Imaging doped regions in a semiconductor with very low energy SEM and Auger electrons

ABSTRACT: Regions of n+ and p+ semiconductors doped to 2.5 x 1020 and 8xl019 cm"3 respectively on n-type silicon substrate have been imaged in a scanning electron microscope modified for use into a cathode lens mode operating in the region of 110,000 eV. The highest contrast with respect to that of the n-type silicon has been obtained from the n+ region followed by the p+. Further, the n+ area shows a maximum contrast at about 5-20 eV, while the contrast from the p+ area shows a maximum at about 300 eV. Imaging of the sample in UHV was also investigated in parallel with AES of the differently doped regions. The AES revealed the presence of a graphitic carbon surface layer across the sample. The effects of altering the surface conditions with a Cr surface layer were also investigated.