U.S. patent application number 11/650929 was filed with the patent office on 2007-05-17 for magnetic impedance device, sensor apparatus using the same and method for manufacturing the same.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Kenichi Ao, Hirofumi Funahashi, Norikazu Ohta, Yasutoshi Suzuki, Hideya Yamadera.
Application Number | 20070108970 11/650929 |
Document ID | / |
Family ID | 32303783 |
Filed Date | 2007-05-17 |
United States Patent
Application |
20070108970 |
Kind Code |
A1 |
Ao; Kenichi ; et
al. |
May 17, 2007 |
Magnetic impedance device, sensor apparatus using the same and
method for manufacturing the same
Abstract
A magnetic sensor apparatus includes a semiconductor substrate
and a magnetic impedance device for detecting a magnetic field. The
magnetic impedance device is disposed on the substrate. The
magnetic sensor apparatus has minimum size and is made with low
manufacturing cost. Here, the magnetic impedance device detects a
magnetic field in such a manner that impedance of the device is
changed in accordance with the magnetic filed when an alternating
current is applied to the device and the impedance is measured by
an external electric circuit.
Inventors: |
Ao; Kenichi; (Tokai-city,
JP) ; Suzuki; Yasutoshi; (Okazaki-city, JP) ;
Yamadera; Hideya; (Nagoya-city, JP) ; Ohta;
Norikazu; (Aichi-gun, JP) ; Funahashi; Hirofumi;
(Nagoya-city, JP) |
Correspondence
Address: |
POSZ LAW GROUP, PLC
12040 SOUTH LAKES DRIVE
SUITE 101
RESTON
VA
20191
US
|
Assignee: |
DENSO CORPORATION
1-1, Showa-cho
Kariya-city
JP
448-8661
|
Family ID: |
32303783 |
Appl. No.: |
11/650929 |
Filed: |
January 9, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10717902 |
Nov 21, 2003 |
|
|
|
11650929 |
Jan 9, 2007 |
|
|
|
Current U.S.
Class: |
324/207.25 ;
324/207.13 |
Current CPC
Class: |
H01L 27/22 20130101;
G01P 3/487 20130101; G01R 33/02 20130101; Y10T 428/1193
20150115 |
Class at
Publication: |
324/207.25 ;
324/207.13 |
International
Class: |
G01B 7/30 20060101
G01B007/30; G01R 33/02 20060101 G01R033/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 21, 2002 |
JP |
2002-337416 |
Nov 21, 2002 |
JP |
2002-337417 |
Mar 5, 2003 |
JP |
2003-58899 |
Mar 5, 2003 |
JP |
2003-58900 |
Mar 18, 2003 |
JP |
2003-73900 |
Claims
1-33. (canceled)
34. A rotation sensor apparatus comprising: a rotation body for
providing a periodic change of intensity of magnetic field disposed
around the rotation body in accordance with rotation of the
rotation body; a magnetic sensor having a magnetic impedance device
for detecting the periodic change of the intensity of magnetic
field so as to detect the rotation of the rotation body; and a
separation shield for separating between the rotation body and the
magnetic sensor, wherein the magnetic sensor detects the rotation
of the rotation body through the separation shield.
35. The apparatus according to claim 34, wherein the separation
shield is a casing for covering the rotation body, and wherein the
magnetic sensor detects the rotation of the rotation body disposed
in the casing.
36. The apparatus according to claim 34, wherein the rotation body
is made of a magnetic material or a material including the magnetic
material, and has a gearwheel shape.
37. The apparatus according to claim 36, further comprising:
another magnetic sensor, wherein two magnetic sensors are arranged
in parallel so as to separately by a half of pitch of the rotation
body and symmetrically disposed around a rotation axis of the
rotation body, and wherein two magnetic sensors output signals,
respectively, so that a differential output signal is obtained.
38. The apparatus according to claim 36, wherein the rotation body
is a gear connecting to a crankshaft of an engine of a vehicle, and
wherein the separation shield is an engine block of the
vehicle.
39. The apparatus according to claim 36, wherein the rotation body
is a cam connecting to a camshaft of an engine of a vehicle, and
wherein the separation shield is an engine block of the
vehicle.
40. The apparatus according to claim 34, wherein the rotation body
is a cylindrical magnet having a pair of N and S poles, which is
alternately disposed on circumferential periphery of the
cylindrical magnet.
41. The apparatus to claim 40, further comprising: another magnetic
sensor, wherein two magnetic sensors are arranged in parallel so as
to separate by a half of pitch of the rotation body and
symmetrically disposed around a rotation axis of the rotation body,
and wherein two magnetic sensors output signals, respectively, so
that a differential output signal is obtained.
42. The apparatus according to claim 40, wherein the rotation body
is a magnetized rotor mounted on a rotation shaft of a wheel of a
vehicle, and wherein the separation shield is a wheel hub of the
vehicle.
43. The apparatus according to claim 34, wherein the separation
shield is made of non-magnetic material.
44. The apparatus according to claim 34, wherein the separation
shield is a sensor casing for covering the magnetic sensor, wherein
the sensor casing is made of magnetic material and includes an
opening, which faces the rotation body, and wherein the magnetic
sensor detects the rotation of the rotation body through the
opening of the sensor casing.
45. The apparatus according to claim 44, wherein the sensor casing
is made of a permanent magnet.
46. The apparatus according to claim 45, wherein the sensor casing
has both ends thereof, which open for an outside of the sensor
casing, wherein the sensor casing has a sidewall for providing the
permanent magnet, and wherein the magnet sensor is disposed in the
sensor casing.
47. The apparatus according to claim 44, wherein the rotation body
is made of magnetic material or a material including the magnetic
material, and has a gearwheel shape.
48. The apparatus according to claim 47, wherein the rotation body
is a gear connecting to a crankshaft of an engine of a vehicle.
49. The apparatus according to claim 44, wherein the rotation body
is a cam connecting to a camshaft of an engine of a vehicle, and
wherein the cam is made of a magnetic material or a material
including the magnetic material.
50. The apparatus according to claim 44, wherein the rotation body
is a cylindrical magnet having a pair of N and S poles, which is
alternately disposed on a circumferential periphery of the
cylindrical magnet.
51. The apparatus according to claim 44, wherein the rotation body
is a magnetized rotor mounted on a rotation shaft of a wheel of a
vehicle.
52. The apparatus according to claim 34, wherein the magnetic
impedance device detects a magnetic field in such a manner that
impedance of the device is changed in accordance with the magnetic
field when an alternating current is applied to the device and the
impedance is measured by an external electric circuit, wherein the
magnetic impedance device includes a magnetic layer made of Ni--Fe
series alloy film, wherein the magnetic layer has a length defined
as L1 in an energization direction of the alternating current, a
width defined as L2 in a perpendicular direction perpendicular to
the energization direction, and a thickness of the magnetic layer
define as L3, wherein the ratio of the length and the width and the
thickness is defined as .alpha., i.e., .alpha.=L11/L2, and the
ratio of the width and the thickness is defined as .beta., i.e.,
.beta.=L2/L3, wherein the ratio .alpha. is equal to or larger than
10, and the ratio .beta. is in a range between 1 and 50, and
wherein the width L3 is equal to or larger than 5 .mu.m.
53. The apparatus according to claim 34, wherein the magnetic
impedance device detects a magnetic field in such a manner that
impedance of the device is changed in accordance with the magnetic
field when an alternating current is applied to the device and the
impedance is measured by an external electric circuit, wherein the
magnetic impedance device includes a magnetic layer made of Ni--Fe
series alloy film, wherein the magnetic layer has a length defined
as L1 in an energization direction of the alternating current, a
width defined as L2 in a perpendicular direction perpendicular to
the energization direction, and a thickness of the magnetic layer
defined as L3, and wherein the length L1 is equal to or larger than
100 .mu.m, the thickness L3 is equal to or larger than 0.3
.mu.m.
54. The apparatus according to claim 53, wherein the Ni--Fe series
alloy film has a composition such that a content of Ni in the
Ni--Fe series alloy film is in a range between 65 wt % and 90 wt %,
and/or a content of Fe in the Ni--Fe series alloy film is in a
range between 10 wt % and 35 wt %, wherein the Ni--Fe series alloy
film has a plurality of grains, dimensions of which are equal to or
smaller than 100 nm, and wherein the substrate has a surface
roughness, which is equal to or smaller than 1300 nm.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on Japanese Patent Applications
No. 2002-337416 filed on Nov. 21, 2002, No. 2002-337417 filed on
Nov. 21, 2002, No. 2003-58899 filed on Mar. 5, 2003, No. 2003-58900
filed on Mar. 5, 2003, and No. 2003-73900 filed on Mar. 18, 2003,
the disclosures of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a magnetic impedance
device, a sensor apparatus using the same and a method for
manufacturing the same. The sensor apparatus is suitably used for a
rotation sensor apparatus.
BACKGROUND OF THE INVENTION
[0003] A conventional magnetic impedance device utilizes a magnetic
impedance effect, and is disclosed in Japanese Patent Application
Publication No. H08-75835. The magnetic impedance effect is that
impedance of the device changes in accordance with an outside
stress in a case where the device is energized with an alternating
current (e.g., a high frequency alternating current, the frequency
being higher than 1 MHz). The device includes a magnetic layer,
which is made of amorphous alloy and has a soft magnetic property.
Here, the amorphous alloy has high relative magnetic permeability.
Therefore, a change of the magnetic permeability in the magnetic
layer in accordance with an external magnetic field becomes large,
so that the device has high sensitivity.
[0004] However, the magnetic impedance device with the magnetic
layer made of amorphous alloy has low heat resistance, so that the
sensitivity of the device is much decreased in a case where the
device is processed with heat treatment above almost 400.degree. C.
The reason is as follows. The crystallization temperature of the
magnetic layer made of amorphous alloy is low, i.e., at around
400.degree. C. Therefore, when the device is processed with heat
treatment above almost 400.degree. C., the amorphous alloy is
crystallized, so that the soft magnetic property of the amorphous
alloy disappears. Here, the soft magnetic property of the amorphous
alloy provides high sensitivity magnetic impedance.
[0005] Further, in a case where the magnetic layer is formed of
easily oxidizable material, the magnetic layer is oxidized with
heat treatment, so that the soft magnetic property is deteriorated.
Thus, the sensitivity is decreased.
[0006] Therefore, it is difficult to manufacture the magnetic
impedance device having the magnetic layer made of amorphous alloy
with using a conventional semiconductor processing method. That is
because the conventional method usually includes a step of heat
treatment above almost 400.degree. C. Accordingly, it is difficult
to minimize the device with using the conventional method so that
the device is integrated with another circuit such as a sensor
output signal processor.
[0007] Further, when the device is annealed, i.e., processed with
heat treatment, a stress is generated in a substrate since thermal
expansion of the substrate is different from that of the device.
Here, the device is mounted on the substrate. Therefore, in some
cases, the device may be removed from the substrate. To prevent
from being removed, deposition condition for depositing a magnetic
layer composing a magnetic impedance device is changed, or a film
quality of the magnetic layer is changed. This is disclosed in
Japanese Patent Application Publication No. 2001-228229. However,
this device is necessitated to form with limited manufacturing
method and to have a limited construction.
[0008] Moreover, since a magnetic impedance device having high
sensitivity is available for various sensor systems, minimization
and low manufacturing cost are much required. For example, a
magnetic impedance head module according to a prior art having a
thin film magnetic impedance device is disclosed in Japanese Patent
Application Publications No. 2001-318131. The head module includes
the thin film magnetic impedance device, an electric power supply
circuit for energizing the device with a high frequency alternating
current, and a detection circuit for detecting a impedance change,
which are provided with a discrete circuit. And each discrete
circuit is combined with a hybrid IC. Therefore, minimization and
reduction of manufacturing cost of the head module are limited.
[0009] Further, a magnetic impedance device is suitably used for a
sensor apparatus mounted on an automotive vehicle, the sensor
apparatus detecting, for example, rotation of a rotational body. A
rotation sensor apparatus according to a prior art is disclosed in
Japanese Patent Applications No. H08-304432 (i.e., U.S. Pat. No.
5,841,276) and No. 2000-46513. These sensor apparatuses are mounted
on an engine of a vehicle or on a wheel hub, so that the sensor
apparatuses detect rotation of crankshaft of the engine or rotation
of wheel of the vehicle, respectively. In each case, it is required
to minimize the sensor apparatus so as to improve mounting
performance of the apparatus and to increase design freedom of an
engine and so on.
