JP2017215326

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DESCRIPTION JP2017215326
Abstract: PROBLEM TO BE SOLVED: To provide a sensor and a microphone capable of improving
sensitivity. According to an embodiment, a sensor includes a printed circuit board, a cover, a
support portion provided between the printed circuit board and the cover, and the support
portion between the printed circuit board and the cover. A deformable substrate supported on
the substrate, and a sensing element provided on the substrate between the printed circuit board
and the cover. The sensing element includes a first magnetic layer, a second magnetic layer
including Fe1-yBy (0 <y ≦ 0.3), and an intermediate provided between the first magnetic layer
and the second magnetic layer. And layers. The electrical resistance of the sensing element
changes according to the deformation of the substrate. [Selected figure] Figure 1
センサ
[0001]
Embodiments of the present invention relate to sensors.
[0002]
Pressure sensors using MEMS (Micro Electro Mechanical Systems) technology include, for
example, a piezoresistive variable type and a capacitive type.
On the other hand, pressure sensors using spin technology have been proposed. In a pressure
sensor using spin technology, a change in resistance according to strain is detected. The
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sensitivity of the resistance change depending on the strain depends, for example, on the
material of the spin valve film. For example, in a strain sensing element used for a pressure
sensor using spin technology, improvement in sensitivity is desired.
[0003]
"D. Meyners et al.," Pressure sensor based on magnetic tunnel junctions ", J. Appl. Phys. 105, 07C
914 (2009)
[0004]
Embodiments of the present invention provide a sensor that can improve sensitivity.
[0005]
According to an embodiment, the sensor is supported by the support between the printed circuit
board, the cover, the support provided between the printed circuit board and the cover, and the
support between the printed circuit board and the cover. And a sensing element provided on the
substrate between the printed circuit board and the cover.
The sensing element includes a first magnetic layer, a second magnetic layer including Fe1-yBy
(0 <y ≦ 0.3), and an intermediate provided between the first magnetic layer and the second
magnetic layer. And layers. The electrical resistance of the sensing element changes according to
the deformation of the substrate.
[0006]
FIG. 1A to FIG. 1C are schematic views showing a strain sensing element according to the first
embodiment. FIG. 2A to FIG. 2C are schematic views showing the operation of the strain sensing
element according to the first embodiment. FIG. 3A to FIG. 3C are graphs showing examples of
experimental results of the strain sensing element according to the embodiment. FIG. 4A to FIG.
4C are graphs showing an example of another experimental result of the strain sensing element
according to the embodiment. FIG. 5A to FIG. 5C are graphs showing an example of another
experimental result of the strain sensing element according to the embodiment. FIG. 6A to FIG.
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6C are graphs showing an example of another experimental result of the strain sensing element
according to the embodiment. FIG. 7A to FIG. 7C are graphs showing an example of another
experimental result of the strain sensing element according to the embodiment. FIG. 8A to FIG.
8C are graphs showing an example of another experimental result of the strain sensing element
according to the embodiment. FIG. 9A to FIG. 9D are graphs showing an example of another
experimental result of the strain sensing element. It is a graph which shows the example of the
result of the distortion sensor characteristic of the distortion detection element which concerns
on embodiment. 11A and 11B are schematic views showing another strain sensing element
according to the first embodiment. 12 (a) and 12 (b) are schematic perspective views illustrating
the pressure sensor according to the second embodiment. FIG. 13A to FIG. 13E are schematic
cross-sectional views in order of processes illustrating the manufacturing direction of the
pressure sensor according to the embodiment. It is a schematic plan view which illustrates the
microphone concerning a 3rd embodiment. It is a schematic cross section which illustrates the
acoustic microphone concerning a 4th embodiment. FIG. 16A and FIG. 16B are schematic views
illustrating the blood pressure sensor according to the fifth embodiment. It is a schematic plan
view which illustrates the touch panel concerning a 6th embodiment.
[0007]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings. The drawings are schematic or conceptual, and the relationship between the thickness
and width of each part, the ratio of sizes between parts, and the like are not necessarily the same
as the actual ones. In addition, even in the case of representing the same portion, the dimensions
and ratios may be different from one another depending on the drawings. In the specification of
the present application and the drawings, the same elements as those described above with
reference to the drawings are denoted by the same reference numerals, and the detailed
description will be appropriately omitted.
[0008]
First Embodiment FIG. 1A to FIG. 1C are schematic views illustrating a strain sensing element
according to a first embodiment. FIG. 1A is a schematic perspective view of a strain sensing
element. FIG. 1B is a schematic cross-sectional view of the strain sensing element. FIG. 1C is a
schematic cross-sectional view illustrating a pressure sensor in which a strain sensing element is
used. In FIG. 1 (b), the first electrode and the second electrode are omitted for the convenience of
description.
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[0009]
As shown in FIG. 1A, the strain sensing element 100 according to the embodiment includes a first
magnetic layer 10, a second magnetic layer 20, and an intermediate layer 30. In this example, the
strain sensing element 100 further includes the nonmagnetic layer 40, the first electrode E1, and
the second electrode E2. The nonmagnetic layer 40 may not necessarily be provided.
[0010]
For example, the direction from the first magnetic layer 10 toward the second magnetic layer 20
is taken as the Z-axis direction (stacking direction). One direction perpendicular to the Z-axis
direction is taken as the X-axis direction. A direction perpendicular to the Z-axis direction and the
X-axis direction is taken as a Y-axis direction.
[0011]
In this example, the second electrode E2 is provided separately from the first electrode E1 in the
stacking direction. The first magnetic layer 10 is provided between the first electrode E1 and the
second electrode E2. An intermediate layer 30 is provided between the first magnetic layer 10
and the second electrode E2. The second magnetic layer 20 is provided between the intermediate
layer 30 and the second electrode E2. The nonmagnetic layer 40 is provided between the second
magnetic layer 20 and the second electrode E2.
[0012]
The first magnetic layer 10 and the second magnetic layer 20 may be interchanged with each
other with the intermediate layer 30 interposed therebetween. In that case, the nonmagnetic
layer 40 is provided between the second magnetic layer 20 and the first electrode E1.
[0013]
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The first magnetic layer 10 is, for example, a reference layer. A magnetization fixed layer or a
magnetization free layer is used as a reference layer. In the example shown in FIGS. 1A and 1B,
the first magnetic layer 10 is a magnetization fixed layer. For example, a synthetic pin structure
or a single pin structure is used for the first magnetic layer 10. In this example, a synthetic pin
structure is used for the first magnetic layer 10. As described later, the first magnetic layer 10
may be a magnetization free layer.
[0014]
In the example shown in FIGS. 1A and 1B, the first magnetic layer 10 includes a first
magnetization fixed layer 11, a second magnetization fixed layer 12, and a magnetic coupling
layer 13. The magnetic coupling layer 13 is provided between the first magnetization fixed layer
11 and the second magnetization fixed layer 12.
[0015]
In the second magnetization fixed layer 12, for example, a Cox Fe 100-x alloy (x is 0 at. % To 100
at. % Or less), Ni x Fe 100-x alloy (x is 0 at. % To 100 at. Or less, or materials obtained by adding
a nonmagnetic element thereto. As the second magnetization fixed layer 12, for example, at least
one selected from the group consisting of Co, Fe, and Ni is used. As the second magnetization
fixed layer 12, an alloy including at least one material selected from these materials may be used.
As the second magnetization fixed layer 12, (CoxFe100-x) 100-yBy alloy (x is 0 at. % To 100 at. %
Or less, y is 0 at. % To 30 at. % Or less) can also be used. When a single pin structure is used for
the first magnetic layer 10, the same material as the material of the second magnetization fixed
layer 12 described above may be used as the ferromagnetic layer used for the magnetization
fixed layer of the single pin structure.
[0016]
The magnetic coupling layer 13 causes antiferromagnetic coupling between the second
magnetization fixed layer 12 and the first magnetization fixed layer 11. For example, Ru is used
as the magnetic coupling layer 13. The material other than Ru may be used as the magnetic
coupling layer 13 as long as it is a material that causes sufficient antiferromagnetic coupling
between the first magnetization fixed layer 12 and the first magnetization fixed layer 11. For
example, Ru of 0.9 nm in thickness is used as the magnetic coupling layer 13. Thereby, a reliable
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connection can be obtained more stably.
[0017]
The magnetic layer used for the first magnetization fixed layer 11 directly contributes to the
magnetoresistive effect (MR effect). For example, a Co̶Fe̶B alloy is used as the first
magnetization fixed layer 11. Specifically, as the first magnetization fixed layer 11, (CoxFe100-x)
100-yBy alloy (x is 0 at. % To 100 at. % Or less, y is 0 at. % To 30 at. % Or less) can also be used.
