| WTi film is one of the most important materials as the diffusion harrier film in Integrated circuit.With the miniaturization of integrated circuit,high barrier performance of WTi film is required.The particle contamination is a key factor that influences the barrier performance of W-Ti films,which is mainly affected by the Ti-rich phase in WTi alloys.It has a significant value for scientific research and important practical significance for improving the barrier performance of WTi film by the regulation of Ti-rich phase in WTi target.The diffusion activation energy of Ti into W with defects was calculated by first principles.The regulation of Ti-rich phase in W-Ti alloys were performed by changing of W powders characteristics,controlling of cooling rate,coupling effect of cryogenic temperature field and magnetic field and the evolution of structure and content of Ti-ich phase was realized.Finally,W-Ti films were prepared using the as-obtained W-Ti targets by majmctron sputtering technology,The WTi diffusion barrier performance was investigated The main conclusions are shown as follows:The initialization of defects in W powders could inhibit the generation of Ti-rich phase,The diffusion activation,energy of Ti into W decreased as the increase of vacancy concentration,indicating that the diffusion of Ti into W was promoted by introducing defects into W.After high-energy milling for 9h using the ball-to-powder weight ratio of 10:1,the micro-strain and the dislocation density in W powders were increased by 10 times and 100 times,respectively,The grain size was decreased by 50%.The diffusion of Ti into W was promoted by diffusing simultaneously along the dislocation and along volume at 900℃,which decreased the generation probability of Ti-rich phase The content of Ti-rich phase was decreased from 16.7%to 12.7%and the grains were also refined,the comprehensive physical properties especially the relative density was dramatically improved.The regulation of W powder combination of WTi alloy could inhibit the generation of Ti-rich phase.The W-10 wt.%Ti alloy prepared by hot-pressing sintering at 1200℃ using W powders milled for 9 h had a relative density of 92.0%,average grain size of 2.33 μm,Ti-rich phase of 12.1%.After a proper combination of W powders,the relative density of WTi alloy reached 99.2%,the content of Ti-rich phase was decreased to 7.9%and the grain size of WTi alloy was 159nm.The formation of Ti-rich phase was inhibited by improving the cooling rate from furnace cooling to water cooling.The content of Ti-rich phase of WTi alloys sintered at 1500℃ was decreased by 52.7%and grain size was decreased from 2.33μm to 0.67μm,respectively.And the nanohardness and elastic modulus increased.It proves that part of Ti-rich phase was formed due to the phase decomposition during cooling process.After cryogenic treatment,the relative density increased,the content of Ti-rich phase decreased,and the relative density and microhardness of W-Ti alloys increased.The content of Ti-rich phase decreased to 7.2%and relative density and microhardness was improved to 99.8%and 594 HV0.05,respectively,when treated at-196℃ for 2h for 1 time.After cryogenic treatment(the cryogenic temperature is-268.6℃)in magnetic field(the magnetic intensity is from 4T to 12T),the content of Ti-rich phase decreased and the relative density increased.Meanwhile,compared with the single cryogenic treatment,the cryogenic treatment of W-Ti alloys in magnetic field led to the obvious grain refinement,more uniform distribution of Ti-rich phase.Meanwhile,the Ti-rich phase deflected to the direction of magnetic field.The optimal magnetic sputtering powers for preparation of W-Ti films using the targets before or after cryogenic treatment were 200W.After cryogenic treatment of WTi target,the as-prepared films were smooth and compact,and the grains were finer and more uniform.The bonding strength between the film and substrate was obviously improved from 14N to 39N,and the failure temperature of barriers was 650℃～700℃,which was increased by 100℃. |
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