Effect Of IBAD Process Parameters On Structure And Properties Of Self-Forming Diffusion Barrier Cu(C)Films

Nowadays,the integrated circuit has been developing rapidly since its birth,copper has become a new generation of interconnect materials instead of aluminum.In order to prevent the copper from diffusing into the silicon substrate and causing device performance damage,and to improve the adhesion between copper and silicon and silicon dioxide,a diffusion barrier must be wrapped outside the copper interconnects.In this paper,Cu（C）alloy thin films for self-forming diffusion barrier layer were prepared by the technique of ion beam assisted deposition.The influence of deposition temperature,assisted ion beam energy and ion/atom arrival ratio on microstructure,electrical properties and diffusion barrier properties of Cu（C）thin film have been studied.Here follows conclusions:（1）With the increase of assisted source ion beam energies（0,0.1,0.2,0.3,0.4keV）,surface roughness of Cu（C）thin films gradually increase,grain sizes and defects density of internal films decrease at first and then increased,resulting in the resistivity of the as-deposited films decrease at first and then increase.And with the ion beam energy of 0.1 keV,the film has the smallest resistivity.The films with assisted source ion beam energy of 0.4 keV,the thermal effect caused by the ion beam bombardment energy of 0.4 keV makes the film to produce Si C phase in advance acting as diffusion barrier layer,so it has the best thermal stability（400℃,1 h）.（2）Controlling deposition temperature at 100℃or more,at the interface between Cu（C）thin film and Si substrate,a spontaneous formation of the SiC phase and amorphous carbon layer happens,which effectively prevents the film from inter-diffusion reaction between Cu and Si and the formation of deep level impurity Cu₃Si even after 400℃annealing for an hour.However,when the deposition temperature reaches 200 to 300℃,there is a serious agglomeration phenomenon of Cu atoms in the films,resulting in the formation of a large number of defects in the films.Furthermore,after annealing,the films are easily oxidized,causing electrical resistivity to rise abruptly.In view of the film deposited at 100℃,after annealing treatment,it remains the lowest resistivity of 4.44μΩ?cm,we conclude that controlling the deposition temperature at 100℃is the most conducive for Cu（C）thin film self-forming diffusion barrier layer to obtaining the lowest resistivity and the most superior thermal stability.（3）With the increasing of the ion atom arrival ratio,the migration rate of the deposited atom increases in the early stage,the nucleation rate increases,the density of Cu（C）alloy film increases,and the effect density of the film reduces,when the arrival ratio is too high,the internal stress of the film increases sharply,resulting in a large increase in the internal defect density.Thus,the change trend of the resistivity of as-deposited film is to decrease first and then increase,and the Cu（C）film with the ion atom arrival ratio of 0.635 has the lowest resistivity,and it also has the best thermal stability and diffusion barrier properties.