MEASURING DEVICE, LITHOGRAPHING FACILITY AND METHOD FOR CALIBRATING A MEASURING DEVICE

Abstract

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 power source in a reference switching position (120) to the reference line branch or in a measuring switching position (122) to the measuring line branch, a connection unit (126) arranged on the measuring line branch for optionally connecting a measuring resistor (104) or at least one calibration component (128, 130) electrically, a reference resistor (132) arranged on the reference line branch, a voltage sensing unit (136) for sensing a voltage (U R , U M) optionally on the reference line branch or the measuring line branch, and a control unit (112) for determining a parasitic resistance value (R) P ) the measuring device based on a reference voltage (U) detected in the reference switching position (120). R ) and a measured voltage (U) 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). M ).

Description

[0001] The present invention relates to a measuring device for measuring a resistance-dependent measured quantity 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.

[0002] Microlithography is used to manufacture microstructured components, such as integrated circuits. The microlithography process is carried out using a lithography system, which includes 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, such as a silicon wafer, coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection system. This transfers the mask structure onto the photosensitive coating of the substrate.

[0003] Driven by the pursuit of ever smaller structures in the fabrication 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 the refracting optics, i.e., lenses, used previously.

[0004] Temperature sensors can be used in various areas of lithography systems. For example, such temperature sensors serve to quantify thermal deformations of mirrors caused by the absorption of radiation emitted by the EUV light source. These optical deformations of the mirror can impair the image produced by the projection lens. To counteract thermal deformations, highly precise temperature measurement with an absolute accuracy better than 50 mK, or even better than 5 mK, is required.

[0005] 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. To enable highly precise temperature measurement and reduce errors, EP 0 120 102 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.

[0006] Against this background, one object of the present invention is to improve the measurement of a resistance-dependent quantity on or in an optical system of a lithography system.

[0007] According to a first aspect, a measuring device for measuring a resistance-dependent quantity on or in an optical system of a lithography system is proposed. The measuring device comprises: a power source for generating a measuring current, a measuring line branch and a reference line branch, a switching unit for optionally connecting the power source in a reference switching position to the reference line branch or in a measuring switching position to the measuring line branch, 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 sensing 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 measuring voltage detected in the measuring switching position in which one of the at least one calibration component is connected to the connection unit.

[0008] By determining the parasitic resistance value of the measuring device, measurement errors when measuring the resistance-dependent quantity can be taken into account. This allows for more accurate measurement of the resistance-dependent quantity (e.g., temperature).

[0009] For example, components of the measuring device integrated into the measurement path can lead to measurement errors. Even the smallest 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 lead to measurement errors. The proposed measuring device allows such leakage resistances (i.e., leakage currents) and line resistances to be determined and taken into account in a subsequent measurement of the resistance-dependent quantity (e.g., temperature).

[0010] Because the proposed measuring device also uses components for measuring the resistance-dependent quantity (e.g., the reference resistor, the reference line branch, and the measuring line branch) to determine the parasitic resistance value, the device can be manufactured more easily. Furthermore, calibration of the measuring device—that is, determination of its parasitic resistance value—can be performed regularly and at short intervals between measurements of the resistance-dependent quantity during operation. This continuous recalibration thus enables more accurate measurements, especially in systems with dynamically changing environmental conditions.

[0011] 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 quantity. This means that during the calibration process, the same current transmission path (e.g., the same conductor tracks and / or cables) is evaluated and calibrated up to the connection unit as is 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 during the subsequent measurement process.

[0012] 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. DUV stands for "deep ultraviolet" and refers to a wavelength of the working light between 30 nm and 250 nm.

[0013] The EUV or DUV lithography system comprises an illumination system and a projection system. Specifically, the EUV or DUV lithography system projects the image of a mask (reticule) illuminated by the illumination system onto a substrate, such as 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.

[0014] 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.

[0015] The optical system can include an optical element (for example, a mirror or a lens), a sensor and / or an actuator.

[0016] The measuring device can be used to measure a resistance-dependent quantity (e.g., temperature) in any part of the lithography system. Using the measuring device, a resistance-dependent quantity is measured, for example, at a test object within the lithography system. The test object is, for example, an optical element (such as a mirror or lens), an actuator, or the like. For instance, the measuring resistor is positioned in physical contact with the test object (e.g., optical element) for measurement purposes.

[0017] 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, particularly for determining the aging of lithography equipment.

[0018] 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 they enable the use of high-precision optics.

[0019] The current source is, for example, a direct current source. Alternatively, the current source can also be an alternating current source, which, for example, provides a square wave or a sine wave. The current source is also, for example, a modulating current source, which can generate a measurement current with a variable current intensity. Just as an example, the current source includes a digital-to-analog converter, so that an output measurement current can be varied with an analog voltage signal from the digital-to-analog converter.

[0020] A measuring resistor is an electrical resistor whose resistance changes depending on a resistance-dependent measured quantity. By determining the electrical resistance of the measuring resistor, the measured quantity can be derived from the determined resistance value. Here, the term "measuring resistor" refers to a component (i.e., a measuring resistor element), and not to an abstract resistance in the sense of a resistance value.

[0021] 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 across it. Thus, the temperature across the temperature resistor can be derived from its electrical resistance value.

[0022] A reference resistor is also an electrical resistor. Specifically, a reference resistor is a high-precision resistor whose resistance value is known as accurately as possible. For example, a reference resistor has a very low absolute tolerance and is highly resistant to aging. A reference resistor can also be temperature-independent.

[0023] The reference resistor is, in particular, an electrical resistor with a predetermined reference resistance value.

[0024] The measuring resistor and the reference resistor can be identical. Alternatively, the reference resistor can be, 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.

[0025] The measuring resistor can be located on or within the optical system (e.g., in physical contact with a device within the optical system) to detect the measured quantity (e.g., temperature). The measuring resistor is primarily used to detect the measured quantity of the device (e.g., an optical element, a mirror, a lens, an actuator, or the like). In contrast, the reference resistor can be positioned at a distance and / or a distance from the device being measured.

[0026] 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.

[0027] The at least one calibration component includes, for example, at least one calibration resistor and / or a short-circuit bridge. A calibration resistor is an electrical resistor. Specifically, each calibration resistor is an electrical resistor with a predetermined calibration resistance value.

