HEMT Barrier Layer Recess for Normally Off Threshold Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional methods for fabricating high electron mobility transistors (HEMTs) face challenges in achieving a 'normally off' operation mode and preventing damage to the region under the gate electrode during the etching process, which affects the threshold voltage and device performance.

Innovation Solution

The method involves forming a patterned mask on the first barrier layer, creating a second barrier layer adjacent to the mask, and then forming the gate, source, and drain electrodes after removing the mask to create a recess, while adjusting the thickness and aluminum concentration of the barrier layers to achieve a 'normally off' operation mode and minimize etching damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional etching process is used to form gate electrode, then gate electrode can be formed, but the region under the gate electrode is damaged and threshold voltage cannot be properly controlled

Engineering Contradiction:

Improvethreshold voltage controlVSAvoidetching damage

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

A mask layer is formed on the barrier layer before the etching process to protect the region under the gate electrode from etching damage. This preliminary protective action prevents the harmful effects of etching on the threshold voltage control while still allowing the gate electrode to be properly formed.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The mask layer acts as an intermediary between the etching process and the barrier layer, preventing direct contact between the etching chemicals and the sensitive region under the gate electrode. This intermediary layer enables the etching process to proceed without causing damage to the threshold voltage control region.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If barrier layer thickness and aluminum concentration are not adjusted, then fabrication is simpler, but normally off operation mode cannot be achieved

Engineering Contradiction:

Improveoperation mode controlVSAvoidbarrier layer structure

Core Design Contradiction:

Ease of operationVSDevice complexity

Solution Approach 1:

The barrier layer is designed with specific thickness and aluminum concentration parameters to achieve the normally off operation mode. By carefully controlling these parameters, the device can be switched off when no gate voltage is applied, providing better power control while maintaining a manageable fabrication process.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11894453B2High electron mobility transistor with improved barrier layer

Publication Date: 2024.02.06 UNITED MICROELECTRONICS CORP

AI summary

A method for fabricating high electron mobility transistor (HEMT) includes the steps of: forming a buffer layer on a substrate; forming a barrier layer on the buffer layer; forming a gate dielectric layer on the barrier layer; forming a work function metal layer on the gate dielectric layer; patterning the work function metal layer and the gate dielectric layer; forming a gate electrode on the work function metal layer; and forming a source electrode and a drain electrode adjacent to two sides of the gate electrode.