U.S. patent application number 15/888324 was filed with the patent office on 2018-06-07 for sensor and electronic device.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. The applicant listed for this patent is Kabushiki Kaisha Toshiba. Invention is credited to Shotaro BABA, Yoshihiko FUJI, Michiko HARA, Yoshihiro HIGASHI, Shiori KAJI, Kei MASUNISHI, Tomohiko NAGATA, Kazuaki OKAMOTO, Kenji OTSU, Akiko YUZAWA.
Application Number | 20180156683 15/888324 |
Document ID | / |
Family ID | 61620974 |
Filed Date | 2018-06-07 |
United States Patent
Application |
20180156683 |
Kind Code |
A1 |
OTSU; Kenji ; et
al. |
June 7, 2018 |
SENSOR AND ELECTRONIC DEVICE
Abstract
According to one embodiment, a sensor includes a film portion
and a first sensor portion. The film portion is deformable. The
first sensor portion is provided at the film portion. The first
sensor portion includes a first conductive layer, a second
conductive layer, a first magnetic layer, a second magnetic layer,
and a first intermediate layer. The second conductive layer is
provided between the first conductive layer and the film portion.
The first magnetic layer is provided between the first conductive
layer and the second conductive layer. The second magnetic layer is
provided between the first magnetic layer and the second conductive
layer. The first intermediate layer is provided between the first
magnetic layer and the second magnetic layer. A curvature of the
first conductive layer is different from a curvature of at least a
portion of the film portion.
Inventors: |
OTSU; Kenji; (Yokohama
Kanagawa, JP) ; HARA; Michiko; (Yokohama Kanagawa,
JP) ; FUJI; Yoshihiko; (Kawasaki Kanagawa, JP)
; MASUNISHI; Kei; (Kawasaki Kanagawa, JP) ;
YUZAWA; Akiko; (Kawasaki Kanagawa, JP) ; NAGATA;
Tomohiko; (Yokohama Kanagawa, JP) ; KAJI; Shiori;
(Kawasaki Kanagawa, JP) ; HIGASHI; Yoshihiro;
(Komatsu Ishikawa, JP) ; OKAMOTO; Kazuaki;
(Yokohama Kanagawa, JP) ; BABA; Shotaro; (Kawasaki
Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Toshiba |
Tokyo |
|
JP |
|
|
Assignee: |
Kabushiki Kaisha Toshiba
Tokyo
JP
|
Family ID: |
61620974 |
Appl. No.: |
15/888324 |
Filed: |
February 5, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15440484 |
Feb 23, 2017 |
|
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15888324 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01B 7/18 20130101; G01L
9/0051 20130101; G01L 1/2287 20130101; G01L 7/02 20130101 |
International
Class: |
G01L 7/02 20060101
G01L007/02; G01B 7/16 20060101 G01B007/16 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 21, 2016 |
JP |
2016-184183 |
Claims
1-15. (canceled)
16. A sensor, comprising: a film portion, the film portion being
deformable; a first sensor portion provided at the film portion,
the first sensor portion including a first conductive layer, a
second conductive layer provided between the first conductive layer
and the film portion, a first magnetic layer provided between the
first conductive layer and the second conductive layer, a second
magnetic layer provided between the first magnetic layer and the
second conductive layer, and a first intermediate layer provided
between the first magnetic layer and the second magnetic layer, the
first conductive layer having a first conductive layer surface, and
a second conductive layer surface positioned between the first
conductive layer surface and the film portion, the first conductive
layer surface being concave or convex, and a curvature of the first
conductive layer surface being different from a curvature of a
partial region of the film portion, the partial region overlapping
the first sensor portion in a direction from the second magnetic
layer toward the first magnetic layer.
17. A sensor, comprising: a film portion, the film portion being
deformable; and a first sensor portion provided at the film
portion, the first sensor portion including a first magnetic layer,
a second magnetic layer provided between the first magnetic layer
and the film portion, and a first intermediate layer provided
between the first magnetic layer and the second magnetic layer, the
first magnetic layer being concave or convex, a curvature of the
first magnetic layer being different from the curvature of a
partial region of the film portion, the partial region overlapping
the first sensor portion in a direction from the second magnetic
layer toward the first magnetic layer.
18. The sensor according to claim 17, wherein the film portion is
positioned between a first space and a second space, and the first
magnetic layer is curved in a first state in which an air pressure
of the first space is substantially the same as an air pressure of
the second space.
19. The sensor according to claim 17, wherein the curvature of the
first magnetic layer is higher than the curvature of the at least a
portion of the film portion.
20. A sensor, comprising: a film portion, the film portion being
deformable; an insulating film; and a first sensor portion provided
at the film portion, the first sensor portion including a first
magnetic layer provided between the insulating film and the film
portion, a second magnetic layer provided between the first
magnetic layer and the film portion, and a first intermediate layer
provided between the first magnetic layer and the second magnetic
layer, the insulating film being concave or convex, a curvature of
the insulating film being different from a curvature of a partial
region of the film portion, the partial region overlapping the
first sensor portion in a direction from the second magnetic layer
toward the first magnetic layer.
21. The sensor according to claim 20, wherein the film portion is
positioned between a first space and a second space, and the
insulating film is curved in a first state in which an air pressure
of the first space is substantially the same as an air pressure of
the second space.
22. The sensor according to claim 20, wherein the curvature of the
insulating film is higher than the curvature of the at least a
portion of the film portion.
23. The sensor according to claim 16, wherein the at least a
portion of the film portion includes a center of the film
portion.
24. The sensor according to claim 16, further comprising: a
substrate; and a cover, the first sensor portion and the film
portion being disposed between the substrate and the cover.
25. An electronic device, comprising: the sensor according to claim
16; and a housing.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2016-184183, filed on
Sep. 21, 2016; the entire contents of which are incorporated herein
by reference.
FIELD
[0002] Embodiments described herein relate generally to a sensor
and an electronic device.
BACKGROUND
[0003] There is a sensor such as a pressure sensor or the like that
converts pressure applied from the outside into an electrical
signal. It is desirable to increase the sensitivity of the
sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1A to FIG. 1C are schematic views illustrating a sensor
according to a first embodiment;
[0005] FIG. 2A and FIG. 2B are graphs illustrating the
characteristics of the sensor;
[0006] FIG. 3 is a schematic cross-sectional view illustrating a
portion of the sensor according to the first embodiment;
[0007] FIG. 4A and FIG. 4B are schematic views illustrating a
sensor according to the first embodiment;
[0008] FIG. 5 is a schematic view illustrating a sensor according
to the first embodiment;
[0009] FIG. 6A to FIG. 6E are schematic views illustrating a sensor
according to a second embodiment;
[0010] FIG. 7A and FIG. 7B are schematic cross-sectional views
illustrating a portion of the sensor according to the second
embodiment;
[0011] FIG. 8 is a graph illustrating the shape of the sensor
according to the embodiment;
[0012] FIG. 9 is a graph illustrating shapes of sensors;
[0013] FIG. 10A to FIG. 10C are graphs illustrating the shapes of
the sensors;
[0014] FIG. 11A to FIG. 11E are schematic views illustrating a
sensor according to the second embodiment;
[0015] FIG. 12A and FIG. 12B are schematic cross-sectional views
illustrating a portion of the sensor according to the second
embodiment;
[0016] FIG. 13A to FIG. 13E are schematic views illustrating a
sensor according to the second embodiment;
[0017] FIG. 14A to FIG. 14E are schematic views illustrating a
sensor according to the second embodiment;
[0018] FIG. 15A and FIG. 15B are schematic cross-sectional views
illustrating a sensor according to a third embodiment;
[0019] FIG. 16A and FIG. 16B are schematic cross-sectional views
illustrating a sensor according to a fourth embodiment;
[0020] FIG. 17 is a schematic perspective view illustrating a
portion of the sensor according to the embodiment;
[0021] FIG. 18 is a schematic perspective view illustrating a
portion of another sensor according to the embodiment;
[0022] FIG. 19 is a schematic perspective view illustrating a
portion of another sensor according to the embodiment;
[0023] FIG. 20 is a schematic perspective view illustrating a
portion of another sensor according to the embodiment;
[0024] FIG. 21 is a schematic perspective view illustrating a
portion of another sensor according to the embodiment;
[0025] FIG. 22 is a schematic perspective view illustrating a
portion of another sensor according to the embodiment;
[0026] FIG. 23 is a schematic perspective view illustrating a
portion of another sensor according to the embodiment;
[0027] FIG. 24 is a schematic view illustrating the electronic
device according to the fifth embodiment;
[0028] FIG. 25A and FIG. 25B are schematic cross-sectional views
illustrating the electronic device according to the fifth
embodiment;
[0029] FIG. 26A and FIG. 26B are schematic views illustrating
another electronic device according to the fifth embodiment;
and
[0030] FIG. 27 is a schematic view illustrating another electronic
device according to the fifth embodiment.
DETAILED DESCRIPTION
[0031] According to one embodiment, a sensor includes a film
portion and a first sensor portion. The film portion is deformable.
The first sensor portion is provided at the film portion. The first
sensor portion includes a first conductive layer, a second
conductive layer, a first magnetic layer, a second magnetic layer,
and a first intermediate layer. The second conductive layer is
provided between the first conductive layer and the film portion.
The first magnetic layer is provided between the first conductive
layer and the second conductive layer. The second magnetic layer is
provided between the first magnetic layer and the second conductive
layer. The first intermediate layer is provided between the first
magnetic layer and the second magnetic layer. A curvature of the
first conductive layer is different from a curvature of at least a
portion of the film portion.
[0032] According to one embodiment, a sensor includes a film
portion and a first sensor portion. The film portion is deformable.
The first sensor portion is provided at the film portion. The first
sensor portion includes a first magnetic layer, a second magnetic
layer, and a first intermediate layer. The second magnetic layer is
provided between the first magnetic layer and the film portion. The
first intermediate layer is provided between the first magnetic
layer and the second magnetic layer. A curvature of the first
magnetic layer is different from the curvature of at least a
portion of the film portion.
[0033] According to one embodiment, a sensor includes a film
portion, an insulating film and a first sensor portion. The film
portion is deformable. The first sensor portion is provided at the
film portion. The first sensor portion includes a first magnetic
layer, a second magnetic layer, and a first intermediate layer. The
first magnetic layer is provided between the insulating film and
the film portion. The second magnetic layer is provided between the
first magnetic layer and the film portion. The first intermediate
layer is provided between the first magnetic layer and the second
magnetic layer. A curvature of the insulating film is different
from a curvature of at least a portion of the film portion.
[0034] Various embodiments will be described hereinafter with
reference to the accompanying drawings.
[0035] The drawings are schematic or conceptual; and the
relationships between the thicknesses and widths of portions, the
proportions of sizes between portions, etc., are not necessarily
the same as the actual values thereof. Further, the dimensions
and/or the proportions may be illustrated differently between the
drawings, even for identical portions.
[0036] In the drawings and the specification of the application,
components similar to those described in regard to a drawing
thereinabove are marked with like reference numerals, and a
detailed description is omitted as appropriate.
[0037] FIG. 1A to FIG. 1C are schematic views illustrating a sensor
according to a first embodiment.
[0038] FIG. 1A illustrates a plan view of the sensor 110 according
to the embodiment. FIG. 1A corresponds to a plan view as viewed
along arrow AA of FIG. 1B. FIG. 1B is a schematic perspective view
illustrating a cross section along line A1-A2 shown in FIG. 1A.
FIG. 1C is a line A3-A4 cross-sectional view shown in FIG. 1B.
[0039] As shown in FIG. 1A and FIG. 1B, the sensor 110 includes a
film portion 71 and a sensor portion 50 (a first sensor portion
51). The sensor 110 is, for example, a pressure sensor.
[0040] The film portion 71 is deformable. For example, the film
portion 71 is a transducing thin film that is flexible. The film
portion 71 is supported by a support portion 70s. For example, a
recess 70h is formed in a portion of the substrate used to form the
film portion 71 and the support portion 70s. The thin portion of
the substrate is used to form the film portion 71. The thick
portion of the substrate is used to form the support portion 70s.
The support portion 70s is connected to the outer edge of the film
portion 71. The planar shape of the film portion 71 is, for
example, substantially a quadrilateral (including a rectangle,
etc.), a circle (including a flattened circle), etc. The deformable
film described above may have a free end. In the example, a portion
(an extension portion 71e) of an outer edge 71E of the film portion
71 is connected to the support portion 70s. An extension portion
70e includes a portion (a side) of the outer edge 71E of the film
portion 71 most proximal to the first sensor portion 51. For
example, the film portion 71 can flex in a direction (e.g., the
Z-axis direction) perpendicular to the film surface.
[0041] As shown in FIG. 1B, the film portion 71 has a first film
surface 71p and a second film surface 71q. The second film surface
71q is the surface on the side opposite to the first film surface
71p. The film portion 71 is positioned between a first space S1
contacting the first film surface 71p, and a second space S2
contacting the second film surface 71q. The film portion 71 deforms
when the pressure (the air pressure) from the first space S1 and
the pressure (the air pressure) from the second space S2 are
different. For example, the film portion 71 deforms due to pressure
from the outside due to a sound wave, an ultrasonic wave, etc.
[0042] The film that is used to form the film portion 71 includes a
portion that flexes due to the external pressure. The film portion
71 may include a portion on the outer side of the portion flexing
due to the external pressure. In the film portion 71, for example,
the portion flexing due to the external pressure and the portion on
the outer side of the portion flexing due to the external pressure
may be continuous. The film portion 71 is supported by the support
portion 70s and flexes due to the external pressure.
[0043] FIG. 1B illustrates the sensor 110 in a state (hereinbelow,
a first state) in which the air pressure of the first space S1 and
the air pressure of the second space S2 are substantially the same.
For example, in the first state, the pressure that is applied to
the first film surface 71p from the outside and the pressure that
is applied to the second film surface 71q from the outside are
substantially equal. In the first state, for example, deformation
due to the sensing object such as the sound wave, etc., does not
occur in the film portion 71. In the first state, for example, the
pressures of both the first space S1 and the second space S2 are
atmospheric pressure.
[0044] In the example, the film portion 71 in the first state is
substantially flat. In the embodiment, the film portion 71 in the
first state may have an upward convex shape. In the embodiment, the
film portion 71 in the first state may have a downward convex
shape.
