U.S. patent application number 09/336300 was filed with the patent office on 2002-01-31 for thin film conductor layer, magnetoresistive element using the same and method of producing thin film conductor layer.
Invention is credited to KANNO, HIROYUKI.
Application Number | 20020012206 09/336300 |
Document ID | / |
Family ID | 16152368 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020012206 |
Kind Code |
A1 |
KANNO, HIROYUKI |
January 31, 2002 |
THIN FILM CONDUCTOR LAYER, MAGNETORESISTIVE ELEMENT USING THE SAME
AND METHOD OF PRODUCING THIN FILM CONDUCTOR LAYER
Abstract
In a magnetoresistive element, deposition of a conductor layer
in a DC magnetron sputtering apparatus causes application of
tensile stress to the conductor layer, causing the problem of
readily producing separation of the conductor layer. In the present
invention, a conductor layer is formed so that the crystal face
spacing in the direction perpendicular to the film plane is larger
than the crystal face spacing of a bulk material. This permits
application of compression stress to the conductor layer,
preventing separation of the conductor layer.
Inventors: |
KANNO, HIROYUKI;
(NIIGATA-KEN, JP) |
Correspondence
Address: |
BRINKS HOFER GILSON & LIONE
P.O. BOX 10395
CHICAGO
IL
60610
US
|
Family ID: |
16152368 |
Appl. No.: |
09/336300 |
Filed: |
June 21, 1999 |
Current U.S.
Class: |
360/322 ;
204/192.34 |
Current CPC
Class: |
G11B 2005/3996 20130101;
G11B 5/40 20130101; H01F 10/324 20130101; H01F 41/306 20130101;
B82Y 10/00 20130101; B82Y 25/00 20130101; B82Y 40/00 20130101; G11B
5/3903 20130101; G01R 33/093 20130101 |
Class at
Publication: |
360/322 ;
204/192.34 |
International
Class: |
G11B 005/39 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 30, 1998 |
JP |
10-184391 |
Claims
What is claimed is:
1. A thin film conductor layer comprising a thin film made of a
metallic material, wherein the crystal face spacing in the
direction perpendicular to the film plane thereof is not less than
the crystal face spacing of a bulk material made of the same
metallic material as the conductor layer in the direction
perpendicular to the film plane thereof.
2. A thin film conductor layer according to claim 1, wherein the
metallic material comprises bcc-structure Cr, and the (110) face
spacing of the conductor layer in the direction perpendicular to
the film plane thereof is 2.039 angstroms or more.
3. A thin film conductor layer according to claim 1, wherein an
under layer is formed on the lower side of the thin film conductor
layer.
4. A thin film conductor layer according to claim 3, wherein the
under layer comprises .beta.-phase Ta having the (002) crystal face
perpendicular to the film plane thereof.
5. A thin film conductor layer according to claim 2, wherein an
under layer is formed on the lower side of the thin film conductor
layer.
6. A thin film conductor layer according to claim 5, wherein the
under layer comprises .beta.-phase Ta having the (002) crystal face
perpendicular to the film plane thereof.
7. A magnetoresistive element comprising: a laminate comprising an
antiferromagnetic layer, a pinned magnetic layer formed in contact
with the antiferromagnetic layer so that the direction of
magnetization is pinned by an exchange coupling magnetic field with
the antiferromagnetic layer, and a nonmagnetic conductive layer
formed between the pinned magnetic layer and a free magnetic layer:
and a thin film conductor layer formed on either side of the
laminate; wherein the thin film conductor layer is formed so that
the crystal face spacing in the direction perpendicular to the film
plane thereof is not less than the crystal face spacing of a bulk
material made of the same metallic material as the conductor layer
in the direction perpendicular to the film plane thereof.
8. A magnetoresistive element according to claim 7, wherein the
thin film conductor layer made of the metallic material comprises
bcc-structure Cr, and the (110) face spacing of the conductor layer
in the direction perpendicular to the film plane thereof is 2.039
angstroms or more.
9. A magnetoresistive element according to claim 8, wherein an
under layer is formed on the lower side of the thin film conductor
layer.
10. A magnetoresistive element according to claim 9, wherein the
under layer comprises .beta.-phase Ta having the (002) crystal face
perpendicular to the film plane thereof.
11. A magnetoresistive element according to claim 7, wherein an
under layer is formed on the lower side of the thin film conductor
layer.
12. A magnetoresistive element according to claim 11, wherein the
under layer comprises .beta.-phase Ta having the (002) crystal face
perpendicular to the film plane thereof.
13. A magnetoresistive element according to claim 7, wherein the
thin film conductor layer is exposed from the side opposite to a
recording medium.
