U.S. patent application number 09/814637 was filed with the patent office on 2001-08-30 for read heads in planar monolithic integrated circuit chips.
This patent application is currently assigned to NVE Corporation. Invention is credited to Daughton, James M., Pohm, Arthur V..
Application Number | 20010017543 09/814637 |
Document ID | / |
Family ID | 26886854 |
Filed Date | 2001-08-30 |
United States Patent
Application |
20010017543 |
Kind Code |
A1 |
Daughton, James M. ; et
al. |
August 30, 2001 |
Read heads in planar monolithic integrated circuit chips
Abstract
A plurality of magnetic field sensing structures in a monolithic
integrated circuit chip structure to provide output signals at
outputs thereof of magnetic field changes provided therein from
corresponding sources having poled pair structures with a gap space
between them with adjacent ones of the magnetic field sensing
structures that are interconnected with a circuit formed in the
monolithic integrated circuit chip such as an amplifier. The paired
pole structures may intersect a surface of the chip perpendicular
to the major surfaces thereof or in one of, or a surface parallel
to, the major surfaces thereof. A magnetic field generating
structure may also be included in the chip.
Inventors: |
Daughton, James M.; (Eden
Prairie, MN) ; Pohm, Arthur V.; (Ames, IA) |
Correspondence
Address: |
KINNEY & LANGE, P.A.
THE KINNEY & LANGE BUILDING
312 SOUTH THIRD STREET
MINNEAPOLIS
MN
55415-1002
US
|
Assignee: |
NVE Corporation
11409 Valley View Road
Eden Prairie
MN
55344
|
Family ID: |
26886854 |
Appl. No.: |
09/814637 |
Filed: |
March 22, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09814637 |
Mar 22, 2001 |
|
|
|
08907561 |
Aug 8, 1997 |
|
|
|
60191209 |
Mar 22, 2000 |
|
|
|
Current U.S.
Class: |
324/252 ;
G9B/5.114; G9B/5.116; G9B/5.131; G9B/5.135; G9B/5.156;
G9B/5.227 |
Current CPC
Class: |
B82Y 10/00 20130101;
G01R 33/093 20130101; G11B 5/3948 20130101; G11B 5/3903 20130101;
G11B 5/3967 20130101; G11B 5/3954 20130101; B82Y 25/00 20130101;
G11B 5/3909 20130101; G11B 5/59683 20130101; G11B 2005/3996
20130101; G11B 5/488 20130101 |
Class at
Publication: |
324/252 |
International
Class: |
G01R 033/02 |
Claims
1. A plurality of magnetic field sensors in a multiple sensor
structure having a substrate, said magnetic field sensors providing
at corresponding outputs thereof representations of magnetic field
changes provided therein from a corresponding source of such
magnetic field changes, said sensor structure comprising: a
plurality of paired pole structures supported on said substrate
with each of those pole structures in a said paired pole structure
being spaced apart from one another to form a corresponding gap
space therebetween and with each of said pole structures comprising
a permeable material and having an end thereof substantially in a
common surface; and a plurality of field sensing structures each
supported on said substrate adjacent a corresponding paired pole
structure with at least a portion thereof positioned away from said
common surface, each of said plurality field sensing structures
being formed of a plurality of magnetoresistive, anisotropic,
ferromagnetic thin-film layers at least two of which are separated
from one another by a nonmagnetic layer positioned
therebetween.
2. The apparatus of claim 1 wherein said substrate includes a
monolithic integrated circuit with circuit interconnections being
provided coupling electrical circuits in said monolithic integrated
circuit to each of said plurality of field sensing structures.
3. The apparatus of claim 1 wherein said common surface is a
surface of said sensor structure substantially perpendicular to a
major surface of said substrate on which said plurality of paired
pole structures and said plurality of field sensing structures are
supported.
4. The apparatus of claim 1 wherein said common surface is a
surface of said sensor structure substantially parallel to a major
surface of said substrate on which said plurality of paired pole
structures and said plurality of field sensing structures are
supported.
5. The apparatus of claim 1 wherein each of said plurality of field
sensing structures is supported in said gap space of said
corresponding paired pole structure and each has said nonmagnetic
layer thereof formed of an electrically conductive material and
positioned between said two ferromagnetic thin-film layers thereof
which each extend to said common surface.
6. The apparatus of claim 1 wherein each of said plurality of field
sensing structures has one of said two ferromagnetic thin-film
layers thereof extend to said common surface and each has said
nonmagnetic layer thereof formed of an electrically insulative
material and positioned between said two ferromagnetic thin-film
layers thereof.
7. The apparatus of claim 1 wherein said pair of pole structures in
a said paired pole structure are relatively closely spaced apart
from one another adjacent said common surface but are relatively
distantly spaced apart from one another elsewhere along said
corresponding field sensing structure.
8. The apparatus of claim 1 further comprising a storing paired
pole structure supported on said substrate with each of those pole
structures in said storing paired pole structure being spaced apart
from one another to form a corresponding storing gap space
therebetween and with each of said pole structures comprising a
permeable material and having a portion thereof substantially in
said common surface, said storing paired pole structure having a
coiled electrical conductor provided in said storing gap space away
from said common surface supported on a surface parallel to said
common surface.
9. The apparatus of claim 2 wherein said electrical circuits
contain an electronic signal amplifier.
10. The apparatus of claim 3 wherein at least one of said plurality
of field sensing structures has one of said two ferromagnetic
thin-film layers thereof extend to said common surface following a
straight line path.
11. The apparatus of claim 4 at least one of said plurality of
field sensing structures has one of said two ferromagnetic
thin-film layers thereof extend to said common surface following a
path other than a straight line path.
12. The apparatus of claim 4 at least one of said plurality of
field sensing structures has said two ferromagnetic thin-film
layers thereof extend to said common surface following a path other
than a straight line path.
13. The apparatus of claim 4 wherein at least one of said plurality
of paired pole structures can have a selected line in said common
surface intersect both of its pole structures so that others of
said plurality of paired pole structures each have both of its pole
structures intersect such a line.
14. The apparatus of claim 4 wherein at least one of said plurality
of paired pole structures can have a selected line in said common
surface intersect both of its pole structures so that others of
said plurality of paired pole structures each have both of its pole
structures laterally offset from such a line.
15. The apparatus of claim 4 wherein at least one of said plurality
of paired pole structures can have a selected first line in said
common surface intersect both of its pole structures to form a
first intersection so that others of said plurality of paired pole
structures each have both of its pole structures laterally offset
from such a first line, and each of said plurality of paired pole
structures can also have a selected correspondence line in said
common surface parallel to said selected first line intersect both
of its pole structures at least one of which forms an intersection
at an angle differing from that in said first intersection.
16. The apparatus of claim 8 wherein said pair of pole structures
in a said storing paired pole structure are relatively closely
spaced apart from one another adjacent said common surface but are
relatively distantly spaced apart from one another elsewhere
adjacent said coiled electrical conductor.
17. A plurality of magnetic field sensors in a multiple sensor
structure having a substrate, said magnetic field sensors providing
at corresponding outputs thereof representations of magnetic field
changes provided therein from a corresponding source of such
magnetic field changes, said sensor structure comprising: at least
one paired pole structure supported on said substrate with each of
those pole structures in said paired pole structure being spaced
apart from one another to form a corresponding gap space
therebetween and with each of said pole structures comprising a
permeable material and having an end thereof substantially in a
common surface; and a plurality of field sensing structures each
supported on said substrate adjacent a corresponding paired pole
structure with at least a portion thereof positioned away from said
common surface, each of said plurality field sensing structures
being formed of a plurality of magnetoresistive, anisotropic,
ferromagnetic thin-film layers at least two of which are separated
from one another by a nonmagnetic layer positioned
therebetween.
