Electron-Beam Studies of Schottky-Barrier Detector Surfaces

The electron beam technique used by Czaja to analyze defects in diode structures has been applied to the analysis of surface anomalies occurring in Schottky-barrier particle detectors. An output map of the detector surface showing local variations in sensitivity was obtained in this manner. It was discovered that characteristic anomalies give characteristic displays. Specifically, SEM analysis was useful in detecting: 1. Chemical contamination of the detector surface. 2. Mechanical damage of the detector´s semiconductor wafer substrate, 3. Damage introduced in semiconductor surface preparation, 4. Radiation damage, and 5. Defective surface metallization. The possibly damaging effects of scanning electron beam irradiation are discussed. A general limit on beam current and magnification setting for a 20 kev beam is given. If this limit is not exceeded, the technique does not, in itself, add artifacts to the electron beam technique display. Methods are developed which enable the quantification of the extent and severity of surface damage. How these methods can be used to eliminate some common processing problems is also covered.