Preparation And Barrier Properties Research Of Cu(Zr) And Cu(Mo) Alloy Films

With continuously decreasing the feature size of integrated circuits（ICs）,aluminum interconnection has seriously restricted the development of the integrated circuit due to its high resistance-capacitance（RC）delay and electromigration.Copper,gradually replacing aluminum,has been widely used as an advanced interconnects material because of its excellent electrical conductivity and resistance to migration.However,copper interconnects also brought some new problems,such as the diffusion between copper and silicon,the adhesion is poor and copper is easy oxidative.So barrier layer is extremely necessary.The thickness of barrier layer has important influence on IC and semiconductor metallization.The diffusion barrier reduces the cross-sectional area of Cu resulting in an increase in electrical resistivity of Cu interconnects.However,it is difficult to obtain an ultra-thin diffusion barrier layer with good step coverage.Thus,the removal of the diffusion barrier is the inevitable trend of future development.The method of copper metallization can effectively solve these problems.Therefore,the research of copper metallization is very important to optimize copper interconnect performance and improve the reliability of copper interconnect.This study discussed the thermal stability and electrical properties of Cu（Zr）and Cu（Mo）alloy films.The difference of Cu（Zr）and Cu（Mo）alloy films on the copper metallization in the application has also been studied.Cu（Zr）and Cu（Mo）alloy films were deposited directly onto SiO₂/Si substrates via DC magnetron sputtering and subsequently annealed in vacuum(2×10^-4Pa)at the various temperature of 300℃-700℃.After this,the characteristics were measured and observed by four-point probe measure（FPP）,X-ray diffraction（XRD）,scanning electron microscope（SEM）,X-ray photoelectron spectroscopy（XPS）,and semiconductor analyzer（Keithley 2400）.The experimental results show that the pure copper film deposited directly on SiO₂substrate obviously failed when annealed at 500℃.Moreover,the film exhibits poor stability and electrical properties.For Cu（Zr）/SiO₂ alloy thin film system,Zr atoms in the film diffuse to the surface and interface after annealing.Zr atoms react with SiO₂ at the interface,generate ZrO₂,constitute a barrier layer of 7nm.While,O atomic distribute scattered because of the reaction of Zr and SiO₂,and it bring about the slope of the interface transition element distribution curve decreases.The addition of Zr atoms has little additional resistivity and good electrical properties.Moreover,it improves the thermal stability of the film to some extent.But the stability of Cu（Zr）alloy film is still poor,further studies are needed to improve the stability of alloy films.For Cu（Mo）/SiO₂ alloy thin film system,the stability of the films has been greatly improved.Mo atoms separate out from the alloy film after annealing,self-form a 8nm barrier layer at the interface.Moreover,Mo cannot react with SiO₂,thus the transition element at the interface is sharp.The interface diffusion is suppressed after high temperature annealing,and no Cu₃Si form.Long time annealing has little effect on the leakage current.Cu（Mo）alloy has excellent reliability.