[0010] Further, the magnetic impedance device mounted on the
vehicle is required to be protected from outside disturbance of
magnetic field with using a simple construction of the device. That
is because the magnetic impedance device has high sensitivity so
that the device is easily affected by the outside disturbance of
magnetic field. Therefore, a current sensor having a magnetic
impedance device according to a prior art, for example, includes a
magnetic shield and a pair of reverse wound coil for reducing the
outside disturbance. This type of current sensor is disclosed in
Japanese Patent Application Publication No. 2001-116773. However,
this current sensor has a complicated construction so that a
manufacturing cost is increased.
SUMMARY OF THE INVENTION
[0011] In view of the above problem, it is an object of the present
invention to provide a sensor apparatus having a magnetic impedance
device, which has minimum size and is made with low manufacturing
cost. Specifically, the magnetic impedance device has high heat
resistance. Namely, magnetic property of the device, i.e., sensor
sensitivity is not decreased even when the device is processed with
heat treatment. More specifically, the sensor apparatus is suitably
used for a rotation sensor having high mounting performance and
high design freedom.
[0012] It is another object of the present invention to provide a
method for manufacturing the above sensor apparatus with a magnetic
impedance device, which has minimum size and is made with low
manufacturing cost.
[0013] It is further another object of the present invention to
provide a sensor apparatus having a magnetic impedance device,
which has high resistance against an outside disturbance of
magnetic field. Specifically, the sensor apparatus is suitably used
for a rotation sensor mounted, for example, on an automotive
vehicle.
[0014] A magnetic sensor apparatus includes a semiconductor
substrate and a magnetic impedance device for detecting a magnetic
field. The magnetic impedance device is disposed on the substrate.
This magnetic sensor apparatus has minimum size and is made with
low manufacturing cost.
[0015] Further, a method for manufacturing the above magnetic
sensor apparatus includes the steps of forming a stress relaxation
layer on the substrate, and forming the magnetic impedance device
on the stress relaxation layer. The stress relaxation layer reduces
a stress generated in the substrate in a case where the apparatus
is processed in a heat treatment. This method provides the magnetic
sensor apparatus having minimum size and being made with low
manufacturing cost. Further, the reliability of the apparatus
concerned with a mechanical strength is improved.
[0016] Preferably, in the above apparatus, the magnetic impedance
device detects a magnetic field in such a manner that impedance of
the device is changed in accordance with the magnetic filed when an
alternating current is applied to the device and the impedance is
measured by an external electric circuit. The magnetic impedance
device includes a magnetic layer made of Ni--Fe series alloy film.
The magnetic layer has a length defined as L1 in an energization
direction of the alternating current, a width defined as L2 in a
perpendicular direction perpendicular to the energization
direction, and a thickness of the magnetic layer defined as L3. The
ratio of the length and the width is defined as .alpha., i.e.,
.alpha.=L1/L2, and the ratio of the width and the thickness is
defined as .beta., i.e., .beta.=L2/L3. The ratio .alpha. is equal
to or larger than 10, and the ratio .beta. is in a range between 1
and 50. The thickness L3 is equal to or larger than 5 .mu.m.
[0017] In the above apparatus, the sensor sensitivity is not
decreased even when the apparatus is processed with heat treatment.
Thus, the apparatus has high heat resistance. Further, the
apparatus has high sensor sensitivity.
[0018] Preferably, the apparatus further includes a protection
layer for covering the magnetic layer. The protection layer is made
of electrically insulation material. More preferably, the
protection layer has a compression stress as an internal stress,
the compression stress being equal to or smaller than 500 MPa. More
preferably, the protection layer has a tensile stress as an
internal stress, the tensile stress being equal to or smaller than
100 MPa. In the above apparatus, the sensor sensitivity is not
decreased even when the apparatus is processed with heat treatment.
Thus, the apparatus has high heat resistance. Specifically, the
magnetic layer of the apparatus is not substantially oxidized even
when the apparatus is annealed. Further, the apparatus has high
sensor sensitivity.
[0019] Further, a rotation sensor apparatus includes a rotation
body for providing a periodic change of intensity of magnetic field
disposed around the rotation body in accordance with rotation of
the rotation body, a magnetic sensor having a magnetic impedance
device for detecting the periodic change of the intensity of
magnetic field so as to detect the rotation of the rotation body,
and a separation shield for separating between the rotation body
and the magnetic sensor. The magnetic sensor detects the rotation
of the rotation body through the separation shield.
[0020] In the above rotation sensor apparatus, the magnetic sensor
having high sensor sensitivity can detect the rotation of the
rotation body, even though the separation shield is disposed
between the magnetic sensor and the rotation body. Therefore, the
magnetic sensor can be disposed outside the separation shield
without drilling an opening for mounting the magnetic sensor. Thus,
the apparatus has high mounting performance for mounting the
magnetic sensor on the separation shield and high design freedom of
the separation shield.
[0021] Preferably, the separation shield is a casing for covering
the rotation body. The magnetic sensor detects the rotation of the
rotation body-disposed in the casing.
[0022] Preferably, the rotation sensor apparatus further includes
another magnetic sensor. The two magnetic sensors are arranged in
parallel so as to separate by a half of pitch of the rotation body
and symmetrically disposed around a rotation axis of the rotation
body. The two magnetic sensors output signals, respectively, so
that a differential output signal is obtained. In this case, the
apparatus detects a differential output generated from both
magnetic sensors. This differential output cancels a constant
component of the geomagnetic field disposed in each magnetic
sensor. Therefore, the apparatus detects the periodic change of
magnetic field much accurately. Namely, the apparatus detects the
rotation much accurately.
[0023] Preferably, the separation shield is a sensor casing for
covering the magnetic sensor. The sensor casing is made of magnetic
material and includes an opening, which faces the rotation body.
The magnetic sensor detects the rotation of the rotation body
through the opening of the sensor casing. In this case, the
apparatus has a simple construction in such a manner that the
sensor casing having the small opening covers the magnetic sensor
so that the influence of disturbance of an external magnetic field
around the magnetic sensor is reduced. Therefore, the manufacturing
cost of the apparatus is reduced. Further, the apparatus having the
magnetic impedance device, which has high resistance against an
outside disturbance of magnetic field.
BRIEF-DESCRIPTION OF THE DRAWINGS
[0024] The above and other objects, features and advantages of the
present invention will become more apparent from the following
detailed description made with reference to the accompanying
drawings. In the drawings:
[0025] FIG. 1 is a plan view showing a magnetic impedance device
according to a first embodiment of the present invention;
[0026] FIG. 2 is a cross-sectional view showing the device taken
along line II-II in FIG. 1;
[0027] FIG. 3 is a cross-sectional view showing the device taken
along line III-III in FIG. 1;
[0028] FIGS. 4A to 4C are cross-sectional views of the device
explaining a manufacturing method of the device according to the
first embodiment;
[0029] FIG. 5 is a graph showing a relationship between an external
magnetic field Hext and impedance Z of the device according to the
first embodiment;
[0030] FIG. 6 is a graph showing a relationship between temperature
T and temperature drift of impedance Z-Zat25.degree.
C./Zat25.degree. C. at zero magnetic field of the device according
to the first embodiment;
[0031] FIG. 7 is a graph showing a relationship between temperature
T and temperature dependence of sensor sensitivity
.DELTA.(Z-Zat25.degree. C./Zat25.degree. C.)/(Z-Zat25.degree.
C./Zat25.degree. C.) of the device according to the first
embodiment;
[0032] FIG. 8 is a table showing coefficients of temperature
dependence of the magnetic impedance .DELTA.Zo/.DELTA.T at zero
magnetic field and of the sensor sensitivity
.DELTA.(.DELTA.Z/Zo)/.DELTA.T in different devices, according to
the first embodiment;
[0033] FIG. 9 is a table showing the ratio of impedance change
.DELTA.Z/Zo in different devices, according to the first
embodiment;
[0034] FIG. 10 is a graph showing a relationship between a length
L1 of the magnetic layer and a ratio of impedance change
.DELTA.Z/Zo in the devices according to the first embodiment;
[0035] FIG. 11 is a table showing the ratio of impedance change
.DELTA.Z/Zo in different devices, according to the first
embodiment;
[0036] FIG. 12 is a graph showing a relationship between a width L2
of the magnetic layer and a ratio of impedance change .DELTA.Z/Zo
in the devices according to the first embodiment;
[0037] FIG. 13 is a table showing the ratio of impedance change
.DELTA.Z/Zo in different devices, according to the first
embodiment;
[0038] FIG. 14 is a graph showing a relationship between a
thickness L3 of the magnetic layer and a ratio of impedance change
.DELTA.Z/Zo in the devices according to the first embodiment;
[0039] FIG. 15 is a table showing the ratio of impedance change
.DELTA.Z/Zo in different devices, according to the first
embodiment;
[0040] FIG. 16 is a graph showing a relationship between a grain
size of the magnetic layer and a ratio of impedance change
.DELTA.Z/Zo in the devices according to the first embodiment;
[0041] FIG. 17 is a table showing the ratio of impedance change in
different devices, according to the first embodiment;
[0042] FIG. 18 is a graph showing a relationship between a surface
roughness of the substrate and a ratio of impedance change
.DELTA.Z/Zo in the devices according to the first embodiment;
[0043] FIG. 19 is a plan view showing a magnetic impedance device
according to a second embodiment of the present invention;
[0044] FIG. 20 is a cross-sectional view showing the device taken
along line XX-XX in FIG. 19;
[0045] FIG. 21 is a table showing the ratio of impedance change
.DELTA.Z/Zo in different devices, according to the second
embodiment;
[0046] FIG. 22 is a graph showing a relationship between an
external magnetic field Hext and impedance Z of the device
according to the second embodiment;
[0047] FIG. 23 is a graph showing a relationship between an
internal stress .sigma. of a protection layer and a ratio of
impedance change .DELTA.Z/Zo of the devices according to the second
embodiment;
[0048] FIG. 24 is a graph showing a relationship between an
internal stress .sigma. of a protection layer and a ratio of
impedance change .DELTA.Z/Zo of the devices according to the second
embodiment;
[0049] FIG. 25 is a cross-sectional view showing a magnetic sensor
apparatus according to a third embodiment of the present
invention;
[0050] FIG. 26 is an enlarged plan view showing a magnetic
impedance device of the apparatus according to the third
embodiment;
[0051] FIG. 27 is a schematic diagram showing an electric circuit
of the apparatus according to the third embodiment;
[0052] FIG. 28 is a cross-sectional view showing a magnetic sensor
apparatus according to a fourth embodiment of the present
invention;
[0053] FIG. 29 is a cross-sectional view showing a magnetic sensor
apparatus according to a fifth embodiment of the present
invention;
[0054] FIG. 30 is a cross-sectional view showing a magnetic sensor
apparatus according to a sixth embodiment of the present
invention;
[0055] FIG. 31 is a cross-sectional view showing part of a magnetic
sensor apparatus according to a seventh embodiment of the present
invention;
[0056] FIG. 32 is a cross-sectional view showing a magnetic sensor
apparatus according to an eighth embodiment of the present
invention;
[0057] FIG. 33 is a cross-sectional view showing a magnetic sensor
apparatus according to a ninth embodiment of the present
invention;
[0058] FIG. 34 is a schematic cross-sectional view showing a
rotation sensor apparatus according to a tenth embodiment of the
present invention;
[0059] FIGS. 35A to 35C are schematic cross-sectional views showing
part of the rotation sensor apparatus according to the tenth
embodiment;
[0060] FIG. 36 is a schematic cross-sectional view showing another
rotation sensor apparatus according to the tenth embodiment;
[0061] FIG. 37 is a schematic cross-sectional view showing a
rotation sensor apparatus according to an eleventh embodiment of
the present invention;
[0062] FIGS. 38A to 38C are schematic cross-sectional views showing
a rotation sensor apparatus according to a twelfth embodiment of
the present invention;
[0063] FIG. 39 is a schematic cross-sectional view showing another
rotation sensor apparatus according to the twelfth embodiment;
and
[0064] FIGS. 40A and 40B are schematic cross-sectional views
showing a rotation sensor apparatus according to a thirteenth
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0065] The inventors examine a magnetic thin film made of Ni--Fe
series alloy as a magnetic material composing a magnetic layer in a
magnetic impedance device, which has high heat resistance so that
sensitivity of the device is not decreased even when the device is
processed with heat treatment above 400.degree. C.
[0066] A magnetic impedance device according to a first embodiment
utilizes magnetic impedance effect. The magnetic impedance effect
is that impedance of the device changes in accordance with an
external magnetic field when the device is energized with an
alternating current. The device includes a magnetic layer made of
Ni--Fe series alloy film. Here, Ni--Fe series alloy film has high
Currie temperature and is made of polycrystalline. Accordingly,
magnetic property of the magnetic layer made of Ni--Fe series alloy
film does not change after the heat treatment above 400.degree. C.
For example, sensor sensitivity of the device is not decreased
after the heat treatment. Therefore, the device has high heat
resistance.
