Use of a clean up step to form more vertical profiles of polycrystalline silicon sidewalls during the manufacture of a semiconductor device

摘要

Disclosed is a process step performed during a wafer etch which allows for the formation of more vertical sidewalls. During a conventional etch step of a material such as oxide, oxygen is released into the etch chamber, which is known to adversely affect the vertical profile of the sidewalls. The oxygen is known to combine with silicon and HBr, which are present as gasses within the etch chamber during the subsequent poly etch, to deposit on the poly sidewalls. For this reason subsequent etches are conventionally performed in a separate etch chamber. The disclosed step introduces an oxygen-scavenging gas into the etch chamber prior to the subsequent etch of the polycrystalline silicon. The oxygen-scavenging gas combines with the liberated oxygen with the application of plasma energy to produce an inert volatile gas which can be pumped from the etch chamber and therefore not adversely affect subsequent etches. Claimed oxygen-scavenging gasses include C2F6, CF4, CHF3, and BCl3.