U.S. patent application number 14/311155 was filed with the patent office on 2014-10-09 for method for manufacturing a magnetoresistive sensor using simultaneously formed hard bias and electrical lapping guide.
This patent application is currently assigned to HGST NETHERLANDS B.V.. The applicant listed for this patent is HGST Netherlands B.V.. Invention is credited to Shin Funada, Quang Le, Jui-Lung Li.
Application Number | 20140302441 14/311155 |
Document ID | / |
Family ID | 47389515 |
Filed Date | 2014-10-09 |
United States Patent
Application |
20140302441 |
Kind Code |
A1 |
Funada; Shin ; et
al. |
October 9, 2014 |
METHOD FOR MANUFACTURING A MAGNETORESISTIVE SENSOR USING
SIMULTANEOUSLY FORMED HARD BIAS AND ELECTRICAL LAPPING GUIDE
Abstract
A method for manufacturing a magnetic sensor using an electrical
lapping guide deposited and patterned simultaneously with a hard
bias structure of the sensor material. The method includes
depositing a sensor material, and patterning and ion milling the
sensor material to define a track width of the sensor. A magnetic,
hard bias material is then deposited and a second patterning and
ion milling process is performed to simultaneously define the back
edge of an electrical lapping guide and a back edge of the
sensor.
Inventors: |
Funada; Shin; (Pleasanton,
CA) ; Le; Quang; (San Jose, CA) ; Li;
Jui-Lung; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HGST Netherlands B.V. |
Amsterdam |
|
NL |
|
|
Assignee: |
HGST NETHERLANDS B.V.
Amsterdam
NL
|
Family ID: |
47389515 |
Appl. No.: |
14/311155 |
Filed: |
June 20, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13172739 |
Jun 29, 2011 |
8778198 |
|
|
14311155 |
|
|
|
|
Current U.S.
Class: |
430/319 |
Current CPC
Class: |
G11B 2005/3996 20130101;
G03F 7/20 20130101; G11B 5/3909 20130101; G11B 5/3169 20130101;
B82Y 10/00 20130101 |
Class at
Publication: |
430/319 |
International
Class: |
G03F 7/20 20060101
G03F007/20 |
Claims
1. A method for manufacturing a magnetoresistive sensor,
comprising: forming a magnetoresistive sensor having a first and
second hard bias layers comprising a magnetic material; forming an
electrical lapping guide comprising the same magnetic material as
the hard bias layers.
2. The method as in claim 1 wherein the hard bias layers and the
electrical lapping guide are deposited in a common deposition
process.
3. The method as in claim 1 wherein the sensor has a back edge and
the electrical lapping guide has a back edge and wherein the back
edge of the sensor and lapping guide are patterned in a common
lithographic process.
4. The method as in claim 1 wherein the sensor has a back edge, the
hard bias layers have a back edge and the electrical lapping guide
has a back edge, and wherein the back edge of the sensor and
lapping guide are patterned in a common lithographic process.
5. The method as in claim 4 wherein the back edges of the sensor
and hard bias layers are at a common location.
6. The method as in claim 1 wherein the sensor has a back edge and
a portion of the sensor extends beyond the back edge, and wherein
the electrical lapping guide has a back edge and wherein the back
edges of the electrical lapping guide and the sensor are formed in
a common patterning process.
7. The method as in claim 1 wherein the common patterning process
comprises forming a mask over the sensor and over the electrical
lapping guide and performing an ion milling to remove portions of
the sensor material and electrical lapping guide that are not
protected by the mask, the ion milling being terminated after the
ion milling has extended all of the way through the electrical
lapping guide and before the electrical lapping guide has extended
all of the way through the sensor.
Description
RELATED APPLICATIONS
[0001] The present Application is a Divisional Application of
commonly assigned patent application Ser. No. 13/172,739, entitled
METHOD FOR MANUFACTURING A MAGNETORESISTIVE SENSOR USING
SIMULTANEOUSLY FORMED HARD BIAS AND ELECTRICAL LAPPING GUIDE, filed
Jun. 29, 2011.