[0028] 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. This means 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 it.

[0029] The connection unit has, in particular, at least one electrical connection element for optional 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 thus designed such that it can be electrically connected to each of the at least one further electrical connection element.

[0030] The fact that the measuring resistor and / or the calibration component are provided electrically disconnected from the connection unit includes situations where the measuring resistor and / or the calibration component are provided physically completely disconnected from the connection unit and can, for example, be electrically connected to the connection unit manually. It also includes a case where the measuring resistor and the calibration component are provided in a switchable (i.e., electrically connectable) manner via another switching unit.

[0031] The measuring device includes, in particular, for example, the measuring resistor and the calibration component.

[0032] The measuring line branch and the reference line branch are each, in particular, electrical lines. An electrical line comprises, for example, an electrical cable, a stranded wire, and / or a conductive trace (e.g., on a printed circuit board). The reference line branch is preferably configured as a conductive trace (e.g., on a printed circuit board). The measuring line branch preferably has a first conductor section configured as a conductive trace (e.g., on the printed circuit board) and a second conductor section configured as an electrical cable and / or stranded wire. The measuring line branch may also have a third conductor section configured as a conductive trace on a further 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 located closer to the connection unit than the first section of the measuring line branch.

[0033] The measuring device includes, in particular, a circuit in which the current source, the voltage detection unit, the switching unit and optionally the measuring line branch or the reference line branch are electrically connected.

[0034] The fact that the connection unit is arranged on the measuring line branch means in particular that the connection unit is arranged in an electrically conductive manner within the measuring line branch and is electrically connected to the measuring line branch.

[0035] The fact that the reference resistor is arranged on the reference line branch means, in particular, that the reference resistor is arranged in an electrically conductive manner within the reference line branch and is electrically connected to the reference line branch.

[0036] The switching unit allows either the measuring branch or the reference branch to be electrically connected to the power source, so that either the measuring branch or the reference branch is energized with the measuring current. This means that the measuring branch and the reference branch are energized individually and sequentially (e.g., alternately).

[0037] 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 conductor 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 conductor point of the measuring line branch or the reference line branch. The switching unit is specifically designed to switch both switching elements simultaneously.

[0038] The switching unit is, in particular, a controllable circuit. The switching unit includes, for example, a multiplexer. For instance, the switching unit, e.g., each of its switching elements, has two distinct switching states. For example, the first switching element has one input port connected to the power source and two output ports. For example, the second switching element has one output port connected to the power source and two input ports.

[0039] The voltage detection unit is 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.

[0040] This means that the switching unit allows the measuring device to be switched between a reference switching position and a measuring switching position. 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 the voltage drop across the reference branch (reference voltage, e.g., the voltage drop across the reference resistor).

[0041] In the measuring position, the measuring line branch with the connection unit is energized with the measuring current. If the connection unit is electrically connected to the measuring resistor, the measuring resistor is energized in the measuring position. If the connection unit is electrically connected to one of the at least one calibration component, this calibration component is energized in the measuring position. Furthermore, in the measuring position, the voltage sensing unit is connected in parallel to the measuring line branch. This means that the voltage sensing unit measures the voltage drop across the measuring line branch in the measuring position.

[0042] 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., with the same current value. Specifically, the measuring current is generated (i.e., switched on) at a certain current intensity, and then the energizing of the reference line branch and the measuring line branch is switched without changing the measuring current.

[0043] 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 U is applied. R of the reference line branch, i.e., the reference resistance, is determined. The measuring device is then switched to the measuring position and a measured voltage value U is applied. Mof 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.

[0044] This is R R the predetermined resistance value of the reference resistor. Furthermore, R M a resistance value of the measuring line branch, which has a parasitic resistance value R P includes. Consequently, the voltage measurement of U can be used. R and U M and with a known resistance value R R of the reference resistor, the resistance value R M of the measuring line branch are calculated: RM=(UM / UR)⋅RR.

[0045] In the case that the calibration component is a short-circuit bridge, R M as parasitic resistance value R PThe resistance of the measuring device (especially as the line resistance of the measuring line branch) is determined. In the case of the short-circuit bridge, the parasitic effect on the signal path (line resistance) is measured. From a circuit perspective, the line resistance can be described by a series circuit.

[0046] In the case that the calibration component is a calibration resistor, R becomes M taking into account a predetermined resistance value R K of the calibration resistor a parasitic resistance value R P The measuring device (especially as the leakage resistance of the measuring line branch) is determined. The calibration resistor is thus used to check whether leakage currents flow in parallel to the measuring circuit. From a circuit perspective, this can be described as a parallel connection of parasitic resistance R. P and calibration resistor R K This allows us to discuss the relationship that applies to parallel circuits. RM=(RK⋅RP) / (RK+RP) can be applied. Thus, the parasitic resistance value R can be determined. P the measuring device from the predetermined resistance value R K of the calibration resistor and the determined resistance value R M of the measuring line branch.

[0047] The parasitic resistance value of the measuring device therefore includes, for example, a leakage resistance and / or a line resistance of the measuring device.

[0048] 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 or reference line connected to the power source.

[0049] 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., a computer or a processor, or as part of a system, e.g., a computer system. If the control unit is implemented as software, it can be designed as a computer program product, a function, program code, or an executable object.

[0050] The control unit is primarily used to evaluate the voltage values ​​acquired by the voltage sensing unit in order to determine the parasitic resistance 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.

[0051] 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 sensing unit. T detected at the measuring line branch. For example, the control unit then calculates based on the voltage value U. T- e.g., taking into account a reference resistance value previously recorded in the reference switching position and / or the pre-determined parasitic resistance - the resistance value across the measuring resistor. 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.

[0052] In embodiments, the control unit is configured to control the switching unit, so that the switching unit selectively connects the power source to the measuring line branch or the reference line branch.

[0053] 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 switch position in which one of the at least one calibration resistor is connected to the connection unit, and a predetermined calibration resistance value of the one calibration resistor.

[0054] For the resistance value R M The following relationship applies to the measuring line branch, based on a parallel circuit consisting of the calibration resistor and a parasitic resistor: RM=(RK⋅RP) / (RK+RP).

