Patent ID: 7242476

Claim:
An alignment measuring system for a photolithography process, comprising: a focusing diode; a light source emitting light; a first splitter adapted to direct a part of the light emitted from the light source toward a wafer disposed on a stage, and to direct in a first direction light returned by the wafer; a second splitter adapted to receive the light from the first splitter, to direct a first portion of the received light in a second direction, to direct a second portion of the received light toward the focusing diode, and to vary respective levels of the first and second portions of the received light in response to an applied control signal; an image sensor adapted to receive the first portion of the light from the second splitter and to produce a detection signal therefrom; and a controller adapted to receive the detection signal from the image sensor to determine an alignment state of the wafer, to control the stage so as to align and position the wafer, and to apply the control signal to the second splitter.