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LAMINATED Al-W-Al STRUCTURE

IP.com Disclosure Number: IPCOM000039241D
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Ahn, K: AUTHOR [+3]

Abstract

This publication describes a laminated structure and process conditions in which thick tungsten film is prepared with good mechanical properties, such as adhesion and stress. Tungsten is a new material in VLSI circuits which has been considered as an etch stop, as a stud material, as a contact diffusion barrier [1] and for gates and interconnections [1,2,3]. Delineation of tungsten lines or studs can be made by reactive ion etching (RIE). An etch stop is generally required for metal RIE to either avoid or reduce substrate etch, or to protect the uncovered contacts, and Al films are known to be a durable mask in reactive ion etching of W; hence the Al films must also be a good etch stop in W RIE. (That is a thin film of Al under the W acts to stop the etch process.) The figure describes a typical cross-sectional view.

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LAMINATED Al-W-Al STRUCTURE

This publication describes a laminated structure and process conditions in which thick tungsten film is prepared with good mechanical properties, such as adhesion and stress. Tungsten is a new material in VLSI circuits which has been considered as an etch stop, as a stud material, as a contact diffusion barrier [1] and for gates and interconnections [1,2,3]. Delineation of tungsten lines or studs can be made by reactive ion etching (RIE). An etch stop is generally required for metal RIE to either avoid or reduce substrate etch, or to protect the uncovered contacts, and Al films are known to be a durable mask in reactive ion etching of W; hence the Al films must also be a good etch stop in W RIE. (That is a thin film of Al under the W acts to stop the etch process.) The figure describes a typical cross-sectional view. The W films can be deposited by chemical vapor deposition (CVD), sputtering, or vacuum deposition techniques. The high stress in evaporated W films limits the useful thickness of W films. The W films obtained by CVD require an adhesion layer, such as Ti or tungsten silicide. The CVD W films directly deposited on the Al film will also cause the material reactions due to the high temperature process of CVD W. A process for sputtering an Al-W(1 mm)-Al sandwich structure in one pump-down with excellent mechanical properties, i.e., low stress and good adhesion, is disclosed herein. As mentioned above, the top layer of the Al film serves as a durable mask and the bottom layer of the Al film serves as an etch stop in W RIE etching. A cross-section...