Hiromitsu Tokisue

Slider dynamics during continuous contact with textured and smooth disks in ultra low flying height

Dynamics of a nano-slider during continuous contact with textured and smooth disks are studied using laser Doppler vibrometer, friction sensor, acoustic emission (AE) transducer and read back signal from a magnetoresistive head on the slider. When the slider contacts with the smooth disk, friction, AE signal and the amplitude of vibration show a steep increase, although the contact occurs at much lower flying height than the textured disk. Both pitch and roll vibration modes of the slider air bearing are strongly excited with the amplitude of about 10 nm. The pitch vibration results in the slider impacting the disk surface severely, which causes thermal asperities with extraordinary high amplitude.

Scratch–wear resistance of nanoscale super thin carbon nitride overcoat evaluated by AFM with a diamond tip

Abstract Atomic force microscopy (AFM) was used to investigate the scratch–wear resistance of ultrathin superhard carbon nitride overcoats of thickness 1, 2, 4, 6, 8 and 10 nm. When sliding against a diamond tip of radius less than 100 nm in the mode of line scratch, the thin overcoats of thickness 1–4 nm exhibited poor wear resistance, especially at contact pressures larger than 25 GPa, with a wear depth of 4 nm or larger and a specific wear rate up to 0.8×10 −4 mm 3 /nm. Non-contact mode imaging of a scratched surface has shown that a large amount of nanoscale wear debris was formed along the two sides of the scratched grooves, which indicated that the material removal mechanism of such thin overcoats was due to brittle fracture and abrasive wear, both in the nanoscale. In comparison, the overcoats of thickness 6–10 nm exhibited wear resistance with a specific wear rate less than 0.2×10 −4 mm 3 /nm. Instead, the least debris was observed on the scratched surfaces and only shallow grooves were left after scratching. It means that the grooves were formed by both plough and plastic deformation. The micro/nanowear mechanism and thickness effect of coating on scratch resistance were discussed.

Study on sofr-particle intrusion in a head/disk interface of load/unload drives

Soft-particle intrusion tests were carried out on load/unload drives. These tests show that to prevent particles intruding into a head/disk interface (HDI) the HDI must be designed with a minimum step height of the slider leading edge. Adhesion of particles to slider rail surface results in slider-disk contact. Even a light intrusion of particles into the leading edge step leads to a decrease both in flying height and the pitch of the slider.

Dependence of microstructure and nanomechanical properties of amorphous carbon nitride thin films on vacuum annealing

Abstract Three kinds of ultrathin amorphous carbon nitride films (α-CNx) with different internal stress were deposited on silicon (111) substrates by an ion beam assisted deposition method. The as-deposited α-CNx was post-annealed to eliminate the internal stress. The microstructure and nanomechanical properties of both as-deposited and annealed α-CNx were studied by using micro Raman spectroscopy, nanoindentation measurement, and nanoscratch test in atomic force microscopy. The Raman spectra of as-deposited and annealed film show that the ratio of intensities of the D band to G band increased after vacuum annealing. Nanoscratch tests showed that the elimination of compressive internal stress due to annealing resulted in reduced scratch resistance, while elimination of tensile internal stress due to annealing resulted in enhanced scratch resistance. Nanoscratch test results were in good agreement with the results of nanoindentation measurement. Experimental results indicate that the effect of internal stress on scratch resistance is stronger than that of microstructure evolution due to post-annealing. Nanoscratch tests show that suitable compressive internal stress is beneficial for enhancement of nanoscratch resistance of the thin α-CNx film.

Friction force of negative pressure sliders for proximity recording

We investigated the friction force between the trailing edge of the center pad or rail of negative pressure sliders and the textured disk surface as a function of flying height at reduced air pressure. In addition, we proposed the simple contact model and compared experimental friction force with calculated contact force to evaluate the influence of slider design parameters on the contact force. Results show that the contact force is significantly influenced by the pitch air-bearing stiffness, the distance between the pivot point and the contact point, and the interference pitch angle defined as the difference between the flying pitch angle on the smooth glass disk and the contact pitch angle on the textured disk.

