GB2150317A - Process for producing negative pressure sliders using a photoresist - Google Patents

Abstract

A process for producing a negative pressure slider 20a having an air bearing flying surface 21a and supporting a magnetic head comprises the steps of: applying a layer of dry photoresist material to the slider 20a; using photolithography to pattern the photoresist layer so that a portion of the photoresist layer is removed to expose a portion of the surface of the slider 20a, the remaining portion of the photoresist layer comprising a protective layer 90a over the flying surface 21a of the slider; ion milling the exposed portion of the surface of the slider and the protective layer 90a to produce at least one negative pressure cavity 100a, 102a in the surface of the slider wherein the protective layer 90a protects the flying surface 21a during the ion milling step; and removing the protective layer 90a. <IMAGE>

Description

SPECIFICATION Process for producing negative pressure sliders This invention relates to processes for producing negative pressure sliders and to negative pressure sliders when made thereby.

Current magnetic disk drives employ spring biased air bearing sliders which rely on the fact that their low flying height above the surface of a disk can be achieved by an air bearing created between the slider and the rotating disk. The slider typically carries a magnetic read/write head at its trailing edge. The slider "floats" on the air bearing and its flying height is controlled by the external loading force of the spring bias on the slider. The flying height should be as low as possible to avoid loss of signal. With this type of slider, in order to decrease the flying height, the external loading force is increased.

This type of spring biased slider operates on a contact start/stop basis where the slider is physically in contact with the disk at the start of rotation of the disk and until the disk achieves a certain speed at which time the air bearing can be set up to lift the slider from the disk. As the disk comes to a stop, the slider returns to direct contact with the disk. Where the loading force is increased in order to lower the flying height, wear occurring between the surface of the disk and the slider during start and stop operations also increases. Frictional wear has been minimised by using what is known as a negative pressure slider. This type of slider utilises a negative pressure cavity on its air bearing surface to create a vacuum which pulls the slider toward the disk.Consequently, the slider can be suspended over the disk and biased away from the disk by a suitable suspension system. The air flow generated by the surface of the recording medium produces a negative pressure region, or partial vacuum, in the negative pressure cavity of the air bearing suface which pulls the slider against the force of the suspension system towards the disk.

Examples of such negative pressure sliders are shown in U.S Patent Specifications Nos. 3,811,856 and 4,141,049.

With this type of slider, the depth and configuration of the negative pressure cavity (or cavities) determines the flying height of the slider.

Consequently, the negative pressure cavity of the air bearing surface of the slider must be very accurately formed.

It is literally impossible to machine accurately and reproduceably a negative pressure cavity of the size and shape required. Some alternatives to machining the cavity are chemical etching, plasma etching, and ion beam milling.

In the past, it has been suggested that the negative pressure cavities can be ion milled using a metal layer mask to protect the air bearing surface of the slider while the negative pressure cavities are being milled. See, for example, IEEE Transactions on Magnetics, Vol. Mag. 16, No. 5, September, 1980, entitled "Floating Thin Film Head Fabricate by Ion Etching Method" by T. Nakanishi, et al.In an ion milling process which utilises a metal mask, generally the metal (usually chrome) is first sputtered onto the slider; photoresist is then spin-coated onto the slider; the photoresist is patterned to expose what will become the negative pressure cavity; the metal layer is then chemically etched out of the cavity; the photoresist is removed, the cavities are ion milled with the metal layer protecting the air bearing surface of the slider; and finally, the remaining portions of the metal layer are removed by chemical etching.

