Silicon Carbide Epitaxial Growth BPD Reduction
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Solution Overview
Problem
Existing epitaxial growth processes struggle to reduce basal plane dislocation (BPD) density in silicon carbide power devices to the required levels for high reverse blocking voltages, as current techniques either introduce defects or increase costs due to complex handling and polishing processes.
Innovation Solution
The method involves interrupting silicon carbide growth by stopping or reducing the silicon source gas flow while maintaining the carrier gas flow and elevated temperature, allowing for in situ conversion of BPDs to threading edge dislocations (TEDs) within the growth chamber, which can be repeated to achieve significant BPD reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If KOH etching, epitaxial growth, and repolishing process is used to reduce BPD density, then BPD-to-TED conversion is increased, but the process complexity and manufacturing cost significantly increase due to handling and polishing steps
Solution Approach 1:
The patent combines multiple separate processes (KOH etching, epitaxial growth, and repolishing) into a single integrated epitaxial growth process. By incorporating the defect conversion mechanism directly into the growth chamber, the method eliminates the need for separate handling, etching, and polishing steps, thereby reducing process complexity while maintaining BPD density reduction effectiveness
Solution Approach 2:
The patent extracts the essential function (BPD-to-TED conversion) from the complex multi-step process and implements it directly during epitaxial growth. By taking out the conversion mechanism and integrating it into the growth process itself, the method removes the need for subsequent repolishing and handling steps, simplifying the overall manufacturing process
2Manufacturing precision
If surface patterning process is used to reduce BPD density, then BPD-to-TED conversion is increased, but lithography problems are introduced during device fabrication
Solution Approach 1:
The patent extracts the BPD conversion function from surface patterning and implements it through controlled epitaxial growth conditions. By removing the need for surface patterning and its associated lithography steps, the method eliminates lithography quality issues while maintaining effective BPD density reduction
Solution Approach 2:
The patent replaces the mechanical surface patterning process with a chemical/thermal process occurring during epitaxial growth. By substituting the mechanical patterning approach with in-situ defect conversion during growth, the method avoids introducing lithography problems while achieving the same BPD reduction goal
3Manufacturing precision
If offcut angle is lowered to increase BPD-to-TED conversion, then conversion rate is improved, but other extended defects are introduced that degrade device performance
Solution Approach 1:
The patent changes the epitaxial growth parameters (temperature, pressure, gas composition, growth rate) to achieve high BPD-to-TED conversion without altering the substrate offcut angle. By controlling the chemical and thermal environment during growth, the method achieves effective defect conversion while avoiding the introduction of other extended defects that would occur with angle modification
Solution Approach 2:
The patent applies localized control of growth conditions at the dislocation sites during epitaxial growth. By creating specific local environments (through gas composition and temperature gradients) that promote BPD conversion to TEDs without affecting the overall crystal structure, the method achieves high conversion rates without introducing other defects
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 achieves a high conversion rate of BPDs to TEDs, reducing BPD density by at least 98% and maintaining a final density below 10/cm², thereby improving device performance without introducing new defects or increasing production costs.
Implementation Method 1
maintaining the flow of the carrier gas while maintaining an elevated temperature in the growth chamber for a period of time
Implementation Method 2
flowing a silicon source gas, a carbon source gas, and a carrier gas into a growth chamber under growth conditions to epitaxial grow silicon carbide on a wafer
Data Source
AI summary
A method of: flowing a silicon source gas, a carbon source gas, and a carrier gas into a growth chamber under growth conditions to epitaxial grow silicon carbide on a wafer in the growth chamber; stopping or reducing the flow of the silicon source gas to interrupt the silicon carbide growth and maintaining the flow of the carrier gas while maintaining an elevated temperature in the growth chamber for a period of time; and resuming the flow of the silicon source gas to reinitiate silicon carbide growth. The wafer remains in the growth chamber throughout the method.