Photonics Chip Dual Underfill for Optical-Mechanical Trade-offs

Solution Overview

Problem

Conventional underfill materials in silicon photonics chips provide poor optical quality due to non-optimized refractive index, while optical epoxies offer high optical transmission but result in mechanical failure due to high thermal expansion, limiting the integration of high-bandwidth photonics chips with optical fibers.

Innovation Solution

A dual underfill material system is employed, using optical epoxy in localized regions for improved optical pathways and conventional underfill in interstitial areas for mechanical support, with a low-viscosity optical epoxy in cavities between grated optical couplers and high-viscosity underfill material outside to prevent diffusion and mechanical failure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If optical epoxy material is used to fill the space between grated optical couplers, then optical transmission is improved, but mechanical reliability deteriorates due to high thermal expansion

Engineering Contradiction:

Improveoptical transmissionVSAvoidmechanical reliability

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent applies different materials with different properties to different regions: optical epoxy is used specifically in the optical coupling region between grated optical couplers where optical transmission is critical, while conventional underfill material is used in the interstitial regions where mechanical support is critical. This local differentiation allows each region to be optimized for its primary function without compromising the other.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs a composite material system consisting of two distinct underfill materials: optical epoxy material with optimized refractive index for optical regions, and conventional underfill material with mechanical properties for structural regions. This composite approach combines the advantages of both materials while mitigating their individual disadvantages.

Inventive Principle:

Principle #40Composite materials

2Strength

If conventional underfill material is used to provide mechanical support, then mechanical integrity is improved, but optical quality deteriorates due to non-optimized refractive index

Engineering Contradiction:

Improvemechanical integrityVSAvoidoptical quality

Core Design Contradiction:

StrengthVSIllumination intensity

Solution Approach 1:

The patent applies different materials with different properties to different regions: optical epoxy is used specifically in the optical coupling region between grated optical couplers where optical transmission is critical, while conventional underfill material is used in the interstitial regions where mechanical support is critical. This local differentiation allows each region to be optimized for its primary function without compromising the other.

Inventive Principle:

Principle #3Local quality

3Illumination intensity

If optical epoxy material is used throughout, then optical pathways are improved, but thermal expansion causes mechanical failure

Engineering Contradiction:

Improveoptical pathwaysVSAvoidthermal expansion

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent applies different materials with different properties to different regions: optical epoxy is used specifically in the optical coupling region between grated optical couplers where optical transmission is critical, while conventional underfill material is used in the interstitial regions where mechanical support is critical. This local differentiation allows each region to be optimized for its primary function without compromising the other.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The conventional underfill material acts as an intermediary in the interstitial regions, providing mechanical support and thermal expansion management, while the optical epoxy material serves as an intermediary in the optical regions, facilitating optical transmission between the grated optical couplers. Each material mediates the specific requirements of its region.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 both optical transmission and mechanical integrity, reducing stress and improving assembly yields by optimizing thermal expansion matching and maintaining structural integrity.

Implementation Method 1

Conventional underfill materials in silicon photonics chips provide poor optical quality due to non-optimized refractive index

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

Out-of-plane coupling uses an optical grating to couple light from the fiber to the waveguide

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS10409006B2Photonics chip

Publication Date: 2019.09.10 GLOBALFOUNDRIES US INC

AI summary

The present disclosure relates to semiconductor structures and, more particularly, to photonics chips and methods of manufacture. A structure includes: a photonics chip having a grated optical coupler; an interposer attached to the photonics chip, the interposer having a grated optical coupler; an optical epoxy material provided between the grated optical coupler of the photonics chip and the grated optical coupler of the interposer; and epoxy underfill material provided at interstitial regions between the photonics chip and the interposer which lie outside of an area of the grated optical couplers of the photonics chip and the interposer.