Magnetic impedance device, sensor apparatus using the same and method for manufacturing the same Number:7,417,269 from the United States Patent and Trademark Office (PTO) owispatent 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.<H manufacturing, apparatus, Magnetic, impeda, 7417269.html, Patent, pto, 7417269

Title: 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.

Patent Number: 7,417,269 Issued on 08/26/2008 to Ao, et al.

Inventors: Ao; Kenichi (Tokai, JP), Suzuki; Yasutoshi (Okazaki, JP), Yamadera; Hideya (Nagoya, JP), Ohta; Norikazu (Aichi-gun, JP), Funahashi; Hirofumi (Nagoya, JP)
Assignee: DENSO CORPORATION (Kariya, JP)

Appl. No.: 10/717,902

Filed: November 21, 2003

Foreign Application Priority Data


Nov 21, 2002 [JP]			2002-337416
Nov 21, 2002 [JP]			2002-337417
Mar 05, 2003 [JP]			2003-058899
Mar 05, 2003 [JP]			2003-058900
Mar 18, 2003 [JP]			2003-073900

Current U.S. Class: 257/241 ; 257/E27.046

Current International Class: H01L 27/148 (20060101); H01L 29/768 (20060101)

Field of Search: 257/E27.046,E23.008,E23.011,241,421,295

References Cited [Referenced By]

U.S. Patent Documents


4276555	June 1981	Vinal
5471084	November 1995	Suzuki et al.
5637995	June 1997	Izawa et al.
5781005	July 1998	Vig et al.
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5889403	March 1999	Kawase
6232767	May 2001	Kawase et al.
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Foreign Patent Documents


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A-06-324061	Nov., 1994	JP
A-H07-099114	Apr., 1995	JP
A-H07-249517	Sep., 1995	JP
A-H08-75835	Mar., 1996	JP
A-08-178937	Jul., 1996	JP
A-H09-063843	Mar., 1997	JP
A-09-329619	Dec., 1997	JP
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A-11-230782	Aug., 1999	JP
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A-2001-221839	Aug., 2001	JP
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A-2001-289929	Oct., 2001	JP
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A-2003-056378	Feb., 2003	JP
WO00/25371	May., 2000	WO

Other References

Notice of Preliminary Rejection from Korean Patent Office issued on Apr. 21, 2006 for the corresponding Korean patent application No. 10-2006-0008570. cited by other .
Decision for Refusal from Japanese Patent Office issued on Nov. 21, 2006 for the corresponding Japanese patent application No. 2003-058899. cited by other .
Decision for Refusal from Japanese Patent Office issued on Nov. 21, 2006 for the corresponding Japanese patent application No. 2003-058900. cited by other .
Notice of Reason for Refusal from Japanese Patent Office issued on Aug. 29, 2006 for the corresponding Japanese patent application No. 2003-058900. cited by other .
Notice of Reason for Refusal from Japanese Patent Office issued on Sep. 5, 2006 for the corresponding Japanese patent application No. 2003-058899. cited by other .
Office Action issued from Korean Patent Office issued on Oct. 31, 2005 for the corresponding Korean patent application No. 2003-0082788. cited by other .
Office Action and its translation from Chinese Patent Office dated Aug. 5, 2005. cited by other .
Notice of Reason for Refusal from Japanese Patent Office issued on Dec. 26, 2006 for the corresponding Japanese patent application No. 2003-073900. cited by other .
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Notice for Reasons of Refusal dated Feb. 15, 2008 in corresponding Japanese Patent Application No. 2002-337417 (and English translation). cited by other .
Decision of Refusal issued May 27, 2008 in corresponding Japanese Patent Application No. 2002-337416 (English translation attached). cited by other .
Decision of Refusal issued May 27, 2008 in corresponding Japanese Patent Application No. 2002-337417 (English translation attached). cited by other.