[0045] For example, the first sensor portion 51 (the sensor portion
50) is a strain sensing element sensing the deformation of the film
portion 71. The first sensor portion 51 is provided at the film
portion 71. For example, the first sensor portion 51 is provided on
a portion of the film portion 71. The front and back (top and
bottom) of the surfaces are arbitrary. It is desirable for the
position where the sensor portion 50 is provided to be the position
where the amount of strain of the film portion 71 is large. It is
desirable for the position of the sensor portion 50 to be an outer
edge vicinity (a peripheral portion) of the film portion 71.
[0046] As shown in FIG. 1A, the sensor 110 may include a first lead
LL1, a second lead LL2, a first sensor electrode ELL a second
sensor electrode EL2, and a controller 60. The first sensor portion
51 is electrically connected to the controller 60 via the first
lead LL1, the second lead LL2, the first sensor electrode ELL and
the second sensor electrode EL2. The controller 60 can sense a
signal (an electrical resistance, etc.) from the first sensor
portion 51.
[0047] In the embodiment, the state of being electrically connected
includes not only the state in which the multiple conductors are in
direct contact, but also the case where the multiple conductors are
connected via another conductor. The state of being electrically
connected includes the case where the multiple conductors are
connected via an element having a function such as switching,
amplification, etc.
[0048] A direction on a shortest line connecting the support
portion 70s and the first sensor portion 51 is taken as a Y-axis
direction (a first direction). One direction perpendicular to the
Y-axis direction is taken as a Z-axis direction. The Z-axis
direction corresponds to the direction connecting the film portion
71 and the first sensor portion 51. A direction perpendicular to
the Y-axis direction and perpendicular to the Z-axis direction is
taken as an X-axis direction. For example, the extension portion
70e extends along the X-axis direction.
[0049] As shown in FIG. 1C, the first sensor portion 51 includes a
first magnetic layer 11, a second magnetic layer 12, a first
intermediate layer 11i, a first conductive layer 21, and a second
conductive layer 22.
[0050] The second conductive layer 22 is provided between the first
conductive layer 21 and the film portion 71. The first magnetic
layer 11 is provided between the first conductive layer 21 and the
second conductive layer 22. The second magnetic layer 12 is
provided between the first magnetic layer 11 and the second
conductive layer 22. The first intermediate layer 11i is provided
between the first magnetic layer 11 and the second magnetic layer
12. The first intermediate layer 11i is nonmagnetic.
[0051] For example, the first conductive layer 21 is electrically
connected to the first sensor electrode EL1 described above. The
second conductive layer 22 is electrically connected to the second
sensor electrode EL2 described above.
[0052] Strain is generated in the first sensor portion 51 when the
film portion 71 deforms. The magnetization of at least one of the
first magnetic layer 11 or the second magnetic layer 12 changes
according to the deformation of the film portion 71. Stress (e.g.,
tensile stress in the surface) is applied to the sensor portion 50
by the deformation of the film portion 71; and the angle between
the magnetization of the first magnetic layer 11 and the
magnetization of the second magnetic layer 12 changes according to
the deformation of the film portion 71. The electrical resistance
(the electrical resistance of the first sensor portion 51) between
the first magnetic layer 11 and the second magnetic layer 12
changes due to the change of this angle. For example, the
controller 60 senses the change of the electrical resistance
between the first sensor electrode EL1 and the second sensor
electrode EL2. The pressure that is applied to the film portion 71
can be sensed.
[0053] In the example, the first magnetic layer 11 is a free layer
(a free magnetic layer), and the second magnetic layer 12 is a
reference layer (a magnetization reference layer). For example, the
first magnetic layer 11 may be a reference layer; and the second
magnetic layer 12 may be a free layer. Both the first magnetic
layer 11 and the second magnetic layer 12 may be free layers. The
description relating to the first sensor portion 51 described above
is applicable also to the other sensor portions 50 (a second sensor
portion 52, etc.) described below.
[0054] As shown in FIG. 1C, the curvature of the first conductive
layer 21 is different from the curvature of at least a portion of
the film portion 71. For example, the curvature (the absolute value
of the curvature) of the first conductive layer 21 is higher than
the curvature (the absolute value of the curvature) of at least a
portion of the film portion 71. For example, the first conductive
layer 21 is curved (bent) in the first state (the initial state) in
which the external pressure is not applied to the first sensor
portion 51. The first conductive layer 21 has a first conductive
layer surface 31 and a second conductive layer surface 32. The
second conductive layer surface 32 is positioned between the first
conductive layer surface 31 and the film portion 71. In the
embodiment, the first conductive layer surface 31 is curved in the
first state. The curvature (the absolute value of the curvature) of
the first conductive layer 21 may be lower than the curvature (the
absolute value of the curvature) of at least a portion of the film
portion 71.
[0055] When the pressure (the strain) that is applied to the film
portion 71 is sensed by the first sensor portion 51, there are
cases where the sensitivity of the sensing is offset with respect
to the strain. For example, it was found that there are cases where
the sensitivity of the sensing is high when the strain is not 0,
and the sensitivity of the sensing is low when the strain is 0. For
example, it is considered that this is caused by strain generated
in the magnetic layers included in the first sensor portion 51 when
manufacturing the first sensor portion 51, etc.
[0056] In the embodiment, the first conductive layer 21 is curved
in the first state in which the external pressure is not applied to
the first sensor portion 51. For example, an initial strain bias is
applied to the magnetic layer of the first sensor portion 51. For
example, the initial strain bias acts to weaken the residual strain
of the magnetic layer. Highly-sensitive sensing is possible for the
external pressure in the desired range. According to the
embodiment, a sensor can be provided in which the sensitivity can
be increased.
[0057] For example, the first conductive layer 21 can be curved by
appropriately setting the relationship between the thickness of the
first conductive layer 21 and the thickness of the second
conductive layer 22. For example, in the case where these materials
are substantially the same, for example, the upper surface of the
first conductive layer 21 is curved by setting the thickness of the
first conductive layer 21 to be thinner than the thickness of the
second conductive layer 22. The curved state can be obtained also
by setting the material of the first conductive layer 21 to be
different from the material of the second conductive layer 22.
[0058] For example, there are cases where residual stress is
applied due to the difference between the thermal history of the
first conductive layer 21 and the thermal history of the second
conductive layer 22. For example, the states of the conductive
layers are controlled to weaken such residual stress. The
appropriate initial strain bias is introduced to the magnetic
layer.
[0059] On the other hand, for example, a method may be considered
in which the initial strain of the magnetic layer is adjusted by
causing the film portion 71 to deform in the initial state.
Conversely, in the embodiment, the first sensor portion 51 is
caused to deform in the initial state. Therefore, compared to the
case where the film portion 71 is caused to deform, the strain of
the magnetic layer can be adjusted more directly and more
effectively. In the embodiment, the film portion 71 may be caused
to deform in the initial state in addition to causing the first
sensor portion 51 to deform (curve) in the initial state.
[0060] In FIG. 1B, the curve that is introduced to the first sensor
portion 51 (the first conductive layer 21) is upwardly convex. The
state of the upward convex curve is taken as a state of positive
initial strain bias. Conversely, a state of a downward convex curve
is taken as a state of negative initial strain bias.
[0061] In the embodiment, the polarity (the direction of the curve)
of the initial strain bias may be controlled based on the state of
the residual stress generated in the first sensor portion 51, the
state of the pressure that is to be sensed, etc.
[0062] The state of the curve introduced to the first sensor
portion 51 (the first conductive layer 21) can be sensed using
light (e.g., interferometry, etc.). A white-light interferometer
can be used to measure the state of the curve. A laser displacement
sensor may be used to measure the state of the curve. For example,
when performing the measurement using coherent light in the state
in which the sensor is disassembled, it is taken that the state
(the first state) in which the air pressure of the first space S1
and the air pressure of the second space S2 are substantially the
same is obtained when the space (the second space S2) on the upper
side of the film portion 71 and the space (the first space S1) on
the lower side of the film portion 71 both are atmospheric
pressure.
[0063] An example of the characteristics of the sensor portion will
now be described.
[0064] FIG. 2A and FIG. 2B are graphs illustrating the
characteristics of the sensor.
[0065] The horizontal axis shows a strain (per mille, 1/1000) of
the sensor portion 50 (the first sensor portion 51). The vertical
axis is an electrical resistance Rs (.OMEGA.) of the first sensor
portion 51. In the figures, the cases where a first material MT1
and a second material MT2 are used as the free layer of the first
sensor portion 51 are shown. The gauge factor of the first material
MT1 is 1500. The gauge factor of the second material MT2 is 4000.
In these samples, the front surface of the first sensor 51 (the
front surface of the first conductive layer 21) is substantially
flat in the state in which the external pressure is not
applied.
[0066] In the example, the change rate of the electrical resistance
Rs with respect to the strain is higher for the second material MT2
than for the first material MT1. In either of these materials, when
the strains is not 0 (e.g., in region R1 shown in FIG. 2A), a large
change of the electrical resistance Rs is obtained. In region R0
where the absolute value of the strain is small, the change of the
electrical resistance Rs is small; and the sensitivity is low.
[0067] Conversely, in the embodiment, the curvature of the first
conductive layer 21 is different from the curvature of the film
portion 71. For example, the first conductive layer 21 is curved in
the first state in which the external pressure is not applied to
the first sensor portion 51. An initial strain bias is applied to
the first sensor portion 51 in the state in which the external
pressure is not applied. For example, the first sensor portion 51
can be operated in an operation region (e.g., region R1 shown in
FIG. 2A) having high sensitivity. According to the embodiment, a
sensor can be provided in which the sensitivity can be
increased.
[0068] In the example shown in FIG. 2A and FIG. 2B, the .lamda.s
(the magnetostriction constant) of the free layer is positive. In
the example shown in FIG. 2A, the direction of the strain is
perpendicular to the orientation of the magnetization of the second
magnetic layer 12. In such a case, a positive initial strain bias
is applied to the first sensor portion 51. For example, the first
conductive layer 21 has an upward convex shape. For example, an
operation region that has high sensitivity such as region R1 can be
used. For example, the curvature (the reciprocal of the curvature
radius) of the first conductive layer surface 31 may be set
according to the magnetic material of the first magnetic layer 11,
etc. For example, in the case where the first magnetic layer 11
includes FeB, it is desirable for the initial strain bias to be
greater than 0 but not more than 0.35 (per mille). At this time,
the curvature (.rho.(mm.sup.-1)) of the first conductive layer
surface 31 is 0<.rho..ltoreq.2.0.
[0069] In the example shown in FIG. 2B, the direction of the strain
E is parallel to the orientation of the magnetization of the second
magnetic layer 12. In such a case, a negative initial strain bias
is applied to the first sensor portion 51. For example, the first
conductive layer 21 has a downward convex shape. Thereby, an
operation region that has high sensitivity can be used.
[0070] An example of the state in which the first conductive layer
21 (the first conductive layer surface 31) is curved is described
below.
[0071] FIG. 3 is a schematic cross-sectional view illustrating a
portion of the sensor according to the first embodiment.
[0072] The first conductive layer surface 31 includes first to
third points P1a to P3a. The third point P3a is positioned between
the first point P1a and the second point P2a on the first
conductive layer surface 31. The first to third points P1a to P3a
are positioned in the Y-Z plane. The Y-Z plane corresponds to a
plane including the first direction on the shortest line connecting
the support portion 70s and the first sensor portion 51 and a
second direction from the second magnetic layer 12 toward the first
magnetic layer 11. For example, the first point P1a and the second
point P2a are positioned at the ends of the first conductive layer
surface 31; and the third point P3a is positioned at the center of
the first conductive layer surface 31. A first straight line L1a
that connects the first point P1a and the third point P3a is tilted
with respect to a second straight line L2a connecting the second
point P2a and the third point P3a.
[0073] In the example, the first conductive layer 21 has an upward
convex shape in the first state. A third straight line L3a that
connects the first point P1a and the second point P2a is positioned
between the film portion 71 and the third point P3a. As described
below, the first conductive layer 21 may have a downward convex
shape in the first state. The first magnetic layer 11, the first
intermediate layer 11i, the second magnetic layer 12, and the
second conductive layer 22 may be curved similarly to the first
conductive layer 21. The curvature (.rho.) of the first conductive
layer surface 31 corresponds to the shape of the first conductive
layer surface 31 in a cross section parallel to the Z-Y plane.
[0074] As shown in FIG. 1C, the film portion 71 includes a film
portion region 71t where the first sensor portion 51 is provided.
For example, the film portion region 71t is the region of the
surface of the film portion 71 contacting the first sensor portion
51. For example, the curvature of the first conductive layer
surface 31 is different from the curvature of the film portion
region 71t. For example, the sign (positive or negative) of the
curvature of the film portion region 71t may be the same as the
sign of the curvature of the first conductive layer surface 31. For
example, the curvature (the absolute value of the curvature) of the
film portion region 71t is lower than the curvature (the absolute
value of the curvature) of the first conductive layer surface 31.
The curvature of the film portion region 71t may be zero. The sign
of the curvature of the film portion region 71t may be the reverse
of the sign of the curvature of the first conductive layer surface
31. The curvature (.rho.) of the film portion region 71t
corresponds to the shape of the film portion region 71t in a cross
section parallel to the Z-Y plane.
[0075] At least one of the first conductive layer 21 or the second
conductive layer 22 includes, for example, at least one selected
from the group consisting of Al (aluminum), Cu (copper), Ag
(silver), and Au (gold). At least one of the first magnetic layer
11 or the second magnetic layer 12 includes, for example, Fe
(iron), Co (cobalt), and Ni (nickel). The first intermediate layer
11i includes, for example, a metal, an insulator, or a
semiconductor. The intermediate layer 11i includes, for example,
MgO, etc. Examples of the materials, thicknesses, and the like of
these conductive layers, these magnetic layers, and the
intermediate layer 11i are described below.
[0076] The film portion 71 includes, for example, an insulator. The
film portion 71 may include, for example, a metal. The film portion
71 includes, for example, at least one of silicon oxide, silicon
nitride, or aluminum oxide. The thickness of the film portion 71
is, for example, not less than 200 nm and not more than 3 .mu.m.
Favorably, the thickness of the film portion 71 is, for example,
not less than 300 nm and not more than 1.5 .mu.m. The width (e.g.,
the length in a direction aligned with the X-Y plane) of the film
portion 71 is, for example, not less than 1 .mu.m and not more than
2000 .mu.m. More favorably, the width is not less than 60 .mu.m and
not more than 1500 .mu.m. In the case where the film portion 71 has
a rectangular shape, the length of one side of the film portion 71
is, for example, not less than 1 .mu.m and not more than 2000
.mu.m.
[0077] FIG. 4A and FIG. 4B are schematic views illustrating a
sensor according to the first embodiment.
