Direct-Bonding Surface Preparation With Sharp Cavity Edges

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Solution Overview

Problem

Conventional methods for preparing bonding surfaces in microelectronics lead to undesirable rounding of cavity edges during chemical-mechanical planarization, which degrades the quality of molecular bonds and increases bond seam dimensions.

Innovation Solution

A sacrificial material or temporary filler is deposited in the cavities and trenches, matching the CMP removal properties of the oxide layer, followed by planarization and selective removal with an etchant that is nonreactive to the oxide surface, preserving sharp edges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If chemical-mechanical planarization is applied to remove photoresist and flatten the oxide surface, then surface flatness is improved, but cavity edge rounding increases

Engineering Contradiction:

Improvesurface flatnessVSAvoidcavity edge sharpness

Core Design Contradiction:

Manufacturing precisionVSShape

Solution Approach 1:

The cavity edges are protected with a sharpener material before the CMP process. This preliminary protective action ensures that when CMP is applied to flatten the surface and remove photoresist, the cavity edges remain sharp rather than rounding, thus resolving the contradiction between achieving surface flatness and maintaining edge sharpness

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A sharpener material is introduced as an intermediary substance between the cavity edges and the CMP process. This intermediary layer prevents direct contact between the CMP abrasives and the cavity edges, allowing the surface to be planarized while the intermediary protects the edges from rounding

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of substance

If CMP is applied aggressively to remove photoresist completely, then photoresist removal is improved, but oxide surface roughening increases

Engineering Contradiction:

Improvephotoresist removal completenessVSAvoidoxide surface roughness

Core Design Contradiction:

Loss of substanceVSManufacturing precision

Solution Approach 1:

The sharpener material serves as a sacrificial intermediary that absorbs the aggressive action of CMP. It allows complete photoresist removal through thorough CMP processing while the sharpener material itself protects the underlying oxide surface from becoming rough, thus resolving the contradiction between complete photoresist removal and surface roughness control

Inventive Principle:

Principle #24Intermediary (Mediator)

3Area of stationary object

If cavity edges are left exposed during bonding preparation, then bonding surface area is maximized, but bond seam dimensions increase

Engineering Contradiction:

Improvebonding surface areaVSAvoidbond seam dimension

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The cavity edges are pre-treated with sharpener material before bonding. This preliminary sharpening creates well-defined, sharp edges that minimize the bonding seam when the wafers are bonded together, thus resolving the contradiction between maximizing bonding surface area and minimizing bond seam dimensions

Inventive Principle:

Principle #10Preliminary action

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 process ensures flat and smooth bonding surfaces with minimal rounding, enhancing bond integrity and reducing seam dimensions, leading to stronger direct bonds.

Implementation Method 1

The temporary filler is then removed with an etchant that is selective to the temporary filler, but nonreactive toward the oxide surface and toward inner surfaces of the cavities and trenches

Methodology Applied

Scientific EffectSelective etching:

Implementation Method 2

The CMP process is applied to the temporary filler to flatten the temporary filler down to the oxide bonding surface

Methodology Applied

Scientific EffectChemical-mechanical planarization:

Data Source

PatentUS20250364263A1Method for preparing a surface for direct-bonding

Publication Date: 2025.11.27 ADEIA SEMICONDUCTOR BONDING TECHNOLOGIES INC

AI summary

Improved bonding surfaces for microelectronics are provided. An example method of protecting a dielectric surface for direct bonding during a microelectronics fabrication process includes overfilling cavities and trenches in the dielectric surface with a temporary filler that has an approximately equal chemical and mechanical resistance to a chemical-mechanical planarization (CMP) process as the dielectric bonding surface. The CMP process is applied to the temporary filler to flatten the temporary filler down to the dielectric bonding surface. The temporary filler is then removed with an etchant that is selective to the temporary filler, but nonreactive toward the dielectric surface and toward inner surfaces of the cavities and trenches in the dielectric bonding surface. Edges of the cavities remain sharp, which minimizes oxide artifacts, strengthens the direct bond, and reduces the bonding seam.