14. A magnetoresistive element comprising: a laminate comprising a
magnetoresistive layer and a soft magnetic layer both of which are
deposited with a nonmagnetic layer therebetween; and a thin film
conductor layer formed on either side of the laminate; wherein the
thin film conductor layer is formed by using a metallic material so
that the crystal face spacing in the direction perpendicular to the
film plane thereof is not less than the crystal face spacing of a
bulk material made of the same metallic material as the conductor
layer in the direction perpendicular to the film plane thereof.
15. A magnetoresistive element according to claim 14, wherein the
thin film conductor layer made of the metallic material comprises
bcc-structure Cr, and the (110) face spacing of the conductor layer
in the direction perpendicular to the film plane thereof is 2.039
angstroms or more.
16. A magnetoresistive element according to claim 15, wherein an
under layer is formed on the lower side of the thin film conductor
layer.
17. A magnetoresistive element according to claim 16, wherein the
under layer comprises .beta.-phase Ta having the (002) crystal face
perpendicular to the film plane thereof.
18. A magnetoresistive element according to claim 14, wherein an
under layer is formed on the lower side of the thin film conductor
layer.
19. A magnetoresistive element according to claim 18, wherein the
under layer comprises .beta.-phase Ta having the (002) crystal face
perpendicular to the film plane thereof.
20. A magnetoresistive element according to claim 14, wherein the
thin film conductor layer is exposed from the side opposite to a
recording medium.
21. A method of producing a thin film conductor layer comprising
depositing a thin film conductor layer on a substrate in a DC
magnetron sputtering apparatus with the DC bias supplied to the
substrate side.
22. A method of producing a thin film conductor layer according to
claim 21, wherein the crystal face spacing of the thin film
conductor layer in the direction perpendicular to the film plane is
adjusted by the voltage value of the DC bias.
23. A method of producing a thin film conductor layer according to
claim 21, wherein the metallic material comprises bcc-structure Cr,
and the (110) face spacing of the conductor layer in the direction
perpendicular to the film plane thereof is 2.039 angstroms or
more.
24. A method of producing a thin film conductor layer according to
claim 21, wherein an under layer is formed on the lower side of the
thin film conductor layer.
25. A method of producing a thin film conductor layer according to
claim 21, wherein the under layer comprises phase Ta having the
(002) crystal face perpendicular to the film plane thereof.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a conductor layer, for
example, formed in a magnetoresistive element, for example, for
detecting an external magnetic field. Particularly, the present
invention relates to a thin film conductor layer capable of
preventing separation, a magnetoresistive element using the thin
film conductor layer, and a method of producing a thin film
conductor layer.
[0003] 2. Description of the Related Art
[0004] Magnetoresistive elements include an AMR (anisotropic
magnetoresistive) element utilizing anisotropic magnetoresistance,
and a GMR (giant magnetoresistive) element utilizing a giant
magnetoresistance. A high rate of resistance change can be obtained
by a GMR element, as compared with an AMR element.
[0005] Of such GMR elements, a spin-valve type thin film element
having a relatively simple structure and showing a change in
resistance with a weak external magnetic field has the simplest
structure comprising four layers including an antiferromagnetic
layer, a pinned magnetic layer, a nonmagnetic conductive layer and
a free magnetic layer.
[0006] FIG. 9 is a sectional view of a conventional spin-valve type
thin film element as viewed from the side opposite to a recording
medium.
[0007] An under layer 6 is made of Ta or the like, and an
antiferromagnetic layer 1, a pinned magnetic layer 2, a nonmagnetic
conductive layer 3, a free magnetic layer 4, and a protective layer
7 are deposited in turn on the under layer 6. As shown in FIG. 9,
the antiferromagnetic layer 1 and the pinned magnetic layer 2 are
formed in contact with each other, and the pinned magnetic layer 2
is pinned by an exchange coupling magnetic field generated in the
interface between the antiferromagnetic layer 1 and the pinned
magnetic layer 2, for example, in the Y direction shown in FIG.
9.
[0008] Referring to FIG. 9, hard magnetic bias layers 5 are formed
on both sides of the laminate ranging from the under layer 6 to the
protective layer 7 so that magnetization of the free magnetic layer
4 is arranged in the X direction shown in the drawing by a bias
magnetic field from the hard magnetic bias layers 5.
[0009] Further, a main conductive layer 9 is formed on each of the
hard magnetic bias layers 5 through an adhesive layer 8, and an
adhesive layer (protective layer) 10 is formed on the main
conductive layer 9. Hereinafter, the adhesive layers 8 and 10, and
the main conductive layers 9 are sometimes referred to as the
general term "conductor layer". The adhesive layers 8 and 10 are
made of, for example, Cr, W, Nb, or the like, and the main
conductive layers 9 are made of .alpha.-Ta, Au, Ag, Cu, or the
like.
