Submicrometer Si and Si-Ge Epitaxial-Bas Double-Poly Self-Aligned Bipolar Transistors

Fabrication, device profiles, and electrical characteristics of epitaxial-base double-poly self-aligned bipolar transistors are presented. The intrinsic-base regions in the present device structures reside above the silicon surface and were formed using boron-doped low-temperature epitaxially (LTE)-grown Si or Si-Ge layer to achieve a narrow intrinsic-base width (< 60 nm) and a low base pinch resistance (< 5 K/sq) simultaneously. As a result of the raised base using LTE and the preservation of the integrity of this layer by minimizing the dopant diffusion during the subsequent processing steps, walled-emitter devices with excellent electrical characteristics have been obtained. © 1991 IEEE