Magnetic probe tips on MEMS cantilevers for perpendicular magnetic recording.

摘要

Actuating a magnetic force microscopy (MFM) tip using microelectromechanical systems (MEMS)-positioning technology promises to increase the magnetic data storage areal density. In such a system, the probe tip is primarily responsible for determining the resolution for both writing and reading. This work is focused on the design, the fabrication and material exploration and characterization of a sub-100 nm diameter permanent magnetic tip for use in a MEMS-actuated probe-based nonvolatile magnetic mass data storage system.;Design considerations for the probe tip include selection of the material from which the tip is created, selection of the manufacturing method used to create the tip and the associated geometry. For a variety of tip dimensions, the tip field distribution in space and the magnetic force are either calculated analytically using MATLAB or simulated using MAXWELL.;During the initial probe tip processing stage, a process flow for etching a TiCoWCr stack was studied for tip electron beam patterning. Then prototype probe tips were fabricated on MEMS cantilevers both on whole silicon wafers and on single CMOS chips, using a focused ion beam (FIB) to trim lithography patterned mircoscale coarse tips down to nanoscale tips.;Different magnetic materials were explored for a high crystalline anisotropy. Pt is added to Co to decrease the Co saturation magnetization slightly and increase the crystalline anisotropy significantly to enhance the perpendicular remnant magnetization of the thin films against demagnetization. Cr is added to CoPt to isolate the Co grains and decrease the saturation magnetization.;For characterization, the domain patterns of the microscale and nanoscale Co tips are imaged on a magnetic force microscope. The switching field of the nanoscale Co tips is measured by using MFM for imaging and VSM for magnetization. Measurement results show that the tip switching field is between 10 kOe and 11 kOe, close to the calculated value for a theoretic case.;Combined with a heat assisted recording technique, our probe storage scheme with this nanoscale Co probe tip can potentially achieve an areal density above 500 Gbit/in2.