SiC Epitaxial Wafer Large Pit Defect Reduction
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Solution Overview
Problem
Triangular defects in SiC epitaxial wafers, caused by substrate carbon inclusions, render portions of the wafer unusable, and large pit defects are identified as 'killer defects' due to their impact on device performance, particularly in Schottky barrier diodes, where they cause significant current leakage.
Innovation Solution
A SiC epitaxial wafer is produced with a 4H—SiC single crystal substrate having a controlled carbon inclusion density of 0.1 to 6.0 inclusions/cm², and an epitaxial growth process with a growth rate of 5 to 100 μm/hour and a C/Si ratio of 1.25 or less, where large pit defects are reduced to 0.5 defects/cm² or less, using a confocal microscope with a differential interference optical system for defect detection and identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SiC epitaxial growth is performed without controlling substrate carbon inclusions, then production efficiency is maintained, but large pit defects occur causing device failure
Solution Approach 1:
The patent applies preliminary action by controlling and managing substrate carbon inclusions before epitaxial growth occurs. Specifically, the method involves detecting carbon inclusions on the substrate surface before growth, mapping their positions, and using this information to adjust growth conditions or select substrates, thereby preventing large pit defects before they form during the epitaxial process.
Solution Approach 2:
The patent implements feedback by using detection results of substrate carbon inclusions to adjust subsequent epitaxial growth processes. The system detects inclusion positions, feeds this information back to control the growth rate and other parameters, and thereby dynamically prevents defect formation during the growth process itself.
2Productivity
If substrate carbon inclusion density is high, then more epitaxial wafers can be produced, but large pit defect density increases causing device failure
Solution Approach 1:
The patent applies local quality by treating different regions of the substrate differently based on their carbon inclusion characteristics. Instead of uniform growth conditions across the entire substrate, the method adjusts growth parameters locally according to the detected inclusion density and distribution in specific areas, thereby preventing defects in high-risk regions while maintaining production efficiency.
Solution Approach 2:
The patent changes growth parameters such as growth rate, temperature, and pressure based on the detected substrate carbon inclusion density and distribution. By dynamically adjusting these parameters according to local inclusion conditions, the method prevents large pit defects while maintaining overall production efficiency.
3Measurement precision
If conventional defect detection methods are used, then detection simplicity is maintained, but large pit defects caused by carbon inclusions cannot be accurately identified
Solution Approach 1:
The patent applies preliminary action in detection by performing carbon inclusion detection and mapping on the substrate surface before epitaxial growth. This preliminary detection creates a defect map that guides subsequent inspection processes, enabling accurate identification of potential large pit defect locations without requiring complex detection systems during final inspection.
Solution Approach 2:
The patent creates a copy or map of the substrate's carbon inclusion distribution pattern before growth. This inclusion map serves as a reference that can be compared with post-growth defect locations, enabling accurate identification of large pit defects caused by carbon inclusions without needing overly complex detection equipment.
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 effectively reduces the density of large pit defects, preventing device failure by accurately identifying and minimizing killer defects in the SiC epitaxial wafer, ensuring improved performance and reliability of SiC-based semiconductor devices.
Implementation Method 1
a confocal microscope with a differential interference optical system for defect detection and identification
Implementation Method 2
a confocal microscope with a differential interference optical system for defect detection and identification
Implementation Method 3
a SiC epitaxial layer has been grown by a chemical vapor deposition (CVD) method
Data Source
AI summary
A SiC epitaxial wafer in which a SiC epitaxial layer is formed on a 4H—SiC single crystal substrate having an off angle and a substrate carbon inclusion density of 0.1 to 6.0 inclusions/cm2, and wherein a density of large pit defects caused by substrate carbon inclusions and contained in the SiC epitaxial layer is 0.5 defects/cm2 or less.