SiC MOSFET Body Doping Profile for Lower Interface Scattering
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Solution Overview
Problem
Silicon carbide-based transistor devices face challenges due to interface defects between the silicon carbide body and gate insulator, leading to poor channel quality, lower electron mobility, and increased on-resistance, which affects their high-voltage and high-temperature performance.
Innovation Solution
The transistor device features a body region with specific subregions of varying carrier concentrations, achieved through ion implantation, where the carrier concentration decreases and then increases away from the gate insulator, shifting the channel formation away from the interface and reducing interface scattering, along with a gate insulator that covers the gate and body region, and a manufacturing method that forms a gate trench and implants doped substances at non-zero angles to create the desired carrier concentration profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional gate insulator structure is used in silicon carbide transistors, then the device can be manufactured with standard processes, but interface defects occur between the silicon carbide body and gate insulator, leading to poor channel quality and increased on-resistance
Solution Approach 1:
The body region is divided into three subregions with different carrier concentrations: a first subregion adjacent to the gate insulator with lower carrier concentration to reduce interface scattering, a second subregion in the middle with intermediate carrier concentration, and a third subregion away from the gate insulator with higher carrier concentration. This local variation in carrier concentration optimizes channel quality at the critical interface region while maintaining overall device functionality.
Solution Approach 2:
The carrier concentration in the body region is changed as a continuous parameter across the three subregions. By gradually varying the carrier concentration from the interface toward the bulk, the invention reduces interface scattering effects while maintaining adequate channel conductivity, thereby improving channel quality without requiring non-standard manufacturing processes.
2Device complexity
If the channel is formed near the gate insulator interface, then the device structure is simple, but interface scattering increases, leading to lower electron mobility and higher on-resistance
Solution Approach 1:
The body region is divided into three subregions with different carrier concentrations: a first subregion adjacent to the gate insulator with lower carrier concentration to reduce interface scattering, a second subregion in the middle with intermediate carrier concentration, and a third subregion away from the gate insulator with higher carrier concentration. This local variation in carrier concentration optimizes channel quality at the critical interface region while maintaining overall device functionality.
Solution Approach 2:
Instead of forming the channel in a single plane near the interface, the invention creates a three-dimensional carrier concentration gradient extending from the interface into the bulk. This dimensional approach allows the channel to benefit from reduced interface scattering while maintaining adequate conductivity through the graded structure.
3Ease of manufacture
If uniform carrier concentration is maintained in the body region, then the manufacturing process is simple, but on-resistance increases due to interface scattering effects
Solution Approach 1:
The body region is divided into three subregions with different carrier concentrations: a first subregion adjacent to the gate insulator with lower carrier concentration to reduce interface scattering, a second subregion in the middle with intermediate carrier concentration, and a third subregion away from the gate insulator with higher carrier concentration. This local variation in carrier concentration optimizes channel quality at the critical interface region while maintaining overall device functionality.
Solution Approach 2:
The doping process is designed to create the three-subregion carrier concentration profile before device operation. By preliminarily establishing the graded carrier concentration distribution, the invention prevents interface scattering effects from degrading performance, rather than attempting to correct the problem after device fabrication.
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 reduces channel resistance and improves the performance of silicon carbide MOSFET devices by avoiding interface scattering and enhancing carrier mobility, resulting in higher drain current and better switching characteristics.
Implementation Method 1
The gate insulator covers the bottom surface and at least a portion of the side surfaces of the gate, the gate insulator comprises a sidewall and a bottom
Implementation Method 2
injecting a doped substance into the initial body region by an ion implantation process
Implementation Method 3
silicon carbide has a higher critical electric field, that is, the electric field of avalanche breakdown
Data Source
AI summary
Disclosed are a transistor device and a manufacturing method thereof. The transistor device includes a gate, a gate insulator, and a drift region stacked with the body region in a first direction, the gate insulator covers the bottom surface and at least a portion of the side surface of the gate, the body region covers a portion of the sidewall of the gate insulator, and the gate insulator is extended from the surface of the drift region facing the body region to the drift region along the first direction; the body region comprises a first subregion, a second subregion and a third subregion arranged sequentially along a second direction, an average carrier concentration in the first subregion and an average carrier concentration in the third subregion are greater than an average carrier concentration in the second subregion.