of the working light between 30 nm and 250 nm. The EUV or DUV lithography system comprises an illumination system and a projection system. In particular, the EUV or DUV lithography system projects the image of a Carl Zeiss SMT GmbH 5 mask (reticule) illuminated by the illumination system onto a substrate, for example a silicon wafer, coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection system, using the projection system.to transfer the mask structure onto the photosensitive coating of the substrate. The optical system is preferably a projection optic of the lithography system or part of a projection optic of the lithography system. However, the optical system can also be an illumination optic of the lithography system or part of an illumination optic of the lithography system. The optical system can comprise an optical element (for example, a mirror or a lens), a sensor, and / or an actuator. The measuring device can be used to measure a resistance-dependent quantity (e.g., a temperature) in any part of the lithography system. For example, a resistance-dependent quantity is measured at a measurement object of the lithography system using the measuring device. The measurement object is, for example, an optical element (for example, a mirror or a lens).an actuator or the like. For example, the measuring resistor is arranged in physical contact with the object being measured (e.g., an optical element). In the case of a measuring device for measuring temperature (temperature measuring device), the measuring resistor can also be considered a temperature resistor and / or temperature sensor. Temperature measurement is useful, for example, for determining thermal deformation of optical elements. Furthermore, determining the temperature is also important for diagnostics, especially for determining the aging of the lithography system. Carl Zeiss SMT GmbH 6 The measuring device is particularly suitable for determining the measured quantity with high accuracy. In the case of temperature measurement, "high accuracy" is understood, for example, to mean an absolute accuracy between 5 and 50 mK, preferably between 5 and 20 mK. High-precision temperature measurements are particularly important in lithography.because this allows for the provision of highly precise optics. The current source is, for example, a direct current source. Alternatively, the current source can also be an alternating current source, which, for example, delivers a square wave or a sine wave. Furthermore, the current source is, for example, a modulating current source, which can generate a measuring current with a variable current intensity. For illustrative purposes only, the current source includes a digital-to-analog converter, so that an output measuring current can be varied with an analog voltage signal from the digital-to-analog converter. The measuring resistor is an electrical resistance.whose electrical resistance value changes depending on a resistance-dependent measured quantity. By determining the electrical resistance value of the measuring resistor, the measured quantity can thus be derived from the determined resistance value. The term "measuring resistor" here refers to a component (i.e., a measuring resistor element), and not to an abstract resistance in the sense of a resistance value. The measuring resistor is, for example, a temperature resistor, i.e., a heat resistance and / or thermal resistance. The electrical resistance value of such a temperature resistor changes depending on the temperature at the temperature resistor. Thus, the temperature at the temperature resistor can be derived from the electrical resistance value. Carl Zeiss SMT GmbH 7 The reference resistor is also an electrical resistor. The reference resistor is, in particular, a high-precision resistor,whose resistance value is known as precisely as possible. The reference resistor, for example, has a very small absolute tolerance and is highly resistant to aging. The reference resistor can also be temperature-independent. In particular, the reference resistor is an electrical resistor with a predetermined reference resistance value. The measuring resistor and the reference resistor can be identical. Alternatively, the reference resistor is, for example, a resistor of the first type, while the measuring resistor is a resistor of the second type. Preferably, the reference resistor is a resistor that enables a more precise measurement than the measuring resistor. The measuring resistor can be arranged on or in the optical system (e.g., in physical contact with a measurement object of the optical system) in order to detect the measured quantity (e.g., temperature). The measuring resistor serves, in particular, toto measure the quantity of the object being measured (e.g., an optical element, a mirror, a lens, an actuator, or the like). In contrast, the reference resistor can be spaced and / or located away from the object being measured. The terms "reference resistor" and "calibration resistor" used herein also refer to a component (i.e., a resistive element) and not to an abstract resistance in the sense of a resistance value. The at least one calibration component, for example, has at least one calibration resistor and / or a short-circuit bridge. A calibration resistor is an electrical resistor. A given calibration resistor is, in particular, an electrical resistor with a predetermined calibration resistance value. The connection unit is, in particular, an electrical connection unit to which either the measuring resistor or the at least one calibration component can be electrically connected. That is to say,that at any given time only either the measuring resistor or one of the at least one calibration component is electrically connected to the connection unit, while the other is provided electrically disconnected from the connection unit and can be electrically connected to the connection unit. The connection unit has, in particular, at least one electrical connection element for selective electrical connection to the measuring resistor or the at least one calibration component. Furthermore, each of the measuring resistor and the at least one calibration component has at least one further electrical connection element for electrical connection to the connection unit, i.e., to the at least one electrical connection element of the connection unit. The at least one electrical connection element of the connection unit is therefore designed in such a way that...that it is electrically connectable to each of at least one other electrical connection element. That the measuring resistor and / or the calibration component is / are provided electrically unconnected to the connection unit includes that the measuring resistor and / or the calibration component is / are provided physically completely unconnected to the connection unit and can, for example, be electrically connected to the connection unit manually. It also includes a case in which the measuring resistor and the calibration component are provided switchably (i.e., electrically connectable) to the connection unit via another switching unit. Carl Zeiss SMT GmbH 9 The measuring device includes, in particular, for example, the measuring resistor and the calibration component. The measuring line branch and the reference line branch are each, in particular, electrical lines. An electrical line includes, for example, an electrical cable,a wire and / or a conductor track (e.g., on a printed circuit board). The reference line branch is preferably designed as a conductor track (e.g., on a printed circuit board). The measuring line branch is preferably designed as a conductor track (e.g., on the printed circuit board) in a first line section and as an electrical cable and / or wire in a second line section. The measuring line branch can also have a third line section, which is designed as a conductor track on another printed circuit board. For example, the first section of the measuring line branch is arranged closer to the power source than the second section of the measuring line branch. Furthermore, for example, the second section of the measuring line branch is arranged closer to the connection unit than the first section of the measuring line branch. The measuring device particularly includes a circuit in which the power source, the voltage sensing unit,The switching unit and either the measuring line branch or the reference line branch are electrically connected. The fact that the connection unit is arranged on the measuring line branch means, in particular, that the connection unit is electrically conductive within the measuring line branch and is electrically connected to the measuring line branch. The fact that the reference resistor is arranged on the reference line branch means, in particular, that the reference resistor is electrically conductive within the Carl Zeiss SMT GmbH 10 reference line branch and is electrically connected to the reference line branch. Using the switching unit, either the measuring line branch or the reference line branch can be electrically connected to the power source, so that either the measuring line branch or the reference line branch is energized with the measuring current. That is to say,The measuring line branch and the reference line branch are energized individually and sequentially (e.g., alternately). The switching unit has, for example, a first and a second switching element. Using the first switching element, the switching unit can establish an electrical connection between a first connection point of the power source and, optionally, a corresponding first line point of the measuring line branch or the reference line branch. Furthermore, using the second switching element, the switching unit can establish an electrical connection between a second connection point of the power source and, optionally, a corresponding second line point of the measuring line branch or the reference line branch. The switching unit is specifically designed to...to switch the two switching elements simultaneously. The switching unit is, in particular, a controllable circuit. The switching unit includes, for example, a multiplexer. For example, the switching unit, e.g., each of the switching elements of the switching unit, has two different switching states. For example, the first switching element has an input port connected to the power source and two output ports. For example, the second switching element has an output port connected to the power source and two input ports. Carl Zeiss SMT GmbH 11 The voltage sensing unit is, in particular, arranged in a parallel circuit to a first and second line node of the circuit of the measuring device, wherein the first line node is electrically connected to the first switching element of the switching unit and the second line node is electrically connected to the second switching element of the switching unit. That is,The measuring device can be switched between a reference switching position and a measuring switching position using the switching unit. In the reference switching position, the reference branch with the reference resistor is energized with the measuring current. Furthermore, in the reference switching position, the voltage sensing unit is connected in parallel to the reference branch, and thus to the reference resistor. This means that in the reference switching position, the voltage sensing unit measures a voltage drop across the reference branch (reference voltage, e.g., the voltage drop across the reference resistor). In the measuring switching position, the measuring branch with the connection unit is energized with