System, method and apparatus for obtaining true roughness of granular media
View Patent ↗The true roughness of highly granular perpendicular media is measured by forming an inverse replica of the surface of the media. The invention enables AFM measurements of granular media valley depth to more consistently predict the corrosion performance of the media. A liquid resist is used to first replicate the media topography and form the inverse replica. The narrow valleys in the original media are precisely modeled as sharp peaks on the replica. The height of the peaks are readily measured with an AFM tip. The resulting image is a negative of the original surface.
1. A method of measuring a surface finish of a magnetic media, comprising:
(a) forming a magnetic media on a surface of a disk, the magnetic media having a topography with valley depths;
(b) placing the disk on a support with the surface facing up;
(c) applying a liquid to at least a portion of the surface;
(d) placing a substrate on the surface to cover at least a portion of the surface is wetted by the liquid;
(e) curing the liquid to form a solid;
(f) removing the substrate from the disk such that the solid remains on the substrate and defines an inverse replica of at least a portion of the magnetic media on the surface of the disk;
(g) measuring peak heights of the inverse replica to derive measurements of the valley depths in the topography of the magnetic media on the disk; and
(h) predicting a corrosion performance of the magnetic media based on the derived measurements of the valley depths in the topography of the magnetic media on the disk.
2. A method according to claim 1 , after step (f), further comprising the step of heating the substrate at about 75.degree. C. for about 5 minutes to complete the curing of the inverse replica.
3. A method according to claim 1 , wherein step (c) further comprises spreading the liquid over said at least a portion of the surface.
4. A method according to claim 1 , wherein the liquid is an acrylic-based liquid photo resist, and the magnetic media is perpendicular media.
5. A method according to claim 1 , wherein the substrate is a UV-transparent plastic substrate, and step (e) further comprises UV curing the liquid through the UV-transparent plastic substrate for about one minute.
6. A method according to claim 1 , wherein step (g) further comprises using AFM to measure a topography of the inverse replica instead of directly imaging the topography of the magnetic media on the surface of the disk.
7. A method according to claim 1 , wherein the topography of the magnetic media has features on the order of less than 10 nm in lateral width.
8. A method according to claim 7 , wherein the topography of the magnetic media comprises peaks and valleys having widths therebetween of about 2 to 5 nm, and an overall peak-to-valley measurement is no more than 5.5 nm.