POLE TIP RECESSION MEASUREMENTS ON THIN-FILM HEADS USING OPTICAL PROFILOMETRY WITH PHASE CORRECTION AND ATOMIC-FORCE MICROSCOPY

Pole tip recession in magnetic recording thin film heads contributes to spacing loss, which leads to a degradation in the readback signal. As manufacturers improve the performance of magnetic recording devices, this recession will become more significant to the performance of future products. Pole tip recession can be measured by several techniques, including stylus profilometry, optical profilometry, and atomic force microscopy. Stylus profilometry is generally not used since it has several problems in this application. In this study, good correlation was found between optical profilometry and atomic force microscopy measurements, provided that the optical measurements were corrected for phase shift. This is necessary because of the dissimilar materials in the thin film head. There are several methods for making this correction. One method is an analytical correction using known optical constants for the head materials. These constants should be well characterized as the measurements are quite sensitive to them. Overcoating the head with a thin film provides two other methods for getting around the material differences problem. However, these methods require an optimum film thickness. The film must be thick enough so that it behaves as a substrate, but not so thick that it fails to replicate the head.