As the first magnetization fixed layer 11, for example, an Fe-Co alloy may be used other than the
Co-Fe-B alloy.
[0018]
For the first magnetization fixed layer 11, in addition to the above-described materials, a
Co90Fe10 alloy of fcc structure, Co of hcp structure, or a Co alloy of hcp structure is used. As the
first magnetization fixed layer 11, for example, at least one selected from the group consisting of
Co, Fe and Ni is used. As the first magnetization fixed layer 11, an alloy containing at least one
material selected from these materials is used. For example, by using a FeCo alloy material of bcc
structure, a Co alloy containing 50% or more of cobalt composition, or a material of 50% or more
of Ni composition (Ni alloy) as the first magnetization fixed layer 11, for example, a larger MR
The rate of change is obtained.
[0019]
For example, a Heusler magnetic alloy layer such as Co2MnGe, Co2FeGe, Co2MnSi, Co2FeSi,
Co2MnAl, Co2FeAl, Co2MnGa0.5Ge0.5, and Co2FeGa0.5Ge0.5 may be used as the first
magnetization fixed layer 11. For example, a Co40Fe40B20 layer with a thickness of 3 nm is
used as the first magnetization fixed layer 11, for example.
[0020]
The second magnetic layer 20 is, for example, a magnetization free layer. When stress is applied
to the strain sensing element 100 and strain is produced in the strain sensing element 100, the
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magnetization of the second magnetic layer 20 changes. For example, the change of the
magnetization of the second magnetic layer 20 is easier than the change of the magnetization of
the first magnetic layer 10. Thereby, the relative angle between the magnetization of the first
magnetic layer 10 and the magnetization of the second magnetic layer 10 changes.
[0021]
A ferromagnetic material is used for the second magnetic layer 20. In the embodiment, the
second magnetic layer 20 contains Fe 1 -yBy (0 <y ≦ 0.3). The whole of the second magnetic
layer 20 may be formed of Fe 1 -yBy (0 <y ≦ 0.3). For example, Fe 1 -yBy (0 <y ≦ 0.3) is
provided in a region of the second magnetic layer 20 including the interface 20s between the
second magnetic layer 20 and the intermediate layer 30.
[0022]
The second magnetic layer 20 is made of a material in which a part of Fe of Fe1-yBy (0 <y ≦ 0.3)
is substituted by Co or Ni, that is, (FeaX1-a) 1-yBy (0.8) ≦ a <1, 0 <y ≦ 0.3) may be included. In
the aforementioned (FeaX1-a) 1-yBy, X is Co or Ni. That is, in the second magnetic layer 20,
(FeaCo1-a) 1-yBy (0.8 ≦ a <1, 0 <y ≦ 0.3) or (FeaNi1-a) 1-yBy (0.8 ≦ a < 1 and 0 <y ≦ 0.3) may
be included.
[0023]
The entire second magnetic layer 20 may be formed of (FeaX1-a) 1-yBy (0.8 ≦ a <1, 0 <y ≦ 0.3).
That is, the entire second magnetic layer 20 may be formed of (FeaCo1-a) 1-yBy (0.8 ≦ a <1, 0
<y ≦ 0.3). Alternatively, the entire second magnetic layer 20 may be formed of (FeaNi1-a) 1-yBy
(0.8 ≦ a <1, 0 <y ≦ 0.3). For example, (FeaX1-a) 1-yBy (0.8 ≦ a <1, 0 <y ≦ 0.3) is provided in a
region including the boundary surface 20s.
[0024]
The second magnetic layer 20 includes both of Fe1-yBy (0 <y ≦ 0.3) and (FeaX1-a) 1-yBy (0.8 ≦
a <1, 0 <y ≦ 0.3). It may be When X is Co, it is more preferable that (FeaCo1-a) 1-yBy (0.8 ≦ a
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<1, 0 <y ≦ 0.3) be provided in the region including the boundary surface 20s.
[0025]
The second magnetic layer 20 may contain Co40Fe40B20. In this case, Co40Fe40B20 is
provided in the region including the interface 20s. For example, the second magnetic layer 20
includes both of Fe1-yBy (0 <y ≦ 0.3) and Co40Fe40B20. Co40Fe40B20 is provided in the
region including the interface 20s. Alternatively, for example, the second magnetic layer 20
includes both (FaaNi1-a) 1-yBy (0.8 ≦ a <1, 0 <y ≦ 0.3) and Co40Fe40B20. Co40Fe40B20 is
provided in the region including the interface 20s.
[0026]
The second magnetic layer 20 includes an amorphous portion. For example, Fe1-yBy (0 <y ≦
0.3) includes an amorphous state. For example, (FeaX1-a) 1-yBy (0.8 ≦ a <1, 0 <y ≦ 0.3)
includes an amorphous state. The second magnetic layer 20 may include an amorphous portion
and a crystalline portion. For example, the region including the boundary surface 20s includes
the crystalline state, and the region not including the boundary surface 20s includes the
amorphous state.
[0027]
The intermediate layer 30 cuts the magnetic coupling between the first magnetic layer 10 and
the second magnetic layer 20, for example. For the intermediate layer 30, for example, a metal or
an insulator or a semiconductor is used. As this metal, for example, Cu, Au, Ag or the like is used.
When a metal is used as the intermediate layer 30, the thickness of the intermediate layer 30 is,
for example, about 1 nm or more and 7 nm or less. As this insulator or semiconductor, for
example, magnesium oxide (Mg-O etc.), aluminum oxide (Al2O3 etc.), titanium oxide (Ti-O etc.),
zinc oxide (Zn-O etc.), or Gallium oxide (Ga-O) or the like is used. When an insulator or a
semiconductor is used as the intermediate layer 30, the thickness of the intermediate layer 30 is,
for example, about 0.6 nm or more and 2.5 nm or less. As the intermediate layer 30, for example,
a CCP (Current-Confined-Path) spacer layer may be used. When a CCP spacer layer is used as a
spacer layer, for example, a structure in which a copper (Cu) metal path is formed in an
insulating layer of aluminum oxide (Al2O3) is used. For example, an MgO layer of 1.5 nm in
thickness is used as the intermediate layer 30.
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[0028]
For the nonmagnetic layer 40, for example, at least one of an oxide, a nitride and an oxynitride is
used. The nonmagnetic layer 40 is made of, for example, magnesium (Mg), aluminum (Al), silicon
(Si), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mg), iron (Fe), cobalt (cobalt) Co),
nickel (Ni), copper (Cu), zinc (Zn), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium
(Ru), rhodium (Rh), palladium (Pd), silver ( Ag), hafnium (Hf), tantalum (Ta), tungsten (W), tin (Sn),
cadmium (Cd), and at least one oxide selected from the first group consisting of gallium (Ga), and
It contains at least one of at least any of the nitrides selected from the above first group.
[0029]
The nonmagnetic layer 40 may contain, for example, an oxide of at least one selected from the
second group consisting of magnesium, titanium, vanadium, zinc, tin, cadmium and gallium. For
the nonmagnetic layer 40, for example, magnesium oxide is easily used to obtain low resistance.
[0030]
For example, at least one of aluminum (Al), aluminum-copper alloy (Al-Cu), copper (Cu), silver
(Ag), and gold (Au) is used for the first electrode E1 and the second electrode E2. Be By using
such a material having a relatively small electric resistance as the first electrode E1 and the
second electrode E2, current can be efficiently supplied to the strain sensing element 100. A
nonmagnetic material can be used for the first electrode E1.
[0031]
The first electrode E1 may be, for example, an underlayer (not shown) for the first electrode E1, a
cap layer (not shown) for the first electrode E1, and Al, Al- provided between them. And at least
one of Cu, Cu, Ag, and Au. For example, tantalum (Ta) / copper (Cu) / tantalum (Ta) or the like is
used for the first electrode E1. By using Ta as a base layer for the first electrode E1, for example,
the adhesion between the substrate 210 and the first electrode E1 is improved. As a base layer
for the first electrode E1, titanium (Ti), titanium nitride (TiN), or the like may be used.
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[0032]
By using Ta as the cap layer of the first electrode E1, oxidation of copper (Cu) or the like under
the cap layer can be prevented. Titanium (Ti), titanium nitride (TiN), or the like may be used as a
cap layer for the first electrode E1.
[0033]
By applying a voltage between the first electrode E1 and the second electrode E2, a current can
be supplied to the stacked body including the first magnetic layer 10, the intermediate layer 30,
and the second magnetic layer 20. The current is, for example, in the Z-axis direction between
the first magnetic layer 10 and the second magnetic layer 20.
