Lift-off Method for Optical Device Layer Transfer
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Solution Overview
Problem
The existing lift-off methods for optical device wafers face challenges in uniformly destroying the buffer layer, leading to irregular peeling of the epitaxy substrate, which affects the quality of optical devices due to uneven substrate surfaces and incomplete buffer layer decomposition.
Innovation Solution
A lift-off method involving a complex substrate formation, buffer layer destruction using a laser beam, and thermal distortion through heating and cooling to ensure uniform buffer layer destruction and successful peeling of the epitaxy substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a laser beam is irradiated from the rear side of the epitaxy substrate to destroy the buffer layer, then the buffer layer decomposition occurs, but the destruction is irregular and incomplete due to substrate unevenness and laser blocking
Solution Approach 1:
The patent applies preliminary action by joining the transfer substrate to the optical device layer before laser irradiation. This preliminary bonding ensures that even if the buffer layer is not completely destroyed by the laser, the subsequent peeling process can still succeed because the optical device layer is already secured to the transfer substrate. The complex substrate formation step prepares the structure in advance to compensate for potential incomplete buffer layer destruction.
Solution Approach 2:
The patent employs parameter changes by irradiating the laser beam from the rear side of the epitaxy substrate rather than from the front. This change in irradiation direction allows the laser to penetrate through the substrate and buffer layer more effectively, achieving more uniform buffer layer destruction. The wavelength selection (257 nm) is also optimized to match the absorption characteristics of the buffer layer materials.
2Ease of manufacture
If the buffer layer is destroyed unevenly in different areas, then complete peeling becomes difficult, but applying additional measures increases process complexity
Solution Approach 1:
The patent uses preliminary action by performing the complex substrate formation (joining transfer substrate to optical device layer) before the buffer layer destruction step. This preliminary bonding ensures that even if buffer layer destruction is uneven, the peeling process will succeed because the optical device layer is already firmly attached to the transfer substrate, eliminating the need for additional measures to handle incomplete destruction.
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 allows for the consistent and effective peeling of the epitaxy substrate, improving the quality of optical devices by ensuring complete buffer layer destruction and preventing degradation during the peeling process.
Implementation Method 1
irradiating a laser beam having a wavelength that penetrates the epitaxy substrate and is absorbed by the buffer layer from a rear side of the epitaxy substrate so as to destroy the buffer layer
Implementation Method 2
decomposition of GaN, INGaP, or AlGaN making up the buffer layer into Ga and N2 gas
Implementation Method 3
heats and cools the complex substrate to produce thermal distortion between the epitaxy substrate and the transfer substrate to which the optical device layer has been joined
Data Source
AI summary
A lift-off method transfers an optical device layer of an optical device wafer onto a transfer substrate. The optical device layer is stacked on a front face of an epitaxy substrate with a buffer layer provided therebetween. A complex substrate formation step forms a complex substrate by joining the transfer substrate to a front face of the optical device layer of the optical device wafer with an adhesive. A buffer layer destruction step irradiates a laser beam at a wavelength that penetrates the epitaxy substrate and is absorbed by the buffer layer from a rear side of the epitaxy substrate of the complex substrate so as to destroy the buffer layer. An optical device layer transfer step peels off the epitaxy substrate and transfers the optical device layer onto the transfer substrate.