Patent ID: 8102509
Filing Date: 2012-01-24
Classification: G03F

Abstract:
1. A focus and level condition control method adapted for use with a projection lens unit comprising a first plurality of lenses, wherein N is the number of lenses in the first plurality of lenses, the method comprising: irradiating a semiconductor substrate positioned under the projection lens with a measurement light after passing the measurement light through at least a second plurality of the lenses in the projection lens unit, wherein M is the number of lenses in the second plurality of lenses, wherein N is greater than or equal to M, and detecting a portion of the measurement light reflected from the semiconductor substrate as a first intensive value; irradiating the semiconductor substrate with a reference light without passing the reference light through any one of the first plurality of the lenses in the projection lens unit, and detecting a portion of the reference light reflected from the semiconductor substrate as a second intensive value; comparing the first and second intensive values to generate a control signal adapted to adjust the position of the semiconductor substrate under the projection lens to compensate for focus and level condition errors; and wherein divergence of the first and second intensity values from being identical indicates variation in a desired focus and level condition.