Selective Epitaxial/Quasi-Epi Emitters
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
In the manufacture of polysilicon emitters in semiconductor devices the conventional method involves a blanket poly-Si deposition and a subsequent lithographic masking to remove it from unwanted regions. This article proposes to selectively deposit silicon in the emitter opening only. This would lead to process simplification since it would eliminate the need for the lithography and etch steps. Under conventional practices the N+ poly contact 1 (Fig. 1) to the emitter 4 is deposited using an homogeneous chemical vapor deposition (CVD) process to deposit the poly-Si. Since the poly films grow over the whole surface of the wafer, a mask-and-etch step is needed to define the edge of the N+ poly. The spacing 5 between the emitters is limited by the alignment tolerance of the N+ poly and the metal 2.