GaN HEMT Electrode Formation Using Protective Insulating Film

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The lift-off process for forming electrodes in nitride semiconductor devices can result in redeposition of metal pieces, leading to defects and impaired device properties in nitride semiconductor devices like AlGaN/GaN HEMTs.

Innovation Solution

A method involving the formation of a gate electrode before the source and drain electrodes, using a protective insulating film to prevent redeposition and damage, with specific etching and deposition techniques to create conductive and insulating layers, and heat treatment to reduce contact resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the lift-off process is used to form electrodes, then the electrode formation process is simple, but metal pieces are redeposited causing defects and impaired device properties

Engineering Contradiction:

Improveelectrode formation process simplicityVSAvoiddevice properties

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

A protective insulating film is introduced as an intermediary between the metal electrode material and the nitride semiconductor layer. This film prevents direct contact and redeposition of metal pieces onto the semiconductor layer, thereby eliminating defects while maintaining the simplicity of the electrode formation process.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful function of metal piece redeposition is extracted and eliminated by removing the direct exposure of the nitride semiconductor layer to metal deposition. The protective insulating film isolates the semiconductor layer from the metal deposition process, preventing the harmful redeposition effect.

Inventive Principle:

Principle #2Taking out (Extraction)

2Ease of manufacture

If the nitride semiconductor layer is directly exposed during electrode formation, then the electrode can be formed directly, but the semiconductor layer is damaged by metal pieces and processing

Engineering Contradiction:

Improvedirect electrode formationVSAvoidsemiconductor layer damage

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The protective insulating film is formed beforehand on the nitride semiconductor layer before electrode formation. This film acts as a cushioning layer that absorbs and prevents damage from metal pieces and processing steps, protecting the semiconductor layer while allowing direct electrode formation to proceed.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If heat treatment is applied to form ohmic contacts, then contact resistance is reduced, but the process complexity increases

Engineering Contradiction:

Improvecontact resistanceVSAvoidprocess complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The heat treatment process for forming ohmic contacts is merged with the existing manufacturing process flow. The protective insulating film remains in place during heat treatment, allowing contact resistance reduction to be achieved without adding significant process complexity, as the same heat treatment step serves multiple purposes.

Inventive Principle:

Principle #5Merging (Combining)

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 approach prevents defects and enhances the formation of electrodes without damaging the semiconductor layers, resulting in improved device properties and reduced contact resistance.

Implementation Method 1

a gate insulator is formed on the inner wall of the first opening by vapor evaporation or the like

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Implementation Method 2

first conductive material is deposited by vapor evaporation or the like on the first insulating film via at least a gate insulator

Methodology Applied

Scientific EffectVapor evaporation: Evaporation

Implementation Method 3

heat treatment of a substrate forms ohmic contacts. Thereby, the source electrode and the drain electrode are formed on the nitride semiconductor layer

Methodology Applied

Scientific EffectHeat treatment: Heat Treatment

Data Source

PatentUS9099545B2Compound semiconductor device and method of manufacturing same

Publication Date: 2015.08.04 TRANSPHORM JAPAN

AI summary

A compound semiconductor device includes a substrate; a compound semiconductor layer formed on the substrate; a first insulating film formed on the compound semiconductor layer; a second insulating film formed on the first insulating film; and a gate electrode, a source electrode, and a drain electrode, each being formed on the compound semiconductor layer, wherein the gate electrode is formed of a first opening filled with a first conductive material via at least a gate insulator, and the first opening is formed in the first insulating film and configured to partially expose the compound semiconductor layer, and wherein the source electrode and the drain electrode are formed of a pair of second openings filled with at least a second conductive material, and the second openings are formed in at least the second insulating film and the first insulating film and configured to partially expose the compound semiconductor layer.