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Highly Selective Plasma Etching of N+ Polysilicon

IP.com Disclosure Number: IPCOM000049075D
Original Publication Date: 1982-May-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Bennett, RS: AUTHOR

Abstract

This article relates generally to plasma etching of semiconductors and more specifically to a highly selective plasma etching of n/+/ polysilicon relative to p/+/ or undoped polysilicon and SiO(2) using CCl(2)F(2) as an etching gas.

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Highly Selective Plasma Etching of N+ Polysilicon

This article relates generally to plasma etching of semiconductors and more specifically to a highly selective plasma etching of n/+/ polysilicon relative to p/+/ or undoped polysilicon and SiO(2) using CCl(2)F(2) as an etching gas.

Highly selective plasma etching of n/+/ polysilicon with respect to p/ / or undoped polysilicon and SiO(2) may be obtained in a flexible diode reactor similar to that shown in the above figure using CCl(2)F(2) as an etching gas. High selectivity of 25 to 1 is achieved in the reactor by maintaining a low voltage between the recessed substrates and the plasma which forms between the perforated top electrode and the aluminum substrate electrode. Etching is carried out with the RF power applied to the perforated top electrode, while the aluminum substrate electrode is allowed to float. Using 25 millitorr of CCl(2)F(2) (5 sccm 0.27 watt per cm/2/ to the perforated top counter electrode) the plasma etch rate n polysilicon is 50 nm per minute, whereas the etch rate of p/+/ or undoped polysilicon is about 2 nm per minute. The etch rate of SiO(2) in the same etching mode is about 1 nm per minute. The main advantage of the present process over known processes which use C(2)F(6) + Cl(2) is that the use of CCl(2)F(2) eliminates problems encountered in using a toxic, corrosive gas. An additional advantage of the present process is that the selectivity is higher (25 to 1 versus 16 to 1 using C(2)F(6...