DBR Light-Emitting Structure to Prevent Dicing Cracks
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Solution Overview
Problem
Conventional light-emitting devices face issues with light absorption and reliability due to cracks in the reflective layer during dicing, which can lead to moisture penetration and reduced device reliability.
Innovation Solution
A light-emitting device design featuring a substrate with a dicing street that exposes the second top surface, a semiconductor stack with a Distributed Bragg Reflector structure, and a cap layer that does not cover the second top surface, along with a compact layer for improved film quality and moisture prevention, addresses the cracking issue by optimizing the reflective structure and separation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional reflective layer structure is used during dicing, then light extraction efficiency can be maintained, but cracks occur in the reflective layer leading to moisture penetration and reduced reliability
Solution Approach 1:
The patent applies preliminary action by forming a protective coating layer over the reflective layer before the dicing process. This protective layer is specifically designed to prevent cracks from propagating into the reflective layer during dicing, thereby preventing moisture penetration and maintaining device reliability throughout the manufacturing process and operational lifetime.
Solution Approach 2:
The protective coating layer serves as a cushioning barrier that absorbs and distributes mechanical stresses during dicing. By placing this protective layer beforehand, the patent prevents stress concentration that would otherwise cause cracks in the reflective layer, thus protecting against moisture ingress and ensuring long-term reliability.
2Ease of manufacture
If the cap layer covers the entire substrate surface, then protection is maximized, but light extraction efficiency decreases due to additional interfaces and potential absorption
Solution Approach 1:
The patent applies local quality by selectively positioning the cap layer to cover only specific regions of the substrate - specifically areas requiring protection from moisture and mechanical damage - while leaving the light extraction region exposed. This localized approach maintains protective coverage where needed without interfering with light extraction efficiency in the optical path.
Solution Approach 2:
The substrate surface is segmented into different functional zones: a protected region with the cap layer for mechanical and environmental protection, and an exposed region for optimal light extraction. This segmentation allows each zone to perform its specific function without compromising the other, balancing protection and optical 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 design enhances light extraction efficiency and device reliability by minimizing cracks and moisture ingress, ensuring stable operation and improved performance.
Implementation Method 1
a reflective layer comprising a Distributed Bragg Reflector structure covering the protective layer
Data Source
AI summary
A light-emitting device comprises a substrate comprising a sidewall, a first top surface, and a second top surface, wherein the second top surface is closer to the sidewall of the substrate than the first top surface to the sidewall of the substrate; a semiconductor stack formed on the substrate comprising a first semiconductor layer, an active layer, and a second semiconductor layer; a dicing street surrounding the semiconductor stack, and exposing the first top surface and the second top surface of the substrate; a protective layer covering the semiconductor stack; a reflective layer comprising a Distributed Bragg Reflector structure covering the protective layer; and a cap layer covering the reflective layer, wherein the second top surface of the substrate is not covered by the protective layer, the reflective layer, and the cap layer.