Lithography apparatus and method for operating the lithography apparatus

Abstract

The present invention relates to a lithography apparatus (1), comprising a radiation source (3) that generates radiation (S) having a specific repetition frequency, and a MEMS mirror (30) that guides the radiation (S) within the lithography apparatus (1), which is displaceable at an inclination angle (W) on at least two inclination axes (A1, A2), and a capacitance sensor (35) having a plurality of electrodes (36, 37) for acquiring the inclination angle (W), and each measurement signal (I S1 ~I S4 Four sensor units (41-44) are provided for each tilt axis (A1, A2) for the purpose of obtaining the following: The first pair of the four sensor units (41-44) (41, 43) excites the capacitance sensor (35) with the first excitation signal (V1) and in response each measurement signal (I S1 , I S3 The system is configured to receive the following: the second pair (42, 44) of the four sensor units (41-44) excites the capacitance sensor (35) with the second excitation signal (V2) and responds to each measurement signal (I S2 , I S4 A MEMS mirror (30) is configured to receive the first excitation signal (V1) and the second excitation signal (V2), which have opposite polarities, and the measurement signals (I) of four sensor units (41-44). S1 ~I S4 The present invention relates to a lithography apparatus comprising an evaluation unit (50) configured to determine the position (P) of a MEMS mirror (30) by ).

Description

[Technical Field]

[0001] The present invention relates to a lithography apparatus and a method for operating a lithography apparatus.

[0002] The entire contents of the priority application, German Patent Application No. 10 2023 203 339.9, are incorporated by reference. [Background technology]

[0003] Microlithography is used, for example, in the manufacturing of microstructured components such as integrated circuits. The microlithography process is performed using a lithography apparatus equipped with an illumination system and a projection system. The image of a mask (reticle) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, which is coated with a photosensitive layer (photoresist) and placed on the image plane of the projection system, thereby transferring the mask structure to the photosensitive coating of the substrate.

[0004] The need for further miniaturization of structures in integrated circuit manufacturing is driving the development of EUV lithography equipment that uses light in the 0.1 nm to 30 nm range, particularly at a wavelength of 13.5 nm. Since most materials absorb light at this wavelength, such EUV lithography equipment requires the use of reflective optical units, i.e., mirrors, instead of the refractive optical units, i.e., lens elements, that have been used in the past.

[0005] It is known that lithography equipment uses what are called MEMS mirrors in its illumination systems. "MEMS" stands for Micro-Electro-Mechanical Systems. Such MEMS mirrors consist of a so-called micromirror (also called a mirror plate) and an actuator. The actuator allows for changes in the alignment of the micromirror. When the lithography equipment is in operation, radiation (working light, also called EUV light) is incident on the surface of the micromirror and reflected there. By changing the alignment of the micromirror, the path of the EUV light in the illumination system can be affected. Such MEMS mirrors are generally manufactured integrally on a substrate. An advantage is that such systems require only a small installation space. On the other hand, there are often significant constraints on the installation space of electronic components behind the MEMS mirror, i.e., in the area opposite to the working light.

[0006] The micromirrors can be configured to be fixed to a carrier plate and at least partially operable or tiltable, for example, to allow each micromirror to move in up to six degrees of freedom, and thus enable very precise positioning of the micromirrors relative to each other, particularly in the pm range. This allows for compensation of changes in optical properties that occur, for example, when the lithography apparatus is in operation as a result of thermal effects.

[0007] To specifically displace the micromirrors with six degrees of freedom, actuators operated by a control loop are assigned to the micromirrors. A device that monitors the tilt angle of each mirror is provided as part of the control loop.

[0008] For example, Patent Document 1 discloses a faceted mirror for projection exposure apparatus in a lithography system, which has multiple individually displaceable individual mirrors. To ensure the optical quality of the projection exposure apparatus, extremely precise positioning of the displaceable individual mirrors is necessary. Furthermore, Patent Document 2 describes that a field-view faceted mirror can be implemented as a micro-electromechanical system (MEMS).

[0009] However, photons from the EUV radiation source of the lithography apparatus can induce electron emission from the mirror surface of the MEMS mirror as a result of the photoelectric effect. This can cause a temporally and spatially variable current flow across the MEMS mirror of the field-of-view facet mirror. These temporally and spatially variable current flows across the MEMS mirror can significantly interfere with monitoring the tilt angle of each mirror. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] International Publication No. 2009 / 100856 [Patent Document 2] German Patent Application Publication No. 10 2013 209 442 Specification [Overview of the project] [Problems that the invention aims to solve]

[0011] In view of this, the object of the present invention is to provide an improved lithography apparatus. [Means for solving the problem]

[0012] According to the first embodiment, a lithography apparatus is proposed. This lithography apparatus comprises a radiation source that generates radiation having a specific repetition frequency, a MEMS mirror that guides radiation within the lithography apparatus and is displaceable at an inclination angle on at least two inclination axes, a capacitive sensor having multiple electrodes for acquiring the inclination angle, four sensor units provided for each inclination angle for the purpose of acquiring each measurement signal from the capacitive sensor, a first pair of the four sensor units configured to excite the capacitive sensor with a first excitation signal and receive each measurement signal in response, a second pair of the four sensor units configured to excite the capacitive sensor with a second excitation signal and receive each measurement signal in response, the first and second excitation signals having opposite polarities, a MEMS mirror, and an evaluation unit configured to determine the position of the MEMS mirror based on the measurement signals from the four sensor units.

[0013] The first and second excitation signals have opposite polarities, and in this case, different signs, but identical amplitudes. Despite the two sensor unit pairs being excited by excitation signals with opposite polarities, the disturbance generated by radiation incident on the MEMS mirror at the output of the first sensor unit has the same sign as the disturbance generated by radiation incident on the MEMS mirror at the output of the second sensor unit pair. The sign of the disturbance remains unchanged as a result of the different signs of the excitation signals. By subtracting the two identical disturbances in a downstream processing stage, these disturbances can be taken into account by the evaluation unit when determining the position of the MEMS mirror so that they cancel each other out.

[0014] Because the excitation signals of the first and second pairs of the four sensor units have different codes, the two effective output signals also have different codes.

[0015] The downstream subtraction step processes the sum of both active signals. In particular, if the evaluation unit is a differential evaluation unit, the output signals of the first sensor unit pair are subtracted from the output signals of the second sensor unit pair, resulting in disturbances with different signs canceling each other out.

[0016] Therefore, the influence of disturbances generated by electrons ejected onto the mirror plate by radiation from the radiation source on the determination of the mirror plate's tilt angle is significantly reduced. This reduction in disturbances allows for much more precise determination of the mirror's position. This more precise determination of the mirror's position significantly improves the control loop that controls the micromirror actuator (also called the control unit).

[0017] The first pair of sensor units and the second pair of sensor units have, in particular, disparate sets of sensor units.

[0018] The lithography apparatus or projection exposure apparatus may be an EUV lithography apparatus. EUV stands for "extreme ultraviolet" and refers to the wavelength of the operating light between 0.1 nm and 30 nm. The lithography apparatus or projection exposure apparatus may also be a DUV lithography apparatus. DUV stands for "deep ultraviolet" and refers to the wavelength of the operating light between 30 nm and 250 nm. The radiation guided may be EUV light or DUV light.

[0019] According to one embodiment, the evaluation unit is embodied as a differential evaluation unit. The differential evaluation unit is configured, in particular, to subtract the output signals of a first pair of sensor units from the output signals of a second pair of sensor units, so that disturbances having the same sign in the outputs of the pairs of sensor units cancel each other out.