[0055] This allows the parasitic resistance value R to be determined. P the measuring device from the previously known calibration resistance value RK and the determined resistance value R M of the measuring line branch.

[0056] 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.

[0057] In the case that the calibration component is a short-circuit bridge, the parasitic resistance value R will be P the measuring device (in particular as the line resistance of the measuring line branch) directly as the resistance value R M of the measuring line branch determined: RP=RM=UM⋅(RR / UR)

[0058] According 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.

[0059] After the parasitic resistance value R P The result determined by the measuring device can be taken into account when measuring the resistance-dependent measured quantity (e.g., a temperature).

[0060] For this purpose, after determining the parasitic resistance value by applying the reference switching position and the measuring switching position with 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. Then, the measuring device is 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 U is determined. T The resistance of the measuring line branch is determined using the measuring resistor. The uncalibrated resistance value R T The measuring resistance can then be calculated as follows: RT=UT / I=UT⋅(RR / UR).

[0061] The same measuring current I is applied in the measuring switch position as in the previously executed reference switch position. To obtain a more precise resistance value R T To determine this, the control unit takes into account, in addition to the voltage U dropping across the measuring resistor. T furthermore, the voltage U across the reference resistor R By taking into account the voltage drop U across the reference resistor R when calculating the resistance value R T , error entries will be made that affect both measurements U R and U T These errors are affected, but not eliminated (ratiometric principle). Such error entries particularly affect the offset and the gain error. The resistance value R T This allows for more accurate calculations.

[0062] Additionally, the control unit now takes into account the previously determined parasitic resistance value R. PFor example, the determined uncalibrated resistance value R T to determine the parasitic resistance value R P corrected. For example, the determined resistance value R T the parasitic resistance value R P subtracted. This allows the resistance value R to be determined. T can be calculated even more precisely.

[0063] From the resistance value R calibrated in this way T The control unit then determines a measured quantity (e.g., a temperature) by applying a pre-stored resistance-measurement characteristic curve.

[0064] 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 one or more second corresponding connecting elements of the at least one calibration component.

[0065] This allows the measuring resistor to be electrically connected to and disconnected from the connection unit. Additionally, at least one 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.

[0066] A detachable electrical connection is, in particular, an electrical connection that can be detached without damage. A detachable electrical connection is, in particular, repeatedly detachable and re-connectable.

[0067] For illustrative purposes only, the detachable electrical connection features a plug connection. For example, one or more connecting elements of the connection unit are one or more connecting 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 connecting elements of the measuring resistor or the calibration component are each, for example, one or more connecting elements of a plug connection, i.e., one or more plug elements or one or more sockets for receiving a corresponding plug element.

[0068] According to a further embodiment, the measuring device comprises the measuring resistor, the 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.

[0069] The additional switching unit is, in particular, a controllable circuit. For example, the control unit is configured to control the additional switching unit such that, in a first switching state of the additional switching unit, the measuring resistor is electrically connected to the connection unit; in a second switching state of the additional switching unit, one of the at least one calibration component is electrically connected to the connection unit; in a third switching state of the additional switching unit, another of the at least one calibration component is electrically connected to the connection unit, and so on.

[0070] This means that, with the help of the additional 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 additional 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.

[0071] The additional switching unit has, in particular, an electrical input port that 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 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.

[0072] In embodiments, the control unit is configured to control the further switching unit, so that the further switching unit optionally connects the measuring resistor or the at least one calibration component electrically to the connection unit.

[0073] 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 selectively connect the measuring resistor, the at least one calibration resistor or the short-circuit bridge electrically to the connection unit.

[0074] According to a further embodiment, the at least one calibration component has several calibration resistors with different calibration resistance values. Furthermore, the connection unit of the measuring line branch is electrically connected in the measuring switching position to a calibration resistor preselected from among the several calibration resistors. The preselected calibration resistor is also selected 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.

[0075] By selecting a calibration resistor whose calibration resistance value differs only slightly from the resistance value of the parasitic resistance, the parasitic resistance value can be determined even more accurately.

[0076] According to another embodiment, the current source has a digital-to-analog converter for generating a variable measuring current, and / or the voltage sensing unit has an analog-to-digital converter for converting a detected analog voltage value into a digital voltage signal.

[0077] The digital-to-analog converter receives a digital input voltage and converts it into an analog signal. This analog signal is then used to control a current-generating unit in the power source to deliver a measuring current of the appropriate intensity.

[0078] The analog-to-digital converter transforms the analog voltage drop across the corresponding line branch into a digital signal and outputs it as a signal. This output signal is then forwarded to the control unit.

[0079] According to another embodiment, the reference line branch is shorter than the measuring line branch, and / or the reference line branch is shorter than the measuring line branch 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.

[0080] This means the reference resistor is located close to the current source and the voltage sensing unit. In contrast, the measuring cable branch is relatively long, meaning the connection unit and thus the measuring resistor connected to it (e.g., a temperature sensor) are located further away from the current source and the voltage sensing unit. Therefore, the parasitic resistance (e.g., the line resistance) of the measuring cable branch is relatively high. The reason for the long measuring cable branch is, for example, a remotely located object whose temperature is to be measured. Because the same (e.g., long) measuring cable 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 length of the measuring cable branch.

[0081] The measuring line branch extends, in particular, from line points that are contacted by the switching unit in the measuring switching position to the connection unit. For example, the measuring line branch extends 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 of the connection unit, and from a second terminal 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.

[0082] According to another embodiment, the measuring device further comprises several of the measuring line branches, wherein Each measuring line branch has a connection unit for optionally connecting a measuring resistor or at least one calibration component electrically, the switching unit is set up to selectively connect the power source in the reference switching position to the reference line branch or in several measuring switching positions accordingly to the several measuring line branches, the voltage detection unit is optionally set up to detect a voltage either on the reference line branch or on the several measuring line branches, and The control unit is set up to determine a respective parasitic resistance value of the measuring device for each measuring line branch based on the detected reference voltage and the corresponding of the several detected measuring voltages on the several measuring line branches.

[0083] 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 taken 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.

