Superjunction Terminal Structure With Trench Rings and Field Plates
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Solution Overview
Problem
Conventional terminal structures for superjunction semiconductor devices are inadequate in withstanding lateral voltage, differing from conventional VDMOS and diodes, necessitating a new design to enhance voltage withstanding performance and reliability.
Innovation Solution
A terminal structure for superjunction devices is developed, featuring trench stripes and rings, second-type wells, source regions, gate and drain electrodes, and field plates, with specific dielectric film thicknesses and materials, arranged around the periphery to improve voltage withstanding and reliability without complex new processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional terminal structures (guarding ring, field plate, junction terminal extension) are used for superjunction devices, then manufacturing processes remain simple, but voltage withstanding performance is insufficient due to the different lateral voltage withstanding mechanism in superjunction devices
Solution Approach 1:
The terminal structure is segmented into multiple functional components: second type trench stripes for voltage withstanding, first type trench stripes for charge balancing, and field plates for electric field control. Each segment performs a specific function to collectively achieve superior voltage withstanding performance while maintaining manufacturability through standard semiconductor processes
Solution Approach 2:
Different regions of the terminal structure have different doping types and configurations optimized for local requirements. The second type trench stripes are positioned where voltage withstanding is critical, while first type trench stripes are placed where charge balancing is needed, creating local quality variations that enhance overall device performance
2Strength
If higher impurity concentration is used in P-type and N-type doping regions to achieve high breakdown voltage, then breakdown voltage increases, but on-resistance also increases which limits device performance
Solution Approach 1:
The device is divided into active area with alternating P-N type thin layers for high breakdown voltage and terminal structure with optimized doping for low on-resistance. This segmentation allows each region to be independently optimized for its specific function, achieving both high breakdown voltage and low on-resistance simultaneously
Solution Approach 2:
The patent uses different doping concentrations in different regions: higher impurity concentration in the active area P-type and N-type regions to achieve high breakdown voltage, while optimizing terminal structure doping to minimize on-resistance. The alternating P-N type thin layers with controlled thickness and doping parameters enable simultaneous optimization of both breakdown voltage and on-resistance
3Reliability
If a terminal structure is designed to withstand the huge voltage difference between border cells and substrate in horizontal direction, then voltage withstanding improves, but device complexity increases
Solution Approach 1:
The terminal structure serves multiple functions simultaneously: second type trench stripes withstand lateral voltage, first type trench stripes balance charges, and field plates control electric fields. This multi-functionality approach achieves comprehensive voltage withstanding performance without requiring separate structures for each function, thereby limiting the increase in device complexity
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 terminal structure effectively enhances voltage withstanding performance and reliability of superjunction devices by balancing charge and electric fields, achieving high breakdown voltage without introducing new complex manufacturing processes.
Implementation Method 1
a second type impurity is filled into the trench stripes to form second type trench stripes; each second type well surrounding a second type trench stripe
Implementation Method 2
both P-type and N-type regions can be fully depleted at a relative low voltage in an off-state, thereby exhibiting a high breakdown voltage
Implementation Method 3
a plurality of trench stripes are formed in the first type epitaxial layer in the active area; a second type impurity is filled into the trench stripes
Implementation Method 4
a first type epitaxial layer formed on the first type substrate; both P-type and N-type regions can be fully depleted
Data Source
AI summary
A terminal structure for superjunction device is disclosed. The terminal structure comprises from inside out at least one P type implantation ring and several P type trench rings formed in an N type epitaxial layer to form alternating P type and N type regions. A channel cut-off ring is formed at the border of the device. The P type implantation ring is formed adjacent to the active area of the device and covers at least one trench ring. A terminal dielectric layer is formed to cover the P type implantation ring and the trench rings. A plurality of field plates are formed above the terminal dielectric layer. Methods of manufacturing terminal structure are also disclosed.