GaN Semiconductor Electrode Barrier Layer for Al Diffusion Control
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Solution Overview
Problem
In GaN-based power semiconductor devices, the use of Au as a pad electrode leads to degradation due to heat-generated alloy formation with Al wires, increasing costs and degrading device characteristics, while Al pad electrodes suffer from heat-induced Al diffusion into the semiconductor layer, affecting device performance.
Innovation Solution
A semiconductor device with a GaN semiconductor layer and an electrode system featuring a barrier layer of W, TiW, WN, TiN, Ta, or TaN between the electrode main body and the Al connection-use electrode, with a surface roughness of 3.0 nm or less, to prevent Al diffusion and enhance device stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Au is used as pad electrode material, then low resistance and good electrical properties are achieved, but heat-induced alloy formation with Al wires degrades device characteristics and increases cost
Solution Approach 1:
A barrier layer composed of W, TiW, WN, TiN, Ta, or TaN is introduced as an intermediary between the Al connection-use electrode and the Au electrode main body. This barrier layer prevents direct contact and alloy formation between Al and Au during heat treatment, while maintaining electrical conductivity and mechanical integrity of the electrode structure.
Solution Approach 2:
The electrode structure is designed as a composite multi-layer system combining different materials (Al connection electrode + barrier layer + Au electrode main body) to achieve both low resistance (from Au) and heat stability (from barrier layer preventing Al-Ga alloy formation in the semiconductor layer).
2Ease of manufacture
If Al is used as pad electrode material to reduce cost, then cost is reduced, but heat-induced Al diffusion into the semiconductor layer degrades device characteristics
Solution Approach 1:
The barrier layer acts as a protective intermediary between the Al connection electrode and the GaN semiconductor layer, preventing Al diffusion into the semiconductor during heat treatment while allowing the Al electrode to maintain its low-cost advantage.
Solution Approach 2:
The barrier layer is formed in advance before the connection electrode is deposited, creating a pre-protection mechanism that prevents Al diffusion into the semiconductor layer before the harmful diffusion process can occur during subsequent heat treatment or device operation.
3Strength
If barrier layer surface roughness is increased to improve adhesion, then adhesion strength is improved, but Al diffusion increases due to larger surface area
Solution Approach 1:
The surface roughness of the barrier layer is precisely controlled within the range of 0.5 nm to 3.0 nm RMS. This parameter optimization achieves sufficient adhesion strength for the connection electrode while minimizing the surface area available for Al diffusion, thereby preventing harmful Al-Ga alloy formation in the semiconductor layer.
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 barrier layer effectively suppresses Al diffusion and leak current, maintaining device characteristics and reducing costs by preventing Au alloy formation, thus enhancing the performance and reliability of GaN-based power semiconductor devices.
Implementation Method 1
a barrier layer formed between the electrode main body and the connection-use electrode, the barrier layer containing at least one selected from the group consisting of W (tungsten), TiW (titanium tungsten), WN (tungsten nitride), TiN (titanium nitride), Ta (tantalum), and TaN (tantalum nitride)
Data Source
AI summary
A semiconductor device includes a semiconductor layer (1) containing GaN and an electrode. The electrode includes an electrode main body (6), a connection-use electrode (8) containing Al and formed at a position farther from the semiconductor layer (1) than the electrode main body (6), and a barrier layer (7) formed between the electrode main body (6) and the connection-use electrode (8), the barrier layer (7) containing at least one selected from the group consisting of W, TiW, WN, TiN, Ta, and TaN. A surface roughness RMS of the barrier layer (7) is 3.0 nm or less.