Various problems have been experienced in the use of the foregoing process. First of all, the requirement of sputtering and etching a metal layer increases the cost and complexity of the process, as well as the time required to complete the process. Furthermore, it has been quite difficult to accurately locate the negative pressure cavities on the slider. In addition, only relatively shallow cavities can be milled using this process in that the metal protective layer can withstand the ion milling operation only up to cavity depths of approximately four microns. As shown in the flying height versus cavity depth curve of Figure 1, which is typical for sliders having negative pressure cavities of the type shown in the present invention and in U.S.Patent Specifications Nos. 4,286,297 and 4,141,049, in order to achieve a flying height of 250 iim (10 microinches), the cavities must be fabricated to a depth of either 2 lim or 1211m. Since the curve has a greater slope at the 2 lim point than at the 12 Fm point, it is more desirable to fabricate the cavities to a depth of 12 pwm so that variations in the actual depth of the cavity will have a less dramatic effect on flying height. However, due to the limitations of the process described above, only relatively shallow cavities in the range of up to 4 m, for example, can be fabricated. See, for example, IEEE Transactions on Magnetics, Vol.

Mag. 15, No. 3, May 1979, entitled "Narrow Track Magnetic Head Fabricated by Ion Etching Method" by T. Nakanishi, et al, wherein the statement is made that "great etching depths cannot be obtained with the ion milling method".

The present invention seeks to provide a process for producing a negative pressure slider wherein (a) relatively deep negative pressure cavities can be ion milled to a precise depth of 12 S > m or more, while avoiding the necessity of applying a protective metal layer, (b) complexity and cost of fabrication as compared to prior processes is reduced and, (c) the negative pressure cavities are very precisely located on the slider to further control flying height and improve the performance of the slider.

Although the present invention is primarily directed to any novel integer or step, or combination of integers or steps, herein disclosed and/or as shown in the accompanying drawings, nevertheless, according to one particular aspect of the present invention to which, however, the invention is in now way restricted, there is provided a process for producing a negative pressure slider having an air bearing flying surface and supporting a magnetic head comprising the steps of: applying a layer of dry photoresist material to said slider; using pho tolithography to pattern said photoresist layer so that a portion of said photoresist layer is removed to expose a portion of the surface of said slider, the remaining portion of said photoresist layer comprising a protective layer over said flying surface of said slider; ion milling said exposed portion of the surface of said slider and said protective layer to produce at least one negative pressure cavity in the surface of said slider wherein said protective layer protects said flying surface during said ion milling step; and removing said protective layer.

Said magnetic head may include a pole tip disposed at said flying surface and in which during said photolithography step, a photolithographic mask is used to pattern said photoresist layer, said mask having an alignment pattern and an alignment mark, said alignment mark being aligned with respect to said pole tip to align said alignment pattern with respect to the surface of said slider.

Said alignment pattern may define said at least one negative pressure cavity to be milled into the surface of said slider, said alignment mark being aligned with said pole tip to align said alignment pattern on said slider. In one embodiment said alignment pattern is H-shaped, having a pair of parallel legs and a crosswise member disposed between said legs.

Preferably during said photolithography step, said alignment pattern is projected onto said photoresist layer to produce an H-shaped light pattern on said photoresist layer, said light pattern exposing said photoresist layer and defining said protective layer, and in which following said ion milling step said at least one negative pressure cavity comprises a first negative pressure cavity bounded by said crosswise member and the lower portions of said legs of said alignment pattern, and a second negative pressure cavity bounded by said crosswise member and the upper portion of said legs of said alignment pattern.

The alignment mark may be positioned within the lower portion of one of said legs of said alignment pattern, and said alignment pattern may be aligned with said pole tip during said photolithography step to align said alignment pattern on said slider.

In a preferred embodiment said slider carries two magnetic heads, each of said magnetic heads having one of said pole tips, said mask including one of said alignment marks disposed in the lower portion of each of said legs of said alignment pattern, each of said alignment marks being aligned with one of said pole tips during said photolithography step to align said alignment pattern on said slider.

Preferably a plurality of sliders are positioned adjacently between a first end slider and an oppositely disposed second end slider, said plurality of sliders comprising a slider bar, said mask including a plurality of said H-shaped alignment patterns positioned adjacently between a first end pattern and an oppositely disposed second end pattern, said first end slider including a pair of pole tips and said second end slider including a pair of pole tips, during said photolithography step each of said alignment marks of said first end pattern being aligned with one of said pole tips of said first end slider, and each of said alignment marks of said second end pattern being aligned with one of said pole tips of said second end slider simultaneously to align said plurality of alignment patterns of said mask on said plurality of sliders of said slider bar.

