Process for performing variable selectivity polysilicon etch
AssigneeHarris Corporation
InventorMark A. Pipkin
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Abstract
A method for controllably varying the selectivity of reactive etching process for etching a polysilicon film, involves the addition of an adjustable amount of oxygen (O.sub.2) to a chlorine based chemistry (e.g. Cl.sub.2, HCl) during the etching process. The adjustable amount of oxygen permits the selectivity to be varied from a low to moderate rate at the beginning of the etch and through most of the film thickness to as high a selectivity as is required for overetch, to allow anisotropic removal of polysilicon without penetrating thin oxide. Selectivity is effectively proportional to the oxygen concentration and may be varied from a low to moderate selectivity value (e.g. 20:1) to a high selective value (e.g. 100:1) of polysilicon oxide etch rate in a controlled manner.
Claims14
A method of controllably enhancing the etch rate of a layer of polysilicon relative to the etch rate of an oxide layer each of which layers is to be simultaneously exposed to a prescribed chlorine chemistry-based etch system, comprising the step of controllably modifying the composition of said chlorine chemistry-based etch system by controllably introducing thereinto an adjustable amount of oxygen.
A method of manufacturing a semiconductor device comprising the steps of:
- (a) selectively forming an insulator layer on a surface of semiconductor substrate so as to expose said surface through an aperture in said insulator layer;
- (b) forming a thin oxide layer on said exposed surface of said substrate:
- (c) forming a layer of polysilicon on said insulator layer and on said thin oxide layer;
- (d) exposing a selected portion of the polysilicon layer and thin oxide layer resulting from step (c) to an anisotropic chlorine chemistry-based etch system;
- and
- (e) during step (d) controllably introducing oxygen into said anisotropic etch system so as to increase the ratio of the etch rate of said system for polysilicon to the etch rate of said system for oxide and thereby remove said selected portion of the polysilicon layer without effectively removing said thin oxide layer.
Dependencies are inferred from the claim text.