DE102018211077A1 - LITHOGRAPHIC APPARATUS AND METHOD FOR OPERATING A LITHOGRAPHIC APPARATUS - Google Patents

Abstract

The invention relates to a lithography system (100) having a radiation source (106A) for generating radiation having a specific repetition frequency, an optical component (200) for guiding the radiation in the lithography system, an actuator device (210) for displacing the optical component capacitive sensor (230) having a number of sensor electrodes (231-236) connected to the optical component for measuring the position of a tilt angle of the optical component (200), one via electrical lines to the sensor electrodes (231-236 ) associated evaluation unit (237) proposed. The evaluation unit (237) is set up to excite the optical component (200) and the sensor electrodes (231-236) connected to the optical component (200) with an excitation signal (S3, V) and produce a resulting measurement signal (S2). to receive and evaluate. In this case, the evaluation unit (237) to a readout circuit (238) with switched capacitors (C) and one of the readout circuit (238) upstream common mode compensation circuit (239) with switched capacitors (251, 252), in which the compensation voltage (V) and / or the compensation capacity (C) is adjustable.

Description

The present invention relates to a lithography system and a method for operating a lithography system. The lithographic system comprises a radiation source for generating a radiation having a specific repetition frequency, an optical component, for example a mirror, for guiding the radiation in the lithography apparatus, an actuator device for displacing the optical component and a measuring device for determining a position of the optical component.

Microlithography is used to fabricate microstructured devices such as integrated circuits. The microlithography process is performed with a lithography system having an illumination system and a projection system. The image of a mask (reticle) illuminated by means of the illumination system is projected by the projection system onto a substrate (eg a silicon wafer) coated with a photosensitive layer (photoresist) and arranged in the image plane of the projection system in order to apply the mask structure to the photosensitive layer Transfer coating of the substrate.

Driven by the quest for ever smaller structures in the manufacture of integrated circuits, EUV lithography systems are currently being developed which use light with a wavelength in the range of 0.1 nm to 30 nm, in particular 4 nm to 6 nm. In such EUV lithography equipment, because of the high absorption of most materials of light of this wavelength, reflective optics, that is, mirrors, must be used instead of - as before - refractive optics, that is, lenses. For the same reason, beamforming and beam projection should be performed in a vacuum.

The mirrors can z. B. on a support frame (English: force frame) and at least partially manipulated or tilted designed to allow movement of a respective mirror in up to six degrees of freedom and thus a highly accurate positioning of the mirror to each other, especially in the pm range , Thus, occurring during operation of the lithographic system changes in the optical properties, eg. B. as a result of thermal influences to be corrected.

For the process of the mirror, in particular in the six degrees of freedom, these actuators are assigned, which are controlled via a control loop. As part of the control loop, a device for monitoring the tilt angle of a respective mirror is provided.

For example, from the WO 2009/100856 A1 a facet mirror for a projection exposure system of a lithography system is known, which has a plurality of individually displaceable individual mirrors. In order to ensure the optical quality of a projection exposure apparatus, a very precise positioning of the movable individual mirrors is necessary.

Furthermore, the document describes DE 10 2013 209 442 A1 in that the field facet mirror can be designed as a microelectromechanical system (MEMS). However, on the one hand pulsed plasma can be generated by the photons of the EUV radiation source of the lithography system in the residual gas in the illumination system and on the other hand electrons can be released from the mirror surfaces of the MEMS mirrors by the photoelectric effect. As a result, temporally and spatially varying current flows can occur via the MEMS levels of the field facet mirror. These temporally and spatially varying current flows via the MEMS mirrors can sensitively disturb the evaluation electronics of the device for monitoring the tilt angle of the respective mirror.

In addition, the document shows WO 2017/005849 A1 a lithography system, which comprises a radiation source for generating a radiation having a certain repetition frequency, an optical component for guiding the radiation in the lithography system, an actuator device for displacing the optical component, a capacitive sensor which has a number of sensors connected to the optical component -Electrode for measuring the position of a tilt angle of the optical component, and having an electrical lines connected to the sensor electrodes evaluation unit, which is adapted to excite the optical component and the sensor component connected to the sensor electrode with an excitation signal, and to receive and evaluate a resulting measurement signal.

This shows the 7 an example of a simplified equivalent circuit diagram of such a capacitive sensor 254 and a downstream evaluation unit 270 for such an EUV lithography system.

