Silver Reflective Electrode Sulfidation Prevention
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Solution Overview
Problem
The degradation of silver (Ag) reflective electrode layers in nitride semiconductor light emitting elements due to sulfidation reactions, which reduces reflectance and product lifetime, is a challenge in existing technologies.
Innovation Solution
A barrier metal layer made of titanium (Ti), tantalum (Ta), ruthenium (Ru), or their alloys is used to prevent sulfur penetration and block the sulfidation of the silver layer, while also enhancing contact with copper interconnections and improving product reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a silver (Ag) reflective electrode layer is used in nitride semiconductor light emitting elements, then high reflectance is achieved, but the reflective electrode layer degrades due to sulfidation reactions reducing product lifetime
Solution Approach 1:
A barrier metal layer is introduced as an intermediary between the silver reflective electrode layer and the external environment. This barrier layer selectively blocks sulfur penetration while maintaining electrical conductivity and mechanical integrity, thereby preventing sulfidation of the silver layer without compromising its reflective properties
Solution Approach 2:
The electrode structure is transformed from a single-material silver layer to a composite multi-layer structure consisting of the barrier metal layer and the silver reflective layer. This composite structure combines the sulfur-blocking properties of the barrier metal with the high reflectance of silver, resolving the contradiction between maintainability and performance
2Reliability
If a protective cover is added to prevent sulfidation of the silver layer, then product lifetime is extended, but device complexity increases
Solution Approach 1:
The barrier metal layer performs multiple functions simultaneously: it acts as a sulfur diffusion barrier to prevent sulfidation, provides electrical conductivity for the electrode, and serves as an adhesive layer between the silver reflective layer and the underlying structure. This multi-functionality prevents the need for additional separate protective components
3Reliability
If the barrier metal layer is made of Ru metal, then sulfur penetration is blocked effectively, but manufacturing cost increases
Solution Approach 1:
The invention changes the material parameter of the barrier layer from expensive Ru metal to cost-effective alternative metals such as Ti or Ta that provide equivalent sulfur-blocking performance. This parameter change maintains the functional requirement of preventing sulfur penetration while significantly reducing manufacturing costs
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 effectively suppresses the degradation of the silver reflective layer, maintaining high reflectance and extending the product lifetime by preventing sulfidation, and enhances contact reliability with copper interconnections.
Implementation Method 1
degradation of the reflective electrode layer may affect the product lifetime... prevent sulfur penetration and block the sulfidation of the silver layer
Data Source
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Figure 3A~3B
AI summary
According to one embodiment, a semiconductor light emitting device includes a semiconductor layer, a first electrode, a second electrode, an insulating film, a first interconnection, a second interconnection, a barrier metal layer, a first metal pillar, a second metal pillar, and a resin. The semiconductor layer has a first major surface, a second major surface formed on an opposite side to the first major surface, and a light emitting layer. The first electrode is provided on the second major surface of the semiconductor layer. The second electrode is provided on the second major surface of the semiconductor layer and includes a silver layer. The insulating film is provided on the second major surface side of the semiconductor layer. The barrier metal layer is provided between the second electrode and the insulating film and between the second electrode and the second interconnection to cover the second electrode.