Embedded dual coil fabrication process

Details Embedded dual coil fabrication process Embedded dual coil fabrication process

2000-08-24

2002-01-15

McPherson, John A. (Department: 1756)

Radiation imagery chemistry: process, composition, or product th

Imaging affecting physical property of radiation sensitive...

Making named article

C430S314000, C430S319000, C029S603140, C029S603150, C029S603180, C029S603250

Reexamination Certificate

active

06338939

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to read/write heads for reading and writing digital data to storage media such as magnetic disks. More particularly, the invention concerns a read/write head with a unique embedded planar dual coil structure, and a process for manufacturing such a head.
2. Description of the Related Art
In this modern information age, there is a tremendous volume of electronic data for people and computers to manage. The management requirements not only involve transmission, receipt, and processing of this information, but storage of the data as well. And, with more data to store, computer users are demanding extremely high capacity digital data storage devices. One of the most popular data storage devices is the magnetic disk drive system, also known as a “hard drive.”
In magnetic disk drives, one of the most critical components is the read/write head. Read/write head characteristics ultimately determine how densely, quickly, and accurately data can be written to magnetic disk media. As a result, engineers are continually developing better and better read/write heads. Two of the chief areas of focus in read/write head development are data storage density (“areal density”), and read/write speed. In this respect, one improvement in the signal storage ability of read/write heads has been the use of two write coils. This has been shown to significantly improve the strength and efficiency of the data storage.
FIG. 1
shows a partial cross-sectional view of an exemplary dual write coil read/write sensor
100
, with the slider's deposit end (“trailing”) being shown at
103
, and the air bearing surface shown
101
. The leading edge (not shown) resides in the direction
105
. The sensor
100
is built upon a slider
102
, beginning with an undercoat
104
. Upon the undercoat
104
lies a first shield
106
, known as “S
1
,” followed by first and second gap layers
108
,
110
. Between the gap layers
108
,
110
lies a magneto resistive (“MR”) stripe
107
. Upon the gap layer
110
lies a combination shield/pole
112
known as “S
2
/P
1
.” The shield
106
, MR stripe
107
, and shield/pole
112
cooperatively form a magneto resistive read head
113
of the read/write sensor.
A write gap layer
113
is built upon the shield/pole
112
, followed by an organic insulating layer
114
. Upon the insulating layer
114
is based a first write coil
116
, which includes a conductive coil embedded in an organic insulating material that is applied to fill the spacing between coil turns and separate the first coil layer from a second coil layer to follow. The second write coil
118
is layered on top of the first write coil
116
, and similarly includes insulating material applied to fill the spacing between coil turns. A second pole
120
, known as “P
2
,” lies atop the second write coil
118
. After fabricating the second write coil layer
118
and its insulation, a plating seed layer (not shown) is deposited, followed by a photo lithography process that defines the shape of the second pole
120
. The “track width” constitutes the width of the second pole
120
(in a direction perpendicular to the page depicting
FIG. 1
) at the air bearing surface
101
. Track width determines the track density on the disk where bits are written to and read from. The second pole
120
is protected by an overcoat layer
122
. The shield/pole
112
, write coils
116
/
118
, write gap
113
, insulation layer
114
, and second pole
120
provide the write head
123
aspect of the read/write sensor
100
.
One drawback of the sensor
100
is the severe topography created by the substantial height of the coil layers
116
,
118
and insulation layer
114
. This topography is severe because it presents a significant curvature beneath the pole
120
, instead of a normally flat surface. In a two coil layer structure with organic insulation, the height of this structure can be as great as ten microns. This great height makes it extremely difficult to define the second pole
120
, especially when a narrow track width is required, for the following reasons. The track width corresponds to the dimension of the second pole
120
in a direction perpendicular to the view of
FIG. 1
(i.e., into the page). When track width is extremely narrow, there is a high “aspect ratio,” defined as the ratio of the second pole's width (track width) to its length (from right to left in FIG.
1
). Normally, when track width is larger than the second pole's length, no difficulty is presented for creating the pole
120
with known photo lithography processes. However, with the dual coil structure of
FIG. 1
, the second pole
120
exhibits a high aspect ratio, rendering photo lithography difficult or impossible. Moreover, this difficulty increases dramatically with more severe topographies, especially with today's track widths, which are frequently in the submicron range. In some cases, this difficulty may be so great that fabrication of the desired write head may be impossible.
Another drawback of the arrangement
100
is the amount of organic insulation present in the head. As mentioned above, organic insulation is present around the write coils
116
,
118
as well as the insulating layer
114
. The organic insulating material is typically a polymeric material. During operation, the write head is heated from current passing the coils. Organic insulation has a lower thermal conductivity than dielectric materials in the head, such as silicon-oxygen and aluminum-oxygen based materials. This low thermal conductivity impedes heat dissipation, causing the temperature of the write head to increase. Increased operating temperatures have various undesirable effects, such as decreasing head life. Furthermore, due to the organic insulation's relatively high thermal expansion coefficient, the organic insulation responds to the heat by expanding more than the nearby layers of the head. This expansion may cause portions of the head to protrude from the normally flat air bearing surface
101
. With the head now enlarged by the protrusions, the head's effective flying height is smaller, and there is a greater danger of the head contacting the storage surface. Such contact may cause further heating of the head, or a disastrous head crash in extreme cases. To avoid head/disk contact, a higher flying height is necessary between the head and disk surface. However, with a higher flying height, signals stored by the write head are weaker, and require more surface area to safely store adjacent signals that are distinguishable from each other. Thus, the protrusion due to the presence of the organic insulation ultimately lowers the areal density of stored signals, diminishing the disk drive's storage capability.
In view of the foregoing, then, the structure and fabrication of known dual coil write heads present a number of unsolved problems.
SUMMARY OF THE INVENTION
Broadly, the present invention concerns an improved read/write head, including an embedded planar dual coil write structure. The head includes a shield layer, a shield/pole layer substantially parallel to the shield layer, and a pole layer substantially parallel to the shield and shield/pole layers. In one embodiment, one edge of the generally planar shield/pole layer reaches an air bearing surface of the head, and the opposite edge abuts a substantially coplanar planarization material. A circuitous channel spans the junction between the shield/pole and the planarization material twice, encircling a central “hub” (or “island”) of shield/pole and bordering planarization material. A write structure is located in this channel, called a “recess”, with the shield/pole and its portion of the embedded write structure covered by the pole layer.
The write structure includes first and second substantially coplanar multi-turn flat coils, where turns of the first write coil are interspersed with turns of the second write coil. Coil turns are substantially parallel to the shield/pole layer. The coils reside in the r

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