Förfarande vid tillverkning av bipolär transistorstruktur

摘要

The present disclosure describes a method to reduce the base-collector capacitance swing and increase the collector-to-base breakdown voltage in a bipolar high-frequency transistor. First a highly doped silicon substrate (1) of a first doping is selected for forming a transistor emitter region. Then layers (5, and 6, 7) are deposited with a second and a first doping for forming a base/collector structure. Subsequently a collector mesa structure is formed by removing silicon on base contact areas using a photoresist mask on top of a layer of for instance an oxide (9) so that the additional layers also serve as a mask for the silicon etch. An etching method is selected to facilitate the form of the collector to be made narrow closer to a collector contact surface, thereby creating a bipolar collector-up high frequency transistor with a shaped collector. This improves both the capacitance swing and the breakdown voltage. The present disclosed method describes the manner in which this is implemented for producing a discrete mesa-etched RF power transistor.