KR20090029800A - 3 axis thin film fluxgate - Google Patents

Abstract

A 3 axis thin film fluxgate is provided to minimize power necessary for operating an element, thereby measuring a direction of a magnetic field at very high accuracy. A 3 axis thin film fluxgate is made by using a thin film technique and an etching process. A lower coil(13) is formed in a substrate insulating layer on a silicon wafer. A magnetic thin film(10) surrounded by a lower insulating layer(11') and an upper insulating layer(11") is formed. A drive coil(4) and a pickup coil(5) surround an electrically isolated magnetic thin film by the insulating thin film by forming an upper coil(12).

Description

Thin-film 3-axis fluxgates {3 AXIS THIN FILM FLUXGATE}

The present invention relates to a thin film fluxgate capable of measuring a direction in which a fine magnetic field is applied. More specifically, the present invention relates to a three-dimensional measurement of a horizontal biaxial component and a vertical component magnetic field. A triaxial thin film fluxgate that can be used.

Fluxgate is a kind of magnetic sensor, and has been used for the purpose of searching for steel-containing deposits such as land mines, and electronic compasses.

The basic structure of the fluxgate is composed of a ferromagnetic material 2, a drive coil 4 surrounding the periphery thereof, and a separate pickup coil 5, as shown in FIGS. AC power supply (3) for applying the and includes a voltmeter (6) for sensing the voltage induced in the pickup coil.

The principle of operation of fluxgate is as follows. When the drive coil 4 is wound around the ferromagnetic material 2 and an alternating current is applied to the coil, a time-varying induction magnetic field is generated around the coil, particularly in the coil, and the magnetic material is magnetized by the induction magnetic field. This magnetic body becomes an electromagnet having an N pole and an S pole. At this time, since the induction magnetic field has time-varying polarity reversed with time, the magnetic poles of the magnetic body mounted inside the coil are also inverted with time, and the magnetic field formed around the fluxgate by the magnetic body is also time Will be converted according to Induced current is formed in the pickup coil surrounding the magnetic material by the time-varying magnetic field. As a result, in the pickup coil 5, as shown in FIGS. 2, 4, and 5, a voltage peak changes with time. Is detected.

1 is a conceptual diagram illustrating a conventional three-axis fluxgate. The conventional fluxgate has a structure in which three two-bar fluxgates 1 are arranged at right angles to each other in order to measure the direction of an applied magnetic field such as an earth magnetic field. In the operation of the conventional fluxgate as shown in FIG. 1, the drive coil and the pick-up coil are wound around two pairs of magnets in each of X, Y, and Z axes, that is, a pair of rod-shaped magnetic bodies, and then the inside of the drive coil By inputting a triangular wave or sine wave, two magnetic bodies are magnetized in different directions, and in this state, a voltage waveform detected by a pickup coil wound on two magnetic bodies is read. FIG. 2A is a diagram illustrating input voltage waveforms applied to the magnetic material A and the magnetic material B of the two rod-type fluxgates having the structure of FIG. The current input along the same drive coil 4 is applied with a current in the form of magnetizing the magnetic material in different directions in the magnetic materials A and B.

FIG. 2 (b) is a diagram representing a pickup voltage waveform generated at each of A and B magnetic parts in a pickup coil wound around two bar-type fluxgates. The pickup voltage represents an output signal with a different sign as shown in Fig. 2B. As shown in (b) of FIG. 2, the output voltage has the same shape as the input voltage. The conventional products are not thin film products using semiconductor technology, unlike the present invention, and a bulk ferromagnetic rod or ferromagnetic powder in epoxy form is used. This is because the magnetic properties of the magnetic material are not good due to the use of the material using the magnetic material manufactured by binding. Therefore, the magnetization reversal of the magnetic material is not achieved in a perfect form, and it exhibits electrical behavior as a kind of simple transformer (transformer). Conventional products have the characteristics that if the input wave is a triangular pie, the output wave is output as a triangular wave, and if the input wave is a sine pie, the output wave is output in the form of a sine wave.

2 (b) shows an output signal in which no magnetic field is applied from the outside, and two different types of signals are summed through one coil, and thus the state of '0' volts over the entire time interval. Will have (C) of FIG. 2 is a diagram showing an output signal detected in each of A and B constituting the conventional two-bar fluxgate when a magnetic field is applied from the outside. As the external magnetic field is applied, the output voltage signal has a relatively horizontal movement, and thus the output voltage is newly displayed while the voltage is '0'. The conventional fluxgate has a structure in which two bar-shaped fluxgates are arranged for each of the X, Y, and Z axes, and each fluxgate uses a principle that a new output voltage is generated by applying a magnetic field.