FIELD OF THE INVENTION
[0002] The present invention relates to magnetoresistive sensors
and more particularly to a method for accurately controlling a
stripe height of a sensor at very small sensor dimensions.
BACKGROUND OF THE INVENTION
[0003] The heart of a computer is an assembly that is referred to
as a magnetic disk drive. The magnetic disk drive includes a
rotating magnetic disk, write and read heads that are suspended by
a suspension arm adjacent to a surface of the rotating magnetic
disk and an actuator that swings the suspension arm to place the
read and write heads over selected circular tracks on the rotating
disk. The read and write heads are directly located on a slider
that has an air bearing surface (ABS). The suspension arm biases
the slider into contact with the surface of the disk when the disk
is not rotating, but when the disk rotates air is swirled by the
rotating disk. When the slider rides on the air bearing, the write
and read heads are employed for writing magnetic impressions to and
reading magnetic impressions from the rotating disk. The read and
write heads are connected to processing circuitry that operates
according to a computer program to implement the writing and
reading functions.
[0004] The write head includes at least one coil, a write pole and
one or more return poles. When a current flows through the coil, a
resulting magnetic field causes a magnetic flux to flow through the
write pole, which results in a magnetic write field emitting from
the tip of the write pole. This magnetic field is sufficiently
strong that it locally magnetizes a portion of the adjacent
magnetic disk, thereby recording a bit of data. The write field,
then, travels through a magnetically soft under-layer of the
magnetic medium to return to the return pole of the write head.
[0005] A magnetoresistive sensor such as a Giant Magnetoresistive
(GMR) sensor, or a Tunnel Junction Magnetoresistive (TMR) sensor
can be employed to read a magnetic signal from the magnetic media.
The sensor includes a nonmagnetic conductive layer (if the sensor
is a GMR sensor) or a thin nonmagnetic, electrically insulating
barrier layer (if the sensor is a TMR sensor) sandwiched between
first and second ferromagnetic layers, hereinafter referred to as a
pinned layer and a free layer. Magnetic shields are positioned
above and below the sensor stack and can also serve as first and
second electrical leads so that the electrical current travels
perpendicularly to the plane of the free layer, spacer layer and
pinned layer (current perpendicular to the plane (CPP) mode of
operation). The magnetization direction of the pinned layer is
pinned perpendicular to the air bearing surface (ABS) and the
magnetization direction of the free layer is located parallel to
the ABS, but free to rotate in response to external magnetic
fields. The magnetization of the pinned layer is typically pinned
by exchange coupling with an antiferromagnetic layer.
[0006] When the magnetizations of the pinned and free layers are
parallel with respect to one another, scattering of the conduction
electrons is minimized and when the magnetizations of the pinned
and free layer are antiparallel, scattering is maximized. In a read
mode the resistance of the spin valve sensor changes about linearly
with the magnitudes of the magnetic fields from the rotating disk.
When a sense current is conducted through the spin valve sensor,
resistance changes cause potential changes that are detected and
processed as playback signals.
[0007] The depth of the magnetoresistive sensor as measured
perpendicular to the air bearing surface is referred to as the
stripe height of the sensor. This stripe height is an important
dimension of the sensor and is defined by a lapping process that
removes sensor material until a desired air bearing surface
location has been reached. In order to determine when lapping
should be terminated, an electrical lapping guide can be used to
determine how far the lapping has progressed. However, certain
design structures, necessary to make a sensor workable at very
small sizes has rendered the construction and use of such lapping
guides inaccurate and unreliable. Therefore, there is a need for a
process that can allow the location of the air bearing surface (and
lapping termination point) to be determined with accuracy for a
very small magnetoresistive sensor.
