| 초록 |
Nano-scale fabrication becomes an essential process in various application fields of magnetic thin films such as MRAM, patterned media and spintronic device. The topographic patterning process, for example, IBE(ion beam etching) and RIE(reactive ion etching), fabricates the nano-structure by removing the unnecessary materials and inherently has drawbacks like etching damage, redeposition and planarity issue. Recently, there has been an attempt to avoid these setbacks by applying non-topographic patterning process for magnetic thin films. This pure magnetic patterning technology utilizes the irradiation or implantation of ions like He+, Ga+, Ni+ into the magnetic thin films in order to modify the magnetic properties. When Ga+ ions are irradiated with FIB(focused ion beam) system, it is possible to fabricate the magnetic thin films directly in nano-scale with the combination of the irradiation induced magnetic patterning and the direct nano-fabrication ability of FIB. In this presentation, we will show the irradiation effects of Ga+ ion on the magnetic properties of perpendicular magnetic recording media for DTR (discrete track recording) and patterned media applications. The perpendicular media was prepared on a glass substrate and its detailed structure was Glass/Ta 5 nm/CoFeZrNb 40 nm/Ta 3 nm/Ru 15 nm/Ru-O2 8 nm/Co73Pt27-TiO2 16 nm. The sample was then exposed to the 10 pA 30 keV Ga+ focused ion beam with different dose from 1 × 1015 ions/cm2 to 30 × 1015 ions/cm2. The exposed area was 3 × 3 ㎛2 and the change of magnetic properties were observed with the MFM(magnetic force microscopy). As Ga+ ion dose increased from 1 × 1015 ions/cm2 to 30 × 1015 ions/cm2, the perpendicular magnetic anisotropy was degraded and no longer observed above 20 × 1015 ions/cm2 dose. The deterioration of the perpendicular magnetic anisotropy and ferromagnetic properties can be attributed to the concentration profile change due to Ga+ ion implantation. |
