U.S. patent application number 11/095830 was filed with the patent office on 2006-10-05 for head design with low coefficient of thermal expansion insert layer.
This patent application is currently assigned to Hitachi Global Storage Technologies Netherlands, B.V. Invention is credited to Christian R. Bonhote, Malika D. Carter, David A. Dudek, Wen-Chien D. Hsiao, John W. Lam, Vladimir Nikitin.
Application Number | 20060221498 11/095830 |
Document ID | / |
Family ID | 37070082 |
Filed Date | 2006-10-05 |
United States Patent
Application |
20060221498 |
Kind Code |
A1 |
Bonhote; Christian R. ; et
al. |
October 5, 2006 |
Head design with low coefficient of thermal expansion insert
layer
Abstract
A magnetic read/write head is produced with an insert layer
between the substrate and the magnetic transducer. The insert layer
has a lower coefficient of thermal expansion than the substrate,
which reduces the temperature pole tip recession (T-PTR) of the
head because the insert layer is an intervening layer between the
substrate and magnetic transducer. The insert layer is produced by
plating, e.g., an Invar layer over the substrate prior to
fabricating the magnetic transducer. The Invar layer is annealed
and the structure planarized prior to depositing a non-magnetic gap
layer followed by the fabrication of the magnetic transducer.
Inventors: |
Bonhote; Christian R.; (San
Jose, CA) ; Carter; Malika D.; (San Jose, CA)
; Dudek; David A.; (San Jose, CA) ; Hsiao;
Wen-Chien D.; (San Jose, CA) ; Lam; John W.;
(San Jose, CA) ; Nikitin; Vladimir; (Campbell,
CA) |
Correspondence
Address: |
SILICON VALLEY PATENT GROUP LLP
2350 MISSION COLLEGE BOULEVARD
SUITE 360
SANTA CLARA
CA
95054
US
|
Assignee: |
Hitachi Global Storage Technologies
Netherlands, B.V
|
Family ID: |
37070082 |
Appl. No.: |
11/095830 |
Filed: |
March 30, 2005 |
Current U.S.
Class: |
360/125.31 ;
360/125.74; G9B/5.079; G9B/5.087; G9B/5.143 |
Current CPC
Class: |
G11B 5/40 20130101; Y10T
29/49048 20150115; G11B 5/3163 20130101; Y10T 29/49043 20150115;
G11B 5/3106 20130101; G11B 5/3133 20130101; G11B 5/3136 20130101;
Y10T 29/49044 20150115; Y10T 29/49046 20150115; Y10T 29/49032
20150115; Y10T 29/49041 20150115; Y10T 29/49052 20150115 |
Class at
Publication: |
360/126 |
International
Class: |
G11B 5/147 20060101
G11B005/147 |
Claims
1. A magnetic read/write head comprising: a substrate having a
first coefficient of thermal expansion; a magnetic transducer
coupled to the substrate, the magnetic transducer having a second
coefficient of thermal expansion that is greater than the first
coefficient of thermal expansion; a conductive layer coupled
between the substrate and the magnetic transducer, the conductive
layer having a third coefficient of thermal expansion that is less
than the first coefficient of thermal expansion; and a non-magnetic
layer coupled between the conductive layer and the magnetic
transducer.
2. The magnetic read/write head of claims 1, wherein the conductive
layer is a layer of plated Invar.
3. The magnetic read/write head of claims 2, wherein the plated
Invar comprises approximately 34 to 38 percent Nickel and 62 to 66
percent Iron.
4. The magnetic read/write head of claims 2, wherein the plated
Invar comprises approximately 0.1 to 5.0 percent of Cobalt, 35 to
36 percent of Nickel, and 62 to 64 percent of Iron.
5. The magnetic read/write head of claims 2, wherein the plated
Invar is annealed at a temperature greater than 450.degree. C.
6. The magnetic read/write head of claims 1, wherein the conductive
layer coupled between the substrate and the magnetic transducer is
between approximately 1.0 .mu.m to 5.0 .mu.m.
7. The magnetic read/write head of claims 1, wherein the conductive
layer has the approximate dimensions of a bottom shield of the
magnetic transducer.
8. The magnetic read/write head of claims 1, wherein the
non-magnetic layer coupled between the conductive layer and the
magnetic transducer comprises at least one of tantalum and
SiO.sub.2.
