Integratable and low base resistance Si/Si/sub 1-x/Ge/sub x/ heterojunction bipolar transistors using selective and non-selective rapid thermal epitaxy

Abstract

We report a new SVSiGe HBT device structure using selective and non-selective rapid thermal epitaxy. The structure has the potential to simultaneously provide for high level integration and a high Ge fraction strained alloy base which allows high base doping. We used an in-situ As doped polysilicon emitter contact to provide low RE (9 to 12 for AE = 0.5 x 10 pm2) without the enhanced diffusion effects associated with direct implantation or phosphorous doped poly emitters, In addition, we studied the effects of the extrinsic base implant position on the device I-V characteristics, junction capacitances, and high frequency performance. The collector current increased by over 3 decades as the extrinsic base implant position moved from the single crystal region to an adjacent poly region due to the containment of damage. Sparameter measurements of a 0.5 x 10 pm2 device yielded a cutoff frequency of 54 GHz for VCE = 1.5 V and IC = 14.8 mA.

Extrinsic base optimization for high-performance RF SiGe heterojunction bipolar transistors

“…High-performance SiGe HBT's were fabricated using a submicron BiCMOS compatible technology [7], [8]. front-end isolation formation, epitaxial SiGe bases were non selectively grown in an ASM RPCVD reactor with germane and diborane added to a 700 C dichlorasilane process at a pressure of 60 mTorr.…”

“…For an RF device, the extrinsic base, including the interface, is equally critical as the intrinsic base. There was a study on using the extrinsic base implant to eliminate a p-n junction formation in the extrinsic base of the SiGe HBT [7]. However, the effect of the extrinsic base and the interface on the SiGe HBT RF performance has not been reported.…”