[0084] According to another embodiment, the measuring device further comprises 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.

[0085] The circuit board is, in particular, a printed circuit board on which the individual components mentioned 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 have an interface unit for connecting at least a second conductor section of the measuring conductor branch.

[0086] In some 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 corrected.

[0087] According to a second aspect, a lithography system is proposed. The lithography system comprises a measuring device and an optical system as described above, wherein the measuring resistor of the measuring device is arranged on or in the optical system.

[0088] The optical system includes, for example, an optical element (e.g., a mirror or a lens) and / or an actuator for an optical element.

[0089] In a measuring device with multiple measuring leads and therefore multiple measuring resistors, one measuring resistor is arranged on or in the optical system. For example, several or all of the multiple measuring resistors are arranged on a single object being measured (e.g., an optical element) of the optical system, and / or the multiple measuring resistors are arranged (e.g., each) on different objects being measured (e.g., optical elements).

[0090] In various embodiments, the lithography system further features: 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 physically separated from the first enclosed area and in which the power source and the voltage sensing unit are located, and Connecting lines that electrically connect the first closed area and the second closed area in such a way 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 one section of the measuring line branch.

[0091] For example, the reference resistor, the reference line branch and / or the switching unit is / are located in the second enclosed area.

[0092] 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.

[0093] 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 within and bounded by enclosures. The connecting lines serve, in particular, for the electrical coupling of the two areas.

[0094] For example, the first enclosed area is under vacuum, and the second enclosed area is not under vacuum.

[0095] 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 which is electrically conductively connected to a calibration component and alternatively electrically connectable to a measuring resistor, c) Detecting a reference voltage at the reference branch when the reference branch is energized, and detecting a measurement voltage at the measurement branch when the measurement 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.

[0096] The fact that the reference line branch and the measurement line branch are energized sequentially means, in particular, that they are energized selectively and / or alternately (i.e., each line branch is energized at least once). In other words, the measurement line branch is energized at a first time and / or during a first period, and the reference line 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.

[0097] According to one embodiment of the third aspect, the method after step d) has: Disconnecting the electrically conductive connection between the connection unit of the measuring line branch and the calibration component, electrically conductive connection of the connection unit to the measuring resistor,

[0098] Energizing the measuring line branch with the measuring current, Detecting an additional measuring voltage at the measuring line branch when the measuring line branch is energized, and Determining the resistance-dependent measured quantity based on the recorded reference voltage of the reference resistor, the recorded additional measurement voltage on the measuring line branch, and the determined parasitic resistance value of the measuring device.

[0099] In particular, the method according to this embodiment is a method for measuring a resistance-dependent measurand in or on an optical system of the lithography system. Furthermore, the method for measuring the resistance-dependent measurand includes the method for calibrating the measuring device described above.

[0100] The term "one" here is not necessarily to be understood as restricting the number to exactly one element. Rather, it can also refer to multiple elements, such as two, three, or more. Similarly, every other counter used here should not be interpreted as restricting the number to the exact number stated. Instead, numerical deviations, both higher and lower, are possible unless otherwise specified.

[0101] The embodiments and features described for the measuring device apply accordingly to the lithography system and the proposed method, and vice versa.

[0102] Other 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.

[0103] 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 will be explained in more detail below with reference to preferred embodiments and the accompanying figures. Fig. Figure 1 shows a schematic meridional section of a projection exposure system for EUV projection lithography according to one embodiment; Fig. Figure 2 shows a measuring device of the projection exposure system. Fig. 1 according to a first embodiment, wherein a reference switching position of the measuring device is shown; Fig. 3 shows the measuring device Fig. 2 in a measuring switching position, wherein a calibration resistor is connected to a measuring line branch of the measuring device; Fig. 4 shows the measuring device Fig. 2 in the measuring switch position, wherein a measuring resistor is connected to the measuring line branch of the measuring device; Fig. Figure 5 shows a measuring device of the projection exposure system. Fig. 1 according to a second embodiment; Fig. Figure 6 shows a measuring device of the projection exposure system. Fig. 1 according to a third embodiment; and Fig. Figure 7 shows a flowchart of a method for calibrating a measuring device of a projection exposure system according to one embodiment.

[0104] In the figures, identical or functionally equivalent elements have been labelled with the same reference symbols, unless otherwise indicated. Furthermore, it should be noted that the representations in the figures are not necessarily to scale.

[0105] Fig. Figure 1 shows an embodiment of a projection exposure system 1 (lithography system), in particular an EUV lithography system. One embodiment of the illumination system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, an illumination 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 illumination system 2. In this case, the illumination system 2 does not include the light source 3.

[0106] A reticule 7 arranged in the object field 5 is exposed. The reticule 7 is held by a reticule holder 8. The reticule holder 8 can be moved, particularly in a scanning direction, via a reticule displacement drive 9.

[0107] 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. The scan direction runs in the Fig. 1 along the y-direction y. The z-direction z runs perpendicular to the object plane 6.

[0108] The projection exposure system 1 comprises 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.

[0109] A structure on the reticulum 7 is imaged onto a photosensitive 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, particularly along the y-direction y, via a wafer transfer drive 15. The movement of the reticulum 7 via the reticulum transfer drive 9 and of the wafer 13 via the wafer transfer drive 15 can be synchronized.

[0110] Light source 3 is an EUV radiation source. 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. Light source 3 can be a plasma source, for example, an LPP source (Laser Produced Plasma) or a DPP source (Gas Discharged Produced Plasma). It can also be a synchrotron-based radiation source. Light source 3 can be a free-electron laser (FEL).

[0111] 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 illumination 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 to optimize its reflectivity for the useful radiation and to suppress stray light.

[0112] 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.

[0113] The illumination optics 4 comprise a deflecting mirror 19 and, downstream in the beam 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 shape 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 the 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 referred to as field facets. Of these first facets 21, the following are in the Fig. 1 only some examples are shown.

[0114] The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or semicircular border contour. The first facets 21 can be designed as planar facets or alternatively as convexly or concavely curved facets.

[0115] As is known, for example, from DE 10 2008 009 600 A1, the first facets 21 can themselves each be composed of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirror 20 can in particular be designed as a microelectromechanical system (MEMS system). For details, reference is made to DE 10 2008 009 600 A1.

