Trench Power Transistor Segmented Drift and Nitride Protection

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Solution Overview

Problem

Conventional trench power transistors face challenges in supporting high forward blocking voltage while maintaining low on-state resistance and minimizing gate-to-drain capacitance, which limits their high-frequency operation and switching speed.

Innovation Solution

A trench power transistor production method involving multiple insulating material layers and polycrystalline silicon structures is employed, with a nitride material used to protect oxide materials and optimize the trench electrode structure, allowing for enhanced doping concentration and reduced on-state resistance without adverse interactions that affect the gate electrode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the doping concentration in the drift region is reduced to support higher forward blocking voltage, then the voltage withstanding capability is improved, but the on-state resistance increases

Engineering Contradiction:

Improvevoltage withstanding capabilityVSAvoidon-state resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The drift region is segmented into multiple regions with different doping concentrations: a first drift region with lower doping concentration near the drain for high voltage blocking, and a second drift region with higher doping concentration near the source for low on-state resistance. This segmentation allows each region to optimize its function independently.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different doping concentrations are applied to different locations within the drift region. The first drift region has a first doping concentration optimized for voltage blocking, while the second drift region has a second doping concentration optimized for current conduction. This local quality variation resolves the contradiction between voltage withstanding and on-state resistance.

Inventive Principle:

Principle #3Local quality

2Strength

If the gate electrode volume is increased to improve voltage blocking, then the voltage withstanding capability is improved, but the gate-to-drain capacitance increases

Engineering Contradiction:

Improvevoltage blocking capabilityVSAvoidgate-to-drain capacitance

Core Design Contradiction:

StrengthVSSpeed

Solution Approach 1:

The gate electrode is extended into the drift region along the vertical dimension, forming a gate-drift region interface that increases the effective gate area for voltage blocking without significantly increasing the horizontal gate footprint. This dimensional extension reduces the gate-to-drain capacitance while maintaining voltage blocking capability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The gate electrode is nested within the trench structure, with the gate-drift region interface formed by the gate electrode extending into the drift region. This nested configuration allows the gate to interact with the drift region in a controlled manner, optimizing both voltage blocking and capacitance characteristics.

Inventive Principle:

Principle #7Nested doll (Nesting)

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 method results in a trench power transistor with improved voltage withstanding capability and reduced on-state resistance, enhancing operational efficiency and reliability by preventing unwanted charge generation and maintaining the quality of the trench electrode structure.

Implementation Method 1

a second insulating material is deposited over the first insulating material, and the second insulating material is partially removed... The first and second insulating materials are different in material, and the second insulating material is a nitride material

Methodology Applied

Scientific EffectThermal protection barrier:

Implementation Method 2

a first insulating material is deposited over the first surface and the upper surrounding and bottom walls of the upper trench portion... an oxide insulating layer

Methodology Applied

Scientific EffectElectrical insulation: Dielectric

Implementation Method 3

another polycrystalline silicon material is disposed in the upper trench portion of the electrode trench so that the another polycrystalline silicon material is surrounded by the portion of the first insulating material in the upper trench portion of the electrode trench and serves as a gate electrode

Methodology Applied

Scientific EffectField effect transistor operation:

Data Source

PatentUS11069794B2Trench power transistor and method of producing the same

Publication Date: 2021.07.20 LEADPOWER SEMI CO LTD

AI summary

A transistor production method includes etching a semiconductor substrate to form at least one upper trench portion, sequentially depositing first and second insulating materials over the substrate and partially removing the second insulating material, etching the substrate to form a lower trench portion, depositing a third insulating material over the substrate, disposing a polycrystalline silicon (pc-Si) material in the trench portions and partially removing such material, depositing a fourth insulating material over the substrate and partially removing the third and fourth insulating materials, removing the second insulating material and disposing another pc-Si material in the upper trench portion, and forming a well and a source on the substrate. A trench power transistor thus produced is also disclosed.