Structured Substrate Preparation for Clean Hybrid Cu/SiO2 Bonding

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Solution Overview

Problem

Existing methods for preparing structured substrates for direct bonding, particularly those with hybrid Cu/SiO2 surfaces, face challenges in achieving high-quality bonding due to surface degradation from aggressive cleaning processes, which round off edges and reduce bonding quality.

Innovation Solution

A method involving a protective layer with lower adhesion energy than the thin film, allowing for resin removal without damaging the surface, followed by separation from a temporary substrate, ensuring the substrate surface remains intact for direct bonding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If plasma cleaning methods combined with wet cleanings are used to remove resin, then complete resin removal is achieved, but the surface quality deteriorates and roughness increases

Engineering Contradiction:

Improvebonding qualityVSAvoidsurface roughness

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The harmful resin is selectively removed through controlled etching processes that target the resin while preserving the underlying hybrid Cu/SiO2 surface. The protective layer is designed to be removed selectively, taking the resin with it while leaving the bonding surface intact.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

A protective layer is introduced as an intermediary between the resin and the hybrid Cu/SiO2 surface. This protective layer allows resin removal through controlled etching while protecting the underlying surface from direct exposure to aggressive cleaning chemicals.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-generated harmful factors

If aggressive cleaning methods are applied to remove resin, then resin contamination is eliminated, but the polished surface is degraded

Engineering Contradiction:

Improveresin contaminationVSAvoidsurface quality

Core Design Contradiction:

Object-generated harmful factorsVSManufacturing precision

Solution Approach 1:

The protective layer, which initially serves to protect during structuring, is later used beneficially to control the resin removal process. The same layer that enabled precise structuring now enables selective resin removal without damaging the surface.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The etching parameters are carefully controlled to change the selectivity of the removal process. By adjusting etching conditions, the resin is removed while the hybrid Cu/SiO2 surface remains unaffected, transforming a potentially harmful process into a beneficial one.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If the surface is re-polished after structuring to improve quality, then surface roughness is reduced, but the pad edges are rounded off and bonding is prevented

Engineering Contradiction:

Improvesurface roughnessVSAvoidbonding capability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The surface is prepared and polished before structuring is performed. By completing all surface preparation operations before creating the structured pads, the sharp edges are preserved and no subsequent polishing can round them off.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The manufacturing process is segmented into distinct phases: surface preparation phase (polishing) followed by structuring phase (etching). This temporal separation ensures that surface quality is established before structuring, and structuring does not compromise surface integrity.

Inventive Principle:

Principle #1Segmentation

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 method preserves the surface quality of hybrid Cu/SiO2 surfaces, enabling high-quality direct bonding without edge rounding, thus improving bonding integrity and reliability.

Implementation Method 1

bonding a protective layer to the thin film by direct bonding... in which method either the resin is removed between step d) and step e) and the adhesion energy between the protective layer and the thin film is lower than the adhesion energy between the temporary substrate and the protective layer

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS12575374B2Method of preparing a structured substrate for direct bonding

Publication Date: 2026.03.10 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

AI summary

A method of preparing a structured substrate of interest including the following steps: providing a substrate of interest including a thin film, onto which a protective layer has been bonded by direct bonding, depositing a resin, and etching the thin film and a portion of the support substrate through openings in the resin, to form pads, bonding a temporary substrate to the substrate of interest, then separating them, whereby the protective layer is separated from the substrate of interest, the resin being removed prior to the bonding step or during the separation, the protective layer/thin film adhesion energy being lower than the temporary substrate/protective layer adhesion energy or than the resin/protective layer adhesion energy.