18. The apparatus of claim 17 wherein said substrate includes a
monolithic integrated circuit with circuit interconnections being
provided coupling electrical circuits in said monolithic integrated
circuit to each of said plurality of field sensing structures.
19. The apparatus of claim 17 wherein said common surface is a
surface of said sensor structure substantially perpendicular to a
major surface of said substrate on which said plurality of paired
pole structures and said plurality of field sensing structures are
supported.
20. The apparatus of claim 17 wherein said common surface is a
surface of said sensor structure substantially parallel to a major
surface of said substrate on which said plurality of paired pole
structures and said plurality of field sensing structures are
supported.
21. The apparatus of claim 17 wherein said paired pole structure is
one of a plurality of such paired pole structures and wherein each
of said plurality of field sensing structures is supported in said
gap space of said corresponding paired pole structure and each has
said nonmagnetic layer thereof formed of an electrically conductive
material and positioned between said two ferromagnetic thin-film
layers thereof which each extend to said common surface.
22. The apparatus of claim 17 wherein said paired pole structure is
one of a plurality of such paired pole structures and wherein each
of said plurality of field sensing structures has one of said two
ferromagnetic thin-film layers thereof extend to said common
surface and each has said nonmagnetic layer thereof formed of an
electrically insulative material and positioned between said two
ferromagnetic thin-film layers thereof.
23. The apparatus of claim 17 wherein said pair of pole structures
in said paired pole structure are relatively closely spaced apart
from one another adjacent said common surface but are relatively
distantly spaced apart from one another elsewhere along said
corresponding field sensing structure.
24. The apparatus of claim 17 further comprising a storing paired
pole structure supported on said substrate with each of those pole
structures in said storing paired pole structure being spaced apart
from one another to form a corresponding storing gap space
therebetween and with each of said pole structures comprising a
permeable material and having a portion thereof substantially in
said common surface, said storing paired pole structure having a
coiled electrical conductor provided in said storing gap space away
from said common surface supported on a surface parallel to said
common surface.
25. The apparatus of claim 18 wherein said electrical circuits
contain an electronic signal amplifier.
26. The apparatus of claim 19 wherein at least one of said
plurality of field sensing structures has one of said two
ferromagnetic thin-film layers thereof extend to said common
surface following a straight line path.
27. The apparatus of claim 20 at least one of said plurality of
field sensing structures has one of said two ferromagnetic
thin-film layers thereof extend to said common surface following a
path other than a straight line path.
28. The apparatus of claim 20 at least one of said plurality of
field sensing structures has said two ferromagnetic thin-film
layers thereof extend to said common surface following a path other
than a straight line path.
29. The apparatus of claim 20 wherein at least one of said
plurality of paired pole structures can have a selected line in
said common surface intersect both of its pole structures so that
others of said plurality of paired pole structures each have both
of its pole structures intersect such a line.
30. The apparatus of claim 20 wherein at least one of said
plurality of paired pole structures can have a selected line in
said common surface intersect both of its pole structures so that
others of said plurality of paired pole structures each have both
of its pole structures laterally offset from such a line.
31. The apparatus of claim 20 wherein at least one of said
plurality of paired pole structures can have a selected first line
in said common surface intersect both of its pole structures to
form a first intersection so that others of said plurality of
paired pole structures each have both of its pole structures
laterally offset from such a first line, and each of said plurality
of paired pole structures can also have a selected correspondence
line in said common surface parallel to said selected first line
intersect both of its pole structures at least one of which forms
an intersection at an angle differing from that in said first
intersection.
32. The apparatus of claim 24 wherein said pair of pole structures
in a said storing paired pole structure are relatively closely
spaced apart from one another adjacent said common surface but are
relatively distantly spaced apart from one another elsewhere
adjacent said coiled electrical conductor.
33. A method for fabricating a magnetic field sensor in a sensor
structure on a substrate, said method comprising: providing an
initial permeable material layer on a surface of said substrate
having an opening therein with an angled side formed at an angle
with respect to said substrate surface; providing an initial
nonmagnetic material layer supported by said initial permeable
material layer including supported by said angled side thereof;
providing a device permeable material layer supported by at least
one of said initial nonmagnetic material layer and an electrical
interconnection extending therethrough, said device permeable
material layer at least in part to be a portion of a magnetic
sensing structure; providing a device nonmagnetic material layer on
said device permeable material layer which is at least in part to
be a portion of a magnetic sensing structure; providing a
completion permeable material layer on said nonmagnetic material
layer which is at least in part to be a portion of a magnetic
sensing structure, at least one of said device permeable material
layer and said completion permeable material layer also being
provided across from said angled side; and removing portions of at
least said initial nonmagnetic material layer and at least one of
said device permeable material layer and said completion permeable
material layer to form a common surface intersected by such layers
which common surface intersects at least a portion of said angled
side.
34. The method of claim 33 further providing a subsequent
nonmagnetic material layer supported by at least a portion of said
completion permeable material layer and thereafter providing an
electrically conductive layer on said subsequent nonmagnetic
material layer and also across from a portion of said completion
permeable material layer.
35. The method of claim 34 wherein said electrically conductive
layer is also provided at a location across from a portion of at
least one of said device permeable material layer and said
completion permeable material layer without also being across from
said subsequent nonmagnetic material layer but being across from
said angled side.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of Application
Ser. No. 08/907,561, filed Aug. 8, 1997, entitled "Magnetic Field
Sensor", and claims priority from Provisional Application No.
60/191,209, filed Mar. 22, 2001, entitled "Read Heads in Planar
Monolithic Integrated Circuit Chips".
BACKGROUND OF THE INVENTION
[0002] Digital data magnetic recording systems store digital data
by recording same in a moving magnetic media layer using a storage,
or "write", electrical current-to-magnetic field transducer, or
"head", positioned immediately adjacent thereto. The data is stored
or written to the magnetic media by switching the direction of flow
in an otherwise substantially constant magnitude write current that
is established in coil windings in the write transducer in
accordance with the data. Each write current direction transition
results in a reversal of the magnetization direction, in that
portion of the magnetic media just then passing by the transducer
during this directional switching of the current flow, with respect
to the magnetization direction in that media induced by the
previous in the opposite direction.
[0003] Recovery of such recorded digital data is accomplished
through positioning a retrieval, or "read" magnetic
field-to-voltage transducer, or "head", to have the magnetic media,
containing previously stored data, pass thereby. Such passing by of
the media adjacent to the transducer permits the flux accompanying
the magnetization reversal regions in that media either to induce a
corresponding voltage pulse in forming an analog output read signal
for that retrieval transducer or, alternatively, change a
transducer circuit parameter based on magnetoresistive sensing of
magnetic conditions therein to thereby provide such an output
signal voltage pulse.
[0004] Such transducers or sensors can often be advantageously
fabricated using ferromagnetic thin-film materials. Ferromagnetic
thin-film sensors can be made very small when so constructed. Such
sensors are often provided in the form of an intermediate
separating material having two major surfaces on each of which an
anisotropic ferromagnetic thin-film is provided. In such "sandwich"
structures, reducing the thickness of the ferromagnetic thin-films
in the intermediate layer has been shown to lead to a "giant
magnetoresistive effect" being present for an electrically
conductive material intermediate layer or a "spin dependent
tunneling effect" being present for an electrically insulative
material intermediate layer. This effect can be enhanced by having
additional alternating ones of such films and layers, i.e.
superlattices. This effect can yield a magnetoresistive response
which can be in the range of up to an order of magnitude greater
than that due to the well-known anisotropic magnetoresistive
response.
