# US 9,001,309 B2 · Method and device for monitoring multiple mirror arrays in an illumination system of a microlithographic projection exposure apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,001,309 B2 - Document ID: US9001309B2 - Status: Granted - Kind: B2 - Application number: 14/255,371 - Filed: 2014-04-17 - Published: 2014-08-14 - Granted: 2015-04-07 - Earliest claimed: 2007-02-06 - Assignees: Carl Zeiss SMT GmbH - Applicants: Carl Zeiss SMT GmbH - Inventors: Stefan Xalter; Yim-Bun Patrick Kwan; Andras G. Major; Manfred Maul; Johannes Eisenmenger; Damian Fiolka; Jan Horn; Markus Deguenther; Florian Bach; Michael Patra; Johannes Wangler; Michael Layh - Web page: https://patentgrep.com/patent/US9001309B2 ## CPC - G03F 7/70258: {Projection system adjustments, e.g. adjustments during exposure or alignment during assembly of projection system} - G01B 11/002: {for measuring two or more coordinates} - G01B 11/272: {using photoelectric detection means} - G01M 11/30: {Testing of optical devices, constituted by fibre optics or optical waveguides} - G01N 21/55: Specular reflectivity - G02B 26/0833: {the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD (G02B26/0825 takes precedence; micromechanical devices in general B81B)} - G03F 7/70058: {Mask illumination systems} - G03F 7/70116: {Off-axis setting using a programmable means, e.g. liquid crystal display [LCD], digital micromirror device [DMD] or pupil facets} - G03F 7/70133: {Measurement of illumination distribution, in pupil plane or field plane} - G03F 7/702: {Reflective illumination, i.e. reflective optical elements other than folding mirrors, e.g. extreme ultraviolet [EUV] illumination systems} - G03F 7/70291: {Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices} - G03F 7/70516: {Calibration of components of the microlithographic apparatus, e.g. light sources, addressable masks or detectors} - G03F 7/7085: {Detection arrangement, e.g. detectors of apparatus alignment possibly mounted on wafers, exposure dose, photo-cleaning flux, stray light, thermal load} - G05B 13/048: {using a predictor} - Y10S 359/904: Micromirror - G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G) - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G) - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract Microlithographic illumination system includes individually drivable elements to variably illuminate a pupil surface of the system. Each element deviates an incident light beam based on a control signal applied to the element. The system also includes an instrument to provide a measurement signal, and a model-based state estimator configured to compute, for each element, an estimated state vector based on the measurement signal. The estimated state vector represents: a deviation of a light beam caused by the element; and a time derivative of the deviation. The illumination system further includes a regulator configured to receive, for each element: a) the estimated state vector; and b) target values for: i) the deviation of the light beam caused by the deviating element; and ii) the time derivative of the deviation. ## Claims ### Claim 1 A monitoring device for monitoring an arrangement of beam deviating elements positioned in a first plane, the device comprising: a detector positioned in a second plane; a Fourier optical system positioned to direct light from the arrangement of beam deviating elements to the detector; and an evaluation device coupled to the detector and configured to provide information about an alignment of one or more of the beam deviating elements based on a signal from the detector; wherein the second plane is a Fourier plane of the Fourier optical system, and wherein the first and second planes are neither parallel, nor perpendicular. ### Claim 2 (depends on 1) The monitoring device of claim 1, wherein the detector comprises at least one image recorder configured as a 4-quadrant detector. ### Claim 3 (depends on 1) The monitoring device of claim 1, wherein each beam deviating element is a tiltable mirror having a reflecting mirror surface. ### Claim 4 (depends on 1) The monitoring device of claim 1, wherein each beam deviating element comprises a reflecting mirror surface, and wherein the information about the arrangement of the beam deviating elements comprises information about a change in a reflection coefficient of the reflecting mirror surface of one or more of beam deviating elements. ### Claim 5 (depends on 1) An illumination system having a pupil surface, the illumination system comprising: a projection light source; the monitoring device of claim 1; and the arrangement of beam deviating elements, wherein: the arrangement of beam deviating elements is configured to variably illuminate the pupil surface of the illumination system with projection light from the projection light source, each beam deviating element is configured to cause a deviation of a projection light beam incident thereon in response to a control signal applied to the beam deviating element, and the illumination system is configured to be used in a microlithographic projection exposure apparatus. ### Claim 6 (depends on 5) The illumination system according to claim 5, further comprising a control unit configured to apply the control signal to each beam deviating element to individually drive each beam deviating element. ### Claim 7 (depends on 5) The illumination system of claim 5, wherein the monitoring device further comprises a monitoring light source different from the projection light source, and wherein the monitoring light source is configured to generate the light received by the detector from the arrangement of beam deviating elements. ### Claim 8 (depends on 5) The illumination system of claim 5, wherein the Fourier optical system of the monitoring device is configured to convert angles of light emerging from the arrangement of beam deviating elements into positions of the light on the detector. ### Claim 9 (depends on 5) The illumination system according to claim 5, wherein the arrangement of beam deviating elements is encapsulated in a housing, the housing having a transparent window through which the projection light passes. ### Claim 10 (depends on 9) The illumination system according to claim 9, wherein light incident on the arrangement of beam deviating elements is configured to strike the transparent window at Brewster angle. ### Claim 11 (depends on 10) The illumination system according to claim 10, wherein the monitoring device further comprises a monitoring light source different from the projection light source, and wherein light from the monitoring light source comprises p-polarized light, and