Selective Titanium Etching via Fluorine Gas
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Solution Overview
Problem
In titanium silicide region forming methods, the use of titanium tetrachloride gas for etching results in a decreasing etching rate, leading to residual titanium films, necessitating selective removal of titanium-containing regions.
Innovation Solution
A method involving pretreatment to expose a clean silicon surface, forming titanium-containing and silicide regions, and using a fluorine-containing gas like chlorine trifluoride for selective etching of titanium-containing regions relative to titanium silicide regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If titanium tetrachloride gas is used for etching the titanium film, then the titanium film can be etched, but the etching rate decreases as etching progresses, causing residual titanium film to remain
Solution Approach 1:
The patent changes the chemical parameters of the etching process by switching from titanium tetrachloride gas to fluorine-containing gas (such as sulfur hexafluoride or nitrogen trifluoride). This parameter change fundamentally alters the etching chemistry, enabling complete removal of titanium film without the progressive rate decrease observed with titanium tetrachloride, thereby resolving the contradiction between etching completeness and productivity
Solution Approach 2:
The patent introduces a selective etching process using fluorine-containing gas as an intermediary step between titanium film formation and titanium silicide region formation. This intermediary etching process selectively removes unwanted titanium while preserving titanium silicide, achieving both complete etching and high productivity through selective chemical interaction
2Manufacturing precision
If titanium tetrachloride gas is used for etching, then etching can proceed, but selective removal of titanium-containing regions becomes necessary due to incomplete etching
Solution Approach 1:
The patent changes the chemical composition parameter of the etching gas from titanium tetrachloride to fluorine-containing gas, which inherently provides selective etching capability. This single parameter change eliminates the need for complex multi-step selective removal processes, reducing device complexity while maintaining manufacturing precision
Solution Approach 2:
The patent utilizes the inherent selectivity of fluorine-containing gas etching to replicate the desired selective removal effect without requiring additional masking or protective layer structures. The chemical selectivity of the fluorine-containing gas copies the function of complex selective etching processes in a simpler manner
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 allows for efficient and selective removal of titanium-containing regions, ensuring complete removal of titanium films while preserving titanium silicide regions, as demonstrated by experiments showing higher etching rates and selectivity with chlorine trifluoride compared to titanium tetrachloride.
Implementation Method 1
supplying a fluorine-containing gas to a workpiece including a titanium-containing region and a titanium silicide region formed on a silicon layer after performing a pretreatment so as to selectively etch the titanium-containing region with respect to the titanium silicide region
Data Source
AI summary
A titanium silicide region forming method includes: performing a pretreatment to expose a clean surface of a silicon layer of a workpiece; forming a titanium-containing region and a titanium silicide region on the silicon layer after performing the pretreatment; and supplying a fluorine-containing gas to the workpiece including the titanium-containing region and the titanium silicide region so as to selectively etch the titanium-containing region with respect to the titanium silicide region.