MBE-GROWN SIGE BASE HBT WITH POLYSILICON-EMITTER AND TISI2 BASE OHMICLAYER

Using Si/SiGe heteroepitaxy grown by solid-sources (SS) molecular beam epitaxy (MBE) on LOGOS-patterned wafers, an n-p-n Si/SiGe/Si heteroju nction bipolar transistor (HBT) which is isolated by a polysilicon-fil led trench has been fabricated. Unlike other SiGe HBTs using a metalli c salicide process, in this proposed device a titanium disilicide (TiS i2) base electrode layer is formed by deposition and patterning of an amorphous TiSi2x (x = 0-0.9) layer on the SiGe base layer using select ive wet etching. In view of a lower thermal budget furnace annealing a t 840 degrees C has only been applied for the drive-in and activation of arsenic (As) implanted in the polysilicon-emitter. The Si/Si0.85Ge0 .15/Si n-p-n HBT with a 1 x 4 mu m(2) mask size emitter typically show s a common-emitter current gain of 118, an Early voltage in the range of 150-170 V, a breakdown voltage BVceo of 7.8 V, a unity current gain frequency f(T) of 20 GHz, and a maximum oscillation frequency f(max) of 15 GHz. Considering the theoretical limit of f(T) vs BVceo, the per formance of our device is near the limit and demonstrates a potential for high frequency analog IC applications. Copyright (C) 1996 Elsevier Science Ltd