Ion beam deposition of permanent magnet layers for liftoff processes

Thin film permanent magnet layers of Cr/CoCrPt were prepared by ion beam de position in a Vecco IBD-350 tool. The magnetic properties were measured as a function of deposition angle, deposition energy, assist energy, and the u nderlayer and permanent magnet thicknesses. It was found that higher deposi tion energies and angles (from normal) resulted in larger coercivities. Inc reasing the assist energy also helped increase the coercivity. The coercivi ties were in the range of 1400-2100 Oe depending on the deposition conditio ns, for a Cr-50 Angstrom/CoCrPt-250 Angstrom film. The squareness, S (the r atio of remnant magnetization to saturation magnetization) and M(r)t (remna nt magnetization and film thickness product) for these films were about 0.8 5 and 1.3 memu/cm(2), respectively. It was found that underlayers of Cr as thin as 25 Angstrom could be used, without significant degradation of magne tic properties. The coercivity had a broad peak between 100 and 200 Angstro m of CoCrPt, above which the coercivity gradually decreased. theta-2 theta x-ray diffraction measurements showed the presence of in-plane textures of (10 (1) over bar 0) and (11 (2) over bar 0) with the largest coercivity bei ng obtained when a strong (10 (1) over bar 0) peak is observed. The side-wa ll profile of the permanent magnet, measured after a liftoff process, was f ound to depend on the deposition angle. As the angle got larger (further aw ay from normal incidence), the side wall showed greater tapering. This is d ue to the increased effect of shadowing by the photoresist structure. The d irectional, collimated, nature of the deposition beam was found to aid the liftoff process, by avoiding step coverage of the liftoff structures. This significantly increased the ease of lifting off. By adjusting the depositio n angle, it is possible to tailor the process to provide optimum magnetic p roperties, coupled with good electrical contact. Thus. it was found that io n beam deposition is an attractive alternative to sputter deposition (physi cal vapor deposition), providing some important advantages over it. (C) 199 9 American Vacuum Society.