Suspended Silicon Photonic Structures Using Metal Etch Channels
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Solution Overview
Problem
Conventional silicon integrated photonic systems face challenges in fabricating efficient photonic devices due to limitations in existing methods, such as silicon-on-insulator technology, which struggle with optical power leakage and device precision.
Innovation Solution
A method involving the formation of metal-dielectric structures on a semiconductor substrate, where metal layers are etched to create photonic devices like suspended rib waveguides and grating couplers, with dielectric layers and materials injected to optimize optical signal propagation and phase modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon-on-insulator (SOI) technology is used for fabrication, then optical power leakage is prevented, but device precision and fabrication efficiency are limited
Solution Approach 1:
The patent changes the fabrication approach by using metal layer etching with controlled etch channels instead of conventional SOI processing. This involves changing parameters such as metal layer thickness, etch channel dimensions, and etch selectivity to achieve precise photonic device fabrication while maintaining optical power confinement.
Solution Approach 2:
The patent replaces the mechanical SOI wafer structure with a metal-dielectric stack that uses chemical etching processes. Instead of relying on the physical BOX layer separation, the invention uses etch channels formed through metal layers to define photonic structures, substituting mechanical isolation with chemical process control.
2Reliability
If conventional SOI fabrication methods are used, then optical isolation is achieved, but fabrication complexity and time increase
Solution Approach 1:
The patent makes the metal layers serve multiple functions: they act as both structural components and etch channel definitions. The same metal layers that form part of the photonic device structure also define the pathways for etchant flow, eliminating the need for separate isolation structures and reducing fabrication steps.
Solution Approach 2:
The patent segments the metal layers into specific patterns that create etch channels, allowing selective removal of metal in controlled pathways. This segmentation enables the etchant to flow through defined channels to remove metal selectively, achieving precise device formation without requiring complete wafer-level isolation structures.
3Manufacturing precision
If metal layers are completely removed to form photonic devices, then device precision is improved, but metal residue remains causing defects
Solution Approach 1:
The patent introduces etch channels as intermediary pathways that facilitate complete metal removal. These channels act as conduits for the etchant to reach and remove metal layers systematically, preventing metal residue by ensuring complete etch penetration through the structured channels rather than relying on bulk removal processes.
Solution Approach 2:
The patent uses fluid dynamics principles by allowing liquid etchant to flow through the etch channels formed in the metal layers. The etchant flows hydraulically through the channels, ensuring complete penetration and removal of metal layers without leaving residue, leveraging fluid flow to achieve complete material removal.
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 enables the fabrication of precise photonic devices with improved optical signal handling and phase control, enhancing the performance of photonic systems by minimizing metal residue and optimizing dielectric structures for efficient light propagation and modulation.
Implementation Method 1
when the structure is exposed to a metal etch, the metal etch removes the metal from the exterior surface of the structure and flows through the etch channel to fully etch the metal layers
Implementation Method 2
Waveguides and other devices are formed within the thin silicon layer since the silicon has a high index contrast with the surrounding oxide
Implementation Method 3
The optical signal propagating through the first waveguide is received by the doped region of the semiconductor substrate through the second waveguide
Data Source
AI summary
A method of fabricating a photonic device includes in part, forming a multitude of metal and dielectric layers over a semiconductor substrate to form a structure. The metal layers form a continuous metal trace that characterize an etch channel. At least one of the metal layers extends towards an exterior surface of the structure such that when the structure is exposed to a metal etch, the metal etch removes the metal from the exterior surface of the structure and flows through the etch channel to fully etch the metal layers. The metal etch leaves behind a dielectric structure characterizing a photonic device. The photonic device may be a suspended rib waveguide, a suspended channel waveguide, a grating coupler, an interlayer coupler, a photodetector, a phase modulator, an edge coupler, and the like. A photonics system may include one or more of such devices.