Variation of diffusion length with processing in dielectrically isolated π-silicon tubs

The variation of minority-electron diffusion length with processing in dielectrically isolated π-silicon tubs is investigated using electron-beam-induced current measurements. The analysis of these measurements is complicated by the six boundary conditions on the π-silicon. The diffusion lengths measured in virgin π-tub silicon are ≤ 250 µm while those in π-silicon undergoing a phosphorus getter are >> 250 µm. The determination of exact values for the diffusion lengths as a function of processing are not possible without a more complete understanding of the parasitic effects of the inversion region at the tub walls. Trends in the diffusion lengths are indicative of trends in the carrier lifetime, which are critical in the high-voltage applications for silicon tubs.