A Self-Aligned Double Poly-Si Process Utilizing Non-Selective Epitaxy of SiGe:C for Intrinsic Base and Poly-SiGe for Extrinsic Base

摘要

A self-aligned double poly-Si process using non-selective epitaxy of SiGe:C for the intrinsic base and a dual stack of poly-Si and poly-SiGe for the extrinsic base is presented. Self-alignment of the extrinsic base is obtained by detailed control of the emitter window etch procedure. The etch of the extrinsic base is endpointed at the poly-Si/poly-SiGe interface, and is followed by a timed etch of the SiGe film. Due to the selectivity towards Si, the etch can be stopped at the epitaxial Si surface. The SiGe:C epitaxy is obtained using ultra-high vacuum chemical vapor deposition (UHV/CVD). As a result of the slightly higher growth rate of the epitaxial film compared to the polycrystalline material, an almost planar surface could be obtained. Working devices have been verified by electrical measurements.