SUMMARY OF THE INVENTION
[0008] The present invention provides a method for manufacturing a
magnetoresistive sensor that includes forming a magnetoresistive
sensor having a first and second hard bias layers constructed of a
magnetic material and forming an electrical lapping guide
comprising the same magnetic material as the hard bias layers.
[0009] The hard bias layers and the electrical lapping guide can be
formed in the same patterning and ion milling process. The sensor
and electrical lapping guide can be formed by depositing a sensor
material and then forming a first mask over the sensor material,
the first mask being configured to define a width of the sensor. A
magnetic material can then be deposited to provide hard magnetic
bias structures in the sensor region and to also provide a layer of
hard bias material in an electrical lapping guide region. Then, a
second mask is formed having a back edge configured to define a
back edge of a sensor in the sensor region and also having a back
edge configured to define a back edge of an electrical lapping
guide in an electrical lapping guide region. An ion milling can
then be performed to simultaneously define a sensor back edge and
an electrical lapping guide back edge.
[0010] The ion milling can advantageously be performed to remove
all of the exposed hard bias material to form a well defined
electrical lapping guide back edge, while leaving a portion of
exposed sensor material extending from the back edge of the sensor
as a sensor tail. This is possible because of the different
materials of the sensor and hard bias material (which makes up the
electrical lapping guide), which allows the ion milling to remove
the hard bias material at a faster rate than the sensor material.
This advantageously allows the AFM layer of the sensor to extend
beyond the stripe height for improved pinning strength, while
allowing the electrical lapping guide to be well defined for
improved stripe height definition during lapping.
[0011] In addition, because the hard bias material is more opaque
than the sensor material, the reflectivity problems associated with
the different substrates of the sensor and electrical lapping guide
(e.g. metal shield under sensor and alumina under the electrical
lapping guide) are no longer an issue to with regard to
photolithographic patterning.
[0012] These and other features and advantages of the invention
will be apparent upon reading of the following detailed description
of preferred embodiments taken in conjunction with the Figures in
which like reference numerals indicate like elements
throughout.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For a fuller understanding of the nature and advantages of
this invention, as well as the preferred mode of use, reference
should be made to the following detailed description read in
conjunction with the accompanying drawings which are not to
scale.
[0014] FIG. 1 is a schematic illustration of a disk drive system in
which the invention might be embodied;
[0015] FIG. 2 is an ABS view of a slider illustrating the location
of a magnetic head thereon;
[0016] FIG. 3 is an ABS view of an example of a magnetoresistive
sensor that might be constructed by a method of the present
invention;
[0017] FIG. 4 is a side cross sectional view of a sensor
constructed according to an embodiment of the invention;
[0018] FIG. 5 is a top down view of a sensor and electrical lapping
guide (ELG);
[0019] FIGS. 6A and 6B are side cross sectional views of a sensor
and an ELG respectively and illustrate problems associated with
prior art methods of forming a lapping guide; and
[0020] FIGS. 7-25 are view of a magnetic read head and electrical
lapping guide (ELG) in various intermediate stages of manufacture,
illustrating a method for manufacturing a magnetic head according
to an embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] The following description is of the best embodiments
presently contemplated for carrying out this invention. This
description is made for the purpose of illustrating the general
principles of this invention and is not meant to limit the
inventive concepts claimed herein.
[0022] Referring now to FIG. 1, there is shown a disk drive 100
embodying this invention. As shown in FIG. 1, at least one
rotatable magnetic disk 112 is supported on a spindle 114 and
rotated by a disk drive motor 118. The magnetic recording on each
disk is in the form of annular patterns of concentric data tracks
(not shown) on the magnetic disk 112.