The problem of the conventional two-bar fluxgate (1) product having such a principle of operation and structure is that the magnetic properties per X, Y, and Z axes are not good, so that a large size is required and two bulk magnetic materials are required for operation. Since the entire device occupies a large area, the area of the product is not only large, but also a large area fluxgate must be mounted in the Z-axis direction. Therefore, electronic products such as mobile phones requiring small, flat sized electronic compasses Is difficult to mount. In addition, as shown in FIG. 2, since the output signal has a form of a transformer (transformer), a signal processing circuit that needs to cancel each other signal is additionally required, and the two signals of the pick-up signal are attenuated. Because of its small size, there was a problem in that a high-capacity amplifier to remove noise was required.In order to solve such a problem, that is, to increase the output signal, a large amount of current was introduced to the fluxgate operation. Was necessary. The need for large amounts of electricity for accurate azimuth measurements has become a constraint that prevents the deployment of products to mobile devices, such as cell phones, where low power consumption is essential.

Technical challenge

In order to solve the above-mentioned problems of the prior art, the present invention is a thin film type 3 that can be manufactured in a small three-axis fluxgate electronic compass to be mounted in a small electronic device such as a mobile phone, and to minimize the power required for device operation The purpose is to provide an axial fluxgate.

Technical solution

According to the present invention for achieving the above technical problem, in the thin film type three-axis fluxgate for detecting the magnetic field component in the three-axis direction, the two arranged on the same plane as for detecting the horizontal two-axis component of the magnetic field Two horizontal component magnetic flux sensing gates, and a vertical component magnetic flux sensing thin film fluxgate for sensing vertical components of a magnetic field, wherein the vertical component magnetic flux sensing gates comprise the two horizontal component magnetic flux sensing gates Provided is a thin-film three-axis fluxgate disposed substantially orthogonally to each other and having a shorter length than the horizontal magnetic component sensing fluxgate and having a plurality of magnetic thin films having a magnetic structure of "∞" shape in parallel. do.

The thin-film three-axis fluxgate according to the present invention arranges three thin-film fluxgates in three directions of the x, y, and z axes, respectively, to detect both the horizontal component and the vertical component of the magnetic field. Take a configuration to identify the orientation on the earth's surface.

In the triaxial fluxgate of the present invention, the fluxgate for detecting magnetic field components in each direction is manufactured in the form of a thin film. In particular, the thin film fluxgate for detecting the vertical component of the magnetic field can be manufactured in a flat form that can be easily mounted on a small electronic device such as a mobile phone. And a winding of the pickup coil.

Favorable effect

According to the present invention, it is possible to configure a small electronic compass with low power consumption, and particularly embedded in a small portable device such as a mobile phone can measure the direction of the external magnetic field with high accuracy.

1 is a view showing the basic structure of a conventional two-bar fluxgate

2 shows an example of a voltage waveform detected in a pickup coil of a conventional fluxgate.

3 is a view showing the structure of a 1-bar thin film fluxgate according to the present invention;

4 is a view illustrating an operating principle of the thin film fluxgate according to the present invention.

5 is a diagram illustrating a result of a voltage waveform detected by a pickup coil of a thin film fluxgate according to an externally applied magnetic field.

6 is a view showing the structure of a thin film fluxgate for X, Y, Z axes according to the present invention

7 is a view showing the structure of an electronic compass chip manufactured using the thin film fluxgate device for the X, Y, and Z axes according to the present invention.

8 is a view illustrating a magnetic thin film and a winding structure of a fluxgate for X and Y axes according to the present invention.

9 is a view showing an inverse magnetic field generated inside a magnetic thin film constituting a thin film fluxgate for the X and Y axes according to the present invention.

10 is a view illustrating a method of manufacturing a thin film fluxgate for a Z axis according to the present invention.

11 is a view showing the shape of the thin film fluxgate for Z-axis according to the present invention and the internal structure of the magnetic thin film constituting the fluxgate

12 is a view showing the operating principle of the thin film fluxgate for Z-axis in accordance with the present invention

13 is a view showing a change in the output signal according to the shape and configuration of the magnetic film of the thin film fluxgate for Z-axis in accordance with the present invention

<Description of the code | symbol about the principal part of drawing>

1.2 bar type fluxgate

2. ferromagnetic material

3. AC power for drive

4. drive coil

5. Pick-up coil

6. Voltmeter for pick-up

7. Epoxy molding

8. PCB for packaging

9. Silicon wafer

10. Magnetic thin film

11, 11 ', 11 ". Insulation thin film

12. top coil

13. bottom coil

14. Thin Film Fluxgate

15. X-axis thin film fluxgate

16. Y-axis thin film fluxgate

17. Z-axis thin film fluxgate

18.ASIC for fluxgate electronic compass

19. bonding wire

20. pad for wire bonding

21.bottom pad

22. chip height

23. Pick-up area or central area

24. Drive area or outer area

25. Insulation film for magnetic film lamination

26. Groove

27. Magnetic flux in the drive area

28. Magnetic flux in the pick-up area

29. External magnetic field to the pick-up area

30. external magnetic field to the drive area

Best Mode for Carrying Out the Invention

EMBODIMENT OF THE INVENTION Hereinafter, with reference to an accompanying drawing, the structure of this invention is demonstrated in detail.