[0020] In yet another embodiment, the evaluation unit is: First pair of measurement signals I from the sensor unit S1 , I S3 The received measurement signal I S1 , I S3 A first converter configured to supply a first voltage signal U1 on the output side that is proportional to the difference between the two, The second pair of measurement signals I from the sensor unit S2 , I S4 The received measurement signal I S2 , I S4A second converter configured to supply, on an output side, a second voltage signal U2 proportional to a difference therebetween A subtractor configured to subtract the second voltage signal U2 from the first voltage signal U1 and, accordingly, output, on an output side, a differential signal U D and includes

[0021] According to yet another embodiment, the first converter is embodied as a first capacitance-voltage converter. The first capacitance-voltage converter obtains, at an input connected to a first sensor unit, a first current I AS1 corresponding to a sum of a current I SS1 generated at an output of the first sensor unit by excitation of a capacitance sensor with a first excitation signal V1 and a current I S1 (I S1 =I AS1 +I SS1 ) generated at the output of the first sensor unit by disturbance generated by radiation in the MEMS mirror, and obtains, at an input connected to a third sensor unit, a third current I AS3 corresponding to a sum of a current I SS3 generated at an output of the third sensor unit by excitation of a capacitance sensor with the first excitation signal V1 and a current I S3 (I S3 =I AS3 +I SS3 ) generated at the output of the third sensor unit by disturbance generated by radiation in the MEMS mirror, and is configured to obtain the first voltage signal U1 according to Equation

Equation

[0022] In this case, C INT represents the capacitance of the first capacitance-voltage converter. In the symbol I AS1 , I represents current, A represents excitation, and S1 represents the first sensor unit among four sensor units. In the symbol I SS1 , I represents current, S represents disturbance voltage V SThis indicates the disturbance generated by, and S1 indicates the first sensor unit. Symbol I AS3 In this diagram, I represents current, A represents excitation, and S3 represents the third sensor unit out of four sensor units. Symbol I SS3 In this equation, I represents the current and S represents the disturbance voltage V. S The disturbance generated is shown, and S3 indicates the third sensor unit. Disturbance voltage V S This occurs on the mirror surface of a MEMS mirror when incident radiation knocks electrons out of the mirror surface. (Disturbance voltage V) S This generates the aforementioned disturbances at each outlet of the sensor unit.

[0023] current I S1 , I S3 If we consider electric charge instead, equation (1) above can also be expressed as equation (2).

number

[0024] In this case, Q S1 Q represents the charge supplied at the output of the first sensor unit S1 by excitation with the first excitation signal V1. S3 This indicates the charge supplied at the output of the third sensor unit S3 by excitation with the first excitation signal V1, and Q SS1 The disturbance voltage V S This indicates the charge supplied by the output of the first sensor unit S1, and Q SS3 The disturbance voltage V S This indicates the charge supplied by the output of the third sensor unit S3 as a result.

[0025] In yet another embodiment, the second converter is embodied as a second capacitance-voltage converter. The second capacitance-voltage converter is an input connected to the second sensor unit, and generates a current I at the output of the second sensor unit due to the excitation of the capacitance sensor with the second excitation signal V2. AS2 The current I generated at the output of the second sensor unit due to disturbances caused by radiation in the MEMS mirror SS2 The second current I corresponds to the sum of the two currents. S2 (IS2 =I AS2 +I SS2 The input connected to the fourth sensor unit is configured to obtain a current I generated at the output of the fourth sensor unit due to the excitation of the capacitive sensor with the second excitation signal V2. AS4 The current I generated at the output of the fourth sensor unit due to disturbances caused by radiation in the MEMS mirror SS4 The fourth current I corresponds to the sum of the above. S4 (I S4 =I AS4 +I SS4 It is configured to obtain the formula

number

[0026] In this case, C INT This indicates the capacitance of the second capacitance-voltage converter. Symbol I AS2 In this diagram, I represents current, A represents excitation, and S2 represents the second sensor unit out of the four sensor units. Symbol I SS2 In this equation, I represents the current and S represents the disturbance voltage V. S This indicates the disturbance generated by [the first element], and S2 indicates the second sensor unit. Symbol I AS4 In this diagram, I represents current, A represents excitation, and S4 represents the fourth sensor unit out of four sensor units. Symbol I SS4 In this equation, I represents the current and S represents the disturbance voltage V. S This indicates the disturbance generated by the system, and S4 indicates the fourth sensor unit.

[0027] current I S2 , I S4 If we consider electric charge instead, equation (3) above can also be expressed as equation (4).

number

[0028] The subtractor subtracts the second voltage signal U2 from the first voltage signal U1, and outputs a difference signal U accordingly.D It was configured to output. U D =U1-U2(5)

[0029] The disturbances generated by incident radiation in mutually adjacent sensor units S1 to S4 (i.e., each disturbance voltage V) S Assuming that ) are the same or nearly the same, charge Q SS1 Q SS2 Q SS3 , and Q SS4 They are identical or nearly identical. In that case, U D This can be calculated as follows using equation (6):

number

[0030] As shown in equation (6), the difference signal U D is the disturbance voltage V S The signal component resulting from this, and therefore Q SS1 Q SS2 Q SS3 , and Q SS4 It does not include the difference signal U. In that case, the evaluation unit will use the difference signal U. D This allows for very precise determination of the position of the MEMS mirror.

[0031] In yet another embodiment, a first A / D converter (analog-to-digital converter) and a first weighting unit are connected downstream of the first converter. In this case, the first A / D converter is configured to convert a first voltage signal supplied by the first converter into a digital first voltage signal. The first weighting unit is configured to weight the digital first voltage signal by the actual tilt angle of the MEMS mirror measured by a measurement unit in order to output a weighted first voltage signal. Furthermore, a second A / D converter and a second weighting unit are connected downstream of the second converter. In this case, the second A / D converter is configured to convert a second voltage signal supplied by the second converter into a digital second voltage signal. The second weighting unit is configured to weight the digital second voltage signal by the actual tilt angle of the MEMS mirror measured by a measurement unit in order to output a weighted second voltage signal. In this case, the subtractor is configured to subtract the weighted second voltage signal from the weighted first voltage signal and output a difference signal on the output side accordingly.

[0032] The first A / D converter converts the first voltage signal into a digital first voltage signal. The first weighting unit weights the digital first voltage signal by the measured actual tilt angle of the MEMS mirror. Various MEMS mirrors in the micromirror array may have slight deviations in their tilt angles. In this regard, a measurement unit is provided to measure the actual tilt angle of each MEMS mirror. Preferably, the measurement unit includes a laser for measuring the actual tilt angle of the MEMS mirror. The use of the first weighting unit makes it possible to account for such tolerances. The second A / D converter and the second weighting unit operate in correspondence. The second A / D converter converts the second voltage signal into a digital second voltage signal, and the second weighting unit weights this digital second voltage signal by the measured actual tilt angle. This individual adjustment allows tolerances to be accounted for, further improving the suppression of EUV disturbances.

[0033] In yet another embodiment, the first and second transducers each include a trimmable capacitor. Furthermore, the lithography apparatus has a calibration unit configured to trim each trimmable capacitor by the actual tilt angle of the MEMS mirror measured by the measurement unit.

[0034] By trimming the trimmable capacitors of the first and second transducers according to the measured actual tilt angle of the MEMS mirror, tolerances can be individually adjusted, further improving the suppression of EUV disturbances.

[0035] In yet another embodiment, the MEMS mirror includes a mirror plate that is displaceable at an inclination angle, a carrier plate that supports the mirror plate, a base plate, a flexure that connects the base plate and the carrier plate and functions to tilt the mirror plate, and a capacitance sensor.

[0036] Individual plates are manufactured, in particular, from polysilicon. Doping creates electrodes that act as conductive elements. Mirror plates are obtained by coating polysilicon with an EUV reflective material. Shielding plates can be manufactured from two plates of doped or undoped polysilicon, or by metallizing an undoped plate.

[0037] In yet another embodiment, the capacitance sensor has an upper electrode positioned in the direction of the mirror plate and a lower electrode positioned in the direction of the base plate in order to measure the tilt angle of the mirror plate of the MEMS mirror.

[0038] In yet another embodiment, the electrodes of the capacitance sensor are realized in a comb shape and arranged to interlock.

[0039] In yet another embodiment, each comb-shaped electrode of the capacitance sensor has a notch through which a flexure that connects the carrier plate and the base plate passes. In particular, the flexure passes through two notches in the comb-shaped electrodes of the capacitance sensor, thereby connecting the carrier plate and the base plate of the MEMS mirror. The mirror plate of the MEMS mirror can be tilted at an angle by the flexure.