[0010] The layers of the above-described conventional spin-valve
type thin film element are formed by sputtering or vapor deposition
using an existing sputtering apparatus or the like. Particularly, a
DC magnetron sputtering apparatus exhibiting excellent thickness
reproducibility is preferably used as the sputtering apparatus. The
DC magnetron sputtering apparatus comprises a substrate and an
electrode unit, which are arranged in the apparatus, and a magnet
provided in the electrode unit. The electrode unit comprises a DC
power source provided therein so that when the DC power source is
operated, magnetron discharge is produced due to the relation
between an electric field and a magnetic field to sputter a target
provided on the electrode unit, to form a thin film (laminate) on
the substrate opposite to the target.
[0011] However, deposition of the conductor layers of the
spin-valve type thin film element by the DC magnetron sputtering
apparatus has a problem in which tensile stress is applied to the
conductor layers in the direction parallel to the film plane,
causing separation of the conductor layers. Since tensile stress is
applied to the conductor layers, it is difficult to increase the
thickness of the conductor layers to a predetermined value.
[0012] Furthermore, in the conventional thin film element, the main
conductor layers 9 are made of, for example, Au, Ag, or the like,
which is a very soft metallic material. Therefore, when the surface
opposite to a recording medium is scratched by dry etching after
film deposition to exposure the structure of the spin-valve type
thin film element shown in FIG. 9 to the outside, the main
conductor layers 9 are sagged to cause a recess in the main
conductor layers 9. The occurrence of such sagging undesirably
causes, for example, a short-circuit.
SUMMARY OF THE INVENTION
[0013] The present invention has been achieved for solving the
problems of the conventional element, and an object of the present
invention is to provide a thin film conductor layer formed by
applying compressive stress thereto for preventing separation of
the conductor layer, a magnetoresistive element using the thin film
conductor layer, and a method of producing a thin film conductor
layer.
[0014] The present invention provides a conductor layer comprising
a thin film made of a metallic material, wherein the crystal face
spacing in the direction perpendicular to the film plane is larger
than that of a bulk material made of the same metallic material as
the conductor layer in the direction perpendicular to the film
plane.
[0015] In the present invention, preferably, the metallic material
comprises bcc-structure Cr, and the (110) spacing of the conductor
layer in the direction perpendicular to the film plane thereof is
2.039 angstroms or more.
[0016] Also, an under layer is preferably formed below the thin
film conductor layer, which is preferably made of phase Ta having
the (002) face perpendicular to the film plane is.
[0017] The present invention also provides a magnetoresistive
element comprising a laminate comprising an antiferromagnetic
layer, a pinned magnetic layer formed in contact with the
antiferromagnetic layer so that the direction of magnetization is
pinned by an exchange coupling magnetic field with the
antiferromagnetic layer, and a nonmagnetic conductive layer formed
between the pinned magnetic layer and a free magnetic layer; and
the thin film conductor layer formed on either side of the
laminate.
[0018] The present invention further provides a magnetoresistive
element comprising a laminate comprising a magnetoresistive layer
and a soft magnetic layer which are laminated through a nonmagnetic
layer, and the thin film conductor layer formed on either side of
the laminate.
[0019] In the present invention, the thin film conductor layer is
preferably exposed from a surface opposite to a recording
medium.
[0020] The present invention further provides a method of producing
a thin film conductor layer, comprising depositing the thin film
conductor layer on a substrate in a DC magnetron sputtering
apparatus with DC bias supplied to the substrate side.
[0021] In the present invention, the crystal face spacing of the
thin film conductor layer in the direction perpendicular to the
film plane thereof is adjusted by the voltage value of the DC
bias.
[0022] In a conventional conductor layer (thin film conductor
layer) formed in, for example, a magnetoresistive element, tensile
stress is applied thereto, readily causing separation of the
conductor layer. Therefore, in the present invention, the crystal
face spacing of the conductor layer is appropriately adjusted to
apply compression stress to the conductor layer.
[0023] As a result of examination of the relation between stress
and the crystal face spacing of a metallic material used for a
conductor layer in the direction perpendicular to the film plane
thereof, the inventors found that the stress applied to the
conductor layer changes from tensile stress to compression stress
with increases in the crystal face spacing. Particularly, it was
found from experiment that the crystal face spacing with which
tensile stress is transferred to compression stress is the same as
the crystal face spacing of a bulk material made of the metallic
material in the direction perpendicular to the film plane thereof.
In the present invention, therefore, the crystal face spacing of
the conductor layer comprising a thin film in the direction
perpendicular to the film plane thereof is not less than the
crystal face spacing of a bulk material in the direction
perpendicular to the film plane thereof.
[0024] Although, in a conventional element, a soft metallic
material such as Au or the like is used for the main conductor
layers 9 shown in FIG. 9, such a metallic material causes "sagging"
when exposed from a surface opposite to a recording medium, thereby
causing a danger of a short circuit. In the present invention,
therefore, a hard metallic material such as Cr is preferably used
in place of a soft metallic material such as Au, so that the danger
of causing "sagging" can be prevented.