Figure 3 is a three-dimensional illustration of the rod-shaped thin film fluxgate according to the present invention. In the thin film fluxgate of the present invention, a thin film fluxgate is manufactured by using a thin film technology and an etching process on a silicon wafer 9 coated with an insulating film 11 on a substrate. In order to manufacture the thin film fluxgate, grooves are formed in the insulating film 11 on the silicon wafer to form the lower side of the coil, that is, the half of the coil, and a conductive material such as aluminum is inserted therein to insert the lower coil 13. After fabrication, the magnetic thin film 10 surrounded by the lower insulating film 11 'and the upper insulating film 11' is formed, and the upper coil 12 is finally formed to form the drive coil 4 and the pickup coil 5. The insulating thin films 11 ′ and 11 ″ may surround the magnetic thin film 10 that is electrically isolated.

The detailed structure and cross-sectional structure of the thin film fluxgate according to the present invention are shown in Fig. 3- (b). In order to fabricate the rod-shaped thin film fluxgate, first, the portion of the lower coil 13 formed on the substrate insulating film formed on the silicon wafer 9 is removed by a photolithography process and an etching process to form a groove, and then the lower coil therein. (13) The aluminum and aluminum alloy thin films which are conductive thin films as materials are formed. This is to increase the flatness of the process.

Thereafter, both ends of the lower coil are partially exposed and a primary insulating thin film 11 ′ is formed to cover the entire length direction of the fluxgate. The purpose of not forming an insulating thin film at both ends of the lower coil is to form a winding structure that surrounds the magnetic thin film surrounded by the insulating thin film by interconnecting the end portions in the upper coil manufacturing process, which is the final process. Next, a ferromagnetic thin film 10 having a length and width narrower than that of the insulating thin film 19 and having a stacked structure is formed, and subsequently, a secondary insulating thin film, ie, an upper insulating thin film, for preventing a short circuit between the upper coil and the ferromagnetic material. (11 "). Thereafter, the upper coil 12 thin film is formed and the terminals of the upper coil end are connected to the terminals of the lower coil 13, which is formed in advance, so that the two types of coils surround the magnetic thin film. To complete the production of rod-shaped thin film fluxgate.

In order to manufacture the thin film fluxgate of the present invention, the lower coil thin film 13, the primary insulating thin film 11 ′, the magnetic thin film 10, the secondary insulating thin film 11 ″ and the upper coil thin film 12 are sequentially formed. In order to secure mechanical properties for electrical and crack prevention, each thin film needs to be formed, and a specific material is required and a magnetic thin film 10 having a laminated structure needs to be formed. In order to remove the stress generated in the whole, the material of the primary insulating thin film 11 ′ has a higher impact resistance toughness than conventional insulator thin films such as Ta ₂ O ₅ , Al ₂ O ₃ , TiO ₂ , and the like. By using SiO ₂ , the magnetic properties of the magnetic thin film 10 formed on the primary insulating thin film were improved, and in order to maintain excellent magnetic properties, the thickness of the primary insulating thin film 11 ′ was at least 5,000 μs. Formed with a thickness of more than C. The thickness of the primary insulating thin film 11 'has the best magnetic properties within the thickness range of 5,000 Å (0.5 탆) to 20,000 Å (2 탆). The magnetic thin film 10 has low coercivity, high permeability, fast saturation magnetization, that is, magnetic properties required as a fluxgate magnetic thin film, that is, a magnetic hysteresis curve of the magnetic material. The width of the loop should be narrow and have a high squareness of square shape To manufacture a magnetic thin film having such magnetic characteristics, it is difficult to form a single layer magnetic thin film. It is preferable to fabricate in the form of a laminated thin film which is alternately formed with the Al ₂ O ₃ insulator thin film 25. The thicknesses of the NiFe ferromagnetic thin film and the Al ₂ O ₃ insulator thin film constituting the laminated thin film are 600 Å ± 300 Å, 1, respectively. Magnetic properties suitable for thin film fluxgates within a thickness range of 50 ± 100Å. When the laminated thin film is formed of the magnetic thin film and the insulating thin film under the above thickness condition, the magnetic history curve has a narrow rectangular shape. In order to increase the magnitude of the output voltage generated in the thin film fluxgate, to make it easy to detect with a dedicated circuit, the number of layers of the magnetic layers may be increased. In order to increase the total amount of the magnetic material, when the NiFe ferromagnetic thin film and the Al ₂ O ₃ insulator thin film are referred to as a pair, it is preferable to form at least three pairs of laminated films.