9. The magnetic read/write head of claims 8, wherein the
non-magnetic layer is between approximately 0.1 .mu.m and 1.0
.mu.m.
10. A method of forming a magnetic read/write head, the method
comprising: providing a substrate; plating a NiFe layer over the
substrate; annealing the NiFe layer; depositing a non-magnetic
layer over the NiFe layer; and producing a magnetic transducer over
the non-magnetic layer.
11. The method of claim 10, further comprising depositing an
undercoating layer over the substrate prior to plating the NiFe
layer.
12. The method of claim 11, further comprising: removing a plating
field of the NiFe layer; depositing a covering layer over the
remaining NiFe layer and over the underlying undercoating layer
prior to annealing the NiFe layer; and polishing the covering layer
to expose the underlying NiFe layer.
13. The method of claim 12, wherein the remaining NiFe layer has
the approximate dimensions of a bottom shield of the magnetic
transducer.
14. The method of claim 12, wherein the covering laying and the
undercoating layer comprise alumina.
15. The method of claim 10, wherein the NiFe layer is annealed
above approximately 450 degrees C.
16. The method of claim 15, wherein the NiFe layer is annealed at
approximately 490 degrees C. for approximately 2 hours.
17. The method of claim 10, wherein the NiFe layer is plated at a
ratio of approximately 34 to 38 percent Ni and 62 to 66 percent
Fe.
18. The method of claim 10, wherein the NiFe layer further includes
Co and is plated at a ratio of approximately 0.1 to 5.0 percent of
Co, 35 to 36 percent of Ni, and 62 to 64 percent of Fe.
19. The method of claim 10, wherein the NiFe layer is plated to a
thickness of approximately 1.0 .mu.m to 5.0 .mu.m.
20. The method of claim 10, wherein the non-magnetic layer
comprises at least one of tantalum and SiO.sub.2.
21. The method of claim 20, wherein the non-magnetic layer is
deposited to a thickness of approximately 0.1 .mu.m to 1.0
.mu.m.
22. The method of claim 10, wherein the annealed NiFe layer has a
coefficient of thermal expansion that is less than the coefficient
of thermal expansion of the substrate.
23. A method of forming a magnetic read/write head, the method
comprising: providing a substrate with a first coefficient of
thermal expansion; plating a conductive layer over the substrate;
annealing the conductive layer, wherein the annealed conductive
layer has a second coefficient of thermal expansion that is less
than the first coefficient of thermal expansion; depositing a
non-magnetic layer over the conductive layer; and fabricating a
magnetic transducer over the non-magnetic layer, wherein the
magnetic transducer has a third coefficient of thermal expansion
that is greater than the first coefficient of thermal expansion.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to magnetic read/write heads,
and in particular to magnetic read/write heads with reduced thermal
pole-tip protrusion.
BACKGROUND
[0002] Magnetic read/write heads, such as those used in hard disk
drives, include a magnetic transducer with a write element and a
read element disposed on a substrate. The write element is an
inductive transducer, which includes electrically conductive coil
windings that are encircled by a magnetic core. The magnetic core
includes a first and second pole tips with a non-magnetic gap
disposed between the tips. When electrical current flows through
the coil a magnetic field is induced across the non-magnetic gap at
the pole tips to write on the magnetic media, i.e., the hard disk,
which is near the pole tips.
[0003] The read element is typically formed between the write
element and the substrate and typically includes first and second
shield layers with a magnetoresistive (MR) sensor formed
therebetween. Magnetic flux from the surface of the magnetic media
causes the rotation of a magnetization vector in the MR sensor,
which causes a change in resistivity. Thus, the presence of
magnetic flux at the surface of the magnetic media may be detected
by measuring the change in resistivity of the MR sensor.
[0004] The read/write elements are located at the trailing end of
the substrate along the air bearing surface. In operation, the head
flies above the spinning magnetic disk so that the read/write
elements are positioned in close proximity to the magnetic
recording media. Ideally, the read/write elements are close enough
to the magnetic media to produce a large data density, however, the
distance should be great enough that contact between the read/write
elements and the magnetic media does not occur.
[0005] Because the read/write elements are fabricated from
materials different from that of the substrate, the read/write
elements and the substrate typically have differing coefficients of
thermal expansion (CTE). Generally, the read/write elements include
metallic layers causing the read/write elements to have a greater
CTE than the substrate. During operation, as the read/write head
flies above the spinning magnetic media, the read/write head is
subjected to increased temperatures. The increased temperatures and
the greater CTE of the read/write elements causes the read/write
elements to protrude closer to the magnetic media than the
substrate, which is known as thermal pole tip protrusion (T-PTR).