[0005] In the ordinary anisotropic magnetoresistive response in
ferromagnetic thin-films, varying differences between the direction
of the magnetization vector in such a thin-film and the direction
of a sensing current passed through that film in turn lead to
varying differences in the effective electrical resistance of the
film in the direction of the current. The maximum electrical
resistance occurs when the magnetization vector in the film and the
current direction are parallel to one another, while the minimum
resistance occurs when they are perpendicular to one another. The
total electrical resistance of such a magnetoresistive
ferromagnetic thin-film exhibiting this response can be shown to be
given by a constant value, representing the minimum resistance
present, plus an additional value depending on the angle between
the current direction in the film and the magnetization vector
therein. This additional resistance follows a square of the cosine
of that angle.
[0006] As a result, external magnetic fields supplied for operating
a film sensor of this sort can be used to vary the angle of the
magnetization vector in such a film portion with respect to the
easy axis of that film portion. This axis exists in the film
because of an anisotropy present therein typically resulting from
depositing the film in the presence of an externally supplied
magnetic field during deposition of the film that is oriented in
the plane of the film along the direction desired for the easy axis
in the resulting film. During subsequent operation of a sensing
device using this resulting film, such externally supplied magnetic
fields for operating the film sensor can vary the magnetization
vector angle to such an extent as to cause switching of that film's
magnetization vector between two stable states which occur as
magnetizations oriented in opposite directions along the
established easy axis. The state of the magnetization vector in
such a film portion can be measured, or sensed, by the change in
resistance encountered by a current directed through this film
portion.
[0007] In contrast to this arrangement, resistance in the plane of
either of the ferromagnetic thin-films in the "sandwich" structure
is isotropic with respect to the giant magnetoresistive effect
rather than depending on the direction of a sensing current
therethrough as for the anisotropic magnetoresistive effect. The
giant magnetoresistive effect has a magnetization dependent
component to resistance that varies as the cosine of the angle
between the magnetizations in the two ferromagnetic thin-films on
either side of the intermediate layer. In the giant
magnetoresistive effect, the electrical resistance through the
"sandwich" or superlattice is lower if the magnetizations in the
two separated ferromagnetic thin-films are parallel than it is if
these magnetizations are antiparallel, i.e. oriented in opposing
directions. Further, the anisotropic magnetoresistive effect in
very thin films is considerably reduced from the bulk values
therefor in thicker films due to surface scattering, whereas very
thin films are a fundamental requirement to obtain a significant
giant magnetoresistive effect. The total electrical resistance in
such a magnetoresistive ferromagnetic thin-film "sandwich"
structure can be shown again to be given by a constant value,
representing the minimum resistance present, plus an additional
value depending on the angle between the magnetization vectors and
the two films as indicated above.
[0008] Another magnetic field sensor suited for fabrication with
dimensions of a few microns or less can be fabricated that provides
a suitable response to the presence of external magnetic fields and
low power dissipation by substituting an electrical insulator for a
conductor in the nonmagnetic layer. This sensor can be fabricated
using ferromagnetic thin-film materials of similar or different
kinds in each of the outer magnetic films provided in a "sandwich"
structure on either side of an intermediate nonmagnetic layer which
ferromagnetic films maybe composite films, but this insulating
intermediate nonmagnetic layer conducts electrical current
therethrough based primarily on a quantum electrodynamic effect
"tunneling" current.
[0009] This "tunneling" current has a magnitude dependence on the
angle between the magnetization vectors in each of the
ferromagnetic layers on either side of the intermediate layer due
to the transmission barrier provided by this intermediate layer
depending on the degree of matching of the spin polarizations of
the electrons tunneling therethrough with the spin polarizations of
the conduction electrons in the ferromagnetic layers, the latter
being set by the layer magnetization directions to provide a
"magnetic valve effect". Such an effect results in an effective
resistance, or conductance, characterizing this intermediate layer
with respect to the "tunneling" current therethrough.
[0010] In addition, shape anisotropy is often used in such a sensor
to provide different coercivities in the two ferromagnetic layers,
and by forming one of the ferromagnetic layers to be thicker than
the other. Such devices may be provided on a surface of a
monolithic integrated circuit to thereby allow providing convenient
electrical connections between each such sensor device and the
operating circuitry therefor.
[0011] A "sandwich" structure for such a sensor, based on having an
intermediate thin layer of a nonmagnetic, dielectric separating
material with two major surfaces on each of which a anisotropic
ferromagnetic thin-film is positioned, exhibits the "magnetic valve
effect" if the materials for the ferromagnetic thin-films and the
intermediate layers are properly selected and have sufficiently
small thicknesses. The resulting "magnetic valve effect" can yield
a response which can be several times in magnitude greater than
that due to the "giant magnetoresistive effect" in a similar sized
sensor structure.
[0012] One common magnetic field sensing situation is the sensing
of magnetization changes along a data recording track selected from
many such tracks in the magnetic media of a magnetic data storage
system. As these tracks are made narrower and narrower to permit
increases in the data density in the magnetic media, inductive
sensing of the magnetization changes along any of those tracks
becomes less feasible. The smaller magnetization volumes lead to
smaller outputs from an inductive sensor, and there is a limit to
the number of turns in the coil used in such a sensor which can be
provided to increase the output signal. Even in thin-film versions
thereof, such inductive sensing structures remain relatively thick
which becomes a problem as the tracks are made more narrow. Thus,
sensing of the magnetization changes along the track using
thin-film magnetoresistive sensors has become attractive.
[0013] Such magnetoresistive sensors for detecting magnetization
changes along a track in the magnetic media are typically formed
with the magnetoresistive sensor film in a rectangular shape, and
sensors based on such films in initial designs therefor had such a
sensing film positioned between a pair of highly permeable magnetic
material shielding poles with a long side of the film's rectangular
shape located adjacent the magnetic media to result in what is
oftentimes termed a horizontal sensor. More recently, such
magnetoresistive sensors have had an alternative construction with
such sensing films positioned between the poles with the short side
of the rectangle adjacent the magnetic media to form what is often
termed a vertical sensor or an "end-on" sensor. These kinds of
sensors were both initially based on use of the anisotropic
magnetoresistive effect in the sensing films. This effect gives a
maximum change in magnetoresistance due to the sensed magnetic
fields on the order of 2.5% at room temperature.
[0014] As data tracks in the magnetic media grow ever thinner
coupled with use of higher densities of magnetization direction
changes therealong, the need for a more efficient converter of such
magnetization changes in the magnetic medium into a sufficiently
large current or voltage output signal becomes greater. Hence,
horizontal and vertical magnetoresistive sensors based on the
"giant magnetoresistive effect" and the "spin dependent tunneling
effect" were introduced because of the greater changes in
resistance possible from corresponding changes in externally
applied magnetic fields. A vertical or end-on magnetoresistive
sensor based on the "giant magnetoresistive effect" or on the "spin
dependent tunneling effect" is typically formed with a nonmagnetic
intermediate conductive metal layer in the first instance, or with
a nonmagnetic intermediate insulative oxide layer in the second
instance, having ferromagnetic layers on opposite sides of the
major surfaces thereof with all layers in corresponding rectangular
shapes. As before, such a vertical sensor is mounted typically
between a pair of ferromagnetic material shielding poles in a
narrow gap provided therebetween so that a short side edge of the
rectangular film sensor is positioned adjacent the magnetic media
approximately in a plane with the sides of the poles also being
positioned adjacent the magnetic media with the resultant surface
in this plane forming the air bearing surface. Thus, the long sides
of the sensor extend inward into the gap between the poles and away
from the magnetic media.
