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High Conductivity Tungsten Silicide-Tungsten Sandwich Structure

IP.com Disclosure Number: IPCOM000040683D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Joshi, RV: AUTHOR

Abstract

A technique is described whereby the conductivity of silicide structures is enhanced by forming a tungsten silicide-tungsten sandwich structure, as used in the metal oxide silicon (MOS) semiconductors. Through the use of thin refractory silicon-rich silicide, deposition and annealing techniques, a unique silicide sandwich structure provides high thermal stability and low resistivity. Silicides of refractory metals, such as WSix, MoSix, TaSi2, are used in submicron MOSFET salicide technology due to their low resistivities. However, lower resistivities are still required so as to reduce RC delays. The concept described herein provides a process to improve the thermal stability and to lower the resistivity of silicide structures.

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High Conductivity Tungsten Silicide-Tungsten Sandwich Structure

A technique is described whereby the conductivity of silicide structures is enhanced by forming a tungsten silicide-tungsten sandwich structure, as used in the metal oxide silicon (MOS) semiconductors. Through the use of thin refractory silicon-rich silicide, deposition and annealing techniques, a unique silicide sandwich structure provides high thermal stability and low resistivity. Silicides of refractory metals, such as WSix, MoSix, TaSi2, are used in submicron MOSFET salicide technology due to their low resistivities. However, lower resistivities are still required so as to reduce RC delays. The concept described herein provides a process to improve the thermal stability and to lower the resistivity of silicide structures. The process involves the deposition of a thin refractory silicon- rich silicide of 100-200 Ao on a silicon structure so as to produce a sandwich effect, as shown in the figure. Metal with a low resistivity is deposited on the already deposited silicide layer. Again, a layer of silicon-rich silicide is deposited, and the cycle of metal deposition and silicide deposition continues until the desired thickness is attained. The final layer must be a silicide layer so as to prevent the oxidation of the refractory metal. An annealing, which may be performed at a temperature lower than during the deposition, takes place so that excess silicon will react with the pure metal and form a b...