An example of a capacitive sensor is in 2 of the document WO 2017/005849 A1 shown. The capacitive sensor of this 2 (see also this 2 ) includes two sensor arrays with electrodes whose capacitances in the present 7 are designated C _CS1 and C _cs3 . Furthermore, in the 7 V _ex the excitation signal (see S3 in 2 ), V _ss a reference potential or reference potential, R _p1 a parasitic conduction resistance, R _p2 a parasitic conduction resistance, C _p1 a parasitic conduction capacitance, C _p2 a parasitic conduction capacitance and C _h a holding capacitance.

The evaluation unit 270 of 7 comprises a readout circuit 271 and an ICMFB stage 272 (ICMFB, upstream of the readout circuit 271) comprising a transconductance amplifier 273. The ICMFB stage 272 acts as a compensation circuit for compensating the DC component of the measurement signal (see S2 in FIG 2 ) and may also be referred to as a common-mode compensation circuit.

$${\text{C}}_{\text{CS1}}={\text{C0+dC}}_1$$

$${\text{C}}_{\text{CS3}}={\text{C0+dC}}_3$$

The readout circuit 271 is based on switched capacitors Ci. The capacitors C _i are switched by means of the switches S ₃ , S ₄ . In this case, the read-out circuit 271 comprises a transconductance amplifier 274 (OTA, Operational Transconductance Amplifier). Thus, the readout circuit 271 is based on the SC (Switched Capacitor) technology. The integration capacitances C _i are reset by means of the switches S ₃ and S ₄ . After the switches S ₃ , S ₄ are opened again, a jump is applied to V _ex . The resulting charge is integrated at the integration capacitances C _i and converted into an output voltage V _out . The output voltage V _{out is} calculated according to equation (1) below: $${\text{V}}_{\text{out}}=\frac{{\text{C}}_{\text{CS1}}-{\text{C}}_{\text{CS3}}}{{\text{C}}_{\text{i}}}\cdot {\text{V}}_{\text{ex}}$$

$${\text{C}}_{\text{CS1}}={\text{C0 + <figure-callout id="1" label="dC" filenames="DE102018211077A1\_0009.png" state="{{state}}">dC</figure-callout>}}_1$$

$${\text{C}}_{\text{CS3}}={\text{C0 + dC}}_3$$

In the above equations (2) and (3), C0 denotes the DC component to be compensated (also referred to as a common mode component or CM component) of the signal, where dC ₁ and dC ₃ indicate the difference signals.

The output voltage V _out is independent of the parasitic input capacitances C _p1 and C _p2 as long as the ICMFB stage 272 compensates all common mode components C0.

The maximum modulation range (V _{out_ICMFB} ) of the transconductance amplifier 273 of the ICMFB stage 272 is limited by the supply voltage. The minimum value for the capacitance C _{fb of} the ICMFB stage 272 can be calculated by the following equation (4): $${\text{C}}_{\text{fb}}>\frac{{\text{V}}_{\text{ex}}}{V_{Out\_ICMFB}}\cdot \text{C0}$$

In this case, the sum of the input capacitances increases by C _fb , which increases the noise due to the amplifier in the main path. As a result, the performance of the stage as a whole deteriorates, which results from Equation (5) below: $${\text{V}}_{\text{out}\text{, noise}\text{OTA}}\approx {\text{V}}_{\text{in}\text{, noise}\text{OTA}}\cdot \frac{\text{Max}\left({\text{C}}_{\text{p1}}.{\text{C}}_{\text{p2}}\right)+{\text{C}}_{\text{fb}}+{\text{C0 + C}}_{\text{i}}}{{\text{C}}_{\text{i}}}$$

In equation (5), _{Vout, noise, OTA} denotes the noise output voltage of the transconductance amplifier 274 (OTA) of the readout circuit 271, where V _{in, noise, OTA} denotes the noise input voltage of the transconductance amplifier 274.

From the above equation (5), the following relationship can be seen: At high DC components CO to be compensated, the capacitance C _{fb is} to be selected to be higher, as a result of which the noise-induced output voltage V _{out, noise, OTA} increases according to equation (5).

Against this background, an object of the present invention is to provide an improved lithography system.

Accordingly, a lithography system is proposed which comprises a radiation source for generating a radiation having a certain repetition frequency, an optical component for guiding the radiation in the lithography system, an actuator device for displacing the optical component, a capacitive sensor which is a number of optical Component-connected sensor electrodes for measuring the position of a tilt angle of the optical component, an evaluation unit connected via electrical lines with the sensor electrodes, which is adapted to excite the optical component and the sensor connected to the sensor electrode with an excitation signal and receive and evaluate a resulting measurement signal. In this case, the evaluation unit to a readout circuit with switched capacitors and a read-out circuit upstream common mode compensation circuit with switched capacitors, in which the compensation voltage and / or the compensation capacitance is adjustable.

