Trench Gate Runner and Floating-Field Implant for MOSFET Termination

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Solution Overview

Problem

Existing transistor devices face limitations in achieving higher current ratings due to breakdown voltage constraints, particularly in the edge termination region, where known termination structures occupy significant device area, are costly, and cause mechanical stress.

Innovation Solution

The integration of trench metal-oxide-semiconductor field effect transistors (MOSFET) devices with a gate-runner trench and a floating-field implant within an epitaxial layer, which reduces electric field crowding and increases breakdown voltage by expanding the depletion region, while being cost-effective and minimizing mechanical stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If known termination structures are used to mitigate electric field concentration, then breakdown voltage is improved, but device area occupied increases significantly

Engineering Contradiction:

Improvebreakdown voltageVSAvoiddevice area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent transitions from planar termination structures to a three-dimensional trench-based structure. The gate runner is formed within a trench that extends vertically into the semiconductor substrate, utilizing the depth dimension to achieve field termination. This vertical configuration allows the termination structure to occupy minimal surface area while effectively managing electric fields through the third dimension, thereby resolving the contradiction between breakdown voltage improvement and device area occupation.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The gate runner trench is nested within the semiconductor device structure, with the trench containing the gate runner material that extends from the surface downward. The floating-field implant region is nested around the trench structure. This nested configuration allows multiple functional regions to occupy overlapping spatial volumes, maximizing the use of available space and achieving effective field termination without proportionally increasing the device footprint.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Reliability

If known termination structures are used to mitigate electric field concentration, then breakdown voltage is improved, but manufacturing cost increases

Engineering Contradiction:

Improvebreakdown voltageVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The gate runner trench serves multiple functions simultaneously: it provides electric field termination, acts as a structural support element, defines the gate region, and serves as a template for subsequent material deposition. The floating-field implant region also performs dual functions of field termination and electrical isolation. This multi-functionality reduces the need for separate dedicated termination structures and additional processing steps, thereby lowering manufacturing complexity and cost while achieving the required breakdown voltage.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If known termination structures are used to mitigate electric field concentration, then breakdown voltage is improved, but mechanical stress within the device increases

Engineering Contradiction:

Improvebreakdown voltageVSAvoidmechanical stress

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent introduces a floating-field implant region with specific electrical properties localized around the gate runner trench. This region has a different doping concentration and type compared to the surrounding bulk material, creating a localized electrical environment that terminates electric fields. By confining the field termination function to this specific localized region rather than using extensive bulk termination structures, mechanical stress is concentrated in a small, controlled volume rather than being distributed throughout the entire device, thereby reducing overall mechanical stress while maintaining breakdown voltage.

Inventive Principle:

Principle #3Local quality

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 solution enhances breakdown voltage, reduces mechanical stress, and optimizes device performance by integrating a trenched gate runner and floating-field implant, allowing for higher voltage operation with reduced sensitivity to surface charge variations.

Implementation Method 1

increases breakdown voltage by expanding the depletion region

Methodology Applied

Scientific EffectDepletion region expansion: Electric Field

Data Source

PatentUS8872278B2Integrated gate runner and field implant termination for trench devices

Publication Date: 2014.10.28 SEMICON COMPONENTS IND LLC

AI summary

In one general aspect, an apparatus can include a plurality of trench metal-oxide-semiconductor field effect transistors (MOSFET) devices formed within an epitaxial layer of a substrate, and a gate-runner trench disposed around the plurality of trench MOSFET devices and disposed within the epitaxial layer. The apparatus can also include a floating-field implant defined by a well implant and disposed around the gate-runner trench.