Oxide Semiconductor Multilayer Structure for Thermal Stress Control
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Solution Overview
Problem
Semiconductor multilayer structures using gallium oxide face degradation issues due to warpage and cracking at high temperatures, particularly in power devices, caused by stress and mismatched coefficients of linear expansion between the semiconductor layer and the conductive substrate.
Innovation Solution
A multilayer structure comprising a crystalline oxide semiconductor layer and a conductive substrate with a specific composition and orientation, where the conductive substrate includes two metals with identical or substantially identical coefficients of linear expansion in perpendicular directions, reducing thermal stress and degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional conductive substrate is used with the semiconductor layer, then the device can be manufactured, but warpage and cracking occur at high temperatures due to stress and coefficient of linear expansion mismatch
Solution Approach 1:
The patent changes the physical parameters of the conductive substrate by selecting metals with specific coefficients of linear expansion that match the semiconductor layer. This parameter matching eliminates thermal stress during temperature changes, preventing warpage and cracking while maintaining structural integrity at high temperatures.
Solution Approach 2:
The patent employs a composite structure consisting of the semiconductor layer and the conductive substrate as integrated components. By designing the conductive substrate with specific metallic compositions (such as copper, aluminum, or their alloys) that have matched thermal expansion properties, the composite structure achieves coordinated thermal behavior, eliminating interfacial stress and enhancing high-temperature reliability.
2Ease of manufacture
If the conductive substrate has different coefficients of linear expansion in different directions, then manufacturing is easier, but thermal stress causes degradation and cracking
Solution Approach 1:
The patent modifies the physical parameters of the conductive substrate by selecting metals and configuring their crystallographic orientations so that the coefficients of linear expansion in the principal directions (a-axis and c-axis for hexagonal structures) are substantially equal. This parameter optimization eliminates anisotropic thermal stress while maintaining manufacturability through standard fabrication processes.
Solution Approach 2:
The patent applies specific crystallographic orientation requirements to different regions of the conductive substrate, ensuring that the a-axis and c-axis directions are properly aligned relative to the semiconductor layer interface. This local quality control ensures uniform thermal expansion behavior across the substrate while maintaining ease of manufacture through controlled crystal growth or processing.
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 solution effectively minimizes degradation and cracking of the semiconductor layer at high temperatures, enhancing the reliability and performance of semiconductor devices, particularly in power applications.
Implementation Method 1
a first coefficient of linear expansion being a coefficient of linear expansion in the first direction of the conductive substrate and a second coefficient of linear expansion being a coefficient of linear expansion in the second direction are identical or substantially identical
Data Source
AI summary
Provided is a multilayer structure including at least: a semiconductor layer containing a crystalline oxide semiconductor as a major component; and a conductive substrate layered on the semiconductor layer, wherein the conductive substrate includes at least a first metal and a second metal different from the first metal, the conductive substrate has a first direction and a second direction perpendicular or substantially perpendicular to the first direction in a plane, and a first coefficient of linear expansion being a coefficient of linear expansion in the first direction of the conductive substrate and a second coefficient of linear expansion being a coefficient of linear expansion in the second direction are identical or substantially identical.