Thus, T-PTR requires an increase in the fly height of the
read/write head in order to avoid contact between the read/write
elements and the magnetic media during high operating
temperatures.
[0006] Accordingly, it is desirable to reduce the amount of T-PTR
in a read/write head so as to reduce variation in the distance
between the read/write elements and the magnetic media during
operation, which permits a decrease in the required fly height of
the head.
SUMMARY
[0007] A magnetic read/write head, in accordance with an embodiment
of the present invention, is produced with an insert layer that has
a lower CTE than the substrate and that is positioned between the
substrate and the magnetic transducer. With the magnetic transducer
deposited over the low CTE insert layer, the expansion of the
magnetic transducer is restricted during operation thereby
decreasing the T-PTR of the head. The insert layer is produced by
plating and annealing, e.g., an Invar NiFe layer over the substrate
prior to fabricating the magnetic transducer.
[0008] In one aspect of the present invention, a magnetic
read/write head includes a substrate and a magnetic transducer that
is coupled to the substrate. The magnetic transducer has a
coefficient of thermal expansion that is greater than the
coefficient of thermal expansion of the substrate. The head also
includes a conductive layer that is coupled between the substrate
and the magnetic transducer. The conductive layer has a coefficient
of thermal expansion that is less than the coefficient of thermal
expansion of the substrate. In addition, the head includes a
non-magnetic layer that is coupled between the conductive layer and
the magnetic transducer.
[0009] In another aspect of the present invention, a method of
forming a magnetic read/write head includes providing a substrate
and plating a NiFe layer over the substrate. The NiFe layer is
annealed and a non-magnetic layer is deposited over the NiFe layer.
A magnetic transducer is then formed over the non-magnetic
layer.
[0010] In yet another aspect of the present invention, a method of
forming a magnetic read/write head includes providing a substrate,
plating a conductive layer over the substrate, and annealing the
conductive layer, wherein the annealed conductive layer has a
coefficient of thermal expansion that is less than the coefficient
of thermal expansion of the substrate. The method further includes
depositing a non-magnetic layer over the conductive layer and
fabricating a magnetic transducer over the non-magnetic layer,
wherein the magnetic transducer has a coefficient of thermal
expansion that is greater than the coefficient of thermal expansion
of the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a cross-sectional view, perpendicular to the air
bearing surface, of a portion of a magnetic read/write head, in
accordance with an embodiment of the present invention.
[0012] FIGS. 2A and 2B illustrate the effect of T-PTR on a magnet
head, in accordance with an embodiment of the present invention,
where FIG. 2A illustrates the head prior to heating and FIG. 2B
illustrates the head after heating.
[0013] FIGS. 3A and 3B illustrate the effect of T-PTR on a
conventional head, where FIG. 3A illustrates the head prior to
heating and FIG. 3B illustrates the head after heating.
[0014] FIG. 4 illustrates a graph modeling the T-PTR for two
conventional heads and a head, in accordance with an embodiment of
the present invention.
[0015] FIG. 5 is a flow chart of the process of fabricating a
magnetic read/write head in accordance with an embodiment of the
present invention.
[0016] FIGS. 6A-6E schematically illustrates the fabrication
process for a magnetic read/write head in accordance with an
embodiment of the present invention.
DETAILED DESCRIPTION
[0017] FIG. 1 is a cross-sectional view, perpendicular to the air
bearing surface (ABS), of a portion of a magnetic read/write head
100 in accordance with an embodiment of the present invention. The
magnetic head 100 includes an insert layer 110 that has a lower
coefficient of thermal expansion (CTE) than that of the substrate,
which advantageously reduces temperature induced pole tip recession
during operation of the head.
[0018] As illustrated in FIG. 1, the head 100 includes a slider
substrate 102, which is manufactured from materials, such as AlTiC,
TiC, Si, SiC Al.sub.2O.sub.3 or other similar materials or
composites formed from combinations of these materials. An
undercoat layer 104, e.g., of alumina, is deposited over the
substrate 102. Over the undercoat layer 104 is deposited the insert
layer 110. The insert layer 110 is an alloy of nickel (Ni) and iron
(Fe), which is sometimes referred to Invar, which advantageously
has a low CTE. A non-magnetic spacer 112 is deposited over the
insert layer 110. The non-magnetic spacer 112 is used to break the
magnetic coupling of the insert layer 110 from the magnetic
transducer 120.