the measuring current. If the connection unit is electrically connected to the measuring resistor, then in the measuring switching position, the measuring resistor is energized.In the measuring switch position, the connection unit is electrically connected to one of the at least one calibration component, thus energizing this calibration component. Furthermore, in the measuring switch position, the voltage sensing unit is connected in parallel to the measuring line branch. This means that the voltage sensing unit measures a voltage drop across the measuring line branch in the measuring switch position. To determine the parasitic resistance value of the measuring device, the reference line branch and the measuring line branch are energized with the same measuring current.i.e., also with the same current value of the measuring current. Carl Zeiss SMT GmbH 12 In particular, the measuring current is generated (i.e., switched on) with a specific current strength, and then switching is performed between energizing the reference line branch and the measuring line branch without changing the measuring current. For example, the connection unit of the measuring line branch is first electrically connected to one of the at least one calibration component. Then the measuring device is switched to the reference switching position, and a reference voltage value UR of the reference line branch, i.e., the reference resistance, is determined. Subsequently, the measuring device is switched to the measuring switching position, and a measuring voltage value U, M of the measuring line branch, i.e., including the calibration component. Since the same current I flows through the respective line branch in both switching positions, the following applies: I = UR / RR = UM / RM.Here, RR is the predetermined resistance value of the reference resistor. Furthermore, R M A resistance value of the measuring line branch, which includes a parasitic resistance value RP. Consequently, the resistance value R can be determined from the voltage measurement of UR and UM and with a known resistance value RR of the reference resistor. M of the measuring line branch: R M = (UM / UR) ∙ RR.In the case that the calibration component is a short-circuit bridge, RM is determined as the parasitic resistance value RP of the measuring device (in particular as the line resistance of the measuring line branch). With the short-circuit bridge, the parasitic effect on the signal path (line resistance) is measured. From a circuit design perspective, the line resistance can be described by a series connection. Carl Zeiss SMT GmbH 13. In the case that the calibration component is a calibration resistor, a parasitic resistance value RP of the measuring device (in particular as the leakage resistance of the measuring line branch) is determined from RM, taking into account a predetermined resistance value RK of the calibration resistor. The calibration resistor is thus used to check whether leakage currents flow in parallel to the measuring circuit. From a circuit design perspective, this can be described as a parallel connection of parasitic resistance RP and calibration resistor RK.This allows the relationship R to be established for parallel circuits. M = (R K ∙ R P ) / (R K + R P) can be applied. Thus, the parasitic resistance value RP of the measuring device can be calculated from the predetermined resistance value RK of the calibration resistor and the determined resistance value RM of the measuring line branch. The parasitic resistance value of the measuring device therefore includes, for example, a leakage resistance and / or a line resistance of the measuring device. The voltage sensing unit can include a voltmeter and / or an analog-to-digital converter. The voltage sensing unit is suitable for measuring the voltage drop across the measuring line branch or reference line branch connected to the current source. The control unit can be implemented as hardware and / or software. If the control unit is implemented as hardware, it can be embodied as a device, e.g., as a computer or processor, or as part of a system, e.g., a computer system.If the control unit is implemented as software, Carl Zeiss SMT GmbH 14 states that it can be designed as a computer program product, a function, program code, or an executable object. The control unit serves, in particular, to evaluate the voltage values ​​acquired by the voltage acquisition unit in order to determine the parasitic resistance value of the measuring device. For example, the control unit is configured to determine the parasitic resistance based on the acquired reference voltage and a predetermined reference resistance value of the reference resistor. Furthermore, the control unit can also be configured to determine the resistance-dependent measured quantity. For this purpose, the measuring device is switched to the measuring position, the connection unit is electrically connected to the measuring resistor, and a measuring voltage U is applied to the voltage acquisition unit. TThe voltage across the measuring line is measured. For example, the control unit then calculates the resistance value at the measuring resistor based on the voltage value UT – e.g., taking into account a reference resistance value previously measured in the reference switching position and / or the pre-determined parasitic resistance. Using a pre-stored resistance-measurement characteristic curve (e.g., resistance-temperature characteristic curve) and / or a pre-stored function that specifies a relationship between the resistance value and the measured quantity, the control unit can determine the measured quantity (e.g., temperature) in or at the optical system. By taking the voltage across the reference resistor into account, gain errors in the voltage sensing unit can, for example, be eliminated.In embodiments, the control unit is configured to control the switching unit so that the switching unit selectively connects the power source to either the measuring line branch or the reference line branch. Carl Zeiss SMT GmbH 15 According to one embodiment, the at least one calibration component has at least one calibration resistor. Furthermore, the control unit is configured to determine the parasitic resistance value based on the detected reference voltage of the reference resistor, a predetermined reference resistance value of the reference resistor, the measured voltage detected in the measuring switching position in which one of the at least one calibration resistor is connected to the connection unit, and a predetermined calibration resistance value of one of the calibration resistors.The following relationship applies to the resistance value RM of the measuring line branch, based on a parallel circuit consisting of the calibration resistor and a parasitic resistance: R. M = (R K ∙ R P ) / (R K + R PThis allows the parasitic resistance value RP of the measuring device to be determined from the known calibration resistance value RK and the determined resistance value RM of the measuring line branch. According to a further embodiment, the at least one calibration component has a short-circuit bridge. Furthermore, the control unit is configured to determine the parasitic resistance value based on the detected reference voltage of the reference resistor, a predetermined reference resistance value of the reference resistor, and the measured voltage detected in the measuring switch position in which the short-circuit bridge is connected to the connection unit. In the case that the calibration component is a short-circuit bridge, the parasitic resistance value RP of the measuring device (in particular as the line resistance of the measuring line branch) is determined directly as the resistance value RM of the measuring line branch: R P = R M = UM ∙ (R R / U RAccording to a further embodiment, the control unit is configured to determine the resistance-dependent measured quantity based on a reference voltage of the reference resistor detected in the reference switching position, a further measured voltage detected in the measuring switching position in which the measuring resistor is connected to the connection unit of the measuring line branch, and the determined parasitic resistance value of the measuring device. After the parasitic resistance value RP of the measuring device has been determined, this result can be taken into account when measuring the resistance-dependent measured quantity (e.g., a temperature). For this purpose, after determining the parasitic resistance value by the user in the reference switching position and the measuring switching position with the at least one calibration component, the connection unit of the measuring line branch is electrically disconnected from the calibration component and instead electrically connected to the measuring resistor.The measuring device is then, for example, first switched back to the reference switching position, and the reference voltage of the reference resistor is determined. Next, the measuring device is switched to the measuring switching position. Now, another measured voltage value UT of the measuring line branch with the measuring resistor is determined. The uncalibrated resistance value RT of the measuring resistor can then be calculated as follows: R. T = U T / I = U T ∙ (R R / U R ). Carl Zeiss SMT GmbH 17 The same measuring current I is also applied in the measuring switching position as in the previously executed reference switching position. In order to determine a more precise resistance value RT, the control unit also takes into account the voltage drop U across the measuring resistor. T furthermore, the voltage drop U across the reference resistor RBy taking into account the voltage drop UR across the reference resistor when calculating the resistance value RT, errors affecting both measurements UR and UT are eliminated (ratiometric principle). These errors primarily concern the offset and gain errors. The resistance value RT can thus be calculated more accurately. Additionally, the control unit now considers the previously determined parasitic resistance value RP. For example, the determined uncalibrated resistance value R T to determine the parasitic resistance value R P corrected. For example, the determined resistance value R TThe parasitic resistance value RP is subtracted. This allows the resistance value RT to be calculated even more accurately. From the resistance value RT' calibrated in this way, the control unit then determines a measured quantity (e.g., a temperature) by applying a pre-stored resistance-measured quantity characteristic curve. According to a further embodiment, the connection unit has one or more connecting elements for detachable electrical connection, optionally with one or more first corresponding connecting elements of the measuring resistor or with one or more second corresponding connecting elements of the at least one calibration component. This allows the measuring resistor to be electrically connected to and disconnected from the connection unit. Additionally, the at least one Carl Zeiss SMT GmbH 18 calibration component (i.e.,In the case of multiple calibration components, each of the multiple calibration components can be electrically connected to and disconnected from the connection unit. The detachable electrical connection is, in particular, a non-destructively detachable electrical connection. The detachable electrical connection is, in particular, repeatedly detachable and connectable. For example, the detachable electrical connection may have a plug connection. For instance, one or more connection elements of the connection