UHV/CVD n--type silicon epitaxy used for SiGe HBT device

n--type silicon epitaxial layers were grown on arsenic-doped n--type silicon substrate by ultra-high vacuum chemical vapor deposition (UHV/CVD). The transition region thicknesses of the Si layers grown under different PH3 flux and different growth temperatures were investigated by spread-resistance probe. Results show that the growth temperature has remarkable influence on the arsenic diffusion from the Si substrate. The thickness of the transition region was 0.16 μm grown at 700°C and 0.06 μm at 500°C, respectively. Moreover, the dopant profiles were very abrupt. X-ray diffraction investigation of the Si layer grown at 700°C shows that the quality of Si layer is very high. Silicon-germanium hetero-junction bipolar transistor (SiGe HBT) was fabricated by a revised double-mesa polysilicon-emitter process. Tests show that the CB-junction breakdown characteristic of the SiGe HBT is very hard, and the leakage current is only 0.3 μA at VCB=14.0 V. The SiGe HBT device also had good output performance with current gain β=60 at VCE=5 V and IC= 3 mA.