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Enhanced Polycide Structures

IP.com Disclosure Number: IPCOM000050123D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Campbell, DR: AUTHOR [+2]

Abstract

Described is a polycide structure which yields a combination of good film adhesion with excellent electrical conductivity.

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Enhanced Polycide Structures

Described is a polycide structure which yields a combination of good film adhesion with excellent electrical conductivity.

Polycide structures typically consist of a layer of a co-deposited transition metal silicide on polysilicon. These structures result in greatly increased conductivity as compared to polysilicon, and are used as gate metallization in FET circuits as well as a number of potential bipolar applications.

Refractory metal silicides, such as WSi(2), MoSi(2), TaSi(2) and NbSi (2), are favored for these applications because of their stability at high processing temperatures (up to 1000 degrees C), oxidizability, resistance to chemical reagents, etc., 1. However, from among this group, no one silicide possesses the two critical properties of excellent adhesion together with high conductivity. For example, experiments as well as literature data (see 1 for instance instance indicate that TaSi is more adhesive and equilibrates (i.e., exchanges atoms) more readily with the underlying polysilicon film than does WSi(2). On the other hand, thin film WSi(2) is substantially more conductive than Mu Omega cm, Rho (TaSi(2))=45 Mu Omega cm (1 and 2, respectively).

A nearly ideal polycide structure would consist of WSi(2)/TaSi(2)/ polysilicon, as shown in the drawing. The TaSi layer provides adhesion, and the WSi(2) layer gives the high conductivity required. The TaSi(2) layer could be as thin as 100-200 Angstroms and still serve its fu...