Patent ID: 6897153

Claim:
A method of etching a silicon oxide layer comprising the steps of: (a) flowing an etching gas composition into a plasma chamber, wherein the etching gas composition consists essentially of: (i) a carbon fluoride gas of the general chemical formula C x F y , in which y/x is a ratio having a value less than 2 and which chemical formula includes at least a double or a triple carbon-carbon bond; (ii) a fluorohydrocarbon gas of the general chemical formula C k H l F m , in which k, l and m are positive integers and wherein the volumetric flow rate of the fluorohydrocarbon gas to that of the carbon fluoride gas is a ratio having a value in a range of about 0.1 to 3.0; and (iii) oxygen, wherein the volumetric flow rate of oxygen to that of the carbon fluoride gas is a ratio having a value of about 1 to 1; and, (b) implementing an etching procedure by generating a plasma of said etching gas composition inside said plasma chamber, and applying said plasma onto said silicon oxide to form contact holes of substantially the same depth and with a high aspect ratio, each having top and bottom portions, wherein the top portion of each contact hole is only very slightly wider than the bottom portion.