The Deposition And Properties Of Ti/Ti_xC_y/DLC Functionally Graded Material On Copper Substrate

In recent years,with society stride forward to electronic technology,automatization,and digital network information society.And copper are finding increasing applications in micro-electronics,micro-electro-mechanical systems(MEMS) and Hi-tech material applications.However copper has its material limitations.In particular,it has relatively low hardness,high oxidation and rate of wear,bad corrosion resistance which have severely limited its widespread applications.In this paper,aimed at difficulties of copper applications, Ti/Ti_xC_y/DLC has been proposed as functionally graded material to deposit on the copper substrate with different depositing methods,which intensify the adhesion between DLC films and copper substrate and improve the properties of copper.A graded intermediate layer design has been proposed prior to deposition of DLC by combining plasma enhanced unbalanced magnetron sputtering physical vapor deposition (PEUMS-PVD) and microwave electron cyclotron resonance plasma enhanced chemical vapor deposition(MW-ECR PECVD) techniques.Improvement in low adhesion between DLC films and copper substrate can be achieved by depositing the graded intermediate layer of Ti/Ti_xC_y,Si/Si_xN_y.The DLC films were smooth,dense and amorphous with typical diamond-like structure and thickness level was in a nanometer range.And it has excellent hardness and elastic modulus,much higher than substrate.In the experiment of Si/Si_xN_y/DLC films deposition,it was found that Si atom sputtering yield decreased,because of target poisoning phenomenon.So Ti was introduced as intermediate layer element to deposit DLC films on copper substrate to solve this problem.But there was element H in the intermediate layer,which held high residual stress and decreased the hardness and adhesion between the films and substrate.Ti/Ti_xC_y intermediate layer were prepared by PEUMS-PVD technique so as to avoid introducing H element,which reduced the stress concentration and improved the stability of intermediate layer.XRD and XPS analyses indicated that TiC nanocrystallines generated in the films,high-energy Ti ion and some C atoms diffused into the substrate which widened the interface between intermediate layer and substrate to make a nice interface mixing and improve the adhesion between DLC films and substrate.For acquiring the DLC films with excellent properties to protect the copper substrate,the experiment to make the best optimization parameter choice had been studied systematically. With the increase of intermediate layer deposition bias voltage,Ti target input current and C target power,bombardment of active radical around the substrate increased.The bombardment may wipe off any weak bond and impurity,be more conducive to sp³-bond come into being and get much smooth surface.Increase of intermediate layer deposition bias voltage and proper bombardment would accelerate the diffusion of interface components,which enhanced adhesion between films and substrate.When the Ti target input current was rised,the Ti content of DLC films increased too.Ti atoms substituted triply bonded carbon atoms,which would reduce the average coordination number of DLC films,and improved the transformation from sp³-bond to sp²-bond.The incidence of Ti ion with high energy leaded to the improvement of adhesion.At high value of Ti target input current,micro-cell corrosion would take place between the large granule Ti and films,the riched large granule Ti would become anode and the films become cathode of local corrosion.With shallow infusion caused by C target sputtering, ions with high energy penetrated into the coating of substrate causing internal pressure stress. This leaded to the increases of film density and formation of sp³ bonds.However,the ion of high energy diffused in the interface which deteriorated the adhesion and mechanism of the films,once the bombardment energy had exceeded a critical value.As a result,the best parameters for excellent performance of DLC films found were:intermediate layer deposition bias voltage of 100V,Ti target input current of 0.2A,C target power of 200W,and Ti/C ratio was 1.And the high quality DLC films with minimal roughness of 2.11nm was obtained at the aboved parameters,maximal hardness and elastic modulus of 17.6GPa and 233.7GPa were respectively achieved too.DLC films held excellent hardness suffering from the positive pressure of 400mN for 20 minutes,the coefficient of friction was only 0.13.And the polarization resistance of DLC films improved two orders of magnitude compared with copper substrate.The maximal value of thermal conductivity of DLC films with optimized parameter of graded intermediate layer was 3.63Wm^-1K^-1,which enhanced the heat transfer effect of copper substrate.