Said mask may include a first gross alignment window disposed outwardly from said first end pattern and a second gross alignment window disposed outwardly from said second end pattern, said slider bar having a first er, during said photolithography step, said first end is positioned within said first gross alignment window and said second end is positioned within said second gross alignment window to provide a gross alignment of said mask with respect to said slider bar before said alignment marks are aligned with said pole tips to provide for fine alignments of said mask with respect to said slider bar.

Preferably during said photolithography step said alignment marks of said first end pattern are symmetrically positioned with respect to said pole tips of said first end slider and said alignment marks of said second end pattern are symmetrically positioned with respect to said pole tips of said second end slider simultaneously to align said plurality of alignment patterns of said mask on said plurality of sliders of said slider bar.

During said ion milling step, said slider bar may be secured to a cooling fixture whereby said fixture and said slider bar are thermally cooled during said ion milling step. Said fixture may be arranged to rotate said slider bar during said ion beam milling step.

Said slider bar may have a trailing edge and wherein the lower portion of each of said legs of said H-shaped pattern extends beyond said trailing edge of said slider, said protective layer of photoresist extending beyond said trailing edge of said slider.

The process may include, following the removal of said protective layer, said slider bar undergoing a cutting step wherein each of said sliders is cut from said slider bar.

In the preferred embodiment during said ion beam milling step said at least one negative pressure cavity is milled to a depth of 12 Fm.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which: Figure 1 shows a flying height versus cavity depth graph for a negative pressure slider according to the present invention; Figure 2 is a perspective view of a slider bar prior to the formation of negative pressure cavities by a process according the present invention; Figure 3 shows the slider bar of Figure 2 supported by a process fixture; Figure 4 shows the slider bar being inserted into a photoresist lamination device; Figure 5 shows the slider bar after a photoresist layer has been applied, with a portion of the process fixture broken away; Figure 6 shows a photolithographic mask used in a process according to the present invention; Figure 7 shows a typical H-shaped pattern of the mask of Figure 6; Figure 8 shows an alignment pattern superimposed upon the slider bar;; Figure 9 shows an enlarged view of an H-shaped pattern superimposed upon one end of the slider bar; Figure 10 shows the slider bar after the photoresist layer has been patterned, with a portion of the process fixture broken away; Figure 11 shows an enlarged view of one end of the slider bar after the photoresist layer has been patterned and the slider cavities have been ion milled, with a portion of the process fixture broken away; Figure 12 shows the slider bar after the ion milling operation with the remaining portions of the photoresist layer removed; and Figure 13 shows a negative pressure slider produced by a process according to the present invention.

A process according to the present invention for producing a negative pressure slider is applied to a slider bar 10, shown in Figure 2, having a first end 12 and an oppositely disposed second end 14. The slider bar 10 has a leading edge 16, a trailing edge 18, and a trailing surface 19 normally disposed from edge 18. A plurality of adjacently positioned sliders 20a-20m are disposed between the ends 12, 14. Each slider is bounded by a pair of dotted lines 22a, 24a; 22b, 24b; 22c, 24c; etc., as shown. Once the slider cavities have been milled into the slider bar 10, as will be later described, the slider bar 10 will be cut along these dotted lines to remove the 13 sliders 20a-20m.The slider 20a comprises a first end slider and the oppositely disposed slider 20m comprises a second end slider with the sliders 20,b- 20/ comprising intermediate sliders. Each slider 20a-20m includes a pair of magnetic read/write heads (not shown) which are disposed adjacently to the trailing edge 18 of the slider bar 10. The magnetic heads are thin film heads and are applied by well known thin film technology to the trailing surface 19 of the sliders 20a-20m. Each magnetic head has a pole tip, or read/write gap, which is disposed at the flying surface of the associated slider.

