Selektives, epitaxiales Silizium für eine Innen/Außen-Basisverbindung

摘要

In a bipolar device, selective epitaxial silicon provides an improved intrinsic-extrinsic base line 34. A trench (29, Fig. 2 not shown) physically separates an intrinsic base portion 20 and extrinsic base portion 21. The trench includes sidewalls having a thin oxide layer formed thereon. The bottom of the trench is exposed during processing. A shallow link 34 between the intrinsic-extrinsic regions of a bipolar transistor base is formed by depositing a heavily boron doped layer of silicon on the exposed portion of the trench. During subsequent processing, including rapid thermal anneal, there is some boron out-diffusion which forms a shallow diffused intrinsic-extrinsic base link. <IMAGE>