Silicon Carbide Wafer Growth for Low Basal Plane Dislocations
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Solution Overview
Problem
Existing silicon carbide wafer production methods fail to adequately address defects such as threading screw dislocations (TSD), threading edge dislocations (TED), and basal plane dislocations (BPD), leading to poor quality and yield in silicon carbide devices.
Innovation Solution
A method of forming silicon carbide wafers that includes controlling axial and radial temperature gradients during crystal growth, combined with photoluminescence and potassium hydroxide etching to analyze basal plane dislocation densities, ensuring ratios and densities fall within specific limits, thereby improving defect detection and yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional crystal growth methods are used to produce silicon carbide wafers, then production efficiency is maintained, but defect density (threading screw dislocations, threading edge dislocations, and basal plane dislocations) remains high leading to poor quality
Solution Approach 1:
The patent applies parameter changes by precisely controlling the axial temperature gradient (ΔTz) in the range of 20-150°C/cm and radial temperature gradient (ΔTx) in the range of 10-100°C/cm during crystal growth. This temperature gradient control modifies the crystallization conditions to reduce defect density while maintaining production efficiency, resolving the contradiction between quality and productivity
2Reliability
If only traditional defect detection methods (KOH etching for TSD, TED, and BPD) are used, then detection process is simple, but quality analysis is incomplete leading to affected yield
Solution Approach 1:
The patent merges multiple detection methods by combining KOH etching detection with photoluminescence detection to comprehensively identify different types of defects (TSD, TED, BPD, and PL-BPD). This combination provides complete quality analysis while managing detection complexity through systematic integration of complementary techniques
Solution Approach 2:
The patent introduces photoluminescence detection as an intermediary method that complements traditional KOH etching. Photoluminescence serves as a mediator to detect basal plane dislocations (PL-BPD) that are difficult to detect by conventional methods, thereby completing the quality analysis without significantly increasing overall detection complexity
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 method enables a more comprehensive quality analysis of silicon carbide wafers, resulting in extremely low defect densities and improved epitaxial quality yield, with defects like BPD, PL-BPD, TSD, BSF, and SF controlled within specified ranges, enhancing geometric yield and reducing defects like warp and triangle defects.
Implementation Method 1
a basal plane dislocation (PL-BPD) density detected by photoluminescence is less than 2000 pcs/cm2 at both the seed end and the dome end
Implementation Method 2
a basal plane dislocation (BPD) density detected by potassium hydroxide (KOH) etching is less than 550 pcs/cm2 at both the seed end and the dome end
Data Source
AI summary
A silicon carbide wafer having a seed end and a dome end opposite to the seed end. In the silicon carbide wafer, a basal plane dislocation (BPD) density detected by potassium hydroxide (KOH) etching is less than 550 pcs/cm2 at both the seed end and the dome end, and a basal plane dislocation (PL-BPD) density detected by photoluminescence is less than 2000 pcs/cm2 at both the seed end and the dome end.