QUANTITATIVE-DETERMINATION OF THE CARRIER CONCENTRATION DISTRIBUTION IN SEMICONDUCTORS BY SCANNING IR ABSORPTION - SI

A contactless method is reported for the quantitative measurement of spatial variations of the free carrier concentration m semiconductors with a resolution of about 20 μm and a sensitivity better than 1%. The method is based on free carrier absorption in the infrared region where other absorption processes are negligible. In the experimental arrangement a CO2 laser beam passes through a semiconductor wafer mounted on a stage with a calibrated x-y motion; detection of the transmitted light through the desired area of the wafer about 20 μm in diameter is achieved by employing an IR microscope in conjunction with an IR detector. The principles and applications of the method are discussed using n- and p-type silicon. Carrier concentration profiles obtained by scanning IR absorption were found to be in good agreement with those obtained by standard spreading resistance measurements. © 1979, The Electrochemical Society, Inc. All rights reserved.