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A comprehensive study on the effect of extrinsic base optimization on the RF performance of an advanced SiGe HBT is presented. An optimized extrinsic poly base with its interface to the epi-base passivated by boron ions is demonstrated to enhance the f/sub max/ and the current gain almost two times and to reduce the low-frequency 1/f noise ten times and noise figure (NF) 0.5 dB, achieving f/sub max/ of 45 GHz, 1/f noise corner frequency of 700 Hz at I/sub B/=1.0 /spl mu/A, NF/spl les/1.0 dB at 900 MHz. Early voltage V/sub A/ of /spl ges/200 V is achieved, while maintaining a BV/sub CEO/ of /spl ges/8.0 V.
Date of Publication: Sept. 1997