[0116] Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction y.

[0117] 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. Specular reflectors are known from US 2006 / 0132747 A1, EP 1 614 008 B1, and US 6,573,978.

[0118] The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0119] The second facets 23 can also be macroscopic facets, which may, for example, have round, rectangular, or hexagonal edges, or alternatively, facets composed of micromirrors. Reference is also made to DE 10 2008 009 600 A1 in this regard.

[0120] The second facets 23 can have planar or alternatively convex or concave curved reflective surfaces.

[0121] The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a honeycomb condenser (English: Fly's Eye Integrator).

[0122] It can be advantageous not to arrange the second faceted mirror 22 exactly in a plane that is optically conjugate to a pupil plane of the projection optics 10. In particular, the second faceted mirror 22 can be arranged tilted relative to a pupil plane of the projection optics 10, as described, for example, in DE 10 2017 220 586 A1.

[0123] With the aid of the second faceted mirror 22, the individual first facets 21 are imaged 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.

[0124] In another embodiment of the illumination optics 4, not shown, a transmission optic can be arranged in the beam path between the second facet mirror 22 and the object field 5, which contributes in particular to imaging the first facets 21 into the object field 5. The transmission optic can have exactly one mirror, or alternatively two or more mirrors, arranged one behind the other in the beam path of the illumination optics 4. The transmission optic can, in particular, comprise one or two mirrors for normal incidence (NI mirrors) and / or one or two mirrors for grazing incidence (GI mirrors).

[0125] The lighting optics 4, in the version shown in the Fig. Figure 1 shows exactly three mirrors after the collector 17, namely the deflecting mirror 19, the first faceted mirror 20 and the second faceted mirror 22.

[0126] In a further embodiment of the lighting optics 4, the deflecting mirror 19 can also be omitted, so that the lighting optics 4 after the collector 17 can then have exactly two mirrors, namely the first faceted mirror 20 and the second faceted mirror 22.

[0127] The mapping 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 approximate mapping.

[0128] 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.

[0129] In the Fig. In the example shown, 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 doubly obscured optic. The penultimate mirror M5 and the last mirror M6 each have an aperture 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.

[0130] 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.

[0131] 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.

[0132] The projection optics 10 can be anamorphic. In particular, they have different image scales Bx, βy in the x and y directions x, y. The two image scales βx, βy of the projection optics 10 are preferably (βx, By) = (+ / - 0.25, + / - 0.125). A positive image scale β indicates a projection without image inversion. A negative sign for the image scale β indicates a projection with image inversion.

[0133] The projection optics 10 thus lead to a reduction in the x-direction x, that is, in the direction perpendicular to the scan direction, in a ratio of 4:1.

[0134] The projection optics 10 lead to a reduction of 8:1 in the y-direction y, that is, in the scan direction.

[0135] Other magnification ratios are also possible. Magnification ratios with the same sign and absolute value in the x and y directions (x, y), for example with absolute values ​​of 0.125 or 0.25, are also possible.

[0136] 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, 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.

[0137] 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 on the second facets 23 assigned to each of them.

[0138] The first facets 21 are each superimposed on a corresponding second facet 23 to illuminate the object field 5 on the reticle 7. The illumination of the 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.

[0139] The illumination of the entrance pupil of the projection optics 10 can be geometrically defined by arranging the second facets 23. 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 filling.

[0140] Another preferred pupil uniformity in the area of ​​defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by a redistribution of the illumination channels.

[0141] 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.

[0142] The projection optics 10 can, in particular, have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

[0143] The entrance pupil of the projection optics 10 cannot always 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.

[0144] The projection optics 10 may have different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second faceted mirror 22 and the reticle 7. This optical element can accommodate the different positions of the tangential and sagittal entrance pupils.

[0145] During the Fig. In the arrangement of the components of the illumination optics 4 shown in Figure 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 arranged tilted relative to the object plane 6. The first faceted mirror 20 is arranged tilted relative to an arrangement plane defined by the deflecting mirror 19. The first faceted mirror 20 is arranged tilted relative to an arrangement plane defined by the second faceted mirror 22.

[0146] Fig. Figure 2 shows a measuring device 100 according to a first embodiment. The measuring device 100 is located in the lithography system 1 of the Fig. 1. The measuring device 100 serves, for example, to measure a resistance-dependent 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 R, is used. Tused, which is arranged on the optical element 102, e.g. in direct physical contact with the optical element 102. The measuring device 100 serves only as an example to measure the temperature T of an optical surface of the faceted mirror 20 ( Fig. 1) to measure and the measuring resistor 104 is arranged on a rear side of the faceted mirror 20.

[0147] The measuring device 100 comprises a current source 106 for generating a measuring current I. The current source 106 is, for example, a DC current source that supplies a current I at its connection points 106a and 106b. The current source 106 includes, for example, a current 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 current generation unit 108 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 optionally be energized with the measuring current I.In particular, a switching unit 118 is provided, with the help of which either the measuring line branch 114 or the reference line branch 116 can be supplied with the measuring current I.

[0148] 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. Fig. 3 and Fig. Figure 4 shows 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.

[0149] The measuring line branch 114 has in particular an electrical line 124 which 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.

[0150] 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 be, for example, at least one calibration resistor 128, 128' and / or a short-circuit bridge 130.

[0151] The measuring resistor 104, for example, has a first connection point 104a and a second connection point 104b. Furthermore, 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.

[0152] The connection unit 126 is, for example, a two-pole connection unit 126 with a first terminal 126a and a second terminal 126b. The first terminal 114a of the measuring line branch 114 is, for example, directly electrically connected via line 124 to the first terminal 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.

[0153] Additionally, the first terminal 126a of the connection unit 126 is suitable, for example, for electrical connection to the corresponding first connection point 104a, 128a, 128a', 130a of the measuring resistor 104 or one of the at least one calibration component 128, 128', 130. Furthermore, the second terminal 126b of the connection unit 126 is suitable, for example, for electrical connection to the corresponding second connection point 104b, 128b, 128b', 130b of the measuring resistor 104 or of the at least one calibration component 128, 128', 130.

