Interposer Grating Couplers for Low-Loss 3D Optical Packaging
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Solution Overview
Problem
Existing grating couplers in optical signaling systems have inefficiencies that limit high-speed data transmission in integrated circuits, particularly in 3D packaging technologies like SoIC, WoW, CoW, and CoWoS packages, affecting the performance of photonic integrated circuits and radio-frequency integrated circuits.
Innovation Solution
Integration of grating couplers with high coupling efficiency into the interposer structure of 3D packaging, utilizing semiconductor materials and etching techniques to form grating regions with controlled refractive index contrast and reduced back reflection, enhancing optical signal transmission between photonic dies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional grating couplers are used in optical signaling systems, then the structure is simple and easy to manufacture, but the coupling efficiency is low and data transmission rates are limited
Solution Approach 1:
The patent applies local quality by creating grating regions with spatially varying refractive indices within the interposer structure. Different regions of the interposer have different refractive index profiles optimized for specific optical functions, such as coupling efficiency enhancement and back-reflection reduction. This localized optimization of optical properties enables high data transmission rates while minimizing coupling losses.
Solution Approach 2:
The patent utilizes parameter changes by modifying the refractive index distribution through material composition variations and geometric structure adjustments in the grating regions. By changing physical parameters such as material density, layer thickness, and grating period, the optical coupling efficiency is enhanced without requiring complete structural redesign, thus improving productivity while controlling energy loss.
2Productivity
If grating couplers with high coupling efficiency are integrated into the interposer structure, then data transmission rates improve, but the device complexity increases
Solution Approach 1:
The patent merges the grating coupler functionality directly into the interposer structure, combining multiple functions (optical coupling, signal transmission, and structural support) into a single integrated component. This consolidation reduces the number of separate parts and interfaces, thereby managing device complexity while achieving high data transmission rates through optimized optical pathways.
Solution Approach 2:
The interposer structure is designed with multi-functionality, serving both as a mechanical support platform and as an active optical coupling element through its grating regions. This universal design allows the same structure to perform multiple functions simultaneously, reducing overall system complexity while enhancing productivity through improved optical performance.
3Loss of energy
If grating regions with controlled refractive index contrast are formed using etching techniques, then coupling efficiency increases and back reflection is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-designing the etching patterns and refractive index profiles before the actual manufacturing process. The grating structures are planned with predetermined geometric parameters and material distributions that inherently minimize back reflection. This upfront design optimization reduces the stringency of manufacturing precision requirements during the etching process, as the structures are less sensitive to minor fabrication variations.
4Reliability
If semiconductor materials and etching techniques are used to form grating regions, then optical signal transmission efficiency improves, but the manufacturing process complexity increases
Solution Approach 1:
The patent replaces conventional mechanical assembly methods with semiconductor fabrication techniques, specifically using etching processes to create the grating structures directly within the interposer material. This substitution enables more precise control over optical properties and improves signal transmission reliability, while the etching processes themselves are well-established in semiconductor manufacturing, thereby managing the complexity increase through proven industrial processes.
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
Improves data transmission rates and reduces coupling losses, leading to better device performance and suitability for high-speed applications, including wafer-scale testing.
Implementation Method 1
grating coupler having at least one grating region
Implementation Method 2
grating regions with controlled refractive index contrast and reduced back reflection
Data Source
AI summary
A package structure comprises photonic dies and an interposer structure. Each photonic die includes a dielectric layer and a first grating coupler embedded in the dielectric layer. The interposer structure is disposed below the photonic dies. The interposer structure includes an oxide layer and a second grating coupler embedded in the oxide layer. The photonic dies are optically coupled through the first grating couplers of the photonic dies and the second grating coupler of the interposer structure.