Electrical characterization of junctions and bipolar transistors formed with in situ doped low-temperature (800°C) epitaxial silicon

The results of characterization of junctions and bipolar transistors formed with in situ doped low-temperature (800°C) epitaxial silicon are presented. The epitaxial silicon layers were deposited by ultra-low pressure chemical vapor deposition (U-LPCVD) preceded by an in situ Ar sputter clean, which makes possible 800°C fabrication of bipolar transistors. For emitter layer depositions, the U-LPCVD process was plasma enhanced to attain high donor incorporation. Three typical structures of bipolar transistors (A: with epitaxial collector, base, and emitter; B: with epitaxial base and emitter; and C: with epitaxial base) were fabricated and compared in this study. The junction characteristics of the fabricated transistors were also investigated. Functional transistors were obtained for all three structures. Ideality factor of the junctions formed within the epitaxial silicon were near unity (1.01). These results support the claim that the bulk quality of the low-temperature epitaxial silicon is good enough for device application