[0023] At least one slider 113 is positioned near the magnetic disk
112, each slider 113 supporting one or more magnetic head
assemblies 121. As the magnetic disk rotates, slider 113 moves
radially in and out over the disk surface 122 so that the magnetic
head assembly 121 can access different tracks of the magnetic disk
where desired data are written. Each slider 113 is attached to an
actuator arm 119 by way of a suspension 115. The suspension 115
provides a slight spring force which biases slider 113 against the
disk surface 122. Each actuator arm 119 is attached to an actuator
means 127. The actuator means 127 as shown in FIG. 1 may be a voice
coil motor (VCM). The VCM comprises a coil movable within a fixed
magnetic field, the direction and speed of the coil movements being
controlled by the motor current signals supplied by controller
129.
[0024] During operation of the disk storage system, the rotation of
the magnetic disk 112 generates an air bearing between the slider
113 and the disk surface 122 which exerts an upward force or lift
on the slider. The air bearing thus counter-balances the slight
spring force of suspension 115 and supports slider 113 off and
slightly above the disk surface by a small, substantially constant
spacing during normal operation.
[0025] The various components of the disk storage system are
controlled in operation by control signals generated by control
unit 129, such as access control signals and internal clock
signals. Typically, the control unit 129 comprises logic control
circuits, storage means and a microprocessor. The control unit 129
generates control signals to control various system operations such
as drive motor control signals on line 123 and head position and
seek control signals on line 128. The control signals on line 128
provide the desired current profiles to optimally move and position
slider 113 to the desired data track on disk 112. Write and read
signals are communicated to and from write and read heads 121 by
way of recording channel 125.
[0026] With reference to FIG. 2, the orientation of the magnetic
head 121 in a slider 113 can be seen in more detail. FIG. 2 is an
ABS view of the slider 113, and as can be seen the magnetic head,
including an inductive write head and a read sensor, is located at
a trailing edge of the slider. The above description of a typical
magnetic disk storage system and the accompanying illustration of
FIG. 1 are for representation purposes only. It should be apparent
that disk storage systems may contain a large number of disks and
actuators, and each actuator may support a number of sliders.
[0027] FIG. 3 shows an example of a magnetoresistive sensor
structure 300 that could be constructed according to a method of
the present invention. The sensor structure 300 include a sensor
stack 302 that is sandwiched between first and second magnetic
shields 304, 306 that are constructed of an electrically conductive
magnetic material so that they function as electrical leads as well
as magnetic shields. The sensor stack 302 includes a magnetic
pinned layer structure 380, a magnetic free layer structure 310 and
a non-magnetic barrier or spacer layer 312 sandwiched between the
pinned layer structure 308 and free layer structure 310. The
non-magnetic layer 312 can be an electrically conductive spacer
layer constructed of a material such as Cu if the sensor 300 is a
giant magnetoresistive (GMR) sensor, and can be a thin electrically
insulating layer if the sensor 300 is a tunnel junction
magnetoresistive (TMR) sensor. In addition to the pinned and free
layer structures 310, 308, the sensor stack 302 can also include a
seed layer 322 for promoting a desired grain structure in the above
applied layers and a capping layer 324 at the top of the sensor
stack for protecting the sensor layers during manufacture.
[0028] The pinned layer structure 308 can be an antiparallel pinned
structure that includes first and second magnetic layers 314, 316,
which are antiparallel coupled across a non-magnetic coupling layer
such as Ru 318 sandwiched there-between. The first magnetic layer
314 is exchange coupled with a layer of antiferromagnetic material
(AFM layer) 320. This exchange coupling strongly pins the
magnetization of the first magnetic layer 314 in a direction
perpendicular with the ABS. Antiparallel coupling between the first
and second magnetic layers 314, 316 then pins the magnetization of
the second magnetic layer 316 in a direction opposite to that of
the first magnetic layer 314.
[0029] The free layer 310 has a magnetization that is biased in a
direction that is parallel with the ABS, but which can move in
response to a magnetic field, such as from the magnetic medium 112
(FIG. 1). Biasing of the magnetic free layer magnetization is
provided by first and second hard magnetic bias layers 326, 328,
which can be constructed of a high coercivity magnetic material
such as Co--Pt or Co--Pt--Cr. The hard bias layers 326, 328 are
each separated from the sensor stack 302 and from the bottom
shield/lead 304 by a thin, non-magnetic layer such as alumina
330.