[0015] Currently, read head transducers are typically provided as
hybrid assemblies with the magnetic sensor and the sensor operating
circuitry provided on one substrate mounted on the slider arm and
the input signal amplifier provided as a separate integrated
circuit chip mounted nearby. However, the parasitic capacitance in
such an arrangement shunts away more and more of the sensor signal
as the data recovery rate is increased leading to higher
frequencies being present in the sensor signal. This situation can
be improved by building the sensor and its operating circuitry on
the input amplifier integrated circuit mounted on the slider arm so
that the distance between the sensor output and the amplifier input
is smaller thereby lessening the parasitic capacitance associated
with that interconnection. One such arrangement is described in an
earlier filed co-pending application by J. M. Daughton and Arthur
V. Pohm entitled "Magnetic Field Sensor With A Plurality Of
Magnetoresistive Thin-film Layers Having An End At A Common
Surface" having Ser. No. 08/907,561 which is assigned to the same
or successor assignee as the present application and is hereby
incorporated herein by reference.
[0016] Magnetoresistive "read" sensing structures are made very
small to be in accord with the dimensions of the data tracks in the
magnetic media from which they are to sense magnetization
transitions, and therefore are usually made using monolithic
integrated circuit fabrication techniques anyway along with other
related thin-film fabrication techniques. Such limited sensing
structure sizes and such limited track widths also limit the
magnitude of the sensing structure output signal. However, because
magnetoresistive sensing structures are to be used with
increasingly narrow data tracks in the magnetic media passing by
them, an increase in the number of such structures provided side by
side may not feasible even though such a plurality of
magnetoresistive sensing structures would be most conveniently
provided in this manner because of structure sizes. This follows
because in that circumstance the steps performed in using
monolithic integrated circuit fabrication techniques to provide the
plurality of such sensing structures would be just those used to
provide one such structure as they are all fabricated
simultaneously. Thus, there is desired a sensor configuration which
can yield a suitable output signal for a given externally applied
input signal without resulting in widening the vertical sensor or
sensor portion which would limit the narrowness permitted for
tracks in the magnetic media.
BRIEF SUMMARY OF THE INVENTION
[0017] The present invention provides plural magnetic field sensing
structures in a monolithic integrated circuit chip structure for
providing at outputs thereof representations of magnetic field
changes provided therein by corresponding sources of such magnetic
field changes having poled pair structures with a gap space between
them adjacent to which are ones of the plurality of magnetic field
sensing structures. These sensing structures are formed of a
plurality of magnetoresistive, anisotropic, ferromagnetic thin-film
layers at least two of which are separated from one another by a
nonmagnetic electrically conductive or insulative layer positioned
between them, and at least one of them is interconnected with a
circuit formed in the monolithic integrated circuit chip such as an
amplifier. The paired pole structures may intersect a surface of
the chip perpendicular to the major surfaces thereof or one of, or
a surface parallel to, the major surfaces thereof. A magnetic field
generating structure may also be included in the chip.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIGS. 1 through 5 show portions of the results of
fabrication steps for forming a device embodying the present
invention,
[0019] FIGS. 6 through 9 show portions of the results of
fabrication steps for forming a device embodying the present
invention,
[0020] FIGS. 10 through 14 show portions of the results of
fabrication steps for forming a device embodying the present
invention,
[0021] FIGS. 15 through 17 show portions of the results of
fabrication steps for forming a device embodying the present
invention,
[0022] FIGS. 18 through 20 show portions of devices embodying the
present invention in various configurations, and
[0023] FIGS. 21 through 23 show portions of the results of
fabrication steps for forming a device embodying the present
invention.
DETAILED DESCRIPTION
[0024] Multiple end-on magnetoresistive sensing structures each
adjacent a paired pole structure can be provided in a monolithic
integrated circuit chip that intersect in part a common surface of
that chip as the "read head" air bearing surface to detect
magnetizations of magnetic media portions positioned in parallel
tracks each passing a corresponding sensing structure if those
sensing structures are formed in suitable configurations using a
fabrication process yielding structures on the chip of sufficiently
small sizes. Such a sensing structure is shown in an initial form
during chip fabrication in FIG. 1 following the earlier fabrication
of the semiconductor substrate portion having electronic circuits
provided therein such as signal amplifiers for use with such
structures. Shown in FIG. 1 is a portion of a ceramic slider arm,
9, formed of aluminum, titanium and carbon, with an already
fabricated semiconductor based monolithic integrated circuit chip
portion, 10, mounted thereon (for position clarification purposes
as the chip maybe completely fabricated first and thereafter
mounted on arm 9). An electrical insulating layer, 11, typically of
silicon nitride 2500 .ANG. to 5000 .ANG. A thick, is deposited on
the outer surface of integrated circuit portion 10 to separate and
electrically isolate that semiconductor based portion of the chip
from the magnetic sensing structures to be provided thereon.
Following the providing of such sensing structures, magnetic
shielding and flux concentration arrangements as paired pole
structures will be provided by magnetic material structures which
are typically formed of a mechanically hard but magnetically soft
material such as Sendust. An initial layer of Sendust, 12, is
provided on insulating layer 11 to a thickness of around 2
.mu.m.
[0025] A masking arrangement is then provided on this Sendust layer
which, after typical development procedures to provide selected
openings therein, has such openings therein where the Sendust below
is desired to be removed. Such removal is done by ion milling
which, with a suitably chosen mask, will result in the mask being
abraded at its edge in such a way during milling as to leave an
opening in the Sendust such that the remaining Sendust around the
opening has walls with an approximately 45.degree. angle slant as
shown in FIG. 2. The remaining portions of Sendust layer 12 of FIG.
1 again has a thickness of about 2 .mu.m and is shown in FIG. 2
where it has been redesignated 12'.
[0026] The resulting openings are filled with deposited silicon
nitride insulating material to the level of the upper surface of
Sendust layer 12' and an insulating material spacing layer, 13, is
deposited over the exposed surfaces of Sendust layer 12' and the
filler insulating material designated 13' in FIG. 3 (which may be
made even and flat by some lapping and chemical mechanical
polishing). Spacer layer 13 is typically of silicon nitride to a
thickness of 500 to 700 .ANG. thick.
[0027] On this insulating layer, a "giant magnetoresistive effect",
or GMR, sensing structure is next provided. A typical sensing
structure of this kind has a first composite ferromagnetic layer
provided on the exposed surface of insulating layer 13 (also as a
magnetic flux guide) comprising a deposited first strata of NiFeCo
(65%/15%/20% atomic %) of 40 .ANG. thickness covered by depositing
a second ferromagnetic strata of FeCo (95%/5% atomic %) thereon
with a thickness of 15 .ANG. with both deposited in an orienting
magnetic field to result in an easy axis parallel to the plane of
the figures, this second strata having a higher magnetic saturation
than the first strata to enhance the GMR effect. The magnetically
"softer" first strata having a lower magnetic saturation allows the
magnetization of the first composite layer to be reoriented to
various angles for changing the electrical resistance of the
resulting sensing structure by smaller externally applied magnetic
fields than would a layer formed of just the magnetically "harder"
second strata material. An intermediate layer of copper of 25 .ANG.
thickness is then deposited on the second strata of the first
composite ferromagnetic layer, and a second composite ferromagnetic
layer is thereafter deposited on this intermediate copper layer.
The second composite ferromagnetic layer is the same as the first
but provided in reverse order with a 15 .ANG. FeCo first strata
being initially deposited for enhancing the GMR effect followed by
depositing a 40 .ANG. thick second strata of NiFeCo to again yield
a composite ferromagnetic layer having a magnetization direction
sensitive to externally applied magnetic fields and also serving as
a flux guide.