[0025] As a method of forming a conductor layer comprising a thin
film in which the crystal face spacing in the direction
perpendicular to the film plane is not less than the crystal face
spacing of a bulk material, the crystal face spacing of the thin
film conductor layer can be increased by applying a DC bias to the
substrate side in the magnetron sputtering apparatus used.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a sectional view of a magnetoresistive element
(spin-valve type thin film element) in accordance with a first
embodiment of the present invention as viewed from the side
opposite to a recording medium;
[0027] FIG. 2 is a sectional view of a magnetoresistive element
(spin-valve type thin film element) in accordance with a second
embodiment of the present invention as viewed from the side
opposite to a recording medium;
[0028] FIG. 3 is a sectional view of a magnetoresistive element
(spin-valve type thin film element) in accordance with a third
embodiment of the present invention as viewed from the side
opposite to a recording medium;
[0029] FIG. 4 is a sectional view of a magnetoresistive element
(AMR element) in accordance with a fourth embodiment of the present
invention as viewed from the side opposite to a recording
medium;
[0030] FIG. 5 is a drawing showing the configuration of a DC
magnetron sputtering apparatus used in the present invention;
[0031] FIG. 6 is a graph showing the relation between the strength
of the DC bias applied to the substrate side in a DC magnetron
sputtering apparatus and the stress applied to conductor layer (Cr
film);
[0032] FIG. 7 is a graph showing the relation between the strength
of the DC bias applied to the substrate side in a DC magnetron
sputtering apparatus and the (110) face spacing of a conductor
layer (Cr film);
[0033] FIG. 8 is a graph showing the relation between the (110)
face spacing of a conductor layer (Cr film) and the film stress
applied to the Cr film; and
[0034] FIG. 9 is a sectional view of a conventional
magnetoresistive element (spin-valve typ thin film element) as
viewed from the side opposite to a recording medium.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0035] FIG. 1 is a sectional view showing the structure of a
spin-valve type thin film element in accordance with a first
embodiment of the present invention as viewed from the side
opposite to a recording medium.
[0036] The spin-valve type thin film element is provided at the
trailing side end of a floating slider provided on a hard disk
device, for sensing a record magnetic field of a hard disk. A
magnetic recording medium such as a hard disk or the like is moved
in the Z direction, and a leakage magnetic field in the Y direction
is supplied from the magnetic recording medium.
[0037] In FIG. 1, the lowermost layer is an under layer 15 made of
a nonmagnetic material such as Ta (tantalum) or the like. An
antiferromagnetic layer 16, a pinned magnetic layer 17, a
nonmagnetic conductor layer 18, and a free magnetic layer 19 are
laminated on the under layer 15. A protective layer 20 of Ta is
formed on the free magnetic layer 19.
[0038] The antiferromagnetic layer 16 may be made of a material
conventionally used as antiferromagnetic material, for example,
such as an NiMn alloy film, or the like. However, in the present
invention, it is preferable to use an antiferromagnetic material
comprising a platinum group element, such as a PtMn alloy film or
the like, which has a high blocking temperature and produces a high
exchange coupling magnetic field in the interface with the pinned
magnetic layer. The pinned magnetic layer 17 and the free magnetic
layer 19 comprise, for example, a NiFe alloy film, a CoFe alloy
film, a Co film, CoNiFe alloy film or a CoNi alloy film. The
nonmagnetic conductive layer 18 comprises a Cu film or the
like.
[0039] The pinned magnetic layer 17 and the antiferromagnetic layer
16 are formed in contact with each other so that magnetization of
the pinned magnetic layer 17 is pinned in the Y direction shown in
FIG. 1 by an exchange coupling magnetic field produced in the
interface with the antiferromagnetic layer 16.
[0040] As shown in FIG. 1, hard magnetic bias layers 21 are formed
on both sides of a laminate ranging from the under layer 15 to the
protective layer 20. The hard magnetic bias layers 21 are made of,
for example, a CoPt alloy or CoCrPt alloy. The hard magnetic bias
layers 21 are magnetized, for example, in the X direction shown in
FIG. 1 so that magnetization of the free magnetic layer 19 is
oriented in the X direction by a bias magnetic field from the hard
magnetic bias layers 21.
[0041] In the present invention, as shown in FIG. 1, a conductor
layer (thin film conductor layer) 23 is formed on each of the hard
magnetic bias layer 21 through an under layer 22. The conductor
layers 23 are made of a metallic material, and preferably a Cr
film.
[0042] The conductor layers 23 shown in FIG. 1 are formed so that
the crystal face spacing in the direction (the Z direction shown in
FIG. 1) perpendicular to the film plane is not less than the
crystal face spacing of a bulk material made of the same metallic
material as the conductor layers 23 in the direction perpendicular
to the film plane thereof. The method of adjusting the crystal face
spacing is described later.