[0030] As the size of the sensor decreases to accommodate higher
data density requirements, the magnetic stability of the pinned
layer suffers. In order to increase the stability of the
magnetization of the pinned layer structure 308, the pinned layer
structure 308 can be extended in the stripe height direction beyond
the stripe height of the free layer 310. This is illustrated in
FIG. 4 which shows a side, cross sectional view as seen from line
4-4 of FIG. 3. As can be seen, the upper portions of the sensor
stack 302 such as the free layer 310 and spacer layer and pinned
layers 308 extend to a stripe height SH as measured from the air
bearing surface (ABS). However, the lower portions of the sensor
stack 302 including the AFM layer 320 extend beyond this stripe
height SH, thereby forming a sensor tail 402 that greatly enhances
the robustness of the pinned layer structure 308. The region above
the tail 402 can be filled with a non-magnetic dielectric fill
layer 404 such as alumina.
[0031] As those skilled in the art will appreciate, the stripe
height of the sensor 300 is ultimately defined by a lapping guide
that is used to remove material until the ABS surface has been
defined. The sensor 300 is formed along with many thousands of
other sensors on a wafer. This wafer is then sliced into rows and a
lapping or grinding operation is performed (from the left as shown
in FIG. 4) until the location of the ABS has been reached. An
electrical lapping guide can be used to determine the point at
which the lapping operation should be terminated.
[0032] FIG. 5 shows a top down view of a portion of a wafer 502. As
can be seen, the wafer includes a sensor stack 302 formed thereon
and an electrical lapping guide 504 formed thereon. The lapping
guide 504 is connected with electrically conductive leads 506, 508.
The lapping guide 504 is constructed of a material that is
electrically conductive but, which has an electrical resistance
that can be measured across the leads 506, 508. During manufacture
a lapping operation is performed to remove wafer material from the
direction as indicated by arrows 510. It is desired that the
lapping operation be terminated when the desired air bearing
surface plane (ABS) is reached.
[0033] It can be seen that as the lapping operation reaches the
lapping guide 504, the lapping guide material will be removed,
which will in turn increase the electrical resistance of the
lapping guide. When the electrical resistance of the lapping guide
reaches a predetermined resistance value (indicating that the ABS
plane has been reached) the lapping can be terminated. In order to
ensure that the shape and location of the lapping guide 504
corresponds accurately with the sensor 302 (and more importantly
that the back edge 512 is accurately located relative to the back
edge 514 of the sensor 302) both the lapping guide 504 and sensor
302 can be defined in a common photolithographic masking and
milling process that defines both the sensor and lapping guide. In
this way there is no problem with misalignment between masks.
[0034] However this method of defining the lapping guide does
present some challenges, which can be better explained with
reference to FIG. 6. As will be recalled from the discussion of
FIG. 3, the sensor layers 302 are deposited on top of a magnetic
shield 304. This shield can be a material such as CoFe or NiFe.
However in the ELG area, the sensor material that makes up the ELG
504 in FIG. 6A is formed on top of an alumina (Al.sub.2O.sub.3)
fill layer 602 and not the shield structure 304. Because the sensor
material in both regions 302, 504 is not entirely opaque, the
different reflectivities of the underlying layers 304, 602 affect
the photolithographic process used to define the back edges 604,
606. This causes an undesirable misalignment of the back edges 604,
606, which in turn leads to inaccurate definition of the ABS
location and variation in the stripe height SH of the sensor stack
302 (FIG. 4).
[0035] Another problem arises as a result of the sensor tail 402
discussed previously with regard to FIG. 4. Because the ELG 504 is
formed (at least partially) of the same material that makes up the
sensor stack 302, the processes used to form the sensor 302 with a
tail 402 also result in an ELG 504 having a corresponding tail 604.
