Mechanical Property Characterization Of Cu,Ti Nanofilms By In-situ Nanoindentation

In the 21 st century,with the rapid development of energy,information,environment,biotechnology and defense industry,the research on nanometer thin film has also been deepened gradually.In micro-electromechanical systems(MEMS),copper(Cu)films replace aluminum films used for previous interconnects due to their lower resistivity and higher melting points.And Titanium(Ti)films,with good adhesion and biocompatibility,have been widely used in the solar cells,sensors,decomposition of water to hydrogen,hydrogen storage materials,biological sciences and other fields.However,in recent years,the miniaturization,intelligent,high integration,high-density storage and ultrafast transmission of components are requiring nanometer thin film material size to be smaller and smaller and their performance to be higher and higher.With the deepening research of nano-science,the exploration of nano-thin film materials has been gradually extended from observing the surface morphology of the samples to acquiring of characteristic parameters such as mechanical properties.Because mechanical properties are an important basic performance parameter of nanometer thin film materials,it is very urgent to understand the connection and difference between nanometer thin film materials under microscopic conditions and macroscopic mechanical properties,and it is very important to obtain corresponding theoretical data to guide new structure design.However,the research on the mechanical characterization of nanometer thin films is rare.With the continuous development of nanometer thin film technology,nanometer thin film mechanics is bound to become an indispensable part of mechanical research field,and it is an important field which we will study in the future.The results play a very important guiding significance of using of nano-thin film materials.The load-in curve is like the "fingerprint" of the material,and the mechanical properties of the corresponding nanometer thin film material can be obtained.In this paper,the mechanical properties of Cu nanofilm and Ti nanofilm were tested by nanoindentation,and the elastic modulus was used as the main research object.The self-developed scanning electron microscopy/scanning probe microscope(SEM/SPM)combined system and the atomic force microscope(AFM)of Bruker have be employed to conduct the nanoindentation test.The force displacement curve of the tested sample is obtained,and the experimental results are analyzed and discussed.The main contents and achievements of the sample and the research are as follows:1.Based on the Hertzian contact theory and King model,the elastic modulus of Cu nanofilm with thickness of 40,60,80 nm deposited by direct current magnetron sputtering(DCMS)and atomic deposition(ALD)in the Si of(100)direction were investigated by scanning electron microscopy-scanning probe microscopy(SEM/SPM)combined system.It has been found that the elastic modulus of Cu films with various thicknesses deposited by DCMS and ALD were obtained as from 95±2 to 125±4 GPa and from 99±2 to 154±6 GPa,and they are 6%-71% larger than that of their bulk counterpart(90GPa).Furthermore,the elastic modulus of Cu films,either deposited by DCMS or by ALD,are closely related to the film thickness and decreases linearly with the increase of film thickness.In the case of same thickness,elastic modulus of the films obtained by ALD show 4.2%-23.2% higher than those obtained by DCMS,because of smaller grain size.2.The Ti nanofilm with thickness of 60 nm,90 nm,120 nm and 180 nm was deposited on the(100)silicon wafer using DCMS.The elastic modulus of Ti films of different thickness have be obtained by the AFM of Bruker.The results show that the elastic modulus of Ti films with thicknesses of 60-180 nm deposited by DC MS is from 95 to 132 GPa.For the Ti film of the same thickness,the elastic modulus decreases with the increase of the peak force,and with the increase of the depth.The difference between the elastic modulus at different peak values is 12.0% when the thickness is 120 nm,and 3.9% when the thickness of 60 nm.Furthermore,when the peak force is 100 nN,the elastic modulus of Ti films decreases with the increase of the film thickness,and this law is equally applicable when the peak force is 150 n N.Furthermore,the SEM / SPM combined system was used to test the titanium nanofilm film.The elastic modulus of the sample obtained also decreased with the increasing of the film thickness.