Superjunction Semiconductor Edge Termination with Dual RESURF Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Power semiconductor devices face a tradeoff between high breakdown voltage and low ON resistance, with the edge termination section being a critical area for ensuring sufficient breakdown voltage, as high dopant concentration in the drift region increases ON resistance and electric field concentration, leading to reliability concerns and avalanche current issues.
Innovation Solution
A semiconductor device with a superjunction structure and RESURF (REduced SURface Field) layers in the edge termination section, where p-type and n-type semiconductor pillar layers are alternately arranged, and additional n-type and p-type RESURF layers are formed to ensure balanced dopant dose and uniform electric field distribution, preventing electric field concentration and enhancing breakdown voltage reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the dopant concentration in the drift region is increased to reduce ON resistance, then the ON resistance decreases, but the breakdown voltage decreases due to electric field concentration at the pn junction interface
Solution Approach 1:
The drift region is segmented into multiple alternating p-type and n-type semiconductor layers (superjunction structure), creating multiple pn junction interfaces. This segmentation distributes the electric field across multiple interfaces rather than concentrating it at a single interface, enabling high dopant concentration in the drift region while maintaining high breakdown voltage.
Solution Approach 2:
The patent applies different dopant concentrations to different regions: high dopant concentration in the drift region for low ON resistance, and optimized dopant concentrations in the p-type and n-type semiconductor layers for electric field distribution. The RESURF layers also have specific dopant concentrations tailored to their function of reducing surface electric field concentration.
2Reliability
If the dopant concentration in the drift region is decreased to increase breakdown voltage, then the breakdown voltage increases, but the ON resistance increases due to higher drift region resistance
Solution Approach 1:
The superjunction structure segments the drift region into alternating p-type and n-type layers, allowing the overall drift region to have high average dopant concentration (low resistance) while the local depletion regions at multiple pn interfaces distribute the electric field (high breakdown voltage).
Solution Approach 2:
The drift region uses a composite structure of alternating p-type and n-type semiconductor layers with different dopant concentrations, combining the benefits of high conductivity (from high overall dopant concentration) and high breakdown voltage (from distributed electric field at interfaces).
3Reliability
If a single RESURF layer is used in the edge termination section, then the electric field is reduced at that interface, but avalanche current concentration and reliability issues persist due to insufficient depletion layer extension
Solution Approach 1:
The single RESURF layer is segmented into a first RESURF layer and a second RESURF layer with opposite conductivity types arranged in sequence. This creates multiple pn junction interfaces that distribute and reduce electric field concentration, preventing avalanche current concentration and enhancing reliability.
Solution Approach 2:
Instead of using a single RESURF layer of one conductivity type, the patent uses two RESURF layers with opposite conductivity types (first and second conductivity types), inverting the approach to create additional pn interfaces that enhance electric field distribution and depletion layer extension.
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 increases the breakdown voltage and reduces ON resistance by ensuring sufficient depletion layer extension in the edge termination section, preventing avalanche breakdown and enhancing the reliability of the semiconductor device despite variations in dopant dose ratios.
Implementation Method 1
a depletion layer extends from the pn junction interface between the p-type base region and the n-type drift region (first pn junction interface) into the drift region and serves to sustain the voltage
Implementation Method 2
electric field strength in the semiconductor device is maximized at the first pn junction interface
Implementation Method 3
it also raises concerns about the decrease of reliability of the semiconductor device. Moreover, avalanche current concentrating on the edge termination section also causes the breakdown of the semiconductor device
Data Source
AI summary
A semiconductor device includes: a drift layer having a superjunction structure; a semiconductor base layer selectively formed in a part of one surface of the drift layer; a first RESURF layer formed around a region having the semiconductor base layer formed thereon; a second semiconductor RESURF layer of a conductivity type which is opposite to a conductivity type of the first semiconductor RESURF layer; a first main electrode connected to a first surface of the drift layer; and a second main electrode connected to a second surface of the drift layer. The first RESURF layer is connected to the semiconductor base layer. The second semiconductor RESURF layer is in contact with the first semiconductor RESURF layer.