Semiconductor Optical Waveguide Cavity Structure
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Solution Overview
Problem
The performance of semiconductor structures using silicon-on-insulator materials in existing technologies is poor due to limited light confinement and high light wave loss, primarily because of the small refractive index difference between the optical waveguide layer and the surrounding dielectric layers, leading to inefficient light transmission.
Innovation Solution
A semiconductor structure is developed with a cavity formed between the optical waveguide layer and a first dielectric layer, where the cavity has a refractive index less than the optical waveguide layer and silicon dioxide, enhancing total reflection and light wave transmission efficiency. This is achieved by removing a sacrificial layer and sealing the cavity with a second dielectric layer, using materials like SiOx, SiNx, and SiNCO, and employing a plasma-enhanced chemical vapor deposition method for the second dielectric layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional optical waveguide structure with dielectric layers is used, then the structure is simple to manufacture, but the light confinement ability is poor and light wave loss is high
Solution Approach 1:
The patent changes the refractive index parameter by introducing a cavity (air gap) with refractive index close to 1, which is significantly lower than the optical waveguide layer material. This parameter change enhances the refractive index contrast, improving light confinement ability and reducing light wave loss in the waveguide structure.
Solution Approach 2:
The patent segments the continuous dielectric layer into two separate parts: a first dielectric layer below the optical waveguide layer and a second dielectric layer above it, with a cavity in between. This segmentation creates the air gap that provides the low refractive index environment needed for better light confinement while maintaining structural integrity.
2Reliability
If the refractive index difference between optical waveguide layer and surrounding dielectric layers is increased, then light transmission efficiency is improved, but manufacturing precision requirements are increased
Solution Approach 1:
The patent uses a sacrificial layer as an intermediary material that is deposited on the optical waveguide layer, then planarized to form a flat top surface. This sacrificial layer serves as a template for subsequent cavity formation, allowing precise control of cavity dimensions and position, thereby reducing manufacturing precision requirements while achieving the desired refractive index contrast.
Solution Approach 2:
The patent performs preliminary actions by first forming the sacrificial layer and planarizing its top surface before removing it to create the cavity. This preliminary preparation ensures that when the cavity is formed, it has the desired geometry and position, making the overall manufacturing process more controllable and precise.
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
The structure improves light wave transmission efficiency by increasing the refractive index difference, leading to better total reflection and enhanced performance of the semiconductor structure.
Implementation Method 1
The transmission principle of the optical waveguide is that the total reflection of electromagnetic waves on an interface of media with different refractive indexes causes light waves to be limited and propagate in the wave guide and a limited area around it
Implementation Method 2
employing a plasma-enhanced chemical vapor deposition method for the second dielectric layer
Data Source
AI summary
A semiconductor structure and a fabrication method are provided. The semiconductor structure includes: a base substrate, an optical waveguide layer over the base substrate; a first dielectric layer over the base substrate; a cavity between the first dielectric layer and the optical waveguide layer; and a second dielectric layer on the first dielectric layer and the optical waveguide layer. The cavity is located on sidewall surfaces of the optical waveguide layer and has a bottom coplanar with a bottom of the optical waveguide layer. The second dielectric layer is located on a top of the cavity and seals the cavity.