Semiconductor Buried Grating Fabrication via Hybrid Etching
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Solution Overview
Problem
Existing methods for fabricating semiconductor gratings in DBR or DFB lasers face challenges in achieving high-quality grating profiles with precise control over pitch size, duty cycle, line height, and crystalline properties, leading to suboptimal laser spectral performance and potential contamination issues with conventional etch mask compositions.
Innovation Solution
A hybrid-etching process combining reactive ion etching (RIE) and chemical wet etching is employed, with a grating layer placement between the etch mask and etch stop layers to control selective wet etching, and the use of aluminum-free materials for the etch stop and mask layers to minimize contamination, followed by regrowth of the cladding layer to form a high-quality grating profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etch mask compositions are used, then the etching process can be performed, but contamination issues arise and grating profile quality deteriorates
Solution Approach 1:
The patent changes the material composition parameters of the etch mask layer, specifically using aluminum-free materials (such as GaInP) instead of conventional aluminum-containing materials. This parameter change eliminates contamination issues while maintaining effective etching performance and improving grating profile quality.
Solution Approach 2:
The patent employs composite material structures with specific layer compositions - using GaInP etch mask layers combined with GaAs grating layers. This composite approach enables selective etching while preventing contamination, achieving both high manufacturing precision and reduced harmful factors.
2Manufacturing precision
If selective wet etching is used to form grating profile, then precise pitch size and duty cycle control are achieved, but etch stop layer composition must be carefully controlled to prevent contamination
Solution Approach 1:
The patent changes the material composition of the etch stop layer to aluminum-free materials (GaInP), which maintains the selective etching capability for precise pitch and duty cycle control while eliminating contamination from aluminum-containing etch stop layers.
Solution Approach 2:
The etch stop layer acts as an intermediary between the grating layer and the substrate, providing controlled etching termination while preventing contamination. The aluminum-free composition of this intermediary layer resolves the contradiction between precision control and contamination prevention.
3Manufacturing precision
If hybrid-etching process (RIE + wet etching) is employed, then grating profile quality is enhanced, but process complexity increases
Solution Approach 1:
The patent segments the etching process into two distinct stages: RIE for initial grating formation and wet etching for profile refinement. This segmentation allows each process to optimize for its specific function, achieving high grating profile quality despite increased overall process complexity.
Solution Approach 2:
The hybrid-etching process maintains continuous useful action by seamlessly transitioning from RIE to wet etching, where each process builds upon the previous one to progressively improve the grating profile, justifying the increased complexity through superior results.
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 results in improved laser spectral performance with enhanced grating profile quality, reduced contamination, and increased reliability of semiconductor lasers, capable of producing single-frequency, single-lateral-mode output with high power, such as 700 mW at 1060 nm wavelength.
Implementation Method 1
The photoresist layer is exposed to UV light to form a photoresist grating pattern
Implementation Method 2
transferring the grating pattern to the grating layer via dry etching
Implementation Method 3
A hybrid-etching process combining reactive ion etching (RIE) and chemical wet etching is employed
Implementation Method 4
selectively wet etching the grating layer to form the grating profile in the grating layer
Implementation Method 5
forming a photoresist grating pattern in the photoresist layer through a holography system
Data Source
AI summary
Methods for forming grating profiles in semiconductor laser structures comprise the steps of providing a semiconductor wafer comprising a wafer substrate, an etch stop layer disposed over the wafer substrate, a grating layer disposed over the etch stop layer, an etch mask layer disposed over the grating layer, and a photoresist layer disposed over the etch mask layer, forming a photoresist grating pattern, transferring the photoresist grating pattern into the grating layers via dry etching, and removing the photoresist layer, selectively wet etching the grating layer to form the grating profile in the grating layer. The placement of the grating layer between the etch mask and etch stop layers controls the selective wet etching step. The method also comprises removing the etch mask layer via selective wet etching without altering the grating profile, and regrowing an upper cladding layer to produce the semiconductor laser structure.