Abstract
Pancake reactors operated at low temperatures and reduced-pressures have been used for silicon selective epitaxial growth (SEG). In general, dichlorosilane (DCS) is the silicon source gas, hydrogen is the carrier gas, and HCl prevents the formation of polysilicon on the silicon dioxide. An investigation of growth rate, uniformity, and doping characteristics of SEG silicon grown at reduced pressures between 40 and 150 Torr and temperatures between 820°C and 1020°C in a pancake reactor is presented. The dependences of growth rates and uniformities on growth temperatures, pressures, and doping were studied. Improvement in thickness uniformity across the wafer was achieved by lowering the deposition temperature and pressure. In-situ phosphorus doping in the range of 1016-1018P atoms/cm3 was accomplished by introducing phosphine (PH3) gas into the reactor during epitaxial deposition. Doping concentration, which was determined by three different methods, increased with phosphine inject set point. Also, higher phosphorus concentrations were obtained at lower deposition temperatures and/or pressures. Diodes and bipolar transistors identically fabricated in undoped SEG and in bulk silicon were used to characterize the SEG material quality. Since average ideality factors, leakage currents, breakdown voltages, and current gains extracted from 970°C-40T SEG devices were similar to those of substrate devices, the material quality of the SEG deposited at 970°C and 40 torr was indicated to be as good as the bulk silicon.
Date of this Version
April 1992
Comments
Page 32 is missing from original document as well as copy held in the Siegesmund Engineering Library of Purdue University.