The present common-mode compensation circuit is based on switched capacitors, in which the compensation voltage and / or or the compensation capacity is / is adjustable. By the adjustability of the compensation voltage and / or the compensation capacitance, the present common mode compensation circuit can satisfy the equation (6) below without increasing the noise in the main path at high DC components CO to be compensated. This is the performance of the entire stage compared to the example of 7 clearly increased. $${\text{V}}_{\text{ex}}\cdot {\text{C0 = V}}_{\text{CMcomp}}\cdot {\text{C}}_{\text{CMcomp}}$$

In particular, the present common-mode compensation circuit may implement the ICMFB stage 272 of FIG 7 replace. This replacement can reduce power consumption and space consumption by up to 30%, especially since the common-mode compensation circuit based on the SC (Switched Capacitor) technology requires very little space. Furthermore, the parasitic input capacitance can be significantly reduced with a suitable choice of the compensation voltage and / or the compensation capacity. This significantly reduces the noise requirements of the main readout branch and thus also the power and area can be additionally saved there.

The radiation generated by the radiation source can lead with its high-energy photons to a charge transfer to the optical component or from the optical component. This charge transfer can lead to mechanical stimulation of the same, in particular in the case of an electromechanically actuable, displaceable optical component. In other words, the optical component can be mechanically excited and / or disturbed by the application of radiation. In particular, high-energy photons from the radiation source, in particular EUV photons, can lead to the generation of a plasma, in particular a hydrogen plasma. Alternatively, argon (Ar) or helium (He) can be used as purge gas. In this case, for example, oxygen (O) and nitrogen (N) can be used as admixtures.

Because the measuring signal frequency of the measuring device is in particular unequal to the repetition frequency of the radiation source and unequal to the integer multiples of the repetition frequency, the measuring device is advantageously desensitized. In particular, the measuring device is desensitized to current pulses which, due to the wavelengths used, for example 0.1 nm to 30 nm, of the radiation source are generated by charge carriers triggered from the surface of the optical component or the plasma.

The displaceable optical component may in particular be a mirror, in particular a micromirror, i. act a mirror with a side length of less than 1 mm. The mirror or micromirror may in particular be part of a multi-mirror array (MMA). The MMA may comprise over 1,000, especially over 10,000, more preferably over 100,000 such levels. In particular, these may be mirrors for reflection of EUV radiation.

The optical component may in particular be part of a facet mirror, in particular a field facet mirror, a beam shaping and illumination system of the lithography system. In this case, the optical component is arranged in particular in an evacuable chamber. During operation of the lithography system, this evacuatable chamber can be evacuated to a pressure of less than 50 Pa, in particular less than 20 Pa, in particular less than 10 Pa, in particular less than 5 Pa. In particular, this pressure indicates the partial pressure of hydrogen in the evacuatable chamber.

The radiation source is in particular an EUV radiation source with an emitted useful radiation in the range between 0.1 nm and 30 nm, preferably between 4 and 6 nm. It can be a plasma source, for example a GDPP source (plasma generation by gas discharge, gas Discharge Produced Plasma) or an LPP source (plasma generation by laser, laser-produced plasma) act. Other EUV radiation sources, for example based on a synchronous tone or on a free electron laser (FEL), are also possible.

According to one embodiment, the readout circuit is formed as a fully differential switched-capacitor readout circuit having a transconductance amplifier.

According to a further embodiment, the lithography system comprises a synchronization unit, which is set up to switch the compensation voltage synchronously and in antiphase to the excitation signal.

By the synchronization of the compensation voltage to the excitation signal, the compensation of the DC component of the measurement signal is optimized.

In accordance with another embodiment, the lithography system includes a calibration unit configured to calibrate the compensation capacitance to compensate for drifting common mode noise.

According to a further embodiment, the sensor electrodes of the capacitive sensor are comb-shaped and arranged in a toothed manner.

According to a further embodiment, the capacitive sensor has a comb-like first sensor device with a number of sensor electrodes and a comb-like second sensor device with a number of sensor electrodes. In this case, each of the sensor devices is coupled to the evaluation unit via an electrical line for transmitting the respective measurement signal.

According to another embodiment, the common mode compensation circuit has an input common mode feedback stage in addition to the switched capacitors.

According to a further embodiment, the switched capacitors are set up for a coarse compensation of the DC component of the measurement signal, wherein the input common mode feedback stage is set up for the fine compensation of the DC component of the measurement signal.

