Undercut Contacts For Poly Si Base
Original Publication Date: 1980-Jan-01
Included in the Prior Art Database: 2005-Feb-12
In the manufacture of polysilicon (poly Si) base transistors, a thick layer of poly Si for base contacts is often deposited directly on silicon. The layer is then reactive ion etched (RIE) to define edges of the poly Si base. This requires a tight control of the RIE step. The improved technique described here alleviates this requirement by the use of an intermediate wet etch step to undercut a first poly Si layer prior to the deposition of a second poly Si layer. By defining the size of the poly Si to single crystal silicon contact with undercut, the base to collector junction area is reduced.