While the tail 402 on the sensor is desirable for maximizing
pinning robustness, the tail 604 on the ELG 504 is undesirable in
that it reduces the effectiveness of the ELG in accurately
determining the distance to which lapping has progressed with
regard to the sensor stripe height SH.
[0036] The present invention, as described herein below, overcomes
both of these challenges to form an ELG by a process that is does
not have lithographic patterning issues with regard to differing
reflectivities in the sensor and ELG areas and that also allows the
sensor to be formed with a tail for improved pinning, while forming
the ELG with no such tail for improved lapping measurement.
[0037] A method for manufacturing a magnetoresistive sensor
according to an embodiment of the invention is described with
reference to FIGS. 7 through 25. With particular reference to FIG.
7, a substrate 702 such as alumina (Al.sub.2O.sub.3) is provided,
preferably with a planar upper surface. An electrically conductive,
electroplating seed layer 704 is deposited over the substrate 702
by a process such as sputter deposition or some similar method.
Then, an electroplating frame mask 706 is formed having an opening
that is configured to define a magnetic shield on which a
magnetoresistive sensor can be formed. A magnetic material 708 such
as CoFe or NiFe is then electroplated into the opening in the mask
706, leaving a structure such as that shown in FIG. 7.
[0038] Then, with reference to FIG. 8, a non-magnetic fill layer
802 such as alumina is deposited. A chemical mechanical polishing
process can then be performed to remove portions of the fill layer
802 that extend over the magnetic shield material 708 and to
planarize the structures 708, 802, leaving a structure such as that
shown in FIG. 9. FIG. 10 shows a top down view of the structure of
FIG. 9, and shows a possible shape of the shield 708 in a sensor
region of the wafer on which the materials are deposited.
[0039] Then, with reference to FIG. 11, a series of layers of
sensor material 1102 is deposited. The sensor material 1102 can
correspond to the layers of the sensor stack 302 described above
with reference to FIGS. 3 and 4, but could include other layers or
types of sensors as well. Then, with reference to FIG. 12, a series
of first mask layers 1200 are deposited. The mask layers can
include a hard mask layer 1202 formed directly over the sensor
material 1102. The hard mask can be a material such as carbon or
diamond like carbon (DLC). An image transfer layer 1204 can be
deposited over the hard mask layer 1202 and can be constructed of a
soluble polyimide material such as DURIMIDE.RTM. and can be a
material that can function as an antireflective coating as well as
an image transfer layer. The mask layers also include a photoresist
layer 1206 deposited over the image transfer layer. An optional
upper hard mask (not shown) can optionally be deposited between the
image transfer layer and the photoresist layer, depending on design
conditions. The photoresist layer 1206 is photolithographically
patterned and developed to form it with openings in a sensor area
for defining a sensor track width (and also a location of hard bias
layers) and in an Electrical Lapping Guide (ELG) area for defining
a location of a for providing a location for lapping guide material
as will be seen. FIG. 13 shows a top down view as seen from line
13-13 of FIG. 12 and better shows a possible configuration of the
openings in the photoresist mask 1206. In FIG. 13, the dashed line
indicates the location of the shield material 708 hidden beneath
the mask hard mask and image transfer layers 1202, 1204. After the
photoresist layer 1206 has been patterned as described above, a
process such as Reactive Ion Etching (RIE) can be performed to
remove portions of the image transfer layer that are not protected
by the mask 1206 to transfer the image of the photoresist mask 1206
onto the underlying image transfer layers 1204, 1202, and leaving a
structure such as that shown in FIG. 14.
[0040] Then, with the mask layers 1204, 1206 as shown in FIG. 14,
an ion milling is performed to remove portions of the sensor
material 1102 that are not protected by the mask layers 1204, 1206,
leaving a structure such as that shown in FIG. 15.