[0034]
A pinning layer (not shown) may be provided between the first electrode E and the first magnetic
layer 10. The pinning layer fixes the magnetization of the first magnetic layer 10 by, for example,
imparting unidirectional anisotropy to the first magnetic layer 10 (ferromagnetic layer) formed
on the pinning layer. . For example, an antiferromagnetic layer is used for the pinning layer. For
the pinning layer, for example, at least one selected from the group consisting of IrMn, PtMn,
PdPtMn and RuRhMn is used. The thickness of the pinning layer is appropriately set to impart
sufficient strength of unidirectional anisotropy.
[0035]
As shown in FIG. 1C, the strain sensing element 100 is used for the pressure sensor 200. The
pressure sensor 200 includes a substrate 210 and a strain sensing element 100. The substrate
210 has a flexible region. The strain sensing element 100 is provided on a part of the substrate
210.
[0036]
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In the present specification, the provided on state includes a state in which other elements
are inserted and provided in addition to the state provided in direct contact.
[0037]
When a force 801 is applied to the substrate 210, the substrate 210 is deformed.
As the substrate 210 deforms, distortion occurs in the strain sensing element 100. In the strain
sensing element 100 according to the embodiment, for example, when the substrate 210 is
deformed by an external force, the strain sensing element 100 is strained. The strain sensing
element 100 converts this change in strain into a change in electrical resistance.
[0038]
The operation in which the strain sensing element 100 functions as a strain sensor is based on
the application of the inverse magnetostrictive effect and the magnetoresistive effect .
The "inverse magnetostrictive effect" is obtained in the ferromagnetic layer used for the
magnetization free layer. The magnetoresistive effect appears in a laminated film of a
magnetization free layer, an intermediate layer, and a reference layer (for example, a
magnetization fixed layer).
[0039]
The inverse magnetostrictive effect is a phenomenon in which the magnetization of a
ferromagnetic material changes due to the strain generated in the ferromagnetic material. That
is, when an external strain is applied to the stacked body of the strain sensing element 100, the
magnetization direction of the magnetization free layer changes. As a result, the relative angle
between the magnetization of the magnetization free layer and the magnetization of the
reference layer (e.g., the magnetization fixed layer) changes. At this time, a change in electrical
resistance is caused by the magnetoresistive effect (MR effect) . The MR effect includes, for
example, a GMR (Giant magnetoresistance) effect or a TMR (Tunneling magnetoresistance) effect.
By passing a current through the stack, the MR effect is expressed by reading the change in the
relative angle of the direction of magnetization as the change in electrical resistance. For
example, strain occurs in the stack (strain sensing element 100), and the strain changes the
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magnetization direction of the magnetization free layer, and the magnetization direction of the
magnetization free layer and the magnetization direction of the reference layer (eg,
magnetization fixed layer) The relative angle of, changes. That is, the MR effect appears due to
the inverse magnetostrictive effect.
[0040]
When the ferromagnetic material used for the magnetization free layer has a positive
magnetostriction constant, the angle between the direction of magnetization and the direction of
tensile strain decreases, and the angle between the direction of magnetization and the direction
of compressive strain increases. , The direction of magnetization changes. When the
ferromagnetic material used for the magnetization free layer has a negative magnetostriction
constant, the angle between the direction of magnetization and the direction of tensile strain
increases, and the angle between the direction of magnetization and the direction of compressive
strain decreases. , The direction of magnetization changes.
[0041]
Hereinafter, the ferromagnetic materials used for the magnetization free layer and the reference
layer (for example, the magnetization fixed layer) respectively have positive magnetostriction
constants, and the magnetization free layer, the intermediate layer, and the reference layer (for
example, the magnetization fixed layer) An example of a change in magnetization will be
described with respect to an example in which the resistance decreases when the relative angle
of magnetization of is small.
[0042]
FIG. 2A to FIG. 2C are schematic views illustrating the operation of the strain sensing element
according to the first embodiment.
FIG. 2A corresponds to the state (tensile state STt) when the tensile stress ts is applied to the
strain sensing element 100. FIG. 2B corresponds to the state (non-distortion state ST0) when the
strain sensing element 100 has no strain. FIG. 2C corresponds to the state (compressed state STc)
when the compressive stress cs is applied to the strain sensing element 100.
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[0043]
In FIGS. 2 (a) to 2 (c), the first magnetic layer 10, the second magnetic layer 20, and the
intermediate layer 30 are drawn to make the figure easy to see. The first electrode E1 and the
second electrode E2 are omitted. In this example, the second magnetic layer 20 is a
magnetization free layer, and the first magnetic layer 10 is a magnetization fixed layer.
[0044]
As shown in FIG. 2B, in the strain free state ST0 (for example, the initial state), the magnetization
20m of the second magnetic layer 20 and the magnetization 10m of the first magnetic layer 10
(for example, the magnetization fixed layer) And the relative angle between them is set to a
predetermined value. The direction of magnetization of the magnetic layer in the initial state is
set, for example, by an external magnetic field, hard bias, shape anisotropy of the magnetic layer,
or the like. In this example, the magnetization 20 m of the second magnetic layer 20
(magnetization free layer) and the magnetization 10 m of the first magnetic layer 10 (for
example, the magnetization fixed layer) intersect.
[0045]
As shown in FIG. 2A, when the tensile stress ts is applied in the tensile state STt, a strain occurs
in the strain sensing element 100 according to the tensile stress ts. At this time, the
magnetization 20m of the second magnetic layer 20 (magnetization free layer) changes from the
non-strain state ST0 so that the angle between the magnetization 20m and the direction of the
tensile stress ts becomes smaller. In the example shown in FIG. 2A, when the tensile stress ts is
applied, the magnetization 20m of the second magnetic layer 20 (magnetization free layer) and
the first magnetic layer 10 (eg, the magnetization free layer) are compared with the unstrained
state ST0. The relative angle between the magnetization 10 m of the magnetization fixed layer) is
reduced. Thereby, the electrical resistance in the strain sensing element 100 is reduced
compared to the electrical resistance in the unstrained state ST0.
[0046]
As shown in FIG. 2C, in the compressed state STc, when a compressive stress cs is applied, the
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magnetization 20m of the second magnetic layer 20 (magnetization free layer) has a
magnetization 20m and a direction of the compressive stress cs. The distortion-free state ST0 is
changed so that the angle is increased. In the example shown in FIG. 2C, when the compressive
stress cs is applied, the magnetization 20m of the second magnetic layer 20 (the magnetization
free layer) and the first magnetic layer 10 (for example, the first magnetic layer 10) as compared
to the unstrained state ST0. The relative angle between the magnetization 10 m of the
magnetization fixed layer) is increased. Thereby, the electrical resistance in the strain sensing
element 100 is increased.
[0047]
As described above, in the strain sensing element 100, a change in strain generated in the strain
sensing element 100 is converted into a change in electric resistance. In the above operation, the
amount of change in electrical resistance (dR / R) per unit strain (dε) is referred to as a gauge
factor (GF). By using a strain sensing element having a high gauge factor, a highly sensitive strain
sensor can be obtained.
[0048]
Here, as described above, the change in the electrical resistance in the strain sensing element
100 is caused by the strain generated in the strain sensing element 100, the magnetization 20m
of the second magnetic layer 20 (magnetization free layer), and the first magnetic layer For
example, it is detected as a resistance change corresponding to the relative angle between the
magnetization 10 m of the magnetization fixed layer). Therefore, increasing the change in
magnetization due to strain and increasing the change in resistance depending on the difference
in relative angle between the magnetization of the first magnetic layer 10 and the magnetization
of the second magnetic layer 20 have high sensitivity. It is required to realize various strain
sensors.
[0049]
In order to make the magnetization of the magnetization free layer easy to move, it is desirable
that the magnetization free layer exhibits soft magnetic properties without strong anisotropy. In
order to make it easy to move the magnetization of the magnetization free layer, it is desirable
that the magnetization free layer include a structure having no magnetocrystalline anisotropy. On
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the other hand, in order to exhibit a high magnetoresistance effect of a certain level or more, it is
desirable that the magnetization free layer contain a certain crystal structure. The trade-off of
such characteristics may hinder the realization of the improvement of the sensitivity of the strain
sensing element 100 and the pressure sensor 200.
