Super Junction MOSFET Edge Termination for Stable Reverse Recovery
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Solution Overview
Problem
Super junction MOSFET devices face breakdown issues due to unsecured hole current paths during reverse recovery, leading to reliability concerns and increased leakage currents when applying reverse bias, which affects the robustness and ruggedness of the device.
Innovation Solution
The solution involves creating a super junction semiconductor device with charge sharing regions in the peripheral and edge termination regions, optimizing the area and depth of these regions to secure a stable hole current path and di/dt value by forming alternating conductivity type pillars and charge sharing regions, and implementing specific manufacturing processes to enhance breakdown voltage and reverse recovery current characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If Schottky diode is implemented to reduce hole carriers, then hole current concentration is reduced, but leakage current increases and device characteristics are affected
Solution Approach 1:
A peripheral region is introduced as an intermediary structure between the active cell and edge termination region. This peripheral region includes peripheral charge sharing regions that facilitate hole current distribution without requiring additional Schottky diodes or irradiation processes, thereby avoiding increased leakage current while still preventing hole current concentration.
Solution Approach 2:
The patent modifies the structural parameters by forming peripheral charge sharing regions with specific doping concentrations and geometries. By changing the physical structure and electrical parameters of the peripheral region, the hole current path is optimized to prevent concentration at corner regions without affecting overall device characteristics.
2Object-affected harmful factors
If helium irradiation or electron beam irradiation is performed to reduce hole carrier lifetime, then hole current concentration is reduced, but process cost increases and device characteristics are affected
Solution Approach 1:
The patent extracts the hole current management function from complex irradiation processes and implements it through a dedicated peripheral region structure. By taking out the charge sharing function and implementing it through conventional semiconductor fabrication processes, the need for expensive helium or electron beam irradiation is eliminated.
Solution Approach 2:
The peripheral region with charge sharing regions serves as a cost-effective structure that achieves hole current management without requiring expensive irradiation processes. This structural solution replaces costly process steps with a design that uses standard fabrication techniques.
3Reliability
If charge sharing regions are optimized to secure hole current path, then reverse recovery characteristics are improved, but device structure becomes more complex
Solution Approach 1:
The device is segmented into distinct functional regions: active cell, peripheral region with charge sharing regions, and edge termination region. This segmentation allows the peripheral region to specifically handle hole current management while keeping the active cell optimized for main device function, achieving improved reverse recovery characteristics through regional specialization.
Solution Approach 2:
The peripheral region serves multiple functions: it acts as a transition zone between active cell and edge termination, provides charge sharing to manage hole current, and prevents corner region breakdown. By making the peripheral region multi-functional, the overall device structure remains compact without requiring additional separate components.
Data Source
AI summary
A super junction semiconductor device includes a substrate, an active cell disposed on the substrate, an edge termination region surrounding the active cell, a peripheral region formed between the active cell and the edge termination region, a plurality of first conductivity type pillars and second conductivity type pillars alternately provided at an edge of the active cell and the peripheral region and the edge termination region, and a charge sharing region connecting the second conductivity type pillars in the peripheral region with the second conductivity type pillars in the edge termination region above the peripheral region and the edge termination region.