Pt Diffusion Barrier for GaN Ohmic Metal Uniformity
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Solution Overview
Problem
Conventional ohmic metal structures for GaN devices suffer from non-uniform top surfaces, ohmic metal spiking, and low breakdown voltage, which affect the reliability and performance of GaN field effect transistors.
Innovation Solution
Incorporating a diffusion barrier seed layer made of Pt on an AlGaN/GaN epitaxial structure, with multiple metal layers such as Ti, Al, Ni, Mo, and Au, and treating them with a rapid thermal annealing process to suppress diffusion and enhance surface uniformity and breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional ohmic metal structure (Ti/Al/Ni/Au or Ti/Al/Ti/Au) is used with rapid thermal annealing process, then the manufacturing process is completed, but the top surface becomes non-uniform with serious protrusion and depression, and tumor forms at the edge
Solution Approach 1:
A Pt diffusion barrier seed layer is deposited on the AlGaN/GaN epitaxial structure before forming the ohmic metal layers. This preliminary action prevents metal diffusion and spiking during subsequent rapid thermal annealing, maintaining surface uniformity and preventing tumor formation at edges.
Solution Approach 2:
The Pt diffusion barrier seed layer acts as an intermediary between the AlGaN/GaN epitaxial structure and the ohmic metal layers (Ti/Al/Ni/Au or Ti/Al/Ti/Au). It mediates the interaction by blocking metal diffusion into the semiconductor, thereby preventing surface non-uniformity and edge tumors during the rapid thermal annealing process.
2Reliability
If conventional ohmic metal structure is used with rapid thermal annealing, then the ohmic contact is formed, but ohmic metal spiking occurs into the epitaxial structure
Solution Approach 1:
The Pt diffusion barrier seed layer serves as an intermediary that prevents ohmic metal spiking into the AlGaN/GaN epitaxial structure during rapid thermal annealing. It allows ohmic contact formation while maintaining the integrity of the epitaxial structure by blocking metal diffusion.
Solution Approach 2:
The harmful diffusion and spiking effects are extracted or removed from the system by introducing the Pt diffusion barrier layer, which isolates the ohmic metal layers from the epitaxial structure and prevents unwanted metal migration.
3Ease of operation
If conventional ohmic metal structure is used, then the device can operate, but the breakdown voltage is low (about 120V) and widely distributed, insufficient for high energy density applications
Solution Approach 1:
The Pt diffusion barrier seed layer is deposited in advance to prevent metal diffusion and spiking, which improves the uniformity and consistency of the ohmic contact. This preliminary action leads to more uniform breakdown voltage values and higher breakdown voltage suitable for high energy density applications.
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 solution results in a smooth and uniform top surface, prevents ohmic metal spiking, and significantly increases the breakdown voltage of GaN devices, making them suitable for high energy density applications.
Implementation Method 1
a diffusion barrier seed layer formed on an epitaxial structure layer, wherein the diffusion barrier seed layer is made of Pt
Implementation Method 2
treating them with a rapid thermal annealing process to suppress diffusion and enhance surface uniformity and breakdown voltage
Data Source
AI summary
An ohmic metal for GaN device comprises a diffusion barrier seed metal layer and a plurality of metal layers. The diffusion barrier seed metal layer is formed on an epitaxial structure layer. The diffusion barrier seed metal layer is made of Pt. The epitaxial structure layer is made of AlGaN or GaN. The plurality of metal layers is formed on the diffusion barrier seed metal layer. The plurality of metal layers comprises a first metal layer and a second metal layer. The first metal layer is formed on the diffusion barrier seed metal layer. The first metal layer is made of Ti. The second metal layer is formed on the first metal layer. The second metal layer is made of Al. By the diffusion barrier seed metal layer, so as to suppress the diffusion of the plurality of metal layers into the epitaxial structure layer.