[0043] In the present invention, since the conductor layers 23 are
formed so that the crystal face spacing in the direction
perpendicular to the film plane is vertically increased, and thus
compression stress is applied in parallel with the film plane. In
the deposition of the conductor layers 23 with the compression
stress applied, the resultant conductor layers 23 are liable to
extend in the direction of the film plane due to repulsion against
the compression stress. However, compression stress is applied to
the conductor layers 23, which are liable to extend in the
direction of the film plane, from the layer below the conductor
layers 23. By applying compression stress to the conductor layers
23, the conductor layers 23 are adhered to the lower layer, thereby
preventing separation of the conductor layers 23. The application
of compression tress to the conductor layers 23 also facilitates
the formation of the conductor layers 23 having a predetermined
thickness, thereby decreasing a DC resistance (DCR).
[0044] As described above, in the present invention, the conductor
layers 23 are preferably made of a Cr film. However, the crystal
structure of the deposited Cr film is generally bcc structure
(body-centered cubic structure), and the (110) crystal face is
perpendicular to the film plane. In the present invention, in the
conductor layers 23 made of a Cr film, the (110) face spacing is
preferably 2.039 angstroms or more. Since a Cr bulk material has a
(110) face spacing of 2.039 angstroms, the (110) face spacing of
the Cr thin film is controlled to 2.039 angstroms or more to apply
compression stress to the Cr film, thereby preventing separation of
the Cr film. In addition, Cr is inexpensive, as compared with Au
conventionally used for the conductor layers 23. Furthermore, the
use of Au for the conductor layers 23 readily causes sagging and
thus a recess when the film structure shown in FIG. 1 is exposed to
the outside by dry-etching the side opposite to the recording
medium. However, Cr is a harder metallic material than Au, and thus
the formation of the conductor layers 23 by using the Cr film can
prevent "sagging" of the conductor layers 23.
[0045] In the present invention, as shown in FIG. 1, the under
layers 22 are preferably respectively formed between the hard
magnetic bias layers 21 and the conductor layers 23, and the under
layers 22 preferably comprise a P-phase Ta film (referred to as a
"i-Ta film" hereinafter) in which the (002) crystal face is
perpendicular to the film plane. The under layers 22 are formed to
a thickness of, for example, about 50 angstroms. By forming the
under layer 23 comprising a .beta.-Ta film under each of the
conductor layers 23, it is possible to improve the orientation of
the conductor layers 23, and decrease the resistivity thereof. For
example, without the under layers 22 of .beta.-Ta, the conductor
layers 23 comprising a Cr film have a resistivity of about 32
(.mu..OMEGA.m), while with the under layers 22 of .beta.-Ta formed,
the conductor layers 23 comprising a Cr film have a resistivity of
about 27 (.mu..OMEGA.m), thereby decreasing resistivity. The under
layers 22 comprising a .beta.-Ta film also exhibit excellent
corrosion resistance, simplifying the production process.
Conventionally, in some cases, an a-Ta film is used as a conductor
layer, and deposition of the .alpha.-Ta film requires introduction
of oxygen into an apparatus. However, as in the present invention,
when .beta.-Ta is deposited to form the under layers 22, there is
no need to introduce oxygen, thereby realizing simplification of
the production process.
[0046] In the spin-valve type thin film element shown in FIG. 1, a
stationary current (sensing current) is supplied to the free
magnetic layer 19, the nonmagnetic conductive layer 18 and the
pinned magnetic layer 17 from the conductor layers 23, and a
magnetic field is applied to these layers from the recording medium
in the Y direction to change the magnetization direction of the
free magnetic layer 19 from the X direction to the Y direction. At
the same time, electrons which move from one of the free magnetic
layer 19 and the pinned magnetic layer 17 to the other layer are
scattered in the interface between the nonmagnetic conductive layer
18 and the pinned magnetic layer 17, or the interface between the
nonmagnetic conductive layer 18 and the free magnetic layer 19 to
cause a change in electric resistance. As a result, the voltage is
changed to obtain detecting output.
[0047] FIG. 2 is a sectional view of a spin-valve type thin film
element in accordance with a second embodiment of the `present
invention as viewed from the side opposite to a recording
medium.
[0048] The spin-valve type thin film element comprises a film
structure comprising an under layer 30, a free magnetic layer 31, a
nonmagnetic conductive layer 32, a pinned magnetic layer 33, an
antiferromagnetic layer 34, and a protective layer 35, which are
formed in this order from below to form a laminate (referred to as
"spin valve films" hereinafter) ranging from the under layer 30 to
the protective layer 35; and a hard magnetic bias layer 36, an
under layer 37 and a conductor layer 38 which are deposited on
either side of the laminate.
