SiC Crystal Heavy Metal Doping for Warpage Reduction
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Solution Overview
Problem
The challenge in growing silicon carbide (SiC) single crystals is the occurrence of dislocations due to thermal stress, which leads to warpage when the crystals are sliced into wafers and further dislocations during epitaxial growth, as existing methods cannot completely eliminate stress and are prone to residual stress issues.
Innovation Solution
Incorporating a heavy metal element with a specific gravity higher than iron at a density of 1×10^15 cm^-3 or more in the outer peripheral portion of the SiC single crystal, which reduces the likelihood of dislocations by altering the crystal's mechanical properties and stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional bulk crystal growth method is used, then SiC single crystal can be grown in bulk shape, but dislocations occur due to thermal stress and warpage occurs when sliced into wafers
Solution Approach 1:
The patent applies local quality by introducing heavy metal elements specifically in the outer peripheral portion of the SiC single crystal rather than uniformly throughout. This localized doping concentration (1×10^15 cm^-3 or more) in the outer region suppresses dislocation propagation at the crystal periphery where thermal stress is most pronounced, while maintaining the bulk crystal's growth quality and productivity.
Solution Approach 2:
The patent changes the physical-chemical parameters of the crystal by incorporating heavy metal elements (with specific gravity higher than iron) at controlled concentrations. This parameter modification alters the crystal's mechanical properties and stress distribution characteristics, reducing thermal stress-induced dislocations and warpage during slicing and epitaxial growth.
2Manufacturing precision
If heavy metal element is added to suppress dislocations, then crystal quality improves, but manufacturing complexity increases
Solution Approach 1:
The patent modifies the gas composition parameters during bulk crystal growth by introducing heavy metal elements at controlled concentrations. This parameter adjustment in the growth environment enables dislocation suppression without requiring complex post-growth processing or specialized equipment, maintaining process simplicity while improving crystal quality.
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 effectively suppresses the generation and propagation of dislocations, resulting in reduced warpage and enhanced mechanical stability of the SiC single crystals, even when sliced into wafers and subjected to high-temperature epitaxial growth, thereby improving the quality of the SiC crystal growth process.
Implementation Method 1
Incorporating a heavy metal element with a specific gravity higher than iron at a density of 1×10^15 cm^-3 or more in the outer peripheral portion of the SiC single crystal, which reduces the likelihood of dislocations by altering the crystal's mechanical properties and stress distribution
Implementation Method 2
This approach effectively suppresses the generation and propagation of dislocations, resulting in reduced warpage and enhanced mechanical stability of the SiC single crystals, even when sliced into wafers and subjected to high-temperature epitaxial growth
Data Source
AI summary
A silicon carbide single crystal contains a heavy metal element having a specific gravity higher than a specific gravity of iron. An addition density of the heavy metal element at least in an outer peripheral portion of the silicon carbide single crystal is set to 1×1015 cm−3 or more.