[0067] A magnetic impedance device 1 according to a first
embodiment is shown FIGS. 1-3. As shown in FIGS. 1 and 2, the
device 1 includes a substrate 22, an insulation layer 24, a
magnetic layer 26, and a pair of electrode pads 28a, 28b. The
electrode pads 28a, 28b connect to an alternating current supply
30. The alternating current supply 30 can control a frequency of
alternating current outputting from the supply 30. In FIG. 1, an
external magnetic field Hext is applied to the device 1, and the
alternating current outputted from the supply 30 also flows through
the device 1. An energization direction of the alternating current
outputted from the supply 30 is parallel to the external magnetic
field Hext.
[0068] The substrate 22 can be made of any material as long as the
insulation layer 24, the magnetic layer 26 and the like can be
formed thereon. For example, the substrate is made of silicon
wafer, glass, metal, and so on. In a case where the substrate 22 is
made of conducting material or semiconducting material such as
metal or silicon, it is preferred that the insulation layer 24 is
disposed between the substrate 22 and the magnetic layer 26 so that
the magnetic layer 26 is insulated from the substrate 22
electrically. In a case where the substrate 22 is made of
insulation material such as glass, the magnetic layer 26 can be
formed on the substrate 22 directly without the insulation layer
24. Further, other material such as a conducting layer other than
the insulation layer 24 may be formed between the substrate 22 and
the magnetic layer 26 in some case. Preferably, surface roughness
of the substrate 22 is lower than 1 .mu.m. In this case, concavity
and convexity of the surface of the substrate 22 is small, and the
magnetic layer 26 is disposed on the substrate 22 directly or
disposed on the substrate 22 through the insulation layer 24 and
the like, so that the magnetic layer 26 can be magnetized easily.
Specifically, the magnetic layer 26 has an excellent soft magnetic
property. Further, the insulation layer 24 can be made of any
insulation material as long as the insulation layer 24 insulates
between the substrate 22 and the magnetic layer 26. For example,
the insulation layer 24 is made of oxide silicon, nitride silicon,
and the like.
[0069] The magnetic layer 26 is formed on the insulation layer 24.
The magnetic layer 26 is made of Ni--Fe series alloy film, which is
a thin film and made of ferromagnetic material having a soft
magnetic property. The Ni--Fe series alloy film is made of Ni and
Fe only, i.e., Ni--Fe alloy. However, the magnetic layer 26 can be
made of Fe--Co alloy and the like. Preferably, composition of
Ni--Fe series alloy composing the magnetic layer 26 is 65-90 wt %
of Ni and/or 15-35 wt % of Fe. In a case where the Ni--Fe series
alloy is made of Ni and Fe only, it is preferred that the
composition is 65-90 wt % of Ni and/or 15-35 wt % of Fe. In this
case, the sensor sensitivity is improved. More preferably,
composition of Ni--Fe series alloy composing the magnetic layer 26
is 77-85 wt % of Ni and/or 15-23 wt % of Fe. In a case where the
Ni--Fe series alloy is made of Ni and Fe only, it is preferred that
the composition is 77-85 wt % of Ni and/or 15-23 wt % of Fe. In the
above cases, the temperature dependence of magnetic permeability of
the magnetic layer 26 becomes small, so that the magnetic impedance
device 1 has high sensor sensitivity and low temperature dependence
of the sensitivity.
[0070] As shown in FIG. 3, the cross-section of the magnetic layer
26 has a square shape, the cross-section being perpendicular to the
energization direction. The cross-section of the magnetic layer 26
has a latitudinal side 26a and a longitudinal side 26b. An angle
.theta. between the latitudinal side 26a and the longitudinal side
26b is preferably in a range between 60.degree. and 120.degree.. In
this case, wedge-shaped magnetic domain is prevented from
generating. Therefore, a hysteresis loop in the magnetic impedance
characteristic of the magnetic layer 26 is also prevented from
generating. More preferably, the angle .theta. is in a range
between 85.degree. and 95.degree..
[0071] Grain size of a single crystalline particle of the Ni--Fe
series alloy composing the magnetic layer 26 is preferably in a
range between 1 nm and 1 .mu.m. If the grain size is smaller than 1
nm, the grain size becomes larger when the device is performed with
heat treatment. Therefore, the soft magnetic property is easily
deteriorated. If the grain size is larger than 1 .mu.m, it is
difficult to magnetize the magnetic layer 26 so as to have the soft
magnetic property. Moreover, it is preferred that the magnetic
layer 26 has an axis of easy magnetization, which is almost
perpendicular to or parallel to the energization direction of the
alternating current from the alternating current supply 30. In this
case, the detection sensitivity for detecting the external magnetic
field is improved. Further, it is preferred that the magnetic
properties of the magnetic layer 26 are such that the coercive
force is lower than 10 Oe and the relative magnetic permeability is
higher than 500.
[0072] As shown in FIGS. 1 and 2, the magnetic layer 26 has a
length L1 in the energization direction of the alternating current,
a width L2 perpendicular to the energization direction, and a
thickness L3 of the magnetic layer 26. Assuming that a ratio
between the length L1 and the width L2 is defined as .alpha., i.e.,
.alpha.=L1/L2, and a ratio between the width L2 and the thickness
L3 is defined as .beta., i.e., .beta.=L2/L3, the ratio .alpha. is
equal to or larger than 10 and the ratio .beta. is in a range
between 1 and 50 (i.e., .alpha..gtoreq.10 and 1
.ltoreq..beta..ltoreq.50). Further, the thickness L3 is equal to or
larger than 5 .mu.m. In this case, the magnetic impedance device
has high sensor sensitivity. That is because the magnetic domain of
the magnetic layer 26 can be controlled accurately so that the
magnetic permeability of the magnetic layer 26 is largely changed
in accordance with the external magnetic field in a case where the
magnetic layer 26 has the above construction.
[0073] More preferably, when the ration .alpha. is equal to or
larger than 50, the sensor sensitivity is much improved. Further,
when the ratio .beta. is in a range between 1 and 30, the sensor
sensitivity is much improved. Specifically, the ratio .beta. is in
a range between 1 and 5, the sensitivity is further improved. The
above reasons are described later.
[0074] The electrode pads 28a, 28b are formed on the insulation
layer 24. Each electrode pad 28a, 28b covers one end or the other
end of the magnetic layer 26 in the longitudinal direction. The
electrode pad 18a, 28b can be made of any material as long as the
material works as an electrode. For example, the material is
aluminum, copper and their alloy. It is preferred that the specific
resistance of the electrode pad 28a, 28b is equal to or lower than
10 .mu..OMEGA.cm.
[0075] Next, the manufacturing method of the magnetic impedance
device 1 is describes as follows. At first, as shown in FIGS. 4A to
4C, the substrate 22 is prepared. Then, the insulation layer 24 is
formed on the substrate 22. When the substrate 22 is made of
silicon, the surface of the silicon substrate 22 is oxidized with
using thermal oxidation method so that the insulation layer 24 made
of silicon oxides is formed. Further, the insulation layer 24 can
be formed with using chemical vapor deposition method, sputtering
method, or the like, and is made of silicon oxides, silicon
nitrides. There is no limitation of the deposition method for
forming the insulation layer 24.
[0076] Next, the Ni--Fe series alloy film is formed on the
insulation layer 24. The Ni--Fe series alloy film can be formed
with using sputtering method, vapor deposition, or coating method.
There is no limitation of the deposition method for forming the
Ni--Fe series alloy. The Ni--Fe series alloy film is patterned into
a predetermined shape with using photo etching method, so that the
magnetic layer 26 is formed, as shown in FIG. 4C. In this case,
preferably a single axial anisotropic magnetic field is applied to
the magnetic layer 26 in the energization direction of the
alternating current, i.e., the longitudinal direction of the
magnetic layer 26 during the deposition under magnetic filed or
heat treatment under magnetic field, so that the magnetic layer 26
has the axis of easy magnetization along with the energization
direction.
[0077] Next, a preliminary layer for an electrode is formed on both
the magnetic layer 26 and the insulation layer 24. The preliminary
layer can be formed with using the sputtering method, vapor
deposition, or coating method. There is no limitation of the
deposition method for forming the preliminary layer. The
preliminary layer is patterned into a predetermined shape with
using photo etching method, so that the electrode pads 28a, 28b are
formed so as to cover both ends of the magnetic layer 26, as shown
in FIGS. 1 and 2. Then, the electrodes 28a, 28b is connected with
bonding wires. Thus, the magnetic impedance device 1 is
completed.
[0078] Specifically, the detailed manufacturing method is described
as follows. A magnetic impedance device S11 (that is shown in FIG.
8) according to this embodiment is manufactured. As shown in FIG.
4, the silicon substrate 22 is prepared. The insulation layer 24
made of silicon oxides having thickness of 1 .mu.m is formed on the
substrate 22 with using the thermal oxidation method.
[0079] Next, a Ni.sub.81Fe.sub.19 Alloy film having thickness of 2
.mu.m is formed on the insulation layer 24 with using the
sputtering method under magnetic field. The Ni.sub.81Fe.sub.19
Alloy film is patterned into a predetermined shape with using the
photo etching method, so that the magnetic layer 26 is formed.
Specifically, the magnetic layer 26 has a length of 2 mm and a
width of 10 .mu.m. At this time, the single axial anisotropic
magnetic field is applied to the magnetic layer 26 in the
energization direction of the alternating current, i.e., the
longitudinal direction of the magnetic layer 26 during the
deposition of sputtering under magnetic filed, so that the magnetic
layer 26 has the axis of easy magnetization along with the
energization direction.
[0080] Next, an aluminum layer having thickness of 1 .mu.m is
formed on both the insulation layer 24 and the magnetic layer 26.
The aluminum layer is patterned into a predetermined shape with
using the photo etching method so that the electrode pads 28a, 28b
are formed so as to cover both ends of the magnetic layer 26, as
shown in FIGS. 1 and 2. Specifically, the area of each electrode
pad 28a, 28b disposed on the upper surface of the electrode pad
28a, 28b is a square of 200 .mu.m.times.200 .mu.m. On the
assumption that the device S11 is processed in semiconductor
process, the device S11 is processed in vacuum under 400.degree. C.
during 30 minutes. After that, each electrode pad 28a, 28b is
connected with a bonding wire. Thus, the device S11 is
completed.
[0081] The device S11 is evaluated with using a coil and an
impedance analyzer. Here, the coil provides an external magnetic
field Hext applied to the device S11, and the impedance analyzer
detects a high frequency impedance z generated at both ends of the
magnetic layer 26 of the device S11. The external magnetic field
Hext is parallel to the energization direction of the high
frequency alternating current generated from the alternating
current supply 30. The external magnetic field Hext is corrected
with a gauss meter disposed on the substrate 22. The impedance Z is
measured in case of the frequency of the high frequency current
supply 30 at 100 MHz. The magnetic impedance property of the device
S11 is evaluated with a ratio of impedance change .DELTA.Z/Zo.
Here, Zo is impedance of the device S11 in a case where the
external magnetic field Hext is zero. .DELTA.Z is a difference
between impedance Z in a case where the external magnetic field
Hext is 100 Oe and the impedance Zo at zero, i.e., .DELTA.Z=Z-Zo.
The temperature dependence of the magnetic impedance of the device
S11 is measured at -40.degree. C. and +85.degree. C. in a
temperature controlled chamber, so that a coefficient of
temperature dependence of magnetic impedance .DELTA.Zo/.DELTA.T at
zero magnetic field and a coefficient of temperature dependence of
sensor sensitivity .DELTA.(.DELTA.Z/Zo)/.DELTA.T are calculated.
The coefficient of temperature dependence of magnetic impedance
.DELTA.Zo/.DELTA.T at zero magnetic field is a coefficient of
temperature dependence of the impedance Z in case of the external
magnetic field at zero. The coefficient of temperature dependence
of sensor sensitivity .DELTA.(.DELTA.Z/Zo)/.DELTA.T is a
coefficient of temperature dependence of the ratio of impedance
change .DELTA.Z/Zo.
[0082] FIG. 5 is a graph of magnetic impedance property of the
device S11 showing an impedance change in accordance with the
external magnetic field Hext. In case of the device S11, the
impedance of the device S11 is reduced in accordance with
increasing or decreasing the external magnetic field Hext. As shown
in FIG. 5, the ration of impedance change .DELTA.Z/Zo, which
corresponds to the sensor sensitivity, is about 30%.
[0083] FIG. 6 shows a graph showing a relationship between
temperature T and an impedance drift .DELTA.Z/Z at zero magnetic
field, i.e., Z-Zat25.degree. C./Zat25.degree. C., of the device
S11. The coefficient of temperature dependence of magnetic
impedance .DELTA.Zo/.DELTA.T at zero magnetic field is calculated
to be 723 ppm/.degree. C. from a slope of a line of the
relationship between temperature T and the impedance drift
.DELTA.Z/Z.