[0049] Like in the conductor layers 32 of the spin-valve type thin
film element shown in FIG. 1, in the spin valve type thin film
element shown in FIG. 2, the conductor layers 38 are formed so that
the crystal face spacing in the direction (the Z direction shown in
the drawing) perpendicular to the film plane is not less than the
crystal face spacing of a bulk material in the direction
perpendicular to the film plane thereof, and compression stress is
thus applied to the deposited conductor layers 38. Therefore, the
conductor layers 38 are adhered to the under layers, preventing
separation of the conductor layers 38.
[0050] The conductor layers 38 preferably comprise a Cr film, and
the (110) face spacing in the direction perpendicular to the film
plane is preferably 2.039 angstroms or more.
[0051] In the present invention, as shown in FIG. 2, the under
layers 37 comprising a .beta.-Ta film are preferably respectively
formed between the hard magnetic bias layers 36 and the conductor
layers 38. By forming the under layers 37 under the conductor
layers 38, it is possible to improve the orientation of the
conductor layers 38, and decrease the resistivity of the conductor
layers 38.
[0052] FIG. 3 is a sectional view of a spin-valve type thin film
element in accordance with a third embodiment of the present
invention as viewed from the side opposite to a recording
medium.
[0053] The spin-valve type thin film element is referred to as a
dual spin-valve type thin film element, and permits the achievement
of a high rate of change in resistance, as compared with the
spin-valve type thin film elements (single spin-valve type thin
film elements) respectively shown in FIGS. 1 and 2.
[0054] The spin-valve type thin film element shown in FIG. 3 has a
film structure comprising an under layer 40, an antiferromagnetic
layer 41, a pinned magnetic layer 42, a nonmagnetic conductive
layer 43, a free magnetic layer 44, a nonmagnetic conductive layer
45, a pinned magnetic layer 46, an antiferromagnetic layer 47 and a
protective layer 48, which are deposited in this order from below.
A hard magnetic bias layer 49, an under layer 50 and a conductor
layer 51 are deposited on both sides of a laminate ranging from the
under layer 40 to the protective layer 48.
[0055] In the spin-valve type thin film element shown in FIG. 3,
the conductor layers 51 are formed so that the crystal face spacing
in the direction (the Z direction shown in the drawing)
perpendicular to the film plane is not less than the crystal face
spacing of a bulk material of a metallic material, which forms the
conductor layers 51, in the direction perpendicular to the film
plane thereof, and compression stress is applied to the deposited
conductor layers 51. Therefore, the conductor layers 51 are adhered
to the under layers, preventing separation of the conductor layers
51.
[0056] The conductor layers 51 are preferably made of a Cr film,
and the (110) face spacing in the direction perpendicular to the
film plane is preferably 2.039 angstroms or more.
[0057] In the present invention, as shown in FIG. 3, the under
layers 50 made of a .beta.-Ta film are preferably respectively
formed between the hard magnetic bias layers 49 and the conductor
layers 51. By forming the under layers 50 below the conductor
layers 51, it is possible to improve the orientation of the
conductor layers 51 and decrease the resistivity of the conductor
layers 51.
[0058] FIG. 4 is a sectional view of an AMR (anisotropic
magnetoresistive) element for detecting a recording magnetic field
from a recording medium, as viewed from the side opposite to the
recording medium.
[0059] The AMR element comprises a soft magnetic layer (SAL layer)
52, a nonmagnetic layer (SHUNT layer) 53, a magnetoresistive layer
(MR layer) 54, and a protective layer 55, which are deposited in
this order from below to form a laminate; and hard magnetic bias
layers 56 formed on both sides of the laminate. A NiFeNb alloy
film, a Ta film, a NiFe alloy film, and a CoPt alloy film are
generally used for the soft magnetic layer 52, the nonmagnetic
layer 53, the magnetoresistive layer 54 and the hard magnetic bias
layer 56, respectively.
[0060] In the AMR element shown in FIG. 4, conductor layers 58 are
respectively formed on the hard magnetic bias layers 56 through
under layers 57. Like the conductor layers of the spin-valve type
thin film elements shown in each of FIGS. 1 to 3, the conductor
layers 58 are formed so that the crystal face spacing in the
direction (the Z direction shown in the drawing) perpendicular to
the film plane is not less than the crystal face spacing of a bulk
material of a metallic material, which forms the conductor layers
58, in the direction perpendicular to the film plane thereof, and
the conductor layers 58 have the compression stress applied
thereto. Therefore, the conductor layers 58 are adhered to the
under layers, preventing separation of the conductor layers 58.
[0061] The conductor layers 58 are preferably made of a Cr film,
and the (110) face spacing in the direction perpendicular to the
film plane is preferably 2.039 angstroms or more.
[0062] In the present invention, as shown in FIG. 4, the under
layers 57 made of a .beta.-Ta film are preferably respectively
formed between the hard magnetic bias layers 56 and the conductor
layers 58. By forming the under layers 57 below the conductor
layers 58, it is possible to improve the orientation of the
conductor layers 58 and decrease the resistivity of the conductor
layers 58.
