Sapphire Substrate Laser Splitting for LED Yield
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Solution Overview
Problem
Current methods for manufacturing semiconductor elements using sapphire substrates face challenges such as damage to the semiconductor layer and reduced optical output due to multiple laser scans, which increase the surface area of modified regions, leading to light loss and decreased yield.
Innovation Solution
A method involving a first and second laser scanning step, where the second scanning occurs before voids are produced in the sapphire substrate, promoting crack development while minimizing damage to the semiconductor layer, and maintaining the focal position close to the substrate to reduce light loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple laser scans are performed at different depths to improve wafer splitting, then splitting efficiency is improved, but semiconductor layer damage increases and optical output decreases
Solution Approach 1:
The patent performs a first laser scan to create a modified region in the sapphire substrate, then performs a second laser scan along the same path before voids form in the modified region. This preliminary action of creating the modified region first enables subsequent crack propagation without requiring additional deep scans that would damage the semiconductor layer, thus resolving the contradiction between splitting efficiency and layer integrity
Solution Approach 2:
The patent employs periodic laser scanning where the laser beam scans the same portion multiple times with specific time intervals. The second scanning is performed periodically after the first scanning but before void formation completes, creating controlled stress accumulation that promotes clean splitting without excessive energy input that would damage the semiconductor layer
2Productivity
If laser pulse energy is increased to improve splitting, then wafer separation is improved, but semiconductor layer damage increases
Solution Approach 1:
The first laser scan creates a modified region with accumulated stress at lower energy levels. The second scan then utilizes this pre-conditioned state to promote crack propagation with minimal additional energy, avoiding the need for high pulse energy that would directly damage the semiconductor layer while still achieving effective separation
3Productivity
If the surface area of the modified region is increased to improve splitting, then wafer division is improved, but light extraction efficiency decreases
Solution Approach 1:
The first laser scan creates the modified region with controlled dimensions. The second scan follows the same path to promote crack propagation along the existing modified region boundaries rather than expanding the modified region area. This prevents excessive surface area increase that would cause light scattering and absorption, while still achieving effective wafer division through controlled cracking
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 improves wafer splitting efficiency, reduces semiconductor layer damage, and maintains optical output by minimizing the width of machining marks, resulting in higher yield and better light extraction from semiconductor elements.
Implementation Method 1
performing a first scanning of a portion of the sapphire substrate in which a laser beam is irradiated into an interior of the sapphire substrate
Implementation Method 2
produce cracks or the like from the modified region, and split along these lines
Data Source
AI summary
A method for manufacturing a semiconductor element includes providing a wafer having a sapphire substrate and a semiconductor stacked body disposed on the sapphire substrate, performing a first scanning of a portion of the sapphire substrate in which a laser beam is irradiated into an interior of the sapphire substrate, performing a second scanning of the portion of the sapphire substrate in which a laser beam is irradiated into the interior of the sapphire substrate, the second scanning occurring after the first scanning and before a void is produced in the interior of the sapphire substrate irradiated with the laser beam in the first scanning, and separating the wafer into a plurality of semiconductor elements.