Optimal extrinsic base fabrication for high performance SiGe HBTs for RF communication applications

SiGe HBTs with low 1/f noise, low base resistance (for low noise figure and high f/sub max/) and high intrinsic gain and breakdown voltage provide design leverage for RF communication applications. This work describes an optimal extrinsic base fabrication for SiGe HBTs, achieving f/sub max/ increased 2 times, R/sub B/ reduced 50%, noise figure at 900 MHz reduced about 0.5 dB, 1/f noise reduced 10 times, and current gain increased 2 times. Breakdown voltage V/sub CEO/ is larger than 8.0 V, sufficient for 3 V operations. Those results have been achieved at no additional mask or process steps to the conventional base-line process.