[0084] FIG. 7 shows a graph showing a relationship between
temperature T and a sensor sensitivity drift .DELTA. .function. (
.DELTA.Z Z ) / ( .DELTA. .times. .times. Z Z ) , ##EQU1## i.e.,
.DELTA.(Z-Zat25.degree. C./Zat25.degree. C.)/(Z-Zat25.degree.
C./Zat25.degree. C.) of the device S11. The coefficient of
temperature dependence of sensor sensitivity
.DELTA.(.DELTA.Z/Zo)/.DELTA.T is calculated to be -443 ppm/.degree.
C. from a slope of a line of the relationship between temperature T
and the sensor sensitivity drift
.DELTA.(.DELTA.Z/Z)/(.DELTA.Z/Z).
[0085] In general, it is required that both of the coefficient of
temperature dependence of sensor sensitivity
.DELTA.(.DELTA.Z/Zo)/.DELTA.T and the coefficient of temperature
dependence of magnetic impedance .DELTA.Zo/.DELTA.T at zero
magnetic field are in a range between -1000 ppm.degree. C. to +1000
ppm/.degree. C. Thus, both of the coefficients
.DELTA.(.DELTA.Z/Zo)/.DELTA.T, .DELTA.Zo/.DELTA.T are preferably in
a range between -1000 ppm/.degree. C. to +1000 ppm/.degree. C.
Here, when the Ni--Fe alloy film has a composition of 77-85 wt % of
Ni and/or 15-23 wt % of Fe, this requirement of the coefficients
.DELTA.(.DELTA.Z/Zo)/.DELTA.T, .DELTA.Zo/.DELTA.T are
satisfied.
[0086] Both of the coefficients .DELTA.(.DELTA.Z/Zo)/.DELTA.T,
.DELTA.Zo/.DELTA.T of various devices S11-S18 are measured. As
shown in FIG. 8, a device S12 has a different thickness of the
magnetic layer 26, which is different from that of the device S11.
Each device S13-S16 has the same construction as the device S11,
and different composition of Ni and Fe, which is different from
that of the device S11. Each device S17, S18 has the same
construction as the device S11, and has a various magnetic layer 26
made of different materials, which is different from those of the
device S11, specifically, the magnetic layer 26 of the device S17,
S18 is made of amorphous alloy.
[0087] As shown in FIG. 8, each device S11-S14 has a high sensor
sensitivity, i.e., high ratio of impedance change .DELTA.Z/Zo that
is higher than 20%, and low coefficients
.DELTA.(.DELTA.Z/Zo)/.DELTA.T, .DELTA.Zo/.DELTA.T, i.e., low
coefficients of temperature dependence of sensor sensitivity
.DELTA.(.DELTA.Z/Zo)/.DELTA.T and of magnetic impedance
.DELTA.Zo/.DELTA.T at zero magnetic field that are in a range
between -1000 ppm/.degree. C. and +1000 ppm/.degree. C. On the
other hand, the devices S15, S16 have the high sensor sensitivity
that is higher than 20%, and the high coefficients
.DELTA.(.DELTA.Z/Zo)/.DELTA.T, .DELTA.Zo/.DELTA.T that are disposed
out of range between -1000 ppm/.degree. C. and +1000 ppm/.degree.
C. That is because the devices S11-S14 have the magnetic layer 26
made of the Ni--Fe alloy film having a composition, which is
disposed in a certain range of the low temperature dependence of
the relative magnetic permeability of the magnetic layer 26.
However, the devices S15, S16 have the magnetic layer 26 made of
the Ni--Fe alloy film having a composition, which is disposed in a
certain range of the high temperature dependence of the relative
magnetic permeability of the magnetic layer 26.
[0088] Further, the devices S17, S18 have much small sensor
sensitivity, which is much smaller than that of the devices
S11-S16. That is because the devices S17, S18 have the magnetic
layer 26 made of amorphous alloy, so that the magnetic layer 26 is
crystallized in the heat treatment process performed at 400.degree.
C. Therefore, the soft magnetic property of the magnetic layer 26
is almost disappeared. The soft magnetic property provides the
change of magnetic permeability in accordance with the external
magnetic field.
[0089] FIG. 9 shows the ratio of impedance change .DELTA.Z/Zo of
various devices S21-S25, each of which has the magnetic layer 26
made of the same composition of Ni and Fe as that of the device S11
(i.e., Ni.sub.81Fe.sub.19). Each device S21-S25 has the magnetic
layer 26 having a thickness L3 of 2 .mu.m, a width L2 of 10 .mu.m,
and a different length L1. FIG. 9 also shows the ratio .alpha.
(i.e., .alpha.=L1/L2) and the ratio .beta. (i.e., .beta.=L2/L3).
FIG. 10 is a graph showing a relationship between the length L1 and
the ratio of impedance change .DELTA.Z/Zo of the various devices
S21-S25.
[0090] As shown in FIGS. 9 and 10, as the length L1 of the magnetic
layer 26 becomes longer, the ratio of impedance change .DELTA.Z/Zo
becomes large. In the above devices S21-S25, the ratio .beta. is 5.
When the ratio .alpha. is equal to or larger than 10, i.e., the
length L1 is equal to or longer than 100 .mu.m, the ratio of
impedance change .DELTA.Z/Zo is larger than 10%. Further, when the
ratio .alpha. is equal to or larger than 50, i.e., the length L1 is
equal to or longer than 500 .mu.m, the ratio of impedance change
.DELTA.Z/Zo is larger than 20%. Furthermore, when the ratio .alpha.
is equal to or larger than 200, i.e., the length L1 is equal to or
longer than 2000 .mu.m, the ratio of impedance change .DELTA.Z/Zo
is larger than 30%. Here, it is preferred that the ratio of
impedance change .DELTA.Z/Zo becomes larger.
[0091] FIG. 11 shows the ratio of impedance change .DELTA.Z/Zo of
various devices S31-S35, each of which has the magnetic layer 26
made of the same composition of Ni and Fe as that of the device S11
(i.e., Ni.sub.81Fe.sub.19). Each device S31-S35 has the magnetic
layer 26 having a thickness L3 of 2 .mu.m, a length L1 of 2000
.mu.m, and a different width L2. FIG. 11 also shows the ratio
.alpha. (i.e., .alpha.=L1/L2) and the ratio .beta. (i.e.,
.beta.=L2/L3). FIG. 12 is a graph showing a relationship between
the width L2 and the ratio of impedance change .DELTA.Z/Zo of the
various devices S31-S35.
[0092] As shown in FIGS. 11 and 12, in a case where the width L2 is
longer than 10 .mu.m, as the width L2 of the magnetic layer 26
becomes longer, the ratio of impedance change .DELTA.Z/Zo becomes
small. In a case where the width L2 is shorter than 10 .mu.m, as
the width L2 of the magnetic layer 26 becomes shorter, the ratio of
impedance change .DELTA.Z/Zo becomes small rapidly. When the ratio
.alpha. is in a range between 20 and 400 and the ratio .beta. is in
a range between 1 and 5, i.e., the width L2 is in a range between 5
.mu.m and 100 .mu.m, the ratio of impedance change .DELTA.Z/Zo is
larger than 10%. Further, when the ratio .alpha. is in a range
between 33.3 and 333.3 and the ratio .beta. is in a range between
1.2 and 30, i.e., the width L2 is in a range between 6 .mu.m and 60
.mu.m, the ratio of impedance change .DELTA.Z/Zo is larger than
20%. Furthermore, when the ratio .alpha. is in a range between
166.7 and 250 and the ratio .beta. is in a range between 1.6 and
2.4, i.e., the width L2 is in a range between 8 .mu.m and 12 .mu.m,
the ratio of impedance change .DELTA.Z/Zo is larger than 30%. Here,
it is preferred that the ratio of impedance change .DELTA.Z/Zo
becomes larger.
[0093] FIG. 13 shows the ratio of impedance change .DELTA.Z/Zo of
various devices S41-S46, each of which has the magnetic layer 26
made of the same composition of Ni and Fe as that of the device S11
(i.e., Ni.sub.81Fe.sub.19). Each device S41-S46 has the magnetic
layer 26 having a width L2 of 10 .mu.m, a length L1 of 2000 .mu.m,
and a different thickness L3. FIG. 13 also shows the ratio .alpha.
(i.e., .alpha.=L1/L2) and the ratio .beta. (i.e., .beta.=L2/L3).
FIG. 14 is a graph showing a relationship between the thickness L3
and the ratio of impedance change .DELTA.Z/Zo of the various
devices S41-S46.
[0094] As shown in FIGS. 13 and 14, as the thickness L3 of the
magnetic layer 26 becomes thicker, the ratio of impedance change
.DELTA.Z/Zo becomes large. Here, the ratio .alpha. is 200. When the
ratio .beta. is equal to or smaller than 33, i.e., the thickness L3
is equal to or larger than 0.3 .mu.m, the ratio of impedance change
.DELTA.Z/Zo is larger than 10%. Further, when the ratio .beta. is
equal to or smaller than 14, i.e., the thickness L3 is equal to or
larger than 0.7 .mu.m, the ratio of impedance change .DELTA.Z/Zo is
larger than 20%. Furthermore, when the ratio .beta. is equal to or
smaller than 5, i.e., the thickness L3 is equal to or larger than 2
.mu.m, the ratio of impedance change .DELTA.Z/Zo is larger than
30%.
[0095] In the above devices S11-S18, S21-S25, S31-S35, S41-S46
shown in FIGS. 8 to 14, it is preferred that the length L1, the
width 12 and the thickness L3 have the following values.
[0096] Preferably, referring to the devices S22, S23, when the
length L1 is equal to or longer than 200 .mu.m, the width L2 is in
a range between 7 .mu.m and 20 .mu.m, and the thickness L3 is equal
to or larger than 2 .mu.m, i.e., the ratio .alpha. is in a range
between 10 and 28.6 and the ratio .beta. is in a range between 3.5
and 10, the ratio of impedance change .DELTA.Z/Zo is equal to or
larger than 10%. Preferably, referring to the devices S31, S35,
when the length L1 is equal to or longer than 2000 .mu.m, the width
L2 is in a range between 5 .mu.m and 50 .mu.m, and the thickness L3
is equal to or larger than 2 .mu.m, i.e., the ratio .alpha. is in a
range between 40 and 400 and the ratio .beta. is in a range between
2.5 and 25, the ratio of impedance change .DELTA.Z/Zo is equal to
or larger than 10%. Preferably, referring to the devices S41, S42,
when the length L1 is equal to or longer than 2000 .mu.m, the width
L2 is in a range between 7 .mu.m and 15 .mu.m, and the thickness L3
is equal to or larger than 0.3 .mu.m, i.e., the ratio .alpha. is in
a range between 133.3 and 258.7 and the ratio .beta. is in a range
between 23.3 and 50, the ratio of impedance change .DELTA.Z/Zo is
equal to or larger than 10%.
[0097] More preferably, referring to the devices S23, S24, S34,
when the length L1 is equal to or longer than 1000 .mu.m, the width
L2 is in a range between 7 .mu.m and 50 .mu.m, and the thickness L3
is equal to or larger than 2 .mu.m, i.e., the ratio .alpha. is in a
range between 20 and 142.9 and the ratio .beta. is in a range
between 3.5 and 10, the ratio of impedance change .DELTA.Z/Zo is
equal to or larger than 20%. In this case, it is much preferred
that the width L2 is in a range between 7 .mu.m and 20 .mu.m.
Preferably, referring to the device S43, when the length L1 is
equal to or longer than 2000 .mu.m, the width L2 is in a range
between 7 .mu.m and 20 .mu.m, and the thickness L3 is equal to or
larger than 0.5 .mu.m, i.e., the ratio .alpha. is in a range
between 100 and 285.7 and the ratio .beta. is in a range between 14
and 40, the ratio of impedance change .DELTA.Z/Zo is equal to or
larger than 20%.
[0098] Much more preferably, referring to the devices S25, S32,
S45, when the length L1 is equal to or longer than 2000 .mu.m, the
width L2 is in a range between 7 .mu.m and 20 .mu.m, and the
thickness L3 is equal to or larger than 2 .mu.m, i.e., the ratio
.alpha. is in a range between 100 and 285.7 and the ratio .beta. is
in a range between 3.5 and 10, the ratio of impedance change
.DELTA.Z/Zo is equal to or larger than 30%.
