Segmented Trench Gate Layout for Gate Oxide Field Protection

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Solution Overview

Problem

Trench power semiconductor devices face challenges in protecting the bottom of the trench from peak electrical fields, which limits the scaling of pitch and obtainable drain-to-source resistance, while maintaining high channel density and reliable gate insulation.

Innovation Solution

A power semiconductor device design featuring a semiconductor body with a trench subdivided into segments, where a doped region of opposite conductivity type extends between segments, providing additional protection to the trench bottom and allowing for reduced pitch without the need for additional shielding regions, thereby enhancing channel density and gate insulation reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a p+-region is provided to protect the gate oxide on the bottom of the trench, then the gate oxide is protected from peak electrical field, but the pitch between adjacent trenches cannot be scaled down and the drain to source resistance increases

Engineering Contradiction:

Improvegate oxide protectionVSAvoidpitch between trenches

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The trench is divided into multiple segments along its main extension direction, creating discrete trench sections separated by regions where the doped region extends deeper. This segmentation allows the protective doped region to be positioned between segments rather than requiring continuous lateral protection, enabling pitch reduction while maintaining gate oxide protection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The protection mechanism transitions from lateral protection (p+-region on the side of the trench) to vertical protection (doped region extending deeper between segments). By utilizing the vertical dimension more effectively, the invention achieves protection without consuming lateral space, thus enabling narrower pitch between trenches.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Loss of energy

If the pitch between adjacent trenches is decreased to increase channel density, then on-state losses are reduced, but the gate oxide becomes more vulnerable to peak electrical field

Engineering Contradiction:

Improveon-state lossesVSAvoidgate oxide protection

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

Dividing the trench into segments creates natural protection zones between segments where the doped region extends deeper, providing electrical field management without requiring increased pitch. This allows narrow pitch for high channel density while maintaining gate oxide protection through the segmented structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The doped region is selectively positioned between adjacent trench segments with higher doping concentration in specific subregions, creating localized protection zones exactly where the gate oxide is most vulnerable to peak electrical field, while maintaining narrow overall pitch.

Inventive Principle:

Principle #3Local quality

3Reliability

If a p+-region is provided on the side of the trench for protection, then the gate oxide is protected, but the device complexity and manufacturing complexity increase

Engineering Contradiction:

Improvetrench protectionVSAvoidtrench structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protective function is merged with the existing doped region structure by extending it vertically between trench segments, rather than adding a separate lateral p+-region. This integration reduces device complexity while achieving the same protection function.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The doped region serves multiple functions: it provides the necessary electrical field management for protection, acts as a structural element defining the segmented trench configuration, and enables pitch reduction. This multi-functionality reduces overall device complexity compared to dedicated lateral protection structures.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 design effectively shields the trench bottom from electrical fields, enabling a higher channel density and improved reliability of the gate insulation layer while maintaining low on-state losses, thus optimizing the device's performance for high electrical currents and voltages.

Implementation Method 1

the doped region is arranged in regions in the vertical direction between the source region and the drift layer... Between the two adjacent segments the doped region extends deeper into the semiconductor body in the vertical direction than the trench

Methodology Applied

Scientific EffectElectrical field effect: Electric Field

Data Source

PatentUS20240021670A1Power semiconductor device with an insulated trench gate electrode

Publication Date: 2024.01.18 HITACHI ENERGY LTD

AI summary

A power semiconductor device (1) comprising a semiconductor body (2) extending in a vertical direction between a first main surface (21) and a second main surface (22), a trench (4) extending from the first main surface (21) into the semiconductor body (2) in the vertical direction, and an insulated trench gate electrode (3) that is formed on the first main surface (21) and extends into the trench (4) is specified, wherein the trench (4) is subdivided along a main extension direction of the trench (4) in a plurality of segments (41) and the insulated trench gate electrode (3) continuously extends over the plurality of segments (41).