3C is a diagram illustrating a winding state of the rod-shaped thin film fluxgate. As shown in the figure, the drive coil 4 and the pickup coil 5 have a structure surrounding the magnetic thin film 10 at the same time. In order to operate the fluxgate, an alternating current flows through the drive coil 4, and the magnetic field of the solenoid coil in the left and right directions generated when the alternating current flows through the coil causes the magnetization direction of the magnetic thin film mounted inside the coil. It should change from side to side. Under the above circumstances, that is, when the magnetization direction of the magnetic material is changed by the drive coil, an independent volt peak of the form shown in Figs. 4D and 4F appears in the pickup coil.

4 is a view illustrating a principle in which the shape of an output signal in the thin film fluxgate is generated in the form of an isolated peak or independent voltage. The appearance of independent peaks through the pickup coil sensing the output signal is closely related to the magnetic properties of the magnetic thin film constituting the fluxgate. When the magnetic behavior of the magnetic thin film manufactured for the fluxgate has the excellent magnetic history curve of the angular ratio as shown in FIG. 4 (c), the triangular wave or the sine wave input to the drive coil of the fluxgate is surrounded by the drive coil. Magnetic field is periodically applied to the magnetic material. The input AC causes the magnetic behavior of ① to ⑦ indicated in (c) of FIG. 4. The dotted line in FIG. 4 (c) shows the magnetic behavior when an AC signal is applied to the thin film fluxgate in the absence of an external magnetic field such as the earth's magnetic field, and the output peak is shown in FIG. 4 (d) in the form of a dotted line. At this time, the position where the independent peak appears is coincident with the A extension line shown in the figure. In addition, the position at which the output peak of the minus sign appears is shown at the B (B ') extension line position shown in the drawing. The dotted line of FIG. 4 (f) also shows the position where the voltage peak appears in the absence of an externally applied magnetic field. Independent peaks appear where magnetization reversal occurs because the output volts are directly proportional to the magnetizing value that changes over time, ie (d (M) / dt). The solid line of FIG. 4C is a diagram showing a change in magnetic behavior when a magnetic field is applied from the right side in a state where the bar-shaped fluxgate is placed horizontally as shown in FIG. 4A. When the magnetic field of the DC component such as the earth's magnetic field is applied on the right side, the magnetic hysteresis curve shifts to the left side. As described above, when an AC input current flows through the drive coil under an external magnetic field applied, the solenoid magnetic field is alternately formed in the drive coil side by side according to the current flow of the drive coil. In this case, since the magnetic hysteresis curve is shifted to the left side, if the magnetization reversal occurs under the same time reference, the generation of the volt peak has a different behavior than when there is no applied magnetic field. The generation of the peak of the (+) output volt as it moves from the (-) magnetization state to the (+) magnetization state occurs in a shorter time than in the absence of an applied magnetic field and moves from the (+) magnetization state to the (-) magnetization state. As a result, the negative output volt is generated later. As a result, the distance between the output peaks has a wider peak-to-peak distance than when there is no externally applied magnetic field. 4 (e) and 4 (f) are diagrams showing a shape in which an output peak appears when an external magnetic field is applied from the left side of the fluxgate lying horizontally as shown in FIG. 4 (b). In contrast to the previous case, the spacing between output peaks is reduced.

Unlike the conventional two-bar fluxgate (1), the reason why the three-axis fluxgate can be manufactured using only one magnetic rod is a ferromagnetic thin film having a narrow and square magnetic hysteresis curve using magnetic thin film technology. It is because it is possible to manufacture (10). The ferromagnetic material employed in the conventional fluxgate does not have a rectangular magnetic hysteresis curve as shown in FIG. 4, and the magnetic hysteresis curve is long divided according to the applied magnetic field (H). It takes more time to change to, so that no isolated volt peaks appear, and it works like a kind of transformer, so that it has an output signal of a triangular wave or sine wave of the form as in 2 (a). Fluxgate using the distance measuring method between independent peaks as in the present invention could not be manufactured.

Since the present invention has an output signal as shown in FIGS. 4 (d) and 4 (f), that is, it has a characteristic of generating independent volt peaks, it is possible to measure the position of the output volt peaks, and these peaks are externally applied. Since the peak shift occurs in proportion to the change in the direction and magnitude of the magnetic field, it is possible to measure the direction of the externally applied magnetic field such as the earth's magnetic field by using a distance measuring method (actually time) of two independent peaks. Do.