[0019] A magnetic transducer 120 is fabricated over the
non-magnetic spacer 112 in any desired fashion. Magnetic
transducers and their fabrication are well known, and accordingly,
magnetic transducer 120 is shown merely for illustrative purposes.
The present invention is not limited to any particular type of
magnetic transducer. Thus, any desired magnetic transducer may be
fabricated over the non-magnetic spacer layer 112.
[0020] As illustrated in FIG. 1, the magnetic transducer 120 may
include, e.g., a read portion 130 with a first shield layer 132, an
insulator layer 134 in which is disposed a sensor element (not
shown) and a second shield layer 136.
[0021] The write portion 140 of the magnetic transducer 120 may
include a first pole piece 142 and a second pole piece 144 that are
separated at the ABS by a write gap layer 150 and a third pole
piece 146. The third pole piece 146 connects the first pole piece
142 and the second pole piece 144 at the back gap (BG). The third
pole piece 146 is formed on either side at the write gap layer 150
at the ABS. The write portion 140 also includes two coil layers 152
and 154, which surround the write gap layer 150 and which are
covered with resist 153 and 155. It should be understood that the
write coil may be in a single layer if desired.
[0022] The magnetic read/write head 100 has a reduced amount of
T-PTR, relative to conventional heads, because the insert layer 110
has a lower CTE than the substrate 102 and the insert layer 110 is
disposed between the substrate 102 and the magnetic transducer 120.
During operation, the insert layer 110 will expand less than the
substrate 102. Because the magnetic transducer 120 is formed on the
insert layer 110, as opposed to the substrate 102, the insert layer
110 will restrict the expansion of the magnetic transducer 120.
[0023] FIGS. 2A and 2B illustrate the effect of T-PTR on a magnet
head 100, where an insert layer 110 is disposed between the
substrate 102 and the magnetic transducer 120. FIG. 2A illustrates
the head 100 prior to heating and FIG. 2B illustrates the head 100
after heating, with the expansion of the substrate 102 and the
magnetic transducer 120 greatly exaggerated. As can be seen in FIG.
2B, the insert layer 110, which expands less than the substrate
102, resists the expansion of the magnetic transducer 120. The
insert layer 110 limits the expansion of the magnetic transducer
120 to an amount that is closer to the expansion of the substrate
102. Accordingly, the magnetic transducer 120 has little
protrusion, illustrated as T-PTR.sub.100, beyond the substrate 102,
resulting in a reduced amount of T-PTR relative to conventional
heads.
[0024] FIGS. 3A and 3B illustrate the effect of T-PTR on a
conventional head 200, where a magnetic transducer 204 is coupled
to the substrate 202 without an intervening Invar insert layer.
FIG. 3A illustrates the head 200 prior to heating and FIG. 3B
illustrates the head 200 after heating with the expansion of the
substrate 202 and the magnetic transducer 204 greatly exaggerated.
As can be seen in FIG. 3B, in the conventional head 200, the
magnetic transducer 204 expands more than the substrate 202 when
heated, but the expansion of the magnetic transducer 204 is limited
by the substrate 202. Accordingly, the magnetic transducer 204
protrudes closer to the underlying magnetic media (not shown) than
the substrate 202, resulting in a large amount of T-PTR.
[0025] FIG. 4 illustrates a graph illustrating the modeling results
of the T-PTR (in nm at 30.degree. C.) as a function of distance
from the undercoat, i.e., layer 104 in FIG. 1, for two conventional
heads and a head with an Invar insert, in accordance with the
present invention. As can be seen, the head with the Invar insert
has a substantial reduction in the T-PTR compared to conventional
heads. In fact, the maximum T-PTR for a head in accordance with the
present invention is 0.55 nm compared to 1.1 nm for the head
labeled Conv2.
[0026] FIG. 5 is a flow chart of the process of fabricating a
magnetic read/write head in accordance with an embodiment of the
present invention. FIGS. 6A-6E schematically illustrates the
fabrication process. It should be understood that FIG. 5 and FIGS.