Consequently, the DC component is first roughly and, in particular, statically compensated via SC technology of the switched capacitors, and then a more exact and dynamic compensation of the remaining interference takes place via the ICMFB stage. In particular, it is advantageously not necessary in this embodiment that the values for the respective excitation voltages, the offset component CO and the compensation capacitor are exactly present or exactly set, since the ICMFB stage has a potentially remaining error after compensation by corrects the capacitive feedback. Another advantage is that the SC technique according to the switched capacitors in this embodiment can be very simple, since no tuning is required. It is sufficient if the respective values are coarse. Dependencies, for example on the service life or the temperature, are unproblematic within certain limits, in particular with a variation of up to 20%. Furthermore, the ICMFB stage requirements of the common mode compensation circuit are as compared to the circuit of FIG 7 significantly reduced. The necessary modulation range of the transconductance amplifier of the ICMFB stage can be reduced by a factor of 10 here, for example. Thereby, the transconductance amplifier of the ICMFB stage can be efficiently implemented, so that the area consumption and the power consumption are reduced with the same performance of the evaluation unit. Furthermore, depending on the implementation, the sum of all input capacitances can be reduced and thus the input-related noise of the entire readout circuit can be reduced.

According to a further embodiment, the evaluation unit is configured to excite the optical component and the actuator and / or sensor devices connected to the optical component with an excitation signal having a predetermined excitation frequency and then to sample at the sampling frequency, the excitation frequency being equal to the sampling frequency ,

According to a further embodiment, the lithography system is an EUV lithography system.

According to a further embodiment, the radiation source is an EUV radiation source, which is set up to generate EUV radiation at the predetermined repetition frequency.

According to a further embodiment, the optical component is a mirror.

According to a further embodiment, the optical component is a single mirror or a field facet mirror of a beam shaping and illumination system of the lithography system.

According to a further embodiment, the optical component is an individual mirror of a pupil facet mirror of a beam shaping and illumination system of the lithography system.

The individual mirrors are each displaceable, in particular positionable, by means of an actuator device with a plurality of electromagnetically, in particular electrostatically operating, actuators. The actuators can be produced in a batch process as a micro-electro-mechanical system (MEMS). For details, see the document WO 2010/049 076 A1 whose content is referenced. To form the field facet mirror and to form the pupil facet mirror is on the DE 10 2013 209 442 A1 whose content is referenced.

In addition, a method for operating a lithography system comprising a radiation source for generating a radiation having a certain repetition frequency, an optical component for guiding the radiation in the lithography system, an actuator device for moving the optical component, a capacitive sensor, which comprises a number of has sensor electrodes connected to the optical component for measuring the position of a tilt angle of the optical component, and proposes an evaluation unit which is connected to the sensor electrodes via electrical lines and which is set up for the optical component and the sensor electrodes connected to the optical component with a Excite excitation signal and to receive and evaluate a resulting measurement signal, the evaluation unit having a switched capacitor read circuit and a switched capacitor common mode compensation circuit preceding the readout circuit, the compensation voltage and / or the compensation capacitance of the common capacitor Mode compensation circuit is set.

The embodiments and features described for the proposed device apply accordingly to the proposed method.

Furthermore, a computer program product is proposed which, on a program-controlled device, causes the operation of a lithography system of the method as explained above in such a way that the compensation voltage and / or the compensation capacitance of the common-mode compensation circuit is set.

A computer program product, such as a computer program means may, for example, be used as a storage medium, e.g. Memory card, USB stick, CD-ROM, DVD, or even in the form of a downloadable file provided by a server in a network or delivered. This can be done, for example, in a wireless communication network by transmitting a corresponding file with the computer program product or the computer program means.

Further possible implementations of the invention also include not explicitly mentioned combinations of features or embodiments described above or below with regard to the exemplary embodiments. The skilled person will also add individual aspects as improvements or additions to the respective basic form of the invention.

• 1 zeigt eine schematische Ansicht einer EUV-Lithographieanlage;
• 2 zeigt eine schematische Ansicht einer Ausführungsform eines Aspekts der EUV-Lithographieanlage;
• 3 zeigt ein erstes Ausführungsbeispiel eines vereinfachten Ersatzschaltbildes eines kapazitiven Sensors und den ersten Teil einer nachgeschalteten Auswerteeinheit des Aspekts der EUV-Lithographieanlage gemäß 2;
• 4 zeigt ein zweites Ausführungsbeispiel eines Ersatzschaltbildes eines kapazitiven Sensors und einer nachgeschalteten Auswerteeinheit des Aspekts der EUV-Lithographieanlage gemäß 2;
• 5 zeigt ein drittes Ausführungsbeispiel eines Ersatzschaltbildes eines kapazitiven Sensors und einer nachgeschalteten Auswerteeinheit des Aspekts der EUV-Lithographieanlage gemäß 2;
• 6 zeigt eine schematische Ansicht einer Ausführungsform einer Auswerteeinheit des Aspekts der EUV-Lithographieanlage gemäß 2; und
• 7 zeigt ein Beispiel eines Ersatzschaltbildes eines kapazitiven Sensors und einer nachgeschalteten Auswerteeinheit einer EUV-Lithographieanlage.

Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the embodiments of the invention described below. Furthermore, the invention will be explained in more detail by means of preferred embodiments with reference to the attached figures.

• 1 shows a schematic view of an EUV lithography system;
• 2 shows a schematic view of an embodiment of an aspect of the EUV lithography system;
• 3 shows a first embodiment of a simplified equivalent circuit diagram of a capacitive sensor and the first part of a downstream evaluation of the aspect of the EUV lithography system according to 2 ;
• 4 shows a second embodiment of an equivalent circuit diagram of a capacitive sensor and a downstream evaluation of the aspect of the EUV lithography system according to 2 ;
• 5 shows a third embodiment of an equivalent circuit diagram of a capacitive sensor and a downstream evaluation of the aspect of the EUV lithography system according to 2 ;
• 6 shows a schematic view of an embodiment of an evaluation of the aspect of the EUV lithography system according to 2 ; and
• 7 shows an example of an equivalent circuit diagram of a capacitive sensor and a downstream evaluation of an EUV lithography system.

In the figures, the same or functionally identical elements have been given the same reference numerals, unless stated otherwise. It should also be noted that the illustrations in the figures are not necessarily to scale.

1 shows a schematic view of an EUV lithography system 100 which is a beam shaping and illumination system 102 and a projection system 104 includes. EUV stands for "extreme ultraviolet" (English: extreme ultraviolet, EUV) and refers to a working light wavelength between 0.1 and 30 nm. The beam-forming and illumination system 102 and the projection system 104 are each provided in a vacuum housing, wherein each vacuum housing is evacuated by means of an evacuation device, not shown. The vacuum housings are surrounded by a machine room, not shown. In this engine room and electrical controls and the like can be provided.

The EUV lithography system 100 has an EUV radiation source or EUV light source 106A on. As an EUV light source 106A For example, a plasma source can be provided, which radiation 108A in the EUV range (extreme ultraviolet range), ie in the wavelength range from 5 nm to 30 nm, for example. In the beam-forming and lighting system 102 becomes the EUV radiation 108A bundled and the desired operating wavelength from the EUV radiation 108A filtered out. The from the EUV light source 106A generated EUV radiation 108A has a relatively low transmissivity through air, which is why the beam guiding spaces in the Beam shaping and lighting system 102 and in the projection system 104 are evacuated.

This in 1 illustrated beam shaping and illumination system 102 has five mirrors 110 . 112 . 114 . 116 . 118 on. After passing through the beam shaping and lighting system 102 becomes the EUV radiation 108A directed to the photomask (Engl .: reticle) 120. The photomask 120 is also designed as a reflective optical element and can be outside the systems 102 . 104 be arranged. Next, the EUV radiation 108A by means of a mirror 136 on the photomask 120 be steered. The photomask 120 has a structure which, by means of the projection system 104 reduced to a wafer 122 or the like is mapped.

The projection system 104 has six mirrors M1 - M6 for imaging the photomask 120 on the wafer 122 on. It can single mirror M1 - M6 of the projection system 104 symmetrical to the optical axis 124 of the projection system 104 be arranged. It should be noted that the number of mirrors of the EUV lithography system 100 is not limited to the number shown. It can also be provided more or less mirror. Furthermore, the mirrors M1 - M6 usually curved at its front for beam shaping.

2 shows a schematic view of a first embodiment of an aspect of the EUV lithography system 100 ,

It shows the 2 a mirror 200 as an optical component and a mirror 200 associated measuring device 230 , The mirror 200 may be formed as a single mirror or as a MEMS mirror and, for example, part of one of the mirrors 110 . 112 . 114 . 116 . 118 the beam-forming and lighting system 102 the EUV lithography system 100 of the 1 be. The individual mirror 200 of the 2 can also be part of another mirror M1 - M6 the EUV lithography system 100 of the 1 be.