[0154] For example, the connection unit 126 is detachably (e.g., by means of a plug connection) electrically connected to the measuring resistor 104 or 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, electrically connected, and then disconnected again. For example, the terminals 126a, 126b of the connection unit 126 and the terminals 104a, 104b of the measuring resistor 104 have corresponding connecting elements.Furthermore, for example, the connection points 128a, 128b, 128a', 128b', 130a, 130b of the 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.

[0155] The measuring device 100 also includes a reference resistor 132 with a reference resistance value R R , which is located on the reference line branch 116. The reference numerals 132a and 132b accordingly designate a first and second connection point of the reference resistor 132.

[0156] The reference line branch 116 has, in particular, a further electrical line 134 that electrically connects a first line point 116a to 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 line point 116b of the reference line branch 116 is, for example, directly electrically connected to the second connection point 132b of the reference resistor 132.

[0157] The reference resistor 134 arranged on the reference line branch 116 with reference resistance value R R It is powered in the reference switching position 120 and is used to perform a reference measurement.

[0158] The connection unit 126 arranged on the measuring line branch 114 is in the measuring switching position 122 ( Fig. 3) energized with the measuring current I. 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 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.

[0159] The switching unit 118, which directs the measuring current I 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, 116a to 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 both switching elements 118a, 118b simultaneously.

[0160] The control unit 112 of the measuring device 100 is also, for example, configured to control the switching unit 118 (control signal B in Fig. 2).

[0161] The measuring device 100 also includes a voltage detection unit 136 for detecting a voltage U R , U M , U T Reference numerals 136a and 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 it is in the reference switching position 120 ( Fig. 2) 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 such that in the measuring switching position 122 ( Fig. 3) is connected in parallel to the measuring line branch 114.

[0162] This means that the voltage sensing unit 136 in the reference switching position 120 detects a reference voltage U dropping across the reference line branch 116. R measures ( Fig. 2) In addition, the voltage detection unit 136 measures a measuring voltage U dropping across the measuring line branch 114 in the measuring switching position 122. M ( Fig. 3).

[0163] 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 T The 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.

[0164] To determine a parasitic resistance value R PThe measuring device 100 is first electrically connected to the connection unit 126 of the measuring line branch 114 with 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 shown.

[0165] 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 ​​R. K , R KThen, 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 R K , R K ' of the preselected calibration resistance 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.

[0166] Then the measuring device 100 is switched to the reference switching position 120 ( Fig. 2) and a reference voltage value U R of the reference line branch 116, i.e., the reference resistor 132, is detected and transmitted (e.g., as signal C) to the control unit 112.

[0167] 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 U is obtained. M of the measuring line branch 114 with the calibration resistor 128 connected to it is detected and transmitted (e.g. as signal C) to the control unit 112.

[0168] 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.

[0169] This is R R the predetermined resistance value of the reference resistor 132. Furthermore, R M a resistance value of the measuring line branch 114, which has a parasitic resistance value R P includes. 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. MThe total resistance of the measuring line branch 114 is a parallel circuit consisting of the calibration resistor 128 and the parasitic resistance. Therefore, the total resistance value R is... M of the measuring line branch 114, the resistance value R K of the calibration resistor 128 and the parasitic resistance value R P : RM=(RK⋅RP) / RK+RP. Consequently, the voltage measurement of U can first be used to determine the voltage. R and U M and with a known resistance value R R of the reference resistor 132 the resistance value R M of measuring line branch 114. From the calculated resistance value R M The measuring line branch 114 can then be determined according to the above equation if the resistance value R is known beforehand. K of the calibration resistor 128 the parasitic resistance value R P The measuring device 100 will be calculated.

[0170] Although in Fig. Not shown in Figure 3, the short-circuit bridge 130 can be connected to the terminal unit 126 instead of the calibration resistor 128 (or the further calibration resistor 128'). Therefore, 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 voltage measurement of U can be used. R and U M and with a known resistance value R R of the reference resistor 132 the parasitic resistance value R P The measuring device 100 can be calculated as follows: RP=RM=UM⋅(RR / UR).

[0171] After the parasitic resistance value R PThe result determined by the measuring device 100 can be taken into account when measuring the resistance-dependent measured quantity T (e.g. the temperature T) of the object being measured 102.

[0172] 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 measuring voltage value U is measured. T of the measuring line branch 114 with the measuring resistor 104 and transmitted (e.g. as signal C) to the control unit 112.

[0173] The uncalibrated resistance value R T The resistance of the measuring resistor 104 can then be calculated as follows: RT=UT / I=UT⋅(RR / UR).

[0174] Additionally, the control unit 112 now takes into account the previously determined parasitic resistance value R. P For example, the uncalibrated resistance value R is determined 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 R P subtracted. This allows for a calibrated resistance value R. T The resistance of the measuring resistor 104 can be calculated as follows: RT'=RT−RP.

[0175] From the calibrated resistance value R T ' of the measuring resistor 104 the control unit 112 then determines a measured quantity T (e.g. a temperature T) by applying a pre-stored resistance-measured quantity characteristic curve.

[0176] In Fig. Figure 5 shows a measuring device 200 according to a second embodiment. The following only describes the differences from the measuring device 100 according to the first embodiment ( Fig. 2 to 4) described.

[0177] 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 the automatic electrical connection of either a measuring resistor 204 or at least one 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).

[0178] The measuring resistor 204 in Fig. 5 is similarly designed to the one in connection with the Fig. 2 to 4 described measuring resistor 104. Also the at least one calibration component 228, 228', 230 in Fig. 5 is similarly designed to those associated with the Fig. 2 to 4 described at least one calibration component 228, 228', 230.

[0179] Furthermore, the connection unit 226 – apart from the fact that the switching device 240 is electrically connected to it – is designed similarly to those in connection with the Fig. 2 to 4 described connection unit 126.

[0180] The control unit 212 in Fig. 5 differs from the one related to the Fig. The control unit 112 described in sections 2 to 4 differs only in that it is designed to control, in addition to the functions of the control unit 112, the switching device 240, in particular the further switching unit 242.

[0181] 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.

[0182] As in Fig. As can be seen in Figure 5, 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 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.

[0183] The additional 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.

