Wafer-Level Handle Replacement for Silicon Photonics
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Solution Overview
Problem
Optical data communication systems face challenges in reliable and efficient transmission of laser light between optical fibers and chips, due to adverse optical coupling issues when the thickness of base layers in silicon-on-insulator (SOI) or CMOS wafers is less than 1 micrometer, affecting light propagation in silicon photonics waveguides.
Innovation Solution
A method for wafer-level handle replacement is introduced, where a replacement handle structure with optical cladding material is attached to the wafer, and cavities are formed through a hard mask material to mitigate optical coupling, enabling efficient optical connection between optical devices on the die and external devices. This involves removing the base layer, attaching a new handle structure, and etching cavities in the replacement handle structure to expose target layers within the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the base layer thickness is reduced to enable optical transmission, then optical coupling is improved, but structural stability and mechanical strength deteriorate
Solution Approach 1:
The patent introduces an optical cladding layer as an intermediary material between the silicon base layer and the optical waveguide. This cladding layer with lower refractive index prevents harmful optical coupling while maintaining mechanical structural integrity, resolving the contradiction between optical performance and structural stability
Solution Approach 2:
The patent changes the refractive index parameter by introducing optical cladding material with a lower refractive index than silicon. This parameter change creates an optical barrier that prevents light leakage into the base layer, thereby reducing optical coupling effects while preserving the mechanical strength of the thin base layer
2Use of energy by moving object
If the base layer thickness is reduced for optical performance, then light propagation is improved, but adverse optical coupling increases
Solution Approach 1:
The optical cladding layer serves as a mediator that guides light propagation efficiently while preventing adverse coupling between the waveguide and base layer. The cladding material creates an optical confinement structure that improves light propagation by confining light within the waveguide region
Solution Approach 2:
The patent applies local quality by creating regions with different optical properties - the optical cladding layer is specifically positioned around the waveguide with different refractive index characteristics. This local differentiation enables efficient light propagation in the waveguide region while preventing optical coupling in the interface region
3Reliability
If wafer-level handle replacement is implemented to mitigate optical coupling, then optical transmission reliability is improved, but device complexity increases
Solution Approach 1:
The wafer structure is segmented into distinct functional layers: the silicon base layer for mechanical support, the optical cladding layer for optical confinement, and the waveguide layer for light transmission. This segmentation allows each layer to be optimized independently, improving optical transmission reliability while managing complexity through modular design
Solution Approach 2:
The replacement handle structure serves multiple functions simultaneously: it provides mechanical support like the original base layer, creates optical confinement to prevent coupling, and enables efficient light propagation. This multi-functionality improves reliability without proportionally increasing complexity
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 reduces optical coupling, allowing for reliable and efficient transmission of laser light by creating a new optical path that minimizes interference between optical devices and the handle structure, enhancing the performance of optical data communication systems.
Implementation Method 1
The first thickness region is formed of an optical cladding material that mitigates optical coupling between optical devices within the die and the replacement handle structure
Implementation Method 2
etching the replacement handle structure through the openings in the hard mask material to form corresponding cavities in the replacement handle structure
Data Source
AI summary
A wafer includes a number of die, with each die including electronic integrated circuits and optical devices. The wafer has a top surface and a bottom surface and a base layer. The bottom surface of the wafer corresponds to a bottom surface of the base layer. A wafer support system is attached to the top surface of the wafer. A thickness of the base layer is removed to expose a target layer within the wafer and to give the wafer a new bottom surface. A replacement handle structure is attached to the new bottom surface of the wafer. The replacement handle structure includes a first thickness region and a second thickness region. The first thickness region is positioned closest to the new bottom surface. The first thickness region is formed of an optical cladding material that mitigates optical coupling between optical devices within the die and the replacement handle structure.