FIG. 5A illustrates a state when the thin film fluxgate faces a specific direction with respect to an external magnetic field, and FIGS. 5B, 5C, and 5D show directions in which the thin film fluxgate faces. It is a figure which shows the change aspect of an output signal. In the case where the thin film fluxgate is disposed eastward or westward, there is no magnetic field acting in the longitudinal direction of the thin film fluxgate, so the output peak of the thin film fluxgate is positive in the absence of an externally applied magnetic field. ) Output peaks appear and the distance between the peaks has a distance of 'E' μsec or 'W' μsec as shown in FIG. If the thin film fluxgate faces north, a magnetic field is applied in the longitudinal direction from the bottom of the fluxgate element so that the distance between the output volt peaks is reduced to 'N' μsec as shown in FIG. In the case of, the distance between the output peaks is increased to 'S' μsec as shown in FIG. As such, when an external magnetic field is applied, a peak shift phenomenon occurs in which the voltage peak is shifted left and right, and as shown in FIG. 5, when there is no external magnetic field other than the geomagnetic field, By analyzing the degree of peak shift, it is possible to accurately determine the existence of an external magnetic field and the direction in which the magnetic field is applied. The reason why the isolated peak appears in the output signal of the fluxgate according to the present invention is that the distance between the coil and the magnetic body surrounding the magnetic body is significantly larger than that of the bulk product by using the thin film technology using the semiconductor technology to manufacture the fluxgate according to the present invention. It is possible to lower the magnetization and magnetization reversal of the thin magnetic film with a small current drawn into the drive coil, and the generation of fine voltage according to the magnetization reversal result is more accurate than that of the bulk-assembled product. Because it can be read.

6 (a) and 6 (b) show the X- and Y-axis single-bar type thin film fluxgates according to the present invention, and FIGS. 6 (c) and 6 (d) show the Z-axis fluxgates. 6A is a thin film fluxgate having a structure in which a drive coil and a pickup coil are alternately wound around a rod-shaped magnetic thin film, and FIG. 6B is an improved electrical characteristic compared to FIG. 6A. It is a thin film fluxgate for X and Y axes with magnetic thin film design and winding structure. The thin film fluxgate for X and Y axes of FIG. 6 (b) has a design in which grooves are formed at the end portions of the magnetic thin film in the form of dumbbells, and the winding structure does not alternately wind the drive coil and the pickup coil for each line. The drive coil is wound by a certain number of turns, and then the pick-up coil is wound by an amount of turns. FIG. 6C is a view showing the configuration of a Z-axis thin film fluxgate having a structure in which a drive coil and a pickup coil are alternately wound on a line of a magnetic thin film having a rod length, and FIG. Z is a thin film fluxgate for Z-axis having a magnetic thin film design and a winding structure having improved electrical characteristics as compared to FIG.

The magnetic thin film constituting the thin film fluxgate for the Z-axis is manufactured to have an "∞" structure, and the drive and pickup coils required for the fluxgate operation are separately wound in different regions without winding in the same region. Has The drive coil 4 concentrates and winds the round portions 10 'on both outer sides of the magnetic thin film constituting the Z-axis element, and the pick-up coil concentrates and winds the magnetic straight portion 10 in the center. On the other hand, the use of winding the drive coil of a certain number of windings at both ends of the center portion where the pickup coil is wound also helps to improve the magnitude of the output peak because it helps to make the direction of the magnetic flux in the center portion in one direction. Increasing the number of turns of the drive in the same pick-up area 10 causes a decrease in the number of turns of the pick-up coil 5, thereby reducing the size of the overall peak. desirable.

The end portion of the central portion 10 of the magnetic thin film of the thin film fluxgate for Z-axis also has grooves formed in the same manner as the magnetic thin film structure of the thin film fluxgate for X and Y axes of FIG. The thin film fluxgate for Z-axis of FIG. 6 (d) is used to determine the thickness of the entire electronic compass chip when the Z-axis fluxgate is erected perpendicularly to the packaging PCB 8 for mounting on a mobile device such as a mobile phone. The overall height of the thin film fluxgate should be as small as possible while the output volt peaks resulting from it should be as large as possible. Therefore, in the present invention, a plurality of short-length fluxgates having a size of at least 0.9 mm or less are arranged, and a thin film fluxgate for Z-axis having a structure in which a drive coil and a pickup coil are connected to one drive coil and one pickup coil is connected thereto. When the fluxgate is formed in the shape of the present invention and electricity flows through the drive coil, magnetization reversal occurs in the same direction at the same time in the plurality of magnetic thin films, so that one pick-up coil is generated in the thin film fluxgate of each small size. Since the pickup bolts are summed up, the size of the isolated peaks necessary to detect the externally applied magnetic field appears to be large enough for the orientation determination.

7 (a) is a view showing the structure of an electronic compass chip employing a novel type of thin film fluxgate according to the present invention. In the present invention, the arrangement of one fluxgate on each axis of X, Y, and Z is no different from the conventional method, but is different from the conventional method employing a two-bar fluxgate per axis. It has a structure in which a gate is arranged, and in order to make a thin-walled electronic compass chip, a structure in which a plurality of fluxgates having a shape having a “∞” shape of magnetic thin film is arranged in parallel in the Z-axis fluxgate is used. In order to measure the magnetic field of the vertical component (Z-axis component), the height of the thin film divided into plural pieces is formed to be shorter than the length of the horizontal component (X-axis and Y-axis) fluxgate so that the overall shape of the three-axis fluxgate is flat. It is possible to produce.

