STUDY OF SUBSTRATE BIAS EFFECT ON CORROSION SUSCEPTIBILITY SF THIN-FILM MAGNETIC DISKS BY ACCELERATED CHEMICAL-TESTS

In this study, the characteristics of two relatively fast pore decorat ion techniques used for studying corrosion susceptibility of thin film disks with the structure CoCrTa/Cr/NiP/AlMg are discussed. The first technique employs HCl vapor. Since the HCl vapor reacts with both the cobalt alloy and the NiP layers, it has the capability of revealing po res in the sputtered layers with different sizes and depths that have an opening at the disk surface. The other technique uses a concentrate d nitric acid solution. Because concentrated nitric acid reacts only e xtensively with the NiP layer, it is used to reveal the deeper pores i n the sputtered layers with depth reaching the NiP layer. The tests ar e used to study the corrosion susceptibility of thin film disks with d ifferent substrate bias voltages during growth of the magnetic and chr omium layers. By the use of these two accelerated chemical tests, the pinhole densities of sputtered films are found to decrease with increa sing bias due to ion bombardment on the growing film that densifies th e film structure. The porosity results obtained are compared with thos e conventional corrosion tests, including the environmental chamber te st and hot water ion extraction. Good correlation among the different tests has been established. (C) 1998 American Vacuum Society.