Trench-Gate LDMOS Structure for Low On-Resistance and Breakdown Voltage
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Solution Overview
Problem
Lateral double-diffused metal oxide semiconductor field effect transistors (LDMOS) face a contradiction between achieving low on-resistance and high breakdown voltage due to the limitations of material doping concentrations, necessitating a balance between these two critical parameters in device design.
Innovation Solution
The LDMOS design incorporates a trench gate extending into the bulk region and an insulation structure within the drift region, forming a three-dimensional current path that increases current density while maintaining sufficient voltage resistance, thereby reducing on-resistance without compromising breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a drift region with low doping concentration is used to increase breakdown voltage, then breakdown voltage is improved, but on-resistance increases
Solution Approach 1:
The patent introduces a three-dimensional current path by extending the trench gate into the bulk region and adding an insulation structure within the drift region. This transforms the conventional two-dimensional current flow into a 3D path, allowing current to flow through multiple regions including the drift region, thereby increasing current density without requiring higher doping concentrations that would compromise breakdown voltage
Solution Approach 2:
The device is segmented into multiple functional regions: source region, drain region, drift region, and bulk region, each with specific doping concentrations and geometries. The trench gate is segmented into a lower part inside the trench and an upper part outside the trench. This segmentation allows optimization of each region's properties to simultaneously achieve high breakdown voltage and low on-resistance
Data Source
AI summary
A lateral double-diffused metal oxide semiconductor field effect transistor (LDMOS), including: a trench gate including a lower part inside a trench and an upper part outside the trench, a length of the lower part in a width direction of a conducting channel being less than that of the upper part, and the lower part extending into a body region and having a depth less than that of the body region; an insulation structure arranged between a drain region and the trench gate and extending downwards into a drift region, a depth of the insulation structure being less than that of the drift region.