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ANISOTROPIC ORGANIC REACTIVE ION ETCH PRODUCING MINIMAL SIDEWALL DEPOSITION

IP.com Disclosure Number: IPCOM000005596D
Original Publication Date: 1986-Oct-01
Included in the Prior Art Database: 2001-Oct-18
Document File: 1 page(s) / 84K

Publishing Venue

Motorola

Related People

Andrew G. Nagy: AUTHOR

Abstract

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.

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4% MOlYIROLA Technical Developments Volume 6 October 1986

ANISOTROPIC ORGANIC REACTIVE ION ETCH PRODUCING MINIMAL SIDEWALL DEPOSITION

by Andrew G. Nagy

   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.

The sputtered material reacts with the oxygen in the etch ambient to form an oxide of the inorganic material, and this oxide is deposited as a liner on the sidewall of the openings.

   The sputtered sidewall liner cause a number of problems. First, the presence of the sidewall liner results in a considerable change in the dimension of the opening through the organic layer. The patterned organic material will eventually act as an etch mask for the patterning of the underlying inorganic mater...