[0184] As exemplified in Fig. Figure 5 shows the measuring device 200 with dashed lines; each of the measuring devices 100, 200, 300 described herein may optionally include one or more circuit boards 256, 258.

[0185] For example, the measuring device 200 has Fig. 5 (or also the measuring device 100 in the Fig. 2 to 4 and / or the measuring device 300 in Fig. 6) a first circuit board 256. The first circuit board 256 contains, for example, the power source 106, the voltage sensing unit 136, the switching unit 118, the reference line branch 116, and the reference resistor 132. Optionally, the control unit 212 (e.g., also the control units 112, 312) can also be located on the first circuit board 256.

[0186] For example, the measuring device 200 has Fig. 5 (or also the measuring device 100 in the Fig. 2 to 4 and / or the measuring device 300 in Fig. 6) a second circuit board 258. The connection unit 226 (e.g., also the connection unit 126, 326, 326') is arranged on the second circuit board 258. Optionally, the measuring resistor 104, 204 and at least one calibration component 128, 128', 130, 228, 228', 230 can also be arranged on the second circuit board 258. If a switching device 240 with a further switching unit 242 is provided, the switching device 240 can also be arranged on the second circuit board 258.

[0187] The measuring line branch 214, for example, is only partially arranged 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 terminal point 214a of the measuring line branch 214 to the first terminal 226a of the connection unit 226 and from the second terminal 226b of the connection unit 226 to the second terminal 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. Figure 5 shows, for example, that 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 and 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 Figure 5. Fig. 5 shown. 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.

[0188] The first circuit board 256 can also have an interface unit 260 (e.g. connection poles 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.

[0189] Although not shown in the figures, the second circuit board 258 may also have another interface unit (e.g. with two connection poles) 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.

[0190] In Fig. Figure 6 shows a measuring device 300 according to a third embodiment. Only the 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 ( Fig. 2 to 4) by the fact that the measuring device 300 has several measuring line branches 314, 314'. Each of the several measuring line branches 314, 314' is like the measuring line branch 114 in the Fig. 2 to 4 (or also like the measuring line branch 214 in Fig. 5) designed. This means in particular that each of the several measuring line branches 314, 314' has a connection unit 326, 326' for the optional electrical connection of a measuring resistor 104 or at least one calibration component 128, 128', 130 ( Fig. 2) is arranged. Each of the connection units 326, 326' accordingly has a first and second connection pole 326a, 236b, 326a', 326b'.

[0191] Furthermore, a switching unit 318 is 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 for selectively connecting the power source 106 in a reference switching position 320 with the reference line branch 116 or in several measuring switching positions (not in Fig. (as shown in Figure 6) is configured accordingly with the multiple measuring line branches 314, 314'. In particular, 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).

[0192] Furthermore, the voltage detection unit 136 is used to detect a voltage U R , U M , U T , Fig. 2 to 4) provided. Depending on the switching position of the switching unit 318, a voltage can be measured with the voltage sensing unit 136 either at the reference line branch 116 or at any of the several measuring line branches 314, 314'.

[0193] 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, they have a parasitic resistance value R P1 , R P2 The measuring device 300 can determine the value for each of the several measuring line branches 314, 314'. For example, the control unit 312 can determine a first parasitic resistance value R. P1 based on the recorded reference voltage U Rand determine a measured voltage recorded for the first measuring line branch 314. Furthermore, the control unit 312 can, for example, determine a second parasitic resistance value R. P2 based on the recorded reference voltage U R and determine a measured voltage recorded for the second measuring line branch 318'.

[0194] Since a corresponding measuring resistor 104 ( is located on each measuring line branch 318, 318' Fig. 4) can be connected, by using several measuring line branches 318, 318', for example several measuring objects 102 can be measured, e.g. a temperature T of the several measuring objects 102 can be measured.

[0195] Although in Fig. Figure 6 shows two different measuring line branches 314, 314' as examples; more than two measuring line branches 314, 314' may also be provided.

[0196] The following refers to Fig. 7 A method for calibrating a measuring device 100, 200, 300 of a lithography system 1 is described. The measuring device 100, 200, 300 is set up for measuring a resistance-dependent measurand T in or on an optical system 102 of the lithography system 1.

[0197] The measuring device 100, 200, 300 is in particular one as described above in connection with the Fig. 2 to 6 described measuring device 100, 200, 300.

[0198] In a first step S1 of the procedure, a measuring current I is generated ( Fig. 2).

[0199] 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 U is applied. R detected on the reference line branch 116 when the reference line branch 116 is energized ( Fig. 2).

[0200] 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 U is applied. M on the measuring line branch 114, 214, 314, 314' when the measuring line branch 114, 214, 314, 314' is energized.

[0201] In a fourth step S4 of the procedure, a parasitic resistance value R is determined. P , R P1 , R P2 the measuring device 100, 200, 300 based on the detected reference voltage U R and the measured voltage U M determined.

[0202] 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.

[0203] 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).

[0204] 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 performed fully automatically.

[0205] 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).

[0206] In an optional eighth step S8 of the procedure, a further measuring voltage U is applied. T on the measuring line branch 114, 214, 314, 314' when the measuring line branch 114, 214, 314, 314' is energized ( Fig. 4).

[0207] In an optional ninth step S9 of the procedure, the resistance-dependent measured quantity T is calculated based on the detected reference voltage U. R of the reference resistor 132, the measured additional measurement voltage U T on the measuring line branch 114, 214, 314, 314' and the determined parasitic resistance value R P , R P1 , R P2 The measuring device determined 100, 200, 300.

[0208] 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 precisely and without great effort.

