Suspended Silicon Photonics Fabrication via Metal Etch Channels
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Solution Overview
Problem
Conventional silicon integrated photonic systems face challenges in fabricating photonic devices with improved methods that enhance optical power isolation and device integration, particularly in silicon-on-insulator (SOI) technology.
Innovation Solution
A method involving the formation of metal-dielectric structures on a semiconductor substrate, followed by selective metal etching to create photonic devices such as suspended rib waveguides, grating couplers, and phase modulators, with additional material injection to fill etched spaces, utilizing CMOS processes for hybrid electronic-photonic device fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SOI technology is used for fabrication, then optical power isolation is achieved through BOX layer, but device integration and fabrication flexibility are limited
Solution Approach 1:
The patent segments the fabrication process into distinct metal layer formation steps, where each metal layer can be independently patterned and etched. This allows different regions of the device to have different metal configurations, enabling both optical isolation in photonic regions and electrical connectivity in electronic regions, thus resolving the contradiction between isolation and integration
Solution Approach 2:
The metal layers serve multiple functions: they provide electrical interconnects for electronic devices, form etch channels for defining photonic device regions, and create suspended structures for optical waveguides. This multi-functionality allows a single fabrication approach to achieve both optical isolation and device integration
2Reliability
If dedicated photonic processes are used, then optical device performance is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges electronic and photonic device fabrication into a single integrated process using standard CMOS-compatible steps. Metal layers are formed and patterned using the same deposition and lithography tools used for electronic interconnects, eliminating the need for separate photonic fabrication lines while maintaining optical device performance
Solution Approach 2:
The metal layers automatically serve dual purposes: they provide electrical connectivity where needed and define photonic device boundaries where etched away. The etch channels self-organize to remove metal from photonic regions while preserving it in electronic regions, reducing the need for additional process steps
3Reliability
If metal layers are removed to form photonic devices, then optical power isolation is enhanced, but structural support may be compromised
Solution Approach 1:
The patent applies different metal layer configurations to different regions of the device. In photonic regions, metal layers are completely removed to achieve optical isolation. In electronic regions and support areas, metal layers are retained to provide structural support and electrical connectivity. This local differentiation resolves the contradiction between isolation and strength
Data Source
Figure 1A~3B
Figure 4A~4C
Figure 4D~4E
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.