FEOL Optical Polarization Splitter and Rotator Waveguide
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Solution Overview
Problem
Current semiconductor manufacturing processes lack a method for integrating polarization splitters and rotators (PSRs) at the front-end of the line (FEOL) layers of a CMOS stack, which are essential for managing the polarization of optical signals in photonic devices.
Innovation Solution
Incorporating a first waveguide and a second waveguide in the FEOL layer of a wafer chip, where the second waveguide has a splitter end with layers of polycrystalline silicon, silicon oxide, and silicon nitride, a rotator end with single crystal silicon, silicon oxide, and silicon nitride, and a middle section with layers of single crystal silicon, silicon oxide, and polycrystalline silicon and silicon nitride, to manage the polarization of optical signals by propagating transverse electric and magnetic eigenstates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polarization splitters and rotators are integrated at the FEOL layers of CMOS stack, then photonic device performance is enhanced through effective polarization management, but manufacturing complexity increases due to multi-layer material integration
Solution Approach 1:
The waveguide structure is segmented into multiple functional layers with distinct material compositions. The FEOL stack is divided into specific layers (e.g., silicon nitride layer, silicon oxide layer, polysilicon layer) that can be independently fabricated and optimized, allowing complex polarization management functionality to be achieved through modular layer integration rather than monolithic structure
Solution Approach 2:
The patent employs composite material structures in the waveguide, combining different semiconductor materials (silicon, silicon nitride, silicon oxide, polysilicon) with complementary optical properties. This composite approach enables simultaneous achievement of high refractive index contrast for effective polarization splitting and low loss for signal propagation, resolving the contradiction between performance enhancement and manufacturing simplicity
2Adaptability or versatility
If multiple material layers are used in the waveguide structure for polarization management, then polarization re-orientation capability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes parameter changes in material properties (refractive index, thickness) across different layers to achieve polarization management. By carefully controlling the thickness and refractive index of each layer (e.g., varying silicon nitride layer thickness to adjust phase differences between polarization modes), the system achieves high adaptability in polarization re-orientation while maintaining compatibility with standard CMOS fabrication tolerances
Solution Approach 2:
Different regions of the waveguide structure are assigned different material qualities and compositions tailored to specific functional requirements. For instance, certain layers are optimized for high refractive index contrast in specific regions to enhance polarization splitting, while other regions use materials optimized for low loss propagation, allowing localized optimization without requiring uniform high precision across the entire structure
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 configuration enables effective polarization re-orientation of optical signals, enhancing the performance of photonic devices integrated within the CMOS structure by allowing for the propagation and rotation of transverse magnetic eigenstates to transverse electric eigenstates, facilitating optimal operation of photonic devices within the CMOS layer.
Implementation Method 1
a first waveguide of the wafer chip configured to receive an optical signal from an optical device; and a second waveguide configured to receive a transverse magnetic eigenstate of the received optical signal
Implementation Method 2
the performance of photonic devices on wafer chips is very sensitive to the orientation of the polarization state. Hence, the input polarization state must be processed on the wafer chip for it to be re-oriented into the polarization state for which the photonic devices work the best
Data Source
AI summary
A polarization splitter and rotator of a wafer chip, an opto-electronic device and method of use is disclosed. The first waveguide of the wafer chip is configured to receive an optical signal from an optical device and propagate a transverse electric eigenstate of the received optical signal. The second waveguide is configured to receive a transverse magnetic eigenstate of the received optical signal from the first waveguide. The second waveguide includes a splitter end, a middle section and a rotator end, wherein the splitter end includes a layer of polycrystalline silicon, a layer of silicon oxide and a layer of silicon nitride, the rotated end includes a layer single crystal silicon, a layer silicon oxide and a layer of silicon nitride, and the middle section includes layers of single crystal silicon, silicon oxide polycrystalline silicon and silicon nitride.