Surface-Emitting Laser Electrode Stack for Cu Diffusion Control
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Solution Overview
Problem
Conventional surface emitting laser devices experience issues with weak bonding strength between the electrode and the substrate, leading to electrical characteristics being compromised due to separation or partial contact, which affects the reliability and ohmic characteristics.
Innovation Solution
Incorporating a copper (Cu) first metal layer as a bonding layer with a barrier layer to prevent copper diffusion and an antioxidant layer to prevent oxidation, enhancing the adhesion and electrical conductivity between the metal layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a metal paste material is used to bond the electrode to the substrate, then the bonding process is simple, but the bonding strength is weak causing electrode separation
Solution Approach 1:
The patent employs a composite metal layer structure consisting of a first metal layer (Ag), a second metal layer (Cu), and a third metal layer (Ni or Pd). This composite structure combines the advantages of each material: Ag provides good bonding with metal paste, Cu provides high electrical conductivity, and Ni/Pd provides strong bonding strength and diffusion barrier properties, thereby resolving the contradiction between manufacturing simplicity and bonding strength.
Solution Approach 2:
The second metal layer (Cu) and third metal layer (Ni or Pd) act as intermediary layers between the first metal layer (Ag) and the substrate. These intermediary layers enhance the bonding strength and prevent direct contact between Ag and the substrate, avoiding Ag diffusion while maintaining electrical conductivity, thus solving the electrode separation problem.
2Ease of manufacture
If the electrode metal is separated from the substrate, then the manufacturing process is simpler, but the electrical characteristics are compromised
Solution Approach 1:
The multi-layer metal structure (Ag-Cu-Ni/Pd) ensures reliable electrical characteristics by combining materials with complementary properties. The Cu layer provides high electrical conductivity, while the Ni or Pd layer ensures strong adhesion and acts as a diffusion barrier, preventing electrode separation and maintaining consistent electrical performance.
Solution Approach 2:
The patent optimizes the thickness parameters of each metal layer to achieve the desired balance between electrical conductivity and bonding strength. By controlling the thickness of the Cu layer (for conductivity) and the Ni/Pd layer (for adhesion and diffusion prevention), the electrode maintains reliable electrical characteristics without separation issues.
3Reliability
If copper is used to enhance electrical conductivity, then the ohmic characteristics improve, but copper diffusion into other metal layers occurs
Solution Approach 1:
The third metal layer (Ni or Pd) serves as an intermediary barrier layer between the Cu layer and other metal layers. This barrier layer prevents Cu diffusion into the Ag layer or substrate while maintaining the high electrical conductivity of the Cu layer, thus preserving both ohmic characteristics and compositional stability.
Solution Approach 2:
The composite metal layer structure (Ag-Cu-Ni/Pd) systematically addresses the copper diffusion issue by positioning Ni or Pd as a diffusion barrier. This composite structure allows Cu to provide excellent electrical conductivity while the Ni/Pd layer maintains the stability of the overall metal layer composition by preventing unwanted diffusion.
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 improves the bonding strength, reliability, and ohmic characteristics of the surface emitting laser device by preventing separation and maintaining electrical conductivity, thus enhancing the overall performance.
Implementation Method 1
The third metal layer may prevent diffusion of copper from the second metal layer into the first metal layer
Implementation Method 2
an antioxidant layer to prevent oxidation
Data Source
AI summary
The surface emitting laser device according to the embodiment includes a substrate, a first metal layer disposed on the substrate, a second metal layer disposed on the first metal layer, and a third metal layer disposed between the first metal layer and the second metal layer.The first to third metal layers may include different materials, and the second metal layer may include copper (Cu).The third metal layer may prevent diffusion of copper from the second metal layer into the first metal layer.