Process for control of the shape of the etch front in the etchin

Details Process for control of the shape of the etch front in the etchin Process for control of the shape of the etch front in the etchin

1998-08-31

2000-06-13

Utech, Benjamin L.

Semiconductor device manufacturing: process

Chemical etching

Vapor phase etching

438719, H01L 213065

Patent

active

060749547

ABSTRACT:
The present disclosure pertains to our discovery that the use of a particular combination of etchant gases results in the formation of a substantially flat etch front for polysilicon etching applications. In general, the process of the invention is useful for controlling the shape of the etch front during the etchback of polysilicon. Typically, the process comprises isotropically etching the polysilicon using a plasma produced from a plasma source gas comprising a particular combination of reactive species which selectively etch polysilicon. The plasma source gas comprises from about 80% to about 95% by volume of a fluorine-comprising gas, and from about 5% to about 20% by volume of an additive gas selected from a group consisting of a bromine-comprising gas, a chlorine-comprising gas, an iodine-comprising gas, or a combination thereof. One preferred mixture is SF.sub.6, Cl.sub.2 and HBr. A preferred method of the invention, used to perform recess etchback of a polysilicon-filled trench in a substrate, comprises the following steps: a) providing a trench 3 formed in a semiconductor structure, wherein the structure includes a substrate 2, at least one gate dielectric layer 6 overlying a surface of the substrate, and at least one etch barrier layer 8 overlying the gate dielectric layer; b) forming a conformal dielectric film 10 overlying the etch barrier layer and the sidewall and bottom of the trench; c) filling the trench with a layer of polysilicon 12 which overlies the conformal dielectric film; and d) isotropically etching the polysilicon back to a predetermined depth within the trench using a plasma produced from the invention plasma source gas. Also disclosed herein is a method of forming a trench capacitor in a single-crystal silicon substrate, the trench capacitor including a dielectric collar and a buried strap.

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