Jae-Joon Choi

Construction of probe-based data storage with ultra-high areal density

Our probe-based data storage (PDS) system consists of four parts: signal processing module, multi-probe array, xy-planar actuator, and recording media. The signal-processing module has 2 layers attached to each other. The first layer has 3 D wiring, and it is assembled to the second layer (ASIC module) for the signal processing circuit. The multi-probe array is designed to increase recording and reading speed of the data bits. Each probe has cantilever and tip that are characterized by a tip height of 15 /spl mu/m, a tip radius of 15 nm, a natural frequency of 18.75 kHz and a DC sensitivity of 16.7 nm/V. Poly-silicon probe was fabricated by molding technique to produce high aspect ratio tips. The electrostatic planar actuator serves as a scanner that positions the probe to the right place by moving the media in xy-plane. The moving distance was /spl plusmn/40 /spl mu/m at 10/spl plusmn/10 V, DC gain was 3.04 /spl mu/m/V at 4 V, and the resonance frequency was 143 Hz. The: recording media stores the recorded information in the form of electric polarization in ferroelectric materials. Ferroelectric Pb(Zr,Ti)O/sub 3/ thin film is a candidate material for the media, and it can yield a memory density as high as 400 Gb/in/sup 2/ by recording bits as small as 35 nm in diameter. The bits are fully rewritable and retain the information for a generation at the temperature range below than 50 /spl deg/C.

Optimal design and fabrication of a rotary microactuator

The electrostatic rotary microactuators integrating optimally curved electrodes are proposed to enhance the actuating force-generation capability. In most conventional type of electrostatic microactuators using rotary mode, the electrodes have not been rigorously evaluated in terms of optimality for the shape and simply have adopted a straight shape. As a result, two neighboring electrodes should be spaced in the way of leading to relative large clearance at the far region from the center of rotation, hence the force generation capability is inherently limited. To overcome the limitation, the optimally curved electrode shape introduced by tilting the electrodes in a continuous manner along with the radius.

Optimally designed electrostatic microactuator for hard disk drives

The rotary electrostatic microactuators integrating optimally curved electronics are proposed to enhance the actuating force-generation capability. In most of the conventional type of electrostatic microactuators using rotary mode, the electrodes have not been rigorously evaluated in terms of optimality for the shape, but have simply been adopted in a straight shape. As a result, two neighboring electrodes should be spaced leading to a larger clearance at the outer region from the center of the rotation, hence the force generation capability is inherently limited. To overcome this limitation, the optimally curved electrode shape is introduced by tilting the electrodes in a continuous manner along with the radius. The simulation results show an enhanced capability over the conventional shape for the current application to a hard disk drive. Microactuators were fabricated with the aspect ratio of 4:45 by using the inductively coupled plasma reactive ion etching. Experiments results obtained indicate the increased capability of the proposed type.