[0028] A chrome silicon layer is then deposited to a thickness of
100 .ANG. as a protective layer for the GMR sensor structure, and
ion milling is used to remove the unwanted portions of this sensing
structure layer to leave the desired GMR sensing structure, 14,
which is shown in FIG. 3 but without the structural detail of that
layer being indicated there in view of its relative thinness. The
chrome/silicon material at the edges of the second composite
ferromagnetic layer where sensor electrical interconnections are
desired need not be removed because of the thinness of this layer
and its relatively good electrical conductivity. Openings are,
however, made by masking and etching steps in insulating layers 13
and 11, and in the protective passivation layer over integrated
circuit 10 so that the interconnections can extend down to and
interconnect with the circuitry in semiconductor integrated circuit
chip portion 10 such as an electronic amplifier. A layer of
titanium/tungsten is then deposited for a rear interconnection to
GMR sensing structure 14 followed by providing a patterned mask
through which unwanted portions of the titanium/tungsten
interconnection layer are removed to leave the desired sensor rear
interconnection, 15, as shown in FIG. 3.
[0029] A further 0.5 to 1 .mu.m thick insulating layer, 16, (not
shown) of silicon nitride is provided over GMR sensing structure
14, rear interconnection 15, and the exposed portions of insulating
layer 13. An opening is provided in layer 16 across sensor
structure 14 from Sendust layer 12' by so as to leave an opening in
layer 16 exposing a portion of sensing structure 14 toward the end
thereof opposite that in contact with rear interconnection 15. This
is accomplished by providing a suitably patterned mask followed by
ion milling which again, with a suitably chosen mask, will result
in the mask being abraded at its edge in such a way during milling
such that the remaining portions of layer 16 around the opening has
walls with an approximately 45.degree. angle slant as shown in FIG.
4. The remaining portions of insulating layer 16 of FIG. 4 still
has a thickness of 0.5 to 1 .mu.m and is shown in FIG. 4 designated
by 16'.
[0030] Thereafter, a further metal interconnection layer of
titanium/tungsten is deposited (not shown in FIG. 4) covering
insulating layer remainder 16' and the exposed portion of sensing
structure 14 to a thickness of 400 to m700 .ANG. for the purpose of
providing a front electrical interconnection to that structure.
Masking and etching are used to form this further metal layer into
a front interconnection, 15', to sensing structure 14 with the
result shown in FIG. 4. Finally, another Sendust layer, not shown
in FIG. 4, is deposited over metal interconnection layer 15' to a
thickness of around 2 .mu.m.
[0031] The structure of FIG. 4 with the final Sendust layer not
shown is then lapped on the left side to mechanically remove
material inwardly to a degree sufficient to leave the desired front
contact structure length followed by chemical mechanical polishing
with the results shown in FIG. 5 in which the final Sendust layer
is shown after lapping and polishing with the designation 17. The
resulting exposed left side surface of the device, 18, will be the
air bearing surface of the "read head" in operation (which can be
covered by a very thin layer of diamond-like carbon for wear
protection). Sendust structures 12' and 17 form a pair of magnetic
material pole structures or poles to provide magnetic shielding and
flux concentration about the gap around sensing structure 14
provided by insulating layer 13 and front interconnection 15' and
they are further separated from sensing structure 14 inwardly from
air bearing surface 18 than at that surface to reduce magnetic
field shunting from that sensing structure.
[0032] These paired poles 12' and 17 and sensing structure 14 thus
in part intersect a potion of air bearing surface 18 that is more
or less perpendicular to the major surfaces of semiconductor chip
portion 10 and insulating layer 11 supporting these poles and this
sensing structure. Additional and similar paired poles and sensing
structures are simultaneously fabricated on chip portion 10 and
insulating layer 11 intersecting air bearing surface 18 positioned
parallel to paired poles 12' and 17 and sensing structure 14
inwardly from the plane of FIG. 5 sufficiently close to one another
to each be over a separate track in the magnetic media passing
thereby during use.
[0033] Electrical current-to-magnetic signal storage transducers
(i.e. "write" heads) and magnetic signal flux-to-electric signal
retrieval transducers (i.e. "read" heads) are often desired so as
to be able to write and read, respectively, several parallel
tracks, say eight to sixteen, simultaneously, but as currently
provided are very complex hybrid assemblies. Nevertheless, there
are increasing demands on these heads both with respect to the rate
of data passing therethrough which is required to be ever higher,
and to the widths of the data tracks in the magnetic storage medium
which are always being sought to be made narrower and narrower to
thereby increase stored data density. Even though the "read heads"
described above aid in the achievement of higher data rates by
lowering parasitic capacitance along the recovered data
transmission path, this improvement may not be enough at a
sufficiently high data rate.
[0034] These design problems can be overcome by providing such
heads in monolithic integrated circuit chips rather than hybrid
assemblies as before, and by having the paired poles, and possibly
the sensing structures, intersect a chip surface as the air bearing
surface that is parallel to major semiconductor surfaces supporting
them to further shorten the recovered data transmission paths. The
read heads are again configured to have the plural heads provided
in these chips arrayed thereacross so as to be more or less
perpendicular to the direction taken by the plural data tracks in
the moving magnetic medium passing thereby during operation so as
to accommodate these heads interacting with the passing tracks.
Forming read heads right in the integrated circuit chip
intersecting the major surfaces thereof allows further shortening
of the data paths from those heads to the input amplifiers formed
in the semiconductor chip portion with relatively small path
parasitic capacitance. Providing the heads in such a chip
arrangement allows the techniques used for fabricating
semiconductor monolithic integrated circuit chips, which are well
developed, to also be used in fabricating such chips with heads,
both "read" and "write" types.
[0035] The resulting heads fabricated in such chips must each
include magnetic shielding thereabout, i.e. poles, to prevent
interaction with adjacent memory locations in the passing magnetic
medium. However, the flux involved at each selected memory location
adjacent a head must be drawn to extend inwardly into a
corresponding gap in such shielding in which this head is located
to permit the required interaction of that head with the magnetic
medium through the fields generated by track portions thereof. The
magnetic fields generated from stored datum at a location in the
magnetic medium, which otherwise have a strong field component
parallel to the planar major surface of the integrated circuit
chip, must instead be converted to have a strong field component
normal to the planar major surface of the integrated circuit chip
near each head in the shield structure thereabout which is then to
be sensed by a head structure that is more or less parallel to
these normal fields. Similarly, gaps must be provided in the
magnetic shielding adjacent writing inductive coils so the magnetic
fields generated thereby can extend outwardly into the magnetic
medium moving thereby.
[0036] With such heads being formed in monolithic integrated
circuit chips so as to allow conventional integrated circuits to be
formed in the semiconductor material that also serves as a
substrate for these head structures, local amplification circuits
can be provided as indicated above and connected directly to the
read heads to help to improve the signal-to-noise ratio of the
signals generated by the magnetic medium tracks moving by those
read heads. The resulting head and amplifier arrangement would
typically require ten interconnections with subsequent circuitry
but this can be reduced by sampling the signal from each and
multiplexing the data obtained through an output circuit, i.e. the
data from a retrieved digital word can be collected in parallel and
transmitted serially. In addition, data processing circuitry can
also be provided in the monolithic integrated circuit chip
semiconductor portion to permit checking for errors and to provide
some error correction to reduce or eliminate those errors.
[0037] A read head of this sort having interconnections on each
side thereof, i.e. an interconnection on either side of the read
head sensing layer, and so more or less on either side of a data
track passing therebelow in the moving magnetic medium, can be
formed starting on an insulator provided over an otherwise typical
monolithic semiconductor integrated circuit chip portion 10 as
shown in FIG. 6. This insulator separates the head structures from
the already fabricated semiconductor integrated circuit chip
portion 10. Various circuits for controlling the "read heads" while
obtaining and transmitting the data obtained thereby from a moving
magnetic medium passing these heads are contained in integrated
circuit semiconductor chip portion 10 which are to be in some
instances connected through the insulator to those heads. For
purposes of providing such read head structures, the insulator
indicated is provided by insulating layer 11, again typically of
silicon nitride with a thickness of 2500 .ANG. to 5000 .ANG., that
is deposited on the outer surface of integrated circuit
semiconductor chip portion 10 resulting from fabrication processing
to this point. Layer 11 serves as a further part of the substrate
including chip 10 supporting such "read heads". Shielding and flux
concentration will again be provided by magnetic material
structures which are typically formed of a mechanically hard but
magnetically soft material such as Sendust. Initial Sendust layer
12 is again provided on insulating layer 11, and to a thickness of
1 to 3 .mu.m.