[0063] In the AMR element, the hard magnetic bias layers 56 are
magnetized in the X direction shown in FIG. 4 to apply a bias
magnetic field in the X direction to the magnetoresistive layer 54
from the hard magnetic bias layers 56. In addition, a bias magnetic
filed in the Y direction shown in the drawing is applied to the
magnetoresistive layer 54 from the soft magnetic layer 52. By
applying the bias magnetic fields in the X and Y directions to the
magnetoresistive layer 54, the magnetoresistive layer 54 is set to
a state in which magnetization linearly changes with changes in
magnetic field.
[0064] A sensing current from the conductor layers 58 is supplied
to the magnetoresistive layer 54. When the recording medium is
moved in the Z direction, and a leakage magnetic field in the Y
direction is supplied from the recording medium, the direction of
magnetization of the magnetoresistive layer 54 is changed to change
the resistance value, and the change in resistance is detected as a
change in voltage.
[0065] Description will be made of the method of manufacturing the
spin-valve type thin film elements respectively shown in FIGS. 1 to
3, and the AMR element shown in FIG. 4.
[0066] The films of the magnetoresistive element shown in each of
FIGS, 1 to 4 are deposited by sputtering or vapor deposition. As a
sputtering apparatus, an exciting apparatus may be used, and
particularly a DC magnetron sputtering apparatus is used in the
present invention. The DC magnetron sputtering apparatus can easily
form each of the layers of the magnetoresistive elements to a
predetermined thickness, and exhibits excellent thickness
reproducibility, as compared with other sputtering apparatus.
[0067] FIG. 5 is a drawing showing the configuration of the
internal structure of the DC magnetron sputtering apparatus used in
the present invention.
[0068] As shown in FIG. 5, a magnetron sputtering apparatus 60
comprises a chamber 61 in which an electrode unit 63 for mounting a
target 62, and a substrate support unit 64 opposite to the target
62 are provided. A substrate 65 is mounted on the substrate support
unit 64. Also, electrodes 66 are provided in the electrode unit 63.
Further, a gas inlet 67 and a gas discharge port 68 are provided in
the change 61 so that an Ar gas is introduced through the gas inlet
67.
[0069] As described above, in some cases, an .alpha.-Ta film is
used for the conductor layers of a magnetoresistive element. In
this case, it is necessary to introduce an Ar gas as well as O
(oxygen) in an amount appropriately adjusted through the gas inlet
67. On the other hand, the present invention uses the same Ta for
the under layers interposed between the conductor layers and the
hard magnetic bias layers, but uses a .beta.-Ta film.
Therefore,-only an Ar gas is introduced through the gas inlet 67,
thereby realizing simplification of the manufacturing process.
[0070] As shown in FIG. 5, a DC power source 69 is connected to the
electrode unit 63 so that when the DC power source 69 is operated,
magnetron discharge is produced due to interaction between an
electric field and a magnetic field. As a result, the target 62 is
sputtered to deposit a laminate 71 on the substrate 65 arranged
opposite to the target 62.
[0071] In the present invention, a DC power source 70 is also
connected to the substrate side. In deposition of conductor layers
of the laminate 71 on the substrate 65, the DC power source 70 on
the substrate side is operated to scratch the surface of the
deposited conductor layer by reverse sputtering. The reverse
sputtering causes crystal interstitial strain in the conductor
layers, increasing the crystal face spacing in the direction
perpendicular to the film plane.
[0072] In the present invention, it is found from experiment that
the crystal face spacing of the conductor layers can be increased
by intensifying the DC bias supplied to the substrate side from the
DC power source 70. Therefore, the strength of the DC bias must be
adjusted so that the crystal face spacing of the conductor layers
in the direction perpendicular to the film plane thereof is larger
than the crystal face spacing of a bulk material in the direction
perpendicular to the film plane thereof.
[0073] After the films of the magnetoresistive element shown in
each of FIGS. 1 to 4 are deposited, the side opposite to the
recording medium is scratched by dry etching to expose the layers
of the magnetoresistive element. In the present invention, since
the conductor layers are made of, for example, a Cr film, there is
no possibility of causing "sagging" in the Cr film when the
conductor layers are exposed to the outside, thereby preventing the
occurrence of a recess.
[0074] As described above, in the present invention, the conductor
layers are formed on the hard magnetic bias layers so that the
crystal face spacing in the direction perpendicular to the film
plane is larger than the crystal face spacing of a bulk material in
the direction perpendicular to the film plane thereof, thereby
applying compression stress to the conductor layers. It is thus
prevent separation of the conductor layers, and form the conductor
layers to an appropriate thickness.
[0075] In the present invention, particularly, the under layers of
a .beta.-Ta film are preferably formed between the hard magnetic
bias layers and the conductor layers. By forming the under layers
below the conductor layers, it is possible to improve the
orientation of the conductor layers, and decrease the resistivity
of the conductor layers.
