GaN Semiconductor Electrode Structure for Wire Bonding Reliability
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Solution Overview
Problem
The existing semiconductor light-emitting elements using GaN-based compound semiconductors face issues with electrode joining properties and reliability due to pressure applied during wire bonding, which can cause separation or cracks in the transparent electrode layer.
Innovation Solution
A semiconductor light-emitting element with a specific electrode structure comprising a first metal layer of Au and a second metal layer with lower hardness, both made of Au, where the second metal layer is thinner and exposed externally, improving bonding wire attachment and reducing mechanical stress on the transparent conductive layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer Au electrode structure is used, then the manufacturing process is simple, but the joining properties and reliability during wire bonding are insufficient due to high hardness causing separation or cracks
Solution Approach 1:
The electrode structure is segmented into multiple layers: a first Au layer with higher hardness for mechanical strength and a second Au layer with lower hardness for wire bonding. This segmentation allows each layer to perform its specific function, resolving the contradiction between structural simplicity and bonding reliability.
Solution Approach 2:
Different regions of the electrode structure have different hardness properties. The first Au layer (near the transparent electrode) has higher hardness to prevent cracks, while the second Au layer (exposed surface) has lower hardness to facilitate wire bonding. This local quality differentiation resolves the contradiction between reliability and structural complexity.
2Strength
If high pressure is applied during wire bonding to ensure good joining, then the bonding strength is improved, but separation of the electrode pad or cracks in the transparent electrode layer occur
Solution Approach 1:
The hardness parameter of the Au layer is changed by creating a gradient structure. The second Au layer has lower hardness (softer) to allow bonding at reduced pressure, while the first Au layer maintains higher hardness for overall strength. This parameter change resolves the contradiction between bonding strength and mechanical stress damage.
Solution Approach 2:
The two-layer Au structure acts as an intermediary between the hard transparent electrode and the bonding wire. The softer second layer mediates the bonding process by accommodating deformation, while the harder first layer protects the transparent electrode from stress, resolving the contradiction between strength and stress damage.
3Strength
If the electrode pad is made of hard material to increase durability, then the electrode strength is improved, but the wire bonding process causes separation or cracks due to excessive hardness
Solution Approach 1:
The electrode structure exhibits dynamic properties through its layered composition. The softer second Au layer deforms elastically during bonding to facilitate wire attachment, while the harder first Au layer maintains overall structural integrity. This dynamic behavior resolves the contradiction between electrode strength and wire bonding ease.
Solution Approach 2:
The electrode uses a composite structure of two Au layers with different hardness characteristics. This composite material approach combines the advantages of both hard and soft materials, achieving both electrode strength and wire bonding ease without requiring completely different materials.
Data Source
AI summary
It is an object to improve joining properties of electrodes and reliability of the electrodes for supplying electrical power to a semiconductor. The semiconductor light-emitting element includes an n-type semiconductor layer, a light-emitting layer, a p-type semiconductor layer, a transparent conductive layer, a p-electrode formed on the transparent conductive layer and an n-electrode formed on the n-type semiconductor layer. The p-electrode includes a p-side second metal layer composed of a metallic material containing Au and provided to be exposed to the outside and a p-side first metal layer composed of a metallic material containing Au with hardness higher than that of the metallic material composing the p-side second metal layer, the p-side first metal layer being provided closer to the transparent conductive layer than the p-side second metal layer along the p-side second metal layer.