[0050]
The sensitivity of the strain sensing element 100 depends on, for example, the materials of the
first magnetic layer 10 and the second magnetic layer 20. For this reason, a magnetic material
that produces a larger resistance change even with a slight strain is required. However, while
there are relatively many magnetic materials that exhibit excellent properties for
magnetostriction, soft magnetic properties and magnetoresistance, respectively, magnetic
materials that exhibit excellent properties for magnetostriction, soft magnetic properties and
magnetoresistance are all known. It is not done. Therefore, it may be difficult to improve the
sensitivity of the strain sensing element.
[0051]
On the other hand, in the strain sensing element 100 according to the embodiment, the second
magnetic layer 20 includes Fe1−yBy (0 <y ≦ 0.3). Alternatively, the second magnetic layer 20
includes (FeaX1-a) 1-yBy (0.8 ≦ a <1, 0 <y ≦ 0.3). Alternatively, the second magnetic layer 20
may have both Fe1-yBy (0 <y ≦ 0.3) and (FeaX1-a) 1-yBy (0.8 ≦ a <1, 0 <y ≦ 0.3). Including.
（ＦｅａＸ１−ａ）１−ｙＢｙにおいて、Ｘは、ＣｏまたはＮｉである。
[0052]
According to this, it is possible to improve the sensitivity of the strain sensing element 100 by
making the magnetostriction, the soft magnetic characteristics, and the magnetoresistive effect
side by side. Details of this will be described later.
[0053]
The amorphous state ideally has no magnetocrystalline anisotropy and exhibits excellent soft
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magnetic properties. Fe-based amorphous is known to exhibit relatively large magnetostriction.
On the other hand, in order to exhibit the magnetoresistance effect, crystallinity is required at the
interface 20s between the second magnetic layer 20 and the intermediate layer 30. When the
region of the second magnetic layer 20 including the interface 20s has crystallinity, higher
magnetoresistive effect can be obtained.
[0054]
Therefore, in the case where the region of the second magnetic layer 20 including the interface
20s is crystalline and the region of the second magnetic layer 20 not including the interface 20s
is amorphous, magnetostriction, The soft magnetic properties and the magnetoresistive effect
can be made parallel. In the case where the second magnetic layer 20 includes both of Fe1-yBy
(0 <y ≦ 0.3) and (FeaX1-a) 1-yBy (0.8 ≦ a <1, 0 <y ≦ 0.3) In the case where (FeaX1-a) 1-yBy
(0.8 ≦ a <1, 0 <y ≦ 0.3) is provided in a region including the boundary surface 20s when X is
Co, a constant The soft magnetic characteristics and the magnetostriction can be made parallel
while exhibiting the magnetoresistance effect. According to this, the sensitivity of the strain
sensing element 100 can be further improved.
[0055]
Information on the distribution of the boron (B) concentration in the second magnetic layer 20
can be obtained by SIMS analysis (secondary ion mass spectrometry). The combination of crosssectional TEM and EDX provides this information. This information is obtained by EELS analysis.
Three-dimensional atom probe analysis can also provide this information.
[0056]
In the strain sensing element 100 according to the embodiment, the second magnetic layer 20 is
provided between the intermediate layer 30 and the nonmagnetic layer 40. The material used for
the nonmagnetic layer 40 is, for example, as described above. According to this, the diffusion of
boron (B) is suppressed, and the boron concentration in the second magnetic layer 20 is
maintained. Therefore, deterioration of the characteristics of the second magnetic layer 20 can
be suppressed. For example, in the strain sensing element 100, a smaller coercive force Hc and a
higher gauge factor can be obtained by a magnetization change due to a larger magnetostriction.
05-05-2019
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[0057]
Next, an example of an experimental result of the strain sensing element 100 according to the
embodiment will be described with reference to the drawings. FIG. 3A to FIG. 3C are graphs
showing examples of experimental results of the strain sensing element according to the
embodiment. The second magnetic layer 20 of the strain sensing element 100 in the example of
the experimental result of FIGS. 3A to 3C contains Fe 1 -yBy. The example of the experimental
result regarding the atomic weight ratio y of boron (B) at this time is as having represented to
FIG. 3 (a)-FIG.3 (c).
[0058]
FIG. 3A shows an example of the relationship between the MR ratio and the atomic weight ratio y
of boron in the strain sensing element according to the embodiment. FIG. 3B illustrates an
example of the relationship between the coercive force Hc and the atomic weight ratio y of boron
in the strain sensing element according to the embodiment. FIG. 3C shows an example of the
relationship between the gauge factor B (GFB) and the atomic weight ratio y of boron.
[0059]
The inventor uses the gauge factor B (GFB) index to evaluate the strain sensing element 100
according to the embodiment. GFB is expressed as a multiplier of the rate of magnetization
change due to MR and strain, and is proportional to the gauge factor (GF). That is, if GFB is
relatively large, relatively high GF can be obtained. When GFB is relatively small, relatively low
GF is obtained. As described above with reference to FIGS. 2A to 2C, by using a strain sensing
element with a high gauge factor, a highly sensitive strain sensor can be obtained. In order to
obtain a highly sensitive strain sensor, higher GF (greater GFB) is desired.
[0060]
The coercive force Hc is a characteristic index indicating the ease of magnetization rotation. In
order to obtain a highly sensitive strain sensor, a smaller coercive force Hc is desired. As
described above with reference to FIGS. 1A to 1C, the MR effect is an effect obtained by reading a
05-05-2019
17
change in the relative angle of the direction of magnetization as a change in electrical resistance.
In order to obtain a highly sensitive strain sensor, ie, to increase the resistance change depending
on the difference in relative angle between the magnetization of the first magnetic layer 10 and
the magnetization of the second magnetic layer 20, a higher MR change A rate is desired.
[0061]
As shown in FIG. 3A, when the atomic weight ratio y of boron is larger than 0.3, it is understood
that the MR is relatively small. As shown in FIG. 3B, it can be seen that a relatively small coercive
force Hc can be obtained when the atomic weight ratio y of boron is 0.3. As shown in FIG. 3C, it
can be seen that when the atomic weight ratio y of boron is 0.3, the magnetization change due to
strain occurs sufficiently, and a GFB of 4000 or more can be obtained. Accordingly, the atomic
weight ratio y of boron in the second magnetic layer 20 is preferably 0.3 or less.
[0062]
On the other hand, as shown in FIG. 3A, when the second magnetic layer 20 does not contain
boron (in the case of y = 0), it can be seen that the MR is relatively small. As shown in FIG. 3B, it
can be seen that the coercivity Hc is relatively large when the second magnetic layer 20 does not
contain boron (in the case of y = 0). As shown in FIG. 3C, when the second magnetic layer 20
does not contain boron (in the case of y = 0), it can be seen that there is almost no change in
magnetization due to strain, and the GFB is about 0. . Accordingly, the atomic weight ratio y of
boron in the second magnetic layer 20 is preferably larger than zero.
[0063]
As shown in FIGS. 3A to 3C, the atomic weight ratio y of boron in the second magnetic layer 20 is
preferably greater than 0 and 0.3 or less. As represented to FIG. 3 (a)-FIG.3 (c), it is more
preferable that the atomic weight ratio y of the boron of the 2nd magnetic layer 20 is 0.1 or
more and 0.3 or less.
[0064]
05-05-2019
18
FIG. 4A to FIG. 4C are graphs showing an example of another experimental result of the strain
sensing element according to the embodiment. The second magnetic layer 20 of the strain
sensing element 100 in the example of the experimental results of FIGS. 4A to 4C includes
(FeaCo1-a) 1-yBy. The example of the experimental result regarding the atomic weight ratio a of
iron (Fe) at this time, in other words, the atomic weight ratio 1-a of cobalt (Co) at this time, is as
shown in FIG. 4A to FIG. It is.
[0065]
FIG. 4A shows an example of the relationship between the MR ratio and the atomic weight ratio a
of iron in the strain sensing element according to the embodiment. FIG. 4B illustrates an example
of the relationship between the coercive force Hc and the atomic weight ratio a of iron in the
strain sensing element according to the embodiment. FIG. 4C shows an example of the
relationship between the gauge factor B (GFB) and the atomic weight ratio a of iron. In the
present study, the atomic weight ratio y of boron is 0.1 ≦ y <0.3.
[0066]
As shown in FIG. 4C, it is understood that when the atomic weight ratio a of iron is about 0.8 or
more, GFB of 4000 or more can be obtained. In other words, when the atomic weight ratio 1-a of
cobalt is about 0.2 or less, it can be seen that GFB of 4000 or more can be obtained. At this time,
as shown in FIG. 4A, it can be seen that a relatively large MR can be obtained. As shown in FIG.
4B, it can be seen that a relatively small coercive force Hc can be obtained. Thus, the atomic
weight ratio a of iron of the second magnetic layer 20 is preferably 0.8 or more. In other words,
the atomic weight ratio 1-a of cobalt of the second magnetic layer 20 is preferably 0.2 or less.
