Fluorine-Free Tungsten Nitride Film Formation via Chloride ALD
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Solution Overview
Problem
The existing Atomic Layer Deposition (ALD) method using tungsten hexafluoride (WF6) gas introduces fluorine into tungsten nitride films, which can diffuse into other layers and degrade device characteristics in semiconductor manufacturing.
Innovation Solution
A method involving the alternated supply of tungsten chloride gas and hydrogen-containing gas, with nitrogen-containing gas for nitriding, to form a tungsten nitride film, utilizing a fluorine-free process that ensures low fluorine concentration and good filling properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ALD method using WF6 gas is used to form tungsten nitride film, then good step coverage is achieved, but fluorine is introduced into the film which degrades device characteristics
Solution Approach 1:
The harmful fluorine element is extracted/removed from the precursor material selection. Instead of using WF6 (tungsten hexafluoride) which contains fluorine, the patent uses WCl6 (tungsten hexachloride) as the tungsten source precursor, thereby eliminating the source of fluorine contamination while maintaining the ALD process benefits for step coverage
Solution Approach 2:
The chemical composition parameters of the precursor materials are changed. The patent modifies the precursor from fluoride-based (WF6) to chloride-based (WCl6), and adjusts the reaction conditions including using H2 or H2-containing gas as reducing agent at controlled temperatures (400-600°C) to achieve fluorine-free tungsten nitride film formation while maintaining good step coverage
2Manufacturing precision
If ALD method is used to form tungsten nitride film, then good filling property is achieved, but fluorine diffusion to other layers occurs
Solution Approach 1:
The fluorine element is completely removed from the process chemistry. By using WCl6 instead of WF6 as the tungsten precursor and H2-based reducing atmosphere instead of fluoride-containing gases, the source of fluorine diffusion is eliminated, preventing contamination of underlying and overlying layers while maintaining the conformal filling properties of ALD
Solution Approach 2:
An intermediary substance (H2 or H2-containing gas) is introduced as the reducing agent to convert tungsten chloride to tungsten metal and subsequently to tungsten nitride without introducing fluorine. This intermediary approach allows the ALD process to maintain its filling properties while avoiding fluorine contamination through careful selection of intermediate reaction species
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 effectively forms tungsten nitride films with low fluorine content and excellent filling properties, preventing fluorine diffusion and maintaining device integrity.
Implementation Method 1
forming a tungsten film by repeating a cycle of alternately supplying a tungsten chloride gas and a hydrogen-containing gas
Implementation Method 2
nitriding the tungsten film by supplying a nitrogen-containing gas
Implementation Method 3
with a supply of a purge gas interposed between the supply of the tungsten chloride gas and the supply of the hydrogen-containing gas
Data Source
AI summary
There is provided a method of forming a tungsten nitride film on a substrate to be processed, including: forming a tungsten film by repeating a cycle of alternately supplying a tungsten chloride gas and a hydrogen-containing gas with a supply of a purge gas interposed between the supply of the tungsten chloride gas and the supply of the hydrogen-containing gas; and nitriding the tungsten film by supplying a nitrogen-containing gas.