[0038] This Sendust layer then has a masking arrangement provided
thereon which, after typical development procedures to provide
selected openings therein, has such openings therein located where
the Sendust below is desired to be removed down to insulating layer
11. Such removal is done by ion milling which, with a suitably
chosen mask, will result in the mask being abraded at its edge in
such a way during milling as to leave an opening in the Sendust so
that the remaining Sendust around the opening has walls with an
approximately 45.degree. angle slant as shown in FIG. 7. The
remaining portions of Sendust layer 12 of FIG. 6 has a thickness of
1 to 2 .mu.m and is shown in FIG. 7 where it has been redesignated
12'.
[0039] Thereafter, insulating layer 13, again of silicon nitride,
is deposited to a typical thickness of 500 .ANG. on the surface of
remaining portions of Sendust layer 12' and on the portions of
insulating layer 11 exposed in the Sendust layer openings. On
insulating layer 13, "giant magnetoresistive effect", or GMR,
sensing structure 14 is next provided. Sensing structure 14 is
provided here just as it was provided in the read device described
above as shown in FIG. 3. Openings are then again made in
insulating layers 13 and 11, and in the protective passivation
layer over integrated circuit semiconductor chip portion 10 so that
the interconnections can here too extend down to and interconnect
with the circuitry in integrated circuit semiconductor chip portion
10.
[0040] A layer of titanium/tungsten is then deposited for
interconnections to GMR sensing structure 14 followed by providing
a patterned mask through which unwanted portions of the
titanium/tungsten interconnection layer are removed to leave the
desired interconnections 15 as shown in FIG. 8. This figure shows a
section view taken along the middle of GMR sensing structure 14
between the edge interconnections thereto so that interconnection
15, on one end of sensing structure 14, appears in dashed line form
because of being inwardly from the plane of FIG. 8. Finally, a
further 500 .ANG. thick insulating layer 16 of silicon nitride is
provided over GMR sensing structure 14, interconnections 15, and
the exposed portions of insulating layer 13. The portion of layer
15 over the portion of sensing structure 14 near the plane of FIG.
8 is shown in solid line form, and the portion of that layer over
interconnection 15 is shown in dashed line form in being inward
from the plane of FIG. 8.
[0041] Upon completion of GMR sensing structure 14,
interconnections 15, and protective insulating layers 13 and 16
thereabout, final magnetic shielding and concentration layer 17 of
Sendust is deposited to a thickness of 1 to 2 .mu.m. The final
result following this step is also shown in FIG. 8. The structure
shown in FIG. 8 then has upper portions thereof mechanically lapped
away to provide a resulting partially vertical read head based on
GMR sensing structure 14. This lapping is followed by chemical
mechanical polishing of the surface remaining after the
lapping.
[0042] The result of the structure in FIG. 8 following the
mechanical lapping and polishing thereof is shown in FIG. 9 with
exposed surface 18 remaining after these steps forming the air
bearing surface for the read head which will be positioned adjacent
the magnetic medium (moving rapidly from left to right in FIG. 9)
in normal operation. Typically, a protective surface layer of very
thin diamond-like carbon will also be deposited on surface 18 (not
shown here) to form the final air bearing surface as a protection
against mechanical wearing during situations when the read head
comes into contact with the magnetic medium.
[0043] Sendust layer remnant 12' of FIG. 3 is redesignated as 12"
in FIG. 9 after its alteration due to the lapping, and similarly
insulating layers 13 and 16 have been redesignated 13' and 16' in
FIG. 9 with interconnections 15 being redesignated 15' and with GMR
sensing structure 14 in FIG. 8 being redesignated 14' in FIG. 9.
Also, Sendust layer 17 of FIG. 8 has been redesignated 17' in FIG.
9, these redesignations following the structural alterings
resulting from forming surface 18 common to all of the sensing
structures and paired pole structures fabricated simultaneously
with sensing structure 14' and pole structures 12" and 17', a
surface which is parallel to the major surfaces of semiconductor
chip portion 10 and insulating layer 11 supporting these poles and
sensing structures. Insulating layers 13' and 16' along with
interconnections 15' provide a gap between magnetic structures 12"
and 17' around read head sensing structure 14' to concentrate there
the flux generated in the magnetic medium moving by air bearing
surface 18 (separated by the diamond-like carbon layer mentioned
above) during typical operation. This flux will extend in magnetic
structures 12" and 17' along the gap to be parallel to much of
"read head" sensing structure 14' as a partially vertical sensor
before crossing therethrough to provide a high sensitivity
head.
[0044] An alternative "read head" structure arrangement is often
desired in integrated circuit chips 10 in which the circuit
interconnections are made at the front and the rear of the
partially vertical read head structure (as made to the front and
rear of the fully horizontal sensing structure of FIG. 5 viewed
with respect to the upper surface of integrated circuit
semiconductor chip portion 10 supporting the head) rather than at
either side thereof as they are in the "read head" structure shown
in FIG. 9. Such an alternative structure can be formed again in
semiconductor based monolithic integrated circuit chip portion 10
as it is in the fabrication process to this point by again having
insulating layer 11 thereon, though this time with some initial
shaping of that insulating layer as is shown in FIG. 10. This
shaping can be accomplished by providing successive masks followed
by ion milling leaving a 45.degree. first sloping edge coming up
from the bottom of that opening to a horizontal intermediate tier
level which in turn is followed by a further 45.degree. sloping
edge to the top of layer 11. The thickness of layer 11 at that
point might be on the order of 1.5 .mu.m with the thickness of the
layer at the point of the intermediate tier being between 7000 and
12,000 .ANG.. The thickness at the bottom of the opening in layer
11 where that layer is thinnest might be on the order of 2000 to
5000 .ANG.. The shaping allows reducing the pole thicknesses near
the gap at the air bearing surface to reduce magnetic field
shunting.
[0045] Thereafter, again Sendust layer 12, 1 to 2 .mu.m thick, is
deposited over shaped layer 11 to provide the final structure
result shown in FIG. 10. The structure in FIG. 10 is then lapped to
mechanically remove material at the upper surface thereof, followed
by chemical mechanical polishing, so as to leave approximately 1000
.ANG. of Sendust in layer 12 above the intermediate tier of layer
11 with the results shown in FIG. 11. The altering of insulating
layer 11 and Sendust layer 12 by such mechanical lapping and
polishing motivates redesignating them as layers 11' and 12',
respectively, in FIG. 11.
[0046] The surface resulting from the mechanical lapping and
polishing is then again masked and ion milling is used to remove a
portion of Sendust layer 12' and insulating layer 11' to provide an
opening again with a 45.degree. wall slant. This result is shown in
FIG. 12 where insulating layer 11' of FIG. 11 is redesignated 11"
in FIG. 12 after the opening provided therein by ion milling, and
Sendust layer 12' of FIG. 11 has been redesignated layer 12" in
FIG. 12.
