Semiconductor Laser Grating Defect Reduction via Asymmetric Mold Recesses
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Solution Overview
Problem
The nano-imprint technique for manufacturing semiconductor lasers can result in defects in the diffraction grating due to trapped gas bubbles between the resin part and the mold, leading to incomplete transfer of the grating pattern and subsequent defects in the semiconductor layer.
Innovation Solution
A method involving a mold with recesses having end portions and a middle portion, where the depth of the end portions is greater than the middle portion, is used to trap gas bubbles at the end portions, allowing for their easy removal, and the process is performed in a reduced-pressure atmosphere to minimize defects, with additional steps for forming a resin pattern and etching to ensure uniformity and accuracy of the diffraction grating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the mold pattern surface is pressed against the resin part to transfer the diffraction grating pattern, then the manufacturing cost is reduced and the grating pattern is formed, but gas bubbles become trapped between the resin part and the recesses in the pattern surface, causing defects in the diffraction grating
Solution Approach 1:
The patent applies preliminary action by creating a reduced-pressure atmosphere before pressing the mold pattern surface against the resin part. This preliminary vacuum treatment removes air from the interface between the mold and resin, preventing gas bubble entrapment during the subsequent pressing operation. The vacuum treatment is performed before the actual pattern transfer, ensuring that when the mold contacts the resin, no air pockets are present to cause defects.
Solution Approach 2:
The patent creates an inert environment by using a reduced-pressure atmosphere (vacuum) during the pattern transfer process. This vacuum environment replaces the normal air atmosphere, eliminating the presence of air molecules that would otherwise form gas bubbles at the interface between the mold recesses and resin part. The inert vacuum environment ensures clean pattern transfer without contamination from air pockets.
2Device complexity
If the recesses in the mold have uniform depth, then the manufacturing process is simpler, but gas bubbles cannot be effectively trapped and removed, leading to defects in the diffraction grating
Solution Approach 1:
The patent applies asymmetry by designing the mold recesses with non-uniform depth profiles. Specifically, the recesses have deeper regions at certain locations and shallower regions at others, creating an asymmetric depth distribution. This asymmetric structure causes gas bubbles to migrate toward the shallower regions during the pressing process, where they can be effectively removed. The asymmetric recess design transforms the uniform mold structure into a functional gas-trapping structure that improves pattern transfer reliability.
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 effectively reduces defects in the diffraction grating by allowing trapped gas bubbles to move to the end portions, which can be easily removed, resulting in a more accurate and uniform grating pattern on the semiconductor laser, enhancing the manufacturing process.
Implementation Method 1
a method involving a mold with recesses having end portions and a middle portion, where the depth of the end portions is greater than the middle portion, is used to trap gas bubbles at the end portions, allowing for their easy removal, and the process is performed in a reduced-pressure atmosphere to minimize defects
Data Source
AI summary
A method for manufacturing a semiconductor laser includes the steps of preparing a mold with a pattern surface having recesses, forming a stacked semiconductor layer including a grating layer, forming a resin part on the grating layer, forming a resin pattern portion on the resin part, forming a diffraction grating by etching the grating layer using the resin part as a mask, and forming a mesa-structure on the stacked semiconductor layer. Each of the recesses includes two end portions and a middle portion between the two end portions. A depth of at least one of the two end portions from the pattern surface is greater than that of the middle portion. The step of forming the mesa-structure includes the step of etching the stacked semiconductor layer so as to remove end portions of the diffraction grating in a direction orthogonal to a periodic direction thereof.