[0041] With reference now to FIG. 16 a thin layer of dielectric
material 1602 is deposited. This layer 1602 is preferably alumina
and is preferably deposited by a conformal deposition process such
as atomic layer deposition. Then, a layer of hard magnetic material
such as CoPt or CoPtCr 1604 is deposited over the thin insulation
layer 1602. The hard bias layer 1604 can also include one or more
seed layers and/or a capping layer which are not shown here for
purposes of clarity. A layer of material that is resistant to
chemical mechanical polishing (CMP stop layer) 1606 is deposited
over the hard magnetic material 1604. The CMP stop material 1606
can be carbon or diamond like carbon (DLC).
[0042] A chemical mechanical polishing can then be performed,
stopping at the hard mask layer 1202 and CMP stop layer 1606,
thereby leaving a planarized structure as shown in FIG. 17. A quick
reactive ion etching can then be performed to remove the remaining
hard mask 1202 and CMP stop layer 1606, leaving a structure as
shown in FIG. 18. FIG. 19 shows a top down view of the structure of
FIG. 18. The shield 708 is shown in dashed line to indicate that it
is hidden beneath the sensor material 1102 and hard bias material
1604. As can be seen in FIG. 18 the above processes result in hard
bias material being formed in a sensor region 1902 and also in an
ELG region 1904 removed from the sensor region 1902 to some
extent.
[0043] With reference now to FIG. 20, a second series of mask
layers 2001 is deposited and can include a CMP resistant hard mask
2002 such as carbon or diamond like carbon, an image transfer layer
2004 that can be a soluble polyimide material such as
DURIMIDE.RTM., and a photoresist layer 2006. The photoresist layer
is photolithographically patterned and developed to form a mask,
and the image of the patterned photoresist mask 2006 is transferred
onto the underlying mask layers 2002, 2004 by one or more of
reactive ion etching and/or ion milling. The finished mask 2001 has
a shape that can be seen more clearly with reference to FIG. 21. As
seen in FIG. 21, the mask 2001 has a sensor stripe height defining
portion 2001(a) that is constructed in the sensor region 1902 and
is configured to define a strip height of the sensor. The mask 2001
also has an ELG defining portion 2001(b) that is formed in the ELG
area 1904 and that is configured to define the shape of an ELG.
After mask 2001 has been formed, an ion milling process is
performed to remove sensor material 1102 and hard bias material
1604 that is not protected by the mask 2001.
[0044] It should be pointed out at this point that, the mask
portions 2001(a) and 2001 (b) are patterned primarily over the
magnetic hard bias material 1604. It will be recalled that prior
art processes, wherein patterning of the sensor stripe height and
ELG were performed on sensor material, suffered from poor,
inaccurate definition of the ELG as a result of the differences in
reflectivity during photolithography. This is because the sensor
material is somewhat transparent, so the different reflectivities
of the under-lying shield and alumina fill layers resulted in
different reflectivities in the sensor and ELG regions during
photolithography. In the present invention, however, the
photolithography is performed on hard bias material. Although the
substrates beneath the hard bias material 1604 in the sensor and
ELG regions 1902, 1904 are still different (shield material and
alumina), the hard bias material 1604 is much more opaque than the
sensor material 1102. This means that the different reflectivities
of the substrate do not affect the photolithography. Therefore, the
problems associated with the prior art (with regard to different
reflectivities in during patterning of the ELG) are effectively
mitigated.
[0045] FIG. 22A shows a side cross sectional view or the structure
of FIG. 21 in the ELG region 1904 as seen from line 22A-22A, and,
similarly, FIG. 22B shows a side cross sectional view of the
structure of FIG. 21 in the sensor region 1902 as seen from line
22B-22B. The cross section of FIG. 22B shows the sensor material
1102 in the sensor region after the ion milling has been performed.
