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Selective Anisotropic Reactive Ion Etch Process for Polysilicon Etching

IP.com Disclosure Number: IPCOM000040896D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Schulz, R: AUTHOR

Abstract

A process has been proposed to provide improved selectivity in reactive ion etching (RIE) used in the production of semiconductor devices. Trichlorofluoromethane, CCl3F, and air make up the process gas used to achieve the results.

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Selective Anisotropic Reactive Ion Etch Process for Polysilicon Etching

A process has been proposed to provide improved selectivity in reactive ion etching (RIE) used in the production of semiconductor devices. Trichlorofluoromethane, CCl3F, and air make up the process gas used to achieve the results.

In the process an intermediate pressure and relatively low power density power are used. These are such that the degree of ion bombardment is limited so as to minimize the SiO2 etch rate but is still of sufficient intensity to take full advantage of the ion assisted component of the silicon etch rate. When higher pressures are used at the selected power level, the silicon rate will fall relatively faster than the SiO2 rate. At a lower pressure and the same power, the SiO2 rate will increase relatively faster than the silicon rate.

Etching of intrinsic and P+ polysilicon is very anisotropic with near 90o profiles and less than 500 o total etch bias as seen on 0.5m wide poly gates. The N+ poly will undercut since the low energy neutrals can successfully etch N+ poly but are unable to etch P+ or intrinsic poly without the ion assisted component.

The proposed process is considered non load dependent with no more than a 10% variation in silicon etch rate and an etch rate ratio from 1/4 wafer to (15) 125 mm wafer silicon load. It is compatible with other selective processes such as CF4/H2 and is much more selective than other processes using fluorocarbons. The process is...