[0040] In yet another embodiment, the mirror plate is connected to ground via a first resistor, and the upper electrode of the capacitance sensor is connected to ground via a second resistor.

[0041] As described above, the MEMS mirror is displaceable on at least two tilt axes, preferably two mutually orthogonal tilt axes. In this case, at least two control units are provided for each tilt axis to actuate the mirror plate for the purpose of displacing the mirror plate.

[0042] In yet another embodiment, the lithography apparatus includes a voltmeter for measuring the voltage drop between the mirror plate and the base plate. In this case, the evaluation unit is configured to determine the position of the MEMS mirror based on the measurement signals supplied by the four sensor units and the measured voltage.

[0043] In yet another embodiment, the lithography apparatus comprises a micromirror array having a plurality of MEMS mirrors. Preferably, the micromirror array is part of the illumination system of the lithography apparatus.

[0044] In yet another embodiment, the lithography apparatus comprises a vacuum housing in which a radiation source, a MEMS mirror, a sensor unit, and an evaluation unit are arranged. For example, the vacuum housing has an internal pressure of 10¹³.25 hPa~10 -3 hPa, preferably 10 -3 hPa~10 -8 hPa, more 10 -8 hPa~10 -11 It is designed to be in hPa.

[0045] In yet another embodiment, the lithography apparatus includes a control device located outside the vacuum housing that controls the radiation source by a control signal.

[0046] In yet another embodiment, the MEMS mirror, sensor unit, and evaluation unit are arranged in the illumination system of the lithography apparatus.

[0047] In yet another embodiment, the radiation source is an EUV radiation source.

[0048] Each unit, for example, a control unit, can be implemented in hardware and / or software. In hardware implementation, a unit can be embodied as a device or as part of a device, for example, as a computer, a microprocessor, or as part of a control device. In software implementation, a unit can be embodied as a computer program product, as a function, as a routine, as part of program code, or as an executable object.

[0049] According to a second embodiment, a method for operating a lithography apparatus is proposed, the lithography apparatus comprising a radiation source that generates radiation having a specific repetition frequency, and a MEMS mirror that guides radiation within the lithography apparatus and is displaceable at an inclination angle on at least two inclination axes, and includes a capacitive sensor having multiple electrodes for acquiring the inclination angle, with four sensor units provided for each inclination axis for acquiring each measurement signal from the capacitive sensor. This method, The first pair of four sensor units excites the capacitance sensor with the first excitation signal V1, and in response, each sensor unit of the first pair generates its respective measurement signal I S1 , I S3 The steps to receive, The second pair of the four sensor units excites the capacitive sensor with the second excitation signal V2, and in response, each sensor unit of the second pair generates the respective measurement signal IS2 , I S4 The step involves receiving the second excitation signal V2, which has the opposite polarity to the first excitation signal V1. Measurement signals I from the four sensor units S1 ~I S4 The steps include determining the position of the MEMS mirror and Includes.

[0050] The embodiments described for the lithography apparatus according to the proposed first embodiment shall apply mutatis mutandis to the method according to the proposed second embodiment. Furthermore, the definitions and descriptions of the lithography apparatus shall also apply mutatis mutandis to the method proposed.

[0051] In this context, "a" or "an" should not necessarily be understood as strictly limited to a single element. Instead, multiple elements, such as two, three, or more, may be included. Any other numbers used here should not be understood as strictly limited to the number of elements listed. Rather, unless otherwise specified, the numerical values ​​can be increased or decreased.

[0052] Further possible embodiments of the present invention include combinations of features or embodiments described above or below with respect to exemplary embodiments that are not explicitly mentioned. Those skilled in the art will also add individual aspects as improvements or supplements to each basic form of the present invention.

[0053] Further advantageous configurations and aspects of the present invention are the subject of the dependent claims and the exemplary embodiments of the present invention described below. The present invention will be described in more detail below based on preferred embodiments with reference to the accompanying drawings. [Brief explanation of the drawing]

[0054] [Figure 1] This shows a schematic meridian cross-section of a projection exposure apparatus for EUV projection lithography. [Figure 2] A schematic diagram of one embodiment of a lithography apparatus is shown. [Figure 3]Figure 2 shows a schematic cross-sectional view of one embodiment of the sensor unit of the lithography apparatus shown. [Figure 4] Figure 2 shows a schematic diagram of one embodiment of an acquisition unit and an evaluation unit having a sensor unit in the lithography apparatus shown. [Figure 5] Figure 2 shows a schematic diagram of yet another embodiment of the acquisition unit and evaluation unit having a sensor unit of the lithography apparatus shown. [Figure 6] Figure 2 shows a schematic diagram of yet another embodiment of the acquisition unit and evaluation unit having a sensor unit of the lithography apparatus shown. [Figure 7] An example of an excitation signal used to excite a capacitance sensor in a lithography apparatus is shown. [Figure 8] This shows an example of a disturbance voltage generated by electrons knocked onto a mirror plate by radiation from a radiation source. [Figure 9] Figure 6 shows an example of the difference signal output by the evaluation unit. [Figure 10] Figure 5 shows an example of the difference signal after low-pass filtering, output by the low-pass filter shown. [Figure 11] This document illustrates one embodiment of a method for operating a lithography apparatus. [Modes for carrying out the invention]

[0055] Unless otherwise specified, identical or functionally identical elements are given the same reference numeral in the figures. Furthermore, it should be noted that the figures are not necessarily drawn to a fixed scale.

[0056] Figure 1 shows one embodiment of a projection exposure apparatus 1 (lithography apparatus), particularly an EUV lithography apparatus. One embodiment of the illumination system 2 of the projection exposure apparatus 1 includes, in addition to a light source or radiation source 3, an illumination optical unit 4 that illuminates the object field of view 5 on the object surface 6. In an alternative embodiment, the light source 3 may be provided as a module separate from the rest of the illumination system 2. In this case, the illumination system 2 does not include the light source 3.

[0057] A reticle 7 positioned in the object field of view 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 is displaceable, particularly in the scanning direction, by a reticle displacement drive 9.

[0058] Figure 1 shows a Cartesian coordinate system with x, y, and z directions for illustrative purposes. The x direction extends perpendicular to the plane of the figure. The y direction extends horizontally, and the z direction extends vertically. In Figure 1, the scanning direction extends along the y direction. The z direction extends perpendicular to the object plane 6.

[0059] The projection exposure apparatus 1 includes a projection optical unit 10. The projection optical unit 10 functions to form an image of the object field of view 5 onto the image field of view 11 of the image plane 12. The image plane 12 extends parallel to the object surface 6. Alternatively, angles other than 0° are possible between the object surface 6 and the image plane 12.

[0060] The structure on the reticle 7 is imaged onto the photosensitive layer of the wafer 13, which is positioned in the image field 11 region of the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is displaceable by a wafer displacement drive 15, particularly along the y-direction y. Firstly, the displacement of the reticle 7 by the reticle displacement drive 9 and secondly, the displacement of the wafer 13 by the wafer displacement drive 15 can be synchronized with each other.

[0061] Light source 3 is an EUV radiation source. Light source 3 specifically emits EUV radiation 16, which will be referred to below as the radiation used, illumination radiation, or illumination light. The radiation used 16 has wavelengths in the range of 5 nm to 30 nm. Light source 3 may be a plasma source, such as an LPP (Laser-Generated Plasma) source or a DPP (Gas Discharge Plasma) source. It may also be a synchrotron-based radiation source. Light source 3 may be an FEL (Free Electron Laser).

[0062] Illumination radiation 16 emitted from light source 3 is focused by collector 17. Collector 17 may be a collector having one or more elliptical and / or hyperbolic reflecting surfaces. Illumination radiation 16 may be incident on at least one reflecting surface of collector 17 at an oblique angle (GI), i.e., at an incident angle greater than 45°, or at a normal angle (NI), i.e., at an incident angle less than 45°. Collector 17 may be structured and / or coated to first optimize reflectivity for the radiation used, and second to suppress external light.

