SiC Single Crystal Stress Reduction via Inert Atmosphere Annealing
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Solution Overview
Problem
SiC single crystal substrates experience warpage due to both processing strain and internal stress during ingot growth, which becomes more pronounced as the substrate diameter increases, leading to excessive etching and thinning issues when heat-treated at high temperatures to reduce stress.
Innovation Solution
A method involving heating SiC single crystals at 1800°C or higher in an atmosphere containing Si and C elements within a semi-closed space with inert gases to reduce internal stress while minimizing SiC sublimation, using a heating furnace capable of uniform temperature distribution to control temperature gradients and vapor pressure environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the SiC single crystal substrate is annealed at high temperature (above 2000°C) to reduce internal stress, then the internal stress is reduced, but surface carbonization becomes more pronounced due to pyrolysis reaction caused by sublimation
Solution Approach 1:
The patent applies inert atmosphere by conducting annealing treatment in a nitrogen atmosphere. This prevents oxygen from participating in the pyrolysis reaction, thereby suppressing surface carbonization while still enabling internal stress reduction through the high-temperature annealing process
Solution Approach 2:
The patent changes the chemical environment parameter by introducing nitrogen atmosphere instead of vacuum or oxygen atmosphere. This parameter change modifies the reaction pathway during high-temperature treatment, allowing stress reduction without excessive surface carbonization
2Stress or pressure
If the SiC single crystal substrate is heated in a temperature range close to ingot growth (1800°C or higher) to reduce internal stress, then the internal stress is reduced, but excessive etching and thinning of the substrate occurs due to SiC sublimation
Solution Approach 1:
The patent uses nitrogen atmosphere to suppress SiC sublimation during high-temperature heating. The inert environment prevents the sublimation-driven material loss while still allowing the thermal energy to reduce internal stress in the substrate
Solution Approach 2:
The patent converts the potentially harmful effect of high-temperature heating (which causes sublimation and material loss) into a beneficial process by controlling the atmosphere. The high temperature is maintained for stress reduction, while the nitrogen atmosphere prevents the harmful sublimation pathway
3Area of stationary object
If the diameter of the SiC single crystal substrate increases, then the substrate size is increased for larger devices, but the warpage caused by internal stress becomes more apparent
Solution Approach 1:
The patent applies preliminary action by performing annealing treatment before device fabrication. This preliminary heat treatment reduces internal stress in advance, preventing warpage from developing during subsequent processing steps, especially important for large-diameter substrates
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 reduces internal stress in SiC single crystals, suppresses sublimation, and achieves a warpage amount of less than 30 μm in substrates with diameters of 6 inches or more, contributing to the production of high-quality SiC devices with reduced defect formation.
Implementation Method 1
a stress reduction step of heating a SiC single crystal at 1800° C. or higher in an atmosphere containing Si and C elements to reduce internal stress in the SiC single crystal
Implementation Method 2
heating in this temperature range causes excessive etching and thinning of the SiC single crystal substrate due to SiC sublimation
Implementation Method 3
heating a SiC single crystal at 1800° C. or higher in an atmosphere containing Si and C elements to reduce internal stress in the SiC single crystal
Data Source
AI summary
An object of the present invention is to provide a novel SiC single crystal with reduced internal stress while suppressing SiC sublimation. In order to solve the above problems, the present invention provides a method for producing SiC single crystals, including a stress reduction step of heating a SiC single crystal at 1800° C. or higher in an atmosphere containing Si and C elements to reduce internal stress in the SiC single crystal. With this configuration, the present invention can provide a novel SiC single crystal with reduced internal stress while suppressing SiC sublimation.