[0099] FIG. 15 shows the ratio of impedance change .DELTA.Z/Zo of
various devices S51-S56, each of which has the magnetic layer 26
made of the same composition of Ni and Fe as that of the device S11
(i.e., Ni.sub.81Fe.sub.19). Each device S51-S56 has the magnetic
layer 26 having a length L1 of 2000 .mu.m a width L2 of 10 .mu.m, a
thickness L3 of 2 .mu.m, and a different grain size. Here, each
device has a surface roughness of the substrate 22 of 2 nm. FIG. 16
is a graph showing a relationship between the grain size and the
ratio of impedance change .DELTA.Z/Zo of the various devices
S51-S56.
[0100] As shown in FIGS. 15 and 16, as the grain size of the
magnetic layer 26 becomes smaller, the ratio of impedance change
.DELTA.Z/Zo becomes large. When the grain size is equal to or
smaller than 1100 nm, the ratio of impedance change .DELTA.Z/Zo is
larger than 10%. Further, when the grain size is equal to or
smaller than 350 nm, the ratio of impedance change .DELTA.Z/Zo is
larger than 20%. Furthermore, when the grain size is equal to or
smaller than 10 nm, the ratio of impedance change .DELTA.Z/Zo is
larger than 30%.
[0101] FIG. 17 shows the ratio of impedance change .DELTA.Z/Zo of
various devices S61-S66, each of which has the magnetic layer 26
made of the same composition of Ni and Fe as that of the device S11
(i.e., Ni.sub.81Fe.sub.19). Each device S61-S66 has the magnetic
layer 26 having a length L1 of 2000 .mu.m a width L2 of 10 .mu.m, a
thickness L3 of 2 .mu.m, and a grain size of 10 nm. Each device has
a different surface roughness of the substrate 22. FIG. 18 is a
graph showing a relationship between the surface roughness and the
ratio of impedance change .DELTA.Z/Zo of the various devices
S61-S66.
[0102] As shown in FIGS. 17 and 18, as the surface roughness of the
substrate 22 becomes smaller, the ratio of impedance change
.DELTA.Z/Zo becomes large. When the surface roughness is equal to
or smaller than 1300 nm, the ratio of impedance change .DELTA.Z/Zo
is larger than 10%. Further, when the surface roughness is equal to
or smaller than 400 nm, the ratio of impedance change .DELTA.Z/Zo
is larger than 20%. Furthermore, when the surface roughness is
equal to or smaller than 50 nm, the ratio of impedance change
.DELTA.Z/Zo is larger than 30%.
[0103] In the above devices having a certain construction, the
sensor sensitivity is not decreased even when the device is
processed with heat treatment. Thus, the device according to the
first embodiment has high heat resistance. Further, the device has
high sensor sensitivity.
Second Embodiment
[0104] A magnetic impedance device 2 according to a second
embodiment of the present invention includes the magnetic layer 26
and a protection layer 32, as shown in FIG. 19. The protection
layer 32 covers the magnetic layer 26, and is made of electrically
insulation material.
[0105] In general, a magnetic impedance device includes a magnetic
layer having zero magneto-striction or low magneto-striction. This
is because the magnetic layer having low magneto-striction is
prevented from changing the magnetic properties generated by a
striction of the magnetic layer, for example, from reducing the
sensor sensitivity or the detection accuracy. However, the
inventors obtain the following experimental results. In the device
having a protection layer for covering the magnetic layer, an
internal stress .sigma. in the protection layer affects the
magnetic properties of the magnetic layer, so that the sensor
sensitivity is reduced. Further, there is a different influence of
the internal stress .sigma. affecting the magnetic properties of
the magnetic layer between a case where the internal stress .sigma.
of the protection layer is a compression stress and a case where
the internal stress .sigma. is a tensile stress.
[0106] Considering the above experimental result, the device 2
according to the second embodiment includes the substrate 22, the
insulation layer 24, the magnetic layer 26, a pair of electrode
pads 28a, 28b and the protection layer 32. The external magnetic
field Hext is applied to the device 2 along with the energization
direction of the alternating current.
[0107] Although the magnetic layer is made of NI--Fe series alloy
film, the magnetic layer 26 can be formed of linear shaped or thin
film type amorphous alloy such as Co--Nb--Zr alloy, Co--Si--B
alloy, and the like. There is no limitation of the shape of the
magnetic layer 26.
[0108] The protection layer 32 covers the surface of the magnetic
layer 26 and the surface of the insulation layer 24. The electrode
pads 28a, 28b are not covered with the protection layer 32, so that
the electrode pads 28a, 28b are exposed from the protection layer
32. The protection layer 32 is made of non-magnetic material having
electrically insulation property. Preferably, the protection layer
32 is made of, for example, silicon nitrides, aluminum nitrides,
silicon oxides, phosphorized silicon oxides, and boron-doped
silicon oxides. The protection layer 32 made of these materials
prevents from oxidizing in a case where the magnetic layer 26 is
made of easily oxidized material such as Ni and/or Fe, or prevents
from crystallizing by heat treatment in a case where the magnetic
layer 26 is made of amorphous alloy. Further, these materials are
usually used in a general semiconductor process, so that the device
2 can be manufactured with using a general semiconductor process.
Further, it is preferred that the protection layer 32 is formed of
composite material having a plurality of insulation materials or
has a laminated structure. In this case, by a combination of a
plurality of insulation materials, the internal stress .sigma. of
the protection layer 32 can be reduced. Preferably, a thickness L11
of the protection layer 32 is in a range between 0.2 .mu.m and 5
.mu.m. In this case, the protection layer 32 can protect the
magnetic layer 26 sufficiently. Further, the protection layer 32 is
prevented from removing from the magnetic layer 26 caused by the
internal stress .sigma. of the protection layer 32. More
preferably, the thickness of the protection layer 32 is in a range
between 0.5 .mu.m and 2 .mu.m. In this case, the protection layer
32 protects the magnetic layer 26 much sufficiently. The above
reasons are described later.
[0109] When the internal stress .sigma. of the protection layer 32
is a compression stress, it is preferred that a magnitude of the
compression stress is lower than 500 MPa. When the internal stress
.sigma. of the protection layer 32 is a tensile stress, it is
preferred that the magnitude of the tensile stress is lower than
100 MPa. In this case, the sensor sensitivity of the device 2 is
prevented from reducing caused by a deterioration of soft magnetic
property of the magnetic layer 26 by the internal stress .sigma. of
the protection layer 32. Further, the protection layer 32 is
prevented from removing from the magnetic layer 26 caused by the
internal stress a of the protection layer 32. When the internal
stress .sigma. of the protection layer 32 is a compression stress,
more preferably the magnitude of the compression stress is lower
than 200 MPa. When the internal stress .sigma. of the protection
layer 32 is a tensile stress, more preferably the magnitude of the
tensile stress is lower than 50 MPa. Preferably, the protection
layer 32 has an insulation resistance, which is equal to or larger
than 10M.OMEGA.. The above reasons are described later.
[0110] When the magnetic layer 26 is made of, for example,
amorphous alloy, the amorphous alloy may be crystallized in a
semiconductor process under high temperature higher than
400.degree. C., so that the magnetic property is changed, i.e., the
sensor sensitivity is reduced. Therefore, when the magnetic layer
26 is made of a certain material such as amorphous material, which
is easily affected by temperature, it is preferred that the
protection layer 32 is made of a material such as SiO.sub.2,
phospho-silicate glass (i.e., PSG), boro-silicate glass (i.e., BSG)
and boro-phospho-silicate glass (i.e., BPSG), which has low heat
conductivity.
[0111] When the magnetic layer 26 includes a material such as Ni
and/or Co, which is easily oxidized, it is considered that the heat
treatment under high temperature higher than 400.degree. C. in a
semiconductor process is performed in vacuum so that the magnetic
layer 26 can be prevented from oxidizing. However, additional
equipment to perform the heat treatment in vacuum is required, so
that the manufacturing cost is increased. On the other hand, in a
case where the protection layer 32 is disposed on the magnetic
layer 26, the magnetic layer 26 is prevented from oxidizing even
when the heat treatment is performed in the presence of oxygen, for
example, in air. Thus, no additional equipment to perform the heat
treatment in vacuum is necessitated. Further, comparing with
increase of the manufacturing cost to prepare the additional
equipment of the heat treatment in vacuum, manufacturing cost
increase of an additional process to form the protection layer 32
is much lower. Moreover, the magnetic layer 26 is prevented from
oxidizing by the protection layer 32 after being manufactured.
[0112] Next, the magnetic impedance device 2 according to the
second embodiment is manufactured as follows. At first, as shown in
FIGS. 4A to 4C, the substrate 22 is prepared. Then, the insulation
layer 24 is formed on the substrate 22. When the substrate 22 is
made of silicon, the surface of the silicon substrate 22 is
oxidized with using thermal oxidation method so that the insulation
layer 24 made of silicon oxides is formed. Further, the insulation
layer 24 can be formed with using chemical vapor deposition method,
sputtering method, or the like, and is made of silicon oxides,
silicon nitrides. There is no limitation of the deposition method
for forming the insulation layer 24.
[0113] Next, a ferromagnetic film having a soft magnetic property
is formed on the insulation layer 24. The ferromagnetic film can be
formed with using sputtering method, vapor deposition, or coating
method. There is no limitation of the deposition method for forming
the ferromagnetic film. The ferromagnetic film is patterned into a
predetermined shape with using photo etching method, so that the
magnetic layer 26 is formed, as shown in FIG. 4C. In this case,
preferably the single axial anisotropic magnetic field is applied
to the magnetic layer 26 in the energization direction of the
alternating current, i.e., the longitudinal direction of the
magnetic layer 26 with using deposition under magnetic filed or
heat treatment under magnetic field, so that the magnetic layer 26
has the axis of easy magnetization.
[0114] Next, a preliminary layer for an electrode is formed on both
the magnetic layer 26 and the insulation layer 24. The preliminary
layer can be formed with using the sputtering method, vapor
deposition, or coating method. There is no limitation of the
deposition method for forming the preliminary layer. The
preliminary layer is patterned into a predetermined shape with
using photo etching method, so that the electrode pads 28a, 28b are
formed so as to cover both ends of the magnetic layer 26, as shown
in FIGS. 1 and 2.
[0115] Next, an insulation material layer is formed on the
insulation layer 24, the magnetic layer 26 and the electrode pads
28a, 28b. The insulation material layer can be formed with using
the CVD method (that includes a plasma CVD method), the sputtering
method and the like. There is no limitation of deposition method.
This insulation material layer is patterned into a predetermined
shape with using reactive ion etching method (i.e., RIE method) and
the like, so that part of the insulation material layer disposed on
the electrode pads 28a, 28b is removed. Thus, the protection layer
32 shown in FIGS. 19 and 20 is formed. Then, the electrodes 28a,
28b is connected with bonding wires. Thus, the magnetic impedance
device 2 is completed.
[0116] Specifically, the detailed manufacturing method is described
as follows. A magnetic impedance device S205 (that is shown in FIG.
21) according to this embodiment is manufactured. As shown in FIG.
4, the silicon substrate 22 is prepared. The insulation layer 24
made of silicon oxides having thickness of 1 .mu.m is formed on the
substrate 22 with using the thermal oxidation method.
[0117] Next, a Ni.sub.81Fe.sub.19 Alloy film having thickness of 2
.mu.m is formed on the insulation layer 24 with using the
sputtering method under magnetic field. The Ni.sub.81Fe.sub.19
Alloy film is patterned into a predetermined shape with using the
photo etching method, so that the magnetic layer 26 is formed.
Specifically, the magnetic layer 26 has a length of 2 mm and a
width of 10 .mu.m. At this time, the single axial anisotropic
magnetic field is applied to the magnetic layer 26 in the
energization direction of the alternating current, i.e., the
longitudinal direction of the magnetic layer 26 with using the
sputtering method under magnetic filed, so that the magnetic layer
26 has the axis of easy magnetization.
[0118] Next, aluminum layer having thickness of 1 .mu.m is formed
on both the insulation layer 24 and the magnetic layer 26. The
aluminum layer is patterned into a predetermined shape with using
the photo etching method so that the electrode pads 28a, 28b are
formed so as to cover both ends of the magnetic layer 26, as shown
in FIGS. 1 and 2. Specifically, the area of each electrode pad 28a,
28b disposed on the upper surface of the electrode pad 28a, 28b is
a square of 200 .mu.m.times.200 .mu.m.
[0119] Next, a silicon nitride layer having thickness of 1 .mu.m is
formed on the insulation layer 24, the magnetic layer 26 and the
electrode pads 28a, 28b with using the plasma CVD method. The
silicon nitride layer is patterned into a predetermined shape with
using the RIE method and the like so that part of the insulation
material layer disposed on the electrode pads 28a, 28b is removed.
Thus, the protection layer 32 is formed. On the assumption that the
device S205 is processed in semiconductor process, the device S205
is processed in argon (i.e., Ar) gas atmosphere under 450.degree.
