Mixed Silicon-Silicon Nitride Waveguides Without Substrate Flipping
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Solution Overview
Problem
Current processes for fabricating photonic components with mixed layers of silicon and silicon nitride waveguides are complex and lack a simple method for chemical-mechanical polishing, especially when a thick silicon-nitride layer covers most of the substrate, making it difficult to integrate these components effectively.
Innovation Solution
A process is developed to fabricate a mixed layer by structuring a silicon-on-insulator stack, using chemical-mechanical polishing to planarize the layer, and depositing silicon nitride to form waveguides, allowing for the integration of silicon and silicon nitride waveguides in the same layer without flipping the substrate, thereby simplifying the fabrication and increasing integration density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a thick silicon-nitride layer is deposited to form waveguides, then the waveguide structure is achieved, but chemical-mechanical polishing cannot effectively remove the layer without uncovering the subjacent silicon oxide layer
Solution Approach 1:
A thin silicon-nitride stop liner is deposited beforehand on the silicon oxide layer before depositing the thick silicon-nitride waveguide layer. This preliminary layer acts as a stopping point for the chemical-mechanical polishing process, preventing over-polishing and eliminating the need to flip the substrate to access the waveguide cores.
2Adaptability or versatility
If three separate layers are stacked to produce silicon waveguides, silicon-nitride waveguides, and III-V material, then each waveguide type can be fabricated, but the fabrication process becomes complex and integration density decreases
Solution Approach 1:
The patent combines multiple waveguide fabrication steps into a single integrated process. Silicon waveguides and silicon-nitride waveguides are fabricated in the same layer using the same substrate, eliminating the need for separate layer stacking and reducing fabrication complexity while maintaining material versatility.
Solution Approach 2:
The silicon-on-insulator substrate serves multiple functions: it provides the substrate for both silicon and silicon-nitride waveguides, acts as a mechanical support, and enables planarization through its silicon oxide layer. This multi-functional approach reduces the number of separate components needed.
3Ease of manufacture
If the substrate is flipped to access the exterior face for polishing, then the thick silicon-nitride layer can be removed, but the fabrication process becomes more complex and time-consuming
Solution Approach 1:
The stop liner is deposited in advance on the exterior face before the thick silicon-nitride layer is formed. This allows the chemical-mechanical polishing to be performed from the same face without substrate flipping, saving time and simplifying the fabrication process while maintaining precise control over the polishing depth.
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 process simplifies the fabrication of photonic components, improves integration density, and allows for precise positioning of waveguide cores, enabling efficient optical coupling between silicon and silicon nitride waveguides within the same layer, enhancing the performance and properties of photonic components like semiconductor laser sources.
Implementation Method 1
chemical-mechanical polishing to planarize the layer
Implementation Method 2
depositing silicon nitride to form waveguides
Data Source
AI summary
A fabricating process may include: producing a trench, in an encapsulated-silicon layer, in the location where a silicon-nitride core of the waveguide must be produced; then depositing a silicon-nitride layer on the encapsulated-silicon layer, the thickness of the deposited silicon-nitride layer being sufficient to completely fill the trench; then removing the silicon nitride situated outside of the trench to uncover an upper face with which the trench filled with silicon nitride is flush; then depositing a dielectric layer that covers the uncovered upper face in order to finalize the encapsulation of the silicon-nitride core and thus to obtain a mixed layer containing both the silicon and silicon-nitride cores encapsulated in dielectric.