FIG. 7B is a diagram showing a cross-sectional structure of an electronic compass chip having three axes of fluxgates mounted thereon. In order to mount an electronic compass chip in a mobile device such as a mobile phone, the chip must be smaller than the maximum allowable height of 1.4mm and be made as thin as possible. The configuration of the electronic compass chip is to place various elements constituting the electronic compass on the packaging PCB (8), and to connect the respective electrical terminals 20 using a wire (19), and then to protect the epoxy molding (element) on the 7) has a configuration to implement. One important point here is to reduce the height of the entire chip as much as possible. Factors constituting the overall height of the chip are the thickness of the PCB, the height of the fluxgate for the Z axis, the thickness of the epoxy molding and the thickness of the bottom pad. The height control of the X, Y-axis fluxgate and ASIC devices can be greatly reduced by grinding the back side of the silicon wafers from which they are fabricated, so there is no problem in reducing the overall thickness of the chip. Normally, PCB uses 0.15mm ~ 0.2mm rigid PCB, and the thickness of epoxy molding on the top is usually 0.10mm ~ 0.15mm, so in order to make the total chip size below 1.2mm, the height of Z-axis thin film fluxgate is increased. It should be manufactured at least 0.95mm to 0.85mm or less, and it is desirable to make it smaller than 0.85mm to further lower the overall chip height.

Figure 8 (a) is a view showing the thin film flux gate for the X-axis and Y-axis in accordance with the present invention produced in the form of a dumbbell wider than the central portion of the coil coil wound both ends of the magnetic thin film 10 is not wound In addition, it has a magnetic thin film structure for forming a concave groove 26 in the central portion of the end. As shown in FIG. 8A, the winding of the coil required to operate the thin film fluxgate has a structure in which the drive coil is wound between drive coils and the pickup coil is wound between pickup coils. At this time, the line width of the used winding is manufactured to 7 ± 2 ㎛, and the number of windings for each winding area should have more than 10 turns and less than 30 turns. The wire width of the winding is limited because a lot of power is consumed in operating the thin film fluxgate as a large amount of current flows through the thick wire when a wide wire width is used. There is a limit to use because when using a thin wire, the resistance of the coil itself becomes large so that a current that can generate a sufficient magnetic field to magnetize the magnetic thin film cannot flow into the wire. It is desirable to have as close a winding as possible to have as many turns as possible.

FIG. 8B is a view showing a thin film fluxgate having a length of 2.2 mm, and FIG. 8C shows that an AC input voltage of ± 2 volt is applied to a drive coil of the thin film fluxgate of FIG. 8B. Is a diagram showing an output signal output along the pickup coil at the time. The magnitude of the volt peak output from the thin film fluxgate according to the present embodiment is about 10 mV. The output size of 10 mV is based on the fact that the output volt is large enough to detect an output signal in a general driving circuit 18. When the output signal is small, the performance of the driving ASIC 18 is improved. It is also possible to produce an electronic compass. In the thin film fluxgate having the shape of (b) of FIG. 8, the chip width of the entire electronic compass may be manufactured in the form of 4 mm x 4 mm.

8 (d) is a flux gate for horizontal magnetic field sensing in which a drive coil and a pickup coil are separately wound on a dumbbell-type magnetic thin film having both end grooves according to the present invention, and FIG. This figure shows the magnitude of the output voltage and has an output volt peak of 13mV level which is 30% higher than the simple rod-type thin film fluxgate.

The thin film fluxgate of FIG. 8 (d) has sufficient magnetization reversal of the magnetic thin film even at a smaller device size and a smaller number of turns, compared to the thin film fluxgate design of FIG. 8 (b). The size of the output also has a high output volt peak of about 30%. The winding structure of FIG. 8A detects a large output in comparison with the number of small pickup coils, in the case of the structure in which the drive coil and the pickup coil are wound alternately, the magnetization of the magnetic thin film through the drive coil is not easy. This is because the magnetization of the magnetic thin film by the drive coil is relatively easy by winding the drive coil in the same area.

FIG. 9 is a view for explaining the effect of demagnetizing fields occurring in the magnetic bodies and the characteristic differences between the two types of magnetic thin film shapes shown in FIG. 8. In the case of a simple rod-shaped magnetic thin film as shown in FIG. 9A, when a current flows through a drive coil, a magnetic thin film causes magnetization in a direction of applying a magnetic field due to a magnetic field generated by current flow, thereby forming spins of atoms constituting the magnetic body. As the spin is aligned, a magnet is formed instantaneously, and once the magnet is formed, a magnetic force line is formed from the magnetic pole toward the other magnetic pole. These lines of magnetic force are simultaneously formed not only outside the magnet but also inside the magnet to form a line of magnetic force that penetrates inside the magnet and faces the opposite magnetic pole. This is called an inverse magnetic field, and its occurrence disturbs the direction of magnetization at both ends of the magnet, thus reducing the area of uniform magnetization in the entire magnet rod. This reverse field occurs largely at the anode, or end, of the magnetic material. When it reaches the center of the magnetic material, it is almost '0'. The effect of the reverse magnetic field is relatively larger as the length of the thin film fluxgate becomes shorter, so as the fluxgate is made smaller, the portion contributing to the complete magnetization reversal is continuously reduced, and the magnitude of the output peak through the pickup coil is reduced. . On the other hand, the longer the fluxgate is, the larger the output size becomes, but the size of the entire electronic compass becomes larger at the same time, making the thin film fluxgate as small as possible within the range that the dedicated circuit used for the electronic compass can analyze. It is necessary to do

