UHV/CVD Low-Temperature Si Epitaxy Used for SiGe HBT

摘要

Low-temperature-epitaxy n~--type silicon layers were grown on arsenic-doped n~+-type silicon substrate by using ultra-high vacuum chemical vapor deposition (UHV/CVD). The transition region thickness of the Si layers grown under different PH_3 flux and different growth temperature were investigated by spreading resistance probe. Results showed that the growth temperature had remarkable influence on the arsenic diffusion from the Si substrate. The thicknesses of the transition region were 0.16 μm. grown at 700℃ and 0.06 μm grown at 500℃, respectively. Moreover, the dopant profiles were very abrupt. X-ray diffraction investigation of the epitaxial Si layer showed the quality of Si layer was very high. SiGe HBT device was fabricated by using a revised double-mesa polysilicon-emitter process. Tests show that the CB-junc-tion breakdown characteristic of the SiGe HBT is very hard, and the leakage current is only 0.3 μA under a reverse voltage of - 14.0 V. The SiGe HBT device had also good output performance, and the current gain is 60.