LED Substrate Notch Segmentation for Side Light Control
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Solution Overview
Problem
In light-emitting devices grown on substrates, such as sapphire, a significant amount of light is emitted through the sides of the substrate, which is undesirable in applications requiring top-emitted light, as the substrate often remains part of the final device structure for mechanical stability.
Innovation Solution
Forming notches or cracks in the substrate and then thinning it to expose these separation zones, allowing for the reduction or elimination of side light emission by fully separating the wafer, while maintaining substrate support for the semiconductor structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the growth substrate remains part of the final device structure to provide mechanical stability, then the mechanical strength is improved, but side light emission increases which reduces light emission efficiency
Solution Approach 1:
The substrate is segmented by forming notches that extend from the front surface into the substrate, creating separation zones that divide the continuous substrate into discrete regions. This segmentation allows light to be directed upward through the semiconductor structure while preventing side emission through the notched regions, thus resolving the contradiction between maintaining mechanical support and eliminating energy loss.
Solution Approach 2:
The harmful function of the substrate (side light emission) is extracted by removing material to form notches and separation zones. The substrate is thinned from the back surface to expose and deepen these notches, effectively extracting the light-blocking function while preserving the mechanical support function of the remaining substrate material.
2Loss of energy
If the substrate is thinned to reduce side light emission, then light emission efficiency is improved, but mechanical support is reduced
Solution Approach 1:
The substrate is treated with local quality variations: notches are formed in specific regions between semiconductor structures where mechanical support is less critical, while the substrate between and around the semiconductor structures is thinned to reduce side emission. This localized treatment allows different regions of the substrate to serve different functions - mechanical support in critical areas and light emission control in non-critical areas.
3Loss of energy
If notches are formed in the substrate before thinning, then separation zones are created to direct light upward, but the manufacturing process complexity increases
Solution Approach 1:
Notches are formed in the substrate before the thinning process. This preliminary action creates predefined separation zones that guide the subsequent thinning operation and ensure that when the substrate is thinned, the notches are properly exposed and positioned to function as light-directing features. This sequencing simplifies the overall process by establishing the light management geometry before removing material.
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 method effectively reduces side light emission, enhances mechanical support for the semiconductor structure, and eliminates the need for complex interconnects, thereby improving the efficiency and reliability of light-emitting devices, particularly in applications like automotive lighting.
Implementation Method 1
a modified layer forming step of applying a laser beam to the sapphire substrate from the back side thereof to thereby form a modified layer in the sapphire substrate along each street
Implementation Method 2
a sapphire substrate grinding step of grinding the back side of the sapphire substrate
Data Source
AI summary
A method comprises forming a mask on a first surface of a substrate. The mask is patterned to form openings on the first surface of the substrate. Notches are formed in the first surface of the substrate in the openings. The mask is removed from the first surface of the substrate A plurality of LEDs are provided on the first surface of the substrate and between notches. A second surface of the substrate is thinned to expose the notches and separate the LEDs. The second surface of the substrate is opposite of the first surface of the substrate.