Vertical Optical Interconnect for Thick BEOL Photonic Integration
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Solution Overview
Problem
Existing BEOL-compatible integration approaches for optoelectronic devices are limited by device thickness, leading to high series resistances, modal losses, and increased epitaxial effort, which restrict the integration of photonic components with larger thicknesses.
Innovation Solution
An integrated optoelectronic device with an optical interconnect structure that includes a vertical stack of optically coupled waveguide elements made of a first dielectric material embedded in a second dielectric material, allowing for efficient optical coupling over large vertical distances, up to 10µm or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If photonic components with larger thicknesses are integrated using existing BEOL-compatible approaches, then the integration of active photonic components is enabled, but high series resistances and modal losses occur
Solution Approach 1:
The patent introduces an optical interconnect structure as an intermediary between the FEOL waveguide and the BEOL photonic component. This structure includes a vertical stack of waveguide elements made of dielectric material with higher refractive index than the embedding medium, enabling efficient optical coupling over large vertical distances without the harmful electrical connections that cause series resistance and modal losses
Solution Approach 2:
The patent transitions from planar optical coupling to vertical three-dimensional coupling by implementing a vertical stack of waveguide elements. This vertical arrangement allows the optical interconnect to bridge large vertical distances between the FEOL waveguide and the BEOL photonic component, enabling thick photonic component integration while maintaining low loss through the vertical optical path
2Adaptability or versatility
If photonic components with larger thicknesses are integrated, then design options for active and passive photonic components are expanded, but device thickness limitation restricts integration
Solution Approach 1:
The patent implements a vertical stack of waveguide elements that extend in the vertical dimension, enabling the optical interconnect to span large vertical distances (up to 10 µm or more) between the FEOL waveguide and the BEOL photonic component. This vertical dimensionality change allows integration of thick photonic components with enhanced design options
Solution Approach 2:
The optical interconnect structure uses composite material construction with waveguide elements made of dielectric material having higher refractive index than the embedding dielectric material. This composite structure enables efficient optical coupling over the large vertical distance while supporting the integration of photonic components with larger thicknesses and diverse material compositions
3Length of stationary object
If optical coupling over large vertical distances is achieved, then integration of thick photonic components is enabled, but existing approaches are limited to small vertical gaps
Solution Approach 1:
The patent employs a vertical stack of waveguide elements arranged in the vertical dimension, enabling optical coupling over large vertical distances (up to 10 µm or more). This vertical arrangement maintains optical coupling efficiency by confining and guiding light through the vertical path, unlike conventional lateral coupling approaches limited to small gaps
Solution Approach 2:
The patent changes the refractive index parameter by using dielectric material for the waveguide elements that has a higher refractive index than the embedding dielectric material. This parameter change enhances optical confinement and coupling efficiency over the large vertical distance, enabling reliable optical interconnection despite the extended vertical gap
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 solution enables the integration of photonic components with larger thicknesses, such as III-V semiconductor lasers, while reducing series resistances and modal losses, thereby expanding design options for active and passive photonic components.
Implementation Method 1
an optical interconnect structure arranged and configured for optically coupling radiation from the BEOL coupling section into the FEOL coupling section
Implementation Method 2
a vertical stack of optically coupled waveguide elements made of a first dielectric material, which each are embedded in a second dielectric material and which in a desired wavelength range have an index of refraction of a higher value than the embedding second dielectric material
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3C
AI summary
An integrated optoelectronic device (100) comprises a substrate (102) with a silicon layer (104) that comprises one or more electronic components. An interconnect stack (114) is arranged on the substrate (102) and comprising a plurality of metal levels (M1, M2, M3). An optical waveguide, herein FEOL wave-guide (130), on the substrate (102) has an optical FEOL coupling section (130.1). A photonic component (122) is arranged in the interconnect stack (114) at a vertical distance from the substrate (102). An optical waveguide in the interconnect stack (114), herein BEOL waveguide (128), is optically coupled to the photonic component (122) and has an optical BEOL coupling section (128.2). An optical interconnect structure (132) is arranged and configured for optically coupling radiation from the BEOL coupling section (128.2) into the FEOL coupling section (130.1) and vice versa. The optical interconnect structure (132) comprises a vertical stack of optically coupled wave-guide elements (132.1-132.4) made of a first dielectric material, which each are embedded in a second dielectric material and which in a desired wavelength range have an index of refraction of a higher value than the embedding second dielectric material. The optically coupled waveguide elements (132.1-132.4) are arranged and configured for receiving optical radiation in the desired wavelength range from the BEOL coupling section (128.2) or the FEOL coupling section (130.1) by coupling the optical radiation into at least one of the waveguide elements, and for cooperatively forming and sustaining, using the coupled optical radiation, one or more supermodes of optical radiation that vertically extend across the vertical stack of coupled optically coupled waveguide elements (132.1-132.4), and for coupling the one or more supermodes into the FEOL coupling section (130.1) or the BEOL coupling section (128.2), respectively.