Microcrystal Orientation Layer for Low-Defect α-Ga2O3 Substrates
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Solution Overview
Problem
Conventional base substrates used for crystal growth of α-gallium oxide suffer from chipping and cracking during grinding and polishing due to lattice constant mismatch, leading to reduced yield and increased crystal defects.
Innovation Solution
A base substrate with an orientation layer containing microcrystals having a corundum-type crystal structure and specific lattice constants, incorporating microcrystals with controlled size and density, reduces lattice mismatch and minimizes chipping during polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If α-Ga2O3 is formed by heteroepitaxial growth on a sapphire substrate, then crystal growth is enabled, but stress is applied into the semiconductor film due to lattice constant difference forming a large number of crystal defects
Solution Approach 1:
An orientation layer composed of α-Al2O3 with controlled crystal orientation is introduced between the sapphire substrate and the α-Ga2O3 semiconductor film. This intermediary layer serves as a buffer that reduces the lattice constant mismatch stress, enabling high-quality crystal growth with reduced dislocation density while maintaining the manufacturability of heteroepitaxial growth processes.
Solution Approach 2:
The crystal orientation parameters of the α-Al2O3 orientation layer are precisely controlled to optimize lattice matching. By adjusting the crystallographic orientation of the orientation layer, the patent achieves better lattice constant alignment between the substrate system and the α-Ga2O3 film, thereby reducing misfit dislocations and improving semiconductor quality.
2Manufacturing precision
If the orientation layer is ground and polished to flatten and mirror-finish the top surface, then surface quality is improved, but chipping is likely to occur on the edge of the orientation layer reducing yield
Solution Approach 1:
The orientation layer is designed with sufficient thickness and optimized mechanical properties to act as a cushioning layer during grinding and polishing operations. This pre-designed structural buffer prevents stress concentration at the edges, thereby preventing chipping and reducing waste during surface finishing processes while maintaining high surface quality.
Solution Approach 2:
The base substrate is constructed as a composite structure combining the sapphire substrate, the α-Al2O3 orientation layer with specific crystal orientation, and the α-Ga2O3 semiconductor film. This composite design leverages the complementary properties of each layer: the mechanical strength of sapphire, the orientation-control capability of α-Al2O3, and the semiconductor functionality of α-Ga2O3, achieving both high surface finish quality and high yield.
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 substrate design significantly reduces crystal defects and chipping, enhancing the quality and yield of semiconductor layers by aligning lattice constants and maintaining surface integrity.
Implementation Method 1
the lattice constant of the base substrate and that of α-Ga2O3 are matched
Implementation Method 2
α-Ga2O3 is formed by heteroepitaxial growth on a sapphire substrate
Data Source
AI summary
There is provided a base substrate including an orientation layer used for crystal growth of a semiconductor film composed of α-Ga2O3 or an α-Ga2O3 solid solution. The orientation layer is composed of a material having a corundum-type crystal structure having an a-axis length and/or c-axis length larger than that of sapphire, and a plurality of microcrystals defined as crystal grains having a major axis length of 1 nm to 2 μm are present inside the orientation layer.