Metal Blocking Structures Mitigate Waveguide Coupling
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Solution Overview
Problem
The integration of silicon nitride waveguides with back-end-of-line (BEOL) interconnect structures in photonics chips leads to unwanted coupling due to modal index matching, degrading waveguide performance, especially in narrow waveguides like tapered sections.
Innovation Solution
A structure comprising a waveguide core with a back-end-of-line interconnect structure featuring a cap layer, an interlayer dielectric layer, and metal features embedded in the interlayer dielectric layer, where the metal features have an overlapping arrangement with the waveguide core to mitigate coupling between the waveguide and the interconnect layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If silicon nitride waveguides are integrated with BEOL interconnect structures, then layout area and cost are reduced, but unwanted coupling degrades waveguide performance
Solution Approach 1:
A metal blocking structure is introduced as an intermediary element between the silicon nitride waveguide core and the BEOL interconnect structures. This metal layer acts as a mediator that prevents unwanted optical coupling while allowing the integrated layout to be maintained, thus resolving the contradiction between compact integration and waveguide performance.
Solution Approach 2:
The harmful coupling effect is extracted and blocked by removing the direct optical path between the waveguide core and BEOL dielectric layers through the introduction of a metal blocking structure. This extraction of the harmful interaction allows the integrated structure to maintain both compact layout and reliable waveguide operation.
2Area of moving object
If narrow waveguide dimensions are used, then layout area is reduced, but coupling with BEOL dielectric layers increases
Solution Approach 1:
The metal blocking structure serves as an intermediary that decouples the narrow waveguide from the BEOL dielectric layers. By placing this metal layer between the waveguide core and interconnect structures, the harmful coupling effect is blocked while allowing the narrow waveguide dimensions to be maintained for compact layout.
Solution Approach 2:
The metal blocking structure is selectively placed only in regions where coupling with BEOL dielectric layers occurs, while leaving other regions of the waveguide unchanged. This localized intervention prevents unwanted coupling in specific areas without affecting the overall narrow waveguide design and compact layout.
3Adaptability or versatility
If BEOL interconnect structures are added, then functionality is improved, but operational overhead increases
Solution Approach 1:
The metal blocking structure is integrated into the existing BEOL interconnect fabrication process as an additional layer, allowing the interconnect functionality to be added without requiring separate processing steps. This intermediary layer is deposited using standard sputtering or evaporation techniques that are already part of the BEOL process flow.
Solution Approach 2:
The blocking function and the interconnect structure are merged into a single integrated system. The metal layer that provides optical blocking is simultaneously incorporated into the interconnect fabrication sequence, combining two functions (optical isolation and electrical interconnection) into one unified structure and process flow.
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 effectively blocks or mitigates unwanted coupling between the optical signal in the waveguide core and the interconnect layers, improving waveguide performance by reducing operational overhead and maintaining layout and cost efficiency in photonics chips.
Implementation Method 1
The one or more metal features have an overlapping arrangement in a lateral direction with the waveguide core to mitigate coupling between the waveguide and the interconnect layers
Data Source
AI summary
Structures including a waveguide core and methods of fabricating a structure including a waveguide core. A back-end-of-line interconnect structure includes a cap layer, an interlayer dielectric layer, and one or more metal features embedded in the interlayer dielectric layer. The interlayer dielectric layer is stacked in a vertical direction with the cap layer. The one or more metal features have an overlapping arrangement in a lateral direction with the waveguide core, which is arranged under the back-end-of-line interconnect structure.