Apparatus for finishing a magnetic slider

A process for finishing a disc drive slider in which a pressure generator applies multiple pressures to the back surface of one slider while the front surface of the one slider contacts a lapping surface to form a finished front surface of the slider. The slider is part of a substrate having multiple unfinished sliders formed in it. An etch process is used to etch trenches in the substrate aligned between the sliders and to form webs joining the sliders together. After the sliders are finished by lapping, the webs are removed to separate the sliders. The multiple sliders are conveniently held together during the finishing process and the etching process avoids damage to the sliders.

FIELD OF THE INVENTION

The present invention relates generally to sliders for use in magnetic storage drives. In particular, this invention relates to methods and apparatus for finishing a disc drive slider that include lapping a surface of a disc drive slider.

BACKGROUND OF THE INVENTION

During the fabrication of magnetic heads for use in magnetic data storage applications, an array of transducers and auxiliary circuits are fabricated on a common substrate in a deposition of metallic and non-metallic layers. The array is then cut up into smaller bars, with each bar including a row of multiple read/write heads. The bars are then lapped to adjust an average stripe height (SH) of magnetoresistive (MR) transducers in the bar, the average throat height (TH) of inductive transducer in the bar, or both. The auxiliary circuits in the bars are electrical lap guides (ELGs) that sense the progress of the lapping process. Each electrical lap guide has an electrical resistance that increases as material is removed by lapping. Lapping is stopped automatically when the average stripe height and/or average throat height are within acceptable limits. After the lapping process is complete, the bars are cut up into individual read/write heads or sliders using diamond saws.

The process of lapping a solid bar has a limited ability to adjust only the average stripe height or average throat height for all the sliders formed in the bar. There are remaining undesired variations in individual stripe height or throat height among the sliders in a bar.

As higher recording densities are being introduced, there is a need for better control than this average control, particularly in the case of stripe height. It is, however, inconvenient and expensive to handle individual sliders in a lapping operation because of their small size.

A process and apparatus are needed that can handle bars of substrate with multiple sliders in each bar, while controlling lapping to individually or independently control stripe height for each slider.

SUMMARY OF THE INVENTION

Disclosed is a process and apparatus for finishing a disc drive slider. The slider is part of a substrate bar having multiple unfinished sliders formed in it. An etch process is used to etch stress-isolating trenches in the substrate aligned between the sliders and to form webs joining the sliders together. The apparatus includes a pressure generator that applies multiple pressures to the back surface of one individual slider while the front surface of the one individual slider contacts a lapping surface to form a finished front surface of the slider.

After the sliders are finished by lapping, the webs are removed to separate the sliders. The webs flexibly hold the multiple sliders together in a fixture during the lapping process while allowing the individual sliders to move independently. The pressures applied to each individual slider can be independently controlled, allowing for improved control of the stripe height (SH), the throat height (TH) or both of each sldier. The etching process avoids damage from the use of diamond saws.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In the present invention, a bar of multiple disc drive sliders has trenches etched between individual sliders using etching. The etching is controlled using a selective mask, and the etching is stopped before it completely cuts through the bar, leaving a web that keeps the sliders flexibly joined together for convenient handling during subsequent lapping operations. The use of etching avoids the use of diamond saws which can leave contamination in the form of chips and can also damage the sliders.

A pressure generator applies multiple pressures to the back surface of one individual slider while the front surface of the one individual slider contacts a lapping surface to form a finished front surface of the slider. The lapping can be automatically controlled by feedback from electric lap guides in the one slider being lapped. The slider being lapped is able to respond independently to the pressures applied to it because the trenches provide stress isolation between the individual sliders. The webs flex to allow the slider being lapped to move independently of adjacent sliders.

After the sliders are individually finished by lapping, the webs are removed to separate the sliders, preferably using masking and etching.

InFIG. 1, an embodiment of a disc drive100is illustrated. Disc drive100includes a disc pack126having storage surfaces106that are typically layers of magnetic material. The disc pack126includes a stack of multiple discs and the read/write head assembly includes a read/write transducer or slider110for each stacked disc. Disc pack126is spun or rotated as shown by arrow107to allow read/write head assembly112to access different rotational locations for data on the storage surfaces106on the disc pack126.

Read/write head assembly112is actuated to move radially, relative to the disc pack126, as shown by arrow122to access different radial locations for data on the storage surfaces106of disc pack126. Typically, the actuation of read/write head assembly112is provided by a voice coil motor118. Voice coil motor118includes a rotor116that pivots on axle120and an arm114that actuates the read/write head assembly112. Disc drive100includes electronic circuitry130for controlling the operation of the disc drive and transferring data in and out of the disc drive.

FIG. 2illustrates a substrate20in an unfinished condition including multiple unfinished disc drive sliders22arranged in a bar shape. Each disc drive slider22includes a front surface24which is lapped in a subsequent finishing process while pressure or force is applied to a back surface26(not visible inFIG. 2) of each slider22. Each disc drive slider22is formed from a slider substrate and various selectively deposited layers of materials that form a read/write head and electrical lap guides(s) in the deposited layers.

FIG. 3illustrates the substrate20with a selective masking layer26applied to the front surfaces24of the sliders22. The masking layer26is lithographically patterned to define masking grooves28which are not covered by the masking layer26. The masking layer26is formed of a material that is resistant to erosion by etching.

FIG. 4illustrates the substrate20after deep trenches32have been etched in substrate20using a microstructure etching process. Reactive ion etching (RIE), ion beam chemical dry etch, ion milling or other known microstructure etching (micromachining) techniques can be used. Etching processes are known, for example, from Handbook of Thin Film Technology, IOP Publishing Company 1997 (CD-ROM).

