SiC Substrate Segmentation for Impurity Control
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Solution Overview
Problem
Silicon carbide substrates manufactured using the solution growth method contain non-dopant metal impurities that contaminate process devices during semiconductor device manufacturing, leading to device degradation.
Innovation Solution
A silicon carbide substrate with a substrate inner portion having a non-dopant metal impurity concentration of 1×10^16 cm^-3 or more, and a substrate outer portion with a surface region having a concentration less than 1×10^16 cm^-3, reducing contamination and threading screw dislocation density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the solution growth method is used to manufacture silicon carbide substrate, then the threading dislocation density is reduced, but non-dopant metal impurities are introduced that contaminate process devices
Solution Approach 1:
The substrate is divided into two distinct regions: a first region (inner portion) containing non-dopant metal impurities and a second region (outer portion) free from such impurities. This segmentation allows the substrate to simultaneously achieve low threading dislocation density through solution growth in the first region while preventing contamination of process devices by maintaining a clean second region at the surface where devices are manufactured.
Solution Approach 2:
Different regions of the substrate are assigned different impurity characteristics: the first region has controlled non-dopant metal impurity concentration to enable low-defect crystal growth, while the second region maintains ultra-low impurity levels to prevent contamination. This local differentiation of quality allows each region to fulfill its specific function without compromising the other.
2Productivity
If metal solutes are added to improve carbon solubility in silicon melt, then practical growth rate is achieved, but metal impurities are introduced into the grown crystal
Solution Approach 1:
The substrate structure is segmented into a first region where metal solutes are intentionally introduced during solution growth to achieve practical growth rates, and a second region where metal impurity concentration is controlled to be below detection limits. This segmentation allows the system to benefit from enhanced growth rate in the bulk while eliminating contamination risks at the surface.
Solution Approach 2:
The harmful metal impurities are effectively extracted or excluded from the second region (surface region) while being retained in the first region (inner portion) where they serve a beneficial purpose for crystal growth. This selective removal of harmful elements from the critical surface region resolves the contradiction between productivity and purity.
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 suppresses contamination of process devices and reduces threading screw dislocation density, enhancing the quality and reliability of semiconductor devices by minimizing non-dopant metal impurities on the substrate surface.
Implementation Method 1
the substrate outer portion surrounding the substrate inner portion, wherein non-dopant metal impurity concentration of the substrate inner portion is 1×10^16 cm^-3 or more, and a region of the substrate outer portion at least on a surface side
Data Source
AI summary
It is an object of the present invention to provide a silicon carbide substrate having a low defect density that does not contaminate a process device and a silicon carbide semiconductor device including the silicon carbide substrate. A silicon carbide substrate according to the present invention is a silicon carbide substrate including: a substrate inner portion; and a substrate outer portion surrounding the substrate inner portion, wherein non-dopant metal impurity concentration of the substrate inner portion is 1×1016 cm−3 or more, and a region of the substrate outer portion at least on a surface side thereof is a substrate surface region in which the non-dopant metal impurity concentration is less than 1×1016 cm−3.