SiC Crystal Defect Reduction via Carbon Interstitial Diffusion
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Solution Overview
Problem
SiC crystal layers contain native intrinsic defects that act as carrier traps, degrading material characteristics, and are difficult to remove due to high thermal stability, especially in thick layers required for cost-effectiveness, where existing annealing methods are insufficient in reducing defect concentration.
Innovation Solution
Introducing excess carbon interstitials into the SiC crystal layer through ion implantation and subsequent high-temperature annealing to diffuse and combine with vacancies, making electrically active defects inactive and reducing carrier trapping centers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high temperature annealing is applied to remove intrinsic defects, then defect concentration is reduced to some extent, but the improvement is insufficient due to high thermal stability of SiC
Solution Approach 1:
Carbon interstitials are introduced as intermediary atoms that mediate the annealing process. These carbon interstitials act as mobile species that can combine with and eliminate intrinsic defects (vacancies and antisites) at lower temperatures than conventional annealing, thereby improving defect removal efficiency without requiring extremely high temperatures
Solution Approach 2:
The patent changes the chemical composition parameter by introducing excess carbon interstitials into the SiC crystal structure. This compositional modification enables defect elimination through a different mechanism (carbon interstitial-mediated annealing) that is more effective than thermal annealing alone, allowing quality improvement without excessively increasing temperature
2Productivity
If growth rate and growth temperature are increased to achieve cost-effective thick layers, then productivity is improved, but intrinsic defect concentration is increased
Solution Approach 1:
Carbon interstitials are introduced into the SiC crystal structure before the annealing process. This preliminary introduction of carbon interstitials prepares the material to undergo more effective defect elimination during subsequent annealing, allowing high-quality thick layers to be produced without compromising on growth rate or temperature
Solution Approach 2:
Carbon interstitials serve as intermediary species that enable more effective defect removal during annealing. By introducing these mobile carbon atoms beforehand, the subsequent annealing process can eliminate intrinsic defects more efficiently, thereby reducing the defect concentration that would normally result from high growth rates and temperatures
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
Significantly reduces or eliminates carrier trapping centers, improving carrier lifetime and semiconductor device quality by making defects inactive, particularly effective in bipolar devices.
Implementation Method 1
heating the SiC crystal for making the carbon interstitials that have been additionally introduced into the surface layer to diffuse out from the surface layer into a deep portion (bulk layer)
Implementation Method 2
carrying out ion implantation of certain atoms into a shallow surface layer of the SiC crystal layer to additionally introduce carbon interstitials into the surface layer
Implementation Method 3
heating the SiC crystal for making the carbon interstitials that have been additionally introduced into the surface layer to diffuse out from the surface layer into a deep portion (bulk layer) and for combining the carbon interstitials and point defects
Data Source
AI summary
A method for improving the quality of a SiC layer by effectively reducing or eliminating the carrier trapping centers in the as-grown SiC crystal. The method includes the steps of: (a) carrying out ion implantation of carbon atoms, silicon atoms, hydrogen atoms, or helium atoms into a shallow surface layer of the SiC crystal layer to introduce carbon interstitials into the surface layer, and (b) growing the SiC layer upward from the edge face of the surface layer into which the carbon interstitials have been introduced, and diffusing out the carbon interstitials that have been introduced into the surface layer from the surface layer into the grown layer and combining the carbon interstitials and point defects to make the electrically active point defects in the grown layer inactive.