[0078] The sensor 111 according to the embodiment shown in FIG. 4A
includes the multiple sensor portions 50. Otherwise, a description
similar to that of the sensor 110 is applicable to the sensor 111.
Similarly to FIG. 1B, FIG. 4A illustrates the cross section of the
sensor 111. The multiple sensor portions 50 include the first
sensor portion 51 and the second sensor portion 52. For example,
the multiple sensor portions 50 are arranged along the X-axis
direction.
[0079] FIG. 4B shows a cross section of the sensor 111 along line
A5-A6 shown in FIG. 4A. The second sensor portion 52 includes a
third magnetic layer 13, a fourth magnetic layer 14, a second
intermediate layer 12i, a third conductive layer 23, and a fourth
conductive layer 24.
[0080] The fourth conductive layer 24 is provided between the third
conductive layer 23 and the film portion 71. The third magnetic
layer 13 is provided between the third conductive layer 23 and the
fourth conductive layer 24. The fourth magnetic layer 14 is
provided between the third magnetic layer 13 and the fourth
conductive layer 24. The second intermediate layer 12i is provided
between the third magnetic layer 13 and the fourth magnetic layer
14. In the example, the third magnetic layer 13 is a free layer;
and the fourth magnetic layer 14 is a reference layer.
[0081] The third conductive layer 23 is curved in the first state
(the initial state) in which the external pressure is not applied
to the second sensor portion 52. The third conductive layer 23 has
a third conductive layer surface 33 and a fourth conductive layer
surface 34. The fourth conductive layer surface 34 is positioned
between the third conductive layer surface 33 and the film portion
71. The third conductive layer surface 33 is curved in the first
state.
[0082] The shape of the curve of the third conductive layer 23 (and
the third conductive layer surface 33) are similar to those of the
first conductive layer 21 (and the first conductive layer surface
31) described above. In the example, similarly to the description
relating to FIG. 3, the third conductive layer 23 (and the third
conductive layer surface 33) have upward convex shapes.
[0083] At least two of the multiple sensor portions 50 may be
connected in series. By providing the multiple sensor portions 50,
the sensitivity of the sensor 111 can be increased. The conductive
layers (the first conductive layer 21, the third conductive layer
23, etc.) are curved for each of the multiple sensor portions 50.
According to the sensor 111, the sensitivity can be increased
further.
[0084] FIG. 5 is a schematic view illustrating a sensor according
to the first embodiment.
[0085] Similarly to the sensor 111 described above, the sensor 112
according to the embodiment shown in FIG. 5 includes the multiple
sensor portions 50. In the sensor 112, for example, the multiple
sensor portions 50 are connected in series. One end of the multiple
sensor portions 50 is electrically connected to the first sensor
electrode EL1. One other end of the multiple sensor portions 50 is
electrically connected to the second sensor electrode EL2. By
connecting the multiple sensor portions 50 in series, the signal
from the multiple sensor portions 50 can be large. The sensing
object such as the pressure, etc., can be sensed with high
precision.
Second Embodiment
[0086] FIG. 6A to FIG. 6E are schematic views illustrating a sensor
according to a second embodiment.
[0087] FIG. 6A is a schematic plan view illustrating the sensor 113
according to the embodiment.
[0088] FIG. 6B is a schematic perspective view illustrating a cross
section of the sensor 113 along line B1-B2 shown in FIG. 6A.
[0089] FIG. 6C is a schematic cross-sectional view along line B1-B2
of the film portion 71.
[0090] FIG. 6D is a schematic cross-sectional view of the film
portion 71 and the sensor portion 50 (the first sensor portion 51)
along line B3-B4 shown in FIG. 6A.
[0091] FIG. 6A to FIG. 6D illustrate the sensor 113 in the first
state. In the embodiment as shown in these drawings, the film
portion 71 is not flat in the first state.
[0092] As shown in FIG. 6B to FIG. 6D, the film portion 71 has a
downward convex shape in the first state. For example, as shown in
FIG. 6C, a second film center 71r (the centroid) of the second film
surface 71q is positioned between a first film center 71s (the
centroid) of the first film surface 71p and a plane 75 including
the outer edge of the film portion 71.
[0093] FIG. 6E is a schematic view illustrating the magnetization
directions of the magnetic layers of the first sensor portion 51
and the direction of the strain generated in the first sensor
portion 51. In the example, the first magnetic layer 11 is a free
layer; and the second magnetic layer 12 is a reference layer. For
example, a second magnetization 12m of the second magnetic layer 12
is substantially fixed in a direction along the X-axis direction
(the third direction). For example, a first magnetization 11m of
the first magnetic layer 11 is aligned with the X-axis direction in
the first state. The first magnetization 11m is in the reverse
direction of the second magnetization 12m in the first state.
[0094] In the sensor 113, the magnetostriction constant (.lamda.s)
of the first magnetic layer 11 is positive. The magnetostriction
constant (.lamda.s) indicates the magnitude of the shape
deformation when the ferromagnetic layer has saturation
magnetization in some direction by applying an external magnetic
field. For a length L along some direction of the ferromagnetic
layer in the state in which there is no external magnetic field,
the magnetostriction constant .lamda.s is .DELTA.L/L, where the
length changes by .DELTA.L when the external magnetic field is
applied. Although the change amount changes with the magnitude of
the magnetic field, the magnetostriction constant .lamda.s is
.DELTA.L/L in the state in which a sufficient magnetic field is
applied and the magnetization is saturated. In the case where the
sign of the magnetostriction constant is positive, the direction in
which the tensile stress is applied is the easy magnetization axis.
In such a case, the magnetization of the first magnetic layer 11
(the free layer) rotates in the direction of the easy magnetization
axis. On the other hand, in the case where the magnetostriction
constant is negative, a direction perpendicular to the direction in
which the tensile stress is applied is the easy magnetization
axis.
[0095] As shown in FIG. 6E, stress (strain) in a direction D is
applied in the first sensor portion 51. The direction D is a
direction along the Y-axis direction. Strain is generated in a
direction perpendicular to the direction of the magnetization of
the reference layer. In such a case, a positive initial strain bias
is applied to the first sensor portion 51. In the example as shown
in FIG. 6D, the first sensor portion 51 (the first conductive layer
21) has an upward convex shape.
[0096] FIG. 7A and FIG. 7B are schematic cross-sectional views
illustrating a portion of the sensor according to the second
embodiment.
[0097] FIG. 7A shows a cross section of the sensor 113 along line
B5-B6 shown in FIG. 6B. FIG. 76 shows the enlarged first conductive
layer 21 shown in FIG. 7A. As shown in FIG. 7B, the first
conductive layer 21 and the first conductive layer surface 31 have
upward convex shapes.
[0098] As shown in FIG. 7B, the first conductive layer surface 31
includes first to third points P1b to P3b. The third point P3b is
positioned between the first point P1b and the second point P2b on
the first conductive layer surface 31. The first to third points
P1b to P3b are positioned in the Y-Z plane. For example, the first
point P1b and the second point P2b are positioned at the ends of
the first conductive layer surface 31; and the third point P3b is
positioned at the center of the first conductive layer surface 31.
A first straight line L1b that connects the first point P1b and the
third point P3b is tilted with respect to a second straight line
L2b connecting the second point P2b and the third point P3b. A
third straight line L3b that connects the first point P1b and the
second point P2b is positioned between the film portion 71 and the
third point P3b.
[0099] Thus, the first conductive layer 21 is curved. An
appropriate initial strain bias is applied to the magnetic layer of
the first sensor portion 51. The sensitivity of the first sensor
portion 51 can be high.
[0100] The film portion 71 is, for example, flat or downwardly
convex in the first state. In the embodiment, the film portion 71
is upwardly convex in the first state.
[0101] FIG. 8 is a graph illustrating the shape of the sensor
according to the embodiment.
[0102] FIG. 8 illustrates the shape of the sensor 113 shown in FIG.
6A to FIG. 6E in the first state. The vertical axis of FIG. 8
illustrates a position Zq (.mu.m) in the Z-axis direction of the
film portion 71 (e.g., the second film surface 71q) and the first
conductive layer 21 (e.g., the first conductive layer surface 31).
The vertical axis of FIG. 8 illustrates a position Yq (.mu.m) in
the Y-axis direction.
[0103] A range Ry1 and a range Ry2 shown in FIG. 8 correspond to
the shape of the first conductive layer 21. A range Ry3 shown in
FIG. 8 corresponds to the shape of the film portion 71. As shown in
FIG. 8, the curvature of the first conductive layer 21 (the first
conductive layer surface 31) is different from the curvature of at
least a portion of the film portion 71 (the second film surface
71q). For example, the curvature of the first conductive layer 21
is higher than the curvature of a center 71c of the film portion
71. The center 71c is the center of the film portion 71 in a
direction (e.g., the Y-axis direction) perpendicular to the Z-axis
direction.
[0104] The film portion 71 includes a region Rc including the
center 71c. The region Rc is a region extending along a fourth
direction connecting the first sensor portion 51 and the center 71c
of the film portion 71. The fourth direction is, for example, the
Y-axis direction. The length along the fourth direction of the
region Rc is, for example, not less than 0.5 times and not more
than 0.8 times the length along the fourth direction of the film
portion 71. For example, in a plane including the fourth direction
and the Z-axis direction, the curvature of the first conductive
layer 21 is higher than the curvature of the region Rc.
[0105] FIG. 9 is a graph illustrating shapes of sensors.
[0106] FIG. 9 illustrates the shape of the first conductive layer
surface 31 for sensors 121 to 124. In the sensors 121 to 124, the
concave or convex shape of the film portion 71 and the concave or
convex shape of the first conductive layer surface 31 are different
from each other. The planar size of the sensor portion is about 20
.mu.m.times.20 .mu.m.
[0107] The vertical axis of FIG. 9 illustrates a position Zp (nm)
of the first conductive layer surface 31 in the Z-axis direction.
The horizontal axis of FIG. 9 illustrates a position Yp (.mu.m) in
the Y-axis direction. The position Zp corresponds to the shape of
the film portion 71 in the range in which the value of the
horizontal axis is less than 120 .mu.m. The position Zp corresponds
to the shape of the first conductive layer surface 31 provided on
the first magnetic layer 11 in the range in which the value of the
horizontal axis is not less than 120 .mu.m and not more than 140
.mu.m. The position Zp corresponds to the support portion 70s in
the range in which the value of the horizontal axis exceeds 140
.mu.m.
[0108] FIG. 10A to FIG. 10C are graphs illustrating the shapes of
the sensors.
[0109] FIG. 10A illustrates the shape of the curve of the first
conductive layer surface 31 for the sensors 121 to 124 and sensors
125 to 127 described above. The vertical axis of FIG. 10A
illustrates a Z-direction displacement .DELTA.h (nm) of the first
conductive layer surface 31. The Z-direction displacement .DELTA.h
(nm) is obtained by rotating the shape of the first conductive
layer surface 31 illustrated by the position Zp (nm) shown in FIG.
9.
[0110] The horizontal axis of FIG. 10A illustrates the position Yp
(.mu.m) in the Y-axis direction.
[0111] FIG. 10B illustrates the curvature .rho. (mm.sup.-1) of the
first conductive layer surface 31 calculated from the data shown in
FIG. 10A.
[0112] FIG. 10C illustrates the values of the curvature .rho. shown
in FIG. 10B converted into an initial strain bias i (per mille)
applied to the first sensor portion 51.
[0113] In the sensor 121, the curvature .rho. is near zero; and the
initial strain bias i is near zero. In the sensor 124, the
curvature .rho. is about 3.7 (mm.sup.-1); and the initial strain
bias i is about 0.56 (per mille). In the sensor 125, the curvature
.rho. is about 2.4 (mm.sup.-1); and the initial strain bias i is
about 0.37 (per mille). In the sensor 126, the curvature .rho. is
about 1.67 (mm.sup.-1); and the initial strain bias i is about 0.25
(per mille). In the sensors 123 and 127, the curvature .rho. is
about 1.8 (mm.sup.-1); and the initial strain bias i is about 0.275
(per mille). In the sensor 122, the curvature .rho. is about 1.3
(mm.sup.-1); and the initial strain bias i is about 0.2 (per
mille). Thus, the initial strain bias i becomes large when the
curvature .rho. becomes large.
[0114] As illustrated in FIGS. 2A and 2B, there is an offset in the
characteristic of the change of the electrical resistance with
respect to the strain; and the initial strain bias is set according
to the offset. The range of the curvature of the first conductive
layer surface 31 is set according to the desired initial strain
bias.
[0115] In the embodiment, for example, the curvature (.rho.) of the
first conductive layer surface 31 is set to 0<.rho..ltoreq.2.0
(mm.sup.-1) in the case where the material of the first magnetic
layer 11 includes FeB. The curvature (.rho.) of the first
conductive layer surface 31 may be 0.1.ltoreq..rho..ltoreq.2.0
(mm.sup.-1). For example, the stress of multiple layers provided in
the sensor portion is adjusted according to the materials of the
multiple layers, the thicknesses of the multiple layers, etc.
Thereby, the degree (e.g., the curvature) of the curve can be
adjusted.
[0116] FIG. 11A to FIG. 11E are schematic views illustrating a
sensor according to the second embodiment.
[0117] FIG. 11A is a schematic plan view illustrating the sensor
114 according to the embodiment.
[0118] FIG. 11B is a schematic perspective view illustrating a
cross section of the sensor 114 along line C1-C2 shown in FIG.
11A.
[0119] FIG. 11C is a schematic cross-sectional view along line
C1-C2 of the film portion 71.
[0120] FIG. 11D is a schematic cross-sectional view of the film
portion 71 and the sensor portion 50 (the first sensor portion 51)
along line C3-C4 shown in FIG. 11A.
[0121] FIG. 11A to FIG. 11D illustrate the sensor 114 in the first
state.
[0122] As shown in FIG. 11B to FIG. 11D, the film portion 71 has an
upward convex shape in the first state. For example, as shown in
FIG. 11C, the first film center 71s of the first film surface 71p
is positioned between the second film center 71r of the second film
surface 71q and the plane 75 including the outer edge of the film
portion 71.
[0123] FIG. 11E is a schematic view illustrating the magnetization
directions of the magnetic layers of the first sensor portion 51
and the direction of the stress (the strain) applied to the first
sensor portion 51. In the example, the first magnetic layer 11 is a
free layer; and the second magnetic layer 12 is a reference layer.