unit may be one or more connection elements of a plug connection, i.e., one or more plug elements or one or more sockets for receiving a corresponding plug element. Furthermore, one or more first and second corresponding connection elements of the measuring resistor or the calibration component may each be, for example, one or more connection elements of a plug connection.One or more plug-in elements or one or more sockets for receiving a corresponding plug-in element. According to a further embodiment, the measuring device comprises the measuring resistor, at least one calibration component, and a further switching unit which is electrically connected to the connection unit, wherein the further switching unit is configured to selectively connect either the measuring resistor or the at least one calibration component electrically to the connection unit. The further switching unit is, in particular, a controllable circuit.For example, the control unit is configured to control the further switching unit such that in a first switching state of the further switching unit, the measuring resistor is electrically connected to the connection unit; in a second switching state of the further switching unit, one of the at least one calibration component is electrically connected to the connection unit; in a third switching state of the further switching unit, another of the at least one calibration component is electrically connected to the connection unit, and so on. That is, with the help of the further switching unit, exactly one of the measuring resistors and one of the at least one calibration component is electrically connected to the connection unit at any given time. In other words, with the help of the further switching unit, either the measuring resistor or one of the at least one calibration component is electrically connected to the connection unit at any given time.The additional switching unit has, in particular, an electrical input port which is electrically connected to the connection unit. Furthermore, the additional switching unit has, in particular, several output ports, each output port being electrically connected to one of the measuring resistors and the at least one calibration component. The additional switching unit is configured to electrically connect the input port to one of the several output ports. The additional switching unit is, for example, a multiplexer. In embodiments, the control unit is configured to control the additional switching unit so that the additional switching unit selectively connects either the measuring resistor or the at least one calibration component electrically to the connection unit.According to a further embodiment, the measuring device comprises the measuring resistor, at least one first calibration component in the form of at least one calibration resistor, a second calibration component in the form of a short-circuit bridge, and a further switching unit which is electrically connected to the connection unit, wherein the further switching unit is configured to electrically connect either the measuring resistor, the at least one calibration resistor, or the short-circuit bridge to the connection unit. According to a further embodiment, the at least one calibration component comprises several calibration resistors with different calibration resistance values. In addition, the connection unit of the measuring line branch is electrically connected in the measuring switching position to a calibration resistor preselected from the several calibration resistors.Furthermore, the preselected calibration resistor is chosen such that its calibration resistance value deviates by 30% or less, 20% or less, and / or 10% or less from a pre-estimated resistance value of the parasitic resistance. By selecting a calibration resistor whose calibration resistance value deviates only slightly from the resistance value of the parasitic resistance, the parasitic resistance value can be determined even more accurately. According to another embodiment, the current source includes a digital-to-analog converter for generating a variable measuring current, and / or the voltage sensing unit includes an analog-to-digital converter for converting a detected analog voltage value into a digital voltage signal. The digital-to-analog converter receives a digital input voltage and converts it into an analog signal.This analog signal controls a current-generating unit of the power source to deliver a measuring current with the corresponding current intensity. The analog-to-digital converter converts the analog voltage drop across the corresponding line branch into a digital signal and outputs it as a Carl Zeiss SMT GmbH 21 output signal. The output signal is then passed on to the control unit. According to another embodiment, the reference line branch is shorter than the measuring line branch, and / or the reference line branch is shorter by a factor of 2 or more, a factor of 5 or more, a factor of 10 or more, or a factor of 100 or more than the measuring line branch. That is, the reference resistor is located close to the power source and the voltage sensing unit. In contrast, the measuring line branch is relatively long, i.e., the connection unit and thus the measuring resistor connected to the connection unit (e.g.,The temperature sensor is located further away from the power source and the voltage sensing unit. Therefore, the parasitic resistance (e.g., the line resistance) of the measuring line branch is relatively high. The reason for the long measuring line branch is, for example, a remotely located object whose temperature is to be measured. Because the same (e.g., long) measuring line branch is used to determine both the parasitic resistance and the measured quantity (e.g., the temperature), the measured quantity can be determined accurately despite the long measuring line branch. The measuring line branch extends, in particular, from the connection points that are contacted by the switching unit in the measuring switch position to the connection unit.The measuring line branch extends, for example, from a first line point of the measuring line branch, which is contacted by a first switching element of the switching unit in the measuring switching position, to a first terminal pole of the connection unit and from a second terminal pole of the connection unit to a second line point of the measuring line branch, which is contacted by a second switching element of the switching unit in the measuring switching position.Carl Zeiss SMT GmbH 22 According to a further embodiment, the measuring device further comprises several measuring line branches, wherein a connection unit for the optional electrical connection of a measuring resistor or at least one calibration component is arranged on each measuring line branch, the switching unit for the optional connection of the current source in the reference switching position with the reference line branch or in several measuring switching positions accordingly with the several measuring line branches is configured, the voltage detection unit for the optional detection of a voltage is configured either on the reference line branch or on the several measuring line branches, and the control unit for determining a respective parasitic resistance value of the measuring device for each measuring line branch is configured based on the detected reference voltage and the corresponding of the several detected measuring voltages on the several measuring line branches.The multiple measuring line branches, each with a connection unit for optionally connecting a measuring resistor or at least one calibration component, can be used to measure multiple objects of the lithography system. For example, the multiple objects can be measured with the measuring device using one and the same current source and voltage sensing unit, with each measurement occurring at a different time. For example, the switching unit, e.g., each of the switching elements of the switching unit, has more than two switching states. For example, a first switching element has one input port and more than two output ports. For example, a second switching element has one output port and more than two input ports. In particular, the number of output ports of the first switching element is equal to the number of input ports of the second switching element.Furthermore, the number of output ports of the first switching element and the number of input ports of the second switching element are one greater than the number of multiple measuring line branches. According to another embodiment, the measuring device also includes a circuit board on which the current source, the voltage sensing unit, the switching unit, the reference line branch, and the reference resistor are arranged. The circuit board is, in particular, a printed circuit board on which the individual components mentioned above are plugged, glued, and / or soldered. The circuit board forms a module that can advantageously be used as a whole. The circuit board can also include an interface unit for connecting at least a second line section of the measuring line branch. In embodiments, the measuring device is configured to reverse the direction of the measuring current.By differentially measuring the voltage sensing unit (before and after the current direction reversal), offset errors of the voltage sensing unit can be factored out. A lithography system is proposed according to a second aspect. The lithography system comprises a measuring device as described above and an optical system, wherein the measuring resistor of the measuring device is arranged on or in the optical system. The optical system comprises, for example, an optical element (e.g., a mirror or a lens) and / or an actuator for an optical element. In the case of a measuring device that has several measuring line branches and thus several measuring resistors, one measuring resistor is arranged on or in the optical system. For example, several or all of the several measuring resistors are located on a single object being measured (e.g.,The optical element of the optical system is arranged and / or the multiple measuring resistors (e.g., each) are arranged on different measurement objects (e.g., optical elements). In embodiments, the lithography system further comprises: a first enclosed area in which the optical system, the connection unit, the measuring resistor, and the at least one calibration component are arranged; a second enclosed area, which is spatially separated from the first enclosed area and in which the current source and the voltage sensing unit are arranged; and connecting lines that electrically connect the first enclosed area and the second enclosed area such that the current source of the connection unit (and thus optionally the measuring resistor or the at least one calibration component) supplies the measuring current, wherein the connecting lines comprise at least a section of the measuring line branch.For example, the reference resistor, the reference line branch, and / or the switching unit are located in the second enclosed area. If a further switching unit is provided for direct electrical connection to the connection unit, it is located, for example, in the first enclosed area. The two enclosed areas are preferably separated by several meters, e.g., more than ten meters and / or more than twenty meters. "Enclosed" means, in particular, that the areas are formed in housings and are delimited by them. The connecting lines serve, in particular, for the electrical coupling of the two areas. For example, a vacuum prevails in the first enclosed area, and