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Reactive Sputter Etching Process for Forming Deep Isolation Trenches With Vertical Sidewalls

IP.com Disclosure Number: IPCOM000042176D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Gray, RK: AUTHOR [+3]

Abstract

Deep isolation trenches with vertical sidewalls are essential for increasing the device density and improving the device performance of VLSI chips. The reactive gas mixtures used for etching deep trenches result to a lesser or greater extent in an enhanced lateral etching at the blanket N+ sublayers, as shown in the Fig. 1 photograph. These trenches are more difficult to fill with chemical vapor deposited films, such as polysilicon, because the conformal coating leaves a void in the film at the widest point in the trench. Subsequent oxidation after planarization of the film can lead to oxidation in the void which can cause an increase in dislocation defects in the adjacent single crystal silicon due to stress.

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Reactive Sputter Etching Process for Forming Deep Isolation Trenches With Vertical Sidewalls

Deep isolation trenches with vertical sidewalls are essential for increasing the device density and improving the device performance of VLSI chips. The reactive gas mixtures used for etching deep trenches result to a lesser or greater extent in an enhanced lateral etching at the blanket N+ sublayers, as shown in the Fig. 1 photograph. These trenches are more difficult to fill with chemical vapor deposited films, such as polysilicon, because the conformal coating leaves a void in the film at the widest point in the trench. Subsequent oxidation after planarization of the film can lead to oxidation in the void which can cause an increase in dislocation defects in the adjacent single crystal silicon due to stress. This enhanced etching at the N+ sublayer can be avoided by etching at high power and low pressure (about 20 mtorr); however, the silicon dioxide mask edge is also faceted by the directional etching of the ions. This is also undesirable, and therefore high pressures of greater than 50 mtorr are required for etching. It has been found that the introduction of the silicon via the gas mixture overcomes this lateral etching at the N+ sublayer. One such gas mixture is SiCl4 and a fluorine-containing gas, such as SF6, CF4, etc. The SiCl4 introduces the silicon loading directly and also the etching species, Cl. The fluorine-containing gas is used to consume the excess Si wh...