Self-aligned bipolar fabrication process.

摘要

Bipolar transistors are made by forming a base window through a dielectric layer overlying a substrate. In the wall of the base window a polysilicon layer is exposed. Subsequent processing involves the forming of various sidewall spacers within the base window to define the base and emitter regions. Since spacer formation requires no lithographic processing, there is no need to define very small features, such as the emitter, lithographically. The smallest feature which needs to be defined lithographically is the original base window which may be between 1 and 2 microns for emitter widths of 0.5 um or less.