Figure 9 (b) is a view showing the magnetization form of the dumbbell-shaped magnetic thin film formed with grooves at both ends of the magnetic thin film according to the present invention. Increasing the size of both ends occurs a large stimulus is formed over a large area, and if the groove is made in addition to this, the position of the reverse magnetic field is spread to both ends of the dumbbell form. Therefore, the size of the reverse magnetic field generated in the magnetic thin film having the shape of FIG. 9 (b) is reduced than the size of the reverse magnetic field generated from the magnetic material of the simple rod-shaped (a) shape. The reason why the output signal of the dumbbell-type thin film fluxgate having grooves at both ends according to the present invention is increased is that the reduction of the reverse magnetic field according to the above description according to FIG. 9 has a great effect.

10 is a view illustrating a method of manufacturing a Z-axis thin film fluxgate according to the present invention. The Z-axis thin film fluxgate is manufactured in the order of the lower coil, the insulating thin film, the magnetic thin film, the insulating thin film, and the upper coil in the same order as the X and Y-axis thin film fluxgate. Although manufactured separately, the method of making the boundary of the two magnetic thin films overlap.

10A is a view showing a state in which the lower coil 4 for a drive coil and the lower coil 5 for a pickup coil are formed on a silicon wafer surface.

FIG. 10B is a view showing a state where an insulating thin film 11 'is formed to prevent a short circuit between the lower coil and the magnetic thin film in a portion where the magnetic thin film is raised.

10C is a diagram in which a magnetic thin film for use in the pickup region 23 is formed, and FIG. 10D is a view in which a magnetic thin film for use in the drive region 24 is formed. In manufacturing the magnetic thin film, it is necessary to overlap the boundary between the magnetic thin film formed in the pickup region and the magnetic thin film formed in the drive region in order to connect the magnetic paths of the magnetic thin films constituting the Z-axis thin film fluxgate. .

FIG. 10E illustrates a state in which the upper insulating thin film 11 is formed for the purpose of preventing an electrical short circuit between the magnetic thin film that has been formed and the upper coil that is finally formed.

FIG. 10 (f) is a view showing a state in which an upper coil formed for the purpose of connecting the drive coil 4 and the pickup coil 5 formed in the lower half at the top as shown in FIG. 10 (a) is formed. .

11 is a view showing the structure and configuration of an ultra-short Z-axis thin film fluxgate according to the present invention. FIG. 11A is a diagram showing the structure of the magnetic thin film and the winding structure of the thin film fluxgate for Z-axis. The magnetic thin film of the Z-axis thin film fluxgate has a basic structure of “∞” shape, and the magnetic thin film is divided into a portion 23 formed in a straight line at the center and a portion 24 formed in a curved shape at the outside. Is manufactured to have a structure of a laminated magnetic thin film of another type.

Meanwhile, the coil 4 for driving the magnetic thin film is concentrated on the curved portion 24 of the outer portion, and the pickup coil 5 has a structure that is concentrated on the straight portion 23 of the center. At this time, it is necessary for each winding to have the length direction of each winding be wound as perpendicular to the length direction of the magnetic thin film as possible. The winding 5 of the pick-up area is wound in parallel as shown in FIG. 11A, and the winding 4 of the drive area is wound radially along the curved drive area.

The magnetic field lines necessary for inversion of magnetization in the magnetic thin film inside the magnetic pick-up portion 23 that detect the magnetization reversal are not generated at the pick-up portion, but the magnetic flux generated in the outer drive region 24 (27 in FIG. 12) is magnetically generated. It has a structure that flows into the connected pick-up area 23. That is, the magnetic flux (27 in FIG. 12) generated in accordance with the alternating current flowing into the drive coil 4 wound around the outer portion flows into the pick-up area 23 of the Z-axis thin film fluxgate to magnetize in the pick-up area. Try to cause reversal. At this time, the pickup coil 5 wound around the center pickup region 23 detects the magnetization reversal of the center region.

