Ultra-clean sputtering process for magnetic thin films on hard disk drives

A specialized multi-sputtering system is developed, which enables one to realize 10^-12 Torr order of the ultimate pressure, and to supply the ultra-clean processing gases. The extremely clean sputtering process (XC process) was realized by the reduction of out-gassing rate from the sputtering chamber and the purification of process gases at use point. The impurity level in the XC process is four orders less than that in the process normally used. Spin valve multilayers, Ta/Ni-Fe/Co/Cu/Co/Mn-Ir/Ta, with ultra-thin thickness were fabricated by using this system. Thin-film recording media, Cr/CoCrTa, were also fabricated by applying the ultra-clean sputtering process. The relation between the cleanness during film deposition process and their magnetic properties was discussed in connection with the changes of their microstructure. As results we found that: (1) the purification of the sputtering atmosphere facilitates the growth of grains, and reduces defects in the film; (2) the reduction of the grain boundaries, impurities, and defects in the XC processed spin valves results in the reduction of saturated resistivity and the enlargement of the magnetoresistance (MR) ratio; (3) the reduction of impurities, especially oxygen in the sputtering atmosphere, enhances the Cr segregation in a magnetic layer of thin-film media; (4) the formation of Cr segregated grain boundary structure reduces intergranular exchange coupling and results in the high coercivity of thin-film media.