Trench MOSFET N-Type Region Segmentation for Breakdown Voltage
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Solution Overview
Problem
Power semiconductor devices face challenges in achieving low on resistance and high breakdown voltage, leading to increased on resistance and decreased forward current density due to the requirements for a thick and low concentration epitaxial layer or drift region.
Innovation Solution
A semiconductor device structure with a trench and specific doping regions, including an n-type layer, p-type regions, and a gate electrode, where the n-type region has a first portion parallel to the substrate surface and a second portion extending vertically, with varying depths and doping concentrations, to disperse current and maintain breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the epitaxial layer or drift region is made thick and low concentration to achieve high breakdown voltage, then breakdown voltage is improved, but on resistance increases and forward current density decreases
Solution Approach 1:
The n-type region is divided into two distinct portions: a first portion with lower doping concentration that extends to the trench side surface for high voltage support, and a second portion with higher doping concentration that extends vertically for low resistance current conduction. This segmentation allows each portion to fulfill different functional requirements simultaneously.
Solution Approach 2:
Different regions of the n-type structure are assigned different doping concentrations based on their specific functional requirements. The first portion near the trench has lower concentration for electrical isolation and breakdown voltage, while the second portion has higher concentration for reducing on-resistance and improving current density.
2Reliability
If the epitaxial layer or drift region is made thick and low concentration to achieve high breakdown voltage, then breakdown voltage is improved, but forward current density decreases
Solution Approach 1:
The n-type region is divided into two distinct portions: a first portion with lower doping concentration that extends to the trench side surface for high voltage support, and a second portion with higher doping concentration that extends vertically for low resistance current conduction. This segmentation allows each portion to fulfill different functional requirements simultaneously.
Solution Approach 2:
Different regions of the n-type structure are assigned different doping concentrations based on their specific functional requirements. The first portion near the trench has lower concentration for electrical isolation and breakdown voltage, while the second portion has higher concentration for reducing on-resistance and improving current density.
3Reliability
If a trench structure is introduced to improve device performance, then breakdown voltage and current density are improved, but device complexity increases
Solution Approach 1:
The n-type region is divided into two distinct portions: a first portion with lower doping concentration that extends to the trench side surface for high voltage support, and a second portion with higher doping concentration that extends vertically for low resistance current conduction. This segmentation allows each portion to fulfill different functional requirements simultaneously.
Solution Approach 2:
The n-type region extends in multiple dimensions: horizontally along the trench side surface and vertically downward beyond the trench depth. This multi-dimensional configuration allows the structure to achieve both electrical isolation and low resistance conduction pathways.
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 solution significantly improves breakdown voltage by 318% and current density by 21%, while reducing on resistance by 19%, enhancing overall performance index and reducing conductor area and production costs.
Implementation Method 1
the n type region includes a first portion in contact with the side surface of the trench and extending parallel to an upper surface of the substrate and a second portion in contact with the first portion, separated from the side surface of the trench, and extending in a direction vertical to the upper surface of the substrate
Implementation Method 2
According to a Poisson equation, since the high breakdown voltage of the power semiconductor device is required, the epitaxial layer or the drift region of the low concentration and the thick thickness are required thus causing on resistance to increase and a foreword direction current density to decrease
Data Source
AI summary
A semiconductor device is provided and includes an n− type layer disposed at a substrate first surface. A trench, n type region, and p+ type region are disposed on the n− type layer. A p type region is disposed on the n type region. An n+ type region is disposed on the p type region. A gate insulating layer is disposed in the trench. A gate electrode is disposed on the gate insulating layer. A source electrode is disposed on an insulating layer disposed on the gate electrode, n+ type region, and p+ type region. A drain electrode is disposed at a substrate second surface. The n type region includes a first portion contacting the trench side surface and extending parallel to a substrate upper surface and a second portion contacting the first portion, separated from the trench side surface, and extending vertical to the substrate upper surface.