[0063] Downstream of the collector 17, the illumination radiation 16 propagates through the intermediate focal point of the intermediate focal plane 18. The intermediate focal plane 18 may represent the separation between the radiation source module, which includes the light source 3 and the collector 17, and the illumination optical unit 4.

[0064] The illumination optical unit 4 includes a deflection mirror 19 and a first facet mirror 20 positioned downstream of it in the beam path. The deflection mirror 19 may be a planar deflection mirror or a mirror having a beam influence effect beyond a pure deflection effect. Alternatively or additionally, the deflection mirror 19 may be embodied as a spectral filter that separates the wavelength of light used by the illumination radiation 16 from external light of wavelengths deviating from it. When the first facet mirror 20 is positioned on the plane of the illumination optical unit 4 that is optically conjugate to the object plane 6 as a field of view, this facet mirror is also referred to as a field of view facet mirror. The first facet mirror 20 includes a plurality of individual first facets 21, which may also be referred to as field of view facets. Only some of these first facets 21 are shown as examples in Figure 1.

[0065] The first facet 21 can be embodied as a macroscopic facet, particularly as a rectangular facet, or as a facet having an arc-shaped or partial-circular periphery. The first facet 21 can be embodied as a planar facet, or as a convex or concave curved facet.

[0066] For example, as is known from German Patent Application Publication No. 10 2008 009 600, the first facet 21 itself can also be composed of multiple individual mirrors, particularly multiple micromirrors. The first facet mirror 20 can take the form of a micro-electromechanical system (MEMS system). See German Patent Application Publication No. 10 2008 009 600 for further details.

[0067] The illumination radiation 16 travels horizontally, i.e., in the y-direction y, between the collector 17 and the deflection mirror 19.

[0068] In the beam path of the illumination optical unit 4, a second facet mirror 22 is positioned downstream of the first facet mirror 20. When the second facet mirror 22 is positioned on the pupil plane of the illumination optical unit 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be positioned away from the pupil plane of the illumination optical unit 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from U.S. Patent Application Publication No. 2006 / 0132747, European Patent No. 1614008, and U.S. Patent No. 6,573,978.

[0069] The second facet mirror 22 includes multiple second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0070] The second facet 23 may similarly be a macroscopic facet having, for example, a circular, rectangular, or hexagonal boundary, or a facet composed of micromirrors. For further details on this point, please refer to German Patent Application Publication No. 10 2008 009 600.

[0071] The second facet 23 may have a planar reflective surface or a curved reflective surface that is convex or concave.

[0072] Therefore, the illumination optical unit 4 forms a dual-facet system. This basic principle is also called a fly-eye condenser (fly-eye integrator).

[0073] It may be advantageous not to position the second facet mirror 22 precisely on a plane optically conjugate to the pupil plane of the projection optical unit 10. In particular, as described in German Patent Application Publication No. 10 2017 220 586, the second facet mirror 22 may be positioned at an angle to the pupil plane of the projection optical unit 10.

[0074] The individual first facets 21 are imaged into the object field of view 5 using the second facet mirror 22. The second facet mirror 22 is the last beam shaping mirror or, in fact, the final mirror for the illumination radiation 16 in the beam path upstream of the object field of view 5.

[0075] In yet another embodiment of the illumination optical unit 4 (not shown), a transfer optical unit, which contributes particularly to the imaging of the first facet 21 onto the object field of view 5, may be positioned in the beam path between the second facet mirror 22 and the object field of view 5. The transfer optical unit may have strictly one mirror, or two or more mirrors positioned one behind the other in the beam path of the illumination optical unit 4. The transfer optical unit may, in particular, include one or two mirrors for perpendicular incidence (NI mirrors) and / or one or two mirrors for oblique incidence (GI mirrors).

[0076] In the embodiment shown in Figure 1, the illumination optical unit 4 has exactly three mirrors downstream of the collector 17, specifically a deflection mirror 19, a first facet mirror 20, and a second facet mirror 22.

[0077] In yet another embodiment of the illumination optical unit 4, the deflection mirror 19 may be omitted, so the illumination optical unit 4 may have exactly two mirrors downstream of the collector 17, specifically a first facet mirror 20 and a second facet mirror 22.

[0078] The imaging of the first facet 21 onto the object surface 6 by the second facet 23, or by using the second facet 23 and the transfer optics unit, is in most cases only an approximate image.

[0079] The projection optical unit 10 includes a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure apparatus 1.

[0080] In the example shown in Figure 1, the projection optical unit 10 includes six mirrors M1 to M6. It can also be replaced with four, eight, ten, twelve, or different numbers of mirrors Mi. The projection optical unit 10 is a double-shielded optical unit. The second-to-last mirror M5 and the last mirror M6 each have apertures through which illumination radiation 16 passes. The projection optical unit 10 has an image-side numerical aperture greater than 0.5 and may be greater than 0.6, for example, 0.7 or 0.75.

[0081] The reflective surface of mirror Mi may take the form of a free-form surface without an axis of rotational symmetry. Alternatively, the reflective surface of mirror Mi can be designed as an aspherical surface with exactly one axis of rotational symmetry of the reflective surface shape. Similar to the mirrors of illumination optical unit 4, mirror Mi may have a highly reflective coating for illumination radiation 16. These coatings can be designed in particular as multilayer coatings having alternating layers of molybdenum and silicon.

[0082] The projection optical unit 10 has a large object-image offset in the y-direction y between the y-coordinate of the center of the object field of view 5 and the y-coordinate of the center of the image field of view 11. This object-image offset in the y-direction y may be approximately the same magnitude as the z-distance between the object plane 6 and the image plane 12.

[0083] The projection optics unit 10 can be embodied in a particularly anamorphic manner. In particular, it has different imaging scales βx and βy in the x-direction and y-direction. The two imaging scales βx and βy of the projection optics unit 10 are preferably (βx, βy) = (+ / -0.25, + / -0.125). A positive imaging scale β means imaging without image inversion. A negative sign for the imaging scale β means imaging with image inversion.

[0084] As a result, the projection optical unit 10 is reduced in size in the x-direction, i.e., perpendicular to the scanning direction, at a ratio of 4:1.

[0085] The projection optical unit 10 reduces its size in the y-direction, i.e., in the scanning direction, at a ratio of 8:1.

[0086] Other imaging scales are also possible. Imaging scales with the same sign and absolute value in the x-direction x and y-direction y, for example, absolute values ​​of 0.125 or 0.25, are also possible.

[0087] The number of intermediate image planes in the x-direction x and y-direction y in the beam path between the object field of view 5 and the image field of view 11 may be the same or may differ depending on the design of the projection optical unit 10. An example of a projection optical unit with a different number of such intermediate images in the x-direction x and y-direction y is known from U.S. Patent Application Publication No. 2018 / 0074303.

[0088] Each of the second facets 23 is assigned to exactly one of the first facets 21 to form an illumination channel that illuminates the object field of view 5. In particular, this allows for illumination according to Köhler's principle. The distant field of view is decomposed into multiple object fields of view 5 using the first facets 21. The first facets 21 generate multiple intermediate-focus images in the second facets 23 assigned to each of them.

[0089] The assigned second facet 23 causes the first facet 21 to be imaged onto the reticle 7 as an overlapping image for the purpose of illuminating the object field of view 5. The illumination of the object field of view 5 is particularly uniform. Preferably, the uniformity error is less than 2%. Field of view uniformity can be achieved by superimposing different illumination channels.

[0090] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the arrangement of the second facet 23. By selecting the illumination channel to guide light, particularly a subset of the second facet 23, the intensity distribution in the entrance pupil of the projection optical unit 10 can be set. This intensity distribution is also referred to as illumination setting or illumination pupil filling.

[0091] Similarly desirable pupil uniformity in a defined illuminated area of ​​the illumination pupil of the illumination optical unit 4 can be achieved by redistributing the illumination channels.

[0092] Further aspects and details of the illumination of the object field of view 5, particularly the entrance pupil of the projection optical unit 10, will be described below.