For example, the second magnetization 12m of the second magnetic
layer 12 is fixed in a direction along the X-axis direction. For
example, the first magnetization 11m of the first magnetic layer 11
is aligned with the X-axis direction in the first state. In the
first state, the first magnetization 11m is in the reverse
direction of the second magnetization 12m. In the sensor 114, the
magnetostriction constant (.lamda.s) of the first magnetic layer 11
is negative.
[0124] As shown in FIG. 11E, the stress (the strain) is applied in
the direction D in the first sensor portion 51. The direction D is
a direction along the Y-axis direction. Strain in a direction
perpendicular to the direction of the magnetization of the
reference layer is generated in the first sensor portion 51. In
such a case, a negative initial strain bias is applied in the first
sensor portion 51. As shown in FIG. 11D, the first sensor portion
51 (the first conductive layer 21) has a downward convex shape.
[0125] FIG. 12A and FIG. 12B are schematic cross-sectional views
illustrating a portion of the sensor according to the second
embodiment.
[0126] FIG. 12A shows a cross section of the sensor 114 along line
C5-C6 shown in FIG. 11B. FIG. 12B shows the enlarged first
conductive layer 21 shown in FIG. 11A. As shown in FIG. 12B, the
first conductive layer 21 and the first conductive layer surface 31
have downward convex shapes.
[0127] As shown in FIG. 12B, the first conductive layer surface 31
includes first to third points P1c to P3c. The third point P3c is
positioned between the first point P1c and the second point P2c on
the first conductive layer surface 31. The first to third points
P1c to P3c are positioned in the Y-Z plane. For example, the first
point P1c and the second point P2c are positioned at the ends of
the first conductive layer surface 31; and the third point P3c is
positioned at the center of the first conductive layer surface 31.
A first straight line L1c that connects the first point P1c and the
third point P3c is tilted with respect to a second straight line
L2c connecting the second point P2c and the third point P3c. The
third point P3c is positioned between the film portion 71 and a
third straight line L3c connecting the first point P1c and the
second point P2c.
[0128] Thus, the first conductive layer 21 is curved. An
appropriate initial strain bias is applied to the first sensor
portion 51. The sensitivity of the first sensor portion 51 can be
high. In the sensor 114, the film portion 71 is flat or upwardly
convex in the first state. In the example, the film portion 71 may
be downwardly convex in the first state.
[0129] FIG. 13A to FIG. 13E are schematic views illustrating a
sensor according to the second embodiment.
[0130] FIG. 13A is a schematic plan view illustrating the sensor
115 according to the embodiment.
[0131] FIG. 13B is a schematic perspective view illustrating a
cross section of the sensor 115 along line D1-D2 shown in FIG.
13A.
[0132] FIG. 13C is a schematic cross-sectional view along line
D1-D2 of the film portion 71 and the sensor portion 50 (the first
sensor portion 51).
[0133] FIG. 13D is a schematic cross-sectional view of the film
portion 71 along line D3-D4 shown in FIG. 13A.
[0134] FIG. 13A to FIG. 13D illustrate the sensor 115 in the first
state. As shown in FIG. 13B to FIG. 13D, the film portion 71 has a
downward convex shape in the first state.
[0135] FIG. 13E is a schematic view illustrating the magnetization
directions of the magnetic layers of the first sensor portion 51
and the direction of the stress (the strain) applied to the first
sensor portion 51. In the example, the first magnetic layer 11 is a
free layer; and the second magnetic layer 12 is a reference layer.
For example, the second magnetization 12m of the second magnetic
layer 12 is fixed in a direction along the Y-axis direction. For
example, the first magnetization 11m of the first magnetic layer 11
is aligned with the Y-axis direction in the first state. The first
magnetization 11m is in the reverse direction of the second
magnetization 12m in the first state. In the sensor 115, the
magnetostriction constant (.lamda.s) of the first magnetic layer 11
is negative.
[0136] As shown in FIG. 11E, stress (strain) is applied in the
direction D in the first sensor portion 51. The direction D is a
direction along the Y-axis direction. Strain in a direction
parallel to the pinning direction of the reference layer is
generated in the first sensor portion 51. In such a case, a
positive initial strain bias is applied to the first sensor portion
51. In the example as shown in FIG. 13C, the first sensor portion
51 (the first conductive layer 21 and the first conductive layer
surface 31) has an upward convex shape.
[0137] An appropriate initial strain bias is applied to the first
sensor portion 51. The sensitivity of the first sensor portion 51
can be high. In the example, the film portion 71 is flat or
downwardly convex in the first state. In the example, the film
portion 71 may be upwardly convex in the first state.
[0138] FIG. 14A to FIG. 14E are schematic views illustrating a
sensor according to the second embodiment.
[0139] FIG. 14A is a schematic plan view illustrating the sensor
116 according to the embodiment.
[0140] FIG. 14B is a schematic perspective view illustrating a
cross section of the sensor 116 along line E1-E2 shown in FIG.
14A.
[0141] FIG. 14C is a schematic cross-sectional view along line
E1-E2 of the film portion 71 and the sensor portion 50 (the first
sensor portion 51).
[0142] FIG. 14D is a schematic cross-sectional view of the film
portion 71 along line E3-E4 shown in FIG. 14A.
[0143] FIG. 14A to FIG. 14D illustrate the sensor 116 in the first
state. As shown in FIG. 14B to FIG. 14D, the film portion 71 has an
upward convex shape in the first state.
[0144] FIG. 14E is a schematic view illustrating the magnetization
directions of the magnetic layers of the first sensor portion 51
and the direction of the stress (the strain) applied to the first
sensor portion 51. In the example, the first magnetic layer 11 is a
free layer; and the second magnetic layer 12 is a reference layer.
For example, the second magnetization 12m of the second magnetic
layer 12 is fixed in a direction along the Y-axis direction. For
example, the first magnetization 11m of the first magnetic layer 11
is aligned with the Y-axis direction in the first state. The first
magnetization 11m is in the reverse direction of the direction of
the second magnetization 12m in the first state. In the sensor 116,
the magnetostriction constant (.lamda.s) of the first magnetic
layer 11 is positive.
[0145] As shown in FIG. 14E, stress (strain) in the direction D is
applied in the first sensor portion 51. The direction D is a
direction along the Y-axis direction. Strain in a direction
parallel to the pinning direction of the reference layer is
generated in the first sensor portion 51. In such a case, a
negative initial strain bias is applied to the first sensor portion
51. In the example as shown in FIG. 14C, the first sensor portion
51 (the first conductive layer 21 and the first conductive layer
surface 31) has a downward convex shape.
[0146] An appropriate initial strain bias is applied to the first
sensor portion 51. The sensitivity of the first sensor portion 51
can be high. In the example, the film portion 71 is flat or
upwardly convex in the first state. In the example, the film
portion 71 may be downwardly convex in the first state.
Third Embodiment
[0147] FIG. 15A and FIG. 15B are schematic cross-sectional views
illustrating a sensor according to a third embodiment.
[0148] The sensor 117 according to the embodiment includes a first
sensor portion 51a instead of the first sensor portion 51 described
above. FIG. 15A illustrates a portion of the support portion 70s, a
portion of the film portion 71, and the first sensor portion 51.
The first sensor portion 51a is provided on the film portion 71.
The first sensor portion 51a includes the first magnetic layer 11,
the second magnetic layer 12, and the first intermediate layer 11i.
The second magnetic layer 12 is provided between the first magnetic
layer 11 and the film portion 71.
[0149] In the first sensor portion 51a, the positions of the first
conductive layer 21 and the second conductive layer 22 are
different from those of the case of the first sensor 51. Otherwise,
a description similar to that of the first sensor portion 51 is
applicable to the first sensor portion 51a. In the example, the
first conductive layer 21 is connected to one region of the second
magnetic layer 12. The second conductive layer 22 is connected to
one other region of the second magnetic layer 12. The one other
region of the second magnetic layer 12 described above is arranged
with the one region of the second magnetic layer 12 described above
in a direction crossing the Z-axis direction. In the first sensor
portion 51a, the current flows along the layer surface of the
magnetic layer. The first sensor portion 51a is a CIP-type. In the
first sensor portion 51a, an insulating layer 211 is provided
between the second magnetic layer 12 and the film portion 71 and
between the first conductive layer 21 and the second conductive
layer 22.
[0150] Otherwise, a description similar to that of the sensor 110
described above is applicable to the sensor 117.
[0151] In the first sensor portion 51a, the first conductive layer
21 may be connected to one region of the first intermediate layer
11i; and the second conductive layer 22 may be connected to one
other region of the first intermediate layer 11i. The other region
of the first intermediate layer 11i described above is arranged
with the one region of the first intermediate layer 11i described
above in a direction crossing the Z-axis direction. In such a case
as well, the current flows along the layer surface of the magnetic
layer.
[0152] In the first sensor portion 51a, the first conductive layer
21 may be connected to one region of the first magnetic layer 11;
and the second conductive layer 22 may be connected to one other
region of the first magnetic layer 11. The other region of the
first magnetic layer 11 described above is arranged with the one
region of the first magnetic layer 11 described above in a
direction crossing the Z-axis direction. In such a case as well,
the current flows along the layer surface of the magnetic
layer.
[0153] As shown in FIG. 15A, the curvature of the first magnetic
layer 11 is different from the curvature of at least a portion of
the film portion 71. For example, the curvature (the absolute value
of the curvature) of the first magnetic layer 11 is higher than the
curvature (the absolute value of the curvature) of at least a
portion of the film portion 71. FIG. 15B shows the enlarged first
magnetic layer 11 shown in FIG. 15A. As shown in FIG. 15B, for
example, the first magnetic layer 11 is curved in the first state
(the initial state) in which the external pressure is not applied
to the first sensor portion 51a. The first magnetic layer 11 has a
first magnetic layer surface 41 and a second magnetic layer surface
42. The second magnetic layer surface 42 is positioned between the
first magnetic layer surface 41 and the film portion 71. For
example, the first magnetic layer surface 41 is curved in the first
state. The curvature (the absolute value of the curvature) of the
first magnetic layer 11 may be lower than the curvature (the
absolute value of the curvature) of at least a portion of the film
portion 71.
[0154] The first magnetic layer surface 41 includes first to third
points P1d to P3d. The third point P3d is positioned between the
first point P1d and the second point P2d on the first magnetic
layer surface 41. The first to third points P1d to P3d are
positioned in the Y-Z plane. For example, the first point P1d and
the second point P2d are positioned at the ends of the first
magnetic layer surface 41; and the third point P3d is positioned at
the center of the first magnetic layer surface 41. A first straight
line L1d that connects the first point P1d and the third point P3d
is tilted with respect to a second straight line L2d connecting the
second point P2d and the third point P3d.
[0155] In the example, the first magnetic layer 11 has an upward
convex shape in the first state. A third straight line L3d that
connects the first point P1d and the second point P2d is positioned
between the film portion 71 and the third point P3d.
[0156] In the example, the first magnetic layer 11 may have a
downward convex shape in the first state. The third point P3d may
be positioned between the film portion 71 and the third straight
line L3d connecting the first point P1d and the second point P2d.
The intermediate layer 11i and the second magnetic layer 12 may be
curved similarly to the first magnetic layer 11. It is desirable
for the curvature of the first magnetic layer surface 41 to be, for
example, greater than 0 (mm.sup.-1) and not more than 2.0
(mm.sup.-1), e.g., not less than 0.1 (mm.sup.-1) and not more than
2.0 (mm.sup.-1).
[0157] In the example shown in FIG. 15A, the film portion 71 is
flat in the first state. In the example, the film portion 71 may be
upwardly convex or downwardly convex in the first state.
[0158] As shown in FIG. 15A, the film portion 71 includes the film
portion region 71t where the first sensor portion 51a is provided.
For example, the film portion region 71t is the region of the
surface of the film portion 71 contacting the first sensor portion
51a. For example, the curvature of the first magnetic layer surface
41 is different from the curvature of the film portion region 71t.
For example, the sign (positive or negative) of the curvature of
the film portion region 71t may be the same as the sign of the
curvature of the first magnetic layer surface 41. For example, the
curvature (the absolute value of the curvature) of the film portion
region 71t is lower than the curvature (the absolute value of the
curvature) of the first magnetic layer surface 41. The curvature of
the film portion region 71t may be zero. The sign of the curvature
of the film portion region 71t may be the reverse of the sign of
the curvature of the first magnetic layer surface 41.
[0159] In the fourth embodiment as well, the first magnetic layer
11 is curved in the first state in which the external pressure is
not applied to the first sensor portion 51a. An initial strain bias
is applied to the first sensor portion 51a. The first sensor
portion 51a can be operated in an operation region having high
sensitivity for the external pressure. According to the embodiment,
a sensor can be provided in which the sensitivity can be
increased.
Fourth Embodiment
[0160] FIG. 16A and FIG. 16B are schematic cross-sectional views
illustrating a sensor according to a fourth embodiment.
[0161] The sensor 118 according to the embodiment includes an
insulating film 65. Otherwise, a description similar to that of the
sensor 110 described above is applicable to the sensor 118.
[0162] As shown in FIG. 16A, the first magnetic layer 11 is
provided between the film portion 71 and at least a portion of the
insulating film 65. For example, the first magnetic layer 11 is
provided between the film portion 71 and one region 65a of the
insulating film 65. For example, one other region 65b of the
insulating film 65 contacts the film portion 71. For example, the
insulating film 65 is a passivation film covering the first sensor
portion 51. The insulating film 65 includes, for example, silicon
oxide (SiO.sub.2).
[0163] The insulating film 65 has a first insulating film surface
61 and a second insulating film surface 62. The second insulating
film surface 62 is positioned between the first insulating film
surface 61 and the first magnetic layer 11. The insulating film 65
contacts the upper surface (e.g., the first conductive layer
surface 31 or the first magnetic layer surface 41) of the first
sensor portion 51 at the second insulating film surface 62. The
first insulating film surface 61 is a region of the front surface
of the insulating film 65 distal to the second insulating film
surface 62 in the Z-axis direction.
[0164] A thickness t65 (the length along the Z-axis direction) of
the region 65a of the insulating film 65 is, for example, not less
than 5 nm and not more than 200 nm. The thickness t65 may be 100 nm
or less.
[0165] As shown in FIG. 16A, the curvature of the insulating film
65 is different from the curvature of at least a portion of the
film portion 71. For example, the curvature (the absolute value of
the curvature) of the insulating film 65 is higher than the
curvature (the absolute value of the curvature) of at least a
portion of the film portion 71. FIG. 16B shows the enlarged
insulating film 65 shown in FIG. 16A. As shown in FIG. 16B, for
example, the first insulating film surface 61 is curved in the
first state in which the external pressure is not applied to the
first sensor portion 51. The curvature (the absolute value of the
curvature) of the insulating film 65 may be lower than the
curvature (the absolute value of the curvature) of at least a
portion of the film portion 71.
