SiC Semiconductor Buffer Layer for ON Resistance Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High energy generated by hole-electron recombination at basal plane dislocations in semiconductor devices leads to defect propagation and increased ON resistance, while introducing defect energy-levels in the drift layer reduces minority carriers, causing conduction loss and resistivity issues during bipolar operation.
Innovation Solution
A semiconductor device with a high-resistance first semiconductor region and a recombination promoting layer having a higher impurity concentration and a defect energy-level, specifically using a carbon vacancy defect energy-level, is introduced between the substrate and the drift layer to manage recombination and reduce defect expansion, while maintaining low resistivity during bipolar operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conversion layer structure is used to convert basal plane dislocations into threading edge dislocations, then ON resistance degradation is prevented, but defect propagation occurs due to high energy generated by hole-electron recombination at the buffer layer-conversion layer interface
Solution Approach 1:
The invention introduces a buffer layer as an intermediary between the substrate and the conversion layer. This buffer layer absorbs and dissipates the high energy generated by hole-electron recombination, preventing it from propagating defects to the conversion layer and substrate while allowing the conversion layer to maintain its BPD-to-TED conversion function
Solution Approach 2:
The invention segments the previously unified substrate-conversion layer structure into three distinct layers: substrate, buffer layer, and conversion layer. This segmentation isolates the high energy recombination events to the buffer layer region, protecting the conversion layer from defect propagation while maintaining the overall device structure
2Object-generated harmful factors
If defect energy-levels are introduced in the drift layer to kill minority carriers, then recombination at substrate BPDs is reduced, but conduction loss increases due to reduced minority carriers in the drift layer
Solution Approach 1:
The invention applies local quality by introducing defect energy-levels only in the buffer layer region, not in the drift layer. This localized approach allows minority carrier recombination to occur where needed (at the buffer layer-conversion layer interface) while preserving minority carrier concentration in the drift layer for efficient bipolar operation
Solution Approach 2:
The invention changes the spatial distribution parameter of defect energy-levels, concentrating them specifically in the buffer layer with a density of at least 1×10^12/cm³, while keeping the drift layer free of such defects. This parameter change enables selective recombination promotion without compromising drift layer conductivity
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 configuration prevents degradation of ON resistance characteristics and conduction loss by promoting recombination in the buffer layer, reducing minority carrier loss and suppressing basal plane dislocation expansion, thereby maintaining low resistance during bipolar operation.
Implementation Method 1
high energy is generated at the time of hole-electron recombination due to the wide bandgap
Implementation Method 2
introducing a defect energy-level, which acts as a recombination site
Data Source
AI summary
A semiconductor device includes an n−-type drift layer of an formed on an n+-type SiC substrate; a p-type layer provided on a surface opposite that facing the n+-type SiC substrate; and an n-type buffer layer provided, as a recombination promoting layer, between the n−-type drift layer and the n+-type SiC substrate, the n-type buffer layer having an impurity concentration higher than that of the n−-type drift layer. In the buffer layer, as a recombination site, a defect energy-level is introduced at a high concentration of 1×1012/cm3 or higher. The buffer layer promotes internal electron-hole recombination and without applying high energy to BPDs at an interface of the buffer layer and the SiC substrate, may reduce the amount of recombination near the interface even at a current density equivalent to that of a conventional structure and thereby, prevents characteristics degradation at the time of operation.