SiC MOSFET Thermal Etching Semi-Polar Plane Formation
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Solution Overview
Problem
Conventional silicon carbide semiconductor devices face issues with crystal defects leading to deteriorated electrical characteristics due to micropipes and difficulty in controlling impurity concentration during liquid phase crystal growth, as well as limited processing accuracy in forming semi-polar planes for improved channel mobility.
Innovation Solution
A method for manufacturing semiconductor devices using a silicon carbide layer with an inclined end surface corresponding to semi-polar planes such as {03-3-8}, {01-1-4}, or {100} planes, achieved through thermal etching with a reaction gas containing oxygen and chlorine, allowing for stable crystal growth and precise control of impurity concentration without liquid phase growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid phase epitaxial growth is used to grow silicon carbide single-crystal, then micropipe density is reduced, but impurity concentration cannot be precisely controlled
Solution Approach 1:
The invention changes the growth method from liquid phase epitaxial growth to vapor phase growth (CVD or PECVD). This parameter change enables precise control of impurity concentration through gas phase reactions while maintaining low micropipe density through controlled deposition conditions
Solution Approach 2:
The invention replaces the liquid phase growth mechanism with a vapor phase deposition mechanism. Instead of using melted silicon source as in liquid phase epitaxy, the invention uses gaseous silicon sources (such as silane) that deposit as solid silicon carbide, enabling better control over impurity concentration
2Ease of manufacture
If machining is used to form semi-polar plane, then processing accuracy is limited, but device characteristics are not sufficiently improved
Solution Approach 1:
The invention replaces mechanical machining with chemical vapor deposition to form the semi-polar plane. The crystal plane is formed through controlled vapor phase growth where the crystal structure naturally develops the desired semi-polar orientation, achieving much higher precision than mechanical machining
Solution Approach 2:
The invention changes the formation method from mechanical removal to chemical deposition. By controlling deposition parameters such as gas composition, temperature, and pressure, the semi-polar plane is formed with atomic-level precision that cannot be achieved by machining
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
The approach results in semiconductor devices with reduced leakage current and high breakdown voltage, providing stable and improved electrical characteristics by utilizing spontaneously formed semi-polar planes as active regions.
Implementation Method 1
forming an end surface inclined relative to the main surface, by heating a silicon carbide layer while exposing the silicon carbide layer to a reaction gas containing oxygen and chlorine
Implementation Method 2
heating a silicon carbide layer while exposing the silicon carbide layer to a reaction gas containing oxygen and chlorine
Data Source
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AI summary
A method for manufacturing a high-quality semiconductor device having stable characteristics is provided. The method for manufacturing the semiconductor device includes the steps of: preparing a silicon carbide layer (2 to 4) having a main surface; forming a trench (16) in the main surface by removing a portion of the silicon carbide layer (2 to 4); and removing a portion of a side wall of the trench (16) by thermal etching.