For example, the slider 20a has pole tips 26a, 28a; the slider 20b has pole tips 26b, 28b; and so on.

The pole tip of the magnetic head is the portion of the head which flies most closely to the recording media and reads and/or writes on the media. The pole tips 26a-26m, 28a-28m, are visible to the eye once the slider bar has been secured in a projection aligner (not shown) and can be used for alignment of a photolithographic mask as will later be described.

The slider bar 10 can be comprised of Alsimag, FOTOCERAM (Trade Mark) or ferrite, for example.

Having described the slider bar 10, an embodiment of a process according to the present invention will now be described.

A layer of a suitable dry film photoresist such as DuPont de Nemours and Company's RISTON is first applied to the slider bar 10. To apply the photoresist to the slider bar 10, it is first placed in an aluminium process fixture 40, shown in Figure 3.

The slider bar 10 extends 25.4 F (1 mil) above the fixture 40 as shown. The slider bar 10 remains in the fixture 40 throughout nearly the entire process as will become apparent. Prior to applying the photoresist the slider bar 10 and the fixture 40 go through a prelamination bake step wherein the bar is heated to a surface temperature of 900C to improve adhesion of the photoresist. Following the pre-lamination bake step, the fixture 40 and the slider bar 10 are inserted between rollers 47, 48 of a roller laminating machine such as the DYNACHEM Model No. 120, manufactured by the Thiokol/Dynachem Corporation, Elmhurst, Illinois (Figure 4).The upper roller 47 pressure applies a sheet of dry film photoresist material 50 to the slider bar 10 so that a photoresist layer 54 adheres to the slider bar 10 as shown in Figure 5. The photoresist layer 54 is applied so that overlapping portions 56, 57, respectively, extend out over the leading and trailing edges 16, 18 of the slider bar 10. The portion 57 extending beyond the trailing edge 18 protects the thin film heads laminated to the trailing surface 19 of the slider bar 10 from the ion beam during the milling step (later described).

Once the photoresist layer 54 has been applied, the slider bar 10 and the fixture 40 are mounted in the workpiece holder of a projection alignment machine (not shown) such as a Cobilt Model No.

CA400A, manufactured by the Cobilt Corp., Sunnyvale, California. A photolithographic mask 60, shown in Figure 6, is placed in a mask holder of the projection aligner. The mask 60 is opaque except for an alignment pattern 64 which is transparent to ultraviolet light. The pattern 64 is comprised essentially of a plurality of equally spaced and adjacently positioned, identical H-shaped patterns 70a-70m which are disposed between the first end pattern 70a and the second end pattern 70m. The pattern 64 is completed by a first gross adjustment window 66 which is outwardly disposed from the first end pattern 70a, and a second gross adjustment window 68 which is outwardly disposed from the second end pattern 70m. A typical H-shaped pattern 70a-70m is shown in more detail in Figure 7.The H-shaped pattern, in the example shown the pattern 70a, is comprised of a pair of vertically running legs 71a, 74a which are connected by a horizontally disposed crosswise member 77a. The leg 71a has an upper portion 72a and a lower portion 73a. Likewise, the leg 74a has an upper portion 75a and a lower portion 76a. In the lowermost portion of the leg 71a, an alignment mark 80a is disposed.

Likewise, an alignment mark 82a is disposed in the lowermost portion of leg 74a as shown.

