Biaxially Oriented SiC Substrate for Low TSD Without Macrodefects
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Solution Overview
Problem
Conventional SiC substrates face challenges in reducing threading screw dislocation (TSD) density below 300 cm−2, particularly when using chemical vapor deposition methods, and often suffer from macrodefects like solvent inclusion and surface roughness when using solution growth methods.
Innovation Solution
A biaxially oriented SiC substrate is developed, characterized by specific photoluminescence (PL) intensity patterns and boron concentration, which effectively reduces TSD density by controlling the distribution of PL intensity and incorporating a SiC single crystal substrate, thereby minimizing macrodefects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a solution growth method is used to produce SiC substrate, then threading screw dislocation density can be reduced, but macrodefects such as solvent inclusion and surface roughness occur
Solution Approach 1:
The patent changes the growth method from solution growth to chemical vapor deposition, altering the physical and chemical parameters of the manufacturing process. This parameter change enables reduction of TSD density while avoiding the macrodefects associated with solution growth methods
Solution Approach 2:
The patent introduces a buffer layer as an intermediary between the SiC substrate and the epitaxial layer. This buffer layer acts as a mediator that prevents the propagation of threading screw dislocations to the epitaxial layer, thereby reducing TSD density without causing macrodefects
2Object-affected harmful factors
If chemical vapor deposition method is used to form SiC epitaxial layer, then macrodefects are avoided, but threading screw dislocation density remains high at 300 to 500 cm−2
Solution Approach 1:
The patent applies preliminary action by forming a buffer layer before growing the epitaxial layer. This preliminary structure prepares the substrate by reducing TSD density in advance, ensuring that when the epitaxial layer is grown by CVD, the TSD density is already reduced to below 300 cm−2
Solution Approach 2:
The patent segments the epitaxial structure into multiple layers: a buffer layer and an epitaxial layer. This segmentation allows the buffer layer to specifically address TSD reduction while the epitaxial layer provides the functional semiconductor structure, achieving both low TSD density and absence of macrodefects
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 SiC substrate achieves a low TSD density on the surface without using the solution growth method, preventing macrodefects and significantly decreasing TSD propagation to the epitaxial layer, thus enhancing the substrate's quality and performance.
Implementation Method 1
when a surface of the biaxially oriented SiC layer is analyzed by photoluminescence (PL) to obtain a graph by plotting PL intensity I as the vertical axis versus distance (μm) in the [11-20] direction as the horizontal axis
Data Source
AI summary
There is provided a SiC substrate including a biaxially oriented SiC layer, wherein when analyzed by photoluminescence (PL) to obtain a graph by plotting PL intensity I as the vertical axis versus distance (μm) in the [11-20] direction as the horizontal axis, (i) the graph has a shape such that a maximum point and a minimum point are repeated, (ii) when a maximum value of PL intensity I at a maximum point PM is assumed to be M, and a minimum value of PL intensity I at a minimum point Pm whose distance in the [11-20] direction is longer than that of the maximum point PM, and point Pm being present at a position nearest to point PM, is assumed to be m, a ratio of M/m is 1.05 or more, and (iii) distance L in the [11-20] direction between point PM and point Pm is 15 to 150 μm.