Tungsten Film Formation via Initial Protective Layer
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Solution Overview
Problem
The miniaturization and complication of semiconductor devices lead to poor adhesive strength and fillability of tungsten films, particularly due to the etching effect of tungsten chloride gas on underlying films like TiN, which results in insufficient thickness for ensuring the integrity of the tungsten film.
Innovation Solution
A method involving the formation of an initial tungsten film using a smaller amount of tungsten chloride gas by CVD or ALD, followed by a main tungsten film with increased gas supply, to alleviate etching effects on the underlying film, ensuring adequate thickness and adhesive strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If tungsten chloride gas is supplied in large amount to form tungsten film by ALD, then film formation speed is improved, but etching effect on underlying film increases causing insufficient thickness
Solution Approach 1:
An initial tungsten film is formed before the main tungsten film formation. This preliminary film acts as a protective layer that prevents excessive etching of the underlying film during subsequent high-rate tungsten deposition, allowing fast film formation while preserving underlying film integrity
Solution Approach 2:
The tungsten film formation process is divided into two distinct stages: initial film formation with controlled etching, and main film formation with high deposition rate. This segmentation allows optimization of each stage independently - the initial stage protects the underlying film while the main stage maximizes productivity
2Adaptability or versatility
If device size is miniaturized, then device integration is improved, but adhesive strength and fillability of tungsten film deteriorate
Solution Approach 1:
The initial tungsten film is formed as a preliminary protective layer before main film deposition. This preliminary film ensures adequate adhesive strength on the underlying film even when the underlying film thickness is reduced due to device miniaturization, enabling continued miniaturization while maintaining film quality
3Quantity of substance
If supply amount of tungsten chloride gas is increased, then tungsten film thickness is improved, but etching amount of underlying film increases
Solution Approach 1:
The initial tungsten film acts as an intermediary protective layer between the tungsten chloride gas and the underlying film. During main film formation with high gas supply, this intermediary layer absorbs the etching effect, allowing high tungsten deposition while protecting the underlying film from excessive etching
Solution Approach 2:
By forming the initial tungsten film beforehand, a protective barrier is established that enables subsequent high-rate tungsten deposition without directly exposing the underlying film to aggressive etching conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the adhesive strength and fillability of the tungsten film, maintaining the required thickness and electrical characteristics despite device miniaturization and complexity.
Implementation Method 1
an initial tungsten film is formed by supplying a tungsten chloride gas and a reduction gas by using the CVD method or the ALD method
Implementation Method 2
reaction WF6+3H2→W+6HF occurs on a semiconductor wafer as a target object by using tungsten hexafluoride (WF6) as a source gas and H2 gas as a reduction gas
Data Source
AI summary
In a method of forming a tungsten film, an initial tungsten film and a main tungsten film are formed on an underlying film of a substrate. The initial tungsten film is formed on the underlying film by sequentially supplying a tungsten chloride gas and a reduction gas into a chamber while supplying a purging gas between the supplies of the tungsten chloride gas and the reduction gas, or by simultaneously supplying the tungsten chloride gas and the reduction gas. The main tungsten film is formed on the initial tungsten film by sequentially supplying the tungsten chloride gas and the reduction gas into the chamber while purging an inside of the chamber between the supplies of the tungsten chloride gas and the reduction gas. A supply amount of the tungsten chloride gas in forming the initial film is smaller than that in forming the main tungsten film.