[0067]
FIG. 5A to FIG. 5C are graphs showing an example of another experimental result of the strain
sensing element according to the embodiment. The second magnetic layer 20 of the strain
sensing element 100 in the example of the experimental result of FIGS. 5A to 5C includes
(FaaNi1-a) 1-yBy. The example of the experimental result regarding the atomic weight ratio a of
iron (Fe) at this time, in other words, the atomic weight ratio 1-a of nickel (Ni) at this time, is as
shown in FIGS. 5 (a) to 5 (c). It is.
05-05-2019
19
[0068]
FIG. 5A shows an example of the relationship between the MR ratio and the atomic weight ratio a
of iron in the strain sensing element according to the embodiment. FIG. 5B shows an example of
the relationship between the coercive force Hc and the atomic weight ratio a of iron in the strain
sensing element according to the embodiment. FIG. 4C shows an example of the relationship
between the gauge factor B (GFB) and the atomic weight ratio a of iron. In the present study, the
atomic weight ratio y of boron is 0.1 ≦ y <0.3.
[0069]
As shown in FIG. 5C, it can be seen that when the atomic weight ratio a of iron is about 0.8 or
more, GFB of 4000 or more can be obtained. In other words, when the atomic weight ratio 1-a of
nickel is about 0.2 or less, it can be seen that GFB of 4000 or more can be obtained. At this time,
as shown in FIG. 5A, it can be seen that a relatively large MR can be obtained. As shown in FIG. 5
(b), it can be seen that a relatively small coercive force Hc can be obtained. Thus, the atomic
weight ratio a of iron of the second magnetic layer 20 is preferably 0.8 or more. In other words,
the atomic weight ratio 1-a of nickel of the second magnetic layer 20 is preferably 0.2 or less.
[0070]
FIG. 6A to FIG. 6C are graphs showing an example of another experimental result of the strain
sensing element according to the embodiment. The second magnetic layer 20 of the strain
sensing element 100 in the example of the experimental result of FIGS. 6A to 6C contains Fe 1yBy. The example of the experimental result regarding thickness t of Fe1-yBy at this time is as
having represented to Fig.6 (a)-FIG.6 (c).
[0071]
FIG. 6A shows an example of the relationship between the MR ratio and the thickness t of Fe1yBy in the strain sensing element according to the embodiment. FIG. 6B shows an example of the
relationship between the coercive force Hc and the thickness t of Fe1-yBy in the strain sensing
element according to the embodiment. FIG. 6C shows an example of the relationship between the
05-05-2019
20
gauge factor B (GFB) and the thickness t of Fe1-yBy.
[0072]
As shown in FIG. 6A, it can be seen that a relatively large MR can be obtained when the thickness
t of Fe1-yBy is 2 nanometers (nm) or more. When the thickness t of Fe1-yBy is smaller than 2
nm, the MR decreases. Then, sufficient magnetic properties may not be obtained. As shown in
FIG. 6B, it can be seen that a relatively small coercive force Hc can be obtained when the
thickness t of Fe 1 -yBy is 2 nm or more. As shown in FIG. 6C, it can be seen that when the
thickness t of Fe1-yBy is 2 nm or more, GFB of 4000 or more can be obtained. Thereby, it is
preferable that thickness t of Fe1-yBy is 2 nm or more.
[0073]
When the thickness t of Fe1-yBy is 2 nm or more, the region including the interface 20s of the
second magnetic layer 20 is maintained to have crystallinity, and the interface of the second
magnetic layer 20 is maintained. It is possible to maintain that the region not including 20s is in
an amorphous state.
[0074]
On the other hand, as shown in FIG. 6C, when the thickness t of Fe1-yBy is larger than 12 nm, it
can be seen that GFB becomes smaller than 4000 and becomes a relatively small value.
Thus, the thickness t of Fe 1 -yBy is more preferably 12 nm or less.
[0075]
As represented to Fig.6 (a)-FIG.6 (c), it is preferable that thickness t of Fe1-yBy is 2 nm or more.
As represented to Fig.6 (a)-FIG.6 (c), it is more preferable that thickness t of Fe1-yBy is 2 nm or
more and 12 nm or less.
[0076]
05-05-2019
21
FIG. 7A to FIG. 7C are graphs showing an example of another experimental result of the strain
sensing element according to the embodiment. The second magnetic layer 20 of the strain
sensing element 100 in the example of the experimental result of FIGS. 7A to 7C includes both of
Fe 1 -yBy and Co 40 Fe 40 B 20. Co40Fe40B20 is provided in the region including the interface
20s. The example of the experimental result regarding thickness t of Fe1-yBy at this time is as
having represented to Fig.7 (a)-FIG.7 (c). In this experiment, the thickness l of Co40Fe20B20 is
set to 0 nm, 0.5 nm, and 1 nm, respectively.
[0077]
FIG. 7A shows an example of the relationship between the MR ratio and the thickness t of Fe1yBy in the strain sensing element according to the embodiment. FIG. 7B shows an example of the
relationship between the coercive force Hc and the thickness t of Fe1-yBy in the strain sensing
element according to the embodiment. FIG. 7C shows an example of the relationship between the
gauge factor B (GFB) and the thickness t of Fe1-yBy.
[0078]
As shown in FIG. 7C, it can be seen that even when Co40Fe40B20 of several nm is provided on
the boundary surface 20s, 4000 or more GFBs can be obtained. This is because, as shown in FIG.
7A, an MR larger than that of FeB alone is obtained, and as shown in FIG. 7B, a relatively small
coercive force Hc is obtained. From this, when both Fe1-yBy and Co40Fe40B20 are included in
the twentieth magnetic layer, it is desirable that Co40Fe40B20 be provided in the region
including the interface 20s. By providing Co40Fe40B20 which is easy to be crystallized at the
interface, it is possible to increase the MR and to realize a strain sensor sensitive to changes in
spin direction.
[0079]
FIG. 8A to FIG. 8C are graphs showing an example of another experimental result of the strain
sensing element according to the embodiment. The second magnetic layer 20 of the strain
sensing element 100 in the example of the experimental results of FIGS. 8A to 8C is (FeaNi 1-a)
1-yBy (0.8 ≦ a <1, 0 <y ≦ 0.3) and Co40Fe40B20. Co40Fe40B20 is provided in the region
05-05-2019
22
including the interface 20s. The example of the experimental result regarding thickness t of
(FeaNi1-a) 1-yBy (0.8 <= a <1 and 0 <y <= 0.3) at this time is shown in Drawing 8 (a)-Drawing 8
(c). As shown in. In this experiment, the thickness l of Co40Fe20B20 is set to 0 nm, 0.5 nm, and 1
nm, respectively.
[0080]
FIG. 8A shows the MR ratio and the thickness t of (FeaNi1-a) 1-yBy (0.8 ≦ a <1, 0 <y ≦ 0.3) in
the strain sensing element according to the embodiment. Represents an example of the
relationship between FIG. 8B shows the strain sensing element according to the embodiment, in
which the coercive force Hc and the thickness t of (FeaNi1-a) 1-yBy (0.8 ≦ a <1, 0 <y ≦ 0.3)
Represents an example of the relationship between FIG. 8C shows an example of the relationship
between the gauge factor B (GFB) and the thickness t of (FeaNi1-a) 1-yBy (0.8 ≦ a <1, 0 <y ≦
0.3). .
[0081]
As shown in FIG. 8C, even when a few nm of Co40Fe40B20 is provided at the boundary surface
20s, a GFB of 4000 or more can be obtained, and it is possible to exceed the configuration of
only (FeaNi1-a) 1-yBy. I understand that. This is because, as shown in FIG. 8 (a), a larger MR is
obtained than in the case of (FeaNi1-a) 1-yBy alone, and as shown in FIG. 8 (b), a relatively small
coercive force Hc is obtained. Can maintain In other words, it is because it is possible to purchase
a minute increment of the coercive force Hc by an increase of the MR. From this, when both
(FeaNi1-a) 1-yBy and Co40Fe40B20 are included in the second magnetic layer 20, it is desirable
that Co40Fe40B20 be provided in a region including the interface 20s. By providing
Co40Fe40B20 which is easy to be crystallized at the interface, it is possible to increase the MR
and to realize a strain sensor sensitive to changes in spin direction.
[0082]
FIG. 9A to FIG. 9D are graphs showing an example of another experimental result of the strain
sensing element. FIG. 9A and FIG. 9B are graphs showing an example of another experimental
result of the strain sensing element according to the embodiment. FIG.9 (c) and FIG.9 (d) are
graphs showing the example of another experimental result of the distortion detection element
which concerns on a comparative example.