Furthermore, the illustrated 2 that the mirror 200 over a suspension 210 with a base plate 220 connected is. The suspension 210 is part of an actuator device, not shown 210 to relocate the mirror 200 , Details for an example of such an actuator device 210 arise from the document DE 10 2013 442 A1 ,

The measuring device 230 is for determining a position of the mirror 200 by means of a measuring signal S2 set up with a certain measuring signal frequency. The measurement signal frequency is, for example, a sampling frequency. Here is the measuring device 230 preferably set up the mirror 200 and those with the mirror 200 connected sensor electrodes 231 - 236 with an excitation signal S3 to excite at a predetermined excitation frequency and then to sample at the sampling frequency. The excitation frequency is in particular equal to the sampling frequency. Alternatively, the sampling frequency may be higher than the excitation frequency. The measuring signal frequency is in particular unequal to the repetition frequency and unequal integer multiples of the repetition frequency. Thus, the measurement signal frequency is not equal to the repetition frequency of the EUV radiation source 106A and the frequencies of their harmonics. The measuring device 230 has a number of electrodes 231 - 236 on, which are comb-shaped and arranged toothed. This forms the measuring device 230 a capacitive sensor for detecting the position of a tilt angle of the mirror 200 out. The electrodes or sensor electrodes 231 - 236 are by means of electrical cables with an evaluation unit 237 connected. The evaluation unit 237 is set up the mirror 200 and those with the mirror 200 connected sensor electrodes 231 - 236 with the excitation signal S3 stimulate and the resulting measurement signal S2 to receive and evaluate.

In addition, the shows 2 the capacities C _CS1 . _CS3 . C _RS1 . C _LS3 , The capacity C _CS1 is the capacity between the electrodes 233 and 234 , The capacity C _RS1 is the capacity between the electrodes 231 and 233 , The capacity _CS3 is the capacity between the electrodes 235 and 236 , The capacity C _LS3 is the capacity between the electrodes 232 and 235 , The electrodes 231 . 233 and 234 form a comb-like first sensor device 241 , Accordingly, the electrodes form 232 . 235 and 236 a comb-like second sensor device 242 , The two sensor devices 241 and 242 in particular form the capacitive sensor for measuring the position of a tilt angle of the optical component 200 , Independent of each other can with each of the sensor devices 241 . 242 a change in position of the optical component 200 be recorded.

This shows the 3 a first embodiment of an equivalent circuit diagram 254 the capacitive sensor and a downstream evaluation 237 the aspect of the EUV lithography system according to 2 , This corresponds to the in the 3 shown equivalent circuit diagram 254 of the capacitive sensor in the 7 shown equivalent circuit diagram 254 of the capacitive sensor.

The evaluation unit 237 of the 3 includes a readout circuit 238 and one of the readout circuits 238 upstream common mode compensation circuit 239 , The common mode compensation circuit 239 acts as a compensation circuit to compensate for the DC component of the measurement signal S2 ,

The readout circuit 238 based on switched capacitors Ci. The capacitors Ci are switched by means of the switches S ₃ , S ₄ . In this case, the readout circuit includes 238 a transconductance amplifier 240 (OTA, Operational Transconductance Amplifier). This is the basis of the readout circuit 240 on the SC technique (SC, Switched Capacitor). The integration capacitances Ci are reset by means of the switches S ₃ and S ₄ . After the switches S ₃ , S ₄ are opened again, a jump is applied to V _ex . Thus, the corresponds in the 3 shown readout circuit 238 the Indian 7 shown readout circuit 271 ,

In comparison to 7 includes the common mode compensation circuit 239 of the 3 switched capacitors 251 in which the compensation voltage V _{CMcomp is} adjustable. An alternative to this shows the 4 in which in the common-mode compensation circuit 239 the compensation capacitance C _{CM is} adjustable. In another alternative, not shown, are in the two switched capacitors 251 . 252 the common-mode compensation circuit 239 both parameters, namely the compensation voltage V _CM-comp and the compensation capacitance C _CMcomp , adjustable. Due to the adjustability of the compensation voltage V _CMcomp and / or the compensation capacitance C _CMcomp , the present common-mode compensation circuit 239 satisfy Equation (6) below, without the CO in the main path - as in the case of high DC to be compensated CO 7 - would be increased. This is the performance of the entire stage compared to the example of 7 clearly increased. $${\text{V}}_{\text{ex}}\cdot {\text{C0 = V}}_{\text{CMcomp}}\cdot {\text{C}}_{\text{CMcomp}}$$

In particular, the common mode compensation circuit 239 of the 3 the ICMFB level 272 of the 7 replace. This replacement allows the power consumption and the space consumption of the evaluation unit 237 be reduced by up to 30%, especially since the common-mode compensation circuit 237 On the basis of the SC technique (SC, Switched Capacitor) requires very little space. As already stated above, the parasitic input capacitance can be significantly reduced by suitably selecting V _CMcomp and C _CMcomp (see equation (6) above). This significantly reduces the noise requirements of the main readout branch and thus also the power and area can be additionally saved there. The numerical example below from an implemented application can clarify this. $${\text{C}}_{\text{p1}}=~2\text{pF}{\text{, C}}_{\text{fb}}=500\text{fF}{\text{, C}}_{\text{CMcomp}}=50\text{fF}$$

This results in a reduction of the input capacity by 450 fF, which corresponds to a share of 18%.