Primary Examiner: Lindsay, Jr.; Walter
Attorney, Agent or Firm: Posz Law Group, PLC

Claims

What is claimed is:

1. A magnetic sensor apparatus comprising: a semiconductor substrate; a magnetic impedance device for detecting a magnetic field, the magnetic impedance device is disposed on the substrate; and a periphery circuit disposed on the substrate for processing an output signal outputted from the magnetic impedance device, wherein the magnetic impedance device is made of Ni--Fe series alloy.

2. The apparatus according to claim 1, further comprising: a wiring layer made of aluminum material, wherein the wiring layer connects to both ends of the magnetic impedance device, and wherein the wiring layer has a pair of ends, which is disposed on a connection portion between the wiring layer and the magnetic impedance device.

3. The apparatus according to claim 2, wherein each end of the wiring layer has a tapered shape.

4. The apparatus according to claim 2, further comprising: a barrier metal film made of titanium material, wherein the wiring layer connects to both ends of the magnetic impedance device through the barrier metal film.

5. The apparatus according to claim 2, further comprising: a metallic film, wherein the wiring layer connects to both ends of the magnetic impedance device through the metallic film.

6. The apparatus according to claim 5, further comprising: an interlayer insulation film, wherein the interlayer insulation film is disposed between the magnetic impedance device and the metallic film.

7. The apparatus according to claim 5, wherein the metallic film is made of titanium material.

8. The apparatus according to claim 5, wherein the metallic film is made of aluminum material, copper material, mixture of aluminum and titanium materials, or mixture of copper and titanium materials.

9. The apparatus according to claim 1, further comprising: a stress relaxation layer disposed between the substrate and the magnetic impedance device, wherein the stress relaxation layer reduces a stress generated in the substrate in a case where the apparatus is processed in a heat treatment.

10. The apparatus according to claim 9, wherein the stress relaxation layer is made of poly-imide.

11. The apparatus according to claim 1, further comprising: an oxidation protection film disposed on the magnetic impedance device.

12. The apparatus according to claim 11, wherein the oxidation protection film is made of silicon oxides, silicon nitrides, or composite film of silicon oxides and silicon nitrides.

13. A magnetic sensor apparatus comprising: a semiconductor substrate; a magnetic impedance device disposed on the substrate for detecting a magnetic field, 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 filed 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, wherein 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, 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 thickness L3 is equal to or larger than 5 .mu.m.

14. The apparatus according to claim 13, 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 %.

15. The apparatus according to claim 13, wherein the magnetic layer has a square shaped cross-section, which is disposed perpendicular to the energization direction of the alternating current applied to the magnetic layer, and wherein the square shaped cross-section has one side and the other side, an angle of which is in a range between 60.degree. and 120.degree..

16. The apparatus according to claim 13, wherein the Ni--Fe series alloy film has a plurality of grains, dimensions of which are in a range between 1 nm and 1 .mu.m.

17. The apparatus according to claim 13, wherein the magnetic layer is disposed on the substrate with or without a buffer layer therebetween, and wherein the substrate has a surface roughness, which is equal to or smaller than 1 .mu.m.

18. The apparatus according to claim 13, wherein the magnetic layer has an axis of easy magnetization, which is substantially parallel to or perpendicular to the energization direction of the alternating current.

19. The apparatus according to claim 13, further comprising: a protection layer for covering the magnetic layer, wherein the protection layer is made of electrically insulation material.

20. The apparatus according to claim 19, wherein the protection layer has a compression stress as an internal stress, the compression stress being equal to or smaller than 500 MPa.

21. The apparatus according to claim 19, wherein the protection layer has a tensile stress as an internal stress, the tensile stress being equal to or smaller than 100 MPa.

22. The apparatus according to claim 19, wherein the protection layer has a thickness in a range between 0.2 .mu.m and 5 .mu.m.

23. The apparatus according to claim 19, wherein the protection layer is made of at least one of materials selected from the group consisting of silicon nitrides, aluminum nitrides, silicon oxides, phosphorized silicon oxides, and boron-doped silicon oxides.

24. The apparatus according to claim 19, wherein the protection layer is made of a composite material having a plurality of insulation materials.