[0093] In particular, the projection optics unit 10 may have a concentric entrance pupil. This can be made accessible. This can also be made inaccessible.

[0094] The entrance pupil of the projection optical unit 10 cannot always be precisely illuminated by the second facet mirror 22. When the projection optical unit 10 images the center of the second facet mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, it is possible to find a plane where the distance between the pairs of aperture rays is minimized. This plane represents the entrance pupil or a real-space plane conjugate to it. In particular, this plane exhibits a finite curvature.

[0095] In the projection optics unit 10, the position of the entrance pupil may differ between the tangential beam path and the sagittal beam path. In this case, an imaging element, particularly an optical component of the transfer optics unit, should be placed between the second facet mirror 22 and the reticle 7. This optical element can be used to account for the difference in the relative positions of the tangential and sagittal entrance pupils.

[0096] In the arrangement of the components of the illumination optical unit 4 shown in Figure 1, the second facet mirror 22 is positioned on a plane conjugate to the entrance pupil of the projection optical unit 10. The first facet mirror 20 is positioned at an angle with respect to the object surface 6. The first facet mirror 20 is positioned at an angle with respect to the arrangement plane defined by the deflection mirror 19. The first facet mirror 20 is positioned at an angle with respect to the arrangement plane defined by the second facet mirror 22.

[0097] Figure 2 shows a schematic diagram of one embodiment of a lithography apparatus or projection exposure apparatus 1, such as the one shown in Figure 1.

[0098] In this case, Figure 2 shows radiation S having a specific repetition frequency generated by the radiation source 3 of the lithography apparatus 1 shown in Figure 1. Furthermore, Figure 2 shows a MEMS mirror 30 that is displaceable at an inclination angle W and serves to guide the radiation S within the lithography apparatus 1. The MEMS mirror 30 may be, for example, part of one of the mirrors 20, 22, M1-M6 of the lithography apparatus 1 from Figure 1.

[0099] The MEMS mirror 30 includes a mirror plate 31 that can be displaced at an inclination angle W, a carrier plate 32 that supports the mirror plate 31, a base plate 33, a flexure 34 that connects the carrier plate 32 and the base plate 33, and a capacitance sensor 35 having a plurality of electrodes 36, 37 positioned between the carrier plate 32 and the base plate 33.

[0100] As further shown in Figure 2, the capacitance sensor 35 has an upper electrode 36 positioned in the direction of the mirror plate 31 and a lower electrode 37 positioned in the direction of the base plate 33 in order to measure the tilt angle W of the mirror plate 31 of the MEMS mirror 30. In the example in Figure 2, the upper electrode 36 is positioned on the carrier plate 32, while the lower electrode 37 is positioned on the base plate 33. The electrodes 36 and 37 of the capacitance sensor 35 are embodied in a comb shape and are arranged to interlock. The comb-shaped electrodes 36 and 37 of the capacitance sensor 35 each have notches through which a flexure 34 connecting the carrier plate 32 and the base plate 33 passes.

[0101] The mirror plate 31 is connected to ground via the first resistor 72. Furthermore, the upper electrode 36 of the capacitance sensor 35 is connected to ground via the second resistor 72.

[0102] The MEMS mirror 30 is displaceable in particular along two tilt axes, preferably two mutually orthogonal tilt axes. Two control units 61 and 62 are provided for each tilt axis to actuate the mirror plate 31 in order to displace the mirror plate 31.

[0103] In this regard, the cross-sectional view of the MEMS mirror 30 in Figure 2 shows one tilt axis. Each measurement signal I from the capacitance sensor 35 S1 ~I S4 To acquire the tilt angle W, four sensor units 41, 42, 43, and 44 are provided for each tilt angle. Sensor units 41 to 44 form an acquisition device 40 for acquiring the tilt angle W. In this case, the first pair formed by, for example, sensor unit 41 and sensor unit 43 of the four sensor units 41 to 44, excites the capacitance sensor 35 with a first excitation signal V1 and, in response, each measurement signal I S1 , I S3 It is configured to receive.

[0104] Therefore, the first pair is formed by sensor unit 41 and sensor unit 43. Sensor unit 41 excites the capacitance sensor 35 with the first excitation signal V1 and, in response, the measurement signal IS1 receives this. In response, the sensor unit 43 excites the capacitance sensor 35 with the first excitation signal V1, and in response thereto, receives the measurement signal I S3 therefrom.

[0105] In an embodiment, the excitation of the first sensor unit 41 and the excitation of the third sensor unit 43 can be performed by a single first excitation signal V1.

[0106] Furthermore, for example, a second pair 42, 44 formed by the sensor unit 42 and the sensor unit 44 among the four sensor units 41 to 44 excites the capacitance sensor 35 with the second excitation signal V2, and in response thereto, receives each measurement signal I S2 、I S4 therefrom.

[0107] The sensor unit 42 and the sensor unit 44 form a second pair. In this case, the sensor unit 42 excites the capacitance sensor 35 with the second excitation signal V2, and in response thereto, receives the measurement signal I S2 therefrom. In response to this, the sensor unit 44 excites the capacitance sensor 35 with the second excitation signal V2, and in response thereto, receives the measurement signal I S4 therefrom. The first excitation signal V1 and the second excitation signal V2 have opposite polarities (in this regard, for example, refer to the left part of FIG. 4). The first excitation signal V1 and the second excitation signal V2 are embodied as excitation voltages having particularly different polarities. Since the first excitation signal V1 and the second excitation signal V2 have opposite polarities, they form a differential pair. Each measurement signal I S1 ~I S4 is particularly embodied as an electric circuit.

[0108] An evaluation unit 50 connected downstream of the sensor units 41 to 44 of the lithography apparatus shown in FIG. 2 determines the position P of the MEMS mirror 30 based on the measurement signals I S1 ~I S4 from the four sensor units 41 to 44.

[0109] Furthermore, as shown in Figure 2, a voltmeter 80 can also be provided, which measures the voltage U between the mirror plate 31 and the base plate 33 (or ground). M It is configured to measure the drop. Since the base plate 33 is grounded, the voltmeter 80 can also be placed between the mirror plate 33 and ground. Using the voltmeter 80, the evaluation unit 50 receives the measurement signal I supplied by the four sensor units 41-44. S1 ~I S4 and the measured voltage U M The system can also be configured to determine the position P of the MEMS mirror 30. This improves the accuracy of determining the position P of the MEMS mirror 30.

[0110] Figure 3 shows a schematic cross-sectional view of one embodiment of the sensor unit of the lithography apparatus shown in Figure 2. Figure 3 shows two tilt axes A1 and A2 to which the MEMS mirror 30 shown in Figure 2 can be displaced. Four sensor units are assigned to each tilt axis A1 and A2. Therefore, sensor units S1 to S4 are assigned to tilt axis A1, while sensor units S5 to S8 are assigned to tilt axis A2. Two sensor units each form a pair. For example, for tilt axis A1, sensor units S1 and S3 form the first pair, while sensor units S2 and S4 form the second pair. Therefore, referring to Figure 2, sensor unit S1 in Figure 3 corresponds to sensor unit 41 in Figure 2, sensor unit S2 in Figure 3 corresponds to sensor unit 42 in Figure 2, sensor unit S3 in Figure 3 corresponds to sensor unit 43 in Figure 2, and sensor unit S4 in Figure 3 corresponds to sensor unit 44 in Figure 2.

[0111] Figure 4 shows a schematic diagram of one embodiment of the acquisition unit 40 and evaluation unit 50 having sensor units 41 to 44 of the lithography apparatus 1 shown in Figure 2.

[0112] Sensor units 41-44 are shown as variable capacitances in Figure 4. In this case, the capacitance of each sensor unit 41-44 changes with the inclination angle W shown by the arrow passing through capacitances 41-44 in Figure 4, and capacitances 41-44 are affected by the inclination angle W according to the dashed line shown in Figure 4.