[0166] The first insulating film surface 61 includes first to third
points P1e to P3e. The third point P3e is positioned between the
first point P1e and the second point P2e on the first insulating
film surface 61. The first to third points P1e to. P3e are
positioned in the Y-Z plane. For example, the first point P1e and
the second point P2e are positioned at the ends of the first
insulating film surface 61; and the third point P3e is positioned
at the center of the first insulating film surface 61. A first
straight line L1e that connects the first point P1e and the third
point P3e is tilted with respect to a second straight line L2e
connecting the second point P2e and the third point P3e.
[0167] In the example, the first insulating film surface 61 has an
upward convex shape in the first state. A third straight line L3e
that connects the first point P1e and the second point P2e is
positioned between the film portion 71 and the third point P3e.
[0168] In the example, the first insulating film surface 61 may
have a downward convex shape in the first state. The third point
P3e may be positioned between the film portion 71 and the third
straight line L3e connecting the first point P1e and the second
point P2e. The first conductive layer 21, the first magnetic layer
11, the intermediate layer 11i, the second magnetic layer 12, and
the second conductive layer 22 may be curved similarly to the first
insulating film surface 61. It is desirable for the curvature of
the first insulating film surface 61 to be, for example, greater
than 0 (mm.sup.-1) and not more than 2.0 (mm.sup.-1), e.g., not
less than 0.1 (mm.sup.-1) and not more than 2.0 (mm.sup.-1).
[0169] In FIG. 16A, the film portion 71 is flat in the first state.
In the example, similarly to the case of the sensors 113 to 116,
the film portion 71 may be upwardly convex or downwardly convex in
the first state.
[0170] As shown in FIG. 16A, the film portion 71 includes the film
portion region 71t where the first sensor portion 51 is provided.
For example, the film portion region 71t is the region of the
surface of the film portion 71 contacting the first sensor portion
51. For example, the curvature of the first insulating film surface
61 is different from the curvature of the film portion region 71t.
For example, the sign (positive or negative) of the curvature of
the film portion region 71t may be the same as the sign of the
curvature of the first insulating film surface 61. For example, the
curvature (the absolute value of the curvature) of the film portion
region 71t is lower than the curvature (the absolute value of the
curvature) of the first insulating film surface 61. The curvature
of the film portion region 71t may be zero. The sign of the
curvature of the film portion region 71t may be the reverse of the
sign of the curvature of the first insulating film surface 61.
[0171] In the embodiment as described above, the first insulating
film surface 61 is curved in the first state in which the external
pressure is not applied to the first sensor portion 51. An initial
strain bias is applied to the first sensor portion 51. The first
sensor portion 51 can be operated in an operation region having
high sensitivity for the external pressure. According to the
embodiment, a sensor can be provided in which the sensitivity can
be increased.
[0172] Examples of the sensor portions included in the embodiments
will now be described. In the following description, the notation
"material A/material B" indicates a state in which a layer of
material B is provided on a layer of material A.
[0173] FIG. 17 is a schematic perspective view illustrating a
portion of the sensor according to the embodiment.
[0174] In a sensor portion 50A as shown in FIG. 17, a lower
electrode 204, a foundation layer 205, a pinning layer 206, a
second magnetization reference layer 207, a magnetic coupling layer
208, a first magnetization reference layer 209, an intermediate
layer 203, a free magnetic layer 210, a capping layer 211, and an
upper electrode 212 are arranged in this order. For example, the
sensor portion 50A is a bottom spin-valve type. The magnetization
reference layer is, for example, a fixed magnetic layer.
[0175] The foundation layer 205 includes, for example, a stacked
film of tantalum and ruthenium (Ta/Ru). The thickness (the length
in the Z-axis direction) of the Ta layer is, for example, 3
nanometers (nm). The thickness of the Ru layer is, for example, 2
nm. The pinning layer 206 includes, for example, an IrMn-layer
having a thickness of 7 nm. The second magnetization reference
layer 207 includes, for example, a Co.sub.75Fe.sub.25 layer having
a thickness of 2.5 nm. The magnetic coupling layer 208 includes,
for example, a Ru layer having a thickness of 0.9 nm. The first
magnetization reference layer 209 includes, for example, a
Co.sub.40Fe.sub.40B.sub.20 layer having a thickness of 3 nm. The
intermediate layer 203 includes, for example, a MgO layer having a
thickness of 1.6 nm. The free magnetic layer 210 includes, for
example, Co.sub.40Fe.sub.40B.sub.20 having a thickness of 4 nm. The
capping layer 211 includes, for example, Ta/Ru. The thickness of
the Ta layer is, for example, 1 nm. The thickness of the Ru layer
is, for example, 5 nm. The lower electrode 204 and the upper
electrode 212 include, for example, at least one of aluminum (Al),
an aluminum copper alloy (Al--Cu), copper (Cu), silver (Ag), or
gold (Au). By using such a material having a relatively small
electrical resistance as the lower electrode 204 and the upper
electrode 212, the current can be caused to flow efficiently in the
sensor portion 50A. The lower electrode 204 and the upper electrode
212 include nonmagnetic materials.
[0176] The lower electrode 204 and the upper electrode 212 may
include, for example, a foundation layer (not illustrated) for the
lower electrode 204 and the upper electrode 212, a capping layer
(not illustrated) for the lower electrode 204 and the upper
electrode 212, and a layer of at least one of Al, Al--Cu, Cu, Ag,
or Au provided between the foundation layer and the capping layer.
For example, the lower electrode 204 and the upper electrode 212
include tantalum (Ta)/copper (Cu)/tantalum (Ta), etc. For example,
by using Ta as the foundation layer of the lower electrode 204 and
the upper electrode 212, the adhesion between the substrate (e.g.,
a film) and the lower electrode 204 and between the substrate and
the upper electrode 212 improves. Titanium (Ti), titanium nitride
(TiN), etc., may be used as the foundation layer for the lower
electrode 204 and the upper electrode 212.
[0177] By using Ta as the capping layer of the lower electrode 204
and the upper electrode 212, the oxidization of the copper (Cu),
etc., under the capping layer is suppressed. Titanium (Ti),
titanium nitride (TiN), etc., may be used as the capping layer for
the lower electrode 204 and the upper electrode 212.
[0178] The foundation layer 205 includes, for example, a stacked
structure including a buffer layer (not illustrated) and a seed
layer (not illustrated). For example, the buffer layer relaxes the
roughness of the surfaces of the lower electrode 204, the film,
etc., and improves the crystallinity of the layers stacked on the
buffer layer. For example, at least one selected from the group
consisting of tantalum (Ta), titanium (Ti), vanadium (V), tungsten
(W), zirconium (Zr), hafnium (Hf), and chrome (Cr) is used as the
buffer layer. An alloy that includes at least one material selected
from these materials may be used as the buffer layer.
[0179] It is favorable for the thickness of the buffer layer of the
foundation layer 205 to be not less than 1 nm and not more than 10
nm. It is more favorable for the thickness of the buffer layer to
be not less than 1 nm and not more than 5 nm. In the case where the
thickness of the buffer layer is too thin, the buffering effect is
lost. In the case where the thickness of the buffer layer is too
thick, the thickness of the sensor portion 50A becomes excessively
thick. The seed layer is formed on the buffer layer; and, for
example, the seed layer has a buffering effect. In such a case, the
buffer layer may be omitted. The buffer layer includes, for
example, a Ta layer having a thickness of 3 nm.
[0180] The seed layer of the foundation layer 205 controls the
crystal orientation of the layers stacked on the seed layer. The
seed layer controls the crystal grain size of the layers stacked on
the seed layer. As the seed layer, a metal having a fcc structure
(face-centered cubic structure), a hcp structure (hexagonal
close-packed structure), a bcc structure (body-centered cubic
structure), or the like is used.
[0181] For example, the crystal orientation of the spin-valve film
on the seed layer can be set to the fcc (111) orientation by using,
as the seed layer of the foundation layer 205, ruthenium (Ru)
having a hcp structure, NiFe having a fcc structure, or Cu having a
fcc structure. The seed layer includes, for example, a Cu layer
having a thickness of 2 nm or a Ru layer having a thickness of 2
nm. To increase the crystal orientation of the layers formed on the
seed layer, it is favorable for the thickness of the seed layer to
be not less than 1 nm and not more than 5 nm. It is more favorable
for the thickness of the seed layer to be not less than 1 nm and
not more than 3 nm. Thereby, the function as a seed layer that
improves the crystal orientation is realized sufficiently.
[0182] On the other hand, for example, the seed layer may be
omitted in the case where it is unnecessary for the layers formed
on the seed layer to have a crystal orientation (e.g., in the case
where an amorphous free magnetic layer is formed, etc.). For
example, a Cu layer having a thickness of 2 nm is used as the seed
layer.
[0183] For example, the pinning layer 206 provides unidirectional
anisotropy to the second magnetization reference layer 207 (the
ferromagnetic layer) formed on the pinning layer 206 and fixes the
magnetization of the second magnetization reference layer 207. The
pinning layer 206 includes, for example, an antiferromagnetic
layer. The pinning layer 206 includes, for example, at least one
selected from the group consisting of Ir--Mn, Pt--Mn, Pd--Pt--Mn,
Ru--Mn, Rh--Mn, Ru--Rh--Mn, Fe--Mn, Ni--Mn, Cr--Mn--Pt, and Ni--O.
An alloy may be used in which an added element is further added to
the at least one selected from the group consisting of Ir--Mn,
Pt--Mn, Pd--Pt--Mn, Ru--Mn, Rh--Mn, Ru--Rh--Mn, Fe--Mn, Ni--Mn,
Cr--Mn--Pt, and Ni--O. The thickness of the pinning layer 206 is
set appropriately. Thereby, for example, the unidirectional
anisotropy of the sufficient strength is provided.
[0184] For example, heat treatment is performed while applying a
magnetic field. Thereby, for example, the magnetization of the
ferromagnetic layer contacting the pinning layer 206 is fixed. The
magnetization of the ferromagnetic layer contacting the pinning
layer 206 is fixed in the direction of the magnetic field applied
in the heat treatment. For example, the heat treatment temperature
(the annealing temperature) is not less than the magnetization
pinning temperature of the antiferromagnetic material included in
the pinning layer 206. In the case where an antiferromagnetic layer
including Mn is used, there are cases where the MR ratio decreases
due to the Mn diffusing into layers other than the pinning layer
206. It is desirable for the heat treatment temperature to be set
to be not more than the temperature at which the diffusion of Mn
occurs. The heat treatment temperature is, for example, not less
than 200.degree. C. and not more than 500.degree. C. Favorably, the
heat treatment temperature is, for example, not less than
250.degree. C. and not more than 400.degree. C.
[0185] In the case where PtMn or PdPtMn is used as the pinning
layer 206, it is favorable for the thickness of the pinning layer
206 to be not less than 8 nm and not more than 20 nm. It is more
favorable for the thickness of the pinning layer 206 to be not less
than 10 nm and not more than 15 nm. In the case where IrMn is used
as the pinning layer 206, unidirectional anisotropy can be provided
using a thickness that is thinner than the case where PtMn is used
as the pinning layer 206. In such a case, it is favorable for the
thickness of the pinning layer 206 to be not less than 4 nm and not
more than 18 nm. It is more favorable for the thickness of the
pinning layer 206 to be not less than 5 nm and not more than 15 nm.
The pinning layer 206 includes, for example, an Ir.sub.22Mn.sub.78
layer having a thickness of 7 nm.
[0186] A hard magnetic layer may be used as the pinning layer 206.
For example, Co--Pt, Fe--Pt, Co--Pd, Fe--Pd, etc., may be used as
the hard magnetic layer. For example, the magnetic anisotropy and
the coercivity are relatively high for these materials. These
materials are hard magnetic materials. An alloy in which an added
element is further added to Co--Pt, Fe--Pt, Co--Pd, or Fe--Pd may
be used as the pinning layer 206. For example, CoPt (the proportion
of Co being not less than 50 at. % and not more than 85 at. %),
(Co.sub.xPt.sub.100x).sub.100-yCr.sub.y (x being not less than 50
at. % and not more than 85 at. %, and y being not less than 0 at. %
and not more than 40 at. %), FePt (the proportion of Pt being not
less than 40 at. % and not more than 60 at. %), etc., may be
used.
[0187] The second magnetization reference layer 207 includes, for
example, a Co.sub.xFe.sub.100-x alloy (x being not less than 0 at.
% and not more than 100 at. %) or a Ni.sub.xFe.sub.100-x alloy (x
being not less than 0 at. % and not more than 100 at. %). These
materials may include a material to which a nonmagnetic element is
added. For example, at least one selected from the group consisting
of Co, Fe, and Ni is used as the second magnetization reference
layer 207. An alloy that includes at least one material selected
from these materials may be used as the second magnetization
reference layer 207. Also, a
(Co.sub.xFe.sub.100-x).sub.100-yB.sub.y alloy (x being not less
than 0 at. % and not more than 100 at. %, and y being not less than
0 at. % and not more than 30 at. %) may be used as the second
magnetization reference layer 207. By using an amorphous alloy of
(Co.sub.xFe.sub.100-x).sub.100-yB.sub.y as the second magnetization
reference layer 207, the fluctuation of the characteristics of the
sensor portion 50A can be suppressed even in the case where the
sizes of the sensor portions are small.
[0188] For example, it is favorable for the thickness of the second
magnetization reference layer 207 to be not less than 1.5 nm and
not more than 5 nm. Thereby, for example, the strength of the
unidirectional anisotropic magnetic field due to the pinning layer
206 can be stronger. For example, the strength of the
antiferromagnetic coupling magnetic field between the second
magnetization reference layer 207 and the first magnetization
reference layer 209 via the magnetic coupling layer formed on the
second magnetization reference layer 207 can be stronger. For
example, it is favorable for the magnetic thickness (the product of
the saturation magnetization and the thickness) of the second
magnetization reference layer 207 to be substantially equal to the
magnetic thickness of the first magnetization reference layer
209.