25. The apparatus according to claim 19, wherein the protection layer has a laminated structure.

26. A magnetic sensor apparatus comprising: a semiconductor substrate; a magnetic impedance device disposed on the substrate for detecting a magnetic field, 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 filed 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 width L2 is in a range between 5 .mu.m and 100 .mu.m, the thickness L3 is equal to or larger than 0.3 .mu.m.

27. The apparatus according to claim 26, 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

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

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

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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:

FIG. 1 is a plan view showing a magnetic impedance device according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional view showing the device taken along line II-II in FIG. 1;

FIG. 3 is a cross-sectional view showing the device taken along line III-III in FIG. 1;

FIGS. 4A to 4C are cross-sectional views of the device explaining a manufacturing method of the device according to the first embodiment;

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;

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;

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;

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;

FIG. 9 is a table showing the ratio of impedance change .DELTA.Z/Zo in different devices, according to the first embodiment;

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;

FIG. 11 is a table showing the ratio of impedance change .DELTA.Z/Zo in different devices, according to the first embodiment;

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;

FIG. 13 is a table showing the ratio of impedance change .DELTA.Z/Zo in different devices, according to the first embodiment;

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;

FIG. 15 is a table showing the ratio of impedance change .DELTA.Z/Zo in different devices, according to the first embodiment;

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;

FIG. 17 is a table showing the ratio of impedance change in different devices, according to the first embodiment;

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;

FIG. 19 is a plan view showing a magnetic impedance device according to a second embodiment of the present invention;

FIG. 20 is a cross-sectional view showing the device taken along line XX-XX in FIG. 19;

FIG. 21 is a table showing the ratio of impedance change .DELTA.Z/Zo in different devices, according to the second embodiment;

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;

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;

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;

FIG. 25 is a cross-sectional view showing a magnetic sensor apparatus according to a third embodiment of the present invention;

FIG. 26 is an enlarged plan view showing a magnetic impedance device of the apparatus according to the third embodiment;

FIG. 27 is a schematic diagram showing an electric circuit of the apparatus according to the third embodiment;

FIG. 28 is a cross-sectional view showing a magnetic sensor apparatus according to a fourth embodiment of the present invention;

FIG. 29 is a cross-sectional view showing a magnetic sensor apparatus according to a fifth embodiment of the present invention;

FIG. 30 is a cross-sectional view showing a magnetic sensor apparatus according to a sixth embodiment of the present invention;

FIG. 31 is a cross-sectional view showing part of a magnetic sensor apparatus according to a seventh embodiment of the present invention;

FIG. 32 is a cross-sectional view showing a magnetic sensor apparatus according to an eighth embodiment of the present invention;

FIG. 33 is a cross-sectional view showing a magnetic sensor apparatus according to a ninth embodiment of the present invention;

FIG. 34 is a schematic cross-sectional view showing a rotation sensor apparatus according to a tenth embodiment of the present invention;

FIGS. 35A to 35C are schematic cross-sectional views showing part of the rotation sensor apparatus according to the tenth embodiment;

FIG. 36 is a schematic cross-sectional view showing another rotation sensor apparatus according to the tenth embodiment;

FIG. 37 is a schematic cross-sectional view showing a rotation sensor apparatus according to an eleventh embodiment of the present invention;

FIGS. 38A to 38C are schematic cross-sectional views showing a rotation sensor apparatus according to a twelfth embodiment of the present invention;

FIG. 39 is a schematic cross-sectional view showing another rotation sensor apparatus according to the twelfth embodiment; and

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

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.

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.

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.

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.

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.

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..

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.

As shown in FIG. 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. a 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.

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.

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.

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.

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.

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.

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.

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.

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.

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..times..times. ##EQU00001## 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.

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%.

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.

FIG. 7 shows a graph showing a relationship between temperature T and a sensor sensitivity drift

.DELTA..function..DELTA..times..times..DELTA..times..times. ##EQU00002## 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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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%.

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.

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