05-05-2019
23
[0083]
The vertical axes in FIG. 9A and FIG. 9C represent the magnetic film thickness (the product (Bs ·
t) of the saturation magnetization Bs and the thickness t). The horizontal axes in FIG. 9 (a) and
FIG. 9 (c) represent the magnetic field. That is, Fig.9 (a) and FIG.9 (c) represent what is called a
BH curve (BH loop). The vertical axes in FIG. 9B and FIG. 9D represent a constant magnetic field
(in this example, a zero magnetic field). The horizontal axes in FIG. 9 (b) and FIG. 9 (d) represent
distortion.
[0084]
The second magnetic layer 20 of the strain sensing element 100 according to the embodiment in
the example of the experimental result of FIGS. 9A and 9B contains Fe 1-yBy. The second
magnetic layer 20 of the strain sensing element according to the comparative example in the
example of the experimental result of FIG. 9C and FIG. 9C includes Co40Fe40B20.
[0085]
When the graph of FIG. 9A and the graph of FIG. 9C are compared with each other, when the
second magnetic layer 20 includes Fe1-yBy, B-H changes significantly when strain is applied. Do.
Thereby, when the graph of FIG. 9B and the graph of FIG. 9D are compared with each other,
when the second magnetic layer 20 includes Fe1-yBy, B at a constant magnetic field is largely
caused by strain. It can be changed. Therefore, according to this magnetic material (material
including Fe1-yBy), it is possible to realize a strain sensor having high sensitivity under the
condition including a certain amount of boron. The GFB of Co40Fe40B20 of the strain sensing
element according to the comparative example is about 1,500.
[0086]
FIG. 10A to FIG. 10D are graphs showing examples of the results of strain sensor characteristics
of the strain sensing element of the embodiment. In the example shown in FIG. 10A, with respect
to the strain sensing element 100 having an element size of 20 μm × 20 μm, the strain applied
05-05-2019
24
to the strain sensing element 100 is −0.8 (% 0) or more and 0.8 (% 0) or less Between them, set
as a fixed value in 0.2 (% 0) increments. FIG. 10A shows an example of the result of measuring
the magnetic field dependency of the electrical resistance at each strain. From FIG. 10A, it can be
seen that the R-H loop shape is changed depending on the value of the applied strain. This
indicates that the in-plane magnetic anisotropy of the magnetization free layer is changed by the
inverse magnetostrictive effect.
[0087]
10 (b) to 10 (d), in the strain sensing element 100, the external magnetic field is fixed, and the
strain is continuously between -0.8 (% 0) and 0.8 (% 0) or less. The change of the electrical
resistance in the case of sweeping is shown. For distortion, sweep from -0.8 (% 0) to 0.8 (% 0)
and then sweep from 0.8 (% 0) to -0.8 (% 0). These results show the strain sensor characteristics.
In FIG. 10 (b), evaluation is performed by applying an external magnetic field of 5 Oe. In FIG. 10
(c), evaluation is performed by applying an external magnetic field of 2 Oe. In FIG. 10D, the
evaluation is performed at 0 Oe.
[0088]
In the strain sensing element 100 of the embodiment, a high gauge factor can be obtained by
applying an appropriate bias magnetic field. The external magnetic field can also be applied by
providing a hard bias on the sidewall of the strain sensing element or an in-stack bias on the top
of the magnetization free layer. In the strain sensing element 100 of the embodiment, an external
magnetic field is simply applied by a coil and evaluated. The gauge factor is estimated from the
change in electrical resistance with respect to strain from FIGS. 10 (b) to 10 (d).
[0089]
The gauge factor is expressed by the following equation. GF = (dR / R) / dε From FIG. 10B, the
gauge factor when the external magnetic field is 5 Oe is 3086. As shown in FIG. 10C, the gauge
factor when the external magnetic field is 2Oe is 4418. From FIG. 10D, the gauge factor when
the external magnetic field is 0 Oe is 5290. From this result, the maximum gauge factor (5290) is
obtained when the bias magnetic field is 0 Oe.
05-05-2019
25
[0090]
11A and 11B are schematic views illustrating another strain sensing element according to the
first embodiment. FIG. 11A is a schematic perspective view of the strain sensing element. FIG.
11B is a schematic cross-sectional view of the strain sensing element. In FIG. 11B, the first
electrode and the second electrode are omitted for the convenience of description.
[0091]
As illustrated in FIG. 11A, the strain sensing element 100a according to the embodiment includes
a first magnetic layer 10, a second magnetic layer 20, and an intermediate layer 30. In this
example, the strain sensing element 100a further includes a first nonmagnetic layer 51, a second
nonmagnetic layer 52, a first electrode E1, and a second electrode E2. The first nonmagnetic
layer 51 and the second nonmagnetic layer 52 may not necessarily be provided.
[0092]
In the strain sensing element 100 described above with reference to FIGS. 1A and 1B, the first
magnetic layer 10 is a magnetization fixed layer. On the other hand, in the strain sensing element
100a shown in FIGS. 11A and 11B, the first magnetic layer 10 is a magnetization free layer.
[0093]
In this example, the second electrode E2 is provided separately from the first electrode E1 in the
stacking direction. The first nonmagnetic layer 51 is provided between the first electrode E1 and
the second electrode E2. The first magnetic layer 10 is provided between the first nonmagnetic
layer 51 and the second electrode E2. An intermediate layer 30 is provided between the first
magnetic layer 10 and the second electrode E2. The second magnetic layer 20 is provided
between the intermediate layer 30 and the second electrode E2. The second nonmagnetic layer
52 is provided between the second magnetic layer 20 and the second electrode E2.
[0094]
05-05-2019
26
In the strain sensing element 100 a shown in FIG. 11A and FIG. 11B, a ferromagnetic material is
used for the first magnetic layer 10. The first magnetic layer 10 contains the same material as
the second magnetic layer 20 described above with reference to FIGS. 1 (a) and 1 (b). That is, in
this example, the first magnetic layer 10 contains Fe1-yBy (0 <y ≦ 0.3). Alternatively, the first
magnetic layer 10 includes (FeaX1-a) 1-yBy (0.8 ≦ a <1, 0 <y ≦ 0.3). Alternatively, in the first
magnetic layer 10, both of Fe1-yBy (0 <y ≦ 0.3) and (FeaX1-a) 1-yBy (0.8 ≦ a <1, 0 <y ≦ 0.3)
can be obtained. Including. （ＦｅａＸ１−ａ）１−ｙＢｙにおいて、Ｘは、ＣｏまたはＮｉであ
る。
[0095]
The first nonmagnetic layer 51 contains the same material as the nonmagnetic layer 40
described above with reference to FIGS. 1 (a) and 1 (b). The second nonmagnetic layer 52
includes the same material as the nonmagnetic layer 40 described above with reference to FIGS.
1 (a) and 1 (b). The second magnetic layer 20 is as described above with reference to FIGS. 1 (a)
and 1 (b). The intermediate layer 30 is as described above with reference to FIGS. 1 (a) and 1 (b).
The first electrode E1 is as described above with reference to FIGS. 1 (a) and 1 (b). FIG. 2
electrode E2 is as described above with reference to FIGS. 1 (a) and 1 (b).
[0096]
Also in the strain sensing element 100a according to the embodiment, as in the strain sensing
element 100 according to the embodiment, the magnetostriction, the soft magnetic
characteristics, and the magnetoresistance effect can be made to stand up to improve the
sensitivity of the strain sensing element 100a. Note that at least one of between the first
nonmagnetic layer 51 and the first electrode E1, and between the second nonmagnetic layer 52
and the second electrode E2, the magnetization fixed layer and pinning (not shown) described
above with reference to FIG. Layers may be provided. Second Embodiment An embodiment
relates to a pressure sensor. In the pressure sensor, at least one of the strain sensing element
100, 100a of the first embodiment and the strain sensing element of the deformation thereof is
used. Hereinafter, the case where the strain sensing element 100 is used as the strain sensing
element will be described.
[0097]
05-05-2019
27
12 (a) and 12 (b) are schematic perspective views illustrating the pressure sensor according to
the second embodiment. FIG. 12 (a) is a schematic perspective view. FIG. 12B is a cross-sectional
view taken along line A1-A2 of FIG. As shown in FIGS. 12A and 12B, the pressure sensor 200
according to the embodiment includes a substrate 210 and a strain sensing element 100.
[0098]
As shown in FIGS. 12A and 12B, the pressure sensor 200 according to the embodiment includes
a support portion 201, a substrate 210, and a strain sensing element 100.
