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Barrier Layer Metallurgy for Preventing Reaction between Aluminum and Polysilicon

IP.com Disclosure Number: IPCOM000087090D
Original Publication Date: 1976-Dec-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Chu, W: AUTHOR [+5]

Abstract

It has been recognized [*] that an aluminum-polysilicon reaction occurs even at 400 Degrees C. In many integrated circuit structures, aluminum metallurgy is formed over polysilicon. Thus, there is a need for an appropriate barrier between the aluminum and polysilicon to prevent such reaction. Titanium has been recognized to provide such a barrier. More recently, we have found that other transition metals such as tantalum, niobium and tungsten display lower reaction rates with aluminum than does titanium, and, therefore, provide improved barrier properties when used in such structures.

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Barrier Layer Metallurgy for Preventing Reaction between Aluminum and Polysilicon

It has been recognized [*] that an aluminum-polysilicon reaction occurs even at 400 Degrees C. In many integrated circuit structures, aluminum metallurgy is formed over polysilicon. Thus, there is a need for an appropriate barrier between the aluminum and polysilicon to prevent such reaction. Titanium has been recognized to provide such a barrier. More recently, we have found that other transition metals such as tantalum, niobium and tungsten display lower reaction rates with aluminum than does titanium, and, therefore, provide improved barrier properties when used in such structures.

In addition, particularly effective results have been achieved when a thin (amorphous or crystalline) transition metal oxide such as Ta(2)O(5) or other stable oxides, such as Ta(2)O, are formed at the interface between the tantalum and the covering aluminum layer. For example, with reference to the drawing, when forming a barrier layer over a layer of intrinsic polysilicon 11 formed on a silicon dioxide insulation 10 over an integrated circuit, a thin tantalum oxide layer 12 is formed on the surface of the tantalum barrier layer 13 to provide an interface with the aluminum metallurgy layer 14.

With respect to the barrier properties of such structures, when tantalum alone is used as the barrier layer, the structure can be heated to temperatures in the order of 450 degrees C without any appreciable alumi...