Nitride Semiconductor Substrate Structure to Prevent Edge Haze
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Solution Overview
Problem
Nitride semiconductor substrates with HEMT structures face issues of haze generation on the mirror edge surface during epitaxial growth, leading to dust and reaction traces, which cause defects and process failures.
Innovation Solution
A nitride semiconductor substrate is fabricated using a composite substrate with a silicon oxide or TEOS layer and a single crystal silicon layer, where the entire central flat surface of the silicon oxide or TEOS layer is covered by the single crystal silicon layer to prevent polycrystalline growth, and optionally, the side surface is covered with a silicon nitride film to suppress haze generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If epitaxial growth is performed on a composite substrate with a silicon oxide layer and single crystal silicon layer, then thick nitride semiconductor films can be grown with reduced warpage, but haze generates on the mirror edge surface and causes defects
Solution Approach 1:
The substrate surface is segmented into a central flat surface region and a peripheral inclined surface region. The central flat surface is covered by the single crystal silicon layer for high-quality epitaxial growth, while the peripheral inclined surface is formed by removing the single crystal silicon layer to expose the silicon oxide layer, preventing haze generation at the edge.
Solution Approach 2:
The single crystal silicon layer is selectively removed from the peripheral region to expose the silicon oxide layer. This extraction creates an inclined surface that prevents the nitride semiconductor film from contacting the silicon oxide layer's central flat surface, thereby eliminating the source of haze and defects.
2Productivity
If a large-diameter composite substrate is used, then productivity and heat dissipation are improved, but stress from lattice constant differences causes warpage and plastic deformation
Solution Approach 1:
The substrate uses a composite structure consisting of a polycrystalline ceramic core, adhesion layers, a silicon oxide layer, and a single crystal silicon layer. This composite structure combines materials with different properties to achieve both large diameter for productivity and stress management through the layered configuration, reducing warpage.
Solution Approach 2:
The thermal expansion coefficient of the composite substrate is adjusted by selecting appropriate materials and thicknesses for each layer. The polycrystalline ceramic core and adhesion layers are designed to have thermal expansion coefficients that match the nitride semiconductor film, reducing stress-induced warpage during temperature changes.
3Reliability
If the single crystal silicon layer completely covers the silicon oxide layer, then haze and defects are eliminated, but manufacturing complexity increases
Solution Approach 1:
The substrate surface is segmented into a central flat surface region and a peripheral inclined surface region. The central flat surface is covered by the single crystal silicon layer for high-quality epitaxial growth, while the peripheral inclined surface is formed by removing the single crystal silicon layer to expose the silicon oxide layer, preventing haze generation at the edge.
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 results in a substrate with no haze on the mirror edge surface, reduced dust and reaction traces, and fewer defects during the process, while also minimizing warpage and enabling the growth of thick nitride semiconductor thin films.
Implementation Method 1
a nitride semiconductor thin film deposited on the single crystal silicon layer
Implementation Method 2
stress caused by differences in lattice constants and thermal expansion coefficients tends to cause increased warpage
Implementation Method 3
epitaxial growth using vapor phase growth on a silicon substrate
Data Source
AI summary
A nitride semiconductor substrate including: a composite substrate with multiple layers stacked, a silicon oxide layer or a TEOS layer having a central flat surface and a side surface around the flat surface and stacked on the composite substrate; a single crystal silicon layer stacked on the silicon oxide layer or the TEOS layer, and a nitride semiconductor thin film deposited on the single crystal silicon layer, wherein the entire central flat surface of the silicon oxide layer or the TEOS layer is covered with the single crystal silicon layer.