The present invention relates generally to the manufacture of components for magnetic storage drives, and more specifically to systems and methods for correcting read/write overlay errors in the manufacture of magnetic transducers for storage drives.
Modern and future magnetic storage drive platters need precise writer and reader lapping geometry control (e.g., less than or equal to about 3 nm for one sigma) for the magnetic transducers or sliders. Current reader to writer overlay alignment at wafer level, as measured by wafer fabrication, is insufficient (e.g., greater than 5 nm for one sigma). The measurement of overlay between successive patterned layers on a wafer is one of the most important process control techniques used in the manufacturing of integrated circuits and devices such as sliders. Overlay generally pertains to the determination of how accurately a first patterned layer (e.g., reader layer) aligns with respect to a second patterned layer (e.g., writer layer) disposed above or below it. Overlay is described in greater detail in U.S. Pat. No. 7,804,994, the entire content of which is incorporated herein by reference.
The “as printed” overlay sigma, as discussed above, results in the inability to meet both the reader and writer lapping height requirements. For example, if the desired reader height is obtained, then writer height is sacrificed and vice versa. Current lapping technology utilizes three axis correction. A first axis relates to the balance used to keep the row bar height on both ends equal during lapping cycle. A second axis relates to the bending of the bar in between the sliders positioned at the ends of the bar. A third axis relates to the tilting of the row bar to increase or decrease the writer removal relative to the reader removal. Various lapping technology including the third axis tilting of the row bar for correction is described in U.S. Pat. No. 7,681,303, the entire content of which is incorporated herein by reference.
Historically lapping tools have been designed such that great effort, thought, modeling and trial and error are invested to ensure the row bar does not twist during the lapping cycle due to bending, balancing and lapping shear forces. This is because it is thought to be well known that row bar twisting will compromise the reader/writer overlay.
Aspects of the invention relate to systems and methods for correcting read/write overlay errors in the manufacture of magnetic transducers for storage drives. In one embodiment, the invention relates to a system for correcting for overlay errors in row bars, the system including a twisting tool configured to receive and secure a row bar having an elongated rectangular block shape and including a plurality of magnetic transducers spaced apart along a length of the row bar, and where the twisting tool is configured to twist the row bar at a plurality of areas along the length of the row bar.
In another embodiment, the invention relates to a method for correcting for overlay errors in row bars, the method including measuring an overlay error at preselected positions along a length of the row bar, where the row bar includes an elongated rectangular block shape and a plurality of magnetic transducers spaced apart along the length of the row bar, where the overlay error is indicative of a variation from a parallel orientation of a reader layer and a writer layer of at least one of the plurality of magnetic transducers, twisting the row bar to substantially correct the overlay error, and lapping the row bar to substantially correct the overlay error.
Referring now to the drawings, embodiments of systems and methods for correcting read/write overlay errors in the manufacture of magnetic transducers using twisting tools are illustrated. The twisting tools receive and secure a row bar having an elongated rectangular block shape and a plurality of magnetic transducers spaced apart along the length of the row bar, where the twisting tools are configured to twist the row bar at various areas along the length of the row bar. In some embodiments, the twisting tools include a number of manual set screws for applying twisting forces at preselected points along the row bar. In several embodiments, the twisting tools are used in conjunction with a lapping tool and both tools are used to correct overlay error.
In some embodiments, the twisting tools include a number of automatically controlled servo motors or voice coils for applying the twisting forces at preselected points along the row bar, and one or more electronic lap guides for providing feedback on the overlay error during a lapping process. In a number of embodiments, the twisting tools include multiple planar segments for applying the twisting forces to the row bars. The sizes and shapes of suitable planar segments can vary. Methods for correcting read/write overlay errors in the manufacture of magnetic transducers can include measuring the overlay error at preselected positions along a length of the row bar, twisting the row bar to substantially correct the overlay error, and lapping the row bar to substantially correct the overlay error.
In operation, and referring now to
The row bar 102 is attached to the mounting face portion 116 of the force translation assembly 109 using adhesive tape. In several embodiments, the adhesive tape is a polyurethane adhesive tape. In other embodiments, the adhesive tape can be replaced with, or used in conjunction with, polyester hot melt, wax, two part epoxy, cyanoacrylate, or other suitable adhesive materials.
In the embodiment illustrated in
The controller 204 can activate one or more of the servo motors (SM1-SM5) to apply a twisting force on a portion of the row bar 206. Using the ELG measurements, the controller 204 can determine whether to apply additional twisting force or not. The controller 204 can also determine whether to apply the lapping tool 208 to the row bar 206 or not, and also the speed of the lapping tool 208. As the controller 204 gets feedback on the orientation and dimensions of the row bar 206 based on the ELG measurements, it can quantitatively determine whether it has substantially corrected a sufficient amount of overlay error in the row bar. In several embodiments, the lapping tool 208 also provides feedback information to the controller 204 regarding current operating conditions.
In one embodiment, the controller 204 is implemented as a software program executing on a general purpose or specialized personal computer. In other embodiments, the controller 204 is implemented in a programmable logic device/controller such as a FPGA, PLD, CPLD, or other suitable programmable logic device. In another embodiment, the controller 204 is implemented using one or more processing circuitry components that share information. In some embodiments, the controller includes a proportional integral derivative (PID) controller for using a feedback loop to control devices attached thereto.
In several embodiments, the row bar is mounted or attached to the twisting tool using an adhesive or other suitable means of attachment. The adhesive can be adhesive tape, polyester hot melt, wax, two part epoxy, cyanoacrylate, or other suitable adhesive materials. In a number of embodiments, the row bar includes one or more electronic lap guides (ELGs). In some embodiments, the process further includes wire bonding to one or more terminals of the ELGs. In a number of embodiments, the ELGs are configured to provide information indicative of a measurement of a dimension of the row bar (e.g., the amount of lapping having been applied in a particular direction, thereby providing a thickness measurement at a particular location or locations along the row bar).
In several embodiments, the process twists the row bar, and/or laps the row bar, by a preselected degree based on the ELG measurement information. In some embodiments, the process twists, and/or laps, the row bar at preselected positions having the overlay error. In several embodiments, the process twists the row bar using a twisting tool configured to twist the row bar at a plurality of areas along the length of the row bar (e.g., a twisting tool having a plurality of planar twisting segments each configured to impart a twisting force on the row bar).
In one embodiment, the process can perform the sequence of actions in a different order. In another embodiment, the process can skip one or more of the actions. In other embodiments, one or more of the actions are performed simultaneously. In some embodiments, additional actions can be performed.
While the above description contains many specific embodiments of the invention, these should not be construed as limitations on the scope of the invention, but rather as examples of specific embodiments thereof. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their equivalents.
This application is a divisional of U.S. application Ser. No. 13/537,018, filed on Jun. 28, 2012, having Attorney Docket No. T5662, and entitled, “SYSTEMS AND METHODS FOR CORRECTING READ/WRITE OVERLAY ERRORS IN THE MANUFACTURE OF MAGNETIC TRANSDUCERS FOR STORAGE DRIVES”, the entire content of which is incorporated herein by reference.
Number | Date | Country | |
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Parent | 13537018 | Jun 2012 | US |
Child | 15234989 | US |