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Method For Improving Silicon RIE In CBrF(3) by the Addition of Oxygen

IP.com Disclosure Number: IPCOM000048583D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Gray, RK: AUTHOR [+2]

Abstract

When patterns are reactive ion etched (RIE) in silicon using pure CBrF(3), with SiO(2) as the mask material, the larger silicon areas become dark in color and rough when examined with a scanning electron microscope. This effect is due to the formation of a non-volatile reaction product at the silicon surface which is back-scattered at high pressures of greater than about 30 millitorr. The higher the pressure the faster this dark silicon forms. It is often important to etch the silicon pattern at high pressure. This is to prevent faceting of the silicon dioxide (SiO(2)) mask edge. The formation of the dark silicon restricts the use of CBrF(3) reactive sputter etching, to narrow patterns at low density.

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Method For Improving Silicon RIE In CBrF(3) by the Addition of Oxygen

When patterns are reactive ion etched (RIE) in silicon using pure CBrF(3), with SiO(2) as the mask material, the larger silicon areas become dark in color and rough when examined with a scanning electron microscope. This effect is due to the formation of a non-volatile reaction product at the silicon surface which is back-scattered at high pressures of greater than about 30 millitorr. The higher the pressure the faster this dark silicon forms. It is often important to etch the silicon pattern at high pressure. This is to prevent faceting of the silicon dioxide (SiO(2)) mask edge. The formation of the dark silicon restricts the use of CBrF(3) reactive sputter etching, to narrow patterns at low density.

The dark silicon problem can be eliminated by introducing a partial pressure of O(2) to the CBrF(3) gas. When a CBrF(3)/O(2) mixture is used, the non- volatile product dies not form on the silicon surface, resulting in a smoothly etched surface. Furthermore, when the silicon surface remains clean, the modified reaction products at the silicon surface in the presence of oxygen are such to inhibit the silicon dioxide etch rate. With O(2) present, a 58 mm bare silicon wafer adjacent to a SiO(2) film reduces the etch rate of SiO(2) from 860 A/min. to 490 A/min., increasing the Si to SiO(2) etch rate ratio (eRR) from about 5:1 to about 9:1, the etch parameters being 300 watt/8" diameter electrode, 100 ...