C. during 30 minutes. After that, each electrode pad 28a, 28b is
connected with a bonding wire. Thus, the device S205 is
completed.
[0120] The device S205 is evaluated with using a coil and an
impedance analyzer. Here, the coil provides an external magnetic
field Hext applied to the device S205, and the impedance analyzer
detects a high frequency impedance Z generated at both ends of the
magnetic layer 26 of the device S205. The external magnetic field
Hext is parallel to the energization direction of the high
frequency alternating current generated from the alternating
current supply 30. The external magnetic field Hext is corrected
with a gauss meter disposed on the substrate 22. The impedance Z is
measured in case of the frequency of the high frequency current
supply 30 at 100 MHz. The magnetic impedance property of the device
S205 is evaluated with a ratio of impedance change .DELTA.Z/Zo.
Here, Zo is impedance of the device S205 in a case where the
external magnetic field Hext is zero. .DELTA.Z is a difference
between impedance Z in a case where the external magnetic field
Hext is 100 Oe and the impedance, Zo at zero, i.e., .DELTA.Z=Z-Zo.
The above evaluation is performed before and after heat treatment
under 450.degree. C. so as to confirm a protection effect of the
protection layer 32.
[0121] FIG. 22 is a graph of magnetic impedance property of the
device S205 showing an impedance change in accordance with the
external magnetic field Hext before the heat treatment. In case of
the device S205, the impedance of the device S205 is reduced in
accordance with increasing or decreasing the external magnetic
field Hext. As shown in FIG. 5, the ration of impedance change
.DELTA.Z/Zo, which corresponds to the sensor sensitivity, is about
30%.
[0122] Next, the device S205 is heated in Ar gas atmosphere under
450.degree. C. during 30 minutes. Then, the device is evaluated
with the above method. In this case, the magnetic impedance
property of the device S205 has the same relationship between the
external magnetic field and the magnetic impedance as that of the
device S205 before heat treatment shown in FIG. 22. This result
shows that the protection layer 32 made of silicon nitride covers
the magnetic layer 26 made of Ni--Fe alloy film so that the Ni--Fe
alloy film composing the magnetic layer 26 is not oxidized by the
heat treatment. Therefore, the magnetic properties of the magnetic
layer 26 do not change substantially. Further, as described later,
although the protection layer 32 of the device S205 has a
compression stress of -120 MPa, the internal stress .sigma. of the
compression stress does not affect the magnetic properties of the
magnetic layer 26 substantially.
[0123] Both of ratios of impedance change .DELTA.Z/Zo before and
after heat treatment of various devices S201-S219 are measured. As
shown in FIG. 21, devices S201-209 has the protection layer 32 made
of silicon nitride and a different thickness of the protection
layer 32 and/or a different internal stress .sigma., which are
different from those of the device S205. Each device S210-S218 has
the protection layer 32 made of different material and a different
thickness of the protection layer 32 and/or a different internal
stress .sigma., which are different from those of the device S205.
A device S219 has no protection layer 32.
[0124] As shown in FIG. 21, in the devices S202-S209, S211-S218,
the sensor sensitivity, i.e., the ratio of impedance change
.DELTA.Z/Zo does not change substantially before and after heat
treatment. However, in the devices S201, S210, S219, the sensor
sensitivity changes largely before and after heat treatment.
Namely, the sensor sensitivity of the device S201, S210, S219 is
much decreased after the heat treatment. That is because the device
S219 has no. protection layer 32, so that the soft magnetic
property of the magnetic layer 26 disappears after the heat
treatments since the Ni--Fe alloy film composing the magnetic layer
26 is oxidized by the heat treatment under 450.degree. C. Although
the device S201, S210 has the protection layer 32, the thickness of
the protection layer 32 is 0.1 .mu.m, which is so thin that the
protection layer 32 can not protect the magnetic layer 26 made of
Ni--Fe alloy film from oxidation.
[0125] FIG. 23 shows the ratio of impedance change .DELTA.Z/Zo of
various devices S204-S206, each of which has the protection layer
32 made of silicon nitride. The thickness of the protection layer
32 of the device S204-S206 is 1 .mu.m, and the internal stress
.sigma. of the protection layer 32 is different from each other.
FIG. 23 also shows the ratio of impedance change .DELTA.Z/Zo before
and after heat treatment. Here, in a case where the internal stress
.sigma. is positive, the internal stress .sigma. is the tensile
stress. In a case where the internal stress .sigma. is negative,
the internal stress .sigma. is the compression stress.
[0126] FIG. 24 shows the ratio of impedance change .DELTA.Z/Zo of
various devices S213-S216, each of which has the protection layer
32 made of silicon oxides. The thickness of the protection layer 32
of the device S213-S216 is 1 .mu.m, and the internal stress .sigma.
of the protection layer 32 is different from each other. FIG. 24
also shows the ratio of impedance change .DELTA.Z/Zo before and
after heat treatment.
[0127] As shown in FIGS. 22 and 23, as the internal stress .sigma.
of the protection layer 32 becomes larger, the ratio of impedance
change .DELTA.Z/Zo is decreased. Namely, the sensor sensitivity is
reduced. That is because a stress is generated in the magnetic
layer 26 by the influence of the internal stress .sigma. of the
protection layer 32 when the internal stress .sigma. of the
protection layer 32 becomes large. Therefore, the magnetic
properties of the magnetic layer 26 are changed, specifically, a
coercive force of the magnetic layer 26 becomes large, so that the
relative magnetic permeability of the magnetic layer 26 is reduced.
Thus, the sensor sensitivity is reduced.
[0128] Further, there is a difference between one case where the
internal stress .sigma. of the protection layer 32 is the tensile
stress and the other case where the internal stress .sigma. is the
compression stress. Specifically, even though the magnitude of the
stress is the same, the ratio of impedance change is different
between the tensile stress and the compression stress. More
specifically, when the magnitude of the internal stress .sigma. is
the same, the reduction of the ratio of impedance change in case of
the tensile stress is smaller than that in case of the compression
stress.
[0129] As shown in FIGS. 23 and 24, in a case where the tensile
stress is equal to or smaller than 100 MPa, the ratio of impedance
change becomes larger than 20%. Preferably, in a case where the
tensile stress is equal to or smaller than 50 MPa, the ratio of
impedance change becomes larger than 25%. In a case where the
compression stress is equal to or smaller than 500 MPa, the ratio
of impedance change becomes larger than 20%. Preferably, in a case
where the compression stress is equal to or smaller than 200 MPa,
the ratio of impedance change becomes larger than 25%.
[0130] In the above devices having a certain construction of the
protection layer 32, the sensor sensitivity is not decreased even
when the device is processed with heat treatment. Thus, the device
according to the second embodiment has high heat resistance.
Specifically, the magnetic layer 26 of the device is not
substantially oxidized even when the device is annealed. Further,
the device has high sensor sensitivity.
Third Embodiment
[0131] A magnetic sensor apparatus 300 having a magnetic impedance
device 301 according to a third embodiment of the present invention
is shown in FIGS. 25-27. FIG. 27 shows a schematic diagram of the
apparatus 300. The apparatus 300 includes the magnetic impedance
device 301, a resistance 312, an oscillator 313, and an amplifier
314. Here, the resistance 312, the oscillator 313 and the amplifier
314 work as a periphery circuitry. The periphery circuitry may
include a regulator circuit, and an interface circuit for
communicating with a signal between the apparatus 300 and an
external circuit. The device 301 is made of, for example, Ni--Fe
series alloy, and connects to the resistance 312 in series. Here,
the device 301 made of Ni--Fe series alloy has a wide dynamic range
of detection of the magnetic field with using the magnetic
impedance effect. Although the device 301 according to this
embodiment is made of Ni--Fe alloy, the device 301 can be formed of
other materials. The resistance 312 and the device 301 also connect
to both ends of the oscillator 313 in series. The oscillator 313
works as a driving circuit for supplying a high frequency current
to the device 301, and both ends of the oscillator 313 provide
output terminals. The above series circuit composing the resistance
312, the device 301 and the oscillator 313 has a common contact
point for connecting to an input terminal of the amplifier 314. The
amplifier 314 amplifies a detection signal and outputs the
amplified signal. Therefore, the amplifier 314 works as a detection
circuit for detecting impedance change of the device 301.
[0132] FIG. 25 is a cross-section showing the apparatus 300. FIG.
26 is an enlarged plan view showing the device 301. The apparatus
300 is formed with using a semiconductor manufacturing method in
bipolar process. However, the apparatus 300 can be formed with
using another semiconductor process such as MOS process and BiCMOS
process. The apparatus 300 includes a NPN type transistor 315
composing part of the amplifier 314, and a sensing portion 302
composing the magnetic impedance device 301.
[0133] The transistor 315 and the device 301 are disposed on a
semiconductor substrate 322 made of P type silicon. Further, the
resistance 312, the oscillator 313 and the amplifier 314 are
disposed on the substrate 322 (not shown).
[0134] The bipolar process for forming the transistor 315 is a
well-known process of the semiconductor manufacturing method. The
transistor 315 is formed with using implant patterning method,
implant diffusion method, separation patterning method, separation
diffusion method, and the like, so that a base, an emitter and a
collector the transistor 315 are formed with using patterning
method, diffusion method and the like. Here, the semiconductor
substrate 322 has an N type region disposed under the device 301.
The N type region is formed with using the separation diffusion
method.
[0135] Next, an insulation layer 324 made of silicon dioxide is
formed on the substrate 322 and is patterned into a predetermined
shape. Then, a wiring layer 328 made of aluminum and the like is
formed on the substrate 322. The wiring layer 328 is patterned into
a predetermined shape so that part of the wiring layer is etched
and removed so as to form the device 301. At that time a top end
328a of the wiring layer 328 is patterned into a tapered shape. The
top end 328a of the wiring layer 328 connects to the device
301.
[0136] Then, Ni--Fe alloy composing the device 301 is deposited on
the substrate 322 with using sputtering method under magnetic
field. The thickness of the Ni--Fe alloy deposited on the substrate
322 is in a range between 1 .mu.m and 5 .mu.m. Since the top end
328a of the wiring layer 328 is formed to be a tapered shape, the
device 301, i.e., the Ni--Fe alloy film is limited from cutting
caused by fault of step coverage.
[0137] Next, to improve the magnetic properties of the device 301,
the apparatus 300 is annealed at about 300.degree. C. in vacuum
under magnetic field. At last, a protection layer 332 made of
silicon nitride, silicon dioxide and the like is formed on the
substrate 322.
[0138] Thus, the apparatus 300 having the device 301, the
resistance 312, the oscillator 313, the amplifier 314, and other
circuits are formed on the substrate 322. Therefore, the apparatus
300 is manufacture to be compact and minimized so that the
manufacturing cost of the apparatus 300 becomes small. Further, the
device 301 is formed of thin film so that the dimensions of the
device 301, specifically thickness of the device 301, are smaller
than that having an amorphous wire. Thus, the apparatus 300 is
formed to be compact.
[0139] Further, since the top end 328a of the wiring layer 328
connecting to both ends of the device 301 is formed to be a tapered
shape, the Ni--Fe alloy film composing the device 301 is limited
from cutting at around the top end 328a of the wiring layer 328.
That is because the step coverage of the Ni--Fe alloy film at the
top end 328a is improved when the Ni--Fe alloy film is deposited on
the wiring layer 328.
[0140] Thus, the sensor apparatus 300 having the magnetic impedance
device 301 according to this embodiment has minimum size and is
made with low manufacturing cost.
Fourth Embodiment
[0141] A magnetic sensor apparatus 303 having a magnetic impedance
device 301A according to a fourth embodiment of the present
invention is shown in FIG. 28. Although the device 301A according
to this embodiment is made of Ni--Fe alloy, the device 301A can be
formed of other materials. The apparatus 303 includes a metallic
film 351 made of titanium (i.e., Ti) material. The metallic film
351 is disposed on a connecting portion between the wiring layer
328 and a magnetic impedance device 301A. The metallic film 351 is
formed on the substrate before the wiring layer 328 is formed.
Thus, the metallic film 351 electrically connects the wiring layer
328 and the device 301A. Then, the protection layer 332 is formed
on the substrate 322.
[0142] In the apparatus 303, since the metallic film 351 made of Ti
material connects both ends of the device 301A and the top ends of
the wiring layer 328, the connection between the device 301A and
the wiring layer 328 becomes excellent ohmic contact.
[0143] Thus, the sensor apparatus 303 having the magnetic impedance
device 301A according to this embodiment has minimum size and is
made with low manufacturing cost. Further, the reliability of the
connection is improved.
Fifth Embodiment
[0144] A magnetic sensor apparatus 304 having a magnetic impedance
device 301B according to a fifth embodiment is shown in FIG. 29.
