Sub-20 ps ECL circuits with high-performance super self-aligned selectively grown SiGe base (SSSB) bipolar transistors

This paper describes a high maximum frequency of oscillation f_max self-aligned SiGe-base bipolar transistor technology, based on a self-aligned selective epitaxial growth (SEG) technology including graded Ge profile in an intrinsic base and link-base engineering using a borosilicate glass (BSG) sidewall structure. The transistor is a new self-aligned transistor, which we call a Super Self-aligned Selectively grown SiGe Base (SSSB) bipolar transistor. The 1st step of the annealing (800°C, 10 min) was performed for the diffusion of boron from the BSG film, before the deposition of an emitter polysilicon film. The 2nd step of the annealing (950°C, 10 sec) of emitter drive-in was carried out, which enabled us to obtain sufficient current gain using in-situ phosphorus doped polysilicon as an emitter electrode. Sheet resistance for a link-region more than one order lower than that of the epitaxial intrinsic base was obtained after heat treatment. Base profile (boron and Ge) design, and the 2-step annealing technique have realized cut-off frequency f_T of 51 GHz and f_max of 50 GHz. ECL circuits of 19-psec gate delay have been achieved