HEAVY BORON DOPING IN LOW-TEMPERATURE SI PHOTOEPITAXY

Heavy boron doping of up to 1.5 x 1020cm-3was achieved in a photoepitaxial layer grown at 650°C. Under UV irradiation, the doped carrier concentration was independent of the diborane flow rate in the heavily doped region and doped boron atoms were completely activated up to L5 x 1020 cm-3. Without UV irradiation, no single crystals were grown and very few boron atoms were activated in the heavily doped region. We studied the crystal quality using Raman scattering spectroscopy and found that, under UV irradiation, single crystals could be grown up to 1.5 x 1020cm-3. The boron atom activation ratio depended strongly on the crystal quality. UV irradiation markedly increased carrier doping efficiency due to photo-enhancement of the diborane vapor phase reaction, which we studied using FTIR and the surface reaction of adsorbed species. The electrical properties of low-temperature photoepitaxial layer with heavy boron doping were studied using a bipolar transistor. Excellent device characteristics were achieved. Low-temperature photoepitaxy also produced very abrupt boron profiles. © 1990, The Electrochemical Society, Inc. All rights reserved.