Vertical Optical Via Single-Mode Transmission
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Solution Overview
Problem
Current photonic device integration technologies face limitations in vertical optical data transfer due to the use of large, multimode optical vias and challenging fabrication of small reflective mirrors, which restricts high-bandwidth communication between layers.
Innovation Solution
A method for creating a vertical optical via in a semiconductor substrate involves forming a hard mask, exposing a via hole, and depositing cladding and core layers with specific refractive indices to facilitate single-mode optical transmission, allowing for the formation of microscopic, high-bandwidth communication pathways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If large optical vias are used for vertical optical transmission, then transmission distance is improved, but the via becomes multimode which degrades transmission quality
Solution Approach 1:
The patent applies local quality by creating a core region with higher refractive index (n2) surrounded by a cladding region with lower refractive index (n1) within the optical via. This local differentiation of optical properties enables single-mode transmission even in larger diameter vias, resolving the contradiction between transmission distance and transmission quality.
Solution Approach 2:
The patent uses composite material structure by combining materials with different refractive indices to form a core-cladding configuration. The core material has refractive index n2 and the cladding material has refractive index n1, creating a composite optical waveguide that maintains single-mode operation over longer distances.
2Area of stationary object
If small spacing between vertical waveguides is used, then integration density is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent changes the refractive index parameter by introducing a core region with higher refractive index (n2) compared to the cladding region (n1). This parameter change creates stronger optical confinement, allowing for tighter waveguide spacing while maintaining signal integrity and reducing crosstalk, thus improving integration density without proportionally increasing manufacturing precision requirements.
3Ease of operation
If turning mirrors are added to reflect light from waveguide to optical via, then optical coupling is improved, but device complexity and fabrication difficulty increase
Solution Approach 1:
The patent extracts the turning mirror component from the optical coupling system and replaces it with a direct core-cladding waveguide structure. By removing the mirror element and using refractive index contrast alone to achieve mode matching and coupling, the device complexity and fabrication difficulty are reduced while maintaining optical coupling efficiency.
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 efficient, high-bandwidth, ultra-fast intra-die communication by providing single-mode optical transmission through the semiconductor substrate, improving communication between logic and DRAM dies while eliminating airgaps and allowing for tighter bonding layouts.
Implementation Method 1
At least one core layer is provided in the via hole. The core layer(s) have at least a second index of refraction greater than the at least the first index of refraction.
Implementation Method 2
The cladding layer(s) have at least a first index of refraction. At least one core layer is provided in the via hole. The core layer(s) have at least a second index of refraction greater than the at least the first index of refraction.
Data Source
AI summary
A method for providing a vertical optical via for a semiconductor substrate is described. The semiconductor substrate has a front surface and a back side. A hard mask having an aperture therein is formed on the front surface. Part of the semiconductor substrate exposed by the aperture is removed to form a via hole. The via hole has a width not exceeding one hundred micrometers and a bottom. Cladding layer(s) and core layer(s) are provided in the via hole. The core layer(s) have at least a second index of refraction greater than that of the core layer(s). A portion of the semiconductor substrate including the back side is removed to expose a bottom portion of the core layer(s) and a bottom surface of the semiconductor substrate. The vertical optical via includes the cladding and core layers. The vertical optical via extends from the front surface to the bottom surface.