Graded bevel tapered write pole design for field enhancement

The invention relates to the general field of perpendicular magnetic writers with particular emphasis on delivering more flux to the ABS (air bearing surface).

Tapered write gaps have been previously used to enhance field and field gradient, as shown in FIG. 1 . It is based on the fundamental principle of increasing the choke area around the neck region so that the sides of ABS 11 are not quite parallel but, instead, converge at an angle θ thereby providing gradual flux concentration to bring additional field to the ABS. Because of the slope of the main pole, the area A 2 behind the ABS is larger than the area A 1 at the ABS. So a larger ratio of A 2 to A 1 corresponds to more flux concentration at the ABS. Other elements shown in FIG. 1 include trailing shield 12 , write gap 13 , and main pole 14 .

As track widths narrow, still further enhancements are needed to this flux concentration approach. While steeper tapered write gap angles can increase A 2 /A 1 , the main drawbacks are the processing difficulty and too high a sensitivity of the ABS area A 1 to the ABS lapping position ‘aa’. If the taper angle θ is too large, a small displacement of ABS line ‘aa’, caused by the ABS lapping process, will result in a large change in both the ABS area and the physical width of the main pole. Therefore, methods for flux concentration are required that are not overly sensitive to changes in the angle at which the write gap lies relative to the ABS.

A routine search of the prior art was performed with the following references of interest being found:

In U.S. Pat. No. 6,621,659, Shukh et al. say “it is common to taper the pole from the larger width in the paddle region to a narrower width in the pole tip region at the ABS.” However, the form of the taper is different from that disclosed by the present invention. U.S. Pat. No. 7,151,647 (Sasaki et al—Headway) shows a yoke portion having a wide portion, a narrow portion, and a sloping flare portion and U.S. Patent Application 2006/0044677 (Li et al—Headway) teaches a plated bevel pole design where the top is wider than the bottom.

U.S. Pat. No. 7,193,815 (Stoev et al) shows an upper section of the write shield wider than the lower section. U.S. Pat. No. 7,116,517 (He et al) teaches a T-shaped pole tip. U.S. Pat. No. 7,133,253 (Seagle et al) discloses a tapered pole tip while U.S. Pat. No. 6,680,815 (Sasaki) shows a tapered write gap as part of their FIG. 9

It has been an object of at least one embodiment of the present invention to provide a perpendicular write pole that provides increased magnetic flux at the ABS.

Another object of at least one embodiment of the present invention has been to provide a process for manufacturing said write pole.

Still another object of at least one embodiment of the present invention has been to achieve the above objects without increasing the degree of taper of the pole at the ABS.

A further object of at least one embodiment of the present invention has been to render performance of the completed device insensitive to small variations of the precise location of the ABS relative to other parts of the structure.

These objects have been achieved by increasing the amount of write flux that originates above the write gap without changing the pole taper at the ABS. In a first embodiment, this is achieved by increasing the taper of the section above the write gap. In a second embodiment, this section is extended so that it overlaps the write gap laterally. In a third embodiment, a part of this section is brought closer to the ABS while keeping the main parts of the write pole and the trailing shield well separated, magnetically speaking.

FIG. 1 shows a tapered write pole of the prior art.

FIG. 2 shows a cross sectional view of the 1 st embodiment.

FIG. 3 shows a 3D view of the 1 st embodiment.

FIG. 4 shows a cross sectional view of the 2 nd embodiment.

FIG. 5 shows a 3D view of the 2 nd embodiment.

FIG. 6 shows a cross sectional view of the 3 rd embodiment.

FIGS. 7-8 show process steps to make the 1 st and 2nd embodiments respectively.

FIG. 9 shows the starting point for manufacturing the 3 rd embodiment.

FIGS. 10 and 11 show additional steps in the manufacture of the 3 rd embodiment.

We describe below three embodiments of the invention, presented as processes for manufacturing the invention while also serving to describe the invented structure:

It should be noted that the descriptions that follow below, along with their drawings, are written as though the bodies described there, including in some cases cantilever-like projections, have no external support. In reality, these bodies are embedded in one or more layers of insulating material (typically Al 2 O 3 ) which provide whatever mechanical support that is needed without influencing the performance of the device being portrayed. In the interests of simplifying both the descriptions and the figures, these supporting layers are not necessarily shown or mentioned.

