SiC Epitaxial Substrate Impurity Control
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Solution Overview
Problem
Current methods for producing single crystal silicon carbide (SiC) epitaxial substrates face challenges in achieving ultrahigh-voltage, low-loss devices, particularly in forming low-concentration epi deposited films with impurity concentrations below 1×10^15/cm^3, as conventional techniques often result in higher impurity concentrations due to contamination from equipment impurities like nitrogen and boron.
Innovation Solution
A silicon carbide semiconductor substrate and manufacturing method that involves controlling the flowrates of nitrogen and boron dopant gases during epitaxial growth to achieve a donor concentration and acceptor concentration difference within the range of 1×10^14/cm^3 to 1×10^15/cm^3, ensuring these concentrations are equal to or higher than those unaffected by impurities in the growth equipment, thereby reducing equipment-induced impurities and allowing for precise carrier lifetime control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional epitaxial growth techniques are used, then single crystal SiC epi substrates can be produced, but the impurity concentration cannot be reduced below 1×10^15/cm^3 due to equipment impurities
Solution Approach 1:
The patent applies parameter changes by precisely controlling the flowrates of dopant gases (nitrogen and boron) during epitaxial growth. By adjusting these flowrate parameters, the invention achieves donor and acceptor concentrations that are equal to or higher than equipment impurity levels, with a difference ranging from 1×10^14/cm^3 to 1×10^15/cm^3, thereby overcoming the limitation of equipment impurity contamination
Solution Approach 2:
The patent employs feedback control by measuring the actual donor and acceptor concentrations in the epi layer and adjusting the dopant gas flowrates accordingly. This closed-loop approach ensures that the impurity concentration is maintained within the target range despite variations in equipment impurities, achieving precise concentration control below 1×10^15/cm^3
2Reliability
If low-concentration epi deposited films are formed to achieve ultrahigh-voltage devices, then device voltage capability improves, but manufacturing precision deteriorates due to difficulty in controlling impurity concentrations
Solution Approach 1:
The patent achieves both ultrahigh-voltage device performance and precise impurity control by changing the parameters of dopant gas flowrates. This allows formation of epi layers with controlled donor and acceptor concentrations (difference of 1×10^14/cm^3 to 1×10^15/cm^3), enabling low-loss 10 kV devices with reliable performance
Solution Approach 2:
The patent replaces conventional mechanical/physical impurity control methods with chemical control through precise dopant gas flowrate management. By controlling the chemical composition and flowrates of nitrogen and boron dopant gases, the invention achieves superior concentration control compared to traditional physical isolation methods
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 enables the formation of low-impurity-concentration epi deposited films with impurity concentrations between 1×10^14/cm^3 and 1×10^15/cm^3, effectively reducing equipment impurity effects and enabling the production of high-voltage semiconductor devices with improved performance.
Implementation Method 1
forming a film of a single crystal silicon carbide on a single crystal silicon carbide substrate by epitaxial growth
Implementation Method 2
supplying a dopant gas including a donor and an acceptor, and forming a film of a single crystal silicon carbide on a single crystal silicon carbide substrate by epitaxial growth
Data Source
AI summary
A silicon carbide semiconductor substrate includes an epitaxial layer. A difference of a donor concentration and an acceptor concentration of the epitaxial layer is within a range from 1×1014/cm3 to 1×1015/cm3. Further, the donor concentration and the acceptor concentration of the epitaxial layer are a concentration unaffected by an impurity inside epitaxial growth equipment.