Method for making high speed poly-emitter bipolar transistor

Details Method for making high speed poly-emitter bipolar transistor Method for making high speed poly-emitter bipolar transistor

1995-12-14

1997-07-01

Niebling, John

Fishing, trapping, and vermin destroying

437 59, 437186, 148DIG9, 148DIG10, H01L 21265

Patent

active

056438095

ABSTRACT:
Spacers are formed on the inside walls of a narrow silicon loss trench of a poly-emitter type bipolar transistor structure so that at most a narrow strip on the bottom of the trench receives high concentration doping when an extrinsic base region of the bipolar transistor is being doped. The narrowness of the exposed silicon surface which is etched to form the silicon loss trench slows vertical etching and thereby facilitates the formation of a shallow trench. The narrowness of the strip on the bottom of the trench which receives high concentration doping causes slow vertical diffusion of dopants. As a result, the highly doped link region which extends downward from the bottom of the trench does not extend downward much farther than the base region. A high cutoff frequency is therefore achievable by reducing the distance between the bottom of the base region and the top of the buried layer without decreasing the base-to-collector breakdown voltage.

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