Trench Semiconductor Structure for Low On-Resistance and High Breakdown
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Solution Overview
Problem
There is a trade-off relationship between on-resistance and breakdown voltage in semiconductor devices with p-type and n-type layers, where improving one characteristic often deteriorates the other.
Innovation Solution
The semiconductor device incorporates a trench structure with a gate insulating film and a gate electrode, along with p-type deep layers, n-type deep layers, and an n-type high concentration layer. The n-type high concentration layer is in contact with the lower surface of the p-type deep layers, restricting the spread of depletion layers and securing a wide current path, thereby achieving low on-resistance and high breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If p-type and n-type layers are repeatedly arranged to reduce on-resistance, then on-resistance decreases, but breakdown voltage deteriorates
Solution Approach 1:
The device segments the current path into multiple parallel channels by arranging multiple p-type deep layers and n-type deep layers alternately. This segmentation allows the current to flow through multiple paths, reducing the overall on-resistance while maintaining adequate breakdown voltage through the alternating structure that prevents depletion layer merger.
Solution Approach 2:
The patent applies local quality by creating regions with different impurity concentrations and types. The p-type deep layers have high p-type impurity concentration, while the n-type deep layers have high n-type impurity concentration, and the drift layer has lower n-type impurity concentration. This local differentiation optimizes both conduction in the on-state and depletion characteristics in the off-state, resolving the trade-off between on-resistance and breakdown voltage.
2Loss of energy
If deep layers are added to reduce on-resistance, then on-resistance decreases, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into the deep layer structure. The alternating p-type and n-type deep layers simultaneously serve as conduction paths for reducing on-resistance and as depletion regions for maintaining breakdown voltage. This merging of functions reduces the need for separate structural elements, thereby limiting the increase in device complexity while achieving low on-resistance.
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 semiconductor device achieves both low on-resistance and high breakdown voltage by restricting the spread of depletion layers through the n-type high concentration layer, effectively addressing the trade-off relationship between these characteristics.
Implementation Method 1
an n-type high concentration layer being in contact with at least a part of a lower surface of a corresponding p-type deep layer in the plurality of p-type deep layers and having a higher concentration of n-type impurities than the drift layer
Implementation Method 2
a gate insulating film covering an inner surface of the trench, and a gate electrode located in the trench and insulated from the semiconductor substrate by the gate insulating film
Data Source
AI summary
A semiconductor device includes a plurality of p-type deep layers, a plurality of n-type deep layers, a drift layer of n-type, and an n-type high concentration layer. The n-type high concentration layer is in contact with at least a part of a lower surface of a corresponding p-type deep layer in the plurality of p-type deep layers and has a higher concentration of n-type impurities than the drift layer.