[0099]
The substrate 210 is supported by the support unit 201.
The substrate 210 has, for example, a flexible region. The substrate 210 is, for example, a
diaphragm. The substrate 210 may be integral with or separate from the support portion 201.
For the substrate 210, the same material as that of the support portion 201 may be used, or a
material different from that of the support portion 201 may be used. A part of the support
portion 201 may be removed, and the thin portion of the support portion 201 may be the
substrate 210.
[0100]
The thickness of the substrate 210 is thinner than the thickness of the support portion 201.
When the same material is used for the substrate 210 and the support portion 201 and they are
integrated, the thin portion is the substrate 210 and the thick portion is the support portion 201.
[0101]
The support portion 201 may have a through hole 201 h penetrating the support portion 201 in
the thickness direction, and the substrate 210 may be provided to cover the through hole 201 h.
At this time, for example, a film of a material to be the substrate 210 may extend on a portion
05-05-2019
28
other than the through hole 201 h of the support portion 201. At this time, in the film of the
material to be the substrate 210, the portion overlapping the through hole 201h becomes the
substrate 210.
[0102]
The substrate 210 has an outer edge 210r. When the same material is used for the substrate 210
and the support portion 201 and they are integrated, the outer edge of the thin portion is the
outer edge 210 r of the substrate 210. In the case where the support portion 201 has a through
hole 201 h penetrating the support portion 201 in the thickness direction and the substrate 210
is provided so as to cover the through hole 201 h, The outer edge of the portion overlapping the
through hole 201 h is the outer edge 210 r of the substrate 210.
[0103]
The support portion 201 may support the outer edge 210 r of the substrate 210 continuously or
may support a part of the outer edge 210 r of the substrate 210.
[0104]
The strain sensing element 100 is provided on the substrate 210.
For example, the strain sensing element 100 is provided on a part of the substrate 210. In this
example, a plurality of strain sensing elements 100 are provided on a substrate 210. The number
of strain sensing elements provided on the film portion may be one.
[0105]
In the pressure sensor 200 shown in FIG. 12, a first wire 221 and a second wire 222 are
provided. The first wiring 221 is connected to the strain sensing element 100. The second wiring
222 is connected to the strain sensing element 100. For example, an interlayer insulating film is
provided between the first wiring 221 and the second wiring 222, and the first wiring 221 and
the second wiring 222 are electrically insulated. A voltage is applied between the first wiring 221
and the second wiring 222, and this voltage is applied to the strain sensing element 100 via the
05-05-2019
29
first wiring 221 and the second wiring 222. When pressure is applied to the pressure sensor
200, the substrate 210 is deformed. In the strain sensing element 100, the electrical resistance R
changes with the deformation of the substrate 210. The pressure can be detected by detecting
the change in the electrical resistance R via the first wiring 221 and the second wiring 222.
[0106]
For the support portion 201, for example, a plate-like substrate can be used. For example, a
hollow portion (through hole 201 h) is provided inside the substrate.
[0107]
For the support portion 201, for example, a semiconductor material such as silicon, a conductive
material such as metal, or an insulating material can be used. The support portion 201 may
include, for example, silicon oxide or silicon nitride. The inside of the hollow portion (through
hole 201h) is, for example, in a reduced pressure state (vacuum state). The interior of the hollow
portion (through hole 201 h) may be filled with a gas such as air or a liquid. The inside of the
hollow portion (through hole 201 h) is designed to allow the substrate 210 to bend. The inside of
the hollow portion (through hole 201 h) may be connected to the outside atmosphere.
[0108]
A substrate 210 is provided on the hollow portion (through hole 201 h). For the substrate 210,
for example, a part of the support portion 201 is processed to be thin. The thickness (length in
the Z-axis direction) of the substrate 210 is thinner than the thickness (length in the Z-axis
direction) of the support portion 201.
[0109]
When pressure is applied to the substrate 210, the substrate 210 deforms. This pressure
corresponds to the pressure to be detected by the pressure sensor 200. The applied pressure
also includes pressure by sound waves or ultrasonic waves. The pressure sensor 200 functions as
a microphone in the case of detecting a pressure by a sound wave or an ultrasonic wave.
05-05-2019
30
[0110]
For the substrate 210, for example, an insulating material is used. The substrate 210 includes, for
example, at least one of silicon oxide, silicon nitride, and silicon oxynitride. For the substrate 210,
for example, a semiconductor material such as silicon may be used. For the substrate 210, for
example, a metal material may be used.
[0111]
The thickness of the substrate 210 is, for example, not less than 0.1 micrometers (μm) and not
more than 3 μm. The thickness is preferably 0.2 μm or more and 1.5 μm or less. For the
substrate 210, for example, a stacked body of a silicon oxide film with a thickness of 0.2 μm and
a silicon film with a thickness of 0.4 μm may be used.
[0112]
Hereinafter, the example of the manufacturing method of the pressure sensor which concerns on
embodiment is demonstrated. The following is an example of a method of manufacturing a
pressure sensor. FIG. 13A to FIG. 13E are schematic cross-sectional views in order of processes
illustrating the manufacturing direction of the pressure sensor according to the embodiment.
[0113]
As shown in FIG. 13A, a thin film 242 is formed on a base 241 (for example, a Si substrate). The
base body 241 becomes the support portion 201. The thin film 242 serves as the substrate 210.
For example, a thin film 242 of SiOx / Si is formed on a Si substrate by sputtering. As the thin
film 242, a SiOx single layer, a SiN single layer, or a metal layer such as Al may be used. In
addition, as the thin film 242, a flexible plastic material such as polyimide or a paraxylylene
polymer may be used. An SOI (Silicon On Insulator) substrate may be used as the substrate 241
and the thin film 242. In the SOI, for example, a laminated film of SiO 2 / Si is formed on a Si
substrate by bonding the substrates.
05-05-2019
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[0114]
As shown in FIG. 13B, the second wiring 222 is formed. In this process, a conductive film to be
the second wiring 222 is formed, and the conductive film is processed by photolithography and
etching. When the periphery of the second wiring 222 is embedded with an insulating film, liftoff processing may be applied. In the lift-off process, for example, after etching of the pattern of
the second wiring 222, an insulating film is formed on the entire surface before removing the
resist, and then the resist is removed.
[0115]
As shown in FIG. 13C, the strain sensing element 100 is formed. In this process, a laminate to be
the strain sensing element 100 is formed, and the laminate is processed by photolithography and
etching. In the case where the side wall of the layered body of the strain sensing element 100 is
embedded with an insulating layer, lift-off processing may be applied. In the lift-off process, for
example, after processing of a laminated body, before peeling off a resist, an insulating layer is
formed on the entire surface, and then the resist is removed.
[0116]
As shown in FIG. 13D, the first wiring 221 is formed. In this process, a conductive film to be the
first wiring 221 is formed, and the conductive film is processed by photolithography and etching.
When the periphery of the first wiring 221 is embedded with an insulating film, lift-off
processing may be applied. In the lift-off process, after the processing of the first wiring 221,
before the resist is peeled off, an insulating film is formed on the entire surface, and then the
resist is removed.
[0117]
As shown in FIG. 13E, etching is performed from the back surface of the base 241 to form a
cavity 201a. Thus, the substrate 210 and the support portion 201 are formed. For example, in
the case of using a laminated film of SiO x / Si as the thin film 242 to be the substrate 210, the
base 241 is deep-worked from the back surface (lower surface) of the thin film 242 toward the
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surface (upper surface). Thus, the hollow portion 201a is formed. In forming the hollow portion
201a, for example, a double-sided aligner exposure apparatus can be used. Thus, the hole pattern
of the resist can be patterned on the back surface in accordance with the position of the strain
sensing element 100 on the front surface.
[0118]
For etching a Si substrate, for example, a Bosch process using RIE can be used. In the Bosch
process, for example, an etching process using SF6 gas and a deposition process using C4F8 gas
are repeated. Thereby, etching is selectively performed in the depth direction (Z-axis direction) of
the base 241 while suppressing the etching of the side wall of the base 241. For example, a SiOx
layer is used as an etching end point. That is, the etching is terminated using an SiOx layer whose
etching selectivity is different from that of Si. The SiOx layer that functions as an etching stopper
layer may be used as part of the substrate 210. The SiO x layer may be removed after etching, for
example, by treatment with anhydrous hydrogen fluoride and alcohol.
[0119]
Thus, the pressure sensor 200 according to the embodiment is formed. Other pressure sensors
according to the embodiment can be manufactured by the same method.
