Oxide MOSFET Layer Structure for High Breakdown Voltage
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Solution Overview
Problem
Conventional semiconductor devices face challenges in achieving high withstand voltage performance, particularly when using gallium oxide-based materials, due to limitations in current blocking layers and crystal defect regions.
Innovation Solution
A semiconductor device is designed with a crystalline oxide semiconductor layer having a multilayer structure, including a drift layer, channel layer, and source layer, where a trench penetrates the source and channel layers, and a gate electrode is positioned in the trench across a gate insulating film. A current blocking layer with a different composition than the drift layer is used between the channel and drift layers, enhancing voltage withstand capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-layer drift layer structure is used, then the device structure is simple, but the withstand voltage performance is insufficient
Solution Approach 1:
The drift layer is segmented into multiple sub-layers with different doping concentrations and thicknesses. Specifically, the drift layer includes a first drift layer with lower doping concentration and a second drift layer with higher doping concentration, creating a graded structure that distributes the electric field more effectively across the device, thereby enhancing breakdown voltage while maintaining manageable structural complexity
Solution Approach 2:
The patent employs composite oxide semiconductor materials with different bandgaps and electrical properties in each drift layer sub-layer. The first drift layer uses a material composition optimized for high voltage blocking, while the second drift layer uses a different composition that balances voltage handling with conductivity requirements, creating a composite structure that achieves superior withstand voltage performance
2Reliability
If the current blocking layer has the same composition as the drift layer, then the manufacturing process is simpler, but the current blocking effect is insufficient
Solution Approach 1:
The current blocking layer is designed with a distinct composition and doping profile that differs from the drift layer. It features a higher doping concentration and specific material composition optimized for creating a strong depletion region, providing localized current blocking functionality at the critical interface between the drift layer and channel layer, while the rest of the device maintains appropriate material properties for their respective functions
Solution Approach 2:
The patent changes key material parameters including doping concentration, carrier density, and bandgap energy between the drift layer and current blocking layer. The current blocking layer employs significantly higher doping concentrations (e.g., 1×10^19 to 1×10^21 atoms/cm³) compared to the drift layer, creating a sharp parameter transition that enhances the blocking effect while allowing standard semiconductor fabrication techniques to be used
3Reliability
If the drift layer has high doping concentration, then the on-resistance is reduced, but the breakdown voltage decreases
Solution Approach 1:
The drift layer is divided into multiple segments with progressively varying doping concentrations. The first drift layer has lower doping concentration to maintain high breakdown voltage, while the second drift layer has higher doping concentration to reduce on-resistance. This segmentation allows each sub-layer to optimize for its specific function, achieving both high voltage handling and low conduction loss
Solution Approach 2:
The patent implements a graded parameter change across the drift layer thickness, transitioning from lower doping concentration near the high-voltage interface to higher doping concentration toward the channel region. This gradual parameter modulation creates an optimized electric field distribution that simultaneously enhances breakdown voltage and reduces on-state resistance, avoiding the trade-off present in uniform doping structures
Data Source
AI summary
Provided a semiconductor device includes at least: a crystalline oxide semiconductor layer including a channel layer and a drift layer; and a gate electrode arranged over the channel layer across a gate insulating film, and has a current blocking layer between the channel layer and the drift layer. The semiconductor device is characterized in that the drift layer contains a first crystalline oxide as a major component, the current blocking layer contains a second crystalline oxide as a major component, and the first crystalline oxide and the second crystalline oxide have different compositions.