Although the device 301B according to this embodiment is made of
Ni--Fe alloy, the device 301B can be formed of other materials. The
apparatus 304 includes an interlayer insulation film 352 made of
silicon oxides, silicon nitrides and the like. The interlayer
insulation film 352 is formed on the substrate 322 after the device
301B and the wiring layer 328 are formed on the substrate 322. The
interlayer insulation film 352 has a through hole for connecting
the device 301B and the wiring layer 328. In the through hole, a
metallic film 351 made of aluminum material, copper material,
Al--Ti series alloy or the like is filled and deposited so that the
metallic film 351 connects the wiring layer 328 and the device
301B. Then, the protection layer 332 is formed on the substrate
322.
[0145] In the apparatus 304, the interlayer insulation film 352 is
formed on the upper surfaces of both the device 301B and the wiring
layer 328, and the metallic film 351 connects both ends of the
device 301B and the top ends of the wiring layer 328. Since the
electrical connection is disposed on the upper surfaces, so that
the connection between the device 301B and the wiring layer 328
becomes excellent ohmic contact.
[0146] Thus, the sensor apparatus 304 having the magnetic impedance
device 301B according to this embodiment has minimum size and is
made with low manufacturing cost. Further, the reliability of the
connection is improved.
Sixth Embodiment
[0147] A magnetic sensor apparatus 305 having the magnetic
impedance device 301 according to a sixth embodiment is shown in
FIG. 30. The apparatus 305 includes a barrier metal film 354 made
of Ti material and the like. The barrier metal film 354 is formed
on the top ends 328a of the wiring layer and its neighboring
portion. Then, the device 301 and the protection layer 332 are
formed on the substrate 322.
[0148] In the apparatus 305, since the barrier metal film 354 is
disposed on the top ends 328a of the wiring layer and its
neighboring portion, the connection portion between the device 301
and the wiring layer 328 has a tri-layer structure. Therefore, the
tri-layer structure provides excellent ohmic contact between the
device 301 and the wiring layer 328.
[0149] Thus, the sensor apparatus 305 having the magnetic impedance
device 301 according to this embodiment has minimum size and is
made with low manufacturing cost. Further, the reliability of the
connection is improved.
Seventh Embodiment
[0150] A magnetic sensor apparatus 306 having the magnetic
impedance device 301 according to a seventh embodiment is shown in
FIG. 31. The apparatus 306 includes a stress relaxation layer 355
made of poly-imide. However, the stress relaxation layer 355 can be
formed of other organic materials or inorganic materials with using
thin film deposition techniques. The stress relaxation layer 355 is
formed on the insulation layer 324 before the wiring layer 328 is
formed. Namely, the insulation layer 324 is formed on the substrate
322, and the stress relaxation film 355 is formed on the surface of
the insulation layer 324. After that, the wiring layer 328 is
formed on the stress relaxation layer 355. The thickness of the
stress relaxation layer is determined in accordance with the
thickness of the device 301 disposed on the stress relaxation layer
355. For example, the thickness of the stress relaxation layer 355
is in a range between 1 .mu.m and 10 .mu.m.
[0151] Next, the Ni--Fe alloy film composing the device 301 is
deposited with using the sputtering method so that the thickness of
the Ni--Fe alloy film is in a range between 1 .mu.m and 5 .mu.m.
Then, to improve the magnetic properties of the device 301, the
apparatus 306 is annealed at about 300.degree. C. in vacuum under
magnetic field. At last, the protection layer 332 made of silicon
nitride, silicon dioxide and the like is formed on the substrate
322.
[0152] When the apparatus 306 is annealed, a stress is generated in
the substrate 322 since coefficient of thermal expansion of the
substrate 322 is different from that of the device 301. Therefore,
in some cases, the substrate 322 may be cracked.
[0153] Conventionally, to prevent from cracking, deposition
condition for depositing a magnetic layer composing a magnetic
impedance device is changed, or a film quality of the magnetic
layer is changed. However, it is not considered about the crack in
the substrate 322.
[0154] In the apparatus 306, the stress relaxation layer 355 is
disposed between the substrate 322 and the device 301, so that the
stress being applied to the substrate 322 is absorbed to the stress
relaxation layer 355. Thus, the substrate 322 is limited from
cracking. Further, since the stress relaxation layer 355 is made of
poly-imide, which is an organic material, the stress relaxation
layer 355 is easily formed.
[0155] Thus, the sensor apparatus 306 having the magnetic impedance
device 301 according to this embodiment has minimum size and is
made with low manufacturing cost. Further, the reliability of the
apparatus concerned with a mechanical strength is improved.
Eighth Embodiment
[0156] A magnetic sensor apparatus 307 having the magnetic
impedance device 301B according to an eighth embodiment is shown in
FIG. 32. The apparatus 307 includes the stress relaxation layer
355. When the through hole for connecting the device 301B and the
wiring layer 328 is formed in the interlayer insulation film 352,
the through hole goes through the stress relaxation layer 355
disposed under the interlayer insulation film 352 so that the
through hole reaches the wiring layer 328.
[0157] In the apparatus 307, the substrate 322 is limited from
cracking. Further, the interlayer insulation film 352 is formed on
the upper surfaces of both the device 301B and the wiring layer
328, and the metallic film 351 connects both ends of the device
301B and the top ends of the wiring layer 328. Since the electrical
connection is disposed on the upper surfaces, so that the
connection between the device 301B and the wiring layer 328 becomes
excellent ohmic contact.
[0158] Thus, the sensor apparatus 307 having the magnetic impedance
device 301B according to this embodiment has minimum size and is
made with low manufacturing cost. Further, the reliability of the
apparatus concerned with a mechanical strength is improved.
Furthermore, the reliability of the connection is improved.
Ninth Embodiment
[0159] A magnetic sensor apparatus 308 having the magnetic
impedance device 301 according to a ninth embodiment is shown in
FIG. 33. The apparatus 308 includes an oxidation protection film
356 made of silicon nitrides, silicon dioxide and the like. The
oxidation protection film 356 is formed on the surface of the
device 301.
[0160] Here, the magnetic properties of the device 301 depend on
the surface of the device since the device 301 utilizes the skin
effect of magnetic thin film. Therefore, if the surface of the
device 301 is oxidized, the magnetic detection of the device 301 is
reduced.
[0161] Therefore, the oxidation protection film 356 protects the
surface of the device 301 so as not to be oxidized. Thus, the
magnetic properties of the device 301 can be maintained to be
excellent.
[0162] Thus, the sensor apparatus 308 having the magnetic impedance
device 301 according to this embodiment has minimum size and is
made with low manufacturing cost. Further, the apparatus 308 has
high heat resistance.
[0163] The oxidation protection film 356 can be formed on the
device 300, 301A, 301B of the apparatus 303-307 shown in FIGS.
28-32.
Tenth Embodiment
[0164] A rotation sensor apparatus 400 having a magnetic sensor 401
according to a tenth embodiment of the present invention is shown
in FIG. 34. The rotation sensor apparatus 400 includes a rotation
body 411 as an object to be detected its rotation, a casing 412 for
covering the rotation body 411, and the magnetic sensor 401. The
casing 412 separates between the rotation body 411 and the magnetic
sensor 401. The magnetic sensor 401 is provided by, for example,
the magnetic sensor apparatus 25 shown in FIG. 25. Therefore, the
magnetic sensor 401 includes a magnetic impedance sensor.
[0165] The rotation body 411 is made of a magnetic material or a
material including the magnetic material, and is a gear having a
gearwheel shape. When the rotation body 411 rotates, a magnetic
field around the rotation body 411 changes repeatedly.
[0166] In a case where the rotation body 411 is made of magnetic
material, the rotation body 411 is magnetized by a surrounding
magnetic field. Therefore, the rotation body 411 works as a
magnetized gear 411a, as shown in FIG. 35A. The magnetized gear
411a attracts a permanent magnet. In FIG. 35A, a pair of arrows
shows magnetic field lines generated by the magnetized gear 411a.
When the magnetized gear 411a rotates, the magnetic field lines
also rotate so that the intensity of magnetic field around the
magnetized gear 411a changes periodically.
[0167] In a case where the rotation body 411 is not magnetized, the
rotation body works as a non-magnetized gear 411b. Even though the
non-magnetized gear 411b is not magnetized, the intensity of
magnetic field around the non-magnetized gear 411b changes
periodically. That is because the magnetic field lines of the
geomagnetic filed changes periodically by alternating appearance of
a concavity and convexity of periphery of the gear 411b when the
non-magnetized gear 411b rotates. As shown in FIGS. 35B and 35C,
when the concavity of the gear 411b faces the magnetic sensor 401,
the intensity of magnetic field around the magnetic sensor 401
becomes weak. When the convexity of the gear 411b faces the
magnetic sensor 401, the intensity of magnetic field around the
magnetic sensor 401 becomes strong. Thus, the intensity of magnetic
field around the gear 411b changes periodically.
[0168] Thus, the magnetic sensor 401 detects the periodic change of
the intensity of magnetic field when the rotation body 411 rotates.
Therefore, the rotation of the rotation body 411 can be detected by
the magnetic sensor 401.
[0169] The magnetic sensor 401 is, for example, a magnetic sensor
apparatus having a magnetic impedance device. The magnetic sensor
apparatus includes a Ni--Fe series alloy film formed on a
non-magnetic substrate. As shown in FIG. 35, the Ni--Fe series
alloy film of the magnetic sensor 401 has a predetermined pattern
in such a manner that a plurality of linear shaped films is
arranged at predetermined intervals parallel to a magnetic field
detection direction, and is repeatedly connected together so that
they forms a switchback shape.
[0170] A high frequency alternating current is applied to both ends
of the Ni--Fe series alloy film of the magnetic sensor 401, so that
the impedance between both ends is changed in accordance with the
change of the external magnetic field. The impedance change is
measured by an electric circuit (not shown), and then the impedance
change is converted to an electric signal. The electric signal is
outputted from the magnetic sensor 401. Thus, the signal, which
corresponds to the rotation of the rotation body 411, is
obtained.
[0171] The magnetic sensor 401 having the magnetic impedance device
has high sensor sensitivity, which is much higher than that of a
conventional magneto-resistance sensor or hall element sensor.
Accordingly, even when the magnetic sensor 401 is disposed outside
the casing 412, the magnetic sensor 401 can detect the change of
magnetic field generated by the rotation of the rotation body 411
disposed in the casing 412 so that the magnetic sensor 401 detects
the rotation of the rotation body 411. Specifically, the magnetic
sensor 401 detects the periodic change of the intensity of magnetic
field, which is generated by the rotation of the rotation body 411
and leaks outside the casing 412. Then, the magnetic sensor 401
converts the signal to the electric signal. Here, the magnetic
sensor 401 includes a driving circuit, a sensing portion, a
detection circuit, a regulator, and an input-output circuit (not
shown).
[0172] The casing 412 works as a separation shield for separating
between the rotation body 411 and the magnetic sensor 401. The
casing 412 is made of aluminum. However, the casing 412 can be made
of other non-magnetic materials such as copper and brass. Further,
the casing 412 can be made of non-metallic non-magnetic materials
such as resin and ceramics. When the casing is made of non-magnetic
material, which does not attract a permanent magnet, the periodic
change of the intensity of magnetic field generated by the rotation
of the rotation body 411 is not substantially disturbed by the
casing 412. Therefore, even when the magnetic sensor 401 is
disposed outside the casing 412, the magnetic sensor 401 can detect
the rotation of the rotation body 411 accurately.
[0173] Here, since the magnetic sensor 401 has high sensor
sensitivity, the rotation sensor apparatus 400 has no bias magnet
for applying an additional magnetic field as a bias magnetic
field.
[0174] FIG. 36 shows a rotation sensor apparatus 402 having a pair
of magnetic sensors 401A, 401B. In the apparatus 402, two magnetic
sensors 401A, 401b are arranged in parallel so as to separate by a
half of pitch of the rotation body 411, i.e., by a half pitch of
gear. The apparatus 402 detects a differential output generated
from both magnetic sensors 401A, 401B. This differential output
cancels a constant component of the geomagnetic field disposed in
each magnetic sensor 401A, 401B. Therefore, the apparatus 402
detects the periodic change of magnetic field much accurately.
Namely, the apparatus 402 detects the rotation much accurately.
[0175] In each apparatus 400, 402, the magnetic sensor 401, 401A,
401B having high sensor sensitivity can detect the rotation of the
rotation body 411, 411a, 411b, even though the casing 412 as a
separation shield is disposed between the magnetic sensor 401,
401A, 401B and the rotation body 411, 411a, 411b. Therefore, the
magnetic sensor 401, 401A, 401B can be disposed outside the casing
412 without drilling an opening for mounting the magnetic sensor
401, 401A, 401B. Thus, the apparatus 400, 402 has high mounting
performance for mounting the magnetic sensor 401, 401A, 401B on the
casing 412 and high design freedom of the casing 412.
