Emitter Fabrication for NPN Transistors
Original Publication Date: 1985-Feb-01
Included in the Prior Art Database: 2005-Feb-18
This article relates generally to integrated circuit fabrication and, more particularly, to the construction of emitter junctions in bipolar NPN transistors. Emitter junctions of high performance bipolar transistors require shallow, highly doped regions for minimal resistance and base current when scaled for minimum feature size. The junctions have usually been constructed by outdiffusion of arsenic from a layer of polysilicon. Arsenic, however, permits sharp profiles and low resistivity only at high concentrations and diffuses out at increasing rates with increasing concentrations. Heavier dopants, such as antimony or bismuth, can be implanted in the silicon to define the emitter depth with greater accuracy.