Characterization of sputter deposited W-Si-N coatings based on α-W structure

W-Si-N coatings based on α-W structure with thickness 1.8-3.0 μm were sputter deposited on silicon (100) substrates, and the effects of nitrogen partial flow rate, silicon target current, and substrate temperature on microstructure, chemical composition, stress, and hardness of the coatings were studied with XRD, XPS, SEM, AFM, optical interference and microindentation techniques. It is found that the coatings deposited at N2 flow rates 10 and 20 sccm (Ar: 10 sccm) without or with additional heating are composed of α-W, W5Si3, and amorphous Si3N4. Cross-sectional SEM shows that the coating fracture changes from columnar to smooth morphology, and the coating thickness increases with silicon target current. AFM reveals that roughness of the coatings decreases with silicon target current. The compressive stress is less than 3.5 GPa for all coatings. Hardness of the coatings is 30-45 GPa, with the maximum at silicon target current 0.8 or 1.2 A. The highest hardness of the coatings (45.4±5.2 GPa) is obtained for the coating with dense columnar structure in cross-section and with the largest W (110) interplanar distance.