[0209] Although the present invention has been described using exemplary embodiments, it can be modified in many ways. REFERENCE MARK LIST 1 Projection exposure system 2 Lighting system 3 light source 4 Lighting optics 5 object field 6 Object level 7 reticles 8 label holders 9 Reticle displacement drive 10 Projection optics 11 Image field 12 Image plane 13 wafers 14 wafer holders 15 wafer transfer drive 16 Lighting radiation 17 Collector 18 Intermediate focus plane 19 deflecting mirrors 20 first faceted mirror 21 first facet 22 second faceted mirror 23 second facet 100 measuring device 102 Measuring object 104 Measuring resistor 104a Connecting element 104b Connecting element 106 Power source 106a Connection point 106b Connection point 108 power generation units 110 Digital-to-Analog Converters 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 switch position 124 Line 126 connection unit 126a Connecting element 126b Connecting element 128 Calibration components 128a Connection point 128b Connection point 128' Calibration component 128a' Connection point 128b' Connection point 130 Calibration component 130a Connection point 130b Connection point 132 Reference resistor 132a Connection point 132b Connection point 134 Management 136 Voltage detection unit 136a Connection point 136b Connection point 138 Analog-to-Digital Converters 200 measuring devices 204 Measuring resistor 204a Connection point 204b Connection point 212 Control unit 214 Measuring line branch 214a Line point 214b Line 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 244 Line 244a Line 244b Line 246 Line 246a Line 246b Line 248 Line 248a Line 248b Line 250a line 250b line 252 Connection unit 252a Connection pole 252b Line point 254 Switching element 256 ladder map 258 ladder map 260 interface unit 260a connection pole 260b connection pole Section 262 Section 264 266 Line section 300 measuring device 312 Control unit 314 Measuring line branch 314a Line point 314b Line point 314' Measuring line branch 314a' Line point 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 Electricity M1-M6 mirrors R K resistance value R K ' Resistance value R M resistance value R P resistance value R P1 resistance value R P2 resistance value R R resistance value R T , R T ' Resistance value S circuit S1-S9 process steps Temperature U R Tension U M Tension U T Tension QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] EP 0 120 102 A1

[0005] DE 10 2008 009 600 A1 [0115, 0119] US 2006 / 0132747 A1

[0117] EP 1 614 008 B1

[0117] US 6,573,978

[0117] DE 10 2017 220 586 A1

[0122] US 2018 / 0074303 A1

[0136]

Claims

[1] 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 power source (106) in a reference switching position (120) with the reference line branch (116) or in a measuring switching position (122) with the measuring line branch (114), a connection unit (126) arranged on the measuring line branch (114) for optionally connecting a measuring resistor (104) or at least one calibration component (128, 130) electrically, a reference resistor (132) arranged on the reference line branch (116), a voltage sensing unit (136) for sensing a voltage (U R , U M) optionally at the reference line branch (116) or the measuring line branch (114), and a control unit (112) for determining a parasitic resistance value (R) P ) of the measuring device (100) based on a reference voltage (U) detected in the reference switching position (120) R ) and a measured voltage (U) 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). M ). [2] Measuring device according to claim 1, wherein which has at least one calibration component (128, 130) and at least one calibration resistor (128), and the control unit (112) is configured to determine the parasitic resistance value (R) P ) based on the recorded reference voltage (U R ) of the reference resistor (132), a predetermined reference resistor value (R R) of the reference resistor (132), which in the measuring switching position (122), in which one of the at least one calibration resistor (128) is connected to the connection unit (126), measured voltage (U) M ) and a predetermined calibration resistance value (R K ) of one calibration resistance (128) to determine. [3] Measuring device according to claim 1 or 2, wherein which has at least one calibration component (128, 130) with a short-circuit bridge (130), and the control unit (112) is configured to measure the parasitic resistance value (R) P ) based on the recorded reference voltage (U R ) of the reference resistor (132), a predetermined reference resistor 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 measure the resistance-dependent measured quantity (T) based on a reference voltage (U) detected in the reference switching position (120). R ) of the reference resistor (132), a further measuring voltage (U) 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). T ) and the determined parasitic resistance value (R P ) 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). [6] 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 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 the measuring resistor (204), the at least one calibration resistor (228) or the short-circuit bridge (230) electrically to the connection unit (226). [8] Measuring device according to one of claims 1 to 7, wherein the at least one calibration component (128, 128', 130) comprises several calibration resistors (128, 128') with different calibration resistance values ​​(R) K , R K') has the connection unit (126) of the measuring line branch (114) in the measuring switching position (122) is electrically connected 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 (R K ) of the preselected calibration resistance (128) by 30% or less, 20% or less and / or 10% or less from a pre-estimated resistance value of the parasitic resistance (R) P ) differs. [9] Measuring device according to any 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 (138) for converting a detected analog voltage value (U) R , U M , U T ) has a digital voltage signal (C). [10] Measuring device according to any 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') is arranged on each measuring line branch (314, 314') for the optional electrical connection of a measuring resistor (104) or at least one calibration component (128, 130), the switching unit (318) is configured to selectively connect the power source (106) in the reference switching position (120) with the reference line branch (116) or in several measuring switching positions (122) accordingly with the several measuring line branches (314, 314'), the voltage detection unit (136) for detecting a voltage (U R , U M ) is optionally set up on the reference line branch (116) or on the several measuring line branches (314, 314'), and the control unit (112) for determining a respective parasitic resistance value (R) P1 , R P2 ) of the measuring device (100) for each measuring line branch (314, 314') based on the detected reference voltage (U R ) and the corresponding of the several recorded measurement voltages (U 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 detection unit (136), the switching unit (118), the reference line branch (116) and the reference resistor (132) are arranged. [13] Lithography system (1) comprising 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 one of claims 1 to 12, wherein the measuring device (100) is configured to measure 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) Determining (S2) a reference voltage (U R ) on the reference line branch (116) when the reference line branch (116) is energized, and detecting (S3) a measuring voltage (U) M ) on the measuring line branch (114) when the measuring line branch (114) is energized, and d) Determining (S4) a parasitic resistance value (R) P ) of the measuring device (100) based on the detected reference voltage (U R ) and the measured voltage (U M ). [15] Method according to claim 14, comprising step d): Disconnecting (S5) the electrically conductive connection between the connection unit (126) of the measuring line branch (114) and the calibration component (128, 130), 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), Acquiring (S8) another measuring voltage (U T ) on the measuring line branch (114) when the measuring line branch (114) is energized, and Determine (S9) the resistance-dependent measured quantity (T) based on the detected reference voltage (U). R ) of the reference resistor (132), the detected further measurement voltage (U T ) on the measuring line branch (114) and the determined parasitic resistance value (R) P ) the measuring device (100).

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