HEMT Gate Electrode Inclined Sidewalls for Leakage Control

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Solution Overview

Problem

Current high electron mobility transistors (HEMTs) face issues with current leakage due to potential differences and fringing fields under high forward gate bias, leading to reverse channel formation and increased leakage.

Innovation Solution

A method for fabricating HEMTs involving the formation of a gate electrode with inclined sidewalls through the use of fluorine-containing gases, which etches the p-type semiconductor layer to form a reverse trapezoid shape, reducing sidewall current leakage by consuming the byproduct accumulated on the gate electrode's sidewalls.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional gate electrode structure with vertical sidewalls is used, then the fabrication process is simple, but current leakage occurs due to potential differences and fringing fields under high forward gate bias

Engineering Contradiction:

Improvecurrent leakage preventionVSAvoidgate electrode structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The gate electrode structure transitions from vertical sidewalls to inclined sidewalls, creating an asymmetric geometry that reduces fringing fields at the sidewalls. This asymmetric design prevents reverse channel formation and current leakage while maintaining the essential gate electrode function.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The sidewall angle of the gate electrode is changed from vertical (90 degrees) to inclined (non-90 degrees), modifying the geometric parameters to reduce electric field concentration at the sidewalls and prevent current leakage under high forward gate bias conditions.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If fluorine-containing gas is used to etch the p-type semiconductor layer, then inclined sidewalls are formed to reduce current leakage, but the etching process becomes more complex

Engineering Contradiction:

Improvesidewall current leakage reductionVSAvoidetching process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The fluorine-containing gas etching process, which could be considered complex, creates a beneficial self-limiting effect where the etching naturally forms inclined sidewalls with reduced fringing fields. The process converts the complexity of selective etching into a benefit by automatically creating the optimal gate electrode geometry for leakage reduction.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 formation of inclined sidewalls effectively prevents current leakage, enhancing the transistor's performance under high temperature gate bias conditions.

Implementation Method 1

the use of fluorine-containing gases, which etches the p-type semiconductor layer to form a reverse trapezoid shape

Methodology Applied

Scientific EffectEtching:

Data Source

PatentEP4328976A1High electron mobility transistor and method for fabricating the same

Publication Date: 2024.02.28 UNITED MICROELECTRONICS CORP

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AI summary

A method for fabricating a high electron mobility transistor (HEMT) includes the steps of forming a buffer layer (14) on a substrate (12), forming a barrier layer (16) on the buffer layer, forming a p-type semiconductor layer (18) on the barrier layer, forming a gate electrode layer (26) on the p-type semiconductor layer, and patterning the gate electrode layer to form a gate electrode. The gate electrode includes an inclined sidewall.