7-MASK SELF-ALIGNED SIGE BASE BIPOLAR-TRANSISTORS WITH F(T) OF 80-GHZ

A 7-mask self-aligned SiGe base bipolar transistor has been newly deve loped. This transistor offers several advancements to a super self-ali gned selectively grown SiGe base (SSSB) transistor which has a selecti vely grown SiGe-base layer formed by a cold-wall ultra high Vacuum (UH V)/CVD system. The advancements are as follows: (1) a BPSG-filled arbi trary-width trench isolation on a SOI is formed by a high-uniformity C MP with a hydro-chuck for reducing the number of isolation fabrication steps, (2) polysilicon-plug emitter and collector electrodes are made simultaneously using an in-situ phosphorus-doped polysilicon film to decrease the distance between emitter and collector electrodes and als o to reduce the fabrication steps of the elecrodes, (3) a n(+)-buried collector layer is made by a high-energy phosphorus ion-implantation t echnique to eliminate collector epitaxial growth, and (4) a germanium profile in the neutral base region is optimized to increase the f(T) v alue without increasing leakage current at the base-cellector junction . In the developed transistor, a high performance of 80-GHz f(T) and m ask-steps reduction are simultaneously achieved.