In order to align the pattern 64 upon the sliders 20a-20m of the slider bar 10, the slider bar 10 is first moved by a suitable positioning mechanism to position symmetrically the ends 12 and 14 of the slider bar 10 within the gross alignment windows 66, 68 of the pattern 64. (Alternatively, the mask 60 could be moved with the slider bar 10 being stationary.) Figure 8 illustrates this positioning of the slider bar 10 with respect to the pattern 64. Once this gross alignment has been made, the operator makes a fine alignment of the sliders 20a-20m with the pattern 64 by looking first at the first end pattern 70a and moving the slider bar 10 until the pole tips 26a, 28a of the slider 20a align with the alignment marks 80a, 82a of the first end pattern 70a (Figure 9). The pole tips 26a, 28a are visible to the eye.The marks 80a, 82a are properly aligned when they are vertically centered and symmetrically arranged with respect to the pole tips 26a, 28a as shown in Figure 9. To complete the fine alignment of the slider bar 10 with the mask 60, the operator next looks at the oppositely disposed second end pattern 70m and moves the slider bar 10 to align the pole tips 26m, 28m of the slider 20m with the alignment marks 80m, 82m of the second end pattern 70m in the very same way as shown in Figure 9. Once the pole tips of both the sliders 20a, 20m are aligned with the corresponding alignment marks of the sliders 70a, 70m, respectively, the fine alignment step is completed. By utilising the pole tips of the sliders 20a, 20m as reference points, the negative pressure cavities, later described, can be very accurately located on the sliders 20a-20m.

Having aligned the pattern 64 to the sliders 20a20m, ultra-violet light is now projected through the mask 60 to expose the H-shaped patterns 70a-70m onto the photoresist layer 54 of the layers 20a20m. Since we are using a negative resist photolithography process, the exposed H-shaped patterns are developed with the unexposed portions of the photoresist layer 54 being removed using 1.1.1 -trichloroethane low-pressure spray, for example. Therefore, at this point in the process, all that remains of the photo-resist layer 54 are thirteen Hshaped patterns 90a-90m, which are shown in Figure 10. Note that the legs of the H-shaped patterns 70a-70m overhang the leading and trailing edges 16, 18 of the slider bar 10.Overlapping portions 98 extending beyond trailing edge 18, protect the exposed portions of the magnetic heads (not shown) which are laminated onto the trailing surface 19 as previously discussed. The extension of the photoresist layer to cover the exposed portions of the magnetic heads is extremely important in that during the ion milling operation of the ions are projected at the slider bar 10 at an oblique angle of 45 -25 , for example, with respect to the surface of the slider bar 10. Consequently, the exposed portions of the magnetic heads would be milled if they were not protected.

Having patterned the photoresist layer, with the slider bar 10 still secured in the fixture 40, the fixture 40 is now secured in an ion milling machine such as a Model 10-1500-10 Ion Source machine manufactured by Ion Tech, Inc., Fort Collies, Colarado. The fixture 40 is rotated during the ion milling step to encourage uniform milling. Once the ion milling operation is in progress, the patterns 90a90m protect the directly underlying portions of the sliders 20a-20m from the milling while the negative pressure cavities are being milled to the proper depth. The milling time and ion accelerating voltage and ion current are chosen to mill the cavities to the desired depth. The portion of each slider directly underlying the patterns 90a-90m will comprise the air bearing flying surface of the completed slider.For example, the pattern 90a protects a flying surface 21a of the slider 20a (Figures 11 to 13). Figure 11 shows the slider 20a, at the completion of the ion milling step, with negative pressure cavities 100a, 102a milled to the proper depth. The cavity 100a is defined by the lower portions of legs 91a, 94a and a crosswise member 97a. The cavity 102a is defined by the upper portions of the legs 91a, 94a and the crosswise member 97a. While the cavities 100a, 102a of the slider 20a are being milled, cavities 100b-100m, 102b102m are, obviously, simultaneously being milled in the respective sliders 20b-20m. The ion milling of the slider bar 10 generates heat which must be dissipated from the slider bar 10 to protect the sliders 20a-20m from being overheated.In the present embodiment, the fixture 40 supporting the slider bar 10 is secured in the ion milling machine in such a way that it is water-cooled during the ion milling process to prevent overheating of the sliders 20a-20m.

Once the ion milling step is completed, the patterns 90a-90m can be removed by, for example, submerging the slider bar 10 first in an acetone bath and subsequently in an ultrasonic cleaning bath.

