Vertical MOSFET Edge Termination With Shielded Trench Layout
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Solution Overview
Problem
Conventional vertical power MOSFETs with trench gate structures face challenges in achieving high blocking voltage while maintaining low resistance, as the edge termination structure requires high implantation energies and is sensitive to doping deviations, leading to potential early electrical breakdown due to high electric fields at the periphery.
Innovation Solution
A vertical semiconductor component with a trench structure and a shielding structure having varying thickness regions, where the edge termination structure is situated between the drift region and the shielding structure, reducing the need for higher implantation energies and enhancing the breakdown voltage by distributing the space-charge region effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the edge termination structure is designed to achieve high blocking voltage, then the breakdown voltage increases, but the implantation energy requirement increases and doping precision sensitivity increases
Solution Approach 1:
The edge termination structure is divided into multiple doped regions with different doping concentrations and depths. The first doped region has a first doping concentration and the second doped region has a second doping concentration, creating a segmented doping profile that distributes the electric field more effectively without requiring excessive implantation energy
Solution Approach 2:
Different regions of the edge termination structure are doped with different concentrations tailored to their specific functional requirements. The first doped region uses one doping concentration while the second doped region uses another, optimizing each local area's performance rather than using a uniform doping approach throughout
2Length of stationary object
If the edge termination structure uses high implantation energies to achieve deep doping, then the doping depth increases, but the sensitivity to doping deviations increases leading to early electrical breakdown
Solution Approach 1:
The doping process is segmented into multiple regions with different concentrations. The first doped region extends to a first depth with a first doping concentration, while the second doped region extends to a second depth with a second doping concentration. This segmentation allows each region to be optimized independently, reducing the sensitivity to doping deviations in any single region
Solution Approach 2:
The doping concentration is varied across different regions rather than maintaining a uniform concentration. By changing the doping parameter from a single value to multiple values across different regions, the structure achieves both sufficient doping depth and reduced sensitivity to doping process variations
3Reliability
If deep p+ regions are provided in the edge region to protect gate oxide from high fields, then the gate oxide reliability improves, but the vertical current flow is constricted increasing forward resistance
Solution Approach 1:
The doping concentration is locally optimized: deep p+ regions are provided where needed for gate oxide protection, while other regions maintain lower doping concentrations to preserve current flow. This local differentiation allows simultaneous achievement of gate oxide reliability and low forward resistance
Solution Approach 2:
The semiconductor structure is divided into functionally distinct doped regions. Some regions have deep p+ doping for field protection while other regions have different doping characteristics optimized for current conduction, separating the protective function from the conductive function in different spatial locations
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 excessive field strength at the periphery, preventing early electrical breakdown and increasing the avalanche breakdown voltage without requiring higher implantation energies, thus optimizing the semiconductor component's performance in power electronics applications.
Implementation Method 1
Since the diffusion constant of dopants is very low in SiC, the regions to be doped must be produced with the aid of an implantation without the option of utilizing the diffusion available with silicon for driving the dopants into the depth.
Implementation Method 2
The activation of dopants is subsequently realized with the aid of a temperature step.
Implementation Method 3
This configuration reduces excessive field strength at the periphery, preventing early electrical breakdown and increasing the avalanche breakdown voltage
Implementation Method 4
The blocking capability of such a power MOSFET in the upward direction is basically restricted by the avalanche effect that sets in at a high voltage due to the occurring high field strengths.
Data Source
AI summary
A vertical semiconductor component. The component includes: a drift region having a first conductivity type; a trench structure on or above the drift region, a shielding structure situated laterally next to at least one sidewall of the trench structure on or above the drift region and having a second conductivity type, and the shielding structure having at least a part of a shielding structure-trench structure such that the shielding structure has at least a first region having a first thickness and a second region having a second thickness, and an edge termination structure on or above the drift region and having the second conductivity type, and the shielding structure having a first doping degree, and the edge termination structure having a second doping degree; and at least in the second region of the shielding structure, the edge termination structure being situated between the drift region and the shielding structure.