Buried Trench Gate Electrodes for Wide SOA and Low On-Resistance
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Solution Overview
Problem
Vertical transistors face a challenge in balancing low drain resistance with a wide safe operating area (SOA) as densely arranged gates tend to narrow the SOA, making it difficult to ensure both low on-resistance and thermal stability.
Innovation Solution
The solution involves forming multiple trenches in a semiconductor substrate with a gate insulating film and a gate electrode buried within, where a first conduction type source layer and a second conduction type high concentration layer are arranged on either side of the trench, with only one lateral side of the trench facing the source layer coupled to a source electrode, allowing for a wider SOA while maintaining low drain resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gates are arranged densely to increase channel density, then channel density increases, but thermal runaway risk increases
Solution Approach 1:
Different regions of the base layer are assigned different impurity concentrations to achieve local optimization. Regions facing the gate electrode (first concentration type) have lower impurity concentration to facilitate channel formation and reduce on-resistance, enabling high channel density. Regions between adjacent first concentration type base layers (second concentration type) have higher impurity concentration to suppress parasitic bipolar transistor operation and improve thermal stability. This local quality differentiation resolves the contradiction between high channel density and thermal stability.
Data Source
AI summary
Trenches are formed in a base layer and extend parallel to each other. A gate insulating film is formed on the inner wall of each of multiple trenches. A gate electrode GE is buried in each of the trenches. The source layer is formed in the base layer to a depth less than the base layer. The source layer is disposed between each of the trenches. A second conduction type high concentration layer is formed between the source layer and the trench in a plan view. The trench, the source layer, and the second conduction type high concentration are arranged in this order repetitively in a plan view. One lateral side of the trench faces the source layer and the other lateral side of the trench faces the second conduction type high concentration layer.