Semiconductor Edge Termination Surface Doping for Field Relaxation
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Solution Overview
Problem
Semiconductor devices with needle trench designs face challenges in maintaining low on-state resistance and preventing electrical breakdowns due to high electric fields at the outer rim of the semiconductor substrate, particularly caused by crystal defects and increased electrical fields.
Innovation Solution
A semiconductor device with a surface doping region in the edge termination area having a net doping concentration lower than the upper drift region, combined with spicular trenches and a specific trench design, helps in reducing the electric field strength and improving blocking capabilities by laterally relaxing the electrostatic potential distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a needle trench design with deep spicular trenches is used to reduce on-state resistance, then the cross-sectional area for the mesa region is increased, but the electric field strength at the outer rim increases causing avalanche breakdown
Solution Approach 1:
The patent applies local quality by creating a surface doping region with reduced net doping concentration specifically in the edge termination area, while maintaining the original doping concentration in the upper drift region. This localized modification of doping concentration allows the device to maintain low on-state resistance in the active area while improving blocking capability at the edge termination area where high electric fields occur.
Solution Approach 2:
The patent changes the doping concentration parameter in the edge termination area by introducing a surface doping region with lower net doping concentration. This parameter change modifies the electrostatic potential distribution and reduces the electric field strength at the outer rim, thereby preventing avalanche breakdown while maintaining the overall device performance.
2Reliability
If the net doping concentration in the upper drift region is reduced to prevent breakdown, then the blocking capability is improved, but the on-state resistance increases
Solution Approach 1:
The invention applies local quality by restricting the reduced doping concentration modification to only the edge termination area through the surface doping region, while keeping the upper drift region's doping concentration unchanged. This allows the active area to maintain low on-state resistance while the edge termination area achieves improved blocking capability.
Solution Approach 2:
The drift region is segmented into an upper drift region and a lower drift region, with the surface doping region creating a distinct transition zone. This segmentation allows independent optimization of different areas: the upper drift region maintains high conductivity for low on-state resistance, while the surface doping region provides field relaxation for improved blocking capability.
3Power
If deep spicular trenches are formed to increase mesa area, then the on-state resistance is reduced, but crystal defects at the outer rim cause localized breakdown
Solution Approach 1:
The surface doping region acts as a beforehand cushioning measure by pre-modifying the doping concentration in the edge termination area to reduce electric field strength. This preparatory modification cushions against the harmful effects of crystal defects and high electric fields that would otherwise cause breakdown at the outer rim.
Solution Approach 2:
The invention converts the harmful high electric field concentration at the edge termination into a beneficial distributed field pattern. By reducing the net doping concentration in the surface doping region, the originally harmful high electric field is transformed into a relaxed electrostatic potential distribution that prevents breakdown.
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 effectively reduces the risk of avalanche breakdowns and enhances the blocking capabilities of the semiconductor device by spreading the electrostatic potential and reducing electric field strength at the outer spicular trench, thereby improving the breakdown voltage and stability.
Implementation Method 1
The edge termination area includes a surface doping region arranged in the upper drift region in the edge termination area and extending to the first side, wherein the surface doping region is spaced apart from the lower end of the upper drift region and has a net doping concentration lower than a net doping concentration of the upper drift region
Data Source
AI summary
A semiconductor device includes a semiconductor substrate having drift and body regions. The drift region includes upper and lower drift regions. An active area includes a plurality of spicular trenches extending through the body region and into the drift region. Each spicular trench in the active area has a lower end which together define a lower end of the upper drift region extending towards a first side and a lower drift region extending from the lower end of the upper drift region towards a second side. The edge termination area includes spicular termination trenches extending at least into the upper drift region. A surface doping region arranged in the upper drift region in the edge termination area extends to the first side, is spaced apart from the lower end of the upper drift region, and has a net doping concentration lower than that of the upper drift region.