Nitride Semiconductor Electrode Au Diffusion Barrier
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Solution Overview
Problem
In ultraviolet light emitting elements with a wavelength of 365 nm or less, the high AlN mole fraction in n-type and p-type AlGaN semiconductor layers requires heat treatment at 600°C or more to form electrodes, leading to Au alloying and increased production costs due to the need for additional steps to prevent Au diffusion and ensure wire bonding.
Innovation Solution
A common laminated structure for the n-electrode and p-electrode with an Au diffusion preventing layer composed of conductive metal oxide, such as ITO, is used, allowing for simultaneous annealing of both electrodes without increasing the number of steps, thereby preventing Au alloying and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment at 600°C or more is performed to form electrodes on high AlN mole fraction AlGaN layers, then ohmic contact is achieved, but Au alloying occurs and wire bonding becomes difficult
Solution Approach 1:
A barrier metal layer (Ru, Rh, Ir, Os, Pd, Pt, or their alloys) with high melting point is introduced as an intermediary between the Au layer and the AlGaN semiconductor layer. This barrier layer prevents direct contact between Au and the semiconductor during heat treatment, blocking Au diffusion while maintaining electrical conductivity and enabling subsequent wire bonding operations.
2Ease of operation
If additional steps are added to prevent Au diffusion, then wire bonding quality improves, but production cost increases
Solution Approach 1:
The barrier metal layer is deposited during the initial electrode formation process, before heat treatment and wire bonding steps. This preliminary incorporation of the barrier layer prevents Au diffusion during subsequent processing without requiring additional corrective steps later in the manufacturing process.
3Ease of operation
If Au layer is used for wire bonding, then bonding performance is good, but Au diffuses during heat treatment and degrades electrode surface
Solution Approach 1:
The barrier metal layer serves as a protective intermediary that physically separates the Au layer from the AlGaN semiconductor layer during heat treatment. This prevents Au atoms from diffusing into the semiconductor, maintaining both the electrode surface integrity and the Au layer composition for optimal wire bonding performance.
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 prevents Au diffusion during annealing, ensuring stable ohmic contact and improved external quantum efficiency without increasing production costs, as evidenced by successful wire bonding and maintained Au layers on the electrode surfaces.
Implementation Method 1
an Au diffusion preventing layer composed of conductive metal oxide and formed under the uppermost layer to prevent Au diffusion
Implementation Method 2
the n-electrode and the p-electrode are each subjected to a heat treatment such as annealing or sintering after deposited and patterned
Data Source
Figure 1
Figure 2A~2H
Figure 3A~3B
AI summary
A nitride semiconductor element 1 includes a base structure part 5, and an element structure part 11 formed on the base structure part 5 and having at least an n-type AlGaN based semiconductor layer 6, and p-type AlGaN based semiconductor layers 8, 9, 10, and further includes an n-electrode contact part 13a formed on the n-type AlGaN based semiconductor layer 6, an n-electrode pad part 13b formed on the n-electrode contact part 13a, and a p-electrode 12 formed on the p-type AlGaN based semiconductor layers 8, 9, 10, in which an AIN mole fraction in the n-type AlGaN based semiconductor layer 6 is 20% or more, the n-electrode contact part 13a includes one or more metal layers, and the p-electrode 12 and the n-electrode pad part 13b have a common laminated structure of two or more layers having an Au layer as an uppermost layer, and an Au diffusion preventing layer composed of conductive metal oxide and formed under the uppermost layer to prevent Au diffusion.