Silicon Seed Layer Prevents Tungsten Oxidation During ALD
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Solution Overview
Problem
The existing methods for forming a silicon oxide film on a tungsten film using oxygen active species often lead to oxidation and volatilization of tungsten, resulting in deteriorated electric characteristics and reduced productivity due to the infiltration of oxygen radicals into the tungsten film.
Innovation Solution
A method involving a silicon seed layer formation on the tungsten film, followed by annealing to reduce natural oxide films and subsequent ALD silicon oxide film formation using silicon-containing gases and oxygen active species, which acts as a barrier to limit oxygen infiltration and prevent tungsten oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ALD process using oxygen active species is performed to form silicon oxide film on tungsten film, then silicon oxide film is formed, but tungsten film is oxidized and volatilized causing deterioration of electric characteristics
Solution Approach 1:
A silicon-containing gas is supplied to form a silicon seed layer on the tungsten film surface before the ALD process. This preliminary silicon layer acts as a protective barrier that prevents oxygen active species from reaching and oxidizing the tungsten film during subsequent ALD processing, thereby maintaining electric characteristics while enabling silicon oxide film formation
Solution Approach 2:
The silicon seed layer serves as an intermediary substance between the tungsten film and oxygen active species. It intercepts the oxygen radicals that would otherwise directly contact and damage the tungsten film, allowing the ALD process to proceed without compromising the underlying tungsten layer's integrity and electrical properties
2Productivity
If low temperature ALD process is performed first then high temperature ALD process to improve wet etching resistance, then productivity is maintained, but oxygen radicals still infiltrate into tungsten film causing oxidation
Solution Approach 1:
The silicon-containing gas is supplied before any ALD processing to create a protective silicon seed layer. This preliminary protection is in place before oxygen radicals can infiltrate during either low or high temperature ALD processes, preventing tungsten oxidation while maintaining the two-stage ALD approach for productivity and wet etching resistance
3Quantity of substance
If oxygen active species are used to form silicon oxide film, then film formation is achieved, but tungsten film integrity is compromised due to oxidation and volatilization
Solution Approach 1:
The silicon seed layer acts as a mediator that allows oxygen active species to be consumed in forming silicon oxide on the silicon layer rather than allowing direct oxidation of tungsten. This intermediary silicon layer protects tungsten film integrity while still enabling sufficient silicon oxide film formation through the ALD process
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 suppresses tungsten oxidation and volatilization, maintaining the integrity of the tungsten film and enhancing the quality and wet etching resistance of the silicon oxide film, thereby improving the manufacturing process for 3D-NAND type nonvolatile semiconductor devices.
Implementation Method 1
forming a silicon seed layer by adsorbing a silicon-containing gas to the tungsten film
Implementation Method 2
performing a third process of annealing the object and forming the silicon oxide film by a reaction of the natural oxide film and the silicon seed layer
Implementation Method 3
forming a silicon oxide film by a reaction of the natural oxide film and the silicon seed layer
Implementation Method 4
forming an ALD silicon oxide film by ALD using a silicon-containing gas and oxygen active species
Data Source
AI summary
A method for forming a silicon oxide film on a tungsten film includes performing a first process of arranging an object to be processed in a processing container kept under a reduced pressure, the object including a tungsten film and a natural oxide film being formed on a surface of the tungsten film, performing a second process of forming a silicon seed layer by adsorbing a silicon-containing gas to the tungsten film, subsequently performing a third process of annealing the object and forming the silicon oxide film by a reaction of the natural oxide film and the silicon seed layer and subsequently performing a fourth process of forming an ALD silicon oxide film by ALD using a silicon-containing gas and an oxygen active species.