SiC Epitaxial Wafer Growth for Carbon Inclusion Defect Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Triangular defects in SiC epitaxial wafers, caused by substrate carbon inclusions, render portions of the wafer unusable as they have different electrical properties than the 4H polymorph, and large pit defects are also device killers, necessitating a reduction in their density and identification method.
Innovation Solution
Producing SiC epitaxial wafers with a 4H-SiC single crystal substrate having an off-angle and controlled substrate carbon inclusion density, where the epitaxial growth conditions such as growth rate, temperature, and C/Si ratio are optimized to minimize large pit and triangular defects, and using a confocal microscope with differential interference optical system for defect identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional epitaxial growth is performed on SiC single crystal substrates, then SiC epitaxial layers can be produced, but triangular defects and large pit defects occur which render portions of the wafer unusable
Solution Approach 1:
The patent applies preliminary action by controlling substrate preparation before epitaxial growth. Specifically, the substrate surface treatment and cleaning processes are optimized in advance to remove carbon inclusions and defects before the epitaxial growth begins, preventing triangular and large pit defects from forming during growth
Solution Approach 2:
The patent applies parameter changes by optimizing epitaxial growth conditions including temperature, pressure, gas flow rates, and C/Si ratio. By adjusting these parameters, the growth process suppresses defect formation while maintaining high-quality epitaxial layer production
2Productivity
If substrate carbon inclusion density is high, then more epitaxial layers can be produced, but the density of triangular and large pit defects increases
Solution Approach 1:
The patent applies parameter changes by controlling the C/Si ratio during epitaxial growth and optimizing growth temperature. These parameter adjustments suppress the formation of triangular and large pit defects even when producing high volumes of wafers, maintaining low defect density while increasing productivity
Solution Approach 2:
The patent applies continuity of useful action by implementing consistent substrate preparation procedures and maintaining stable epitaxial growth conditions throughout continuous production. This ensures that defect suppression is maintained across multiple wafers produced in sequence
3Measurement precision
If defect identification is performed using conventional methods, then some defects can be detected, but triangular defects and large pit defects caused by substrate carbon inclusions are difficult to distinguish from other defects
Solution Approach 1:
The patent applies color changes by utilizing photoluminescence imaging where different defect types exhibit distinct luminescence characteristics. Triangular defects and large pit defects show different photoluminescence signals compared to other defects, enabling visual differentiation and identification
Solution Approach 2:
The patent applies copying by creating optical images of the substrate surface using confocal microscopy and photoluminescence imaging. These images serve as copies that reveal defect locations and characteristics, allowing identification of triangular and large pit defects caused by substrate carbon inclusions
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 reduces the density of device-killing large pit and triangular defects to 0.6 defects/cm2 or less, enabling the production of high-quality SiC epitaxial wafers suitable for semiconductor devices and providing an effective defect identification technique.
Implementation Method 1
using a confocal microscope with differential interference optical system for defect identification
Implementation Method 2
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, wherein a total density of large pit defects and triangular defects caused by substrate carbon inclusions and contained in the SiC epitaxial layer is 0.01 defects/cm2 or more and 0.6 defects/cm2 or less. The large pit defect is a pit located on a surface at a position corresponding to a position of the carbon inclusion on the substrate surface, and a conversion rate from the substrate carbon inclusions to the large pit defects and the triangular defects caused by the substrate carbon inclusions is 20% or less. Also disclosed is a method for producing the SiC epitaxial wafer.