Tungsten silicide (WSIX) deposition process for semiconductor manufacture

Abstract

A semiconductor manufacturing process for depositing a tungsten silicide film on a substrate includes deposition of a tungsten silicide nucleation layer on the substrate using a (CVD) process with a silane source gas followed by deposition of the tungsten silicide film with a dichlorosilane source gas. This two step process allows dichlorosilane to be used as a silicon source gas for depositing a tungsten silicide film at a lower temperature than would otherwise by possible and without plasma enhancement. Tungsten silicide films deposited by this process are characterized by low impurities, good step coverage, and low stress with the silicon substrate.

Description

TECHNICAL FIELD[0001]This invention relates to semiconductor manufacture and more particularly to a novel process for the deposition of tungsten silicide (WSix) films.BACKGROUND OF THE INVENTION[0002]Refractory metals and their silicides are often used in semiconductor manufacture. One silicide that is of particular interest in the formation of MOS and CMOS integrated circuits is tungsten silicide. Tungsten silicide, generally in the form of (WSi2), can be used in the formation of integrated circuits as an intermediate, barrier, or conducting film. Tungsten silicide can also be used with polysilicon as a polycide-gate in transistor formation. Among the useful properties of tungsten silicide are its low bulk resistance and low stress.[0003]In the formation of a tungsten silicide film, the film quality and step coverage provided by the deposited film greatly influences the completed semiconductor devices. This is because poor step coverage and an irregular surface topography generated...

AI Technical Summary

Benefits of technology

[0010]In accordance with the present invention a novel process for depositing a tungsten silicide film is provided. The process of the invention, simply stated, includes the steps of; depositing a tungsten silicide nucleation layer on a substrate using silane as a silicon gas source and then switching to dichlorosilane as the silicon gas source to complete deposition of the tungsten silicide film. This two step process permits the dichlorosilane silicon source gas to react with a reactant gas at a relatively low temperature. In addition, this process can be performed in a cold wall (CVD) system without the need for plasma enhancement of the reactant gases. The reactant gas is preferably tungsten hexaflouride mixed with inert carrier gases.

[0011]Other objects, advantages and capabilities of the present invention will become more apparent as the description proceeds.

Problems solved by technology

This is because poor step coverage and an irregular surface topography generated by multi-layer processes causes serious difficulties for subsequent processing steps such as lithography, deposition, and etching.

Poor step coverage and high stress may also degrade device reliability by causing stress induced cracking.

Moreover, impurities in the deposited film may degrade device reliability and cause metal migration.

These deposition temperatures are typically in the range of 250°-400° C. A disadvantage of a (CVD) deposition process of tungsten silicide using this reaction chemistry is the very high levels of fluorine impurities in the deposited film.

In addition, step coverage may be poor.

), the requirement of plasma enhancement for thermal deposition tended to complicate the procedure.

Such a complicated procedure may not be entirely suitable for large scale semiconductor manufacture.

In addition plasma can cause degradation of devices due to radiation induced damage.