there is no vacuum in the second enclosed area. According to a third aspect, a method for calibrating a measuring device of a lithography system is proposed.The measuring device is, in particular, a measuring device as described above. Furthermore, the measuring device is configured to measure a resistance-dependent quantity in or on an optical system of the lithography system.The method comprises the following steps: a) generating a measuring current, b) successively energizing a reference line branch and a measuring line branch of the measuring device with the measuring current, wherein the reference line branch has a reference resistor, and the measuring line branch has a connection unit that is electrically conductively connected to a calibration component and alternatively electrically connectable to a measuring resistor, c) detecting a reference voltage at the reference line branch when the reference line branch is energized, and detecting a measuring voltage at the measuring line branch when the measuring line branch is energized, and d) determining a parasitic resistance value of the measuring device based on the detected reference voltage and the detected measuring voltage. The fact that the reference line branch and the measuring line branch are energized sequentially means, in particular, that they can be selectively and / or alternately (i.e.,Each branch of the line is energized at least once. In other words, the measuring branch is energized at a first time and / or during a first period, and the reference branch is energized at a second time and / or during a second period. The first and second times are different from each other, the first and second periods are different from each other (e.g., disjoint), and / or the first and second periods do not overlap.According to one embodiment of the third aspect, the method according to step d) comprises: disconnecting the electrically conductive connection between the terminal unit of the measuring line branch and the calibration component, electrically connecting the terminal unit to the measuring resistor, energizing the measuring line branch with the measuring current, detecting a further measuring voltage at the measuring line branch when the measuring line branch is energized, and determining the resistance-dependent measured quantity based on the detected reference voltage of the reference resistor, the detected further measuring voltage at the measuring line branch, and the determined parasitic resistance value of the measuring device. In particular, the method according to this embodiment is a method for measuring a resistance-dependent measured quantity in or on an optical system of the lithography system.Furthermore, the method for measuring the resistance-dependent quantity includes the calibration procedure for the measuring device described above. "One" in this context is not necessarily to be understood as limiting to exactly one element. Rather, several elements, such as two, three, or more, may also be provided. Likewise, every other counter used here is not to be understood as limiting the number of elements to the specified number. Rather, numerical deviations both upwards and downwards are possible unless otherwise stated. The embodiments and features described for the measuring device apply accordingly to the lithography system and the proposed method, and vice versa.Further possible implementations of the invention also include combinations of features or embodiments described previously or subsequently with regard to the exemplary embodiments, even if not explicitly mentioned. In such cases, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention. Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention is further explained below with reference to preferred embodiments and the accompanying figures. Fig. 1 shows a schematic meridional section of a projection exposure system for EUV projection lithography according to one embodiment; Fig. 2 shows a measuring device of the projection exposure system from Fig. 1 according to a first embodiment, showing a reference switching position of the measuring device; Fig.Figure 3 shows the measuring device from Figure 2 in a measuring switching position, with a calibration resistor connected to a measuring line branch of the measuring device; Figure 4 shows the measuring device from Figure 2 in the measuring switching position, with a measuring resistor connected to the measuring line branch of the measuring device; Figure 5 shows a measuring device of the projection exposure system from Figure 1 according to a second embodiment; Figure 6 shows a measuring device of the projection exposure system from Figure 1 according to a third embodiment; and Figure 7 shows a flowchart of a method for calibrating a measuring device of a projection exposure system according to one embodiment. In the figures, identical or functionally equivalent elements have been provided with the same reference numerals unless otherwise indicated.Furthermore, it should be noted that the illustrations in the figures are not necessarily to scale. Fig. 1 shows an embodiment of a projection exposure system 1 (lithography system), in particular an EUV lithography system. One embodiment of a lighting system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, a lighting optic 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the rest of the lighting system 2. In this case, the lighting system 2 does not include the light source 3. Carl Zeiss SMT GmbH 29 A reticle 7 arranged in the object field 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 can be moved via a reticle displacement drive 9, in particular in a scanning direction. In the Fig.Figure 1 shows a Cartesian coordinate system with an x-direction x, a y-direction y, and a z-direction z. The x-direction x runs perpendicular to the plane of the drawing. The y-direction y runs horizontally, and the z-direction z runs vertically. In Figure 1, the scan direction runs along the y-direction y. The z-direction z runs perpendicular to the object plane 6. The projection exposure system 1 includes a projection optic 10. The projection optic 10 serves to image the object field 5 onto an image field 11 in an image plane 12. The image plane 12 is parallel to the object plane 6. Alternatively, an angle other than 0° between the object plane 6 and the image plane 12 is also possible. A structure on the reticulum 7 is imaged onto a light-sensitive layer of a wafer 13 located in the image plane 12 within the image field 11. The wafer 13 is held by a wafer holder 14.The wafer holder 14 can be moved, in particular along the y-direction y, via a wafer transfer drive 15. The movement of the reticle 7 via the reticle transfer drive 9 and of the wafer 13 via the wafer transfer drive 15 can be synchronized. The light source 3 is an EUV radiation source. The light source 3 emits, in particular, EUV radiation 16, which is also referred to below as useful radiation, illumination radiation, or illumination light. The useful radiation 16 has a wavelength in the range between 5 nm and 30 nm. The light source 3 can be a plasma source Carl Zeiss SMT GmbH 30, for example an LPP source (Laser Produced Plasma, plasma generated with the aid of a laser) or a DPP source (Gas Discharged Produced Plasma, plasma generated by means of a gas discharge).It can also be a synchrotron-based radiation source. The light source 3 can be a free-electron laser (FEL). The illumination radiation 16 emanating from the light source 3 is focused by a collector 17. The collector 17 can be a collector with one or more ellipsoidal and / or hyperboloid reflective surfaces. The at least one reflective surface of the collector 17 can be illuminated by the radiation 16 at grazing incidence (GI), i.e., with angles of incidence greater than 45°, or at normal incidence (NI), i.e., with angles of incidence less than 45°. The collector 17 can be structured and / or coated on the one hand to optimize its reflectivity for the useful radiation and on the other hand to suppress stray light.After the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 can represent a separation between a radiation source module, comprising the light source 3 and the collector 17, and the illumination optics 4. The illumination optics 4 includes a deflecting mirror 19 and, downstream of this in the radiation path, a first faceted mirror 20. The deflecting mirror 19 can be a planar deflecting mirror or, alternatively, a mirror with an effect that influences the beam beyond the mere deflection effect. Alternatively or additionally, the deflecting mirror 19 can be designed as a spectral filter that separates a useful wavelength of the illumination radiation 16 from stray light of a different wavelength.If the first faceted mirror 20 is arranged in a plane of the illumination optics 4 that is optically conjugate to the object plane 6 as a field plane, it is also referred to as a field faceted mirror. The first faceted mirror 20 comprises a plurality of individual first facets 21, which can also be called field facets. Only a few of these first facets 21 are shown as examples in Fig. 1. The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or semicircular edge contour. The first facets 21 can be designed as planar facets or alternatively as convexly or concavely curved facets. As is known, for example, from DE 102008009600 A1, the first facets 21 themselves can each also be composed of a large number of individual mirrors, in particular a large number of micromirrors.The first faceted mirror 20 can be designed, in particular, as a microelectromechanical system (MEMS system). For details, reference is made to DE 102008009600 A1. Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e., along the y-direction y. In the beam path of the illumination optics 4, a second faceted mirror 22 is arranged downstream of the first faceted mirror 20. If the second faceted mirror 22 is arranged in a pupil plane of the illumination optics 4, it is also referred to as a pupil faceted mirror. The second faceted mirror 22 can also be arranged at a distance from a pupil plane of the illumination optics 4. In this case, the combination of the first faceted mirror 20 and the second faceted mirror 22 is also referred to as a specular reflector. Carl Zeiss SMT GmbH 32 Specular reflectors are known from US 2006 / 0132747 A1, EP 1614 008 B1 and US 6,573,978.The second faceted mirror 22 comprises a plurality of second facets 23. In the case of a pupil faceted mirror, the second facets 23 are also referred to as pupil facets. The second facets 23 can also be macroscopic facets, which may, for example, have round, rectangular, or hexagonal borders, or alternatively, facets composed of micromirrors. In this regard, reference is also made to DE 102008009600 A1. The second facets 23 can have planar or, alternatively, convex or concave curved reflective surfaces. The illumination optics 4 thus forms a doubly faceted system. This basic principle is also referred to as a honeycomb condenser (English: Fly's Eye Integrator). It may be advantageous not to arrange the second faceted mirror 22 exactly in a plane which is optically conjugate to a pupil plane of the projection optics 10.In particular, the second faceted mirror 22 can be tilted relative to the pupil plane of the projection optics 10, as described, for example, in DE 102017220586 A1. The second faceted mirror 22 images the individual first facets 21 into the object field 5. The second faceted mirror 22 is the last beam-shaping or, indeed, the last mirror for the illumination radiation 16 in the beam path before the