IMAGING SEMICONDUCTOR WAFERS USING PHOTOLUMINESCENCE

A facility for producing photoluminescence (PL) images of semiconducto r wafers at cryogenic temperatures is described. A custom-designed liq uid helium cryostat capable of accepting 50-mm-diam wafers is used tog ether with a scanning optical table for PL excitation and collection. Spectral analysis is achieved by the use of a CCD detector mounted on a standard grating spectrometer. The configuration used enables a full spectrum to be recorded for each point on a wafer with a spatial reso lution of approximately 100 mu m. The spectral information may be used to produce images of the total PL intensity, the peak PL intensity, a nd the wavelength at which the peak intensity occurs. Typical PL maps are presented to illustrate the quality of the information.