Buried Layer Segmentation in Power MOSFETs
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Solution Overview
Problem
Conventional power MOSFETs, particularly double-diffused MOSFETs, face limitations in achieving high breakdown voltage and low turn-off resistance, which affects their performance in power switching applications.
Innovation Solution
The semiconductor device incorporates a specific structure with a gate, source, body, and drain regions, along with buried layers and an epitaxial semiconductor layer, to enhance breakdown voltage and reduce turn-off resistance by forming depletion regions and optimizing current paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional double-diffused MOSFET structure is used, then manufacturing simplicity is maintained, but breakdown voltage is limited and turn-off resistance is high
Solution Approach 1:
The buried layer structure is segmented into multiple regions with different conductivity types and doping concentrations. The first buried layer (opposite conductivity type) and second buried layers (same conductivity type as drift region) are spatially separated and have different doping levels, creating distinct functional zones that collectively enhance breakdown voltage while managing resistance characteristics
Solution Approach 2:
Different regions of the buried layer structure are assigned different doping concentrations and conductivity types to perform specific functions. The first buried layer has higher doping concentration for one function, while the second buried layers have lower doping concentration for another function, optimizing local electrical properties to achieve overall performance improvement
2Reliability
If higher doping concentration is used in buried layers, then turn-off resistance is reduced, but breakdown voltage decreases
Solution Approach 1:
The buried layer system is divided into multiple segments with different doping concentrations. The first buried layer has higher doping concentration to reduce turn-off resistance, while the second buried layers have lower doping concentration to maintain breakdown voltage, allowing both conflicting requirements to be satisfied simultaneously in different spatial locations
Solution Approach 2:
The doping concentration parameter is varied across different buried layer regions. By changing the doping concentration from high in the first buried layer to low in the second buried layers, the patent optimizes the balance between turn-off resistance and breakdown voltage, achieving both improved reliability and maintained strength
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 increases the breakdown voltage and reduces turn-on resistance, improving the overall performance of the semiconductor device in power switching applications.
Implementation Method 1
forming depletion regions and optimizing current paths
Implementation Method 2
a first buried layer under the drift region in the substrate, the first buried layer extending in the first and second directions; and a plurality of second buried layers between the first buried layer and the drift region in the substrate
Data Source
AI summary
A semiconductor device comprises a substrate and a gate which extends on the substrate in a first horizontal direction. A source region is positioned at a first side of the gate and extends in the first direction. A body region of a first conductivity type is under the source region and extends in the first direction. A drain region of a second conductivity type is at a second side of the gate and extends in the first direction. A drift region of the second conductivity type extends between the body region and the drain region in the substrate in a second horizontal direction. A first buried layer is under the drift region in the substrate, the first buried layer extending in the first and second directions. A plurality of second buried layers is between the first buried layer and the drift region in the substrate. The second buried layers extend in the second direction and are spaced apart from each other in the first direction.