Polysilicon Photonic Structures with Spatially Varying Optical Properties
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Solution Overview
Problem
The high cost and complexity of integrating different materials in optoelectronic integrated structures to achieve photonic devices with varying optical properties, such as signal detection and low loss waveguides, are significant challenges in current fabrication methods.
Innovation Solution
The use of polysilicon material with varying optical absorption properties in different regions of the optoelectronic structure allows for the formation of both low loss waveguides and high absorption signal detectors, leveraging the inherent properties of polysilicon for transistor gates and defect-state photodetectors, while maintaining fabrication at the same physical level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If different materials are used in different regions to achieve photonic devices with varying optical properties, then the optical performance is improved, but the fabrication complexity and cost increase significantly
Solution Approach 1:
The patent changes the optical parameters of polysilicon by controlling its crystallization conditions (temperature, time, atmosphere) to achieve different absorption coefficients in different regions. By annealing polysilicon at different temperatures or for different durations, regions can be tuned to have either high absorption (for photodetectors) or low absorption (for waveguides), all using the same base material system
Solution Approach 2:
The polysilicon material serves multiple functions within the same integrated circuit: it forms transistor gates, waveguide cores, and photodetector regions. This multi-functionality is achieved by spatially varying the crystallization parameters of the polysilicon to create different optical properties in different areas, eliminating the need for separate material layers for each function
2Adaptability or versatility
If different materials are integrated in different regions, then photonic devices with different optical properties are achieved, but the fabrication cost increases
Solution Approach 1:
The patent employs parameter changes in the polysilicon crystallization process (temperature, time, atmospheric conditions) to create spatial variations in optical absorption. This allows a single material deposition step followed by selective annealing to produce regions with tailored optical properties, avoiding the need for multiple material depositions and reducing fabrication cost
Solution Approach 2:
The patent applies local quality by creating spatially varying optical properties within the polysilicon material through localized annealing treatments. Specific regions are subjected to different thermal histories to achieve desired absorption characteristics, allowing high absorption in photodetector regions and low absorption in waveguide regions while using the same base material
3Adaptability or versatility
If polysilicon is used for transistor gates, then CMOS compatibility is achieved, but optical absorption is high which is undesirable for waveguides
Solution Approach 1:
The patent applies local quality by creating spatially varying optical properties within the polysilicon material through localized annealing treatments. Specific regions are subjected to different thermal histories to achieve desired absorption characteristics, allowing high absorption in photodetector regions and low absorption in waveguide regions while using the same base material
Solution Approach 2:
The patent segments the polysilicon material into regions with different crystallization states. The transistor gate region maintains as-grown or lightly-annealed polysilicon for CMOS compatibility, while waveguide regions undergo extended high-temperature annealing to reduce absorption, and photodetector regions are annealed to achieve high absorption for detection functionality
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 reduces fabrication complexity and cost by utilizing polysilicon for both low loss waveguides and high absorption photodetectors in the same structure, enhancing signal propagation and detection capabilities.
Implementation Method 1
polysilicon material with different absorption losses in different regions of an optoelectronic integrated structure such that low loss waveguides and high absorption signal detector photodetector can be formed
Data Source
AI summary
Method and structural embodiments are described which provide an integrated structure using polysilicon material having different optical properties in different regions of the structure.