Multi-Layer Silicon Nitride Waveguide Dielectric

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Solution Overview

Problem

Photonics chips experience optical signal absorption due to hydrogen-nitrogen bonds in silicon nitride layers, leading to unwanted optical loss, particularly in long-range signal routing.

Innovation Solution

A structure comprising a waveguide with a first silicon nitride dielectric layer and a second silicon nitride layer with lower absorption, where the second layer is deposited using a method that avoids hydrogen incorporation, reducing modal overlap and absorption loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a silicon nitride dielectric layer is deposited over optical components, then the structural integrity and fabrication process are simplified, but optical loss increases due to hydrogen absorption

Engineering Contradiction:

Improvefabrication processVSAvoidoptical loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent divides the dielectric layer into multiple segments: a first dielectric layer deposited by PECVD (which contains hydrogen and causes absorption), and a second dielectric layer deposited by SACVD (which lacks hydrogen and causes minimal absorption). This segmentation allows each layer to serve different functions - the first layer provides structural integrity and ease of manufacture, while the second layer protects the optical signals from absorption loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second dielectric layer acts as an intermediary between the optical components and the environment. It is positioned directly over the waveguide and optical components to shield them from harmful interactions, while the first dielectric layer serves as a structural foundation. This intermediary arrangement allows the optical signals to propagate without direct exposure to hydrogen-containing materials.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If a continuous silicon nitride slab is formed over optical components, then manufacturing is simplified, but absorption of optical signals occurs through nitrogen-hydrogen bonds

Engineering Contradiction:

Improvecontinuous slab formationVSAvoidabsorption

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The continuous slab is segmented into two distinct layers with different deposition methods and compositions. The first layer (PECVD) provides the continuous structural foundation, while the second layer (SACVD) provides a hydrogen-free protective interface. This segmentation maintains the ease of manufacturing a continuous structure while eliminating the harmful absorption effect.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses a composite dielectric structure combining two different silicon nitride layers with different deposition histories and hydrogen contents. The PECVD layer and SACVD layer have different material properties - the PECVD layer is easier to deposit but contains hydrogen, while the SACVD layer is hydrogen-free but requires different deposition parameters. This composite approach allows optimization of both manufacturing ease and optical performance.

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

The solution effectively reduces propagation loss in waveguides by shifting mode distributions away from hydrogen-containing layers, resulting in improved signal transmission efficiency.

Implementation Method 1

the silicon nitride in this slab incorporates hydrogen that, through nitrogen-hydrogen bonds, causes absorption of the optical signals propagating in the optical components

Methodology Applied

Scientific EffectOptical absorption: Absorption (EM radiation)

Implementation Method 2

shifting mode distributions away from hydrogen-containing layers, resulting in improved signal transmission efficiency

Methodology Applied

Scientific EffectModal overlap:

Data Source

PatentUS10698159B2Multiple-layer arrangements including one or more dielectric layers over a waveguide

Publication Date: 2020.06.30 GLOBALFOUNDRIES US INC

AI summary

Structures that include a waveguide and methods of fabricating a structure that includes a waveguide. A first dielectric layer comprised of a first silicon nitride is formed. The waveguide is arranged over the first dielectric layer. A second dielectric layer is formed that is arranged over the waveguide. The second dielectric layer is composed of a second silicon nitride having a lower absorption of optical signals than the first silicon nitride.