LOW-TEMPERATURE FORMATION OF BETA-SILICON CARBIDE

Silicon carbide thin films were deposited by unbalanced radio frequenc y (RF) (13.56 MHz) magnetron sputtering from a silicon carbide target in a pure argon discharge. Deposition parameters were 80 W RF target p ower, 1.6 x 10(-3) mbar argon pressure and 6 cm target substrate dista nce. As determined with energy and mass analysis, the flux of the film -forming particles (Phi(Si) + Phi(C) approximate to 0.6 x 10(15) cm(-2 ) s(-1)) consists of mainly neutral silicon and carbon atoms with typi cal energies of a few electronvolts. The flux of the plating particles (Phi(Si) + approximate to 1.5 x 10(15) cm(-2) s(-1)) is composed of a rgon ions with a well-defined energy of 24 eV. The low film growth rat e, in combination with a high flux ratio of plating argon ions to film -forming particles Phi(Ar) + /(Phi(Si) + Phi(C)) of about 2.5, shifts the temperature of the phase transition from amorphous silicon carbide to nanocrystalline silicon carbide from normally 1000 degrees C in th e case of plasma-enhanced chemical vapour deposition (PECVD) or chemic al vapour deposition (CVD) deposition techniques down to 420 degrees C . The films were characterized by measurements of the mechanical prope rties, e.g. hardness and stress, as well as X-ray diffraction (XRD) an d Auger electron spectroscopy (AES). Due to the crystallization at 420 degrees C the stress of the films is reduced from 6.3 GPa (at 60 degr ees C and for the amorphous phase) to approximately 0.8 GPa. The hardn ess is between 53 and 37 GPa. At higher plating energies (> 85 eV) the ion-plating-induced densification is diminished by preferential sputt ering of silicon and consequently stoichiometry and hardness are negat ively affected. (C) 1997 Elsevier Science.