Columnar Light Emitter Electrode Layout for Stronger Wire Bonding
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Solution Overview
Problem
The formation of asperities on the n-type GaN layer due to differing etching rates between nano-columns and the SOG embedded layer leads to decreased bonding strength when bonding a wire to the n-type electrode in semiconductor lasers with nano-columns.
Innovation Solution
A light emitting device with a laminated structure that includes a substrate, columnar parts, first and second electrodes, a first wiring layer, and an insulating layer, where the first electrode is connected via a contact hole in the insulating layer, and the wiring layer is connected to the first electrode, enhancing bonding strength and current injection uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If etching is performed on the area where nano-columns are formed, then the n-type electrode can be formed in the dug area, but asperities are formed on the surface of the n-type GaN layer due to difference in etching rate between nano-columns and SOG embedded layer
Solution Approach 1:
A planarization layer is introduced as an intermediary between the etched n-type GaN layer and the n-type electrode. This planarization layer fills the asperities and provides a flat surface for electrode formation, thereby resolving the contradiction between enabling electrode formation in the etched area and maintaining surface flatness.
2Productivity
If asperity is formed on the surface of the n-type GaN layer, then the etching process can be completed, but the bonding strength of wire bonding decreases
Solution Approach 1:
The planarization layer serves as a mediator between the asperity-containing n-type GaN layer and the n-type electrode. By providing a flat bonding surface, it ensures strong wire bonding while allowing the etching process to be completed on the underlying layer.
Solution Approach 2:
The planarization layer is formed in advance before electrode and wire bonding processes. This preliminary action of creating a flat surface ensures that subsequent bonding operations can be performed with high strength, preventing the degradation of bonding strength that would otherwise occur due to surface asperities.
3Shape
If concavo-convex shape is formed on the surface of the n-type electrode, then the asperity formation is accommodated, but the bonding strength of wire bonding decreases
Solution Approach 1:
The planarization layer acts as an intermediary that decouples the concavo-convex shape formation in the n-type GaN layer from the electrode surface morphology. It absorbs the surface irregularities and provides a flat upper surface for the electrode, thereby maintaining strong wire bonding strength despite the underlying concavo-convex structure.
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 bonding strength with external terminals and ensures efficient, uniform electrical current injection into the columnar parts, increasing the device's operational efficiency and light emission performance.
Implementation Method 1
a light emitting layer disposed between the first semiconductor layer and the second semiconductor layer
Data Source
AI summary
In the light emitting device, each of columnar parts includes a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type different from the first conductivity type, and a light emitting layer disposed between the first semiconductor layer and the second semiconductor layer, the first semiconductor layer is disposed between a substrate and the light emitting layer, a laminated structure has a third semiconductor layer of the first conductivity type disposed between the substrate and the plurality of columnar parts, a first electrode is electrically connected to the first semiconductor layer via the third semiconductor layer, a contact hole is disposed in an insulating layer at a position overlapping the first electrode when viewed from a stacking direction of the first semiconductor layer and the light emitting layer, the first wiring layer is provided to the insulating layer, and the first wiring layer is electrically connected to the first electrode via the contact hole.