| abstract |
SUMMARY OF THE INVENTION The apparatus and method of the present invention provides a method for diffusion modulation (e.g., one or more of mobility, doping, and lifetime) used to evaluate a semiconductor wafer. (Without generating carrier waves). The measurement is performed on a small area for use on a wafer having a pattern for an integrated circuit die. The measurement is based on a measurement of the reflectivity, for example as a function of the carrier concentration. In one embodiment, the semiconductor wafer (106) is illuminated with two beams (151, 152). One of the beams has photons of higher energy than the bandgap energy of the semiconductor and the other has photons of energy near or below the bandgap. The diameter of the two beams relative to each other is changed, for example, to extract additional information about the semiconductor material, for use in measuring lifetime. |