FIG. 2 shows the first of the new configurations disclosed in the present invention to enhance flux concentration ratio A 2 /A 1 while still keeping the taper angle of the write gap unchanged. Compared to the prior art shown in FIG. 1 , main pole 14 taper is now formed from two layers, 14 and 25 .

To form layer 14 , a first trench, with sidewalls that slope at an angle θ to the vertical, is formed in a layer of insulation (not shown) to a first depth. This trench is now just filled (overfill followed by CMP) with a layer of material suitable for the main pole followed by a non-magnetic layer (for the write gap). The (filled) first trench is then covered with a second layer of insulation (also not shown). A second trench, whose floor is aligned with the roof of the first trench, is now formed in the second insulation layer, said second trench having sidewalls that slope at an angle greater than θ. The second trench is then just filled with the same material as the first trench, thereby forming layer 25 and completing formation of element 14 as seen in FIG. 7 .

This is followed by an angle-lapping step to form the appropriately sloped surface onto which non-magnetic write gap layer 13 is then deposited (as well as being simultaneously deposited onto the top surface of lower pole 14 ). The process concludes with the deposition and shaping of trailing shield 12 .

Thus top part 25 of layer 14 has a larger taper angle than bottom part 11 , which increases A 2 relative to A 1 without increasing the sensitivity of the ABS to the lapping angle. This is because, after tapered write gap 13 is formed, top layer 25 will be recessed from ABS 11 so that the larger taper angle will not change A 1 when ABS line ‘aa’ is moved.

FIG. 3 shows a 3D view of the structure after tapered write gap 13 has been formed.

FIG. 4 (cross sectional view) and FIG. 5 (3D view of FIG. 4 ) show the 2 nd embodiment of the invention. It differs from the 1 st embodiment in that newly added top layer 45 is not simply an extension of bottom layer 14 with a larger taper angle. Instead, layer 45 does not need to be tapered (although using a tapered shape here would still be within the scope of the invention) In FIGS. 4 and 5 we show element 45 as having a rectangular cross-section (our preferred shape) but as long as there is a net increase in the A 2 /A 1 ratio, the objects of the invention will have been met. In general, element 45 will be wider than the top of write gap 13 enabling the achievement of a larger A 2 /A 1 .

Process-wise the main departure from the first embodiment is that the second trench, also aligned with the first trench and also formed in the second insulation layer, extends outwards from the mouth of the first trench (typically up to about 0.2 to 0.5 microns in each direction) and has straight, as opposed to sloping, sides. As for the first embodiment, the second trench is then just filled with the same material as before, thereby completing formation of element 14 as illustrated in FIG. 8 .

The 3 rd embodiment takes a different approach from the previous two embodiments. Instead of changing the A 2 /A 1 ratio, a non-uniform write gap is formed. This is illustrated FIG. 6 which shows that extra non-magnetic layer 63 has been inserted between write pole 14 and trailing shield 12 . Thus, the write gap is narrower at the ABS and wider away from it. This reduces flux leakage from the main pole to the write shield. Consequently, for a given A 2 /A 1 , this larger separation of the main pole from the trailing shield results in more flux being delivered at the ABS, while the field gradient is unchanged since the write gap at the ABS is unchanged. FIG. 9 shows how non-magnetic layer 13 (the write gap layer) is made up of two connected parts, both of which lie on the upper surface of element 14 —a sloping part (on the left of the figure) and a level part (on the right).

The starting point for forming a write pole built according to the teachings of the third embodiment is similar to the point where, in the first two embodiments, layer 14 has been angle-lapped to provide a suitably tilted surface for layer 13 . After deposition of non-magnetic layer 13 , as seen in FIG. 10 , the non-uniform write gap can be formed by depositing 2 nd write gap layer 93 which is then patterned so that it terminates at a distance (typically between about 0.05 and 0.2 microns from the ABS. The process ends with the deposition and patterning pf layer 12 to form the trailing shield, as shown in FIG. 11 .