Patent ID: 8357549

Claim:
A method for identifying an incorrect radial position of a semiconductor wafer to be thermally treated in a thermal treatment apparatus having a process chamber transmissive to infrared radiation, the semiconductor wafer having a radius r 1 , and lying within a circular pocket of a rotating susceptor, the circular pocket having a center of radius and a radius r 2 greater than r 1 , the semiconductor wafer heated by infrared radiation transmitted through the process chamber and maintained at a predetermined temperature by means of a control system, the method comprising: providing a pyrometer having a measurement spot which lies partially on a peripheral surface of the semiconductor wafer and partially on a portion of the susceptor lying outside the semiconductor wafer, the emissivities of the semiconductor wafer and the susceptor being different; measuring the amplitude of a fluctuating measurement signal from the pyromer obtained from a test semiconductor wafer which is centered with respect to the center of radius of the circular pocket or within an acceptable degree of eccentricity from being centered, to establish an acceptable maximum amplitude; measuring the amplitude of a fluctuating signal from the pyrometer obtained from the semiconductor wafer to be thermally treated, and if the amplitude so measured exceeds the acceptable maximum amplitude, identifying the semiconductor wafer to be thermally treated as positioned radially incorrectly within the circular pocket, wherein the orientation of the measurement spot is such that from 10-90% of the area of the measurement spot lies on the test semiconductor wafer within a distance r 1 from the center of radius of the circular pocket.