Influence of R.F. sputter parameters on the magnetic orientation of Co-Cr layers

Co-Cr layers for the perpendicular recording mode were deposited by means of RF-sputtering. The most important sputter parameters, i.e. the RF sputter high voltage VRF, the argon pressure Par and the substrate holder temperature Tsh, gave an optimum value for perpendicular orientation of the magnetization. The crystal structure is always hcp within the range of varied parameters and no other magnetic phases were observed. If the sputter parameters do not have optimum values an additional hcp compound with in-plane orientation of the c-axis is observed. This orientation causes an increase of the in-plane remanence S//= (Mr/Ms). Measurements of the substrate temperature Ts as an function of the various sputter parameters lead to the conclusion that an exclusive perpendicular c-axis orientation is only obtained at Ts~150oC. At other Ts established either directly by changing Tsh or indirectly by changing the sputter conditions an additional hcp compound with in-plane c-axis orientation appears. We concluded that Ts is the dominant parameter for sputtering CoCr layers.