[0113] The left region of Figure 4 shows the first excitation signal V1, the second excitation signal V2, and the disturbance voltage V generated by the radiation S. S This shows the disturbance voltage V. S This occurs on the mirror surface of the MEMS mirror 30 when the incident radiation S knocks electrons out of the mirror surface of the MEMS mirror 30. The disturbance voltage V S This generates the aforementioned disturbances at the outputs of sensor units 41 to 44.

[0114] The first pair, including sensor units 41 and 43, is controlled using the first excitation signal V1. The second pair, including sensor units 42 and 44, is excited using the second excitation signal V2, which has the opposite polarity. Disturbance voltage V S This is shown twice because it affects both the first pair, which includes sensor units 41 and 43, and the second pair, which includes sensor units 42 and 44.

[0115] The evaluation unit 50 shown in Figure 4 includes a first converter 51, a second converter 52, and a subtractor 53. The first converter 51 processes the measurement signals I of the first pair 41 and 43 of the sensor unit. S1 , I S2 The received measurement signal I S1 , I S3 The first converter 51 is configured to supply a first voltage signal U1 on the output side that is proportional to the difference between the two. The first converter 51 is specifically embodied as a capacitive-voltage converter and can be referred to as the first capacitive-voltage converter 51. The first capacitive-voltage converter 51 receives a first current I at the input connected to the first sensor unit 41. S1 It is configured to receive the first current I S1 This refers to the current I generated at the output of the first sensor unit 41 due to the excitation of the capacitance sensor 35 by the first excitation signal V1. AS1The current I generated at the output of the first sensor unit 41 due to disturbances caused by radiation S in the MEMS mirror 30 SS1 This corresponds to the sum of . Symbol I AS1 In this diagram, I represents current, A represents excitation, and S1 represents the first sensor unit 41 or S1 (see Figure 3). Symbol I SS1 In this equation, I represents the current and S represents the disturbance voltage V. S This indicates the disturbance generated by the first sensor unit 41 or S1.

[0116] The first capacitance-voltage converter 51 is further connected to the input of the third sensor unit 43, and the current I generated at the output of the third sensor unit 43 due to the excitation of the capacitance sensor 35 with the first excitation signal V1 AS3 The disturbance generated by radiation S in the MEMS mirror 30 causes a current I to be generated at the output of the third sensor unit 43. SS3 The third current I corresponds to the sum of the above. S3 It is configured to receive the symbol I. AS3 In this diagram, I represents current, A represents excitation, and S3 represents the third sensor unit 43 or S3. Symbol I SS3 In this equation, I represents the current and S represents the disturbance voltage V. S This indicates the disturbance generated by the third sensor unit 43 or S3.

[0117] Received current I S1 , I S3 Based on this, the first capacitance-voltage converter 51 is configured to determine the first voltage signal U1 according to the following equation (1) and output the first voltage signal on the output side. In this case, C INT This indicates the capacitance of the first capacitance-voltage converter 51.

number

[0118] current I S1 , I S3 If we consider electric charge instead, equation (1) above can also be expressed as equation (2).

number

[0119] In this case, Q S1 Q indicates the charge supplied by the output of the first sensor unit 41 or S1 due to excitation with the first excitation signal V1, and S3 Q indicates the charge supplied by the output of the third sensor unit 43 or S3 due to excitation with the first excitation signal V1, and SS1 The disturbance voltage V S This indicates the charge supplied by the output of the first sensor unit 41 or S1, and Q SS3 The disturbance voltage V S This indicates the charge supplied by the output of the third sensor unit 43 or S3 as a result of the above.

[0120] The second converter 52 receives the measurement signals I of the second pair 42, 44 of the sensor unit. S2 , I S4 The received measurement signal I S2 , I S4 The system is configured to supply a second voltage signal U2 on the output side that is proportional to the difference between the two. The second converter 52 is also preferably implemented as a capacitive-to-voltage converter and can be referred to as the second capacitive-to-voltage converter 52.

[0121] The second capacitance-voltage converter 52 is an input connected to the second sensor unit 42, and the current I generated at the output of the second sensor unit 42 due to the excitation of the capacitance sensor 35 with the second excitation signal V2 AS2 The current I generated at the output of the second sensor unit 42 due to disturbances caused by radiation S in the MEMS mirror 30 SS3 The second current I corresponds to the sum of the two currents. S2 The input is configured to receive the second excitation signal V2, and the current I generated at the output of the fourth sensor unit 44 due to the excitation of the capacitance sensor 35 with the second excitation signal V2 is connected to the input of the fourth sensor unit 44. AS4 The disturbance caused by radiation S in the MEMS mirror 30 generates a current I at the output of the fourth sensor unit 44. SS4 The fourth current I corresponds to the sum of the above. S4It is configured to receive a second voltage signal U2 according to equation (3) and to output the second voltage signal.

number

[0122] In this case, C INT This indicates the capacitance of the second capacitance-voltage converter 52.

[0123] current I S2 , I S4 If we consider electric charge instead, equation (3) above can also be expressed as equation (4).

number

[0124] The subtractor 53 subtracts the second voltage signal U2 from the first voltage signal U1, and outputs a difference signal U accordingly. D It was configured to output. U D =U1-U2(5)

[0125] The disturbances (i.e., each disturbance voltage V) generated by the incident radiation S in the mutually adjacent sensor units 41-44 (or S1-S4 in Figure 3) in Figures 2 and 4 S Assuming that ) are the same or nearly the same, charge Q SS1 Q SS2 Q SS3 , and Q SS4 They are identical or nearly identical. In that case, U D This can be calculated as follows using equation (6):

number

[0126] As shown in equation (6), the difference signal U D is the disturbance voltage V S The signal component resulting from this, and therefore Q SS1 Q SS2 Q SS3, and Q SS4 It does not include the difference signal U. In that case, the evaluation unit 50 will use the difference signal U. D The position P of the MEMS mirror 30 can be precisely determined using this method.

[0127] Figure 5 shows a schematic diagram of one embodiment of an acquisition unit 40 and an evaluation unit 50 having sensor units 41-44 of the lithography apparatus 1 shown in Figure 2. The embodiment shown in Figure 5 is substantially based on the embodiment shown in Figure 2, and further improves the suppression of EUV disturbances by allowing individual tolerance adjustments. For this purpose, the first A / D converter 55 and the first weighting unit 56 are connected downstream of the first capacitance-voltage converter 51. Correspondingly, the second A / D converter 57 and the second weighting unit 58 are connected downstream of the second capacitance-voltage converter 52.

[0128] The first A / D converter 55 receives the first voltage signal U supplied by the first capacitance-voltage converter 51. 1A to digital first voltage signal U 1D The first weighting unit 56 is configured to convert the weighted first voltage signal U 1G To output the digital first voltage signal U, the actual tilt angle of the MEMS mirror 30 measured by a measurement unit (not shown) is used. 1D It is configured to assign weights to the following:

[0129] The second A / D converter 57 receives the second voltage signal U supplied by the second capacitance-voltage converter 52. 2A to digital second voltage signal U 2D The second weighting unit 58 is configured to convert the second weighted voltage signal U 2G To output the digital second voltage signal U, the actual tilt angle of the MEMS mirror 30 measured by the measurement unit is used. 2D It is configured to weight the first voltage signal U. 1G and weighted second voltage signal U 2G By considering the tolerances of the MEMS mirror 300, it is advantageous to further improve the suppression of EUV disturbances.

[0130] In this case, the subtractor 53 outputs the weighted second voltage signal U 2G The weighted first voltage signal U 1G Subtract from it, and the difference signal U is output accordingly. D It is configured to output the difference signal U. D The position P of the MEMS mirror 30 can be determined using this method.

[0131] Figure 6 shows a schematic diagram of yet another embodiment of the acquisition device 40 and evaluation unit 50 having sensor units, particularly the lithography apparatus 1 shown in Figure 2. The embodiment shown in Figure 6 is substantially based on the embodiment shown in Figure 2, but differs in that the embodiment shown in Figure 6 uses only two sensor units 41 and 42 for each tilt axis. Therefore, according to Figure 6, the acquisition device 40 for acquiring the tilt angle W has two sensors for each tilt axis.