[0189] The saturation magnetization of the thin film of
Co.sub.40Fe.sub.40B.sub.20 is about 1.9 T (teslas). For example, in
the case where a Co.sub.40Fe.sub.40B.sub.20 layer having a
thickness of 3 nm is used as the first magnetization reference
layer 209, the magnetic thickness of the first magnetization
reference layer 209 is 1.9 T.times.3 nm, i.e., 5.7 Tnm. On the
other hand, the saturation magnetization of Co.sub.75Fe.sub.25 is
about 2.1 T. The thickness of the second magnetization reference
layer 207 to obtain a magnetic thickness equal to that described
above is 5.7 Tnm/2.1 T, i.e., 2.7 nm. In such a case, it is
favorable for a Co.sub.75Fe.sub.25 layer having a thickness of
about 2.7 nm to be included in the second magnetization reference
layer 207. For example, a Co.sub.75Fe.sub.25 layer having a
thickness of 2.5 nm is used as the second magnetization reference
layer 207.
[0190] In the sensor portion 50A, a synthetic pinned structure made
of the second magnetization reference layer 207, the magnetic
coupling layer 208, and the first magnetization reference layer 209
is used. A single pinned structure made of one magnetization
reference layer may be used instead. In the case where the single
pinned structure is used, for example, a Co.sub.40Fe.sub.40B.sub.20
layer having a thickness of 3 nm is used as the magnetization
reference layer. The same material as the second magnetization
reference layer 207 described above may be used as the
ferromagnetic layer included in the magnetization reference layer
having the single pinned structure.
[0191] The magnetic coupling layer 208 causes antiferromagnetic
coupling to occur between the second magnetization reference layer
207 and the first magnetization reference layer 209. The magnetic
coupling layer 208 has a synthetic pinned structure. For example,
Ru is used as the material of the magnetic coupling layer 208. For
example, it is favorable for the thickness of the magnetic coupling
layer 208 to be not less than 0.8 nm and not more than 1 nm. A
material other than Ru may be used as the magnetic coupling layer
208 if the material causes sufficient antiferromagnetic coupling to
occur between the second magnetization reference layer 207 and the
first magnetization reference layer 209. For example, the thickness
of the magnetic coupling layer 208 is set to be a thickness not
less than 0.8 nm and not more than 1 nm corresponding to the second
peak (2nd peak) of RKKY (Ruderman-Kittel-Kasuya-Yosida) coupling.
Further, the thickness of the magnetic coupling layer 208 may be
set to be a thickness not less than 0.3 nm and not more than 0.6 nm
corresponding to the first peak (1st peak) of RKKY coupling. For
example, Ru having a thickness of 0.9 nm is used as the material of
the magnetic coupling layer 208. Thereby, highly reliable coupling
is obtained more stably.
[0192] The magnetic layer that is included in the first
magnetization reference layer 209 contributes directly to the MR
effect. For example, a Co--Fe--B alloy is used as the first
magnetization reference layer 209. Specifically, a
(Co.sub.xFe.sub.100-x).sub.100-yB.sub.y alloy (x being not less
than 0 at. % and not more than 100 at. %, and y being not less than
0 at. % and not more than 30 at. %) may be used as the first
magnetization reference layer 209. For example, the fluctuation
between the elements caused by crystal grains can be suppressed
even in the case where the size of the sensor portion 50A is small
by using a (Co.sub.xFe.sub.100-x).sub.100-yB.sub.y amorphous alloy
as the first magnetization reference layer 209.
[0193] The layer (e.g., a tunneling insulating layer (not
illustrated)) that is formed on the first magnetization reference
layer 209 may be planarized. The defect density of the tunneling
insulating layer can be reduced by planarizing the tunneling
insulating layer. Thereby, a higher MR ratio is obtained with a
lower resistance per area. For example, in the case where MgO is
used as the material of the tunneling insulating layer, the (100)
orientation of the MgO layer that is formed on the tunneling
insulating layer can be strengthened by using a
(Co.sub.xFe.sub.100-x).sub.100-yB.sub.y amorphous alloy as the
first magnetization reference layer 209. A higher MR ratio is
obtained by increasing the (100) orientation of the MgO layer. The
(Co.sub.xFe.sub.100-x).sub.100-yB.sub.y alloy crystallizes using
the (100) plane of the MgO layer as a template when annealing.
Therefore, good crystal conformation between the MgO and the
(Co.sub.xFe.sub.100-x).sub.100-yB.sub.y alloy is obtained. A higher
MR ratio is obtained by obtaining good crystal conformation.
[0194] Other than the Co--Fe--B alloy, for example, an Fe--Co alloy
may be used as the first magnetization reference layer 209.
[0195] A higher MR ratio is obtained as the thickness of the first
magnetization reference layer 209 increases. For example, a larger
fixed magnetic field is obtained as the thickness of the first
magnetization reference layer 209 decreases. A trade-off
relationship between the MR ratio and the fixed magnetic field
exists for the thickness of the first magnetization reference layer
209. In the case where the Co--Fe--B alloy is used as the first
magnetization reference layer 209, it is favorable for the
thickness of the first magnetization reference layer 209 to be not
less than 1.5 nm and not more than 5 nm. It is more favorable for
the thickness of the first magnetization reference layer 209 to be
not less than 2.0 nm and not more than 4 mm.
[0196] Other than the materials described above, the first
magnetization reference layer 209 may include a Co.sub.90Fe.sub.10
alloy having a fcc structure, Co having a hcp structure, or a Co
alloy having a hcp structure. For example, at least one selected
from the group consisting of Co, Fe, and Ni is used as the first
magnetization reference layer 209. An alloy that includes at least
one material selected from these materials may be used as the first
magnetization reference layer 209. For example, a higher MR ratio
is obtained by using an FeCo alloy material having a bcc structure,
a Co alloy having a cobalt composition of 50% or more, or a
material (a Ni alloy) having a Ni composition of 50% or more as the
first magnetization reference layer 209.
[0197] For example, a Heusler magnetic alloy layer such as
Co.sub.2MnGe, Co.sub.2FeGe, Co.sub.2MnSi, Co.sub.2FeSi,
Co.sub.2MnAl, Co.sub.2FeAl, Co.sub.2MnGa.sub.0.5Ge.sub.0.5,
Co.sub.2FeGa.sub.0.5Ge.sub.0.5, etc., also may be used as the first
magnetization reference layer 209. For example, a
Co.sub.40Fe.sub.40B.sub.20 layer having a thickness of 3 nm may be
used as the first magnetization reference layer 209.
[0198] For example, the intermediate layer 203 breaks the magnetic
coupling between the first magnetization reference layer 209 and
the free magnetic layer 210.
[0199] For example, the material of the intermediate layer 203
includes a metal, an insulator, or a semiconductor. For example,
Cu, Au, Ag, or the like is used as the metal. In the case where a
metal is used as the intermediate layer 203, the thickness of the
intermediate layer is, for example, not less than about 1 nm and
not more than about 7 nm. For example, magnesium oxide (MgO, etc.),
aluminum oxide (Al.sub.2O.sub.3, etc.), titanium oxide (TiO, etc.),
zinc oxide (ZnO, etc.), gallium oxide (Ga--O), or the like is used
as the insulator or the semiconductor. In the case where the
insulator or the semiconductor is used as the intermediate layer
203, the thickness of the intermediate layer 203 is, for example,
not less than about 0.6 nm and not more than about 2.5 nm. For
example, a CCP (Current-Confined-Path) spacer layer may be used as
the intermediate layer 203. In the case where a CCP spacer layer is
used as the spacer layer, for example, a structure is used in which
a copper (Cu) metal path is formed inside an insulating layer of
aluminum oxide (Al.sub.2O.sub.3). For example, a MgO layer having a
thickness of 1.6 nm is used as the intermediate layer.
[0200] The free magnetic layer 210 includes a ferromagnet material.
For example, the free magnetic layer 210 includes a ferromagnet
material including Fe, Co, and Ni. For example, an FeCo alloy, a
NiFe alloy, or the like is used as the material of the free
magnetic layer 210. The free magnetic layer 210 may include a
Co--Fe--B alloy, an Fe--Co--Si--B alloy, an Fe--Ga alloy having a
large .lamda. (magnetostriction constant), an Fe--Co--Ga alloy, a
Tb-M-Fe alloy, a Tb-M1-Fe-M2 alloy, an Fe-M3-M4-B alloy, Ni,
Fe--Al, ferrite, etc. For example, the X (magnetostriction
constant) is large for these materials. In the Tb-M-Fe alloy
described above, M is at least one selected from the group
consisting of Sm, Eu, Gd, Dy, Ho, and Er. In the Tb-M1-Fe-M2 alloy
described above, M1 is at least one selected from the group
consisting of Sm, Eu, Gd, Dy, Ho, and Er. M2 is at least one
selected from the group consisting of Ti, Cr, Mn, Co, Cu, Nb, Mo,
W, and Ta. In the Fe-M3-M4-B alloy described above, M3 is at least
one selected from the group consisting of Ti, Cr, Mn, Co, Cu, Nb,
Mo, W, and Ta. M4 is at least one selected from the group
consisting of Ce, Pr, Nd, Sm, Tb, Dy, and Er. Fe.sub.3O.sub.4,
(FeCo).sub.3O.sub.4, etc., are examples of the ferrite described
above. The thickness of the free magnetic layer 210 is, for
example, 2 nm or more.
[0201] The free magnetic layer 210 may include a magnetic material
including boron. The free magnetic layer 210 may include, for
example, an alloy including boron (B) and at least one element
selected from the group consisting of Fe, Co, and Ni. For example,
the free magnetic layer 210 includes a Co--Fe--B alloy or an Fe--B
alloy. For example, a Co.sub.40Fe.sub.40B.sub.20 alloy is used. Ga,
Al, Si, W, etc., may be added in the case where the free magnetic
layer 210 includes an alloy including boron (B) and at least one
element selected from the group consisting of Fe, Co, and Ni. For
example, high magnetostriction is promoted by adding these
elements. For example, an Fe--Ga--B alloy, an Fe--Co--Ga--B alloy,
or an Fe--Co--Si--B alloy may be used as the free magnetic layer
210. By using such a magnetic material containing boron, the
coercivity (Hc) of the free magnetic layer 210 is low; and the
change of the magnetization direction for the strain is easy.
Thereby, high sensitivity is obtained.
[0202] It is favorable for the boron concentration (e.g., the
composition ratio of boron) of the free magnetic layer 210 to be 5
at. % (the atomic percent) or more. Thereby, an amorphous structure
is obtained easily. It is favorable for the boron concentration of
the free magnetic layer to be 35 at. % or less. For example, the
magnetostriction constant decreases when the boron concentration is
too high. For example, it is favorable for the boron concentration
of the free magnetic layer to be not less than 5 at. % and not more
than 35 at. %; and it is more favorable to be not less than 10 at.
% and not more than 30 at. %.
[0203] In the case where a portion of the magnetic layer of the
free magnetic layer 210 includes Fe.sub.1-yB.sub.y
(0<y.ltoreq.0.3) or (Fe.sub.zX.sub.1-z).sub.1-yB.sub.y (X being
Co or Ni, 0.8.ltoreq.z<1, and 0<y.ltoreq.0.3), it becomes
easy to realize both a large magnetostriction constant .lamda. and
a low coercivity. Therefore, this is particularly favorable from
the perspective of obtaining a high gauge factor. For example,
Fe.sub.80B.sub.20 (4 nm) is used as the free magnetic layer 210.
Co.sub.40Fe.sub.40B.sub.20 (0.5 nm)/Fe.sub.80B.sub.20 (4 nm) may be
used as the free magnetic layer.
[0204] The free magnetic layer 210 may have a multilayered
structure. In the case where a tunneling insulating layer of MgO is
used as the intermediate layer 203, it is favorable to provide a
layer of a Co--Fe--B alloy at the portion of the free magnetic
layer 210 contacting the intermediate layer 203. Thereby, a high
magnetoresistance effect is obtained. In such a case, a layer of a
Co--Fe--B alloy is provided on the intermediate layer 203; and
another magnetic material that has a large magnetostriction
constant is provided on the layer of the Co--Fe--B alloy. In the
case where the free magnetic layer 210 has the multilayered
structure, for example, the free magnetic layer 210 may include
Co--Fe--B (2 nm)/Fe--Co--Si--B (4 nm), etc.
[0205] The free magnetic layer 210 may include an alloy including
Co.sub.xFe.sub.1-x (70 at %.ltoreq.x.ltoreq.80 at %) having a
crystal structure. The free magnetic layer 210 may have a
multilayered structure including an alloy layer including
Co.sub.xFe.sub.1-x (70 at %.ltoreq.x.ltoreq.80 at %) having a
crystal structure. The free magnetic layer 210 may include an alloy
including Ni.sub.yFe.sub.1-y (50 at %.ltoreq.x.ltoreq.75 at %)
having a crystal structure. The free magnetic layer 210 may have a
multilayered structure including an alloy layer including
Ni.sub.yFe.sub.1-y (50 at %.ltoreq.y.ltoreq.75 at %) having a
crystal structure.
[0206] The capping layer 211 protects the layers provided under the
capping layer 211. The capping layer 211 includes, for example,
multiple metal layers. The capping layer 211 includes, for example,
a two-layer structure (Ta/Ru) of a Ta layer and a Ru layer. The
thickness of the Ta layer is, for example, 1 nm; and the thickness
of the Ru layer is, for example, 5 nm. As the capping layer 211,
another metal layer may be provided instead of the Ta layer and/or
the Ru layer. The shape of the capping layer 211 is arbitrary. For
example, a nonmagnetic material is used as the capping layer 211.
Another material may be used as the capping layer 211 as long as
the material can protect the layers provided under the capping
layer 211.
[0207] In the case where the free magnetic layer 210 includes a
magnetic material containing boron, a diffusion suppression layer
(not illustrated) of an oxide material and/or a nitride material
may be provided between the free magnetic layer 210 and the capping
layer 211. Thereby, for example, the diffusion of boron is
suppressed. By using the diffusion suppression layer including an
oxide layer or a nitride layer, the diffusion of the boron included
in the free magnetic layer 210 can be suppressed; and the amorphous
structure of the free magnetic layer 210 can be maintained. As the
oxide material and/or the nitride material included in the
diffusion suppression layer, for example, an oxide material or a
nitride material including an element such as Mg, Al, Si, Ti, V,
Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W,
Sn, Cd, Ga, or the like is used. The diffusion suppression layer is
a layer that does not contribute to the magnetoresistance effect.
It is favorable for the resistance per area of the diffusion
suppression layer to be low. For example, it is favorable for the
resistance per area of the diffusion suppression layer to be set to
be lower than the resistance per area of the intermediate layer
that contributes to the magnetoresistance effect. From the
perspective of reducing the resistance per area of the diffusion
suppression layer, it is favorable for the diffusion suppression
layer to be an oxide or a nitride of Mg, Ti, V, Zn, Sn, Cd, or Ga.
