Abstract
SiGe HBTs have achieved record peak f T values [1-2] and impressive digital circuit ECL RO delays [3] but no analog circuit results have been reported. In this work we investigate the leverage of SiGe HBTs for analog circuits by optimizing the Ge-profile for a high βV A product and high f T under the constraint of breakdown voltage and effective strain of the SiGe layer. Analytical calculations of β, V A , and f T of SiGe-HBTs as a function of Ge profile predict the largest performance advantage over Si BJTs for the most steeply graded Ge profile. SiGe-HBT transistors are fabricated with βV A products of 6160 V, BV CEO of 3.5 V and f max of 46 GHz, and compared to Si-BJTs fabricated with the same process. Digital performance is benchmarked by an ECL ring oscillator delay of 17.2 psec. The leverage for analog technology is demonstrated by fabrication of a 1GHz SiGe-HBT 12 bit Digital to Analog Convertor.