Segmented LDMOS Gate Structure for Lower Qg and TDDB

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Solution Overview

Problem

Conventional LDMOS field-effect transistors exhibit high gate charge (Qg) and are prone to hot-carrier injection (HCI) induced time-dependent dielectric breakdown (TDDB) burnout.

Innovation Solution

The proposed LDMOS architecture incorporates a gate structure with an undoped block and a doped block, where the undoped block is disposed partially on the source and wells, and the doped block is disposed partially on the second well, reducing the effective thickness of the gate oxide and thereby reducing Qg and TDDB.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If conventional LDMOS structure is used, then device can achieve high voltage operation, but gate charge is relatively high

Engineering Contradiction:

Improvegate chargeVSAvoidTDDB resistance

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The gate is segmented into two distinct blocks: an undoped block positioned over the source and first well, and a doped block positioned over the second well. This segmentation allows different regions of the gate to have different doping concentrations, enabling reduced gate charge while maintaining voltage blocking capability and reducing TDDB susceptibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the gate are assigned different doping qualities - the undoped block provides low gate charge and reduced TDDB, while the doped block maintains voltage blocking capability. This local differentiation of material properties resolves the contradiction between reducing gate charge and maintaining reliability.

Inventive Principle:

Principle #3Local quality

2Reliability

If conventional gate architecture is used, then device structure is simple, but hot-carrier injection induces TDDB burnout

Engineering Contradiction:

ImproveTDDB resistanceVSAvoidgate structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The gate is divided into undoped and doped blocks to specifically address TDDB caused by hot-carrier injection. The undoped region reduces the electric field that causes hot-carrier injection, while the doped region maintains voltage blocking. This segmentation provides TDDB protection with minimal added structural complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The undoped block is specifically positioned to protect against hot-carrier injection at the source-gate interface, while the doped block handles voltage blocking. This localized quality differentiation targets the specific TDDB mechanism without requiring complete structural redesign.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS20250040178A1Laterally-Diffused Metal-Oxide Semiconductor Devices with Reduced Gate Charge and Time-Dependent Dielectric Breakdown

Publication Date: 2025.01.30 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

An LDMOS with reduced gate charge and time-dependent dielectric breakdown is provided. An apparatus includes a substrate comprising a first well having a first doping and a second well region having a second doping, a source formed in the first well, and a gate comprising an undoped block and a doped block. The undoped block is disposed at least partially on the source, first well, and second well. The doped block is disposed at least partially on the second well.