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Laser Texture Procedure for Glide Calibration Disclosure Number: IPCOM000015929D
Original Publication Date: 2002-Jul-11
Included in the Prior Art Database: 2003-Jun-21

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For some time it has been known that there is a difference in the PZT response of a glide head toward a metal calibration nanobump and a glass calibration nanobump of the same height. As the storage industry moves from metal AlMg substrate-based manufacturing to glass substrates, this PZT difference has caused concerns. The smaller PZT response of a glass nanobump primarily results from the smooth dome-like shape of the bump, relative to the "volcano-like" bump shape of an AlMg nanobump. The "rim" of the latter bump provides a significantly increased contact area with the glide head, relative to the smooth top of the glass nanobump. As a result, at a given fly height the glide head will "ring louder" (i.e., respond with greater PZT amplitude) when contacting a metal nanobump, compared to a glass nanobump of the same height. In attempting to transition from metal to glass, this discontinuous change in PZT response (for the same height bump) has caused calibration problems in correlating metal bumps to glass bumps. One solution to this amplitude difference problem occurs by creating a linear row, or "wall", of closely spaced nanobumps on a glass substrate; such that the resultant PZT amplitude response from a glide head is sufficient to permit continuous correspondence between metal and glass. Basically, due to the larger contact area, the PZT amplitude response of a glide head interacting with multiple closely spaced glass nanobumps is approximately equal to the PZT response from a single metal nanobump. By this method, metal/glass correlation problems are mitigated. The basic methodology is to use a glass-absorbing pulsed laser (typically, a CO2 laser) to create closely spaced nanobumps in a linear configuration. Details on using CO2 lasers to create glass nanobumps are contained in Ref. 1. With the disk to be irradiated and "bumped" attached to a linear translation stage, the disk is translated by microscopic distances between each successive bump-generating laser pulse. The resultant profile is a "mountain range" of glass nanobumps creating a glass "wall" with which the PZT glide head can interact. Figure 1 displays an interference microscope image of a 5-bump linear profile, with the spacing between each bump center being about 10 µm, and the wall height being about 20 nm. The wall profile in Fig. 1 is clearly evident. This profile was generated by creating a first bump, then translating the disk 10 µm in the radial direction, creating a 2nd bump at the new location, and so on, for five bumps. Cross-sectional profiles of these bumps are displayed in Fig. 2, with the transverse cross-section shown in the top part, and the longitudinal cross-section on the bottom. Fig. 1 Interference microscope image of Fig. 2 Cross-section profiles of the wall