Following the removal of the remaining portions of the patterns 90a-90m, the slider bar 10 can be removed from the fixture 40 as is shown in Figure 12 wherein the thirteen sliders 20a-20m each have a pair of accurately located and formed negative pressure cavities 100a-100m and 102a-102m, respectively. The sliders 20a-20m can now be removed from the slider bar 10. To remove the slider 20a from the slider bar 10, a diamond abrasive wheel can be used to cut along phantom cut lines 110a, 112a (which correspond to the dotted lines 22a, 24a of Figure 2). Likewise, the remaining sliders 20b-20m would be removed by cutting at the phantom cut lines 110b-110m and 112b-112m, respectively. The flying surfaces 21a-21m can then be lightly lapped. The sliders 20a-20m can then be cleaned in acetone and in water to complete the process.

A typical slider 20a produced by the process is shown in Figure 13. The slider 20a has an Hshaped air bearing flying surface 21a and a pair of very accurately located and formed negative pressure cavities 100a, 102a. The pole tips 26a-28a of the slider 20a can now be moved over the recording surface at a precisely controlled flying height to optimize performance of the magnetic head.

In the presently preferred embodiment the material chosen for the slider bar 10 is Alsimag. The photoresist material, which is RISTON as noted, is applied at a thickness of approximately 48 Clam. The negative pressure cavities 100a-100m, 102a-102m are ion milled to a depth of 12 lim as noted. To accomplish the 12 iim milling depth using the Ion Tech Model 10-1500-200 model milling machine, an ion accelerating voltage of 120 volts together with an ion current of 125 milliamps is used for a period of 150 minutes. The ion milling beam is 10 cm in diameter. These parameters result in 1.9 watts/cm2 of power being dissipated at the surface of the slider bar 10. As noted above, the slider bar 10 is supported in a water cooling fixture to dissipate this heat.While the cavities 110a-110m, 112a-112m are being milled, the photoresist layer is also being milled. Approximately, 36 #m of the 48 um photoresist layer are milled away while the slider cavities are milled to a depth of 12 lim.

Typically, the milling angle of the ion beam is 45 with respect to the surface being milled. To avoid redeposition of the milled material on the milled surface, however, the milling angle can be varied. For example, with a slider bar of FOTO CERAM a milling angle of 25 prevents redeposition.

Hence, the above-described process provides for very accurate locating of the negative pressure cavities of the slider while also providing for precisely formed cavities, having a depth of 12 um as desired. Moreover, the process is greatly simplified over that used in the prior art in that the metal deposition and patterning step is eliminated.

Obviously, while the present embodiment shows thirteen adjacent sliders being simultaneously produced using the process of the present invention, other configurations of sliders could also be used with corresponding changes in the mask which is used to pattern the photoresist layer.

Claims (1)

1. A process for producing a negative pressure slider having an air bearing flying surface and supporting a magnetic head comprising the steps of: applying a layer of dry photoresist material to said slider; using photolithography to pattern said photoresist layer so that a portion of said photoresist layer is removed to expose a portion of the surface of said slider, the remaining portion of said photoresist layer comprising a protective layer over said flying surface of said slider; ion milling said exposed portion of the surface of said slider and said protective layer to produce at least one negative pressure cavity in the surface of said slider wherein said protective layer protects said flying surface during said ion milling step; and removing said protective layer.

2. A process as claimed in claim 1 in which said magnetic head includes a pole tip disposed at said flying surface, and in which during said photolithography step, a photolithographic mask is used to pattern said photoresist layer, said mask having an alignment pattern and an alignment mark, said alignment mark being aligned with respect to said pole tip to align said alignment pattern with respect to the surface of said slider.

3. A process as claimed in claim 2 in which said alignment pattern may define said at least one negative pressure cavity to be milled into the surface of said slider, said alignment mark being aligned with said pole tip to align said alignment pattern on said slider.