[0076] In order to adjust the crystal face spacing of the conductor
layers, the DC power source is also connected to the substrate side
in the existing DC magnetron sputtering apparatus so that the
crystal face spacing of the conductor layers can easily be
increased by supplying a DC bias to the substrate side.
[0077] Although the thin film conductor layers of a
magnetoresistive element have been described with reference to the
embodiments of the present invention, the present invention can
also be applied to conductor layers of a semiconductor DRAM and the
like.
EXAMPLES
[0078] In the present invention, a Cr film was actually deposited
on a substrate in a DC magnetron sputtering apparatus to examine
the relation between the strength of the DC bias supplied to the
substrate side and the stress applied to the Cr film, and the
relation between the strength of the DC bias and the (110) face
spacing of the Cr film.
[0079] Before the Cr film was deposited on the substrate, an under
layer made of a .beta.-Ta film was deposited.
[0080] The relation between the strength of the DC bias supplied to
the substrate side and the stress applied to a conductor layer (Cr
film) is described with reference to FIG. 6. In FIG. 6, "stress"
shown on the ordinate represents the stress applied in parallel
with the film plane of the conductor layer.
[0081] FIG. 6 shows that the stress applied to the conductor layer
changes from a plus value to a minus value as the DC bias
increases. The stress on the plus side means that tensile stress is
applied to the conductor layer, and stress on the minus side means
that compression stress is applied to the conductor layer. It is
thus found that compression stress can be applied to the conductor
layer by increasing the Dc bias.
[0082] FIG. 7 is a graph showing the relation between the strength
of the DC bias supplied to the substrate side and the (110) face
spacing of the Cr film. The Cr film has a bcc crystal structure,
and the (110) crystal face is perpendicular to the film plane
thereof.
[0083] FIG. 7 indicates that the (110) face spacing of the Cr film
can be gradually increased by increasing the Dc bias. It is found
that the (110) face spacing of a bulk material of Cr is 2.039
angstroms.
[0084] It is thus found that in order to make the (110) face
spacing of the Cr film larger than the (110) face spacing (=2.039
angstroms) of a bulk material, a DC bias of about 280 (V) or more
is preferably supplied.
[0085] A graph was formed on the basis of FIGS. 6 and 7, in which
the (110) face spacing of the Cr film was shown on the abscissa,
and film stress was shown on the ordinate. The results are shown in
FIG. 8.
[0086] FIG. 8 indicates that the film stress applied to the Cr film
changes from plus to minus, i.e., from tensile stress to
compression stress, as the (110) face spacing of the Cr film
increases.
[0087] As described above, in the case of the bulk material, the
(110) face spacing is 2.039 angstroms. However, as shown in FIG. 8,
the film stress can be made zero (Gpa) when the (110) face spacing
of the Cr film is 2.039 angstroms, and compression stress can be
applied to the Cr film when the (110) face spacing is 2.039
angstroms or more.
[0088] In the present invention, therefore, the crystal face
spacing of a metallic material, which constitutes the conductor
layers, in the direction perpendicular to the film plane thereof is
not less than the crystal face spacing of a bulk material in the
direction perpendicular to the film plane thereof. This permits
application of compression stress to the conductor layers, and
prevention of separation of the conductor layers.
[0089] As described above, in the present invention, the conductor
layers comprising thin films are formed by using a metallic
material so that the crystal face spacing in the direction
perpendicular to the film plane thereof is not less than the
crystal face spacing of a bulk material, to apply compression
stress to the conductor layers, thereby preventing separation of
the conductor layers. By applying compression stress to the
conductor layers, the conductor layers can easily be formed to a
predetermined thickness.
[0090] In the present invention, particularly, the conductor layers
preferably comprise Cr films. The Cr films have a bcc crystal
structure, and the (110) crystal face thereof is perpendicular to
the film plane. However, in the present invention, the (110) face
spacing is 2.039 angstroms or more so that compression stress is
applied to the Cr films, thereby preventing separation of the Cr
films. By forming the conductor layers comprising Cr films, it is
possible to prevent "sagging" and the occurrence of a recess. Also
the Cr films are inexpensive, as compared with Au films
conventionally used for conductor layers.
[0091] In the present invention, the under layers are preferably
formed below the conductor layers. By forming the under layers, it
is possible to improve the orientation of the conductor layers, and
decrease the resistivity of the conductor layers. In addition, the
under layers are preferably made of a .beta.-Ta film which has
excellent corrosion resistance. When an .alpha.-Ta film is used for
conductor layers, the step of appropriately adjusting the amount of
0 (oxygen) introduced into the sputtering apparatus is required.
However, the deposition of a .beta.-Ta film requires no oxygen, and
can thus simplify the process, as compared with conventional
manufacturing processes.
* * * * *