[0047] Next, insulating layer 13, typically of silicon nitride, is
here again deposited to a thickness of 400 to 1000 .ANG. on the
exposed surface of Sendust layer 12" and the surface formed by the
opening in layer 11". On the resulting surface of insulating layer
13 a GMR sensing layer is again provided and sensing structure 14
is formed just as sensing structure 14 was provided in FIGS. 3 and
8 including the composite ferromagnetic layers therein serving as
magnetic flux guides. In a change from the fabrications of the
previously described structures associated with these last two
figures, the present structure as fabricated to this point is then
covered with insulating layer 16 (not shown) of silicon nitride to
a thickness of 2000 to 3000 .ANG. before any interconnection
structures are formed as shown in FIG. 13 for the purpose of
reducing the length of the sensing structure over which the front
interconnection contact extends to reduce electrical shunting of
that sensing structure. Masking and etching are then used to remove
a portion of insulating layer 16, which is thus redesignated 16' in
FIG. 13, to thereby expose the portion of sensing structure 14
above the midpoint of its covering on the 45.degree. wall shown in
that figure, and to provide other openings therein and in
insulating layers 13 and 11, and in the protective passivation
layer over integrated circuit semiconductor chip portion 10 so that
the interconnections can here again extend down to and interconnect
with the circuitry in integrated circuit semiconductor chip portion
10. Thereafter, a metal interconnection layer of titanium/tungsten
is deposited covering insulating layer remainder 16' and the
exposed portion of sensing structure 14 for the purpose of
providing a front electrical interconnection to that structure and
other interconnections. This interconnection layer is deposited to
a thickness of 400 to 1000 .ANG., and masking and etching are then
used to form the desired interconnection 15. Finally, Sendust layer
17 is deposited over metal interconnection 15 and the exposed
portions of insulating layers 13 and 16' to a thickness of around 2
.mu.m.
[0048] The structure of FIG. 13 is then lapped to mechanically
remove material down to the surface of Sendust layer 12" followed
by chemical mechanical polishing with the results shown in FIG. 14.
The resulting exposed surface of the device 18 will be the air
bearing surface in operation (which can again be covered by a very
thin layer of diamond-like carbon for wear protection) which is
common to all of the sensing structures and paired pole structures
fabricated simultaneously with sensing structure 14' and pole
structures 12" and 17', a surface which is parallel to the major
surfaces of semiconductor chip portion 10 and insulating layer 11
supporting these poles and sensing structures. As a result of the
lapping mechanical removal of material, insulating layer 13 of FIG.
13 is redesignated 13' in FIG. 14 as before, sensing structure 14
of FIG. 13 is redesignated 14' in FIG. 14 as before, metal and
front interconnection layer 15 of FIG. 13 is redesignated 15' in
FIG. 14 as before, and Sendust layer 17 of FIG. 13 is redesignated
17' in FIG. 14 as before. As can be seen, metal layer 15' becomes a
front contact to sensing structure 14' with the rear contact to
that layer not being shown here though formed more or less
concurrently therewith.
[0049] A further alternative "read head" structure arrangement with
the circuit interconnections made at the front and the rear of the
partially vertical read head structure can be provided using a
"spin dependent tunneling effect" sensing structure rather than a
GMR sensing structure. Such an alternative structure can be formed
again in semiconductor based monolithic integrated circuit chip
portion 10 as it is in the fabrication process to this point by
again having insulating layer 11 thereon, with again some initial
shaping of that insulating layer as is shown in FIGS. 10 through
12.
[0050] Thus, starting from the structure shown in FIG. 12,
insulating layer 13, typically of silicon nitride, is here again
deposited to a thickness of 400 to 1000 .ANG. on the exposed
surface of Sendust layer 12" and the surface formed by the opening
in layer 11". Masking and etching are then used to remove a portion
of insulating layer 13, which is thus redesignated 13' in FIG. 15,
to provide openings therein and in insulating layer 11, which is
thus redesignated 11'", and in the protective passivation layer
over integrated circuit semiconductor chip portion 10 so that
certain interconnections can here again extend down to and
interconnect with the circuitry in integrated circuit semiconductor
chip portion 10. Thereafter, a metal interconnection layer of
titanium/tungsten is deposited covering insulating layer remainder
13' for the purpose of providing a bottom electrical
interconnection to the sensing structure and perhaps other
interconnections. This interconnection layer is deposited to a
thickness of 400 to 1000 .ANG., and masking and etching are then
used to form the desired interconnection 15.
[0051] On the resulting surface of insulating layer 13' and on
interconnection 15 a "spin dependent tunneling effect" sensing
structure 14 is provided. A typical sensing structure of this kind
has a first "pinned" ferromagnetic layer provided on a "pinning"
antiferromagnetic layer that is provided on the exposed surface of
interconnection 15. This "pinning" layer is formed of CrPt Mn
(45%/45%/10% atomic %) deposited to a thickness of 200 to 300 .ANG.
and the "pinned" ferromagnetic layer is formed of NiFeCo
(65%/15%/20% atomic %) deposited to a 30 .ANG. thickness with both
deposited in an orienting magnetic field to result in an easy axis
parallel to the plane of the figures so that the magnetization of
the ferromagnetic layer will be essentially maintained in this
direction even in the presence of externally applied magnetic
fields. Ion milling is used to form this "pinning-pinned" layer
combination into a joint layer having the extent desired for the
sensing structure. Thereafter, 200 to 400 .ANG. of silicon nitride
is deposited with masking and etching then used to provide an
opening therein down to the "pinned" ferromagnetic layer. Aluminum
is then deposited to cover this ferromagnetic to thickness of 20
.ANG. which is then oxidized to form an intermediate layer of
aluminum oxide Al.sub.2O.sub.3 as the tunneling barrier with a
thickness of 15 .ANG..
[0052] Second and third ferromagnetic layers for flux guides
separated by a gap forming layer are thereafter deposited to have
magnetization directions which will react to externally applied
fields to change the electrical resistance through the resulting
sensing structure. The second ferromagnetic layer is deposited
formed of NiFeCo (65%/15%/20% atomic %) to a 50 .ANG. thickness,
the gap forming layer is typically formed of ruthenium, Ru,
deposited to a thickness of 30 .ANG. as it contributes to layer
smoothness although it could be formed of other conductive
materials such as copper (Cu) or tantalum (Ta), and the third
ferromagnetic layer is deposited formed of NiFeCo (65%/15%/20%
atomic %) again to a 50 .ANG. thickness with both ferromagnetic
layers being antiferromagnetically coupled to one another and
deposited in an orienting magnetic field to result in an easy axis
perpendicular to the plane of the figures. Ion milling is used to
form the barrier layer, the second and third ferromagnetic layers
and the gap forming layer to be coextensively over the
"pinning-pinned" joint layer combination and insulating layer 13'
above Sendust layer 12" as further shown in FIG. 15. Sensing
structure 14 is thus completed by the "pinning-pinned" joint layer
combination, 14", beneath the opened silicon nitride layer, 14'",
provided across the aluminum oxide barrier, 14"", from the second
ferromagnetic layer, 14.sup.v, to thus be adjacent to the magnetic
flux guide structure formed by second ferromagnetic layer 14.sup.v
as one flux guide, gap forming layer, 14.sup.vi, and the third
ferromagnetic layer, 14.sup.vii, as the other flux guide as these
flux guides are separated by the gap forming layer.
[0053] The present structure as fabricated to this point is then
covered with insulating layer 16 (not shown) of silicon nitride to
a thickness of 2000 to 3000 .ANG. before any interconnection
structures are formed as shown in FIG. 16 for the purpose of
reducing the length of the sensing structure over which the front
interconnection contact extends to reduce electrical shunting of
that sensing structure. Masking and etching are then used to remove
a portion of insulating layer 16, which is thus redesignated 16' in
FIG. 16, to thereby expose the portion of third ferromagnetic layer
14.sup.vii above the midpoint of its covering on the 45.degree.
wall shown in that figure, and to provide other openings therein
and in insulating layers 14'", 13 and 11, and in the protective
passivation layer over integrated circuit semiconductor chip
portion 10 so that the interconnections can here again extend down
to and interconnect with the circuitry in integrated circuit
semiconductor chip portion 10. Thereafter, a metal interconnection
layer of titanium/tungsten is deposited covering insulating layer
remainder 16' and the exposed portion of third ferromagnetic layer
14.sup.vii for the purpose of providing a front electrical
interconnection to that layer and other interconnections. This
interconnection layer is deposited to a thickness of 400 to 1000
.ANG., and masking and etching are then used to form the desired
interconnection 15'. Masking and etching are then used to remove a
portion of insulating layer 16' to thereby expose the portion of
third ferromagnetic layer 14.sup.vii to the right of sensing
structure 14. Finally, Sendust layer 17 is deposited over metal
interconnection 15' and the exposed portions of insulating layers
13' and 16' to a thickness of around 2 .mu.m and in the opening in
layer 16' to close a portion of the magnetic flux path to include
sensing structure 14 as shown in FIG. 16.
