Semiconductor Trench Structure with Variable Width for Voltage Stability
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Solution Overview
Problem
Semiconductor devices face instability in withstand voltage due to 'walk-out' and 'walk-in' phenomena, leading to decreased on-resistance and channel area, particularly in the outer peripheral portions of the element portion.
Innovation Solution
A semiconductor device design with a trench structure featuring a first portion with a narrower width for the gate electrode and a second portion with a wider width in the outer peripheral area, allowing for a larger depletion layer extension and increased freedom in channel region positioning to prevent voltage drops and resistance increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the channel region is formed widely to the outer peripheral portion positioned on a more outward side than a termination of a gate trench, then the withstand voltage in the outer peripheral portion is improved, but walk-out and walk-in phenomena occur causing instability in device withstand voltage characteristic
Solution Approach 1:
The patent applies local quality by forming a wider trench in the outer peripheral portion compared to the inner portion. Specifically, the trench width in the outer peripheral portion is set to be larger than in the inner portion, creating localized structural differences that suppress the walk-out and walk-in phenomena while maintaining improved withstand voltage characteristics in the outer region without causing instability.
2Reliability
If the end portion of the channel region is positioned on a more inward side than the termination of the gate trench to countermeasure against walk-out and walk-in phenomena, then the stability of withstand voltage characteristic is improved, but the channel area in the element portion is narrowed and on-resistance becomes high
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through position-dependent trench width variation. The outer peripheral portion has a wider trench that suppresses walk-out and walk-in phenomena, while the inner portion maintains appropriate dimensions to preserve channel area and low on-resistance. This localized structural differentiation allows simultaneous achievement of voltage stability and low resistance.
Solution Approach 2:
The trench structure is segmented into distinct regions: an inner portion and an outer peripheral portion, each with different width characteristics. This segmentation allows independent optimization of each region - the inner portion for low on-resistance and the outer portion for voltage stability - thereby resolving the contradiction between these two performance parameters.
3Strength
If the trench width is increased in the outer peripheral portion, then the depletion layer can extend more easily toward the end of the outer peripheral portion and withstand voltage is suppressed from decreasing, but the device complexity increases
Solution Approach 1:
The patent implements local quality by varying the trench width only in the outer peripheral portion while keeping the inner portion dimensions standard. This localized modification achieves the desired depletion layer extension and withstand voltage improvement without requiring complete redesign of the entire trench structure, thereby limiting the increase in device complexity to only the necessary peripheral regions.
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
This design effectively suppresses decreases in withstand voltage and on-resistance by expanding the depletion layer and maintaining a stable channel area, enhancing the device's voltage stability and performance.
Implementation Method 1
a gate insulating film formed at an inner surface of the trench, and a gate electrode that is embedded in the trench and that faces the first region, the second region, and the third region through the gate insulating film
Data Source
AI summary
A semiconductor device includes a semiconductor layer that has a first surface and a second surface, a trench that is formed at the first surface of the semiconductor layer and that extends in a first direction, an element portion that has a first-conductivity-type first region, a second-conductivity-type second region, and a third-conductivity-type third region that are formed in order along a depth direction of the trench from the first surface of the semiconductor layer, a gate insulating film formed at an inner surface of the trench, and a gate electrode that is embedded in the trench and that faces the first region, the second region, and the third region through the gate insulating film.