LDMOS Ring Field Plate for On-Resistance and Breakdown Voltage

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Solution Overview

Problem

Current semiconductor devices face challenges in achieving low on-resistance while maintaining high breakdown voltage, which is essential for high-voltage applications and energy efficiency.

Innovation Solution

A lateral diffused MOS transistor (LDMOS) is designed with a ring-shaped field plate that surrounds the source and drain regions, comprising a conductive layer with a dielectric layer under portions of the field plate to smooth the electrical field and reduce breakdown voltage, thereby achieving low on-resistance and high breakdown voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional LDMOS structure is used, then high breakdown voltage is achieved, but on-resistance remains high

Engineering Contradiction:

Improvebreakdown voltageVSAvoidon-resistance

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The field plate structure is segmented into a conventional linear portion and an added ring-shaped portion, allowing different regions to serve different functions: the linear portion maintains high breakdown voltage while the ring portion reduces on-resistance by smoothing the electrical field in the drift region

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The ring-shaped field plate is positioned to surround the source and drain regions, creating localized field smoothing in specific areas of the drift region where it most effectively reduces on-resistance, while maintaining high breakdown voltage in other regions

Inventive Principle:

Principle #3Local quality

2Loss of energy

If the electrical field in the drift region is smoothed to reduce on-resistance, then energy loss decreases, but breakdown voltage may be compromised

Engineering Contradiction:

Improveon-resistanceVSAvoidbreakdown voltage

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The field plate is divided into functional segments: the ring-shaped portion smooths the electrical field to reduce on-resistance, while the linear portion extending from the gate maintains the high breakdown voltage characteristic, allowing both objectives to be achieved simultaneously

Inventive Principle:

Principle #1Segmentation

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 LDMOS device exhibits reduced energy consumption and increased design tolerance due to its low on-resistance characteristics and ability to withstand sufficient high breakdown voltage, making it suitable for high-voltage applications.

Implementation Method 1

A first portion of the ring-shaped field plate on an isolation can make a drift region of the LDMOS more smooth to reduce or suspend break down

Methodology Applied

Scientific EffectElectrical field smoothing: Electric Field

Implementation Method 2

Due to having a dielectric layer under a second portion of a ring-shaped field plate neighboring a gate structure, the LDMOS can be applied with sufficient high break-down voltage

Methodology Applied

Scientific EffectDielectric isolation: Dielectric

Data Source

PatentUS9859399B2Lateral diffused semiconductor device with ring field plate

Publication Date: 2018.01.02 VANGUARD INTERNATIONAL SEMICONDUCTOR CORPORATION

AI summary

A lateral diffused semiconductor device is disclosed, including: a substrate; a first isolation and a second isolation comprising at least portions disposed in the substrate to define an active area; a first drift region and a second drift region disposed in the active area, wherein the first drift region is disposed in the second drift region; a gate structure on the substrate; a source region in the first drift region; a drain region in the second drift region; and a ring-shaped field plate on the substrate, wherein the ring-shaped field plate surrounds at least one of the source and the drain region.