ANISOTROPIC ORGANIC REACTIVE ION ETCH PRODUCING MINIMAL SIDEWALL DEPOSITION
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2001-Oct-18
Tri-level photoresist processing is used to pattern a layer, usually an inorganic layer, on a substrate under conditions which require submicron resolution, vertical mask profiles, and in which the surface to be patterned is highly irregular and non-planar. In the tri-level process a thick layer of organic material such as photoresist or polyimide is applied to the surface of the material to be etched to act as leveling or planarizing layer. A "hard mask" layer of deposited oxide or nitride is formed overlying the organic material, and a layer of photoresist is applied over the hard mask. The photoresist is exposed and developed in normal manner and is used as an etch mask to pattern the hard mask. The hard mask, in turn, is used as an etch mask for the anisotropic etching of the thick planarizing layer. The anisotropic etch of the organic material is usually accomplished by low pressure reactive ion etching (RIE) under typical conditions of: O2 = 20 seem Pressure = 2.0 millitorr Power = 800 Watts rf Overetch = 25% The 25% overetch is necessary to insure that the desired openings through the organic layer are opened uniformly across the wafer surface. Unfortunately, some of the underlying inorganic material is exposed to the RIE during the overetch of the organic layer. The etching of the underlying inorganic material results in the sputterdeposition of that etched inorganic material onto the sides of the openings which have just been etched through the organic leveling material.