Wide Trench Termination for Semiconductor Reverse Voltage
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Solution Overview
Problem
Semiconductor devices, such as gated diodes, face limitations in reverse voltage tolerance, leading to junction breakdown at high reverse voltages, which restricts their application.
Innovation Solution
A wide trench termination structure is introduced, featuring a wide trench with a larger width than narrow trenches, an oxide layer on the trench's inner face, a polysilicon layer on the outer face, and a metal layer on the oxide layer, along with a field oxide layer structure, to enhance reverse voltage tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional gated diode structure is used, then the device achieves good forward voltage drop and switching speed, but the reverse voltage tolerance is limited and junction breakdown occurs at high reverse voltages
Solution Approach 1:
The device is divided into distinct functional regions: a device region with narrow trenches for current conduction, and a termination region with wide trenches for voltage distribution. This segmentation allows each region to specialize in its function, preventing junction breakdown by distributing electric field stress away from the high-voltage edges.
Solution Approach 2:
The termination structure extends the voltage distribution into the vertical dimension by forming deep wide trenches filled with conductive material. This three-dimensional configuration creates multiple equipotential planes that progressively distribute the reverse voltage from the surface down into the substrate, preventing concentration of electric field at any single junction point.
2Reliability
If the trench width is increased to improve voltage distribution, then the reverse voltage tolerance improves, but the device area and manufacturing complexity increase
Solution Approach 1:
Different trench widths are implemented in different spatial locations: narrow trenches in the device region for low-loss current conduction, and wide trenches in the termination region for voltage distribution. This local differentiation optimizes each region's function without unnecessarily complicating the entire device structure.
Solution Approach 2:
The wide trench termination structure is merged with the existing narrow trench device region, sharing common fabrication processes such as photolithography patterning, etching, and conductive material filling. This integration reduces manufacturing complexity by using unified process flows rather than separate fabrication sequences.
Data Source
AI summary
A wide trench termination structure for semiconductor device includes a wide trench structure defined on a semiconductor substrate and having a width larger than that of narrow trench structures on an active region of the semiconductor device, an oxide layer arranged on an inner face of the wide trench structure, at least one trench polysilicon layer arranged on the oxide layer and on inner sidewall of the wide trench structure, a metal layer arranged on the oxide layer not covered by the trench polysilicon layer and on the trench polysilicon layer, and a field oxide layer arranged on the semiconductor substrate and outside the wide trench structure.