Grating Couplers with Substrate Airgaps for Silicon Photonics
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Solution Overview
Problem
Grating couplers in silicon photonics face limited coupling efficiency due to light leakage into the underlying substrate, and existing solutions like metallic mirrors or distributed Bragg reflectors are either incompatible with CMOS processes or require complex fabrication, making them difficult to implement cost-effectively.
Innovation Solution
The integration of airgaps within the substrate material, either as a single merged airgap or an array of airgaps, under the grating coupler, which enhances coupling efficiency by shifting the peak wavelength and relaxing fabrication constraints, allowing for simpler patterning and tuning of the grating coupler performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reflector (metallic mirror or distributed Bragg reflector) is provided under the grating coupler to improve coupling efficiency, then coupling efficiency is improved, but device complexity and fabrication complexity increase
Solution Approach 1:
The patent extracts the reflector function from complex metallic mirrors or distributed Bragg reflectors and implements it using a simple airgap structure. The airgap is formed by removing substrate material to create an empty space, which inherently provides the needed reflectivity without requiring complex multilayer stacks or precious metals. This extraction simplifies the device while maintaining the essential function of reflecting light back into the waveguide.
Solution Approach 2:
The patent replaces expensive and complex reflector materials (noble metals like Au or complex oxide multilayers) with a simple airgap structure that is both inexpensive and easy to fabricate. The airgap is created through standard substrate removal processes, eliminating the need for costly deposition techniques or complex assembly steps, thereby reducing manufacturing costs and process complexity.
2Reliability
If metallic mirrors or distributed Bragg reflectors are used to enhance grating coupler efficiency, then coupling efficiency is improved, but compatibility with CMOS processes is reduced
Solution Approach 1:
The patent extracts the reflector function from materials and structures that are incompatible with CMOS processes (such as noble metals or complex oxide stacks) and replaces it with an airgap structure that is fully compatible with standard CMOS fabrication. The airgap is created through substrate removal, a process that integrates seamlessly with CMOS manufacturing, thereby maintaining compatibility while preserving the reflector function.
3Reliability
If complex reflector structures are implemented, then coupling efficiency is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive reflector materials (noble metals requiring specialized deposition) and complex structures (multilayer stacks requiring precise fabrication) with a simple airgap created through standard substrate removal. This approach dramatically reduces material costs and manufacturing complexity, making the solution cost-effective for mass production while maintaining the essential reflector function.
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 significantly improves the coupling efficiency of grating couplers by reducing light leakage and simplifying the fabrication process, making it compatible with CMOS technology and cost-effective for silicon photonics platforms.
Implementation Method 1
the coupling efficiency of grating couplers are limited due to the light leakage into the underlying substrate
Implementation Method 2
enhances coupling efficiency by shifting the peak wavelength
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to grating couplers integrated with one or more airgap and methods of manufacture. The structure includes: a substrate material comprising one or more airgaps; and a grating coupler disposed over the substrate material and the one or more airgaps.