Low temperature in-situ phosphorus doped single-crystal silicon emitters for application in SiGe HBTs

SiGe Heterojunction Bipolar Transistors (HBTs) require low temperature processing in order to minimize Boron-out diffusion from the base region. In this paper a novel technique of producing low temperature in-situ Phosphorus doped single-crystal silicon emitters for application in SiGe HBTs is presented. The single-crystal silicon was deposited at a temperature of 670°C in a UHV-compatible LPCVD cluster tool. Gummel plots of the fabricated transistors show very ideal base and collector current characteristics. An ultra low emitter resistance of 6.6 Ω.μm² was also obtained. The very low emitter resistance is due to very low oxygen dose of 5.3×10¹³ cm^-2 at the single-crystal silicon emitter/silicon substrate interface. The commercial Silvaco TCAD ATHENA and ATLAS were used to model the DC characteristics of the transistor to validate the results.