[0132] Sensor units 41 and 42 are excited by the excitation signal V1 shown in Figure 7. The disturbance voltage V shown in Figure 8 S This is generated by electrons knocked out of the mirror surface of the MEMS mirror 30 (see Figure 2) by radiation S from the radiation source 3, and (as explained with reference to Figure 4) generates an additional current at the output of each sensor unit 41, 42. Similarly, as explained with reference to Figure 4, the evaluation unit 50 shown in Figure 6 receives the first current I from the sensor unit 41. S1 and the second current I from the sensor unit 42 S2 Receives the first current I S1 This corresponds to the sum of the current generated at the output of the first sensor unit 41 due to the excitation of the capacitance sensor 35 by the excitation signal V1 shown in Figure 7, and the current generated at the output of the first sensor unit 41 due to the disturbance (see Figure 8) caused by the radiation S in the MEMS mirror 30.

[0133] In response to this, the second current I S2This corresponds to the sum of the current generated at the output of the second sensor unit 42 due to the excitation of the capacitance sensor 35 by the excitation signal V1 and the current generated at the output of the second sensor unit 42 due to the disturbance caused by the radiation S in the MEMS mirror 30. The evaluation unit 50 in Figure 6 is the above current I S1 and I S2 Upon receiving the signal, the output side outputs a difference signal U. D It supplies the difference signal U, as shown in Figure 9. D is the disturbance voltage V S Includes high-frequency signal components caused by the disturbance shown in Figure 9. D This is supplied to the low-pass filter 54 shown in Figure 6, and the low-pass filter 54 removes high-frequency disturbances and outputs the difference signal U after low-pass filtering. T Outputs the difference signal U after low-pass filtering. T The position P of the MEMS mirror 30 can be determined using the difference signal U shown in Figure 9. D Unlike the difference signal U after low-pass filtering shown in Figure 10, T Since this does not include disturbances generated by the incident radiation S, this determination is highly accurate. As an alternative to or in addition to the low-pass filter 54, it is possible to use a filter that removes values ​​with a specified deviation.

[0134] Figure 11 shows a schematic diagram of how the lithography apparatus 1 is operated. The lithography apparatus 1 includes a radiation source 3 that generates radiation S having a specific repetition frequency, a MEMS mirror 30 that guides the radiation S within the lithography apparatus 1 and is displaceable at an inclination angle W on at least two inclination axes A1, A2, and a capacitance sensor 35 having multiple electrodes 36, 37 for acquiring the inclination angle W, and each measurement signal I from the capacitance sensor 35 S1 ~I S4 The system includes a MEMS mirror 30 and four sensor units 41-44, each provided on a tilt axis A1, A2, for the purpose of acquiring [specific data]. The method shown in Figure 11 includes steps 101-103. In particular, steps 101 and 102 are performed simultaneously.

[0135] In step 101, the first pair of sensor units 41 and 43 among the four sensor units 41 to 44 excite the capacitance sensor 35 with the first excitation signal V1, and in response, each of the first pair of sensor units 41 and 43 generates the respective measurement signals I S1 , I S3 Receive.

[0136] In step 102, the second pair of sensor units 42 and 44 among the four sensor units 41 to 44 excite the capacitance sensor 35 with the second excitation signal V2, and in response, each of the sensor units 42 and 44 in the second pair generates the respective measurement signals I S2 , I S4 The second excitation signal V2 has the opposite polarity to the first excitation signal V1.

[0137] In step 103, the measurement signals I from the four sensor units 41-44 S1 ~I S4 The position of the MEMS mirror 30 is determined by this.

[0138] Although the present invention has been described based on exemplary embodiments, it can be modified in various ways. [Explanation of symbols]

[0139] 1. Projection exposure apparatus 2. Lighting System 3 Radiation source 4. Illumination Optical Unit 5 Object field of view 6 Object plane 7 Reticle 8 Reticle holders 9. Reticle displacement drive 10 Projection Optical Unit 11 Image field 12 Image plane 13 wafers 14 Wafer holder 15 Wafer Displacement Drive 16 Illumination Radiation 17 Collector 18 Intermediate focal plane 19. Polarizing mirror 20 First Facet Mirror 21 First Facet 22. Second Facet Mirror 23 Second Facet 30 Mirror 31 Mirror Plate 32 Carrier Plate 33 Base Plate 34 Flexia 35 Capacitive Sensors 36 Upper comb electrode 37 Lower comb electrode 40 Acquisition Devices 41 Sensor Unit 42 Sensor Units 43 Sensor Unit 44 Sensor Units 50 evaluation units 51 Converters, Capacitance-Voltage Converters 52 Converters, Capacitance-Voltage Converters 53 Subtractor 54 Low-pass filter 55 A / D Converters 56 weighting units 57 A / D Converters 58 weighting units 61 Control Unit 62 Control Unit 71 Resistors 72 resistors 80 Voltmeter 101 Steps 102 steps 103 steps A1 tilt axis A2 tilt axis I AS1 Current generated at the output of the first sensor unit due to excitation by the excitation signal. I AS2 Current generated at the output of the second sensor unit due to excitation by the excitation signal. I AS3 Current generated at the output of the third sensor unit due to excitation by the excitation signal. I AS4Current generated at the output of the fourth sensor unit due to excitation by the excitation signal. I SS1 Current generated at the output of the first sensor unit due to EUV disturbance I SS2 Current generated at the output of the second sensor unit due to EUV disturbance I SS3 Current generated at the output of the third sensor unit due to EUV disturbance I SS4 Current generated at the output of the fourth sensor unit due to EUV disturbance M1 Mirror M2 Mirror M3 Mirror M4 Mirror M5 Mirror M6 Mirror P Mirror Position S radiation S1 Sensor Unit S2 Sensor Unit S3 Sensor Unit S4 Sensor Unit U D Difference signal U T The difference signal after low-pass filtering. U1 First voltage signal U 1A Analog first voltage signal U 1D Digital first voltage signal U 1G Weighted first voltage signal U2 Second Voltage Signal U 2A Analog second voltage signal U 2D Digital second voltage signal U 2G Weighted second voltage signal U M Voltage between the mirror plate and the base plate V1 First Excitation Signal V2 second excitation signal V S Disturbance voltage (disturbance caused by incident radiation) W Tilt angle

Claims

1. Lithography apparatus (1), A radiation source (3) that emits radiation (S) having a specific repetition frequency, At least two tilt axes (A １ , A ２ ), a MEMS mirror (30) for guiding the radiation (S) in a lithographic apparatus (1) and displaceable at a tilt angle (W), including a capacitance sensor (35) having a plurality of electrodes (36, 37) for obtaining the tilt angle (W), and four sensor units (41 to 44) are provided for each of the tilt axes (A Ｓ１ to I Ｓ４ ) for the purpose of obtaining each measurement signal (I １ , A ２ ). A first pair (41, 43) of the four sensor units (41 to 44) is configured to excite the capacitance sensor (35) with a first excitation signal (V １ ) and receive each measurement signal (I Ｓ１ , I Ｓ３ ) in response thereto. A second pair (42, 44) of the four sensor units (41 to 44) is configured to excite the capacitance sensor (35) with a second excitation signal (V ２ ) and receive each measurement signal (I Ｓ２ , I Ｓ４ ) in response thereto. The first excitation signal (V １ ) and the second excitation signal (V ２ ) have opposite polarities, a MEMS mirror (30), and The measurement signals (I Ｓ１ ~I Ｓ４ An evaluation unit (50) is configured to determine the position (P) of the MEMS mirror (30) by the means of the evaluation unit (50) A lithography apparatus equipped with [a specific feature / feature].

2. In the lithography apparatus according to claim 1, The evaluation unit (50) is a lithography apparatus, which is embodied as a differential evaluation unit (50).

