Effects of chamber pressure on dielectric properties of sputtered MgTiO₃ films for multilayer ceramic capacitors

MgTiO₃ thin films were prepared by r.f. magnetron sputtering in order to prepare miniaturized NPO type MLCCs. MgTiO₃ films showed a polycrystalline structure of ilmenite characterized by the appearance of (110) and (202) peaks. The intensity of the peaks decreased with an increase in the chamber pressure due to the decrease of crystallinity which resulted from the decrease of kinetic energy of the sputtered atoms. The films annealed at 600°C for 60min. showed a fine grained microstructure without micro-cracks. The grain size and roughness of the MgTiO₃ films decreased with the increase of chamber pressure. The average surface roughness was 1.425~0.313 nm for MgTiO₃ films prepared at 10~70 mTorr. MgTiO₃ films showed a dielectric constant of 17~19.7 and a dissipation factor of 2.1~4.9% at 1MHz. The dielectric constant of the films is similar to that of bulk ceramics. The dielectric constant and the dissipation factor decreased with the increase of the chamber pressure due to the decrease of grain size and crystallinity. The leakage current density was 10^-5~10^-7 A/cm² at 200kV/cm and this value decreased with the increase of the chamber pressure. The small grain size and smooth surface microstructure of the films deposited at high chamber pressure resulted in a low leakage current density. MgTiO₃ films showed a near zero temperature coefficient and satisfied the specifications for NPO type materials. The dielectric properties of the MgTiO₃ thin films prepared by sputtering suggest the feasibility of their application for MLCCs.