Nondestructive and Noncontact Evaluation of Semiconductors by Photothermal Radiometry

We have developed a new photothermal-radiation (PTR) microscope for noncontact and nondestructive evaluation of defects in semiconductors. We measured PTR topographs of a GaAs wafer and a thermally oxidized Si wafer with a HgCdTe infrared detector which is highly sensitive to the radiation in the wavelength range from 8 to 13 µm. We found that the PTR topograph has a correlation with the distribution of surface damage. We also unexpectedly found that the PTR signal decreases at a deep scratch in contrast to the increase of the photoacoustic signal reported previously.