MOS Transistor Air-Gap Structure for Lower Gate Charge

Solution Overview

Problem

In metal-oxide semiconductor transistors, particularly in high voltage applications, there is a challenge in reducing the gate charge (Qg) while maintaining the breakdown voltage (BV), which affects switch loss control and is crucial for advanced node performance.

Innovation Solution

The introduction of an air gap within the insulator material extending into the drift region and the use of a field plate adjacent to or over this air gap, which reduces parasitic capacitance and enhances breakdown voltage by depleting the drift region and reducing surface electric fields.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the insulator material is made thicker to increase breakdown voltage, then breakdown voltage is improved, but parasitic capacitance increases and gate charge increases

Engineering Contradiction:

Improvebreakdown voltageVSAvoidgate charge

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The patent introduces an air gap specifically in the drain region where high electric field stress occurs, while maintaining continuous insulator material in other regions. This localized modification reduces parasitic capacitance in the high-stress area without compromising overall breakdown voltage, thereby reducing gate charge while maintaining the required voltage blocking capability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent creates a composite insulator structure combining solid dielectric material and air (vacuum) regions. The air gap portion has zero dielectric material, effectively reducing parasitic capacitance, while the surrounding solid insulator material maintains the breakdown voltage. This composite approach allows optimization of both breakdown voltage and gate charge parameters.

Inventive Principle:

Principle #40Composite materials

2Strength

If the drift region is extended to increase breakdown voltage, then breakdown voltage is improved, but device area increases and parasitic capacitance increases

Engineering Contradiction:

Improvebreakdown voltageVSAvoiddevice area

Core Design Contradiction:

StrengthVSArea of stationary object

Solution Approach 1:

The air gap is introduced specifically in the drain region where the electric field is most intense during breakdown conditions. This localized modification allows the drift region to be optimized for breakdown voltage without requiring excessive extension, thereby controlling device area while achieving the required voltage blocking capability.

Inventive Principle:

Principle #3Local quality

3Loss of energy

If the insulator material is made thinner to reduce gate charge, then gate charge is reduced, but breakdown voltage decreases

Engineering Contradiction:

Improvegate chargeVSAvoidbreakdown voltage

Core Design Contradiction:

Loss of energyVSStrength

Solution Approach 1:

The patent introduces an air gap specifically in the drain region where high electric field stress occurs, while maintaining continuous insulator material in other regions. This localized modification reduces parasitic capacitance in the high-stress area without compromising overall breakdown voltage, thereby reducing gate charge while maintaining the required voltage blocking capability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent creates a composite insulator structure combining solid dielectric material and air (vacuum) regions. The air gap portion has zero dielectric material, effectively reducing parasitic capacitance, while the surrounding solid insulator material maintains the breakdown voltage. This composite approach allows optimization of both breakdown voltage and gate charge parameters.

Inventive Principle:

Principle #40Composite materials

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 effectively reduces parasitic capacitance and increases breakdown voltage, improving the performance of metal-oxide semiconductor transistors by controlling switch loss and enhancing their operational efficiency in high voltage applications.

Implementation Method 1

The introduction of an air gap within the insulator material extending into the drift region and the use of a field plate adjacent to or over this air gap, which reduces parasitic capacitance

Methodology Applied

Scientific EffectParasitic capacitance reduction: Capacitance

Implementation Method 2

enhances breakdown voltage by depleting the drift region and reducing surface electric fields

Methodology Applied

Scientific EffectElectric field depletion: Electric Field

Implementation Method 3

reduces surface electric fields

Methodology Applied

Scientific EffectElectric field reduction: Electric Field

Data Source

PatentUS20250015181A1Metal-oxide semiconductor transistors

Publication Date: 2025.01.09 GLOBALFOUNDRIES SINGAPORE PTE LTD

AI summary

The present disclosure relates to semiconductor structures and, more particularly, to metal-oxide semiconductor transistors and methods of manufacture. The structure includes: a substrate comprising a drift region and a body region; a gate structure between the drift region and the body region; an insulator material over the gate structure, the drift region and the body region; and an air gap within the insulator material and extending into the drift region.