Micromechanical structures for data storage

Abstract

Rapidly increasing demand for data storage continues to drive the storage industry in a primary technological trend: the areal data density of the stored information must also increase at a very high rate. Micromechanical structures are soon likely to be needed to accommodate the increased mechanical positioning precision necessary for reading and writing data, as the bit and track sizes continue to decrease. Furthermore, as one considers storage densities beyond magnetic or optical limits, micromechanical devices will be needed to extend storage capacity through the use of advanced recording mechanisms. A first example of micromechanical engineering for data storage is a microactuator used as the fine stage of a two-stage actuator to position a magnetic recording head. Using the microactuator, the head can be positioned more rapidly and precisely, than can be accomplished by a conventional voice coil motor-driven, single-stage actuator. This device is a lithographically-defined, high-aspect-ratio, electroplated structure which is electrostatically-driven. The fabrication process and mechanical characteristics are described for the device, which may have linear or rotary motion. A micromechanical scanning probe structure, which may represent the basis for future directions for data storage, is also described. An Atomic Force Microscope (AFM)-based probe device is used to generate and detect fine pits in a polymer storage medium, using a probe-heating laser and a motion-detection laser. An areal density of 25 Gb/in2 is achieved, along with a data reading rate of about 1 Mb/s. Key to this level of performance is the incorporation of an extremely low-mass (0.3 ng) AFM probe, having a spring constant of about 1 N/m. Probe fabrication and associated performance are given. © 1995 Elsevier Science B.V. All rights reserved.