object field 5. Carl Zeiss SMT GmbH 33 In another embodiment of the illumination optics 4, not shown, a transmission optic can be arranged in the beam path between the second faceted mirror 22 and the object field 5, which contributes in particular to imaging the first facets 21 into the object field 5. The transmission optics can have exactly one mirror, or alternatively two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 4.The transmission optics can, in particular, comprise one or two mirrors for perpendicular incidence (NI mirrors, normal incidence mirrors) and / or one or two mirrors for grazing incidence (GI mirrors, grazing incidence mirrors). In the embodiment shown in Fig. 1, the illumination optics 4 has exactly three mirrors after the collector 17, namely the deflecting mirror 19, the first faceted mirror 20, and the second faceted mirror 22. In a further embodiment of the illumination optics 4, the deflecting mirror 19 can also be omitted, so that the illumination optics 4 can then have exactly two mirrors after the collector 17, namely the first faceted mirror 20 and the second faceted mirror 22. The imaging of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optic into the object plane 6 is regularly only an approximation.The projection optics 10 comprise a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1. In the example shown in Fig. 1, the projection optics 10 comprise six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or any other number of mirrors Mi are also possible. The projection optics 10 is a double-obscured optic. The penultimate mirror M5 and the last mirror M6 each have a passage for the illumination radiation 16. The projection optics 10 has an image-side numerical aperture that is greater than 0.5 and can also be greater than 0.6, for example, 0.7 or 0.75. The reflective surfaces of the mirrors Mi can be designed as freeform surfaces without an axis of rotational symmetry.Alternatively, the reflective surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one axis of rotational symmetry of the reflective surface shape. The mirrors Mi, like the mirrors of the illumination optics 4, can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon. The projection optics 10 has a large object-image offset in the y-direction y between a y-coordinate of a center of the object field 5 and a y-coordinate of the center of the image field 11. This object-image offset in the y-direction y can be approximately as large as a z-distance between the object plane 6 and the image plane 12. The projection optics 10 can, in particular, be anamorphic. In particular, it exhibits different image scales βx, βy in the x and y directions x, y.The two image scales βx, βy of the projection optics 10 are preferably (βx, βy) = (+ / - 0.25, + / - 0.125). A positive image scale β means imaging without image inversion. A negative sign for the image scale β means imaging with image inversion. The projection optics 10 thus results in a reduction ratio of 4:1 in the x-direction x, that is, in the direction perpendicular to the scan direction. Carl Zeiss SMT GmbH 35 The projection optics 10 results in a reduction ratio of 8:1 in the y-direction y, that is, in the scan direction. Other image scales are also possible. Image scales with the same sign and absolute values ​​in the x and y directions x, y, for example with absolute values ​​of 0.125 or 0.25, are also possible. The number of intermediate image planes in the x and y directions x, y in the beam path between the object field 5 and the image field 11 can be the same or, depending on the design of the projection optics 10, can be different.Examples of projection optics with different numbers of such intermediate images in the x and y directions x, y are known from US 2018 / 0074303 A1. Each of the second facets 23 is assigned to exactly one of the first facets 21 to form an illumination channel for illuminating the object field 5. This can result, in particular, in illumination according to Köhler's principle. The far field is divided into a multitude of object fields 5 with the help of the first facets 21. The first facets 21 generate a plurality of images of the intermediate focus onto the second facets 23 assigned to each of them. The first facets 21 are each superimposed by an assigned second facet 23 onto the reticle 7 to illuminate the object field 5. The illumination of object field 5 is particularly homogeneous. It preferably exhibits a uniformity error of less than 2%.Field uniformity can be achieved by superimposing different illumination channels. Carl Zeiss SMT GmbH 36 By arranging the second facets 23, the illumination of the entrance pupil of the projection optics 10 can be geometrically defined. By selecting the illumination channels, in particular the subset of the second facets 23 that carry light, the intensity distribution in the entrance pupil of the projection optics 10 can be adjusted. This intensity distribution is also referred to as the illumination setting or illumination pupil fill. A similarly preferred pupil uniformity in the area of ​​defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by redistributing the illumination channels. Further aspects and details of the illumination of the object field 5, and in particular the entrance pupil of the projection optics 10, are described below.The projection optics 10 may, in particular, have a homocentric entrance pupil. This pupil may be accessible or inaccessible. The entrance pupil of the projection optics 10 cannot usually be illuminated exactly by the second faceted mirror 22. When the projection optics 10 image the center of the second faceted mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, a surface can be found where the pairwise determined separation of the aperture rays is minimized. This surface represents the entrance pupil or a surface conjugate to it in real space. In particular, this surface exhibits a finite curvature. The projection optics 10 may have different positions of the entrance pupil for the tangential and sagittal beam paths.In this case, an imaging element, in particular an optical component of the transmission optics (Carl Zeiss SMT GmbH 37), should be provided between the second faceted mirror 22 and the reticle 7. This optical element allows the different positions of the tangential and sagittal entrance pupils to be taken into account. In the arrangement of the components of the illumination optics 4 shown in Fig. 1, the second faceted mirror 22 is arranged in a plane conjugate to the entrance pupil of the projection optics 10. The first faceted mirror 20 is tilted relative to the object plane 6. The first faceted mirror 20 is tilted relative to an arrangement plane defined by the deflecting mirror 19. The first faceted mirror 20 is tilted relative to an arrangement plane defined by the second faceted mirror 22. Fig. 2 shows a measuring device 100 according to a first embodiment.The measuring device 100 is arranged in the lithography system 1 of Fig. 1. The measuring device 100 serves, for example, to measure a resistance-dependent measured quantity T, e.g., a temperature T, of an optical element 102 of the lithography system 1. For this purpose, a measuring resistor 104, e.g., a temperature resistor 104, with a resistance value RT, is used, which is arranged on the optical element 102, e.g., in direct physical contact with the optical element 102. By way of example only, the measuring device 100 serves to measure a temperature T of an optical surface of the faceted mirror 20 (Fig. 1), and the measuring resistor 104 is arranged on a back side of the faceted mirror 20. The measuring device 100 includes a current source 106 for generating a measuring current I. The current source 106 is, for example, a 100-volt power supply. B. a direct current source that delivers a current I at its connection points 106a, 106b.The power source 106 comprises, for example, a power generation unit 108 and optionally a digital-to-analog converter 110. The digital-to-analog converter 110 receives a digital input voltage A (e.g., from a control unit 112 of the measuring device 100) and converts the digital input voltage A into an analog signal. This analog signal is used to control the power generation unit 108 in order to supply a measuring current I with a corresponding current intensity. The measuring device 100 also comprises a measuring line branch 114 and a reference line branch 116, which can be selectively energized with the measuring current I. In particular, a switching unit 118 is provided, with the aid of which either the measuring line branch 114 or the reference line branch 116 can be selectively energized with the measuring current I. In Fig.Figure 2 shows a reference switching position 120 of the measuring device 100, in which the switching unit 118 is switched such that the current source 106 is electrically connected to the reference line branch 116. Figures 3 and 4 each show a measuring switching position 122 of the measuring device 100, in which the switching unit 118 is switched such that the current source 106 is electrically connected to the measuring line branch 114. The measuring line branch 114 has, in particular, an electrical line 124 that electrically connects a first line point 114a with a second line point 114b of the measuring line branch 114 – interrupted only by a connection unit 126. The connection unit 126 of the measuring device 100, arranged on the measuring line branch 114, serves for the optional electrical connection of the measuring resistor 104 or at least one calibration component 128, 128', 130.The at least one calibration component 128, 128', 130 can, for example, be at least one calibration resistor 128, 128' and / or a short-circuit bridge 130. Carl Zeiss SMT GmbH 39 The measuring resistor 104, for example, has a first connection point 104a and a second connection point 104b. In addition, each of the at least one calibration component 128, 128', 130, for example, has a first connection point 128a, 128a', 130a and a second connection point 128b, 128b', 130b. The connection unit 126 is, for example, a two-pole connection unit 126 with a first connection pole 126a and a second connection pole 126b. The first line point 114a of the measuring line branch 114 is, for example, directly electrically connected via line 124 to the first terminal pole 126a of the connection unit 126.Furthermore, the second terminal 114b of the measuring line branch 114 is, for example, directly electrically connected via line 124 to the second terminal 126b of the connection unit 126. Additionally, the first terminal 126a of the connection unit 126 is suitable, for example, for electrical connection to the corresponding first terminal 104a, 128a, 128a', 130a of the measuring resistor 104 or one of the at least one calibration component 128, 128', 130. Moreover, the second terminal 126b of the connection unit 126 is suitable, for example, for electrical connection to the corresponding second terminal 104b, 128b, 128b', 130b of the measuring resistor 104 or of the at least one calibration component 128, 128', 130. For example, the connection unit 126 is detachably (e.g. by means of a plug connection) electrically connected to the measuring resistor 104 or to the at least one calibration component 128, 128', 130.For example, both the connection unit 126 and the measuring resistor 104, or the at least one calibration component 128, 128', 130, have corresponding detachable connecting elements that can be engaged with each other and electrically connected, and then disconnected again. For example, the terminals 126a, 126b of the