Microstructural Effects on the Interfacial Adhesion of Nanometer-Thick Cu Films on Glass Substrates: Implications for...

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Interface stability in nanosized thin films on brittle substrates is critical for microelectronics, but brittle-ductile interfaces often limit reliability.
• Extrinsic toughening mechanisms during delamination can improve interface adhesion by tuning thin film properties.

Purpose of the Study:

• To investigate the influence of film microstructure on interface adhesion in nanosized copper (Cu) films on brittle glass substrates.
• To understand how varying grain size distributions affect the mechanical properties and adhesion of thin films.

Main Methods:

• Deposition of 110 nm thin Cu films on glass substrates using magnetron sputtering, controlling for film thickness, residual stresses, and texture.
• Variation of Cu film microstructure through deposition parameters and isothermal annealing, creating bimodal grain size distributions.
• Determination of interface adhesion using stressed molybdenum (Mo) overlayers to induce delamination and analysis of buckled films via focused ion beam cutting and confocal laser scanning microscopy.

Main Results:

• Interface adhesion energy varied from 2.35 J/m² (larger grains) to 4.90 J/m² (highest amount of nanosized grains).
• Films with smaller grains demonstrated a higher capacity for energy absorption during delamination.
• Decoupled analysis of elastic and plastic deformation in buckled films explained the enhanced adhesion in finer-grained films.

Conclusions:

• The microstructure, specifically the prevalence of nanosized grains, significantly impacts the interface adhesion of thin films.
• Films with smaller grains exhibit superior energy absorption capabilities, leading to improved adhesion and reliability.
• This study provides a pathway for enhancing thin film stability in technological applications by controlling film microstructure.