Direct Bonding Infrared Detector With Thin SiOx Adhesion Layer

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Solution Overview

Problem

Conventional infrared detector bonding methods using epoxy as an adhesive layer absorb infrared radiation, reducing transmission efficiency and requiring additional anti-reflective coatings, which increases manufacturing costs and complexity.

Innovation Solution

A direct bonding method employing a thin silicon monoxide (SiOx) layer with a thickness of 1000 angstroms or less, deposited and polished using chemical-mechanical polishing, eliminates the need for epoxy and anti-reflective coatings, enabling covalent bonding between infrared detector wafers and silicon wafers without voids.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If epoxy is used as an adhesive layer for bonding infrared detector wafers to silicon wafers, then bonding strength is improved, but infrared radiation transmission is reduced due to absorption by the epoxy material

Engineering Contradiction:

Improvebonding strengthVSAvoidinfrared radiation transmission

Core Design Contradiction:

StrengthVSLoss of energy

Solution Approach 1:

The patent removes the epoxy adhesive layer from the bonding interface between infrared detector wafers and silicon wafers. By extracting the harmful epoxy material, the invention eliminates infrared radiation absorption while maintaining bonding strength through direct wafer bonding techniques, thus resolving the contradiction between bonding strength and infrared transmission.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a thin film intermediary layer (such as silicon dioxide or silicon nitride) at the bonding interface to replace epoxy. This intermediary layer provides adequate adhesion between the infrared detector wafer and silicon wafer while being transparent to infrared radiation, thereby maintaining both bonding strength and infrared transmission.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of energy

If anti-reflective coatings are applied to compensate for epoxy absorption, then infrared transmission is improved, but manufacturing complexity and cost increase

Engineering Contradiction:

Improveinfrared radiation transmissionVSAvoidmanufacturing process complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent extracts the source of the problem by removing the epoxy adhesive layer that causes infrared absorption. This eliminates the need for additional anti-reflective coatings to compensate for epoxy-induced losses, thereby simplifying the manufacturing process while maintaining infrared transmission performance.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the optical properties of the bonding interface by replacing epoxy with materials that have different optical characteristics—specifically, materials that are transparent to infrared radiation. This inherent optical transparency eliminates the need for additional anti-reflective coatings.

Inventive Principle:

Principle #32Color changes

3Ease of manufacture

If conventional epoxy bonding methods are used, then bonding process is simplified, but infrared detector performance deteriorates due to optical interference from epoxy

Engineering Contradiction:

Improvebonding process simplicityVSAvoidinfrared detector performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent uses a thin film intermediary layer (silicon dioxide or silicon nitride) at the bonding interface that serves dual purposes: providing adequate adhesion like epoxy while simultaneously being transparent to infrared radiation. This intermediary approach maintains bonding process simplicity while eliminating the performance-deteriorating optical interference caused by epoxy.

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 infrared transmission across all spectral regions, reduces optical interference, and simplifies manufacturing by eliminating the need for anti-reflective coatings, resulting in improved detector performance and cost-effectiveness.

Implementation Method 1

a thin silicon monoxide (SiOx) layer with a thickness of 1000 angstroms or less, deposited and polished using chemical-mechanical polishing

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Implementation Method 2

a direct bonding process for bonding contact surfaces of infrared detectors and silicon wafers using oxidation of the contact surfaces

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentUS11587971B2Infrared detector having a directly bonded silicon substrate present on top thereof

Publication Date: 2023.02.21 L3 CINCINNATI ELECTRONICS CORP

AI summary

A direct bonding method for infrared focal plane arrays, includes steps of depositing a thin adhesion layer on infrared radiation detecting material, removing a portion of the thin adhesion layer with a chemical-mechanical polishing process, forming a bonding layer at a bonding interface, and bonding the infrared radiation detecting material to a silicon wafer with the thin adhesion layer as a bonding layer. The thin adhesion layer may include SiOx, where x ranges between 1.0 and 2.0. The thickness of the thin adhesion layer to form the bonding layer is 500 angstrom or less.