connection unit 126 and the Carl Zeiss SMT GmbH 40 connection points 104a, 104b of the measuring resistor 104 have corresponding connecting elements. Furthermore, for example, the connection points 128a, 128b, 128a', 128b', 130a, 130b of at least one calibration component 128, 128', 130 also have corresponding connecting elements which correspond to the connecting elements of the connection poles 126a, 126b of the connection unit 126 and can be detachably connected.The measuring device 100 also includes a reference resistor 132 with a reference resistance value RR, which is arranged on the reference line branch 116. The reference numerals 132a and 132b designate, respectively, a first and second connection point of the reference resistor 132. The reference line branch 116 has, in particular, a further electrical line 134, which electrically connects a first line point 116a with a second line point 116b of the reference line branch 116 – interrupted only by the reference resistor 134. The first line point 116a of the reference line branch 116 is, for example, directly electrically connected to the first connection point 132a of the reference resistor 132. Furthermore, the second conductor point 116b of the reference conductor branch 116 is, for example, directly electrically connected to the second connection point 132b of the reference resistor 132.The reference resistor 134, with reference resistance value RR, arranged on the reference line branch 116, is energized in the reference switching position 120 and serves to perform a reference measurement. The connection unit 126, arranged on the measuring line branch 114, is energized with the measuring current I in the measuring switching position 122 (Fig. 3). The energized measuring line branch 114 is used to perform a calibration measurement when one of the at least one calibration component 128, 128', 130 is connected to the Carl Zeiss SMT GmbH 41 connection unit 126. Furthermore, the energized measuring line branch 114 is used to perform a measurement of the resistance-dependent measured quantity T (e.g., the temperature T) on the object 102 when the measuring resistor 104 is connected to the connection unit 126.The switching unit 118, with which the measuring current I is directed either into the measuring line branch 114 or the reference line branch 116, has, for example, a first and second switching element 118a, 118b. The first switching element 118a can selectively electrically contact either the first line point 114a of the measuring line branch 114 or the first line point 116a of the reference line branch 116 and thus connect the corresponding line point 114a, 116 with the first connection point 106a of the power source 106. Similarly, the second switching element 118b can selectively electrically contact either the second terminal 114b of the measuring line branch 114 or the second terminal 116b of the reference line branch 116, thus connecting the corresponding terminal 114b, 116b to the second connection point 106b of the power source 106. The switching unit 118 is specifically designed to switch the two switching elements 118a, 118b simultaneously.The control unit 112 of the measuring device 100 is also configured, for example, to control the switching unit 118 (control signal B in Fig. 2). The measuring device 100 also has a voltage sensing unit 136 for detecting a voltage UR, UM, UT. The reference numerals 136a, 136b indicate connection points of the voltage sensing unit 136. The voltage sensing unit 136 is arranged in the circuit S of the measuring device 100 such that, in the reference switching position 120 (Fig. 2), it is connected in parallel to the reference line branch 116 – and thus to the reference resistor 132. Furthermore, the voltage sensing unit 136 is arranged in circuit S Carl Zeiss SMT GmbH 42 such that it is connected in parallel to the measuring line branch 114 in the measuring switching position 122 (Fig. 3). This means that the voltage sensing unit 136 measures a reference voltage UR dropping across the reference line branch 116 in the reference switching position 120 (Fig. 2).Furthermore, in the measuring switching position 122, the voltage detection unit 136 measures a measuring voltage U dropping across the measuring line branch 114. M (Fig. 3). The voltage sensing unit 136, for example, includes an analog-to-digital converter 138. The analog-to-digital converter 138 converts the analog voltage U R , U M , U TThe voltage drop across the corresponding line branch 114, 116 is converted into a digital signal C and outputs this signal C as an output signal. The output signal C of the voltage sensing unit 136 is forwarded to the control unit 112. To determine a parasitic resistance value RP of the measuring device 100, the connection unit 126 of the measuring line branch 114 is first electrically connected to one of the at least one calibration component 128, 128', 130. For example, the connection unit 126 of the measuring line branch 114 is electrically connected to the calibration resistor 128, as shown in Fig. 3. Although not shown in all figures, each of the measuring devices 100, 200, 300 shown and described herein can have more than one calibration resistor 128, 128' and can also have more than two calibration resistors 128, 128'. These multiple calibration resistors 128, 128' each have different calibration resistance values ​​RK, RK'.Then, one of the several calibration resistors 128, 128' can be preselected and electrically connected to the connection unit 126 of the measuring line branch 114. The preselected calibration resistor 128, 128' is chosen, for example, such that a calibration resistance value RK, RK' of the preselected calibration resistor 128, 128' deviates by 30% or less, 20% or less, and / or 10% or less from a pre-estimated resistance value of the parasitic resistance. The measuring device 100 is then switched to the reference switching position 120 (Fig. 2), and a reference voltage value UR of the reference line branch 116, i.e., of the reference resistor 132, is detected and transmitted (e.g., as signal C) to the control unit 112. The measuring device 100 is then switched to the measuring switching position 122 (Fig. 3).In this measuring switch position 122, a measured voltage value UM of the measuring line branch 114 with the connected calibration resistor 128 is recorded and transmitted (e.g., as signal C) to the control unit 112. Since the same current I with the same current intensity flows through the respective line branch 114, 116 in both switching positions 120, 122, the following applies: I = UR / RR = UM / RM. Here, RR is the predetermined resistance value of the reference resistor 132. Furthermore, RM is a resistance value of the measuring line branch 114, which includes a parasitic resistance value RP. In the example of Fig. 3, in which the calibration resistor 128 is connected to the measuring line branch 114, the resistance value R results. Mof the measuring line branch 114 as the total resistance of a parallel circuit consisting of the calibration resistor 128 and the parasitic resistance. Thus, for the total resistance value RM of the measuring line branch 114, the resistance value RK of the calibration resistor 128, and the parasitic resistance value RP: Carl Zeiss SMT GmbH 44 RM = (RK ∙ RP) / RK + RP. Consequently, the voltage measurement of UR and UM, and with a known resistance value R, can first be used to determine the resistance value. R The resistance value RM of the measuring line branch 114 can be calculated from the reference resistor 132. From the calculated resistance value RM of the measuring line branch 114, the parasitic resistance value R can then be determined according to the equation above, given the known resistance value RK of the calibration resistor 128. Pthe measuring device 100 can be calculated. Although not shown in Fig. 3, the short-circuit bridge 130 can also be connected to the connection unit 126 instead of the calibration resistor 128 (or the further calibration resistor 128'). Thus, if the short-circuit bridge 130 (and no calibration resistor 128, 128') is connected to the measuring line branch 114, then the resistance value R M of the measuring line branch 114 only by the parasitic resistance value R P caused. In this case, the parasitic resistance value R can be determined by measuring the voltage of UR and UM and with a known resistance value RR of the reference resistor 132. PThe parasitic resistance of the measuring device 100 is calculated as follows: RP = RM = UM ∙ (RR / UR). After the parasitic resistance value RP of the measuring device 100 has been determined, this result can be taken into account when measuring the resistance-dependent measured quantity T (e.g., the temperature T) of the object 102. For this purpose, the connection unit 126 of the measuring line branch 114 is electrically disconnected from the corresponding calibration component 128, 128', 130 and instead electrically connected to the measuring resistor 104 (Fig. 4). The measuring device 100 remains in the measuring switching position 122 (or is switched to this position by the control unit 112, control signal B). Now, another measurement – ​​the voltage value UT of the measuring line branch 114 – is measured with the measuring resistor 104 and transmitted (e.g., as signal C) to the control unit 112. The uncalibrated resistance value R TThe resistance of the measuring resistor 104 can then be calculated as follows: RT = UT / I = UT ∙ (RR / UR). Additionally, the control unit 112 now takes into account the previously determined parametric resistance value RP. For example, the uncalibrated resistance value R is T of the measuring resistor 104 by the parasitic resistance value R P corrected. For example, the determined resistance value R T The parasitic resistance value RP is subtracted. Therefore, a calibrated resistance value RT' of the measuring resistor 104 can be calculated as follows: RT' = RT – RP. From the calibrated resistance value R TThe control unit 112 then determines a measured quantity T (e.g., a temperature T) from the measuring resistor 104 by applying a pre-stored resistance-measured quantity characteristic curve. Figure 5 shows a measuring device 200 according to a second embodiment. In the following, only the differences from the measuring device 100 according to the first embodiment (Figures 2 to 4) are described. The measuring device 200 according to the second embodiment differs from the measuring device 100 according to the first embodiment, in particular by a switching device 240, which includes a further switching unit 242. The switching device 240 of the measuring device 200 enables automatic electrical connection of either a measuring resistor 204 or at least a calibration component 228, 228', 230 to a connection unit 226 of the measuring device 200.A control unit 212 of the measuring device 200 is configured to control the switching device 240, in particular the further switching unit 242, accordingly (control signal D in Fig. 5). The measuring resistor 204 in Fig. 5 is designed similarly to the measuring resistor 104 described in connection with Figures 2 to 4. The at least one calibration component 228, 228', 230 in Fig. 5 is also designed similarly to the at least one calibration component 228, 228', 230 described in connection with Figures 2 to 4. In addition, the connection unit 226 – apart from the fact that the switching device 240 is electrically connected to it – is also designed similarly to the connection unit 126 described in connection with Figures 2 to 4. The control unit 212 in Fig.Figure 5 differs from the control unit 112 