Another alternative to those in the 3 and 4 shown embodiments of the common mode compensation circuit 239 is in the 5 shown. According to the 5 includes the common mode compensation circuit 239 in addition to the switched capacitors 251 and 252 as in the 3 and 4 shown an input common mode feedback stage 255 , which is also called ICMFB level 255 can be designated. The switched capacitors 251 . 252 are set up for coarse compensation of the DC component of the measurement signal, whereas the ICMFB stage 255 is set up for fine compensation of the DC component of the measurement signal. In other words, the DC component becomes coarse and in particular static via the SC technique of the switched capacitors 251 . 252 and thereafter, a more accurate and dynamic compensation of the remaining perturbations occurs via the ICMFB stage 255 ,

Advantageously, in the common-mode compensation circuit 239 of the 5 not necessary that the values for the respective excitation voltages, the offset component C0 and the compensation capacitance C _{CMcomp are} exactly or exactly set, since the ICMFB stage 255 a potential remaining error after compensation by the switched capacitors 251 . 252 corrects. Another advantage is that the SC technology according to the capacitors 251 and 252 In this case, it can be set up very simply because no tuning is required. It is sufficient if the respective values are coarse. Dependencies, eg. As of the temperature or the lifetime, these sizes are just as unproblematic within certain limits, especially with a variation up to about 20%. Furthermore, the requirements for the ICMFB level 255 the common-mode compensation circuit 239 of the 5 in comparison to the circuit according to 7 significantly reduced. The necessary modulation range of the transconductance amplifier of the ICMFB stage 255 can be reduced by a factor of 10, for example. This allows the transconductance amplifier of the ICMFB stage 255 be implemented more efficiently, so that the area consumption and power consumption are reduced with the same performance of the evaluation. Further, depending on the implementation, the sum of all input capacitances can also be reduced and thus the input-related noise of the entire readout circuit can be reduced.

Furthermore, in the 6 a schematic view of an embodiment of an evaluation unit 237 the aspect of the EUV lithography system according to 2 shown.

The evaluation unit 237 of the 6 includes an evaluation circuit 238 and one of the evaluation circuit 238 upstream common mode compensation circuit 239 , Examples of such arrangements are in the 3 to 5 shown. Furthermore, the evaluation unit comprises 237 of the 6 a synchronization unit 256 and a calibration unit 257 ,

The synchronization unit 256 is _adapted to the compensation voltage V _CMcomp synchronous and out of phase with the excitation _signal V _ex to switch. The calibration unit 257 is configured to calibrate the compensation capacitance C _CMcomp to compensate for drifting common mode _noise .

Although the present invention has been described with reference to embodiments, it is variously modifiable.

LIST OF REFERENCE NUMBERS

100

lithography system

100A

EUV lithography system

102

Beam shaping and lighting system

104

projection system

106A

Radiation source, EUV light source

108A

EUV radiation

110

mirror

112

mirror

114

mirror

116

mirror

118

mirror

120

photomask

122

wafer

124

optical axis of the projection system

136

mirror

M1-M6

mirror

137

Vacuum housing

200

mirror

210

Actuator device, in particular suspension

220

baseplate

230

Capacitive sensor, measuring device

231

electrode

232

electrode

233

electrode

234

electrode

235

electrode

236

electrode

237

evaluation

238

evaluation

239

Common mode compensation circuit

240

transconductance amplifier

241

sensor device

242

sensor device

251

switched capacitor

252

switched capacitor

254

Equivalent circuit diagram for capacitive sensor

255

Input common mode feedback stage (ICMFB stage)

256

synchronization unit

257

calibration unit

263

management

264

management

270

evaluation

271

readout circuit

272

ICMFB stage

273

transconductance amplifier

274

transconductance amplifier

C _fb

Capacity of the ICMFB stage

C _{CM comp}

Compensation capacity

CCSI

Capacitance between electrode 233 and electrode 234

_CS3

Capacitance between electrode 235 and electrode 236

C _h

parasitic line capacitance

C _i

switched capacity

C _LS3

Capacitance between electrode 232 and electrode 235

C _p1

parasitic line capacitance

C _p2

parasitic line capacitance

C _RS1

Capacitance between electrode 231 and electrode 233

R _p1

parasitic line resistance

R _p2

parasitic line resistance

S1

E UV radiation

S2

measuring signal

S3

excitation signal

S ₃

switch

S ₄

switch

VCM

supply voltage

V _{CM comp}

Compensating voltage

V _ex

excitation signal

V _out

output voltage

V _ss

reference potential

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2009/100856 A1 [0006]
• DE 102013209442 A1 [0007, 0043]
• WO 2017/005849 A1 [0008, 0010]
• WO 2010/049076 A1 [0043]
• DE 102013442 A1 [0057]

