Fabrication and characterization of bipolar transistors within-situ doped low-temperature (800°C) epitaxial silicon

The authors report the fabrication of bipolar transistors at a maximum process temperature of 800°C, utilizing in situ doped low-temperature epitaxial silicon deposited by ultralow-pressure chemical vapor deposition (U-LPCVD), and their subsequent characterization. The epitaxial silicon layers form the collector, base, and emitter layers. To attain a high donor concentration in the epitaxial emitter layer, the U-LPCVD process is plasma enhanced. Transistors having excellent DC characteristics down to collector currents of ~10 pA/μm² are obtained, which indicates that the bulk quality of the epitaxial films is good enough for device fabrication