[0120]
Third Embodiment FIG. 14 is a schematic plan view illustrating a microphone according to a third
embodiment. As shown in FIG. 14, the microphone 410 includes any pressure sensor (for
example, the pressure sensor 200) according to each of the above-described embodiments, and a
pressure sensor according to the deformation thereof. In the following, as an example, a
microphone 410 having a pressure sensor 200 is illustrated.
[0121]
Microphone 410 is incorporated at the end of portable information terminal 420. The substrate
210 of the pressure sensor 200 provided in the microphone 410 can be, for example,
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substantially parallel to the surface provided with the display unit 421 of the portable
information terminal 420. Note that the arrangement of the substrate 210 is not limited to the
illustrated one and can be changed as appropriate. The microphone 410 includes the pressure
sensor 200 and the like, and thus can be highly sensitive to a wide range of frequencies.
[0122]
Although the case where the microphone 410 is incorporated in the portable information
terminal 420 is illustrated, the present invention is not limited to this. The microphone 410 can
also be incorporated into, for example, an IC recorder or a pin microphone.
[0123]
Fourth Embodiment The embodiment relates to an acoustic microphone using the pressure
sensor of each of the above embodiments. FIG. 15 is a schematic cross-sectional view illustrating
an acoustic microphone according to the fourth embodiment. The acoustic microphone 430
according to the embodiment includes a printed circuit board 431, a cover 433, and a pressure
sensor 200. The printed circuit board 431 includes, for example, a circuit such as an amplifier.
The cover 433 is provided with an acoustic hole 435. The sound 439 enters the inside of the
cover 433 through the acoustic hole 435.
[0124]
As the pressure sensor 200, any one of the pressure sensors described in regard to each of the
above-described embodiments and its variation are used.
[0125]
The acoustic microphone 430 is sensitive to sound pressure.
By using the highly sensitive pressure sensor 200, a highly sensitive acoustic microphone 430
can be obtained. For example, the pressure sensor 200 is mounted on the printed circuit board
431 and an electrical signal line is provided. A cover 433 is provided on the printed circuit board
431 so as to cover the pressure sensor 200. According to the embodiment, a highly sensitive
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acoustic microphone can be provided.
[0126]
Fifth Embodiment The embodiment relates to a blood pressure sensor using the pressure sensor
of each of the above embodiments. FIG. 16A and FIG. 16B are schematic views illustrating the
blood pressure sensor according to the fifth embodiment. FIG. 16 (a) is a schematic plan view
illustrating the skin on human arterial blood vessels. FIG. 16B is a cross-sectional view taken
along line H1-H2 of FIG.
[0127]
In an embodiment, pressure sensor 200 is applied as blood pressure sensor 440. As this pressure
sensor 200, any one of the pressure sensors described in regard to each of the above-described
embodiments, and a variation thereof are used.
[0128]
This enables highly sensitive pressure detection with a small size pressure sensor. By pressing
the pressure sensor 200 against the skin 443 on the arterial blood vessel 441, the blood
pressure sensor 440 can perform blood pressure measurement continuously. According to the
present embodiment, a highly sensitive blood pressure sensor can be provided.
[0129]
Sixth Embodiment The embodiment relates to a touch panel using the pressure sensor of each of
the above embodiments. FIG. 17 is a schematic plan view illustrating the touch panel according
to the sixth embodiment. In the embodiment, the pressure sensor 200 is used as the touch panel
450. As this pressure sensor 200, any one of the pressure sensors described in regard to each of
the above-described embodiments, and a variation thereof are used. In the touch panel 450, the
pressure sensor 200 is mounted on at least one of the inside of the display and the outside of the
display.
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[0130]
For example, the touch panel 450 includes a plurality of first wires 451, a plurality of second
wires 452, a plurality of pressure sensors 200, and a controller 453.
[0131]
In this example, the plurality of first wires 451 are arranged along the Y-axis direction.
Each of the plurality of first wires 451 extends along the X-axis direction. The plurality of second
wires 452 are arranged along the X-axis direction. Each of the plurality of second wires 452
extends along the Y-axis direction.
[0132]
Each of the plurality of pressure sensors 200 is provided at each intersection of the plurality of
first wires 451 and the plurality of second wires 452. One of the pressure sensors 200 is one of
the detection elements 200e for detection. Here, the intersection includes the position where the
first wiring 451 and the second wiring 452 intersect and the area around the position.
[0133]
One end 261 of each of the plurality of pressure sensors 200 is connected to each of the
plurality of first wires 451. The other end 262 of each of the plurality of pressure sensors 200 is
connected to each of the plurality of second wires 452.
[0134]
The control unit 453 is connected to the plurality of first wires 451 and the plurality of second
wires 452. For example, the control unit 453 includes a first wiring circuit 453a connected to the
plurality of first wirings 451, a second wiring circuit 453b connected to the plurality of second
wirings 452, and a first wiring circuit 453a. And a control circuit 455 connected to the second
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wiring circuit 453 b.
[0135]
The pressure sensor 200 is capable of compact and highly sensitive pressure sensing. Therefore,
it is possible to realize a high definition touch panel.
[0136]
The pressure sensor according to each of the above embodiments can be applied to various
pressure sensor devices such as an air pressure sensor or a tire air pressure sensor, in addition to
the above applications.
[0137]
According to the embodiment, a highly sensitive strain sensing element, a pressure sensor, a
microphone, a blood pressure sensor, and a touch panel can be provided.
[0138]
The embodiments of the present invention have been described above with reference to specific
examples.
However, the present invention is not limited to these specific examples.
For example, specific configurations of respective elements such as a strain detection element, a
pressure sensor, a microphone, a substrate included in a blood pressure sensor and a touch
panel, a strain detection element, a first magnetic layer, a second magnetic layer, an intermediate
layer, and a nonmagnetic layer Is included in the scope of the present invention as long as the
present invention can be similarly practiced by suitably selecting from the known range by those
skilled in the art and the same effect can be obtained.
[0139]
Moreover, what combined any two or more elements of each specific example in the technically
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possible range is also included in the scope of the present invention as long as the gist of the
present invention is included.
[0140]
In addition, all strain sensing elements, pressure sensors and microphones that can be
appropriately designed and implemented by those skilled in the art based on the strain sensing
element, pressure sensor, microphone, blood pressure sensor and touch panel described above as
the embodiment of the present invention The blood pressure sensor and the touch panel are also
included in the scope of the present invention as long as the gist of the present invention is
included.
[0141]
Besides, within the scope of the concept of the present invention, those skilled in the art can
conceive of various changes and modifications, and it is understood that the changes and
modifications are also within the scope of the present invention. .
[0142]
While certain embodiments of the present invention have been described, these embodiments
have been presented by way of example only, and are not intended to limit the scope of the
invention.
These novel embodiments can be implemented in various other forms, and various omissions,
substitutions, and modifications can be made without departing from the scope of the invention.
These embodiments and modifications thereof are included in the scope and the gist of the
invention, and are included in the invention described in the claims and the equivalent scope
thereof.
[0143]
DESCRIPTION OF SYMBOLS 10 ... 1st magnetic layer, 10m ... magnetization, 11 ... 1st
magnetization fixed layer, 12 ... 2nd magnetization fixed layer, 13 ... magnetic coupling layer, 20
... 2nd magnetic layer, 20m ... magnetization, 20s ... boundary surface, 30 Intermediate layer 40
Nonmagnetic layer 51 First nonmagnetic layer 52 Nonmagnetic layer 52 100, 100a Strain
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sensing element 200 Pressure sensor 200e Detecting element 201 Support portion 201a ...
Hollow part, 201h ... through hole, 210 ... substrate, 210r ... outer edge, 221 ... first wiring, 222 ...
second wiring, 241 ... base, 242 ... thin film, 261 ... one end, 262 ... the other end, 410 ...
microphone, 420 ... portable information terminal, 421 ... display unit, 430 ... acoustic
microphone, 431 ... printed circuit board, 433 ... cover, 435 ... acoustic hole, 439 ... sound, 440 ...
blood pressure sensor, 4 DESCRIPTION OF SYMBOLS 1 ... Arterial blood vessel, 443 ... Skin, 450
... Touch panel, 451 ... 1st wiring, 452 ... 2nd wiring, 453 ... Control part, 453a ... Circuit for 1st
wiring, 453b ... Circuit for 2nd wiring, 455 ... Control circuit 801: force E1: first electrode E2:
second electrode Hc: coercivity R: electrical resistance ST0: no strain state STc: compression state
STt: tension state a: atomic weight ratio cs Compressive stress, t ... thickness, ts ... tensile stress, y
... atomic weight ratio
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