Semiconductor Light Emitting Element Al-Based Cover Electrode
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Solution Overview
Problem
Semiconductor light emitting elements using flip-chip mounting face issues with adhesion of insulation films, leading to peeling and gaps, which compromise the barrier function against moisture and oxygen, causing Ag migration and reduced light extraction efficiency due to low reflectance of metals like Ni, Pt, and Ti.
Innovation Solution
A semiconductor light emitting element structure featuring a Ag-based reflection film, an Al-based cover electrode, a metal oxide film, and an insulation film, where the Al-based cover electrode enhances reflectance and prevents Ag migration, while the metal oxide film improves adhesion and protects against environmental factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal film made of Ni, Pt, or Ti is used to prevent Ag migration, then the barrier property to Ag migration is improved, but the reflectance to visible light deteriorates due to low reflectance of these metals
Solution Approach 1:
The metal film is divided into multiple layers with different functions: the first metal film (Ni, Pt, or Ti) provides Ag migration barrier, while the second metal film (Al or Al-based alloy) provides high reflectance. This segmentation allows each layer to specialize in one function, resolving the contradiction between migration prevention and light extraction efficiency.
Solution Approach 2:
The invention uses a composite metal film structure combining different metal materials. The first metal film uses materials with good Ag barrier properties (Ni, Pt, Ti), while the second metal film uses materials with high reflectance (Al or Al-based alloy). This composite structure achieves both Ag migration prevention and high light extraction efficiency simultaneously.
2Reliability
If an insulation film made of oxide or nitride is formed over the metal film, then the protection against environmental factors is improved, but the adhesion property between insulation film and metal film deteriorates causing peeling and gap formation
Solution Approach 1:
A metal oxide film is introduced as an intermediary layer between the metal film and the insulation film. This intermediate metal oxide film serves as a buffer that improves adhesion between the metal film and insulation film, preventing peeling and gap formation while maintaining the protection function against moisture and oxygen.
Solution Approach 2:
The protective structure uses a composite of multiple materials: metal film (for Ag barrier), metal oxide film (for adhesion and protection), and insulation film (for environmental protection). This composite structure resolves the adhesion problem between insulation film and metal film while maintaining protective functions.
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 prevents Ag migration, maintains high light extraction efficiency, and improves the reliability of the semiconductor light emitting element by enhancing the adhesion and reflectance properties.
Implementation Method 1
a first metal film that is provided on an upper surface of the p-type semiconductor layer and of which a surface contacting on the p-type semiconductor layer is made of an Ag or an Ag-based alloy
Implementation Method 2
a metal oxide film that covers other portions of the second metal film and contains at least an oxide of a metal material forming the second metal film
Data Source
AI summary
A semiconductor light emitting element having: a semiconductor laminated body; a full surface electrode containing an Ag provided on an upper surface of the p-type semiconductor layer; a cover electrode that covers a surface of the full surface electrode, is provided to contact on the upper surface of the p-type semiconductor layer at an outer edge of the full surface electrode, and is made of an Al-based metal material; a p-side electrode that is provided on a portion of a surface of the cover electrode; a metal oxide film that covers other surfaces of the cover electrode and contains an oxide of a metal material forming the cover electrode; and an insulation film that is made of an oxide and covers a surface of the metal oxide film, is provided.