A 60-GHz fT super self-aligned selectively grown SiGe-base (SSSB) bipolar transistor with trench isolation fabricated on SOI substrate and its application to 20-Gb/s optical transmitter ICs

A 60-GHz cutoff frequency (f_T) super self-aligned selectively grown SiGe-base (SSSB) bipolar technology is developed. It is applied to 20-Gb/s optical fiber transmitter ICs. Self-aligned bipolar transistors mutually isolated by using a BPSG-filled trench were fabricated on a bond-and-etchback silicon-on-insulator (SOI) substrate to reduce the collector-substrate capacitance C_CS. The SiGe base was prepared by selective epitaxial growth (SEG) technology. A 0.4-μm wide emitter was used to reduce the junction capacitances. The maximum cutoff frequency f_T and the maximum frequency of oscillation f_max were 60 and 51 GHz, respectively. By using this technology, Si-ICs for an optical transmitter system were made, such as a selector (a multiplexer without input and output retiming D-type flip-flops (D-F/Fs)), a multiplier, and a D-F/F. An internal high-speed clock buffer circuit achieves stable operation under a single clock input condition in the selector and the multiplier ICs. Their stable operation was confirmed up to 20 Gb/s. The selector IC for data multiplexing operates at over 30 Gb/s