6A-6E, describe the fabrication of a single head for the sake of
simplicity and that the fabrication is performed at the wafer
level, where multiple heads are fabricated simultaneously and then
separated.
[0027] As described in FIG. 5, first a substrate with an
undercoating is provided (block 302). The substrate may be, e.g., a
manufactured from AlTiC, TiC, Si, SiC Al.sub.2O.sub.3 or other
similar materials or composites formed from combinations of these
materials. By way of example, a AlTiC substrate with a CTE of
approximately 6.times.10.sup.-6/.degree. C. may be used. The
undercoating may be, e.g., 0.7 .mu.m to 1.0 .mu.m of alumina. A
seed layer is then deposited over the undercoating (block 304). The
seed layer may be, e.g., 32/68 or 45/55 of nickel and iron, and may
be, e.g., sputter deposited to a thickness of, e.g., 300-2000
.ANG.. Other seed layers, including non-magnetic but conductive
seed layers, may be used if desired, such as V or NiCr.
[0028] The Invar insert layer is then frame plated over the seed
layer (block 306). The Invar insert layer is produced with 34 to 38
percent Ni and 62 to 66 percent Fe to a thickness of between
approximately 1.0 .mu.m to 5.0 .mu.m. In one embodiment, Invar
insert layer is Ni.sub.36Fe.sub.64 and is approximately 4.0 .mu.m.
In another embodiment, the insert may be produced with plated
CoNiFe, where Co is 0.1 to 5.0 percent, Ni is 35 to 36 percent, and
Fe is 62 to 64 percent. FIG. 6A shows an illustrative cross section
of the frame plated Invar insert layer 410 deposited over the seed
layer 406, undercoating 404 and the substrate 402. The plating mask
for the Invar insert layer may have approximately the same size
and/or shape, or larger, as the first shield in the magnetic
transducer. If desired, alignment marks may be produced with the
frame plating at this step to be used in later fabrication of the
magnetic transducer.
[0029] The plating field and the seed layer underlying the plating
field are then removed by, e.g., wet etching, (block 308),
resulting in the structure shown in FIG. 6B. After the plating
field and seed layer removal, the Invar insert layer and gaps are
covered with an overcoat layer (block 310). The overcoat layer may
be the same material as used for the undercoating, i.e. alumina.
FIG. 6C illustrates the resulting structure with the overcoat layer
412 deposited over the Invar insert layer 410. The overcoat layer
412 should be deposited to a thickness that is greater than the
Invar insert layer 410, e.g., 4.0 .mu.m to 5.0 .mu.m, so that the
structure may be planarized later.
[0030] With the Invar insert layer 410 covered with the overcoat
layer 412, the structure is annealed at a temperature greater than
450.degree. C., e.g., between approximately 450.degree. C. and
800.degree. C., e.g., at 490.degree. C., for between approximately
1 and 10 hours, e.g., for 2 hours, with a slow temperature ramp
(block 312). The annealing of the Invar insert layer 410
advantageously produces a phase transition in the material that
reduces the CTE to, e.g., 4.5.times.10.sup.-6/.degree. C.
[0031] The structure is then planarized, e.g., by chemical
mechanical polishing, to the desired final thickness of the Invar
insert layer, e.g., 4 .mu.m (block 314). FIG. 6D illustrates the
structure after planarizing.
[0032] A non-magnetic spacer layer is deposited over the Invar
insert layer (block 316). The non-magnetic spacer layer may be,
e.g., a layer of Ta, that is sputter deposited to a thickness of
approximately 0.1 .mu.m to 1.0 .mu.m, e.g., 0.25 .mu.m. If desired,
other non-magnetic low expansion materials, such as AlO.sub.2, may
be used, however, the use of Ta is desirable as it provides good
heat dissipation. FIG. 6E illustrates the structure with the
non-magnetic spacer layer 414 over the Invar insert layer 410 and
the remaining overcoating layer 412. The deposition of the
non-magnetic spacer layer may be followed with any desired
conventional magnetic transducer fabrication process (block
318).
[0033] Although the present invention is illustrated in connection
with specific embodiments for instructional purposes, the present
invention is not limited thereto. Various adaptations and
modifications may be made without departing from the scope of the
invention. For example, additional layers, such as adhesion layers,
may be used with the present invention. Moreover, the present
invention is not limited to any particular magnetic transducer.
Therefore, the spirit and scope of the appended claims should not
be limited to the foregoing description.
* * * * *