Study On Deposition And Electronic Property Of Ta AndTa-N Films

Ta-N thin films were deposited on Al₂O₃-based ceramic and glass substrates byDC magnetron reactive sputtering in N₂/Ar ambient with different N₂flow rates. Themicrostructure, surface morphology and chemical component evolution of Ta-N thinfilms were studied as a function of sputtering parameters and heat treatment procedure,and the effects of electrical properties of the films was also be studied. At the sametime, the diffusion barrier property and its failure mechanism of Cu/Ta-N/SiO₂/Si,Cu/Ta/Ta-N/SiO₂/Si and Cu/Ti/Ta-N/SiO₂/Si films were analyzedTa-N thin films deposited on Al₂O₃-based ceramic substrates grow with clustersand formed with single-phase, while the films deposited on the glass substratesformed with single-phase of Ta₂N grains and transformed into the films composed ofmulti-phase with the increase of the N₂/Ar flow ratio. At the same time, With increaseof the N₂/Ar flow ratio, the N/Ta ratio and the sheet resistance of Ta-N films increases,while the TCR shift to negative value. At the same N₂/Ar flow ratio, the electricalproperties of Ta-N films deposited on glass substrate were better than that of filmsdeposited on Al₂O₃-based ceramic substrates. As increasing substrate temperature, theN content in the films increases, and the Ta-N films shows the preferred orientation ofTaN（111） are transforms into the preferred orientation of TaN（200）, which all makethe sheet resistance and TCR increase. With the increase of the annealing temperature,the surface average roughness and grain size of the Ta-N films decrease, while thedensity of the Ta-N films increase. When the annealing temperature is higher than500oC, the phase of Ta₂N was identified, which makes the sheet resistance decrease.At the same time, with the increase of the annealing temperature, the O content in thefilms increase gradually. However, when the annealing temperature is higher than600oC, the oxidation of Ta-N films and the internal stress in the Ta-N films increaseabruptly which may lead to the Ta-N films crack.The experimental results show that the barrier properties against Cu diffusion arefirst increase and then decrease with the increase of the N₂/Ar flow ratio. The N₂/Arflow ratio of10%for the Ta-N single diffusion barrier layer with thickness100nmexhibited better thermal stability. After700oC/30min annealing, the sheet resistanceof Cu/Ta-N/SiO₂/Si increased abruptly, Cu3Si and Ta₂O₅appeared, which indicatedthat the barrier has already failed. The Ta/Ta-N double diffusion barrier layer provides good adhesion of Cu/Ta interface and excellent stability. The results showthat, After annealing at750oC/30min, the Ta/Ta-N double barrier layer began to losebarrier function because of Cu diffusion along Ta/Ta-N grain boundaries towards Si.,which causes Cu agglomeration on the surface of films.. Another, we fabricated andstudied Ti/Ta-N double diffusion barrier layer for the first time. The results showedthat the Cu films deposited on the Ti/Ta-N layer grew in the way of close-stack andthe agglomeration of Cu atoms was not seen on the Ti barrier after annealing. TheCu/Ti interface showed better adhesion than the Cu/Ta interface. At the same time,Ti showed better affinity to oxygen than Ta, which could restrain the oxidation ofTa-barrier oxidation. After annealing at700oC/30min, the Ta₂O₅phase was notobserved in the Ti/Ta-N bi-layer, which indicated that the Ti/Ta-N bi-layer caneffectively prevent the diffusion of Cu.. The Ti/Ta-N diffusion barrier layer canreduce surface aggregation of Cu atoms and restrain stress between Cu/Ti/Ta-Ninterface which induced void and electrical migration in the films. So the Ti/Ta-Nbi-layer can effectively improve the diffusion barrier property between Cu and SiO₂.