Laser Diode Alignment Mark Recovery via InAsP Etching Stopper
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Solution Overview
Problem
In the manufacturing of laser diodes with diffraction gratings, alignment marks formed on semiconductor surfaces are often buried or eroded during subsequent regrowth and etching steps, making it difficult to maintain alignment accuracy for waveguide structure formation.
Innovation Solution
A method involving the growth of an active layer, a first InP layer, and a diffraction grating layer on a semiconductor substrate, with an alignment mark formed by etching the diffraction grating and InP layers, followed by the formation of a modified InAsP layer on the alignment mark's inner walls, which serves as an etching stopper to recover the alignment mark during subsequent etching steps, allowing for precise alignment of the waveguide structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an alignment mark is formed by etching a recess on the semiconductor layer surface, then the alignment mark can be initially formed for waveguide alignment, but the alignment mark is buried in regrowth and eroded in subsequent etching, making it difficult to recognize
Solution Approach 1:
The alignment mark is formed preliminarily on the semiconductor layer surface before regrowth, and its position is recorded. After regrowth buries the alignment mark, the pre-recorded position information enables recovery of the alignment mark by etching through the regrown layer at the predetermined position, thus resolving the recognition difficulty
Solution Approach 2:
The alignment mark is temporarily discarded (buried) during the regrowth process, then recovered by selective etching at the predetermined position after regrowth. This allows the alignment mark to survive the regrowth step and remain recognizable for subsequent waveguide formation
2Difficulty of detecting and measuring
If the alignment mark is formed using a SiO2 film, then the alignment mark remains observable after cladding layer growth, but the waveguide structure cannot be formed with the same material system
Solution Approach 1:
The alignment mark formation is extracted from the material system constraint by using a recess structure in the semiconductor layer itself rather than a foreign material layer. This allows the alignment mark to be formed, buried, and recovered within the same semiconductor material system, enabling both observability and material compatibility
3Manufacturing precision
If regrowth is performed to embed the diffraction grating, then the diffraction grating is properly embedded, but the alignment mark is buried and becomes unrecognizable
Solution Approach 1:
The alignment mark position is predetermined and recorded before regrowth. After regrowth embeds the diffraction grating, the pre-recorded position enables selective etching to recover the alignment mark through the regrown layer, maintaining visibility despite embedding
Solution Approach 2:
The alignment mark is temporarily discarded (buried) during regrowth to enable proper diffraction grating embedding, then recovered by selective etching at the predetermined position, allowing it to remain recognizable for waveguide alignment
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 ensures accurate recognition and maintenance of the alignment mark, enabling high-precision alignment and waveguide formation, even after regrowth and etching, thereby improving the manufacturing process for laser diodes with diffraction gratings.
Implementation Method 1
forming a modified layer containing InAsP, after removing the first etching mask, on an inner wall surface of the recess of the alignment mark by supplying a first source gas containing As and a second source gas containing P
Implementation Method 2
growing a second InP layer, after forming the modified layer, on the diffraction grating layer and on the alignment mark
Data Source
AI summary
Manufacturing a laser diode includes growing an active layer, a first InP layer, and a diffraction grating layer; forming an alignment mark having a recess by etching the diffraction grating layer and the first InP layer; forming a first etching mask; forming a diffraction grating in the diffraction grating layer using the first etching mask; forming a modified layer containing InAsP on a surface of the alignment mark recess by supplying a first source gas containing As and a second source gas containing P; growing a second InP layer on the diffraction grating layer and on the alignment mark; forming a second etching mask on the second InP layer; selectively etching the second InP layer embedded in the recess of the alignment mark through the second etching mask by using the modified layer serving as an etching stopper; and forming a waveguide structure using the alignment mark.