SiC Semiconductor Structure for High-Voltage Reliability
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Solution Overview
Problem
Conventional semiconductor power devices using SiC struggle to achieve high withstand voltage and low loss due to high resistance in p-type silicon carbide single crystal substrates, which limits their mechanical strength and performance in high-voltage applications.
Innovation Solution
A p-type silicon carbide single crystal layer with an impurity concentration of 1×10^19 cm^-3 or higher and a thickness of 50 μm or greater is grown using epitaxial growth techniques, combined with an n-type silicon carbide single crystal layer to form a semiconductor structure with a p/n junction, enhancing mechanical strength and reducing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p-type silicon carbide single crystal substrate is used, then the semiconductor device can be fabricated, but the resistance is high and mechanical strength is insufficient
Solution Approach 1:
The invention divides the substrate into two separate layers: a thick n-type drift layer (100 μm or more) that provides mechanical strength, and a thinner p-type layer (1-10 μm) that provides the desired electrical properties. This segmentation allows each layer to optimize its function without compromising the other.
Solution Approach 2:
The invention creates a composite structure by combining n-type and p-type silicon carbide layers with different thicknesses and doping concentrations. The n-type layer serves as a mechanical support with high strength, while the p-type layer provides the necessary electrical characteristics for the semiconductor device operation.
2Reliability
If the drift layer thickness is increased to 100 μm or more for high withstand voltage, then the breakdown voltage increases, but the resistance becomes unignorable
Solution Approach 1:
The invention applies different doping types and concentrations to different regions of the semiconductor structure. The n-type drift layer has low doping concentration (1×10^15 to 1×10^13 cm^-3) optimized for high breakdown voltage, while the p-type layer has higher doping concentration (1×10^18 to 1×10^20 cm^-3) optimized for low resistance and high conductivity modulation capability.
Solution Approach 2:
The invention changes the doping concentration parameter significantly between layers: the n-type drift layer maintains very low doping (1×10^15 to 1×10^13 cm^-3) for high voltage capability, while the p-type layer uses high doping (1×10^18 to 1×10^20 cm^-3) to reduce resistance and enable effective conductivity modulation, thereby reducing on-state resistance.
3Ease of operation
If a p-type drift layer is used in bipolar-operation devices, then conductivity modulation is applicable, but the On resistance is higher than n-type devices
Solution Approach 1:
The invention creates a dynamic structure where the p-type layer can be selectively activated. During device operation, the p-type layer provides conductivity modulation when needed, while the thick n-type drift layer continuously provides mechanical support and maintains low base resistance, enabling the device to dynamically switch between different conduction modes.
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
The approach results in a semiconductor structure with excellent mechanical strength and low resistance during electric conduction, suitable for high-voltage applications such as IGBT semiconductor devices, enabling efficient power conversion with reduced losses.
Implementation Method 1
a p-type silicon carbide single crystal layer which has an α-type crystal structure, contains aluminum at an impurity concentration of 1×10^19 cm^-3 or higher, and has a thickness of 50 μm or greater
Implementation Method 2
combined with an n-type silicon carbide single crystal layer to form a semiconductor structure with a p/n junction
Data Source
AI summary
The present invention provides a semiconductor structure which includes at least a p-type silicon carbide single crystal layer having an α-type crystal structure, containing aluminum at impurity concentration of 1×1019 cm−3 or higher, and having thickness of 50 μm or greater. Further provided is a method for producing the semiconductor structure of the present invention which method includes at least epitaxial growth step of introducing silicon carbide source and aluminum source and epitaxially growing p-type silicon carbide single crystal layer over a base layer made of silicon carbide single crystal having α-type crystal structure, wherein the epitaxial growth step is performed at temperature conditions of from 1,500° C. to 1,700° C., and pressure conditions of from 5×103 Pa to 25×103 Pa.