The barrier height of these materials is low. It is favorable to
use an oxide having a strong chemical bond to suppress the
diffusion of the boron. For example, a MgO layer of 1.5 nm is used.
Oxynitrides are included in one of the oxide or the nitride.
[0208] In the case where the diffusion suppression layer includes
an oxide or a nitride, it is favorable for the thickness of the
diffusion suppression layer to be, for example, 0.5 nm or more.
Thereby, the diffusion suppression function of the boron is
realized sufficiently. It is favorable for the thickness of the
diffusion suppression layer to be 5 nm or less. Thereby, for
example, a low resistance per area is obtained. It is favorable for
the thickness of the diffusion suppression layer to be not less
than 0.5 nm and not more than 5 nm; and it is favorable to be not
less than 1 nm and not more than 3 nm. At least one selected from
the group consisting of magnesium (Mg), silicon (Si), and aluminum
(Al) may be used as the diffusion suppression layer. A material
that includes these light elements may be used as the diffusion
suppression layer. These light elements produce compounds by
bonding with boron. For example, at least one of a Mg--B compound,
an Al--B compound, or a Si--B compound is formed at the portion
including the interface between the diffusion suppression layer and
the free magnetic layer 210. These compounds suppress the diffusion
of boron.
[0209] Another metal layer, etc., may be inserted between the
diffusion suppression layer and the free magnetic layer 210. In the
case where the distance between the diffusion suppression layer and
the free magnetic layer 210 is too long, boron diffuses between the
diffusion suppression layer and the free magnetic layer 210; and
the boron concentration in the free magnetic layer 210 undesirably
decreases. Therefore, it is favorable for the distance between the
diffusion suppression layer and the free magnetic layer 210 to be
10 nm or less; and it is more favorable to be 3 nm or less.
[0210] FIG. 18 is a schematic perspective view illustrating a
portion of another sensor according to the embodiment.
[0211] As shown in FIG. 18, other than an insulating layer 213
being provided, a sensor portion 50AA is similar to the sensor
portion 50A. The insulating layer 213 is provided between the lower
electrode 204 and the upper electrode 212. The insulating layer 213
is arranged with the free magnetic layer 210 and the first
magnetization reference layer 209 in a direction crossing the
direction connecting the lower electrode 204 and the upper
electrode 212. The portions other than the insulating layer 213 are
similar to those of the sensor portion 50A; and a description is
therefore omitted.
[0212] The insulating layer 213 includes, for example, aluminum
oxide (e.g., Al.sub.2O.sub.3), silicon oxide (e.g., SiO.sub.2),
etc. The leakage current of the sensor portion 50AA is suppressed
by the insulating layer 213. The insulating layer 213 may be
provided in the sensor portions described below.
[0213] FIG. 19 is a schematic perspective view illustrating a
portion of another sensor according to the embodiment.
[0214] As shown in FIG. 19, a hard bias layer 214 is further
provided in a sensor portion 50AB. Otherwise, the sensor portion
50AB is similar to the sensor portion 50A. The hard bias layer 214
is provided between the lower electrode 204 and the upper electrode
212. The free magnetic layer 210 and the first magnetization
reference layer 209 are arranged between two portions of the hard
bias layer 214 in a direction crossing the direction connecting the
lower electrode 204 and the upper electrode 212. Otherwise, the
sensor portion 50AB is similar to the sensor portion 50AA.
[0215] The hard bias layer 214 sets the magnetization direction of
the free magnetic layer 210 by the magnetization of the hard bias
layer 214. The magnetization direction of the free magnetic layer
210 is set to the desired direction by the hard bias layer 214 in a
state in which pressure from the outside is not applied to the
film.
[0216] The hard bias layer 214 includes, for example, Co--Pt,
Fe--Pt, Co--Pd, Fe--Pd, etc. For example, the magnetic anisotropy
and the coercivity are relatively high for these materials. These
materials are, for example, hard magnetic materials. The hard bias
layer 214 may include, for example, an alloy in which an added
element is further added to Co--Pt, Fe--Pt, Co--Pd, or Fe--Pd. The
hard bias layer 214 may include, for example, CoPt (the proportion
of Co being not less than 50 at. % and not more than 85 at. %),
(Co.sub.xPt.sub.100-x).sub.100-yCr.sub.y (x being not less than 50
at. % and not more than 85 at. %, and y being not less than 0 at. %
and not more than 40 at. %), FePt (the proportion of Pt being not
less than 40 at. % and not more than 60 at. %), etc. In the case
where such a material is used, by applying an external magnetic
field that is larger than the coercivity of the hard bias layer
214, the direction of the magnetization of the hard bias layer 214
is set (fixed) in the direction in which the external magnetic
field is applied. The thickness of the hard bias layer 214 (e.g.,
the length along the direction from the lower electrode 204 toward
the upper electrode) is, for example, not less than 5 nm and not
more than 50 nm.
[0217] In the case where the insulating layer 213 is disposed
between the lower electrode 204 and the upper electrode 212,
SiO.sub.x or AlO.sub.x is used as the material of the insulating
layer 213. A not-illustrated foundation layer may be provided
between the insulating layer 213 and the hard bias layer 214. Cr,
Fe--Co, or the like is used as the material of the foundation layer
for the hard bias layer 214 in the case where the hard bias layer
214 includes a hard magnetic material such as Co--Pt, Fe--Pt,
Co--Pd, Fe--Pd, etc.
[0218] The hard bias layer 214 may have a structure of being
stacked with a not-illustrated pinning layer for the hard bias
layer. In such a case, the direction of the magnetization of the
hard bias layer 214 can be set (fixed) by the exchange coupling of
the hard bias layer 214 and the pinning layer for the hard bias
layer. In such a case, the hard bias layer 214 includes a
ferromagnetic material of at least one of Fe, Co, or Ni or an alloy
including at least one type of these elements. In such a case, the
hard bias layer 214 includes, for example, a Co.sub.xFe.sub.100-x
alloy (x being not less than 0 at. % and not more than 100 at. %),
a Ni.sub.xFe.sub.100-x alloy (x being not less than 0 at. % and not
more than 100 at. %), or a material in which a nonmagnetic element
is added to these alloys. A material that is similar to the first
magnetization reference layer 209 described above is used as the
hard bias layer 214. The pinning layer for the hard bias layer
includes a material similar to the pinning layer 206 inside the
sensor portion 50A described above. In the case where the pinning
layer for the hard bias layer is provided, a foundation layer
similar to the material included in the foundation layer 205 may be
provided under the pinning layer for the hard bias layer. The
pinning layer for the hard bias layer may be provided at a lower
portion or at an upper portion of the hard bias layer. In such a
case, the magnetization direction of the hard bias layer 214 is
determined by heat treatment in a magnetic field similarly to the
pinning layer 206.
[0219] The hard bias layer 214 and the insulating layer 213
described above are applicable also to any sensor portion according
to the embodiment. By using the stacked structure of the hard bias
layer 214 and the pinning layer for the hard bias layer, the
orientation of the magnetization of the hard bias layer 214 can be
maintained easily even when a large external magnetic field is
applied to the hard bias layer 214 for a short period of time.
[0220] FIG. 20 is a schematic perspective view illustrating a
portion of another sensor according to the embodiment.
[0221] In a sensor portion 50B as shown in FIG. 20, the lower
electrode 204, the foundation layer 205, the free magnetic layer
210, the intermediate layer 203, the first magnetization reference
layer 209, the magnetic coupling layer 208, the second
magnetization reference layer 207, the pinning layer 206, the
capping layer 211, and the upper electrode 212 are stacked in
order. The sensor portion 50B is, for example, a top spin-valve
type.
[0222] The foundation layer 205 includes, for example, a stacked
film of tantalum and copper (Ta/Cu). The thickness (the length in
the Z-axis direction) of the Ta layer is, for example, 3 nm. The
thickness of the Cu layer is, for example, 5 nm. The free magnetic
layer 210 includes, for example, Co.sub.40Fe.sub.40B.sub.20 having
a thickness of 4 nm. The intermediate layer 203 includes, for
example, a MgO layer having a thickness of 1.6 nm. The first
magnetization reference layer 209 includes, for example,
Co.sub.40Fe.sub.40B.sub.20/Fe.sub.50Co.sub.50. The thickness of the
Co.sub.40Fe.sub.40B.sub.20 layer is, for example, 2 nm. The
thickness of the Fe.sub.50Co.sub.50 layer is, for example, 1 nm.
The magnetic coupling layer 208 includes, for example, a Ru layer
having a thickness of 0.9 nm. The second magnetization reference
layer 207 includes, for example, a Co.sub.75Fe.sub.25 layer having
a thickness of 2.5 nm. The pinning layer 206 includes, for example,
an IrMn-layer having a thickness of 7 nm. The capping layer 211
includes, for example, Ta/Ru. The thickness of the Ta layer is, for
example, 1 nm. The thickness of the Ru layer is, for example, 5
nm.
[0223] The materials of the layers included in the sensor portion
50B may be the vertically-inverted materials of the layers included
in the sensor portion 50A. The diffusion suppression layer
described above may be provided between the foundation layer 205
and the free magnetic layer 210 of the sensor portion 50B.
[0224] FIG. 21 is a schematic perspective view illustrating a
portion of another sensor according to the embodiment.
[0225] In a sensor portion 50C as shown in FIG. 21, the lower
electrode 204, the foundation layer 205, the pinning layer 206, the
first magnetization reference layer 209, the intermediate layer
203, the free magnetic layer 210, the capping layer 211, and the
upper electrode 212 are stacked in this order. For example, the
sensor portion 50C has a single pinned structure that uses a single
magnetization reference layer.
[0226] The foundation layer 205 includes, for example, Ta/Ru. The
thickness (the length in the Z-axis direction) of the Ta layer is,
for example, 3 nm. The thickness of the Ru layer is, for example, 2
nm. The pinning layer 206 includes, for example, an IrMn-layer
having a thickness of 7 nm. The first magnetization reference layer
209 includes, for example, a Co.sub.40Fe.sub.40B.sub.20 layer
having a thickness of 3 nm. The intermediate layer 203 includes,
for example, a MgO layer having a thickness of 1.6 nm. The free
magnetic layer 210 includes, for example,
Co.sub.40Fe.sub.40B.sub.20 having a thickness of 4 nm. The capping
layer 211 includes, for example, Ta/Ru. The thickness of the Ta
layer is, for example, 1 nm. The thickness of the Ru layer is, for
example, 5 nm.
[0227] For example, materials similar to the materials of the
layers of the sensor portion 50A are used as the materials of the
layers of the sensor portion 50C.
[0228] FIG. 22 is a schematic perspective view illustrating a
portion of another sensor according to the embodiment.
[0229] In a sensor portion 50D as shown in FIG. 22, the lower
electrode 204, the foundation layer 205, a lower pinning layer 221,
a lower second magnetization reference layer 222, a lower magnetic
coupling layer 223, a lower first magnetization reference layer
224, a lower intermediate layer 225, a free magnetic layer 226, an
upper intermediate layer 227, an upper first magnetization
reference layer 228, an upper magnetic coupling layer 229, an upper
second magnetization reference layer 230, an upper pinning layer
231, the capping layer 211, and the upper electrode 212 are stacked
in order.
[0230] The foundation layer 205 includes, for example, Ta/Ru. The
thickness (the length in the Z-axis direction) of the Ta layer is,
for example, 3 nanometers (nm). The thickness of the Ru layer is,
for example, 2 nm. The lower pinning layer 221 includes, for
example, an IrMn-layer having a thickness of 7 nm. The lower second
magnetization reference layer 222 includes, for example, a
Co.sub.75Fe.sub.25 layer having a thickness of 2.5 nm. The lower
magnetic coupling layer 223 includes, for example, a Ru layer
having a thickness of 0.9 nm. The lower first magnetization
reference layer 224 includes, for example, a
Co.sub.40Fe.sub.40B.sub.20 layer having a thickness of 3 nm. The
lower intermediate layer 225 includes, for example, a MgO layer
having a thickness of 1.6 nm. The free magnetic layer 226 includes,
for example, Co.sub.40Fe.sub.40B.sub.20 having a thickness of 4 nm.
The upper intermediate layer 227 includes, for example, a MgO layer
having a thickness of 1.6 nm. The upper first magnetization
reference layer 228 includes, for example,
Co.sub.40Fe.sub.40B.sub.20/Fe.sub.50Co.sub.50. The thickness of the
Co.sub.40Fe.sub.40B.sub.20 layer is, for example, 2 nm. The
thickness of the Fe.sub.50Co.sub.50 layer is, for example, 1 nm.
The upper magnetic coupling layer 229 includes, for example, a Ru
layer having a thickness of 0.9 nm. The upper second magnetization
reference layer 230 includes, for example, a Co.sub.75Fe.sub.25
layer having a thickness of 2.5 nm. The upper pinning layer 231
includes, for example, an IrMn-layer having a thickness of 7 nm.
The capping layer 211 includes, for example, Ta/Ru. The thickness
of the Ta layer is, for example, 1 nm. The thickness of the Ru
layer is, for example, 5 nm.
[0231] For example, materials similar to the materials of the
layers of the sensor portion 50A are used as the materials of the
layers of the sensor portion 50D.
[0232] FIG. 23 is a schematic perspective view illustrating a
portion of another sensor according to the embodiment.
[0233] In a sensor portion 50E as shown in FIG. 23, the lower
electrode 204, the foundation layer 205, a first free magnetic
layer 241, the intermediate layer 203, a second free magnetic layer
242, the capping layer 211, and the upper electrode 212 are stacked
in this order.
[0234] The foundation layer 205 includes, for example, Ta/Cu. The
thickness (the length in the Z-axis direction) of the Ta layer is,
for example, 3 nm. The thickness of the Cu layer is, for example, 5
nm. The first free magnetic layer 241 includes, for example,
Co.sub.20Fe.sub.40B.sub.20 having a thickness of 4 nm. The
intermediate layer 203 includes, for example,
Co.sub.40Fe.sub.40B.sub.20 having a thickness of 4 nm. The capping
layer 211 includes, for example, Cu/Ta/Ru. The thickness of the Cu
layer is, for example, 5 nm. The thickness of the Ta layer is, for
example, 1 nm. The thickness of the Ru layer is, for example, 5
nm.
