Effects of thermal annealing on structural and electrical properties of sputtered W–Ti thin films

• Published in: Surface & coatings technology Vol. 204; no. 12; pp. 2099 - 2102
• Main Authors: Petrović, S., Peruško, D., Gaković, B., Mitrić, M., Kovač, J., Zalar, A., Milinović, V., Bogdanović-Radović, I., Milosavljević, M.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15-03-2010; Elsevier
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Metals. Metallurgy; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Production techniques; RBS; Surface treatment; Surface treatments; TEM; Thermal annealing; W–Ti thin films; XPS; RBS; XPS; W–Ti thin films; Thermal annealing; TEM; Annealing; Electrical properties; Surface treatments; Photoelectron spectroscopy; Heat treatments; Sputtering; Thin films; Transmission electron microscopy; W-Ti thin films; Microstructure
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2009.09.048

In this work we have studied the influence of thermal annealing on the structural and electrical properties of W–Ti thin films, deposited on n-type (100) silicon wafers. The films were deposited by d.c. sputtering from a 90:10
wt.% W–Ti target, using Ar ions, to a thickness of ~
170
nm. After deposition the samples were annealed at 400 to 700
°C for 60
min, in a nitrogen ambient. Structural characterizations were performed by X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD) and transmission electron microscopy (TEM). A four-point probe was used for electrical characterization. It was found that the as-deposited films exhibit a polycrystalline structure in the form of columnar grains (20–50
nm in diameter). Only b.c.c. W phase could be registered in the films, while any presence of crystalline Ti was hindered in XRD and electron diffraction patterns. Annealing at up to 600
°C resulted in an increase of the mean grain size in the films, and a decrease of their sheet resistance. For these annealing temperatures we did not register any interaction at the W–Ti/Si interface. However, upon annealing at 700
°C, a progressed interaction between the film and the substrate occurred. Structural analyses suggest the formation of both W and Ti silicides. The estimated thickness of the formed metal-silicide layer is approximately 125
nm. Sheet resistance increased rapidly after annealing at 700
°C, because a large portion of the original metallic film was consumed in the reaction with silicon.