Hybrid Waveguide Interlayer Thickness Control

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Solution Overview

Problem

Current silicon photonics devices face challenges in achieving accurate interlayer thickness control, particularly in the integration of silicon nitride and silicon waveguides on a silicon-on-insulator substrate, which affects the performance of passive and active optical components due to issues like high optical power sensitivity and propagation loss.

Innovation Solution

A method for forming vertically integrated hybrid waveguides with precise interlayer thickness control, involving a silicon-on-insulator substrate, multi-layer hard mask formation, and sequential etching and deposition processes to achieve a controlled silicon oxide and silicon nitride waveguide structure, ensuring an interlayer thickness of no greater than 90 nm for reduced coupling loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional deposition and etching processes are used for hybrid waveguide fabrication, then manufacturing simplicity is maintained, but interlayer thickness control precision deteriorates

Engineering Contradiction:

Improveinterlayer thickness controlVSAvoidfabrication process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The fabrication process is divided into distinct stages: forming the core waveguide layer, depositing the first cladding layer, forming the overlay waveguide layer, and depositing the second cladding layer. Each stage uses specific processes optimized for that layer, allowing precise thickness control at each step while maintaining overall process manageability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first cladding layer is deposited and planarized before forming the overlay waveguide layer. This preliminary action ensures a flat surface for subsequent layer formation, enabling precise thickness control of the overlay layer and preventing coupling loss variations

Inventive Principle:

Principle #10Preliminary action

2Loss of energy

If interlayer thickness is not precisely controlled, then fabrication complexity is reduced, but coupling loss increases

Engineering Contradiction:

Improvecoupling lossVSAvoidinterlayer thickness control

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The patent employs thickness monitoring during deposition processes to ensure each cladding layer achieves the target thickness. This feedback mechanism allows real-time adjustment of deposition parameters to maintain precise thickness control, minimizing coupling loss between waveguide layers

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent specifies precise thickness parameters for each layer (core waveguide: 220nm, first cladding: 30-50nm, overlay waveguide: 220nm, second cladding: 30-50nm) and controls these parameters through regulated deposition conditions, ensuring optimal coupling efficiency while maintaining manufacturing precision

Inventive Principle:

Principle #35Parameter changes

3Productivity

If bandwidth is increased for high-speed communication, then communication capacity improves, but sensitivity to interlayer thickness variations increases

Engineering Contradiction:

Improvecommunication bandwidthVSAvoidinterlayer thickness tolerance

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent uses a composite structure with different materials for different layers (silicon nitride for core and overlay waveguides, silicon oxide for cladding layers). This composite approach allows optimization of each layer's properties and provides differentials in etch rates and deposition characteristics, enabling precise thickness control even at high bandwidth operating conditions

Inventive Principle:

Principle #40Composite materials

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 enhances the performance of silicon photonics devices by achieving low coupling loss and improved optical communication bandwidth, addressing the limitations of existing technologies in temperature tolerance and optical transparency.

Implementation Method 1

vertically integrated hybrid waveguide... silicon nitride waveguide structure with a controlled silicon oxide interlayer thickness

Methodology Applied

Scientific EffectEvanescent field coupling: Total Internal Reflection

Data Source

PatentUS10107961B2Vertical integration of hybrid waveguide with controlled interlayer thickness

Publication Date: 2018.10.23 MARVELL ASIA PTE LTD

AI summary

An silicon photonics device of hybrid waveguides having a coupling interlayer with an accurately controlled thickness and a method of making the same. The device includes a first plurality of Si waveguides formed in a SOI substrate and a first layer of SiO2 overlying the first plurality of Si waveguides and a second plurality of Si3N4 waveguides formed on the first layer of SiO2. At least one Si3N4 waveguide is disposed partially overlapping with at least one of the first plurality Si waveguides in vertical direction separated by the first layer of SiO2 with a thickness controlled no greater than 90 nm. The device includes a second layer of SiO2 overlying the second plurality of Si3N4 waveguides. The method of accurately controlling the coupling interlayer SiO2 thickness includes a multilayer SiO2/Si3N4/SiO2 hard mask process for SiO2 etching and polishing as stopping and buffering layer as well as Si waveguide etching mask.