Semiconductor Light Emitting Device Metal Buffer Layer Crack Resistance
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Solution Overview
Problem
Semiconductor light emitting devices face reliability issues due to cracks in electrodes and insulating layers, particularly under stress from differences in thermal expansion coefficients during bonding with external devices.
Innovation Solution
A semiconductor light emitting device structure is developed with a metal buffer layer having higher fracture toughness than the capping layer, encompassing the upper and lateral surfaces of the capping layer, and extending to expose portions of the electrodes, thereby preventing crack propagation and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional electrode structure with capping layer is used, then the device can be manufactured with standard processes, but cracks occur in the electrodes and insulating layers due to thermal expansion stress
Solution Approach 1:
The patent applies composite materials by creating a multi-layer electrode structure consisting of a contact layer, capping layer, and metal buffer layer. Each layer is made of different materials with specific properties: the contact layer (e.g., Ti, Ni) provides adhesion to the semiconductor, the capping layer (e.g., Cr, Pt, Au) provides oxidation resistance, and the metal buffer layer (e.g., Al, Cu, Ag) provides mechanical stress relief. This composite structure resolves the contradiction by combining materials with complementary properties to simultaneously achieve reliability and manufacturability.
Solution Approach 2:
The patent applies local quality by giving different regions of the electrode structure different properties. The metal buffer layer is strategically positioned between the capping layer and insulating layer, and its thickness is optimized (thicker than contact or capping layers) to specifically address stress concentration at critical interfaces. This localized enhancement of crack resistance at stress-prone regions resolves the contradiction without requiring complete restructuring of the entire device.
2Reliability
If the metal buffer layer is made thicker to prevent cracks, then crack resistance improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness parameters of each layer. The metal buffer layer is designed to be thicker than the contact or capping layers to provide sufficient stress relief, while the contact and capping layers are kept thinner to minimize total electrode thickness and reduce manufacturing complexity. By carefully selecting and optimizing these thickness parameters, the patent achieves crack resistance without excessively increasing manufacturing precision requirements.
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 metal buffer layer effectively prevents cracks in the contact and capping layers, improving the reliability of the semiconductor light emitting device by reducing stress-induced failures and enhancing light extraction efficiency.
Implementation Method 1
differences in thermal expansion coefficients during bonding with external devices
Implementation Method 2
metal buffer layer having higher fracture toughness than the capping layer
Data Source
AI summary
A semiconductor light emitting device including a light emitting structure including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer; a first electrode connected to the first conductivity type semiconductor layer; a second electrode including a contact layer connected to the second conductivity type semiconductor layer, a capping layer disposed on the contact layer, and a metal buffer layer disposed on the capping layer, the metal buffer layer encompasses an upper and lateral surface of the capping layer; a first insulating layer disposed on the light emitting structure such that the first and second electrodes are exposed; and a second insulating layer disposed on the first insulating layer such that at least a portion of the first electrode and at least a portion of the metal buffer layer are exposed.