[0235] Materials similar to the materials of the layers of the
sensor portion 50A are used as the materials of the layers of the
sensor portion 50E. For example, materials similar to those of the
free magnetic layer 210 of the sensor portion 50A may be used as
the materials of the first free magnetic layer 241 and the second
free magnetic layer 242.
Fifth Embodiment
[0236] The embodiment relates to an electronic device. The
electronic device includes, for example, a sensor according to the
embodiments recited above or a sensor of a modification of the
embodiments. The electronic device includes, for example, an
information terminal. The information terminal includes a recorder,
etc. The electronic device includes a microphone, a blood pressure
sensor, a touch panel, etc.
[0237] FIG. 24 is a schematic view illustrating the electronic
device according to the fifth embodiment.
[0238] As shown in FIG. 24, an electronic device 750 according to
the embodiment is, for example, an information terminal 710. For
example, a microphone 610 is provided in the information terminal
710.
[0239] The microphone 610 includes, for example, a sensor 310. For
example, the film portion 71 is substantially parallel to the
surface of the information terminal 710 where a display unit 620 is
provided. The arrangement of the film portion 71 is arbitrary. Any
sensor described in reference to the first to third embodiments is
applicable to the sensor 310.
[0240] FIG. 25A and FIG. 25B are schematic cross-sectional views
illustrating the electronic device according to the fifth
embodiment.
[0241] As shown in FIG. 25A and FIG. 25B, the electronic device 750
(e.g., a microphone 370 (an acoustic microphone)) includes a
housing 360, a cover 362, and the sensor 310. The housing 360
includes, for example, a substrate 361 (e.g., the printed circuit
board) and the cover 362. The substrate 361 includes, for example,
a circuit such as an amplifier, etc.
[0242] An acoustic hole 325 is provided in the housing 360 (at
least one of the substrate 361 or the cover 362). In the example
shown in FIG. 25B, the acoustic hole 325 is provided in the cover
362. In the example shown in FIG. 25B, the acoustic hole 325 is
provided in the substrate 361. Sound 329 passes through the
acoustic hole 325 and enters the interior of the cover 362. The
microphone 370 responds to the sound pressure.
[0243] For example, the sensor 310 is disposed on the substrate
361; and electrical signal lines (not illustrated) are provided.
The cover 362 is provided to cover the sensor 310. The housing 360
is provided around the sensor 310. For example, the first sensor
portion 51 and the film portion 71 are disposed between the
substrate 361 and the cover 362. For example, the sensor 310 is
disposed between the substrate 361 and the cover 362.
[0244] FIG. 26A and FIG. 26B are schematic views illustrating
another electronic device according to the fifth embodiment.
[0245] In the example of these drawings, the electronic device 750
is a blood pressure sensor 330. FIG. 26A is a schematic plan view
illustrating skin on an arterial vessel of a human. FIG. 26B is a
line H1-H2 cross-sectional view of FIG. 26A.
[0246] The sensor 310 is used as a sensor in the blood pressure
sensor 330. The sensor 310 contacts the skin 333 on the arterial
vessel 331. Thereby, the blood pressure sensor 330 can continuously
perform blood pressure measurements.
[0247] FIG. 27 is a schematic view illustrating another electronic
device according to the fifth embodiment.
[0248] In the example of the drawing, the electronic device 750 is
a touch panel 340. In the touch panel 340, the sensors 310 are
provided in at least one of the interior of the display or the
exterior of the display.
[0249] For example, the touch panel 340 includes multiple first
leads 346, multiple second leads 347, the multiple sensors 310, and
a control circuit 341.
[0250] In the example, the multiple first leads 346 are arranged
along the Y-axis direction. Each of the multiple first leads 346
extends along the X-axis direction. The multiple second leads 347
are arranged along the X-axis direction. Each of the multiple
second leads 347 extends along the Y-axis direction.
[0251] The multiple sensors 310 are provided respectively at the
crossing portions between the multiple first leads 346 and the
multiple second leads 347. One sensor 310 is used as one sensing
component Es for sensing. The crossing portion includes the
position where the first lead 346 and the second lead 347 cross and
includes the region at the periphery of the position.
[0252] One end E1 of each of the multiple sensors 310 is connected
to one of the multiple first leads 346. One other end E2 of each of
the multiple sensors 310 is connected to one of the multiple second
leads 347.
[0253] The control circuit 341 is connected to the multiple first
leads 346 and the multiple second leads 347. For example, the
control circuit 341 includes a first interconnect circuit 346d that
is connected to the multiple first leads 346, a second interconnect
circuit 347d that is connected to the multiple second leads 347,
and a control signal circuit 345 that is connected to the first
interconnect circuit 346d and the second interconnect circuit
347d.
[0254] According to the fifth embodiment, an electronic device that
uses a sensor in which the sensitivity can be increased can be
provided.
[0255] The embodiments include, for example, the following
configurations.
(Configuration 1)
[0256] A sensor, comprising:
[0257] a film portion, the film portion being deformable;
[0258] a first sensor portion provided at the film portion, the
first sensor portion including [0259] a first conductive layer,
[0260] a second conductive layer provided between the first
conductive layer and the film portion, [0261] a first magnetic
layer provided between the first conductive layer and the second
conductive layer, [0262] a second magnetic layer provided between
the first magnetic layer and the second conductive layer, and
[0263] a first intermediate layer provided between the first
magnetic layer and the second magnetic layer,
[0264] a curvature of the first conductive layer being different
from a curvature of at least a portion of the film portion.
(Configuration 2)
[0265] The sensor according to configuration 1, wherein
[0266] the first conductive layer has a first conductive layer
surface, and a second conductive layer surface positioned between
the first conductive layer surface and the film portion, and
[0267] the first conductive layer surface is curved.
(Configuration 3)
[0268] The sensor according to configuration 2, further comprising
a support portion supporting the film portion,
[0269] the first conductive layer surface including a first point,
a second point, and a third point, the third point being positioned
between the first point and the second point on the first
conductive layer surface,
[0270] the first to third points being positioned in a plane
including a first direction and a second direction, the first
direction being on a shortest line connecting the support portion
and the first sensor portion, the second direction being from the
second magnetic layer toward the first magnetic layer,
[0271] a first straight line connecting the first point and the
third point being tilted with respect to a second straight line
connecting the second point and the third point.
(Configuration 4)
[0272] The sensor according to configuration 3, wherein
[0273] a magnetostriction constant of the first magnetic layer is
positive,
[0274] a direction of a magnetization of the second magnetic layer
is aligned with a third direction,
[0275] the third direction is perpendicular to the first direction
and perpendicular to the second direction, and
[0276] a straight line connecting the first point and the second
point is positioned between the third point and the film
portion.
(Configuration 5)
[0277] The sensor according to configuration 3, wherein
[0278] a magnetostriction constant of the first magnetic layer is
negative,
[0279] a direction of a magnetization of the second magnetic layer
is aligned with the third direction,
[0280] the third direction is perpendicular to the first direction
and perpendicular to the second direction, and
[0281] the third point is positioned between the film portion and a
straight line connecting the first point and the second point.
(Configuration 6)
[0282] The sensor according to configuration 3, wherein
[0283] a magnetostriction constant of the first magnetic layer is
negative,
[0284] a direction of a magnetization of the second magnetic layer
is aligned with the first direction, and
[0285] a straight line connecting the first point and the second
point is positioned between the third point and the film
portion.
(Configuration 7)
[0286] The sensor according to configuration 3, wherein a
magnetostriction constant of the first magnetic layer is
positive,
[0287] a direction of a magnetization of the second magnetic layer
is aligned with the first direction, and
[0288] the third point is positioned between the film portion and a
straight line connecting the first point and the second point.
(Configuration 8)
[0289] The sensor according to one of configurations 2 to 7,
wherein a curvature of the first conductive layer surface is not
less than 0.1 (mm.sup.-1) and not more than 2.0 (mm.sup.-1).
(Configuration 9)
[0290] The sensor according to configuration 8, wherein the first
magnetic layer includes at least one selected from a group
consisting of iron, cobalt and nickel, and boron.
(Configuration 10)
[0291] The sensor according to one of configurations 1 to 9,
wherein
[0292] the film portion is positioned between a first space and a
second space, and
[0293] the first conductive layer is curved in a first state in
which an air pressure of the first space is substantially the same
as an air pressure of the second space.
(Configuration 11)
[0294] The sensor according to one of configurations 1 to 10,
wherein the curvature of the first conductive layer is higher than
the curvature of the at least a portion of the film portion.
(Configuration 12)
[0295] A sensor, comprising:
[0296] a film portion, the film portion being deformable; and
[0297] a first sensor portion provided at the film portion, the
first sensor portion including [0298] a first magnetic layer,
[0299] a second magnetic layer provided between the first magnetic
layer and the film portion, and [0300] a first intermediate layer
provided between the first magnetic layer and the second magnetic
layer,
[0301] a curvature of the first magnetic layer being different from
the curvature of at least a portion of the film portion.
(Configuration 13)
[0302] The sensor according to configuration 12, wherein
[0303] the first magnetic layer has a first magnetic layer surface,
and a second magnetic layer surface positioned between the first
magnetic layer surface and the film portion, and
[0304] the first magnetic layer surface is curved.
(Configuration 14)
[0305] The sensor according to configuration 13, further comprising
a support portion supporting the film portion,
[0306] the first magnetic layer surface including a first point, a
second point, and a third point, the third point being positioned
between the first point and the second point on the first magnetic
layer surface,
[0307] the first to third points being positioned in a plane
including a first direction and a second direction, the first
direction being on a shortest line connecting the support portion
and the first sensor portion, the second direction being from the
second magnetic layer toward the first magnetic layer,
[0308] a first straight line connecting the first point and the
third point being tilted with respect to a second straight line
connecting the second point and the third point.
(Configuration 15)
[0309] The sensor according to configuration 13 or 14, wherein a
curvature of the first magnetic layer surface is not less than 0.1
(mm.sup.-1) and not more than 2.0 (mm.sup.-1).
(Configuration 16)
[0310] The sensor according to configuration 15, wherein the first
magnetic layer includes at least one selected from a group
consisting of iron, cobalt and nickel, and boron.
(Configuration 17)
[0311] The sensor according to one of configurations 12 to 16,
wherein
[0312] the film portion is positioned between a first space and a
second space, and
[0313] the first magnetic layer is curved in a first state in which
an air pressure of the first space is substantially the same as an
air pressure of the second space.
(Configuration 18)
[0314] The sensor according to one of configurations 12 to 17,
wherein the curvature of the first magnetic layer is higher than
the curvature of the at least a portion of the film portion.
(Configuration 19)
[0315] A sensor, comprising:
[0316] a film portion, the film portion being deformable;
[0317] an insulating film; and
[0318] a first sensor portion provided at the film portion, the
first sensor portion including [0319] a first magnetic layer
provided between the insulating film and the film portion, [0320] a
second magnetic layer provided between the first magnetic layer and
the film portion, and [0321] a first intermediate layer provided
between the first magnetic layer and the second magnetic layer,
[0322] a curvature of the insulating film being different from a
curvature of at least a portion of the film portion.
(Configuration 20)
[0323] The sensor according to configuration 19, wherein
[0324] the insulating film has a first insulating film surface, and
a second insulating film surface positioned between the first
insulating film surface and the film portion, and the first
insulating film surface is curved.
(Configuration 21)
[0325] The sensor according to configuration 20, further comprising
a support portion supporting the film portion,
[0326] the first insulating film surface including a first point, a
second point, and a third point, the third point being positioned
between the first point and the second point on the first
insulating film surface,
[0327] the first to third points being positioned in a plane
including a first direction and a second direction, the first
direction being on a shortest line connecting the support portion
and the first sensor portion, the second direction being from the
second magnetic layer toward the first magnetic layer,
[0328] a first straight line connecting the first point and the
third point being tilted with respect to a second straight line
connecting the second point and the third point.
(Configuration 22)
[0329] The sensor according to configuration 20 or 21, wherein a
curvature of the first magnetic layer surface is not less than 0.1
(mm.sup.-1) and not more than 2.0 (mm.sup.-1).
(Configuration 23)
[0330] The sensor according to one of configurations 19 to 22,
wherein
[0331] the film portion is positioned between a first space and a
second space, and
[0332] the insulating film is curved in a first state in which an
air pressure of the first space is substantially the same as an air
pressure of the second space.
(Configuration 24)
[0333] The sensor according to one of configurations 19 to 23,
wherein
[0334] the curvature of the insulating film is higher than the
curvature of the at least a portion of the film portion.
(Configuration 25)
[0335] The sensor according to one of configurations 1 to 24,
wherein the at least a portion of the film portion includes a
center of the film portion.
(Configuration 26)
[0336] The sensor according to configuration 25, wherein the at
least a portion of the film portion is a region along a fourth
direction connecting the first sensor portion and the center of the
film portion.
(Configuration 27)
[0337] The sensor according to configuration 26, wherein a length
along the fourth direction of the at least a portion of the film
portion is not less than 0.5 times a length along the fourth
direction of the film portion.
(Configuration 28)
[0338] The sensor according to one of configurations 1 to 27,
further comprising:
[0339] a substrate; and
[0340] a cover,
[0341] the first sensor portion and the film portion being disposed
between the substrate and the cover.
(Configuration 29)
[0342] An electronic device, comprising:
[0343] the sensor according to one of configurations 1 to 27;
and
[0344] a housing.
[0345] The "sensor" may be a "sensor device", for example. A
configuration including the "sensor device" and the controller can
be regarded as "sensor". The "sensor" may include at least one of
substrate and cover.
[0346] According to the embodiments, a sensor and an electronic
device can be provided in which the sensitivity can be
increased.
[0347] In the specification of the application, "perpendicular" and
"parallel" refer to not only strictly perpendicular and strictly
parallel but also include, for example, the fluctuation due to
manufacturing processes, etc. It is sufficient to be substantially
perpendicular and substantially parallel.
[0348] Hereinabove, embodiments of the invention are described with
reference to specific examples. However, the invention is not
limited to these specific examples. For example, one skilled in the
art may similarly practice the invention by appropriately selecting
specific configurations of components such as the film portion, the
sensor portion, the support portion, etc., from known art; and such
practice is within the scope of the invention to the extent that
similar effects can be obtained.
[0349] Further, any two or more components of the specific examples
may be combined within the extent of technical feasibility and are
included in the scope of the invention to the extent that the
purport of the invention is included.
[0350] Moreover, all sensors practicable by an appropriate design
modification by one skilled in the art based on the sensors
described above as embodiments of the invention also are within the
scope of the invention to the extent that the spirit of the
invention is included.
* * * * *