Bond Pad Trench Design for LED Light Extraction
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Solution Overview
Problem
Current LED packages face challenges in maximizing light extraction efficiency due to high current density around bond pads, which leads to light trapping and reduced output, especially in vertical geometry LED chips with active backside mounting pads.
Innovation Solution
The implementation of a trench structure around bond pads on the semiconductor structure to physically isolate them from the primary emission surface, allowing current to flow away from the pads before reaching the active region, thereby reducing light absorption and increasing overall light output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bond pads are placed on the primary emission surface for electrical connection, then electrical connectivity is achieved, but light extraction efficiency deteriorates due to light trapping and absorption near the bond pads
Solution Approach 1:
The patent segments the bond pad structure by introducing trenches that divide the bond pad into isolated regions. This segmentation prevents continuous light propagation paths beneath the bond pad, reducing light trapping while maintaining electrical connectivity through the segmented conductive regions.
Solution Approach 2:
The patent introduces trenches as intermediary structures between the bond pad and the underlying semiconductor layers. These trenches act as optical barriers that mediate the interaction between electrical conductors and light propagation, blocking trapped light while allowing electrical current to pass through the bond pad material.
2Reliability
If current density is concentrated around bond pads for efficient electrical connection, then electrical connectivity is improved, but light absorption increases reducing overall light output
Solution Approach 1:
The trench structure segments the high current density region into isolated zones, preventing the formation of continuous high-density current paths that would generate excessive heat and light absorption. The segmentation distributes current flow more evenly while maintaining necessary electrical connections.
Solution Approach 2:
The patent converts the potentially harmful effect of current concentration (light absorption and heat generation) into a beneficial structure by using trenches to channel and distribute the current. The trenches guide current flow in a way that reduces parasitic light absorption while maintaining efficient electrical connectivity.
3Adaptability or versatility
If vertical geometry LED chips with active backside mounting pads are used, then individual control of LED chips is achieved, but light extraction efficiency deteriorates due to complicated package design and light trapping
Solution Approach 1:
The patent applies segmentation to the bond pad structure on the active surface, using trenches to create isolated conductive regions. This allows individual control of LED chips through the bond pads while simultaneously improving light extraction by preventing light trapping in the segmented regions.
Solution Approach 2:
The patent moves the primary electrical connection interface from the backside mounting pad to the active surface bond pads, utilizing the surface dimension for both light emission and electrical connection. This dimensional reorganization simplifies the package design while maintaining individual control capability and improving light extraction.
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 by approximately 4% without significant changes to the fabrication process, improving the LED chip's ability to emit more light while maintaining electrical connectivity.
Implementation Method 1
The high current density around the bond pads 104 causes more light to be generated in portions of the active region 204 near the bond pads 104. Some of the light generated in this area gets trapped underneath the bond pads 104 and ultimately absorbed
Data Source
AI summary
An improved bond pad design for increased light extraction efficiency for use in light emitting diodes (LEDs) and LED packages. Embodiments of the present invention incorporate a structure that physically isolates the bond pads from the primary emission surface, forcing the current to flow away from the bond pads first before traveling down into the semiconductor material toward the active region. This structure reduces the amount of light that is generated in the area near the bond pads, so that less of the generated light is trapped underneath the bond pads and absorbed.