Determining the optical constants of read-write sliders during flying-height testing

Area of Science:

• Materials Science
• Optical Engineering
• Metrology

Background:

• Flying-height testers for rigid disk drives use optical interferometry.
• Material phase change on reflection affects optical constants (n and k) of the slider.
• Accurate optical constants are crucial for precise flying height measurements.

Purpose of the Study:

• To develop an instrument for simultaneous in situ measurement of flying height and optical constants (n and k) of read-write sliders.
• To obviate the need for independent ellipsometry and avoid problematic retract calibration.

Main Methods:

• Utilized polarization interferometry to measure flying height and optical constants simultaneously.
• Employed a transparent glass substrate instead of a magnetic disk.
• Verified results using experimental techniques on laboratory samples and actual sliders.

Main Results:

• Achieved root-mean-square (rms) uncertainty of 0.04 for optical constants n and k.
• Resulting flying height uncertainties range from 3 nm at 250 nm to 0.5 nm at contact.
• Demonstrated the effectiveness of the in situ analysis method.

Conclusions:

• The developed instrument provides accurate and simultaneous measurement of flying height and optical constants.
• This method enhances precision in disk drive testing by eliminating external calibration steps.
• The technique offers a significant advancement in metrology for read-write slider dynamics.