SiC Semiconductor Drift Layer Doping Gradient
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Solution Overview
Problem
Conventional silicon carbide semiconductor devices face challenges in reducing ON resistance and increasing breakdown voltage due to difficulties in controlling the doping concentration distribution in the drift layer, particularly in achieving an ideal distribution for minimizing resistance and maximizing voltage.
Innovation Solution
A silicon carbide semiconductor device with a drift layer featuring a breakdown voltage holding layer where the doping concentration of the dopant continuously decreases and then increases in the film thickness direction, formed through epitaxial growth by adjusting the supply of dopant and carbon atom gases, allowing for a more precise control of doping concentration distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the drift layer has a fixed doping concentration, then the manufacturing process is simple, but the ON resistance cannot be minimized and breakdown voltage cannot be maximized simultaneously
Solution Approach 1:
The patent applies parameter changes by modifying the doping concentration distribution in the drift layer from a fixed value to a continuously varying profile. Specifically, the doping concentration is designed to decrease continuously from the substrate interface toward the surface, with a controlled gradient. This parameter transformation enables simultaneous optimization of ON resistance (through higher doping near the surface) and breakdown voltage (through lower doping near the substrate), resolving the technical contradiction between electrical performance and manufacturing simplicity.
2Reliability
If the drift layer thickness is increased to achieve higher breakdown voltage, then the breakdown voltage increases, but the drift resistance increases and crystal defects increase
Solution Approach 1:
The patent applies local quality by creating spatially varying doping concentrations within the drift layer. The doping concentration is highest near the substrate interface and decreases continuously toward the surface, with the concentration at any point optimized for the local electrical requirements. This local optimization allows different regions of the drift layer to contribute differently: the high-doping region near the substrate provides high breakdown voltage, while the lower-doping region toward the surface reduces drift resistance, thereby resolving the contradiction between breakdown voltage and conduction loss.
3Reliability
If the drift layer thickness is increased to achieve higher breakdown voltage, then the breakdown voltage increases, but the density of crystal defects increases due to lattice distortion
Solution Approach 1:
The patent applies parameter changes by introducing a continuous doping concentration gradient in the drift layer, where the doping concentration decreases from the substrate interface toward the surface. This gradual parameter transformation reduces lattice distortion by providing a smooth transition in the crystal structure, thereby reducing the density of crystal defects. Simultaneously, the optimized doping profile maintains high breakdown voltage, resolving the contradiction between reliability and manufacturing precision.
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 ON resistance and increases breakdown voltage by aligning the doping concentration distribution with ideal values, thereby enhancing the electrical characteristics and reducing crystal defects in the drift layer.
Implementation Method 1
formed through epitaxial growth by adjusting the supply of dopant and carbon atom gases
Data Source
AI summary
A silicon carbide semiconductor device capable of achieving a decrease in ON resistance and an increase in breakdown voltage and a method for manufacturing a silicon carbide semiconductor device. A silicon carbide semiconductor device includes a silicon carbide substrate and a drift layer. The drift layer includes a breakdown voltage holding layer extending from a point where a doping concentration has a predetermined value to a surface of the drift layer. The doping concentration in the breakdown voltage holding layer continuously decreases from the point where the doping concentration has the predetermined value to a modulation point located further toward the surface of the drift layer than a midpoint in a film thickness direction of the breakdown voltage holding layer. The doping concentration in the breakdown voltage holding layer continuously increases from the modulation point to the surface of the drift layer.