Sapphire Wafer Cleavage Patterning for UV Light Extraction
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Solution Overview
Problem
Existing methods for manufacturing light-emitting elements using sapphire substrates often result in uniform side surfaces, which can limit light extraction efficiency, particularly for deep ultraviolet light, as the shape of the side surface is dependent on the crystal plane and does not allow for optimal light extraction.
Innovation Solution
A method involving laser beam irradiation along specific axes of the sapphire substrate to create multiple modified regions at varying distances, allowing for uneven surfaces that enhance light extraction by increasing the surface area and altering the cracking pattern during cleavage, thereby improving light-emitting element efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser beam is concentrated in the substrate interior to form modified regions for wafer cleavage, then the wafer can be separated into individual elements, but the side surface shape is determined by the crystal plane and does not allow for optimal light extraction
Solution Approach 1:
The patent changes the spatial parameters of laser irradiation by performing multiple scanning passes at different positions and depths within the sapphire substrate. This creates multiple modified regions with varying distances from the surface, which fundamentally alters the cleavage behavior to produce uneven side surfaces that improve light extraction efficiency
Solution Approach 2:
The laser irradiation process is segmented into multiple distinct scanning passes, each creating modified regions at different locations. The first scanning creates modified regions at a first spacing, while the second scanning creates modified regions at a second spacing (less than the first spacing), resulting in a segmented distribution of modified regions that enables controlled uneven side surface formation
2Reliability
If multiple modified regions are formed at different spacings through repeated laser scanning, then uneven side surfaces are formed to improve light extraction, but the manufacturing process becomes more complex
Solution Approach 1:
The laser beam is used to perform multiple functions: it creates modified regions for cleavage initiation, controls the spacing and distribution of these regions, and ultimately determines the side surface morphology. This multi-functionality reduces the need for additional processing steps or equipment, despite the complex outcome
Solution Approach 2:
The laser scanning is performed periodically with specific intervals and patterns. The first scanning establishes a baseline pattern of modified regions, and subsequent periodic scans at different positions create the uneven distribution. This periodic action with varying parameters achieves the complex side surface morphology through a systematic rather than random process
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 method increases light extraction efficiency by forming uneven side surfaces on the sapphire substrate, specifically for deep ultraviolet light, by creating a greater number of modified regions with varying spacings, which enhances the protrusions and reduces crack extension, leading to improved output and stability during cleavage.
Implementation Method 1
irradiating a laser beam into an interior of the sapphire substrate through the second surface side of the wafer
Implementation Method 2
a first irradiation process of scanning the laser beam along a first direction parallel to an a-axis direction of the sapphire substrate to form a plurality of first modified portions along the first direction in the interior of the sapphire substrate
Data Source
AI summary
In a method for manufacturing a light-emitting element, a second irradiation process includes forming a first modified region at a first distance from a second surface in a thickness direction of a sapphire substrate, forming a second modified region at a second distance from the second surface in the thickness direction, the second distance being less than the first distance, the second modified region being shifted in a first direction from the first modified region, and forming a third modified region at a third distance from the second surface in the thickness direction, the third distance being less than the second distance, the third modified region overlapping the first modified region in a top-view. In the thickness direction of the sapphire substrate, a greater number of modified regions that include second modified portions are formed than modified regions that include first modified portions.