Silicon Carbide Mask Etching for Impurity Precision
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Solution Overview
Problem
The challenge in manufacturing silicon carbide semiconductor devices lies in achieving precise control over the spreading of impurity regions, as the diffusion coefficient for impurities is small in silicon carbide substrates, making it difficult to adjust the spreading of impurity regions using the double diffusion method, and existing methods using tungsten masks result in warpage and reduced precision due to internal stress differences.
Innovation Solution
A method involving the formation of silicon oxide films on silicon carbide substrates with specific etching processes using gases like CHF3 and a mixture of oxygen and fluorine compounds to create mask patterns for ion implantation, allowing for precise formation of impurity regions with improved etching selectivity and reduced substrate warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tungsten is used for the ion implantation mask, then self-alignment precision is improved, but substrate warpage increases due to internal stress
Solution Approach 1:
The patent introduces a silicon oxide film as an intermediary layer between the silicon carbide substrate and the tungsten mask. This intermediate layer acts as a stress buffer that absorbs the internal stress from the tungsten mask, preventing it from transferring to the substrate and causing warpage, while still allowing the mask to maintain its self-alignment precision for accurate ion implantation.
Solution Approach 2:
The patent creates a composite mask structure consisting of multiple layers: the silicon oxide film layer and the tungsten mask layer. This composite structure combines the advantages of both materials - the silicon oxide provides stress buffering and adhesion, while the tungsten provides precise patterning and self-alignment capabilities, thereby resolving the contradiction between precision and warpage.
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 method enhances the precision in spreading impurity regions with self-alignment, reduces substrate warpage, and minimizes metal contamination, achieving improved uniformity and accuracy in semiconductor device manufacturing.
Implementation Method 1
forming a first mask pattern of the silicon oxide film by removing a portion of the silicon oxide film by means of first etching employing a first gas containing CHF3
Implementation Method 2
forming a second mask pattern of the silicon oxide film by removing a portion of the silicon oxide film by means of second etching employing a second gas containing oxygen gas and at least one fluorine compound gas selected from a group consisting of CF4, C2F6, C3F8, and SF6
Implementation Method 3
forming a first impurity region having first conductivity type by means of ion implantation of a first ion into the silicon carbide substrate including the silicon oxide film having the first mask pattern
Data Source
AI summary
A method for manufacturing a silicon carbide semiconductor device includes the step of forming a mask pattern of a silicon oxide film by removing a portion of the silicon oxide film by means of etching employing a gas containing oxygen gas and at least one fluorine compound gas selected from a group consisting of CF4, C2F6, C3F8, and SF6.