Semiconductor Device Floating Layer Control Gate

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Solution Overview

Problem

Existing semiconductor devices with insulated gate bipolar transistors (IGBTs) face increased switching loss during turn-off as carrier accumulation increases, despite enhanced injection enhancement (IE) effects.

Innovation Solution

The semiconductor device incorporates a floating layer of a first conductivity type surrounded by trench electrodes, a floating layer control gate of a second conductivity type, and a floating layer control gate disposed above the floating separation layer, which allows for improved IE effects and reduced switching loss by controlling carrier discharge paths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the carrier accumulation quantity is increased to enhance the IE effect, then the IE effect is improved, but the switching loss (Eoff) at turn-off increases

Engineering Contradiction:

ImproveIE effectVSAvoidswitching loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The device is divided into active cell regions and inactive cell regions that are alternately arranged. The inactive cell regions contain floating layers that serve as carrier storage regions, separating the carrier accumulation function from the active switching regions. This segmentation allows carrier accumulation to be concentrated in specific floating layers while keeping the active regions optimized for switching performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Floating layers are introduced as intermediary structures between the active cells and the collector. These floating layers act as mediator regions that accumulate carriers during conduction and can be controlled to discharge carriers during turn-off, thereby mediating between the need for carrier accumulation (IE effect) and the need for rapid carrier removal (switching performance).

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If floating layers are provided to increase carrier concentration in the drift layer, then the IE effect is enhanced, but the turn-off switching loss increases

Engineering Contradiction:

Improvecarrier concentrationVSAvoidswitching loss

Core Design Contradiction:

Quantity of substanceVSLoss of energy

Solution Approach 1:

The floating layers are designed to dynamically change their electrical characteristics based on operating conditions. During conduction, the floating layers are depleted and store carriers. During turn-off, the floating layers can be biased to rapidly discharge accumulated carriers. This dynamic behavior allows the same structure to support both high carrier concentration during on-state and rapid carrier removal during off-state.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The floating layers undergo periodic charging and discharging cycles synchronized with the IGBT switching operations. During the on-period, carriers are accumulated in the floating layers; during the off-period, the floating layers discharge carriers. This periodic action pattern allows the system to alternately achieve high carrier concentration and rapid carrier removal without conflict.

Inventive Principle:

Principle #19Periodic action

3Reliability

If active cells and inactive cells are alternately arranged to reduce carrier discharge path, then the IE effect is improved, but the device complexity increases

Engineering Contradiction:

ImproveIE effectVSAvoidcell structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The floating layers in the inactive cell regions serve multiple functions simultaneously: they act as carrier storage regions, they define the boundaries between active cells, and they provide a controlled discharge path for carriers. This multi-functionality reduces the need for additional separate structures, thereby limiting the increase in device complexity while achieving the desired IE effect enhancement.

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 configuration enhances the IE effect while reducing switching loss during turn-off by effectively managing carrier discharge, leading to increased turn-off speed and improved reliability.

Implementation Method 1

the IE-type IGBT utilizing IE (Injection Enhancement) effect has been developed with the purpose of reducing the conduction resistance and on-voltage in the on-state of the trench gate type IGBT. By providing the floating layer, holes are less likely to be discharged from the emitter electrodes when IGBT is in the on-state, and the concentration of carriers (holes) accumulated in the drift layer can be increased.

Methodology Applied

Scientific EffectInjection Enhancement (IE) effect:

Data Source

PatentUS11444186B2Semiconductor device

Publication Date: 2022.09.13 RENESAS ELECTRONICS CORP

AI summary

A semiconductor device includes a semiconductor substrate, first and second trench electrodes formed on the semiconductor substrate, a floating layer of a first conductivity type formed around the first and second trench electrodes, a floating separation layer of a second conductivity type formed between the first and second trench electrodes and contacted with the floating layer of the first conductivity type and a floating layer control gate disposed on the floating separation layer of the second conductivity type.