described in connection with Figures 2 to 4 only in that it is configured to control the switching device 240, in particular the further switching unit 242, in addition to the functions of the control unit 112. Each of the measuring resistor 204 and the at least one calibration component 228, 228', 230 has a first electrical connection point 204a, 228a, 228a', 230a and a second electrical connection point 204b, 228b, 228b', 230b, at which the respective component is electrically connected to a corresponding first line 244a, 246a, 248a, 250a and a corresponding second line 244b, 246b, 248b, 250b of the switching device 240. As shown in Figure 5. As can be seen, the switching device 240 is electrically connected to the connection unit 226 of the measuring device 200.In particular, the switching device 240 has a further connection unit 252, which is electrically connected to the Carl Zeiss SMT GmbH connection unit 226. For example, the further connection unit 252 has a first terminal 252a and a second terminal 252b, which are electrically connected to a first terminal 226a and a second terminal 226b of the connection unit 226. The further switching unit 242 also has a switching element 254, which can be electrically connected either to the first line 244a (and thus to the measuring resistor 204), to the second line 246a (and thus to the calibration resistor 228), to the third line 248a (and thus to the further calibration resistor 228') or to the fourth line 250a (and thus to the short-circuit bridge 230). In the example of Fig.5, the switching element 254 is electrically connected to the first line 244a and thus to the measuring resistor 204.As shown by way of example in Fig. 5 for the measuring device 200 with dashed lines, each of the measuring devices 100, 200, 300 described herein can optionally have one or more circuit boards 256, 258. For example, the measuring device 200 in Fig. 5 (or also the measuring device 100 in Figures 2 to 4 and / or the measuring device 300 in Fig. 6) has a first circuit board 256. On the first circuit board 256, for example, the current source 106, the voltage sensing unit 136, the switching unit 118, the reference line branch 116 and the reference resistor 132 are arranged. Optionally, the control unit 212 (e.g., also the control unit 112, 312) can also be arranged on the first circuit board 256. For example, the measuring device 200 in Fig. 5 (or also the measuring device 100 in Figures 2 to 4 and / or the measuring device 300 in Fig. 6) has a second circuit board 258.The second circuit board 258, for example, houses the Carl Zeiss SMT GmbH 48 connection unit 226 (e.g., also the connection unit 126, 326, 326'). Optionally, the second circuit board 258 can also house, for example, the measuring resistor 104, 204 and at least one calibration component 128, 128', 130, 228, 228', 230. If a switching device 240 with a further switching unit 242 is provided, the switching device 240 can also be located on the second circuit board 258. The measuring line branch 214, for example, is only partially located on the first circuit board 256 (first section 262 of the measuring line branch 214 in Fig. 5). The measuring line branch 214 extends in particular from the first line point 214a of the measuring line branch 214 to the first connection pole 226a of the connection unit 226 and from the second connection pole 226b of the connection unit 226 to the second line point 214b of the measuring line branch 214.If a second circuit board 258 is provided, then the measuring line branch 214 can, for example, be arranged partly on the first circuit board 256 and partly on the second circuit board 258, as shown in Fig. 5. For example, a first section 262 of the measuring line branch 214 is arranged on the first circuit board 256, a second section 264 of the measuring line branch 214 is arranged between the first and second circuit boards 256, 258 (i.e., neither on the first circuit board 256 nor on the second circuit board 258), and a third section 262 of the measuring line branch 214 is arranged on the second circuit board 258, as shown in Fig. 5. In this case, the first conductor section 262 of the measuring conductor branch 214 can be designed as a conductor track, the second conductor section 264 of the measuring conductor branch 214 as an electrical cable, and the third conductor section 266 of the measuring conductor branch 214 as a conductor track.The first circuit board 256 can further comprise an interface unit 260 (e.g., connection terminals 260a, 260b) for electrically connecting the first section 262 of the measuring line branch 214 to at least the second line section 264 of the measuring line branch 214. Although not shown in the figures, the second circuit board 258 can also comprise a further interface unit (e.g., with two connection terminals) for electrically connecting the second section 264 of the measuring line branch 214 to the third line section 266 of the measuring line branch 214. Figure 6 shows a measuring device 300 according to a third embodiment. Only differences from the first embodiment are described below.The measuring device 300 according to the third embodiment differs from the measuring device 100 according to the first embodiment (Figures 2 to 4) in that the measuring device 300 has several measuring line branches 314, 314'. Each of the several measuring line branches 314, 314' is configured like the measuring line branch 114 in Figures 2 to 4 (or like the measuring line branch 214 in Figure 5). This means, in particular, that a connection unit 326, 326' for the optional electrical connection of a measuring resistor 104 or at least one calibration component 128, 128', 130 (Figure 2) is arranged on each of the several measuring line branches 314, 314'. Each of the connection units 326, 326' has a first and second connection pole 326a, 236b, 326a', 326b'. Furthermore, a switching unit 318 similar to the switching unit 118 in Fig. 2 is provided, but with more than two switching positions. In the example of Fig.The switching unit 318 has three different switching positions. In particular, the switching unit 318 is configured to selectively connect the power source 106 in a reference switching position 320 to the reference line branch 116 or in several measuring switching positions (not shown in Fig. 6) to the several measuring line branches 314, 314'. Specifically, a first switching element 318a can selectively electrically contact a first line point 116a, 314a, 314a'. Furthermore, a second switching element 318b can selectively electrically contact a second line point 116b, 314b, 314b'. The control unit 312 is configured to control the switching unit 318, 318a, 318b (control signal E in Fig. 6). Furthermore, the voltage detection unit 136 is provided for detecting a voltage UR, UM, UT (Figures 2 to 4).Depending on the switching position of the switching unit 318, the voltage sensing unit 136 can selectively measure a voltage either at the reference line branch 116 or at any of the several measuring line branches 314, 314'. A control unit 312 of the measuring device 300 is designed similarly to the control unit 112 of the measuring device 100 in Fig. 2, wherein, in addition to the functions of the control unit 112, it can determine a parasitic resistance value RP1, RP2 of the measuring device 300 for each of the several measuring line branches 314, 314'. For example, the control unit 312 can determine a first parasitic resistance value RP1 based on the detected reference voltage UR and a measured voltage detected for the first measuring line branch 314. Furthermore, the control unit 312 can, for example, determine a second parasitic resistance value RP2 based on the detected reference voltage UR and a measured voltage detected for the second measuring line branch 318'.Since a corresponding measuring resistor 104 (Fig. 4) can be connected to each measuring line branch 318, 318', several objects 102 can be measured by using multiple measuring line branches 318, 318', e.g., the temperature T of several objects 102 can be measured. Carl Zeiss SMT GmbH 51 Although two different measuring line branches 314, 314' are shown as examples in Fig. 6, more than two measuring line branches 314, 314' can also be provided. In the following, a method for calibrating a measuring device 100, 200, 300 of a lithography system 1 is described with reference to Fig. 7. The measuring device 100, 200, 300 is designed to measure a resistance-dependent measurand T in or on an optical system 102 of the lithography system 1. The measuring device 100, 200, 300 is, in particular, a measuring device 100, 200, 300 as described above in connection with Figures 2 to 6.In a first step S1 of the procedure, a measuring current I is generated (Fig. 2). In a second step S2 of the procedure, a reference line branch 116 of the measuring device 100, 200, 300 is energized with the measuring current I, wherein the reference line branch 116 has a reference resistance 132. Furthermore, a reference voltage UR is detected across the reference line branch 116 when the reference line branch 116 is energized (Fig. 2). In a third step S3 of the procedure, a measuring line branch 114, 214, 314, 314' of the measuring device 100, 200, 300 is energized with the measuring current I (Fig. 3). The measuring line branch 114, 214, 314, 314' has a connection unit 126, 226, 326, 326' which is electrically connected to a calibration component 128, 128', 130, 228, 228', 230 and can alternatively be electrically connected to a measuring resistor 104, 204.In addition, a measuring voltage UM is recorded on the measuring line branch 114, 214, 314, 314' when the measuring line branch 114, 214, 314, 314' is energized. Carl Zeiss SMT GmbH 52 In a fourth step S4 of the procedure, a parasitic resistance value RP, RP1, RP2 of the measuring device 100, 200, 300 is determined based on the measured reference voltage UR and the measured measuring voltage UM. In an optional fifth step S5 of the procedure, the electrically conductive connection between the connection unit 126, 226, 326, 326' of the measuring line branch 114, 214, 314, 314' and the calibration component 128, 128', 130, 228, 228', 230 is disconnected. In an optional sixth step S6 of the procedure, the connection unit 126, 226, 326, 326' is electrically connected to the measuring resistor 104, 204 (Fig. 4). In the case of a measuring device 200 with a switching device 240 with a further switching unit 242 (Fig. 5) steps S5 and S6 can be carried out fully automatically.In an optional seventh step S7 of the procedure, the measuring line branch 114, 214, 314, 314' – and thus the measuring resistor 104, 204 – is energized with the measuring current I (Fig. 4). In an optional eighth step S8 of the procedure, a further measuring voltage UT is detected at the measuring line branch 114, 214, 314, 314' when the measuring line branch 114, 214, 314, 314' is energized (Fig. 4). In an optional ninth step S9 of the procedure, the resistance-dependent measured quantity T is calculated based on the detected reference voltage UR of the reference resistor 132, the detected further measuring voltage UT at the measuring line branch 114, 214, 314, 314', and the determined parasitic resistance value RP, RP1, RP2 of the measuring device 100, 200, 300. Carl Zeiss SMT GmbH 53 Consequently, the resistance-dependent measured quantity T of the object 102, e.g., a temperature T of an optical element 102 of the lithography system 1, can be determined even more accurately and without great effort.Although the present invention has been described using exemplary embodiments, it can be modified in many ways.

