Fluorine-Treated GaN HEMT Gate Dielectric for Normally-Off Operation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Developing III-V semiconductor compound-based devices, such as high electron mobility transistors (HEMTs), faces challenges in improving transistor performance due to complexities in material configurations and circuit complexity, especially in achieving enhancement-mode operation without a negative-polarity voltage supply.

Innovation Solution

A semiconductor structure is formed with a heterojunction between undoped or unintentionally doped gallium nitride (GaN) and intentionally doped aluminum gallium nitride (AlGaN) layers, creating a two-dimensional electron gas (2-DEG) channel, along with a fluorine-treated gate dielectric layer to achieve an enhancement-mode HEMT with a normally-off carrier channel, reducing circuit complexity and cost.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a heterojunction structure with undoped GaN and intentionally doped AlGaN layers is used to create a 2-DEG channel, then electron mobility is enhanced, but the device complexity increases due to multiple material layers and doping configurations

Engineering Contradiction:

Improveelectron mobilityVSAvoidmaterial configuration complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The semiconductor structure is segmented into distinct functional layers: undoped GaN layer for high electron mobility channel, intentionally doped AlGaN layer for carrier supply, and fluorine-treated gate dielectric layer for threshold voltage control. Each layer performs a specific function, allowing optimization of electron mobility while managing complexity through functional segmentation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses composite material structure combining GaN and AlGaN with different band gaps to form heterojunction. This composite approach enables creation of 2-DEG channel with high electron mobility by exploiting the material properties of both compounds, while the fluorine treatment adds another material dimension for threshold voltage stabilization.

Inventive Principle:

Principle #40Composite materials

2Device complexity

If enhancement-mode operation is achieved without negative-polarity voltage supply, then circuit complexity is reduced, but manufacturing precision requirements increase due to fluorine treatment and interface control

Engineering Contradiction:

Improvecircuit complexityVSAvoidinterface control precision

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

Fluorine treatment is performed on the gate dielectric layer before final device assembly and operation. This preliminary action pre-establishes the threshold voltage characteristics and carrier channel properties, allowing the device to achieve enhancement-mode operation without negative voltage supply while simplifying the overall circuit design.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The fluorine treatment modifies the physical and chemical parameters of the gate dielectric layer, including its dielectric constant and interface properties. This parameter change enables precise control of threshold voltage and carrier concentration, achieving normally-off operation while reducing circuit complexity.

Inventive Principle:

Principle #35Parameter changes

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 structure enhances electron mobility and stability of the threshold voltage, simplifies circuit design by eliminating the need for a negative-polarity voltage supply, and reduces manufacturing costs by avoiding gold in metal features, facilitating integration with silicon-fabrication processes.

Implementation Method 1

A HEMT is a field effect transistor incorporating a junction between two materials with different band gaps (i.e., a heterojunction) as the channel

Methodology Applied

Scientific EffectHeterojunction:

Implementation Method 2

creating a two-dimensional electron gas (2-DEG) channel

Methodology Applied

Scientific EffectTwo-dimensional electron gas (2-DEG):

Implementation Method 3

along with a fluorine-treated gate dielectric layer to achieve an enhancement-mode HEMT with a normally-off carrier channel

Methodology Applied

Scientific EffectFluorine treatment:

Data Source

PatentUS9748372B2Semiconductor structure and method of forming the same

Publication Date: 2017.08.29 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method of forming a semiconductor structure includes growing a second III-V compound layer over a first III-V compound layer, wherein the second III-V compound layer has a different band gap from the first III-V compound layer. The method further includes forming a source feature and a drain feature over the second III-V compound layer. The method further includes forming a gate dielectric layer over the second III-V compound layer, the source feature and the drain feature. The method further includes implanting at least one fluorine-containing compound into a portion of the gate dielectric layer. The method further includes forming a gate electrode over the portion of the gate dielectric layer.