Laser Scribing Sapphire Substrates for LED Chips
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Solution Overview
Problem
Conventional laser scribing methods for semiconductor light emitting elements, particularly those using high-energy laser beams on sapphire substrates, often damage semiconductor structures, leading to reduced yield and efficiency in manufacturing.
Innovation Solution
The method involves irradiating the substrate with a series of laser pulses at predetermined intervals and energies, where the second pulse has a shorter time interval and slightly lower energy than the first pulse, to reduce damage and enhance crack propagation while maintaining processing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a high-energy laser beam is used to cleave the sapphire substrate, then the cleaving efficiency is improved, but the semiconductor structures are damaged
Solution Approach 1:
The laser irradiation process is segmented into multiple pulses with different time intervals and energy levels. The first pulse (longer time interval, lower energy) initiates crack propagation, while the second pulse (shorter time interval, higher energy) enhances crack extension. This segmentation allows efficient cleaving while preventing excessive energy damage to semiconductor structures.
Solution Approach 2:
The method employs periodic laser pulsing with specific time intervals (first time interval between first pulses, second time interval between second pulses). This periodic action with controlled timing allows the substrate to respond to each pulse appropriately, enabling crack propagation without causing damage to the semiconductor layers through continuous high-energy exposure.
2Manufacturing precision
If the laser pulse energy is increased to improve crack propagation, then the cleaving effectiveness is improved, but the damage to semiconductor layers increases
Solution Approach 1:
The method changes laser parameters (energy, time interval) between different pulses. The first pulse uses a first energy level and first time interval, while the second pulse uses a second energy level and second time interval. This parameter optimization ensures effective crack propagation while minimizing damage to semiconductor structures through controlled energy delivery.
Solution Approach 2:
The first laser pulse performs preliminary action by initiating crack propagation at a lower energy level. This preliminary cracking creates pathways that the second, higher-energy pulse can then extend more effectively. This staged approach prevents the need for excessive energy in a single pulse, thereby protecting semiconductor structures from damage.
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 approach reduces the intensity of each pulse, minimizing damage to semiconductor layers and improving yield by effectively propagating cracks for efficient cleaving of semiconductor light emitting element chips.
Implementation Method 1
irradiating an inner portion of a substrate of the wafer at a predetermined depth in a thickness direction a plurality of times with laser pulses
Implementation Method 2
irradiating the substrate with a series of laser pulses at predetermined intervals and energies, where the second pulse has a shorter time interval and slightly lower energy than the first pulse, to reduce damage and enhance crack propagation
Data Source
Figure 1
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AI summary
A method includes preparing a wafer including a substrate and a semiconductor structure, and irradiating an inner portion of a substrate at a predetermined depth in a thickness direction a plurality of times with laser pulses at a first time interval and a predetermined distance interval between irradiations. Each irradiation performed at the first time intervals in the step of irradiating the substrate with laser pulses includes irradiating the substrate at a first focal position in the thickness direction with a first laser pulse having a first pulse-energy; and after irradiating with the first laser pulse, irradiating the substrate with a second laser pulse performed after a second time interval, the second time interval being shorter than the first time interval and being in a range of 3 ps to 900 ps, and the second laser pulse having a second pulse-energy 0.5 to 1.5 times the first pulse-energy.