The invention relates to the general field of magnetic data recording with particular reference to dealing with the wide area track erasure problem.
In today's high density magnetic recording art, the number of tracks per inch (TPI) has been increasing rapidly. To avoid erasure of adjacent tracks during data writing and to shield the main writing pole fringing fields, a side shield (SS) was added. Recently, a wrap-around shield (WAS) writer comprising a trailing shield together with side shields, as shown in
There is, however, a problem associated with the side shield and WAS designs: wide area track erasure (WATE). When the writer is writing the data track, some percentage of heads can erase data several tracks away, usually after several cycles of write operation. WATE can occur from 1 to 10 μm away from the main writing pole location.
A routine search of the prior art was performed with the following references of interest being found:
In U.S. Pat. No. 7,538,976, Hsiao et al. teach a tapered trailing shield to prevent wide angle track erasure while in U.S. 2007/0230045, Hsiao et al. disclose recessed shield portions to prevent WATE. Guan et al. (Headway) show shields having recessed edges to avoid concentration of flux at the edges in U.S. Pat. No. 7,599,152. Okada et al. describe recessed shields to prevent leaking of the magnetic field in U.S. 2003/0026039. In U.S. 2009/0262464, Gill et al. disclose a wrap-around shield made of low-permeability material to reduce WATE while in U.S. 2007/0268623 Feng teaches a multi-layer pole structure to reduce WATE.
It has been an object of at least one embodiment of the present invention to provide a method for eliminating far-field WATE while still maintaining side shielding ability.
Another object of at least one embodiment of the present invention has been to describe a magnetic write head that embodies said method.
Still another object of at least one embodiment of the present invention has been to describe a process for the manufacture of said write head.
These objects have been achieved by moving all but the central section of the three shields (leading shield LS, side shield SS, and write shield WS) and, optionally, the top yoke, a short distance (typically between 0.02 and 0.05 microns) inwards i.e. further away from the recording medium than the ABS.
a. ABS view of general Proximity Shield Design (PSD)#1.
b. Cross-section view of PSD#1 outside of the PSD region (off main port center).
a. ABS view of PSD#.
b. Cross-section view of PSD#2 outside of the PSD region (off main port center).
a. ABS view of PSD#3 with non recessed region forming a straight bar across the top yoke.
b. Cross-section view of PSD#3 at the center line of the main pole.
c. Cross-section view of PSD#3 off the PSD region.
a. ABS view of PSD#4 with non recessed region conforming to the side and write gaps of the main pole.
b. Cross-section view of PSD#4 at the center line of the main pole.
The invention discloses a novel design (the proximity shield design or PSD) and processes to implement it. The purpose of the PSD is to completely eliminate far-field wide area track erasure or WATE. As discussed below in relation to
In this way the proximity magnetic shield will still continue to prevent fringe fields generated during write operations from reaching the recording medium while the increased distance of the recessed magnetic shields from the magnetic media will reduce any disturb fields originating in the recessed region to a low enough level to avoid accidental erasure.
The width of the proximity shield (PS) is in the range of 0.05-0.5 μm per side. For a track width of 0.05-0.1 μm, the proximity shield thus covers only 1 to 10 tracks per side, so all WATE peaks beyond the outer edge of the proximity shield will be eliminated. Additionally, the disk drive already has a build-in function which re-writes ˜10 adjacent tracks after some number of write cycles and/or on detection of signal degradation on adjacent tracks.
However, this adjacent track re-writing scheme alone cannot take care of the far-field WATE problem since it can occur anywhere from nearby to more than 100 tracks away. Also, the location of far-track WATE peaks can vary greatly from one head to another. In
Only the sections near the main pole are shown here. The full recessed region extends all the way to the outer edges of the LS, SS, and WS. The amount of recess depends on the detailed design requirements and process limitations to achieve the selected PSD. The typical minimum value is 5 nm. The greater the recessed amount, the less the chance of WATE caused by undesired magnetic activity in the LS, SS, and WS.
The first embodiment of the invention (PSD#1 shown in
PSD#2, shown in
PSD#3, shown in ABS view in
PSD#4, shown in ABS view in
A cross-sectional view of PSD#4 is shown in
Manufacture of the PSDs:
The two processes that we have employed to manufacture the preferred embodiments listed above are:
For the First Process:
Non-magnetic material 71 is deposited to replace the LS/SS/WS material that was removed near the ABS by ion milling, as illustrated in the top view of the main pole surface seen in
Note that since the non-magnetic material will be part of the ABS, its adhesion to the recessed magnetic shields may not be strong enough. This poses a reliability concern of cracking or of a small piece breaking loose and then falling into the disk drive environment and causing mechanical contact between the head and the recording media.
This problem has been solved by using the tapered PSD design illustrated in
For the Second Process:
Another method to realize the PSD design includes ABS trimming. At row bar level, after the head has been lapped, additional photo patterning and ion milling are applied as follows:
Photoresist is applied and patterned to protect the reader and the non recessed area while leaving the recessed area unprotected.
Etching is then performed at the slider level. After final lapping, the wafer is sliced into multiple rows, there being a number of heads per row. Each slider row is then aligned and internally bonded with its ABS facing up. After a photoresist mask has been applied to protect the proximity shield and reader, ion-milling or wet-etching process is used to remove at least 5 nm in the unprotected region so as to form the recessed region in the LS/SS/WS/Top yoke. After stripping the photoresist and cleaning, processing of the slider continues in the normal way.
Number | Name | Date | Kind |
---|---|---|---|
6785097 | Okada et al. | Aug 2004 | B2 |
7538976 | Hsiao et al. | May 2009 | B2 |
7599152 | Guan et al. | Oct 2009 | B2 |
7768741 | Feng | Aug 2010 | B2 |
8164853 | Hirata et al. | Apr 2012 | B2 |
20070230045 | Hsiao et al. | Oct 2007 | A1 |
20080112081 | Matono | May 2008 | A1 |
20090262464 | Gill et al. | Oct 2009 | A1 |
20110157746 | Hirata et al. | Jun 2011 | A1 |
20110216443 | Hirata et al. | Sep 2011 | A1 |
Entry |
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“Side-Track Erasure Processes in Perpendicular Recording,” by Shaoping Li et al., IEEE Transactions on Magnetics, vol. 42, No. 12, Dec. 2006, pp. 3874-3879. |
“High Density Perpendicular Recording with Wrap-Around Shielded Writer,” by Daniel Z. Bai et al, TMRC 2009, Paper B4, pp. 1-9, Manuscript received Aug. 24, 2009. |
“One Terabit per Square Inch Perpendicular Recording Conceptual Design,” by M. Mallary et al., IEEE Transactions on Magnetics, vol. 38, No. 4, Jul. 2002, pp. 1719-1724. |
Number | Date | Country | |
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20120127611 A1 | May 2012 | US |