Crystalline-Amorphous Silicon Photonic Module Coupling Without Voids
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Solution Overview
Problem
Conventional photonic modules face issues such as voids at the amorphous-crystalline interface due to non-uniform growth-fronts during fabrication, leading to optical insertion losses and polarization-dependent performance due to non-ideal chemical mechanical polishing (CMP) processes.
Innovation Solution
A photonic module design featuring crystalline and amorphous silicon waveguides with a coupling section that eliminates cavity etching and CMP, utilizing etching processes to form tapered portions for efficient light coupling across a broad wavelength range, reducing optical losses with silicon dioxide claddings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PECVD is performed in a cavity to form amorphous silicon waveguide, then the waveguide can be fabricated, but voids are created at the growth-front interface leading to optical insertion losses
Solution Approach 1:
The patent extracts and eliminates the problematic cavity structure from the fabrication process. Instead of depositing amorphous silicon into a cavity formed by etching, the invention uses a planar deposition process where amorphous silicon is deposited on a flat surface, thereby removing the source of void formation at growth-front interfaces while still enabling waveguide fabrication.
Solution Approach 2:
The patent applies preliminary planarization through chemical mechanical polishing (CMP) before the PECVD deposition process. This preliminary action creates a flat substrate surface, ensuring uniform amorphous silicon deposition and preventing void formation at interfaces, thereby improving optical transmission reliability before the actual waveguide formation occurs.
2Manufacturing precision
If CMP is used to achieve uniform topography, then surface flatness can be obtained, but non-ideal CMP causes dishing and step topology leading to insertion loss and higher-order mode excitation
Solution Approach 1:
The patent modifies the deposition parameters and process sequence to reduce reliance on aggressive CMP. By controlling the PECVD deposition conditions and using a multi-layer structure with different materials, the invention achieves the necessary surface flatness and waveguide dimensions without requiring aggressive CMP that causes dishing, thereby maintaining optical performance.
Solution Approach 2:
The patent uses composite material structures combining amorphous silicon waveguides with different cladding and substrate materials. This composite approach allows for stress management and surface profile control that reduces dishing effects, maintaining surface flatness and preventing higher-order mode excitation while achieving the required manufacturing precision.
3Quantity of substance
If amorphous silicon is deposited in a cavity with vertical and horizontal growth-fronts, then the cavity can be filled, but diagonal voids are created acting as scattering centres
Solution Approach 1:
The patent extracts and eliminates the cavity structure that causes diagonal void formation. By transitioning from cavity-based deposition to planar deposition on a flat surface, the invention removes the geometric conditions that create scattering centres while still achieving complete amorphous silicon coverage for waveguide formation.
Solution Approach 2:
The patent changes the deposition geometry from three-dimensional cavity filling to two-dimensional planar deposition. This dimensional change eliminates the diagonal growth-front intersection that creates voids, transforming the process into a controlled lateral expansion that covers the substrate without forming scattering centres.
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
Enhances coupling and transmission properties by eliminating voids and reducing optical leakage, achieving efficient and polarization-independent light transfer.
Implementation Method 1
the coupling section is configured to couple light between the first waveguide and the second waveguide
Implementation Method 2
by spatially compressing the optical modes propagating through the at least one of the waveguides, the tapered portion induces an efficient transfer of optical power between the waveguides
Implementation Method 3
reducing optical losses with silicon dioxide claddings
Data Source
AI summary
A photonic module, comprising a first waveguide; a second waveguide, disposed on an opposing side of the first waveguide to a substrate; and, a coupling section. One of the first waveguide and the second waveguide is formed of crystalline silicon. The other of the first waveguide and the second waveguide is formed of amorphous silicon. The coupling section is configured to couple light between the first waveguide and the second waveguide. Such a silicon photonic module has enhanced coupling and transmission properties in contrast to conventional modules.