Nano-Scale Hollow Optical Waveguides via SiGe Sacrificial Etching
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Solution Overview
Problem
The challenge lies in forming well-defined, nano-scale hollow optical waveguides on semiconductor substrates, as current technologies face difficulties in achieving densely populated structures with precise dimensions.
Innovation Solution
The solution involves a semiconductor waveguide structure with a non-planar top surface, featuring first planar and second curved top surface portions, where the hollow optical channel's inner surface is positioned below and above the planar surfaces, formed through a process involving silicon-on-insulator substrates, epitaxial growth, and selective etching of sacrificial silicon-germanium layers to create consistently sized nano-scale channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional fabrication methods are used to form optical waveguides, then manufacturing simplicity is maintained, but manufacturing precision deteriorates at nano-scale dimensions
Solution Approach 1:
The fabrication process is divided into distinct stages: forming sacrificial SiGe layers, depositing conformal silicon layers, and selective removal of SiGe. This segmentation allows each step to be optimized independently for precision while maintaining overall process manageability at the nano-scale
Solution Approach 2:
Sacrificial silicon-germanium layers are deposited and patterned in advance before the final waveguide structure is formed. This preliminary action establishes precise dimensional templates that guide subsequent conformal layer deposition, ensuring accurate nano-scale waveguide dimensions before the sacrificial material is removed
2Productivity
If hollow optical waveguides are formed with higher density, then productivity is improved, but manufacturing precision deteriorates due to difficulty in defining nano-scale structures
Solution Approach 1:
The conformal silicon layers automatically self-align to the sacrificial SiGe structures through conformal deposition, and the selective removal process self-defines the hollow channel positions. This self-service mechanism ensures precise waveguide definition even when multiple waveguides are densely packed, as each structure is defined by its own sacrificial template rather than requiring individual patterning
Solution Approach 2:
Multiple hollow optical waveguides are formed by nesting them within a common sacrificial SiGe layer structure. The sacrificial material serves as a master template that simultaneously defines multiple adjacent waveguides, enabling high-density integration while maintaining precise dimensional control through the unified patterning step
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 creation of densely populated, nano-scale hollow optical waveguides with precise dimensions, enhancing the integration of optical waveguide structures in semiconductor photonics and supporting advanced photonic integrated circuits.
Implementation Method 1
epitaxial growth
Implementation Method 2
selective etching of sacrificial silicon-germanium layers
Data Source
AI summary
A strip of sacrificial semiconductor material is formed on top of a non-sacrificial semiconductor material substrate layer. A conformal layer of the non-sacrificial semiconductor material is epitaxially grown to cover the substrate layer and the strip of sacrificial semiconductor material. An etch is performed to selectively remove the strip of sacrificial semiconductor material and leave a hollow channel surrounded by the conformal layer and the substrate layer. Using an anneal, the conformal layer and the substrate layer are reflowed to produce an optical waveguide structure including the hollow channel.