a reflected intensity of the p-polarized light at the transparent window is less than 5%. ### Claim 12 (depends on 9) The illuminating system according to claim 9, further comprising antireflection coatings disposed on the transparent window, the antireflection coatings being optimized for the projection light. ### Claim 13 An illumination system having a pupil surface, the illumination system comprising: a projection light source; an arrangement of beam deviating elements positioned in a first plane, a monitoring device for monitoring the arrangement of beam deviating elements, the device comprising: a detector positioned in a second plane; a Fourier optical system positioned to direct light from the arrangement of beam deviating elements to the detector; and an evaluation device coupled to the detector and configured to provide information about an alignment of one or more of the beam deviating elements based on a signal from the detector; wherein: the second plane is a Fourier plane of the Fourier optical system, the first and second planes are neither parallel, nor perpendicular the arrangement of beam deviating elements is configured to variably illuminate the pupil surface of the illumination system with projection light from the projection light source, and the illumination system is configured to be used in a microlithographic projection exposure apparatus. ### Claim 14 (depends on 13) The illumination system of claim 13, wherein the monitoring device further comprises a monitoring light source different from the projection light source, and wherein the monitoring light source is configured to generate the light received by the detector from the arrangement of beam deviating elements. ### Claim 15 An apparatus, comprising: an illumination system having a pupil surface, the illumination system comprising: a projection light source; an arrangement of beam deviating elements positioned in a first plane, a monitoring device for monitoring the arrangement of beam deviating elements, the device comprising: a detector positioned in a second plane; a Fourier optical system positioned to direct light from the arrangement of beam deviating elements to the detector; and an evaluation device coupled to the detector and configured to provide information about an alignment of one or more of the beam deviating elements based on a signal from the detector; and a projection objective, wherein: the second plane is a Fourier plane of the Fourier optical system, the first and second planes are neither parallel, nor perpendicular, the arrangement of beam deviating elements is configured to variably illuminate the pupil surface of the illumination system with projection light from the projection light source, and the apparatus is a microlithographic projection exposure apparatus. ### Claim 16 (depends on 15) The apparatus of claim 15, wherein the monitoring device further comprises a monitoring light source different from the projection light source, and wherein the monitoring light source is configured to generate the light received by the detector from the arrangement of beam deviating elements. ### Claim 17 A method for monitoring an arrangement of beam deviating elements positioned in a first plane of an illumination system, the method comprising: using a detector positioned in a second plane to detect light received from the arrangement of beam deviating elements; and determining information about an alignment of one or more the beam deviating elements based on a signal from the detector, wherein a Fourier optical system is positioned between the arrangement of beam deviating elements and the detector to direct the light from the arrangement of beam deviating elements to the detector, wherein the second plane is a Fourier plane of the Fourier optical system, and wherein the first and second planes are neither parallel, nor perpendicular. ### Claim 18 (depends on 17) The method of claim 17, wherein the Fourier optical system converts angles of light emerging from the arrangement of beam deviating elements into positions of the light on the detector. ### Claim 19 (depends on 17) The method of claim 17, further comprising regulating the alignment of the beam deviating elements using a control loop, wherein the control loop comprises a model-based state estimator. ### Claim 20 (depends on 19) The method of claim 19, wherein the model-based state estimator estimates a current alignment of the arrangement of the beam deviating elements based on a model and the signal from the detector. ### Claim 21 (depends on 20) The method of claim 20, wherein the model-based state estimator comprises a Kalman filter that accounts for stochastic inaccuracies of the signal from the detector. ### Claim 22 (depends on 17) The method of claim 17, further comprising using a control loop to control a tilt angle of a beam deviating element so that a setpoint value of the tilt angle is obtained. ### Claim 23 (depends on 22) The method of claim 22, wherein the control loop controls the title angle of the beam deviating element based on the signal from the detector. ### Claim 24 (depends on 23) The method of claim 23, wherein the control loop is operated at a regulating frequency f. ### Claim 25 (depends on 17) A method for illuminating a pupil plane in an illumination system of a microlithographic projection exposure apparatus, the method comprising: using an arrangement of beam deviating elements to variably illuminate the pupil plane of the illumination system of the microlithographic projection exposure apparatus; and monitoring the arrangement of beam deviating elements using the method of claim 17. ### Claim 26 (depends on 17) The method of claim 17, further comprising providing p-polarized light to the arrangement of beam deviating elements, wherein less than 5% of the p-polarized light is reflected at a transparent window of a housing encapsulating the arrangement of beam deviating elements. ### Claim 27 (depends on 26) The method of claim 26, wherein the arrangement of beam deviating elements is monitored during an operation of the projection exposure apparatus. ### Claim 28 (depends on 17) The method of claim 17, further comprising: reflecting a luminous pattern off the arrangement of beam deviating elements, and imaging the pattern to a camera. ### Claim 29 (depends on 28) The method of claim 28, wherein the luminous pattern is generated by illuminating a semi-reflective screen carrying a pattern or by illuminating through a transparent sheet carrying a pattern. ### Claim 30 (depends on 28) The method of claim 28, wherein tilts of multiple beam deviating elements are simultaneously determined.