4. A process as claimed in claim 3 in which said alignment pattern is H-shaped, having a pair of parallel legs and a crosswise member disposed between said legs.

5. A process as claimed in claim 4 in which during said photolithography step, said alignment pattern is projected onto said photoresist layer to produce an H-shaped light pattern on said photoresist layer, said light pattern exposing said photoresist layer and defining said protective layer, and in which following said ion milling step said at least one negative pressure cavity comprises a first negative pressure cavity bounded by said crosswise member and the lower portions of said legs of said alignment pattern, and a second negative pressure cavity bounded by said crosswise member and the upper portion of said legs of said alignment pattern.

6. A process as claimed in claim 5 in which the alignment mark is positioned within the lower portion of one of said legs of said alignment pattern, and in which said alignment pattern is aligned with said pole tip during said photolithography step to align said alignment pattern on said slider.

7. A process as claimed in claim 6 in which said slider carries two magnetic heads, each of said magnetic heads having one of said pole tips, said masks including one of said alignment marks disposed in the lower portion of each of said legs of said alignment pattern, each of said alignment marks being aligned with one of said pole tips during said photolithography step to align said alignment pattern on said slider.

8. A process as claimed in claim 7 in which a plurality of sliders are positioned adjacently between a first end slider and an oppositely disposed second end slider, said plurality of sliders comprising a slider bar, said mask including a plurality of said H-shaped alignment patterns positioned adjacently between a first end pattern and an oppositely disposed second end pattern, said first end slider including a pair of pole tips and said second end slider including a pair of pole tips, during said photolithography step each of said alignment marks of said first end pattern being aligned with one of said pole tips of said first end slider, and each of said alignment marks of said second end slider pattern being aligned with one of said pole tips of said second end slider simultaneously to align said plurality of alignment patterns of said mask on said plurality of sliders of said slider bar.

9. A process as claimed in claim 8 in which said mask includes a first gross alignment window disposed outwardly from said first end pattern and a second gross alignment window disposed outwardly from said second end pattern, said slider bar having a first end outwardly disposed with respect to said first end slider and a second end outwardly disposed with respect to said second end slider, during said photolithography step, said first end is positioned within said first gross alignment window and said second end is positioned within said second gross alignment window to provide a gross alignment of said mask with respect to said slider bar before said alignment marks are aligned with said pole tips to provide for fine alignments of said mask with respect to said slider bar.

10. A process as claimed in claim 9 in which during said photolithography step said alignment marks of said first end pattern are symmetrically positioned with respect to said pole tips of said first end slider, and said alignment marks of said second end pattern are symmetrically positioned with respect to said pole tips of said second end slider simultaneously to align said plurality of alignment patterns of said mask on said plurality of sliders of said slider bar.

11. A process as claimed in any of claims 8 to 10 in which during said ion milling step, said slider bar is secured to a cooling fixture whereby said fixture and said slider bar are thermally cooled during said ion milling step.

12. A process as claimed in claim 11 but in which said fixture is arranged to rotate said slider bar during said ion beam milling step.

13. A process as claimed in any of claims 10 to 12 in which said slider bar has a trailing edge and wherein the lower portion of each of said legs of said H-shaped pattern extends beyond said trailing edge of said slider, said protective layer of photoresist extending beyond said trailing edge of said slider.

15. A process as claimed in any preceding claim in which during said ion beam milling step said at least one negative pressure cavity is milled to a depth of 12 im.

16. A process as claimed in any one of claims 1 to 7 in which during said ion beam milling step, said slider is secured to a cooling fixture, said slider and said fixture being thermally cooled during said ion beam milling step.

17. A process as claimed in claim 16 in which said fixture is arranged to rotate said slider during said ion beam milling step.

18. A process for producing a negative pressure slider substantially as herein described with reference to the accompanying drawings.

19. A negative pressure slider when made by the process as claimed in any preceding claim.

20. Any novel integer or s the present claim is within the scope of, or relates to the same or a different invention from that of, the preceding claims.