Shield-Gate Bidirectional Power Structure for Low On-Resistance
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Solution Overview
Problem
Bidirectional power devices face a trade-off between voltage withstand property and on-resistance, where improving breakdown voltage increases on-resistance and power consumption.
Innovation Solution
A bidirectional power device design featuring a control gate at the lower portion of trenches, a shield gate at the upper portion isolated by an isolation layer, and a shield dielectric layer to manage voltage withstand and on-resistance, with the shield gate isolated from the semiconductor layer to enhance voltage withstand and provide a low-impedance conduction path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the impurity concentration of the lightly-doped N- region is reduced to improve breakdown voltage, then voltage withstand property is improved, but on-resistance increases and power consumption increases
Solution Approach 1:
The device is segmented into multiple regions with different doping concentrations: a lightly-doped N- region for high breakdown voltage and heavily-doped N+ regions for low on-resistance. This segmentation allows each region to optimize its function independently, resolving the contradiction between voltage withstand and power consumption.
Solution Approach 2:
Different regions of the device have different local qualities in terms of doping concentration. The N- region has low impurity concentration for high voltage withstand, while the N+ regions have high impurity concentration for low resistance conduction. This local differentiation resolves the global contradiction by optimizing each location for its specific function.
2Strength
If the impurity concentration of the lightly-doped N- region is reduced to improve breakdown voltage, then voltage withstand property is improved, but on-resistance increases
Solution Approach 1:
The device structure is divided into voltage-withstand regions (lightly-doped N-) and conduction regions (heavily-doped N+). This segmentation allows the voltage withstand regions to optimize for breakdown voltage while conduction regions optimize for low on-resistance, resolving the contradiction between these two parameters.
Solution Approach 2:
Each region is assigned a specific doping concentration appropriate for its function: low doping in N- regions for high voltage withstand and high doping in N+ regions for low on-resistance. This local quality differentiation simultaneously achieves both high voltage withstand property and low on-resistance.
Data Source
AI summary
Disclosed are a bidirectional power device and a method for manufacturing the same. The bidirectional power device includes a semiconductor layer, a plurality of trenches located in the semiconductor layer, a gate dielectric layer located on an inner wall of each of the plurality of trenches, a control gate located at a lower portion of each of the plurality of trenches, a shield gate located at an upper portion of each of the plurality of trenches and an isolation layer located between the control gate and the shield gate. When the bidirectional power device is turned off, charges of a source region and a drain region are depleted by the shield gate through a shield dielectric layer, thereby improving voltage withstand property. When the bidirectional power device is turned on, the source region and/or the drain region and the semiconductor layer provide a low-impedance conduction path.