[0176] The apparatus 400, 402 is suitably used for detecting a
rotation of a cam of camshaft in an engine of an automotive vehicle
or a gear of a crankshaft in an engine of a vehicle. The apparatus
400, 402 can detect the rotation without opening a hole for
detecting the rotation, i.e., without drilling in a wall of engine
casing (e.g., an engine block) of the vehicle. Accordingly, the
apparatus 400, 402 has high mounting performance on the engine of
the vehicle, so that design freedom for mounting the apparatus on
the engine, on which a lot of parts are mounted, is improved.
[0177] Further, the apparatus 400, 402 can detect a rotation of a
wheel of an automotive vehicle. For example, the magnetic sensor
401, 401A, 401B detects the periodic change of the intensity of
magnetic field in accordance with the rotation of the wheel. Then,
the apparatus 400, 402 outputs the electric signal so that the
apparatus 400, 402 detects the rotation of the wheel. Here, the
magnetic sensor 401, 401A, 401B is mounted on an engine hood of the
vehicle or in a compartment of the vehicle.
Eleventh Embodiment
[0178] A rotation sensor apparatus 403 having the magnetic sensor
401 according to an eleventh embodiment of the present invention is
shown in FIG. 37. The rotation sensor apparatus 403 includes a
rotation body 411c, the casing 412 and the magnetic sensor 401. The
rotation body 411c includes a cylindrical magnet. Each of N and S
poles of the cylindrical magnet is alternately disposed on a
circumferential periphery of the cylindrical magnet.
[0179] As shown in FIG. 37, a center axis of the cylindrical magnet
works as a rotation axis, so that the rotation body 411c works as a
magnetic rotor having a pair of magnet poles disposed alternately
on the circumferential periphery of the rotor. Magnetic field lines
generated by the rotation body 411c output from the rotation body
411c, and are disposed periodically. When the rotation body 411c
rotates, a periodic change of the intensity of magnetic field is
generated around the rotation body 411c. This periodic change is
detected by the magnetic sensor 401 disposed outside the casing
412, so that the apparatus 403 can detect the rotation of the
rotation body 411c.
[0180] Although the apparatus 403 has a single magnetic sensor 401,
the apparatus can have a pair of magnetic sensors. In this case,
two magnetic sensors are arranged in parallel to separate by a half
of pitch of the rotation body 411c. The apparatus detects a
differential output generated from both magnetic sensors. This
differential output cancels a constant component of the geomagnetic
field disposed in each magnetic sensor. Therefore, the apparatus
detects the rotation much accurately. Specifically, in a case where
the intensity of magnetization of the rotation body 411c is weak so
that the periodic change of the intensity of magnetic field in
accordance with the rotation of the rotation body 411c is small,
the apparatus 403 having a pair of magnetic sensors can effectively
detect the rotation.
[0181] In the apparatus 403, the magnetic sensor 401 having high
sensor sensitivity can detect the rotation of the rotation body
411c, even though the casing 412 as a separation shield is disposed
between the magnetic sensor 401 and the rotation body 411c.
Therefore, the magnetic sensor 401 can be disposed outside the
casing 412 without drilling an opening for mounting the magnetic
sensor 401. Thus, the apparatus 403 has high mounting performance
for mounting the magnetic sensor 401 on the casing 412 and high
design freedom of the casing 412.
[0182] The apparatus 403 is suitably used for detecting a rotation
of a magnetized rotor mounted on a rotation shaft of a wheel of an
automotive vehicle. In this case, the apparatus 403 provides a
wheel rotation sensor for anti lock break system (i.e., ABS) of the
vehicle. In the ABS, the magnetic sensor 401 is mounted on a wheel
hub as a rotor casing without drilling a hole in the rotor casing.
Accordingly, the apparatus 403 can mount on the wheel hub, which is
required to have a narrow mounting portion since the wheel and a
suspension are nearly disposed. Thus, the apparatus 403 has high
mounting performance to the wheel hub, so that design freedom for
mounting the apparatus 403 on the wheel hub is improved.
[0183] Further, the apparatus 403 can detect a rotation of a wheel
of an automotive vehicle. In this case, the magnetic sensor 401 is
mounted on an engine hood of the vehicle or in a compartment of the
vehicle.
Twelfth Embodiment
[0184] Rotation sensor apparatuses 500, 501 having the magnetic
sensor 401 according to a twelfth embodiment of the present
invention are shown in FIGS. 38A to 38C. Each rotation sensor
apparatus 500, 501 includes the magnetized gear 411a or the
non-magnetized gear 411b as a rotation body 411 as an object to be
detected its rotation, the magnetic sensor 401, a sensor casing 512
for covering the magnetic sensor 401. The sensor casing 512
separates between the rotation body 411 and the magnetic sensor
401.
[0185] The sensor casing 512 covers the magnetic sensor 401, and is
made of magnetic material. The sensor casing 512 includes an
opening 513 disposed between the magnetic sensor 401 and the
rotation body 411. Namely, the opening 513 faces the rotation body
411. In the apparatus 500, 501, the magnetic sensor 401 having high
sensor sensitivity is surrounded by the sensor casing 512 having
high magnetic permeability. Accordingly, the sensor casing 512
partially shields a magnetic field so that influence of disturbance
of an external magnetic field around the magnetic sensor 401 is
reduced. Namely, the apparatus 500, 501 has high resistance against
the outside disturbance of magnetic field.
[0186] The periodic change of the intensity of magnetic field
generated by the rotation of the rotation body 411 is detected by
the magnetic sensor 401 through the opening 513 of the sensor
casing 512. Thus, the magnetic sensor 401 can detect the rotation
of the rotation body 411. Here, since the magnetic sensor 401 has
high sensor sensitivity for detecting magnetic field, the opening
513 of the sensor casing 512 can be minimized as long as the
magnetic sensor 401 detects the periodic change of the intensity of
magnetic field.
[0187] Thus, the apparatus 500, 501 has a simple construction in
such a manner that the sensor casing 512 having a small opening 513
covers the magnetic sensor 401 so that the influence of disturbance
of an external magnetic field around the magnetic sensor 401 is
reduced. Therefore, the manufacturing cost of the apparatus 500,
501 is reduced.
[0188] The apparatus 500, 501 is suitably used for detecting a
rotation of a cam of camshaft in an engine of an automotive vehicle
or a gear of a crankshaft in an engine of a vehicle. Here, there
are many sources to generate disturbance of the external magnetic
field around the engine of the vehicle. Further, the disturbance of
the external magnetic field has a complicated structure. Even when
the apparatus 500, 501 is disposed in such a complicated
disturbance, the influence of disturbance is reduced so that the
apparatus 500, 501 detects the rotation accurately.
[0189] Although the rotation body 411 has a gearwheel shape and is
made of a magnetic material or a material including the magnetic
material, the rotation body 411 can have another shape and be made
of another material. As shown in FIG. 39, a rotation sensor
apparatus 502 has the rotation body 411c. The rotation body 411c
includes a cylindrical magnet. Each of N and S poles of the
cylindrical magnet is alternately disposed on a circumferential
periphery of the cylindrical magnet. The apparatus 502 further
includes the magnetic sensor 401 and the sensor casing 512 having
the opening 513. In the apparatus 502, the sensor casing 512
partially shields a magnetic field so that influence of disturbance
of an external magnetic field around the magnetic sensor 401 is
reduced. Further, the magnetic sensor 401 detects the periodic
change of the intensity of magnetic field generated by the rotation
of the rotation body 411c through the opening 513 of the sensor
casing 512. Thus, the magnetic sensor 401 can detect the rotation
of the rotation body 411c.
[0190] Thus, the apparatus 502 has a simple construction in such a
manner that the sensor casing 512 having the small opening 513
covers the magnetic sensor 401 so that the influence of disturbance
of an external magnetic field around the magnetic sensor 401 is
reduced. Therefore, the manufacturing cost of the apparatus 502 is
reduced.
[0191] The apparatus 502 is suitably used for detecting a rotation
of a magnetized rotor mounted on a rotation shaft of a wheel of an
automotive vehicle. In this case, the apparatus 502 provides a
wheel rotation sensor for ABS of the vehicle. Here, there are many
sources to generate disturbance of the external magnetic field
under a body of the vehicle. Further, the disturbance of the
external magnetic field has a complicated structure. Even when the
apparatus 502 is disposed in such a complicated disturbance, the
influence of disturbance is reduced so that the apparatus 502
detects the rotation accurately.
Thirteenth Embodiment
[0192] A rotation sensor apparatus 503 having the magnetic sensor
401 according to a thirteenth embodiment of the present invention
is shown in FIGS. 40A and 40B. The rotation sensor apparatus 503
includes the rotation body 411 made of a magnetic material or a
material including the magnetic material, the magnetic sensor 401,
and a sensor casing 512a for covering the magnetic sensor 401. The
sensor casing 512a is made of permanent magnet. Both ends of the
sensor casing 512a are opened, and the sensor casing 512a has a
cylindrical shape. One end of the sensor casing 512a has an opening
513a, which faces the rotation body 411. The sidewall of the sensor
casing 512a is formed of the permanent magnet. In the sensor casing
512a, the magnetic sensor 401 is disposed. Specifically, the
magnetic sensor 401 is disposed on the rotation body side, and does
not protrude from the opening 513a of the sensor casing 512a.
[0193] In the apparatus 503, the magnetic sensor 401 having high
sensor sensitivity is surrounded by the sensor casing 512a made of
the permanent magnet. The external magnetic field is prevented from
inserting into the sensor casing 512a except for the opening 513a
because the sensor casing 512a is made of the permanent magnet.
Thus, the sensor casing 512a works as a magnetic shield for
shielding the disturbance of the external magnetic field.
[0194] Further, the sensor casing 512a works as not only a magnetic
shield but also a bias magnet for applying a bias magnetic field
shown as arrows in FIGS. 40A and 40B. The one end of the sensor
casing 512a, at which the opening 513a is disposed, provides one
pole, and the other end provides the other pole. Therefore, the
maximum bias magnetic field is applied toward the rotation body
411. Part of the bias magnetic field penetrates into a cavity of
the sensor casing 512a, so that part of the bias magnetic field
reaches the magnetic sensor 401. When the rotation body 411
rotates, the concavity and convexity disposed on a circumferential
periphery of the rotation body 411 changes the magnetic field lines
of the bias magnetic field periodically. Therefore, the periodic
change of the intensity of magnetic field in accordance with the
rotation of the rotation body 411 affects the bias magnetic field
penetrated in the cavity of the sensor casing 512a. Thus, the
magnetic sensor 401 detects this periodic change of the intensity
of magnetic field, so that the apparatus 503 detects the rotation
of the rotation body 411.
[0195] The periodic change of the intensity of magnetic field in
accordance with the rotation of the rotation body 411 can be
enlarged by controlling the bias magnetic field of the permanent
magnet composing the sensor casing 512a, even in a case where the
rotation body 411 is not magnetized so that no magnetic field is
generated by the rotation body 411. Therefore, the magnetic sensor
401 can detect the rotation accurately.
[0196] With using the rotation sensor apparatus 503 having the
sensor casing 512a made of the permanent magnet, detection accuracy
for detecting the rotation is improved. Here, when the opening 513a
becomes small, the bias magnetic field is difficult to penetrate
into the cavity of the sensor casing 512a. However, the magnetic
sensor 401 with the magnetic impedance device has high sensor
sensitivity for detecting the magnetic field, so that the opening
513a of the sensor casing 512a can be minimized as long as the
magnetic sensor 401 detects the periodic change of the intensity of
magnetic field.
[0197] Thus, the apparatus 503 has a simple construction in such a
manner that the sensor casing 512a having the small opening 513a
covers the magnetic sensor 401 so that the influence of disturbance
of an external magnetic field around the magnetic sensor 401 is
reduced. Therefore, the manufacturing cost of the apparatus 503 is
reduced.
[0198] The apparatus 503 is suitably used for detecting a rotation
of a cam of camshaft in an engine of an automotive vehicle or a
gear of a crankshaft in an engine of a vehicle.
[0199] Although the apparatus 503 includes the rotation body 411,
the apparatus 503 can have another type of rotation body such as
the rotation body 411c, of which N and S poles are disposed
alternately on a circumferential periphery thereof. In this case,
the sensor casing 512a is not required to work as a bias magnet.
Therefore, the sensor casing 512a merely works as a magnetic
shield. In this case, the apparatus 503 provides a wheel rotation
sensor for ABS of the vehicle.
[0200] Such changes and modifications are to be understood as being
within the scope of the present invention as defined by the
appended claims.
* * * * *