US 5,702,978 A · Sloped silicon nitride etch for smoother field oxide edge

Abstract

A method of fabricating an integrated circuit on a silicon substrate in such a manner as to avoid the requirement of over-etching the polysilicon usually necessary to prevent shorting of adjacent devices by poly filaments caused by deep polysilicon pockets in notch areas created in the field oxide during its growth. The notches are prevented by forming the nitride mask with sloped rather than perpendicular side walls. The sloped side walls present less resistance to the growing oxide than does the usual perpendicular wall and thus does not dig into the growing oxide to form the notches. The edge of the resultant field oxide is therefore smoother, permitting easier and more complete removal of the polysilicon without the need for over-etching.

Claims8

Dependent claims

A method for providing a smooth field oxide edge in the fabrication of an integrated circuit on a substrate comprising the steps of:

depositing a layer of nitride on the substrate;
etching the nitride away in those areas where active devices are not to be formed, said etching step comprising;
supplying CF.sub.4 and CHF.sub.3 gases into the etcher at a ratio of CF.sub.4 :
CHF.sub.3 =1:3;
etching the nitride at least until the end point;
growing a field oxide on the substrate adjacent to said edge surface of the nitride;
removing the nitride;
applying gate material over the surface of the field oxide;
depositing a pattern of photoresist on the gate material in areas where gates are to be located;
and
etching the gate material away in those areas not covered by the resist.

8 more elements

Dependencies are inferred from the claim text.

Sloped silicon nitride etch for smoother field oxide edge

Life of this patent

Sloped silicon nitride etch for smoother field oxide edge

Life of this patent

Abstract

Claims8