[0002] Carl Zeiss SMT GmbH 54 REFERENCE SYMBOL LIST 1 Projection exposure system 2 Lighting system 3 Light source 4 Lighting optics 5 Object field 6 Object plane 7 Retikel 8 Reticle holder9 Reticle displacement drive10 Projection optics11 Image field12 Image plane 13 Wafer14 Wafer holder 15 Wafer transfer drive 16 Illumination beam 17 Collector 18 Intermediate focus plane 19 Deflection mirror 20 First facet mirror 21 First facet 22 Second facet mirror 23 Second facet 100 Measuring device 102 Measured object 104 Measuring resistor 104a Connecting element 104b Connecting element Carl Zeiss SMT GmbH 55106 Power source 106a Connection point 106b Connection point 108 Power generation unit 110 Digital-to-analog converter 112 Control unit 114 Measuring line branch 114a Line point 114b Line point 116 Reference line branch 116a Line point 116b Line point 118 Switching unit 118a Switching element 118b Switching element 120 Reference switching position 122 Measuring switching position 124 Line 126 Connection unit 126a Connecting element 126b Connecting element 128 Calibration component 128a Connection point 128b Connection point 128' Calibration component 128a' Connection point 128b' Connection point 130 Calibration component 130a Connection point 130b Connection point Carl Zeiss SMT GmbH 56132 Reference resistor 132a Connection point 132bConnection point 134 Cable 136 Voltage sensing unit 136a Connection point 136b Connection point 138 Analog-to-digital converter 200 Measuring devices 204 Measuring resistor 204a Connection point 204b Connection point 212 Control unit 214 Measuring cable branch 214a Cable point 214b Cable point 226 Connection unit 226a Connection pole 226b Connection pole 228 Calibration component 228a Connection point 228b Connection point 228' Calibration component 228a' Connection point 228b' Connection point 230 Calibration component 230a Connection point 230b Connection point 240 Switching device 242 Switching unit Carl Zeiss SMT GmbH 57244 Cable 244a Cable 244b Cable 246 Cable 246a Cable 246b Cable 248 Cable 248a Cable 248b Cable 250a Cable 250b Cable 252 Connection unit 252a Connection pole 252b Line point 254 Switching element 256 Circuit board 258 Circuit board 260 Interface unit 260a Connection pole 260b Connection pole 262 Section 264 Section 266 Line section 300 Measuring device 312 Control unit 314 Measuring line branch 314a Line point 314bLine point 314' Measuring line branch 314a' Line point Carl Zeiss SMT GmbH 58 314b' Line point 318 Switching unit 318a Switching element 318b Switching element 320 Reference switching position 326 Connection unit 326a Connection pole 326b Connection pole 326' Connection unit 326a' Connection pole 326b' Connection pole A Signal B Signal C Signal D Signal E Signal I Strom M1-M6 Mirror RK Resistance value RK' Resistance value R M Resistance value RP Resistance value RP1 Resistance value R P2 Resistance value RR Resistance value RT, RT' Resistance value S Circuit S1-S9 Process steps T Temperature Carl Zeiss SMT GmbH 59 UR Voltage UM Voltage UT Voltage

Claims

Carl Zeiss SMT GmbH 60 PATENT CLAIMS1. Measuring device (100) for measuring a resistance-dependent measured quantity (T) on or in an optical system (10) of a lithography system (1), comprising: a current source (106) for generating a measuring current (I), a measuring line branch (114) and a reference line branch (116), a switching unit (118) for selectively connecting the current source (106) in a reference switching position (120) to the reference line branch (116) or in a measuring switching position (122) to the measuring line branch (114), a connection unit (126) arranged on the measuring line branch (114) for selectively electrically connecting a measuring resistor (104) or at least a calibration component (128, 130), a reference resistor (132) arranged on the reference line branch (116), a Voltage sensing unit (136) for sensing a voltage (UR,UM) optionally on the reference line branch (116) or the measuring line branch (114),and a control unit (112) for determining a parasitic resistance value (RP) of the measuring device (100) based on a reference voltage (UR) detected in the reference switching position (120) and a measuring voltage (UM) detected in the measuring switching position (122) in which one of the at least one calibration component (128, 130) is connected to the connection unit (126).

2. Measuring device according to claim 1, wherein the at least one calibration component (128, 130) comprises at least one calibration resistor (128), and the control unit (112) is configured to determine the parasitic resistance value (RP) based on the detected reference voltage (UR) of the reference resistor (132), a predetermined reference resistance value (RR) of the, Carl Zeiss SMT GmbH 61 reference resistance (132), which in the measuring switching position (122), in which at least one calibration resistor (128) is connected to the connection unit (126), measured voltage (UM) and a predetermined calibration resistance value (RK) of one calibration resistor (128).

3. Measuring device according to claim 1 or 2, wherein the at least one calibration component (128, 130) has a short-circuit bridge (130), and the control unit (112) is configured to determine the parasitic resistance value (RP) based on the measured reference voltage (UR) of the reference resistor (132), a predetermined reference resistance value (R). R ) of the reference resistor (132), and the measured voltage (U) detected in the measuring switch position (122) in which the short-circuit bridge (130) is connected to the connection unit (126). M) to determine.

4. Measuring device according to one of claims 1 to 3, wherein the control unit (112) is configured to determine the resistance-dependent measured quantity (T) based on a reference voltage (UR) of the reference resistor (132) detected in the reference switching position (120), a further measured voltage (UT) detected in the measuring switching position (122) in which the measuring resistor (104) is connected to the connection unit (126) of the measuring line branch (114), and the determined parasitic resistance value (RP) of the measuring device (100).5.Measuring device according to one of claims 1 to 4, wherein the connection unit (126) has one or more connecting elements (126a, 126b) for detachable electrical connection optionally with one or more first corresponding connecting elements (104a, 104b) of the measuring resistor (104) or one or more second corresponding connecting elements (128a, 128b, 130a, 130b) of the at least one calibration component (128, 130). Carl Zeiss SMT GmbH 626. Measuring device according to one of claims 1 to 5, comprising the measuring resistor (204), the at least one calibration component (228, 230) and a further switching unit (242), which is electrically conductively connected to the connection unit (226), wherein the further switching unit (242) is configured to selectively connect either the measuring resistor (204) or the at least one calibration component (228, 230) electrically to the connection unit (226).7.Measuring device according to one of claims 1 to 6, comprising the measuring resistor (204), at least one first calibration component (228) in the form of at least one calibration resistor (228), a second calibration component (230) in the form of a short-circuit bridge (230) and a further switching unit (242) which is electrically connected to the connection unit (226), wherein the further switching unit (242) is configured to selectively connect either the measuring resistor (204), the at least one calibration resistor (228) or the short-circuit bridge (230) electrically to the connection unit (226).Measuring device according to one of claims 1 to 7, wherein the at least one calibration component (128, 128', 130) has several calibration resistors (128, 128') with different calibration resistance values ​​(RK, RK'), the connection unit (126) of the measuring line branch (114) is electrically connected in the measuring switching position (122) to a calibration resistor (128) preselected from the several calibration resistors (128, 128'), and the preselected calibration resistor (128) is selected such that a calibration resistance value (RK) of the preselected calibration resistor (128) deviates by 30% or less, 20% or less and / or 10% or less from a preestimated resistance value of the parasitic resistance (RP). Measuring device according to one of claims 1 to 8, wherein the current source (106) has a digital-to-analog converter (110) for generating a variable measuring current (I), and / or the voltage sensing unit (136) has an analog-to-digital converter (110).Carl Zeiss SMT GmbH 63 Digital converter (138) for converting a detected analog voltage value (UR, UM, UT) into a digital voltage signal (C).

10. Measuring device according to one of claims 1 to 9, wherein the reference line branch (116) is shorter than the measuring line branch (114), and / or the reference line branch (116) is shorter than the measuring line branch (114) by a factor of 2 or more, a factor of 5 or more, a factor of 10 or more, a factor of 100 or more.

11. Measuring device according to one of claims 1 to 10, further comprising several of the measuring line branch (314, 314'), wherein a connection unit (326, 326') for selectively connecting a measuring resistor (104) or at least a calibration component (128, 130) is arranged on each measuring line branch (314, 314'),the switching unit (318) is configured for selectively connecting the current source (106) in the reference switching position (120) to the reference line branch (116) or in several measuring switching positions (122) accordingly to the several measuring line branches (314, 314'), the voltage detection unit (136) is configured for selectively detecting a voltage (UR, UM) either on the reference line branch (116) or on the several measuring line branches (314, 314'), and the control unit (112) is configured for determining a respective parasitic resistance value (RP1, RP2) of the measuring device (100) for each measuring line branch (314, 314') based on the detected reference voltage (UR) and the corresponding of the several detected measuring voltages (U, UM). M ) is set up on the several measuring line branches (314, 314').

12. Measuring device according to one of claims 1 to 11, further comprising a circuit board (256) on which the current source (106), the voltage sensing unit Carl Zeiss SMT GmbH 64(136), the switching unit (118), the reference line branch (116) and the reference resistor (132) are arranged.

13. Lithography system (1) with a measuring device (100) according to one of claims 1 to 12 and an optical system (10), wherein the measuring resistor (104) of the measuring device (100) is arranged on or in the optical system (10).

14. Method for calibrating a measuring device (100) of a lithography system (1), in particular a measuring device (100) according to any one of claims 1 to 12, wherein the measuring device (100) is set up for measuring a resistance-dependent measured quantity (T) in or on an optical system (10) of the lithography system (1), comprising the steps: a) generating (S1) a measuring current (I), b) successively energizing (S2, S3) a reference line branch (116) and a measuring line branch (114) of the measuring device (100) with the measuring current (I), wherein the reference line branch (116) has a reference resistor (132),and the measuring line branch (114) has a connection unit (126) which is electrically connected to a calibration component (128, 130) and alternatively can be electrically connected to a measuring resistor (104), c) detecting (S2) a reference voltage (UR) at the reference line branch (116) when the reference line branch (116) is energized, and detecting (S3) a measuring voltage (UM) at the measuring line branch (114) when the measuring line branch (114) is energized, and d) determining (S4) a parasitic resistance value (RP) of the measuring device (100) based on the detected reference voltage (U, R ) and the measured voltage (UM).

15. Method according to claim 14, comprising step d):Disconnecting (S5) the electrically conductive connection between the terminal unit (126) of the measuring line branch (114) and the calibration component (128, 130), Carl Zeiss SMT GmbH 65 electrically conductive connection (S6) of the connection unit (126) with the measuring resistor (104), energizing (S7) the measuring line branch (114) with the measuring current (I), detecting (S8) a further measuring voltage (U) T ) on the measuring line branch (114) when the measuring line branch (114) is energized, and determining (S9) the resistance-dependent measured quantity (T) based on the detected reference voltage (UR) of the reference resistor (132), the detected further measuring voltage (UT) on the measuring line branch (114) and the determined parasitic resistance value (RP) of the measuring device (100).

Images