Vertical MOSFET Trench Layout for Lower On-Resistance
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Solution Overview
Problem
In in-trench double gate type power MOSFETs, supplying source potential to the field plate electrode increases on-resistance, compromising switching loss reduction and surge voltage reduction benefits compared to supplying gate potential.
Innovation Solution
The semiconductor device alternately arranges trenches with a gate electrode and a field plate electrode at a gate potential and another trench with a gate electrode and a field plate electrode at a source potential, allowing for reduced on-resistance while maintaining switching loss reduction and false-on margin expansion advantages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If source potential is supplied to the field plate electrode, then switching loss is reduced and surge voltage is reduced, but on-resistance increases
Solution Approach 1:
The patent applies different potentials to different field plate electrodes based on their local position and function. Specifically, field plate electrodes in odd-numbered trenches are supplied with source potential to reduce switching loss and surge voltage, while field plate electrodes in even-numbered trenches are supplied with gate potential to maintain low on-resistance. This local differentiation resolves the contradiction by optimizing each region for its specific function.
2Reliability
If all field plate electrodes are supplied with gate potential, then on-resistance is reduced, but switching loss and surge voltage increase
Solution Approach 1:
Rather than uniformly supplying gate potential to all field plate electrodes, the patent implements a differentiated approach where odd-numbered field plate electrodes receive source potential to reduce switching loss and even-numbered ones receive gate potential to maintain low on-resistance. This resolves the contradiction by distributing different functions to different locations.
3Reliability
If alternating trenches with different field plate potentials are arranged, then on-resistance is reduced while maintaining switching loss reduction benefits, but device structure becomes more complex
Solution Approach 1:
The patent segments the field plate electrodes into two groups based on their trench position (odd-numbered and even-numbered trenches). Each segment is supplied with a different potential (source potential for odd-numbered, gate potential for even-numbered) through separate connection structures. This segmentation allows the device to achieve low on-resistance while maintaining switching loss reduction benefits, with the added advantage that the segmented structure can be implemented using existing trench formation processes.
Data Source
AI summary
A semiconductor device includes a vertical MOSFET in which a trench including a gate electrode and a field plate electrode therebelow at a gate potential and a trench including a gate electrode and a field plate electrode therebelow at a source potential are alternately arranged on an upper surface of a semiconductor substrate in a plan view.