3. In the lithography apparatus according to claim 1 or 2, The evaluation unit (50) is The measurement signals (I Ｓ１ , I Ｓ３ ) receives the received measurement signal (I Ｓ１ , I Ｓ３ A first voltage signal (U) proportional to the difference between ) １ A first converter (51) is configured to supply ) on the output side, The measurement signals (I Ｓ２ , I Ｓ４ ) receives the received measurement signal (I Ｓ２ , I Ｓ４ A second voltage signal (U) proportional to the difference between ) ２ A second converter (52) is configured to supply ) on the output side, Second voltage signal (U ２ ) to the first voltage signal (U １ ) is subtracted, and the difference signal (U) is output accordingly. Ｄ A subtractor (53) configured to output ) and Lithography equipment, including [specific component].

4. In the lithography apparatus according to claim 3, The first converter (51) receives the first excitation signal (V) at the input connected to the first sensor unit (41). １ ) The excitation of the capacitance sensor (35) generates a current (I) at the output of the first sensor unit (41). ＡＳ１ ) and the current (I) generated at the output of the first sensor unit (41) due to disturbances caused by the radiation (S) in the MEMS mirror (30) ＳＳ１ The first current (I) corresponds to the sum of ) Ｓ１ The input connected to the third sensor unit (43) is configured to obtain the first excitation signal (V １ (Current I) is generated at the output of the third sensor unit (43) due to the excitation of the capacitance sensor (35) at ). ＡＳ３ ) and the current (I) generated at the output of the third sensor unit (43) due to disturbances caused by the radiation (S) in the MEMS mirror (30) ＳＳ３ The third current (I) corresponds to the sum with ). Ｓ３ It is configured to obtain the formula [Math 1] According to the first voltage signal (U １ ) is embodied as a first capacitance-voltage converter configured to obtain and output the first voltage signal, in the formula, C ＩＮＴ A lithography apparatus, where is the capacitance of the first capacitance-voltage converter (51).

5. In the lithography apparatus according to claim 4, The second converter (52) receives the second excitation signal (V) at the input connected to the second sensor unit (42). ２ The excitation of the capacitance sensor (35) in ) generates a current (I) at the output of the second sensor unit (42). ＡＳ２ ) and the current (I) generated at the output of the second sensor unit (42) due to disturbances caused by the radiation (S) in the MEMS mirror (30) ＳＳ２ The second current (I) corresponds to the sum with ). Ｓ２ The input connected to the fourth sensor unit (44) is configured to obtain the second excitation signal (V ２ (Current I) is generated at the output of the fourth sensor unit (44) due to the excitation of the capacitance sensor (35) at ). ＡＳ４ ) and the current (I) generated at the output of the fourth sensor unit (44) due to disturbances caused by the radiation (S) in the MEMS mirror (30) ＳＳ４ The fourth current (I) corresponds to the sum with ). Ｓ４ It is configured to obtain the formula [Math 2] According to the second voltage signal (U ２ ) is embodied as a second capacitance-voltage converter configured to obtain and output the second voltage signal, in the formula, C ＩＮＴ A lithography apparatus, where is the capacitance of the second capacitance-voltage converter (52).

6. In the lithography apparatus according to any one of claims 3 to 5, The evaluation unit (50) uses the difference signal (U Ｄ A lithography apparatus configured to determine the position (P) of the MEMS mirror (30) using ).

7. In the lithography apparatus according to any one of claims 3 to 6, A first A / D converter (55) and a first weighting unit (56) are connected downstream of the first converter (51), and the first A / D converter (55) receives the first voltage signal (U) supplied by the first converter (51). １Ａ ) to digital first voltage signal (U １Ｄ The first weighting unit (56) is configured to convert the first weighted voltage signal (U １Ｇ In order to output the digital first voltage signal (U １Ｄ It is configured to weight the following: A second A / D converter (57) and a second weighting unit (58) are connected downstream of the second converter (52), and the second A / D converter (57) receives the second voltage signal (U) supplied by the second converter (52). ２Ａ ) to a digital second voltage signal (U ２Ｄ The second weighting unit (58) is configured to convert to a weighted second voltage signal (U ２Ｇ In order to output the digital second voltage signal (U ２Ｄ It is configured to weight the following: The subtractor (53) receives the weighted second voltage signal (U ２Ｇ ) to the weighted first voltage signal (U １Ｇ ) is subtracted, and the difference signal (U) is output accordingly. Ｄ A lithography apparatus configured to output (a lithography device).

8. In the lithography apparatus according to any one of claims 3 to 6, A lithography apparatus comprising a first transducer (51) and a second transducer (52), each including a trimmable capacitor, and a calibration unit configured to trim each trimmable capacitor according to the actual tilt angle of the MEMS mirror (30) measured by a measurement unit.

9. In the lithography apparatus according to any one of claims 1 to 7, A lithography apparatus comprising a MEMS mirror (30), a mirror plate (31) that is displaceable at the tilt angle (W), a carrier plate (32) that supports the mirror plate (31), a base plate (33), a flexure (34) that connects the base plate (33) and the carrier plate (32) to tilt the mirror plate (31), and the capacitance sensor (35).

10. In the lithography apparatus according to claim 9, Lithography apparatus, wherein the capacitance sensor (35) includes an upper electrode (36) positioned in the direction of the mirror plate (31) and a lower electrode (37) positioned in the direction of the base plate (33) for measuring the tilt angle (W) of the mirror plate (31) of the MEMS mirror (30).

11. In the lithography apparatus according to claim 9 or 10, A lithography apparatus in which the electrodes (36, 37) of the capacitance sensor (35) are realized in a comb shape and arranged to interlock.

12. In the lithography apparatus according to claim 10, A lithography apparatus in which the comb-shaped electrodes (36, 37) of the capacitance sensor (35) each have notches through which the flexure (34) connecting the carrier plate (32) and the base plate (33) passes.

13. In the lithography apparatus according to any one of claims 1 to 12, For the purpose of displacing the mirror plate (31), two control units (61, 62) that operate the mirror plate (31) are connected to the tilt axis (A １ A ２ A lithography device installed at each location.

14. In the lithography apparatus according to any one of claims 1 to 13, The voltage between the mirror plate (31) and the base plate (33) (U Ｍ A voltmeter (80) is provided to measure the drop of the voltage, and the evaluation unit (50) receives the measurement signal (I) supplied by the four sensor units (41-44). Ｓ１ ~I Ｓ４ ) and the measured voltage (U Ｍ A lithography apparatus configured to determine the position (P) of the MEMS mirror (30) by the above.

15. In the lithography apparatus according to any one of claims 1 to 14, A lithography apparatus equipped with a micromirror array having multiple MEMS mirrors (30).

16. In the lithography apparatus described in item 15 of the claim, The micromirror array is part of the illumination system (2) of the lithography apparatus (1).

17. A method for operating a lithography apparatus (1), wherein the lithography apparatus (1) comprises a radiation source (3) that generates radiation (S) having a specific repetition frequency, and at least two tilt axes (A １ A ２ A MEMS mirror (30) that is displaceable at an inclination angle (W) in the lithography apparatus (1) and serves to guide the radiation (S), and includes a capacitance sensor (35) having a plurality of electrodes (36, 37) for acquiring the inclination angle (W), and each measurement signal (I Ｓ１ ~I Ｓ４ Four sensor units (41-44) are used to obtain the tilt axis (A) １ A ２ In a method comprising a MEMS mirror (30) provided for each of the following, Of the four sensor units (41-44), the first pair (41, 43) generates the first excitation signal (V １ The capacitance sensor (35) is excited by the above, and in response, each of the first pair of sensor units (41, 43) (41, 43) measures each measurement signal (I Ｓ１ , I Ｓ３ The step of receiving (101), Of the four sensor units (41-44), the second pair (42, 44) generates the second excitation signal (V ２ The capacitance sensor (35) is excited by the second pair of sensor units (42, 44) and in response, each measurement signal (I Ｓ２ , I Ｓ４ The step (102) is to receive the second excitation signal (V ２ ) is the first excitation signal (V １ Step (102) has the opposite polarity to ) and The measurement signals (I Ｓ１ ~I Ｓ４ The step (103) is to determine the position (P) of the MEMS mirror (30) by the above method. Methods that include...

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