HEMT Sidewall Electrode Structure for Low-Resistance Ohmic Contact
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Solution Overview
Problem
Conventional high electron mobility transistor (HEMT) manufacturing processes face challenges in controlling the thickness of the aluminum gallium nitride layer, leading to high contact resistance between the source/drain electrode and the two-dimensional electron gas, which affects the performance and yield of HEMT devices.
Innovation Solution
The method involves forming a semiconductor structure by creating openings with appropriate profiles during the etching process, exposing substantially vertical sidewalls of multiple semiconductor layers, thereby improving the ohmic contact properties between the electrode structure and the two-dimensional electron gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature process is used to melt metal for penetrating the aluminum gallium nitride layer, then the metal can penetrate the layer to form contact, but metal flow occurs which is not beneficial to subsequent processes and the remaining thickness of the aluminum gallium nitride layer becomes hard to control
Solution Approach 1:
The patent changes the temperature parameter from high-temperature melting process to low-temperature deposition process. Instead of melting metal at high temperature to penetrate the AlGaN layer, the invention uses physical vapor deposition or chemical vapor deposition at lower temperatures to deposit metal materials that conformally cover the sidewalls, thereby avoiding metal flow while achieving good ohmic contact.
Solution Approach 2:
The patent replaces the mechanical/thermal penetration mechanism (melting and flowing metal through the layer) with a deposition mechanism (physical or chemical vapor deposition). This substitution allows precise control of the metal layer thickness and eliminates the harmful metal flow effect while maintaining effective electrical contact.
2Reliability
If the remaining thickness of the aluminum gallium nitride layer is made thicker to ensure complete coverage, then the layer can fully cover the sidewalls, but the temperature and heating time required for turning on the device increase significantly
Solution Approach 1:
The patent changes the temperature parameter from high-temperature processing to low-temperature deposition and processing. By using physical vapor deposition or chemical vapor deposition at lower temperatures, the method achieves complete sidewall coverage without requiring increased heating time or temperature, thus reducing the loss of time while maintaining reliable coverage.
3Manufacturing precision
If the etching process penetrates the aluminum gallium nitride layer completely, then the interface profile of the ohmic contact becomes critical, but the contact resistance between the source/drain electrode and the two-dimensional electron gas remains large and difficult to control
Solution Approach 1:
The patent transitions from a planar contact interface to a three-dimensional sidewall contact structure. By depositing metal materials that conformally cover the vertical sidewalls of the etched openings, the invention creates a contact interface that extends in the vertical dimension, increasing the contact area and improving ohmic contact properties while maintaining precise interface control.
Solution Approach 2:
The patent creates a nested structure where the metal electrode material is deposited inside the etched openings, conformally covering the sidewalls. This nested configuration ensures that the metal is positioned precisely within the opening structure, achieving both precise interface profile control and low contact resistance through increased contact area with the two-dimensional electron gas.
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 reduces the contact resistance between the electrode structure and the two-dimensional electron gas, enabling the formation of HEMT devices that meet electrical requirements and improving the product yield.
Implementation Method 1
performing an etching process to form an opening exposing a first vertical sidewall of the first semiconductor layer and a second vertical sidewall of the second semiconductor layer
Data Source
AI summary
A method for forming a semiconductor structure is provided. The method includes forming a second semiconductor layer on a first semiconductor layer. The first semiconductor layer and the second semiconductor layer have different energy bandgaps. The method further includes performing an etching process to form an opening exposing a first vertical sidewall of the first semiconductor layer and a second vertical sidewall of the second semiconductor layer. The method further includes forming an electrode structure in the opening to cover the first vertical sidewall and the second vertical sidewall.