This ion milling is a stripe height defining ion milling. As can be
seen, the ion milling can be terminated before all of the sensor
material has been removed, leaving a desired tail 2202 of sensor
material behind the stripe height defining back edge 2204 of the
sensor material 1102. As discussed above, this tail 2202 of sensor
material allows all or a portion of the AFM layer 320 (FIG. 4)
structure 308 to extend beyond the stripe height defining back edge
2204 (FIG. 22B), which greatly enhances pinning strength.
[0046] On the other hand, it can be seen in FIG. 22A that even
though the ion milling of the sensor material 1102 left a tail as
shown in FIG. 22B, the hard bias material 1604 that makes up the
ELG has been removed all of the way to the substrate 802. This is
because the hard bias material 1602 is removed more rapidly by the
ion milling than are the materials making up the sensor layers
1102. The ELG formed by the layer 1602, therefore, has a back edge
2206 that extends all of the way to the substrate 802. This allows
the ELG 1602 to have a well defined back edge which can be used to
clearly identify the point at which lapping should be terminated to
accurately define the stripe height of the sensor, as will be
seen.
[0047] With continued reference to FIGS. 22A and 22B a
non-magnetic, dielectric fill layer 2208 is deposited full film.
This material 2208 is preferably alumina (Al.sub.2O.sub.3) to a
thickness that is at least as thick as the sensor material 1602. A
layer of material that is resistant to chemical mechanical
polishing (second CMP stop layer) 2210 is then deposited over the
fill layer 2208. The second CMP stop layer 2210 can be a carbon or
Diamond Like Carbon (DLC).
[0048] A chemical mechanical polishing process is then performed to
planarize the structure, leaving a structure as shown in FIGS. 23A
and 23B. A quick reactive ion etching is then performed to remove
the remaining CMP stop layers 2002, 2210, leaving a structure such
as that shown in FIG. 24A and 24B.
[0049] FIG. 25 shows a top down view of the structures of FIGS. 24A
and 24B. As shown in FIGS. 25 and 24A a pair of electrically
conductive leads 2502, 2504 are formed over the end portions of the
ELG 1602. These leads 2502, 2504 can be used to measure the
electrical resistance across the ELG 1602 during lapping to
determine lapping progress. The leads 2502 can be formed by a
liftoff process by forming a mask (not shown) having an opening
that is configured to define the leads 2502, 2504, then sputter
depositing an electrically conductive material and then lifting off
the mask. With reference to FIG. 24B an upper shield 2404 can be
formed over the sensor 1102, constructed of a magnetic,
electrically conductive material such as NiFe or CoFe and deposited
by electroplating.
[0050] With reference again to FIG. 25, once the head (including
the write head) has been completely formed on a wafer, the wafer is
sliced into rows of heads. Then, a lapping operation is performed
from a direction indicated by arrows 2506 until the desired air
bearing surface plane has been reached. The air bearing surface
plane is indicated in FIG. 25 at the dashed line denoted "ABS". the
electrical resistance across the lapping guide 1602 is measured
during lapping. As the lapping progresses, lapping guide material
will be removed accordingly, resulting in a corresponding increase
in electrical resistance across the lapping guide. When the desired
electrical resistance has been reached, indicating that the ABS
plane has been reached, lapping is terminated.
[0051] It can be seen then, that a novel method of manufacturing a
lapping guide from the material used to form the hard bias layers
for the sensor can eliminate the problems associated with lapping
guide tail formation and also with regard to differences in
reflectivity during photolithographic patterning of the lapping
guide and sensor. This advantageously provides a much higher degree
of accuracy in the lapping operation used to define the stripe
height of the sensor.
[0052] While various embodiments have been described above, it
should be understood that they have been presented by way of
example only and not limitation. Other embodiments falling within
the scope of the invention may also become apparent to those
skilled in the art. Thus, the breadth and scope of the invention
should not be limited by any of the above-described exemplary
embodiments, but should be defined only in accordance with the
following claims and their equivalents.
* * * * *