Method and device for monitoring multiple mirror arrays in an illumination system of a microlithographic projection exposure apparatus

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.

1 . (canceled) 
     
     
         2 . A monitoring device for monitoring an arrangement of movable reflective optical elements, the device comprising:
 a measurement illumination apparatus configured to emit measuring light and direct the measurement light towards the arrangement of moveable reflective optical elements;   a lens having a focal plane;   a light detector arranged at least substantially in the focal plane of the lens, wherein the lens is configured to direct measuring light reflected from moveable reflective optical elements of the arrangement of moveable reflective optical elements to the light detector; and   an evaluation device coupled to the detector and configured to provide information about an alignment of one or more of the reflective optical elements based on a signal from the light detector,   wherein the arrangement of movable reflective optical elements is part of an illumination system of a microlithography tool.   
     
     
         3 . The monitoring device of  claim 2 , wherein the detector comprises at least one image recorder configured as a 4-quadrant detector. 
     
     
         4 . The monitoring device of  claim 2 , wherein each moveable reflective optical element is a tiltable mirror having a reflecting mirror surface. 
     
     
         5 . The monitoring device of  claim 2 , wherein the measurement illumination apparatus is configured to emit a plurality of measuring light beams so that at least one measuring light beam is incident on each of the reflective optical elements. 
     
     
         6 . The monitoring device of  claim 5 , wherein the measurement illumination apparatus comprises a plurality of individual measuring light sources. 
     
     
         7 . The monitoring device of  claim 6 , wherein the measuring light sources are semiconductor lasers. 
     
     
         8 . An illumination system comprising:
 a projection light source;   an arrangement of movable reflective optical elements; and   the monitoring device of  claim 2 , wherein:   the arrangement of moveable reflective optical elements is configured to variably illuminate a surface within the illumination system with projection light from the projection light source,   each moveable reflective optical element is configured to cause a deviation of a projection light beam incident thereon in response to a control signal applied to the reflective optical element, and   the illumination system is configured to be used in a microlithographic projection exposure apparatus.   
     
     
         9 . The illumination system according to  claim 8 , further comprising a control unit configured to apply the control signal to each moveable reflective optical element to individually drive each moveable reflective optical element. 
     
     
         10 . The illumination system of  claim 8 , wherein the monitoring light source of the monitoring device is different from the projection light source. 
     
     
         11 . The illumination system of  claim 8 , wherein the lens of the monitoring device is configured to convert angles of measuring light emerging from the arrangement of moveable reflective optical elements into positions of the light on the detector. 
     
     
         12 . The illumination system according to  claim 8 , wherein the arrangement of moveable reflective optical elements is encapsulated in a housing, the housing having a transparent window through which the projection light passes. 
     
     
         13 . The illumination system according to  claim 12 , wherein light incident on the arrangement of moveable reflective optical elements is configured to strike the transparent window at a Brewster angle. 
     
     
         14 . The illumination system according to  claim 13 , wherein the measuring light comprises p-polarized light, and an intensity of the p-polarized light reflected at the transparent window is less than 5%. 
     
     
         15 . The illuminating system according to  claim 12 , further comprising an antireflection coating disposed on the transparent window, the antireflection coating being optimized for the projection light. 
     
     
         16 . The illumination system of  claim 8 , wherein
 the arrangement of moveable reflective optical elements is positioned in a first plane,   the detector is positioned in a second plane, and   the first plane and the second plane are neither parallel nor perpendicular to each other.   
     
     
         17 . A method for monitoring an arrangement of movable reflective optical elements, the method comprising:
 directing measuring light on the arrangement of moveable reflective optical elements;   directing the measuring light reflected from the moveable reflective optical elements to a detector using a lens having a focal plane in which the detector is arranged; and   determining information about an alignment of one or more the moveable reflective optical elements based on a signal from the detector,   wherein the arrangement of movable reflective optical elements is part of an illumination system of a microlithography tool.   
     
     
         18 . The method of  claim 17 , further comprising regulating the alignment of the moveable reflective optical elements using a control loop, wherein the control loop comprises a model-based state estimator. 
     
     
         19 . The method of  claim 17 , wherein the model-based state estimator estimates a current alignment of the arrangement of the moveable reflective optical elements based on a model and the signal from the detector. 
     
     
         20 . The method of  claim 17 , wherein the arrangement of moveable reflective optical elements is monitored during an operation of a projection exposure apparatus in which the moveable reflective optical elements are arranged. 
     
     
         21 . The method of  claim 17 , wherein alignments of multiple moveable reflective optical elements are simultaneously determined. 
     
     
         22 . A method for illuminating a plane in an illumination system of a microlithographic projection exposure apparatus, the method comprising:
 using an arrangement of moveable reflective optical elements to variably illuminate the plane; and   monitoring the arrangement of moveable reflective optical elements using the method of  claim 17 .