GaN Trench Gate MISFET Sidewall Geometry for Low On-Resistance
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Solution Overview
Problem
In trench type vertical MISFETs, it is challenging to cover the corner portion of the trench with the gate electrode without increasing on-resistance, as existing methods like forming a V-shaped trench cross-section lead to increased channel length and resistance.
Innovation Solution
A semiconductor device with a trench gate structure where the side surface of the trench has a specific angled configuration, with a perpendicular region and an inclined region, allowing for improved gate electrode coverage without increasing on-resistance, achieved through dry-etching and ion implantation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the cross section of the trench is made into a V-shape to improve gate electrode coverage, then the coverage of the gate electrode is improved, but the channel length increases and on-resistance deteriorates
Solution Approach 1:
The trench side surface is segmented into two distinct regions: a first region with a first inclination angle and a second region with a second inclination angle. This segmentation allows each region to serve different functions - the first region provides adequate gate electrode coverage while the second region maintains the channel length and prevents on-resistance increase.
Solution Approach 2:
Different portions of the trench side surface are given different local qualities through varying inclination angles. The first region has a specific inclination angle optimized for gate electrode coverage, while the second region has a different inclination angle optimized for maintaining channel characteristics and minimizing resistance.
2Reliability
If the channel length is reduced to lower on-resistance, then the on-resistance decreases, but the gate electrode coverage becomes insufficient
Solution Approach 1:
Instead of simply reducing the channel length in one dimension, the invention introduces a dimensional change by creating an inclined region. This inclined region allows the gate electrode to extend further along the trench side surface without increasing the effective channel length, thus improving coverage while maintaining 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
This configuration enhances the coverage of the gate electrode, reducing resistance and improving the stability of the device operation by maintaining the channel length and minimizing thermal damage.
Implementation Method 1
achieved through dry-etching and ion implantation processes
Implementation Method 2
achieved through dry-etching and ion implantation processes
Data Source
AI summary
A semiconductor device of trench gate type is formed of a group III nitride semiconductor. The semiconductor device has a substrate, a first layer, a second layer, and a third layer accumulated in this order, and further has a trench penetrating through the third layer and the second layer and reaching the first layer. A side surface of the trench, exposed to the second layer, is perpendicular to a main surface of the substrate. A side surface of the trench, exposed to the third layer, includes a first region which is perpendicular to the main surface of the substrate, and a second region above the first region, which is inclined with respect to the main surface of the substrate. A cross-sectional area of the trench at the second region in a plane parallel to a bottom surface of the trench increases from a bottom toward an upper of the trench.