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Evaluating the Shape of the Landing Zone Pattern and Contaminants on a Hard Disk / All-in-one system of optical, laser, and probe microscope capabilities provides seamless measurement from the millimeter to nanometer level.
Application
The magnetic head slider of a hard disk drive (HDD) makes light contact with the disk when it stops spinning. When the disk is spinning, the airflow of the disk causes the slider to float about 10 nm above the disk’s surface. Contaminants or scratches on the surface of the disk can disrupt the airflow causing the magnetic head to bump the surface and become damaged.
To increase the recording density on a magnetic disk, a smooth disk surface is needed. However, the smoother the surface, the more the head slider sticks to the disk’s surface when it stops spinning. This tendency means that more torque is required when spinning restarts, and this can cause damage to the disk surface. To solve this problem, a ring-like landing zone where a portion of the disk surface is roughened or patterned is included to keep the slider from sticking to the disk’s surface. Contaminants and landing zone patterns may both have nanometer-level irregularities that are so small that it is difficult to observe the shape or measure the irregularity’s height using brightfield observation.
The Olympus solution
Olympus' OLS4500 nano-search microscope provides the high-definition differential interference microscopy of a laser microscope as well as brightfield observation so users can clearly visualize minor irregularities on a hard disk’s surface and easily locate the target to be measured. In addition, the high-resolution laser microscope enables 3D measurement to measure the profile of irregularities with a height of several tens of nanometers. Seamlessly transfer the target area for probe microscopy without losing track of the measurement subject. The probe microscope is capable of capturing reliable nanometer-level height data for a subject with micron-sized width that would be difficult to measure even with laser microscopy. The profile evaluation of the same area using both the laser and probe microscopes integrated into this unit enables comparison of the data and the ability to select the best observation method for each subject.
1. Observing a landing zone dot pattern and contaminants using optical and laser microscopes
Laser microscopic intensity image
Objective lens 20X
Objective lens 100X
Laser microscope differential interference image
Objective lens 20X
Objective lens 100X
Differential interference image
Objective lens 20X
Objective lens 100X
2. Comparing data from laser microscopes and probe microscopes
Laser microscope image
Depth of the dot pattern: 0.032 um
Width of the contaminant: 0.382 um
Height of the contaminant: 0.115 um
Probe microscope data
Depth of the dot pattern: 0.033 μm
Width of the contaminant: 0.390 μm
Height of the contaminant: 0.142 μm
The data obtained with the probe microscope shows that the shape measurement of a contaminant of this size with a laser microscope cannot correctly capture the contaminant’s height because the size of the contaminant is close to the spot diameter of the laser (0.4 μm).
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