HEMT Gate Stack With WN Barrier for Lower Gate Leakage
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Solution Overview
Problem
High electron mobility transistors (HEMTs) based on AlGaN/GaN heterostructures face significant gate leakage current issues due to reduced Schottky barrier potential, which affects their radiofrequency (RF) performance, and existing solutions like using Nickel as a contact metal are not optimal as they either contaminate CMOS production lines or fail to effectively reduce leakage current.
Innovation Solution
A method for manufacturing HEMT devices involves a gate region formed by a stack of layers including a Nickel layer for Schottky contact, a Tungsten Nitride layer as a diffusion barrier, an Aluminium layer for reduced resistivity, and a Titanium Nitride cap layer for protection, which prevents Aluminium diffusion and corrosion, while being compatible with CMOS processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Nickel is used as contact metal to reduce gate leakage current, then gate leakage current is reduced, but Gold coverage is required which contaminates CMOS production lines
Solution Approach 1:
The patent extracts and removes the harmful Gold layer from the gate electrode structure, retaining only the essential Nickel layer that provides the Schottky barrier function. This eliminates the contamination issue while preserving the gate leakage reduction benefit.
Solution Approach 2:
The patent uses a simpler, cheaper material combination (Nickel alone or with CMOS-compatible materials) that does not require expensive Gold coverage and does not contaminate production lines, making the process suitable for standard CMOS manufacturing.
2Ease of manufacture
If a simple single-layer gate electrode is used, then manufacturing complexity is reduced, but gate leakage current control and material stability are insufficient
Solution Approach 1:
The gate electrode uses a composite multi-layer structure combining materials with complementary properties: Nickel for Schottky barrier, Aluminium for conductivity, and diffusion barrier materials for stability. This composite approach achieves superior performance while remaining compatible with standard CMOS fabrication processes.
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 effectively reduces gate leakage current, enhancing RF performance and ensuring compatibility with CMOS production lines by preventing Aluminium diffusion and corrosion, thus improving the overall performance of GaN-based HEMT devices for RF applications.
Implementation Method 1
a Tungsten Nitride layer as a diffusion barrier
Implementation Method 2
a Nickel layer for Schottky contact
Data Source
Figure 1~2
Figure 3A~3C
Figure 3D~3E
AI summary
Method for manufacturing a HEMT device (1) including the steps of: forming, on a heterostructure (3), a single dielectric layer (7); forming a through opening (9) through the dielectric layer; and forming a gate electrode (8) at the through opening. Forming the gate electrode includes: forming a sacrificial structure (34); depositing by evaporation a Ni layer (20); carrying out a lift-off of the sacrificial structure; depositing a WN layer (22) by sputtering; and depositing an Al layer (24). The WN layer forms a barrier against the diffusion of Al atoms towards the heterostructure.