Particulate-contamination-free wafer-handling systems for gas, liquid and vacuum environments used in a 64 Mbyte dynamic random-access memory process

Abstract Devices which establish particle-free wafer handling for gas, liquid and vacuum environments used in a 64 Mbyte dynamic random-access memory (DRAM) process were developed. A non-contact handler was developed as a handling device for use in a gas environment, such as air or nitrogen, which keeps wafers clean without touching them through the mutual action of gas suction and blow-out. Also, a non-contact gas levitation track was developed for use in a gas environment, which levitates, transfers and guides wafers without any contact using the fluid force of gas blow-out with a very low velocity. A liquid levitation transport track was developed for use in a liquid environment, which transports wafers without exposing them to atmosphere using the fluid forces of liquid jets. An electrostatic chuck was developed as a device for use in a vacuum environment which holds a wafer by a Coulomb attractive force. This electrostatic chuck is used as the hand of a wafer handler and the holding system of a wafer stage. These devices were applied to actual manufacturing processes and it was confirmed that they are effective for reducing wafer contamination. Automation of the manufacturing line in the 64 Mbyte DRAM process for the future is attempted with these devices.

Experimental Comparison of Load/Unload Slider Dynamics For Two Different Pico-Slider Designs

A comparison of Laser-Doppler vibrometry (LDV) and acoustic emission (AE) data is presented for two different slider designs during load/unload (L/UL). The behavior of the slider is measured for three different vertical load/unload velocities using a transparent glass disk with the slider flying at the bottom surface of the disk. The LDV laser spot can be positioned on the slider alrbearing surface during the complete load/unload process with the help of a so-called “periscope.” A characteristic velocity peak during unloading is observed that is caused by the slider pull-off force. Presented as a Society of Tribologists and Lubrication Engineers Paper at the STLE/ASME Tribology Conference in San Francisco, CA October 21–24, 2001

Oil-repellent treatment of a flying slider in a hard disk drive

The effectiveness of various oil-repellent treatments was evaluated by measuring the contact angles of mineral oil on the surface of a slider of a hard disk drive. The contact angle on an untreated slider was 20°; it was 51° on a slider dipped in FAS solution (2-(heptadecafluorooctyl)-ethyltrimethoxysilane) and heated to 393 K; 68° on a slider dipped in FASI solution (a octadecafluorooctane solution of FAS treated by hydrolysis and polymerization) and heated to 393 K; 80° on a slider vapor-deposited with FAS solution at 433 K; 80° on a slider dipped in FASI solution after ultraviolet radiation (UV) and heated to 393 K; and 81° on a slider irradiated by UV after being dipped in FASI solution. These results indicate that a compact coating of FAS can be formed, even on the slider surface of a carbon film with few hydroxyl groups, by treating the surface with FAS solution or FASI solution.

Effective refractive index method for frustrated total reflection: application to measurement of flying height

In order to measure the spacing between an actual magnetic disk and a slider, we developed a flying height sensor based on frustrated total reflection (FTR). When optically measuring the flying height of a slider, the phase shift on reflection at the magnetic disk is a significant problem. In this paper, we describe the theoretical treatment of the problem, introduce the modified effective refractive index method, and measure the effective refractive index of an actual magnetic disk. The flying height on a magnetic disk was also measured using the obtained effective refractive index. The result was compared with flying height measurements measured by the traditional interference method. They agreed with each other, with an error of less than 2.5 nm.

Flying height measurement using frustrated total reflection: determination of the reflectivities by the least-squares method

A new method for determining reflectivities in flying height measurement of a slider using frustrated total reflection (FTR) sensor is evaluated. The method is based on the fact that the reflectivity of FTR has different dependence on flying height for P-polarized light and S-polarized light. The flying height of a slider on a glass disk was measured both by an FTIP sensor using this method and by a traditional flying height tester. The results agree with each other with an error of less than 3 nm.