The position and size of trenches32are defined by the masking grooves28and aligned between the individual sliders22. A directional etching process is preferred in etching trenches32in order to accurately reproduce the masking grooves and etch deep trenches32. The substrate20can be formed of a single crystal material such as doped silicon. The etching process is stopped or controlled to etch trenches32only partially through the substrate20, forming webs34that join the sliders22together. Webs34are thick enough to hold the sliders22together during a subsequent lapping operation, and thin and flexible enough to allow each slider22to mover responsive to pressure somewhat independently of the adjacent sliders22.

FIG. 5illustrates the unfinished slider20with the selective masking layer26removed after the etching process is complete.

FIG. 6schematically illustrates a process of applying multiple pressures36to an unfinished slider22during a lapping process. InFIG. 6, a portion of the substrate20ofFIG. 5is illustrated with the same reference numerals being used inFIG. 6that are used in FIG.5. The bar-shaped substrate20made up of multiple unfinished sliders22joined together by webs34is placed between a lapping surface42and a multiple pressure generator38. Multiple pressure generator38generates multiple pressures36that are applied to the back side26of one of the sliders22as illustrated. Multiple pressures36can be each individually controlled based on electrical feedback46from an electrical lap guide controller or circuit44. Electrical lap guide controller44is connected to electrical lap guides (ELGs)40that are disposed in the unfinished slider22that is being lapped. The front surface24of the slider22is in contact with lapping surface42while controlled pressure is applied to back surface26. A finished front surface is formed by lapping at front surface24based on feedback from the electrical lap guides (ELGs)40. Feedback from the ELGs40controls the approach of the front surface24to the lapping surface42. The individual pressures36can be adjusted in real time to change the profile of pressure applied from front-to-back and left-to-right to vary the lapping rate in different regions of the front surface24. The stripe height (SH), the throat height (TH) or both of each individual slider22are precisely controlled using feedback from the electrical lap guides40. The electrical lap guides40are explained in more detail below in connection with FIG.9.

The multiple sliders22can be lapped independently of one another. This can be done sequentially with a single pressure generator38. While the lapping is going on at one slider22, the backsides of adjacent sliders22can be held by a fixture10with openings45that subject adjacent sliders22to a vacuum to conveniently hold the bar-shaped substrate20in place during the lapping operation.

Alternatively, the multiple sliders22can be lapped simultaneously using multiple pressure generators38and multiple ELG controllers44. When simultaneous lapping is done, the substrate20is held in place by mechanically engaging the webs34on an alternate mounting fixture with arms12inserted under the webs34as illustrated.

The webs34hold the sliders22together and each trench32stress-isolates each slider22from an adjacent slider22during the lapping. The webs34hold the sliders22together while the trenches32reduce transverse mechanical support of each slider22during the lapping.

After each of the sliders22in substrate20has been through the lapping process illustrated inFIG. 6, a finished substrate20as illustrated inFIG. 7results.

FIG. 7illustrates a finished substrate20including finished sliders23that include a finished (lapped) front surface25. The finishing of the sliders having been completed, the webs34are removed. Webs34can be removed by etching as illustrated in dashed lines in FIG.7.

FIG. 8illustrates a partial cross sectional view of a slider58with an inductive write transducer50and a layer66including a magnetoresistive (MR) transducer and electrical lap guides (ELGs). The cross sectional view inFIG. 8is perpendicular to a bottom surface60that is part of the lapped surface. The portion of the slider58that is illustrated is a portion near the trailing edge of the slider58. Slider58is formed on a substrate52in a conventional manner using thin film processing techniques. The inductive transducer50includes an inductive transducer throat62with a throat height64. Lapping of surface60(as described above in connection withFIG. 6) adjusts the height of the inductive throat62and also the height of a magnetoresistor and electrical lap guides in layer66. The arrangement of the magnetoresistor and electrical lap guides in layer66is explained in more detail below in connection with FIG.9.

FIG. 9illustrates a cross sectional view that is transverse to the view shown inFIG. 8of the layer66. Layer66includes a magnetoresistive transducer (MR)72and electrical lap guides70. As the bottom surface60is lapped (as illustrated in FIG.6), the stripe height74of the magnetoresistive transducer72changes, and also the electrical resistance of the electrical lap guides70changes as they are eroded away by the lapping process. When the desired lap depth is acheived at dotted line76as indicated by lap guide resistances, the lapping process is stopped. The stripe height74is controlled by the applied pressures during lapping as explained above in connection with FIG.6. The throat height (TH)64is also controlled or adjusted by the applied pressures during lapping.

In summary, a process for finishing a disc drive slider (22,23) is disclosed. A substrate (20) has multiple unfinished sliders (22) formed in it, each slider (22) has a front surface (25) and a back surfaces (26). An etch process is used to etch trenches (32) in the substrate (20), aligned between the sliders (22) and to form webs (34) joining the sliders (22) together. A multiple pressure generator (38) applies pressures (36) to the back surface (26) of one slider (22) while the front surface (24) of the one slider (22) contacts a lapping surface (42) to form a finished front surface (25). The webs (34) are removed to separate the finished disc drive sliders (26).

It is to be understood that even though numerous characteristics and advantages of various embodiments of the invention have been set forth in the foregoing description, together with details of the structure and function of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. For example, the masking and etching may vary depending on the particular application for the slider while maintaining substantially the same functionality without departing from the scope and spirit of the present invention. In addition, although the preferred embodiment described herein is directed to a slider for a disc drive, it will be appreciated by those skilled in the art that the teachings of the present invention can be applied to other systems, like tape drive and magneto-optical drives, without departing from the scope and spirit of the present invention.