[0054] The structure of FIG. 16 is then lapped to mechanically
remove material down to the surface of Sendust layer 12" followed
by chemical mechanical polishing with the results shown in FIG. 17.
As a result of the lapping mechanical removal of material,
insulating layer 13' of FIG. 16 is redesignated 13.sup.x in FIG.
17, silicon nitride layer 14'" of FIG. 16 is redesignated 14.sup.x
in FIG. 17, aluminum oxide barrier 14"" of FIG. 16 is redesignated
14.sup.xi in FIG. 17, second ferromagnetic layer 14.sup.v of FIG.
16 is redesignated 14.sup.xii in FIG. 17, gap forming layer
14.sup.vi of FIG. 16 is redesignated 14.sup.xiii in FIG. 17, and
third ferromagnetic layer 14.sup.vii of FIG. 16 is redesignated
14.sup.xiiii in FIG. 17, metal and front interconnection layer 15'
of FIG. 16 is redesignated 15.sup.x in FIG. 17, and Sendust layer
17 of FIG. 16 is redesignated 17' in FIG. 17 as before. As can be
seen, metal layer 15.sup.x becomes a front interconnection contact
to flux guides 14.sup.xii and 14.sup.xiiii and so to sensing
structure 14 along with bottom interconnection contact 15 thereto.
The resulting exposed surface 18 of the device after lapping and
polishing will be the air bearing surface in operation (which can
again be covered by a very thin layer of diamond-like carbon for
wear protection) which is common to all of the sensing structures
and paired pole structures fabricated simultaneously with sensing
structure 14 and pole structures 12" and 17', a surface which again
is parallel to the major surfaces of semiconductor chip portion 10
and insulating layer 11 supporting these poles and sensing
structures.
[0055] FIG. 18 shows a plan view of air bearing surface 18 as it
might result from fabricating "read head" structures like the one
shown in FIG. 9 although they could just as well instead be "read
head" structures like the ones shown in FIGS. 14 or 17. The
magnetic media in operation would be moving past surface 18 in FIG.
18 from top to bottom, or vice versa. Not only can a pair of
separate sensing structures, 19 and 20, each formed in the manner
shown in FIG. 9, be provided side by side to each be over an
adjacent data track in the magnetic medium moving thereby, multiple
structures for sensing along such tracks can also be provided.
[0056] Thus, separate sensing structures or read heads, 20', 20",
20'", 20.sup.iv, 20.sup.v and 20.sup.vi, can be provided directly
in line with sensing structure 20 along the track path thereby so
that each can sense directly over a single data track passing under
each of them and head 20. Processing the results from each of these
individual heads by adding their sensed signals together after a
suitable time delay in each with respect to the preceding one will
give a composite signal result having a larger signal-to-noise
ratio since some of the noise from each head will cancel while all
of the signals will add.
[0057] Similarly, to aid in maintaining the position of a read head
over a data track, several sensing structures or read heads, 19',
19", 19'" and 19.sup.iv, can be used with head 19, but rather than
being in line therewith along a track path through that head, each
is offset perpendicular to that track path from the preceding head
in the string. As a result, a substantial portion on each side of a
head positioning track in the magnetic medium moving thereby (which
may be concentric with data tracks on one or both sides thereof
also moving by as shown in FIG. 19) passes under these heads to
thereby provide position error signals from one or more of the
other heads in the set whenever the data track is following a path
that is offset from the center one of this set of these offset read
heads, here head 19". Alternatively, fluctuating path deviations
can be measured in this set of offset read heads with the head
signals combined after suitable delays so as to get a full track
signal even though there are fluctuations of a data track from
following a data track path passing by the center head this set.
Further, as shown in FIG. 20, a set of separate sensing structures
or read heads 20 otherwise in a line across adjacent tracks can
each be rotated at an angle with respect to that line and so moved
closer together along that line to permit even closer positioned
tracks in the magnetic media moving thereby for greater track
density in that media (which can also be provided by the
arrangement of sensing structures or read heads, 19', 19", 19'" and
19.sup.iv shown in FIG. 18).
[0058] Write heads can be provided in the same monolithic
integrated circuit arrangement in which the read heads shown in
FIGS. 4 and 9 are provided. Thus, from the structure of FIG. 6,
Sendust layer 12 is shown in FIG. 21 of a thickness of 4 to 7 .mu.m
having a opening provided therein, through masking and ion milling,
that does not go all the way down to insulating layer 11 but
instead leaves a Sendust material bottom of 2 .mu.m and a
45.degree. slant wall. Sendust layer 12 of FIG. 1 is redesignated
12' in FIG. 21. Insulating layer 13 provided of silicon nitride
over the bottom of the opening in Sendust layer 12' to a thickness
of 1 .mu.m as is also shown in FIG. 21. A planar inductive coil,
21, formed of copper to thickness of 1 to 2 .mu.m is formed on the
surface of insulating layer 13 with appropriate interconnections
through insulating layer 13, Sendust layer 12', insulating layer 11
and the protective passivation layer over integrated circuit 10 to
the circuits in chip 10 for providing the currents through coil 21
representing the data to be stored in magnetic medium moving by the
chip. Coil 21 is covered by silicon nitride insulating layer 15 in
FIG. 21 to nearly the upper surface of Sendust layer 12'.
[0059] Thereafter, insulating layers 15 and 13 are shaped by
masking and ion milling as shown in FIG. 22 reducing the thickness
of layer 15 over coil 21 to around 1 .mu.m, and leaving a portion
thereof on the upper part of the 45.degree. slant wall of Sendust
layer 12' having a thickness of 0.1 .mu.m perpendicular to that
wall. Sendust layer 17 is then formed over the resulting shaped
structure of insulating layers containing coil 21 to a thickness of
around 2 .mu.m. Insulating layer 13 of FIG. 21 is redesignated 13'
in FIG. 22 and insulating layer 15 of FIG. 21 is redesignated 15'
in FIG. 22.
[0060] Once again, lapping is used to mechanically remove surface
materials to result in the structure shown in FIG. 23 with surface
18 resulting from the lapping and the subsequent chemical
mechanical polishing being the air bearing surface. Sendust layer
12' of FIG. 22 is redesignated 12" in FIG. 23 with a remaining
thickness of 4 to 7 .mu.m, and insulating layer 15' of FIG. 22 is
redesignated 15" in FIG. 23, and finally Sendust layer 17 of FIG.
22 is redesignated 17' in FIG. 23 with a remaining thickness of 1
to 2 .mu.m. The resulting structure provides a flux concentration
gap about layer 15" where it occurs narrowly between Sendust layers
12" and 17'. Except for this gap, coil 21 is surrounded by Sendust
on all sides to concentrate the flux induced by currents
therethrough in this gap to result in a flux field extending
outward from this gap at air bearing surface 18.
[0061] Although the present invention has been described with
reference to preferred embodiments, workers skilled in the art will
recognize that changes may be made in form and detail without
departing from the spirit and scope of the invention.
* * * * *