Nanotechnology - Fabrication and characterization of bit-patterned media beyond 1.5 Tbit/in2
Tolerance of process to exposure variation. SEM images of 30-nm-pitch dots before (a,b) and after (c,d) Co or Pd multilayer deposition. SEM images of HSQ posts exposed at the optimized dose of 30 fC per dot (a) and overdosed by three times higher dose at 90 fC per dot. Though the HSQ dots are of different sizes in (a) and (b), the resulting dots after magnetization (c) and (d) are almost identical in size due to shadowing effects during Co/Pd deposition. Insets show the possible cross sections of these structures.
We fabricated bit-patterned media (BPM) at densities as high as 3.3 Tbit/in2 using a process consisting of high-resolution electron-beam lithography followed directly by magnetic film deposition. By avoiding pattern transfer processes such as etching and liftoff that inherently reduce pattern fidelity, the resolution of the final pattern was kept close to that of the lithographic step. Magnetic force microscopy (MFM) showed magnetic isolation of the patterned bits at 1.9 Tbit/in2, which was close to the resolution limit of the MFM. The method presented will enable studies on magnetic bits packed at ultra-high densities, and can be combined with other scalable patterning methods such as templated self-assembly and nanoimprint lithography for high-volume manufacturing.
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