Ching-Hua Hsieh

Growth of (Ti,Zr)N Films on Si by DC Reactive Sputtering of TiZr in N 2 / Ar Gas Mixtures Effect of Flow Ratio

Titanium zirconium nitride [(Ti,Zr)N] films were prepared on Si substrates by dc reactive magnetron sputtering from a Ti-5 atom % Zr alloy target in N 2 /Ar gas mixtures. Material characteristics of the (Ti,Zr)N films were investigated by X-ray photoelectron spectroscopy, four-point probe, X-ray diffraction, atomic force microscopy, and cross-sectional transmission electron microscopy. According to those results, the deposition rate, chemical composition, crystalline structure, and film resistivity of the deposited films correlate with the N 2 /Ar flow ratio. The microstructure of the (Ti,Zr)N films was an assembly of very small columnar crystallites with a rock-salt (NaCI) structure and an enlarged lattice constant (over pure TiN). A minimum film resistivity of 59.3 μΩ cm was obtained at an N 2 /Ar flow ratio of 2.75, corresponding to near stoichiometric film composition [N/(Ti,Zr) = 0.96] and crystalline structure.

Characteristics of DC Reactively Sputtered (Ti,Zr)N Thin Films as Diffusion Barriers for Cu Metallization

(Ti,Zr)N films were prepared by dc reactive magnetron sputtering from a Ti-5 atom % Zr alloy target in N 2 /Ar gas mixtures and then employed as diffusion barriers between Cu thin films and Si substrates. Material characteristics of the (Ti,Zr)N film were investigated by X-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy (XTEM). The (Ti,Zr)N film microstructure was an assembly of Very small columnar crystallites with a rock-salt (NaCI) structure. Metallurgical reactions of Cu/(Ti,Zr)N 0 . 9 5 /Si, Cu/(Ti,Zr)N 0 . 7 6 /Si, and Cu/TaN 0 . 7 1 /Si were studied by X-ray diffraction and sheet resistance measurements. The variation percentage of sheet resistance for all Cu/barrier/Si systems stayed at a constant value after annealing up to 500°C for 30 min. However, the sheet resistance increased dramatically after annealing above 750°C for Cu/(Ti,Zr)N 0 . 9 5 /Si, and 500°C for both Cu/(Ti,Zr)N 0 . 7 6 /Si and Cu/TaN 0 . 7 1 /Si. For these samples, the interface deteriorated seriously and formationof Cu 3 Si was observed by XTEM. Our results suggest thai the refractory binary metal nitride film, (Ti,Zr)N, can be used as a diffusion barrier for Cu metallization as compared to the well-known TaN film.