Silicon Carbide Substrate Void Control for Yield Improvement
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Solution Overview
Problem
The existing methods for manufacturing silicon carbide semiconductor devices face challenges in improving the yield due to the presence of voids and threading screw dislocations in the silicon carbide substrates.
Innovation Solution
A silicon carbide substrate with specific void configurations and threading screw dislocation distributions is developed, where the first main surface has one or more first voids with controlled dimensions and area density, and the second main surface has second voids with similar characteristics. The substrate is processed to reduce the area density of threading screw dislocations and to optimize the distribution of carbon inclusions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods are used to manufacture silicon carbide substrates, then the manufacturing process is simple, but the yield is low due to high density of voids and threading screw dislocations
Solution Approach 1:
The patent applies parameter changes by precisely controlling the growth conditions including temperature gradients, pressure, and chemical composition during the silicon carbide crystal growth process. By optimizing these parameters, the patent reduces the area density of voids to less than 0.9/cm² and controls threading screw dislocation density, thereby improving yield while maintaining manageable defect levels
Solution Approach 2:
The patent implements preliminary action by pre-treating the substrate surface and controlling the initial growth stage carefully. The method includes specific procedures for preparing the substrate, controlling nucleation, and early crystal growth to prevent the formation of voids and threading screw dislocations before they can propagate and affect device yield
2Reliability
If the area density of voids is reduced to improve yield, then device reliability improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent employs feedback mechanisms by implementing real-time monitoring and control of growth parameters during crystal formation. The process includes continuous adjustment of temperature, pressure, and chemical feed rates based on monitored conditions, ensuring that void density remains below 0.9/cm² while maintaining manufacturing feasibility through automated control systems
3Productivity
If threading screw dislocation density is reduced, then device performance improves, but the complexity of the manufacturing process increases
Solution Approach 1:
The patent replaces complex mechanical sorting and selection processes with a chemical and thermal field-based approach. Instead of mechanically separating substrates with different defect densities, the method uses controlled chemical vapor deposition and thermal field management to selectively grow crystals with reduced threading screw dislocation density, simplifying the overall manufacturing process while improving device performance
Data Source
AI summary
A silicon carbide substrate has a first main surface and a second main surface opposite to the first main surface. One or more first voids are present in the first main surface. An area density of the first voids is less than 0.9/cm2. When viewed in a direction perpendicular to the first main surface, the first void has a width of 10 μm or more and 100 μm or less. When viewed in a direction parallel to the first main surface, the width of the first void increases from the first main surface toward the second main surface. When viewed in the direction parallel to the first main surface, the first void has a depth smaller than a thickness of the silicon carbide substrate. The first main surface is a carbon plane, or a plane inclined at an off angle of 8° or less relative to the carbon plane.