Claims (14)

A lithographic apparatus (100), comprising: a radiation source (106A) for generating radiation at a given repetition frequency, an optical component (200) for guiding the radiation in the lithography apparatus (100), an actuator device (210) for displacing the optical component (200), a capacitive sensor (230) having a number of sensor electrodes (231-236) connected to the optical component (200) for measuring the position of a tilt angle of the optical component (200), one via electrical leads the evaluation unit (237) which is connected to the sensor electrodes (231-236) and is adapted to connect the optical component (200) and the sensor electrodes (231-236) connected to the optical component (200) with an excitation signal (S3, V _ex ) and to receive and evaluate a resulting measurement signal (S2), wherein the evaluation unit (237) comprises: a switched-capacitor read circuit (238), and one of the A A common-mode compensation circuit (239) with switched capacitors (251, 252) upstream of the read-out circuit (238), in which the compensation voltage (V _CMcomp ) and / or the compensation capacitance (C _CMcomp ) can be set. Lithography plant according to Claim 1 wherein the readout circuit (238) is formed as a fully differential switched capacitance readout circuit having a transconductance amplifier (240). Lithography plant according to Claim 1 or 2 comprising: a synchronization unit (256) arranged to switch the compensation voltage (V _CMcomp ) synchronously and in _anti- phase with the excitation _signal (V _ex ). Lithography plant according to one of Claims 1 to 3 , comprising: a calibration unit (257) arranged to calibrate the compensation capacitance (C _CMcomp ) to compensate for drifting common mode _noise . Lithography plant according to one of Claims 1 to 4 , wherein the sensor electrodes (231 - 236) of the capacitive sensor (230) are comb-shaped and arranged toothed. Lithography plant according to Claim 5 wherein the capacitive sensor (230) comprises a comb-like first sensor device (241) with a number of sensor electrodes (231, 233, 234) and a comb-like second sensor device (242) with a number of sensor electrodes (232, 235, 236 ), wherein each of the sensor devices (241, 242) is coupled to the evaluation unit (237) via an electrical line (263, 264) for transmitting the respective measurement signal. Lithography plant according to one of Claims 1 to 6 wherein the common mode compensation circuit (239) has an input common mode feedback stage (255) in addition to the switched capacitors (251, 252). Lithography plant according to Claim 7 wherein the switched capacitors (251, 252) are arranged for coarse compensation of the DC component of the measurement signal and the input common mode feedback stage (255) is set up for fine compensation of the DC component of the measurement signal. Lithography plant according to Claim 8 in which the evaluation unit (237) is set up to excite the optical component (200) and the sensor electrodes (231-236) connected to the optical component (200) with the excitation signal (S3) at a predetermined excitation frequency and then with a Sampling frequency, wherein the excitation frequency is equal to the sampling frequency. Lithography plant according to one of Claims 1 to 9 wherein the radiation source (106A) is an EUV radiation source configured to generate EUV radiation at the predetermined repetition frequency. Lithography plant according to one of Claims 1 to 10 wherein the optical component (200) is a mirror. Lithography plant according to one of Claims 1 to 11 wherein the optical component (200) is a single mirror of a field facet mirror of a beamforming and illumination system (102) of the lithography system (100). Lithography plant according to one of Claims 1 to 12 wherein the optical component (200) is a single mirror of a pupil facet mirror of a beamforming and illumination system (102) of the lithography system (100). A method for operating a lithography system (100) comprising a radiation source (106A) for generating a radiation having a specific repetition frequency, an optical component (200) for guiding the radiation in the lithography system (100), an actuator device (210) for displacing the optical component (200), a capacitive sensor (230) having a number of sensor electrodes (231-236) connected to the optical component (200) for measuring the position of a tilt angle of the optical component (200), and one via electrical leads to the sensor electrodes (231 - 236) connected evaluation unit (237), which is adapted to the optical component (200) and the optical component (200) connected to the sensor electrodes (231 - 236) with an excitation signal (S3) to excite and a receiving resultant measurement signal (S2) and evaluated, with the evaluation unit (237) a readout circuit (238) switched-capacitor (C _i) and one of the read-out circuit (238) upstream common mode compensation circuit (239) switched-capacitor circuit (251, 252), wherein the compensation voltage (V _CMcomp ) and / or the compensation capacitance (C _CMcomp ) of the common mode compensation circuit (239) is set.

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