Patent ID: 6504608
Filing Date: 2003-01-07
Classification: G01B,G01N,G03F

Abstract:
An optical measurement arrangement, comprising:an ellipsometer (45) in which an incident beam (23) of polarized light is directed at an angle &agr;â‰ 90Â° onto a measurement location (M) on the surface of a specimen (P), and information as to specimen properties is obtained from an investigation of the reflected return beam (24); a device for ascertaining and correcting directional deviations between a line normal to the specimen surface and an angle bisector (25) between the incident and return beams (23, 24); an optical radiation source (33) emitting a direction monitoring beam (30) which is directed onto the measurement location (M) substantially in the direction of the angle bisector (25); a position-sensitive area detector (39) and a reflective optical element for imaging a return reflection of the direction monitoring beam (30) onto the position-sensitive area detector (39); an evaluation circuit (46) to which the position-sensitive area detector (39) is connected and said evaluation circuit (46) is for determining positions commands; and a positioning system (47, 47a) receiving the positioning commands of the evaluation circuit (46), wherein a specimen stage (12) on which the specimen (P) rests is caused to tilt until the position of the return reflection of the direction monitoring beam (30) on the position-sensitive area detector (39) corresponds to a predefined position at which the direction of the line normal to the specimen surface corresponds to the direction of the angle bisector (25), wherein the optical radiation source (33) is a focusable diode laser, and wherein a polarization splitter (35) and a &lgr;/4 plate (36) following the polarization splitter (35) are present in the beam path between the diode laser (33) and the surface of the specimen (P), the return reflection of the direction monitoring beam (30) from the polarization splitter (35) being directed onto the position-sensitive area detector (39).