Fiber-Waveguide Coupler V-Groove Alignment Under Substrate Bow
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Solution Overview
Problem
Existing fabrication processes for fiber-to-waveguide couplers face challenges in achieving tight tolerances and alignment accuracy, particularly when thick claddings are required, due to issues like surface roughness, wafer bow, and particle contamination, which are not adequately addressed by methods such as wafer-to-wafer fusion bonding.
Innovation Solution
A method involving the deposition of a mask layer, an intermediate layer, and a stress compensation layer on a substrate, followed by precise etching to create a V-groove aligned with a waveguide structure, using materials like SiO2 and metals for stress compensation, to ensure accurate fiber alignment and reduce substrate bow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If wafer-to-wafer fusion bonding is used to integrate V-Groove with thick claddings, then bonding strength is improved, but surface roughness requirements become extremely strict (less than 0.5 nm) and manufacturing complexity increases
Solution Approach 1:
The patent introduces an intermediary layer between the substrate and the bonding interface. This intermediate layer acts as a buffer that reduces the stringent surface roughness requirements, allowing bonding to proceed with more relaxed surface preparation while maintaining bonding strength. The intermediary layer compensates for surface irregularities that would otherwise prevent successful fusion bonding.
Solution Approach 2:
The patent modifies the bonding interface parameters by introducing the intermediate layer, which changes the surface topology and roughness characteristics. This parameter change allows the bonding process to tolerate higher surface roughness values while still achieving adequate bonding strength, thereby reducing manufacturing complexity.
2Reliability
If thick claddings are required for photonic structures, then optical performance is improved, but alignment accuracy deteriorates due to substrate bow and surface roughness
Solution Approach 1:
The patent applies preliminary anti-action by depositing a stress compensation layer on the back side of the substrate before the bonding process. This layer pre-compensates for the substrate bow that would otherwise develop during or after bonding, thereby maintaining alignment accuracy between the V-groove and the waveguide core even with thick claddings present.
Solution Approach 2:
The stress compensation layer changes the mechanical parameters of the substrate by counteracting the stress-induced bow. This parameter change maintains the substrate flatness and alignment precision throughout the bonding process, enabling both thick claddings and high alignment accuracy to coexist.
3Manufacturing precision
If stress compensation layer is added to reduce substrate bow, then alignment accuracy is improved, but manufacturing steps increase
Solution Approach 1:
The patent merges the stress compensation layer deposition with the existing fabrication process flow. By integrating this step into the standard manufacturing sequence and using conventional deposition techniques, the additional manufacturing step does not significantly increase overall process complexity or time, while delivering substantial alignment accuracy improvements.
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
The method enhances alignment accuracy, reduces fabrication costs, and improves coupling efficiency by centering the fiber core with respect to the waveguide core, meeting higher alignment demands and enabling cost-effective production of fiber-waveguide couplers.
Implementation Method 1
depositing a stress compensation layer on a second surface on a back side of the substrate, wherein at least one of a material and a thickness of the stress compensation layer are selected for reducing a bow of the substrate
Implementation Method 2
anisotropic etching of a V-groove into the substrate at the opening marker of the mask layer
Implementation Method 3
bonding a first oxide layer on the intermediate layer
Data Source
AI summary
The present invention provides a method for manufacturing a fiber-waveguide coupler comprising depositing a mask layer on a first surface on a front side of a substrate, wherein the mask layer has at least one opening mark; depositing an intermediate layer on the mask layer; bonding a first oxide layer on the intermediate layer; depositing a stress compensation layer on a second surface on a back side of the substrate, wherein at least one of a material and a thickness of the stress compensation layer are selected for reducing a bow of the substrate; depositing a waveguide structure on the first oxide layer, wherein the waveguide structure has a core layer and a cladding layer, wherein the core layer has a predetermined width and a predetermined thickness and is aligned with the opening mark; and anisotropic etching of a V-groove into the substrate at the opening marker of the mask layer such that when a fiber having a predetermined size is placed inside the V-groove, a core of the fiber is centered with respect to the core layer of the waveguide structure. Further, the present invention provides a corresponding fiber-waveguide coupler, a further method for manufacturing a fiber-waveguide coupler as well as a corresponding further fiber-waveguide coupler.