FIG. 11B is a diagram showing the internal structure of the magnetic thin film constituting the thin film fluxgate for Z-axis. The magnetic thin films constituting the pickup region 23 and the drive region 24 are each formed of a magnetic thin film having a laminated structure, but it is important that the detailed configuration has a different structure. The central region 23 is required to be manufactured in the same form as the laminated structure of the thin film fluxgate for X-axis. The central region was manufactured in the form of a laminated thin film in which the NiFe magnetic thin film 10 was alternately formed with the Al ₂ O ₃ insulating thin film 25. The thicknesses of the NiFe ferromagnetic thin film and the Al ₂ O ₃ insulator thin film constituting the laminated thin film are within the thickness range of 600Å ± 300Å and 150Å ± 100Å, respectively, and the outer region is formed of the laminated magnetic thin film composed of the same material. It should give a change in thickness. In order to satisfy pickup bolt generation of 10 mV or more and measurable peak shift simultaneously, the thicknesses of the NiFe ferromagnetic thin film and Al ₂ O ₃ insulating thin film formed in the outer region 24 are 1800Å ± 200Å and 150Å ± 100Å, respectively. It should be formed within the thickness range of. In addition, the overall height of the Z-axis thin film fluxgate is maintained to be 0.9 mm or less, and the three Z-axis thin film fluxgates are connected in parallel to form a total pickup bolt size of at least 10 mV or more at an input voltage of ± 2 volt. It is necessary to form a stack of magnetic thin films of the central portion 23 in the form of a laminated film of at least eight layers (eight magnetic thin films + seven intermediate insulating thin films), and the outer portion 24 has at least three layers stacked. It is necessary to form a film.

The output peak can be generated even if the magnetic thin film is formed smaller than this thickness and structure, but in this case, the output signal of the Z-axis thin-film fluxgate is reduced, and it is necessary to greatly improve the performance of the electronic compass driving circuit. Lose. In addition, in order to increase the output size, it is possible to make a Z-axis element by connecting as many unit units as possible in parallel to the Z-axis thin film fluxgate manufactured in a short size, but in this case, the total length of the Z-axis thin film fluxgate is possible. Is increased, making it difficult to manufacture a small sized compass chip. 11C shows at least 5 windings and up to 10 windings of drive coils having a 5 to 9 탆 line width at both ends of the pickup region 23 for the purpose of contributing to the magnetization reversal of the pickup region 23. A diagram showing a Z-axis thin film fluxgate employing a winding method. The additional placement of drive coils at both ends of the pickup area contributes to the enhancement of the output peak size. However, an increase in the number of windings of the drive coil in the limited pick-up area causes a decrease in the number of windings of the pick-up coil. Therefore, it is not desirable to form a drive coil of 10 turns or more at both ends of the pick-up area. FIG. 11D is a diagram showing a structure obtained by dividing the middle portion of the pick-up area vertically. This configuration of the magnetic thin film has a feature that can arbitrarily widen the area of the magnetic thin film participating in the pickup without increasing the number of turns of the pickup coil.

12 is a view showing the operating principle of the thin film fluxgate for Z-axis in accordance with the present invention. FIG. 12 (a) is a view showing that the entire magnetic thin film constituting the thin film fluxgate for Z-axis is manufactured in the same laminated structure, and FIG. 12 (c) shows the thin film fluxgate for Z-axis manufactured with the same thin film. It is a figure which shows the magnetic characteristic which the magnetic thin film of the pickup area | region 23 and the drive area | region 24 have. Each region is formed of the same magnetic thin film stack structure and thus has the same hysteresis loop.

12B is a view showing a Z-axis element having a configuration in which the magnetic thin film constituting the Z-axis thin film fluxgate is divided into a pickup area 23 and a drive area 24, respectively, and has a different stacked structure. FIG. 12 (d) is a diagram showing magnetic hysteresis curves in which two types of slopes are different due to formation of different laminated films in respective regions.

NiFe ferromagnetic thin film and the Al ₂ O ₃ thickness of the insulating thin film at the pickup region (23) is composed of each of 600Å ± 300Å, 150Å ± 100Å, in the drive region 24 of NiFe ferromagnetic thin film and the Al ₂ O ₃ insulator thin film The thickness is 1800Å ± 200Å and 150Å ± 100Å, respectively. As the stacked magnetic thin films are formed under different conditions in each region, the magnetic thin films constituting the Z-axis thin film fluxgate have different magnetic properties depending on the regions.

Different magnetic history curves can be produced by changing the lamination structure using the same magnetic material. However, the magnetic history curves of the respective regions may be differently formed by forming magnetic thin films using different magnetic materials. By changing the area of the constituent magnetic material, it is possible to cause output peak generation and peak shift generation through the Z-axis fluxgate, but these methods can also be used to generate output peaks through magnetic thin film configurations having different magnetic characteristics. It will be an embodiment in accordance with the principles of the present invention causing the shift.

In the case of the Z-axis thin film fluxgate made of the same magnetic thin film structure as shown in FIG. 12A, the magnetic flux 27 generated by flowing a current through the drive coil 4 in the drive region 24 is selected from the pickup region 23. Magnetic flux flows continuously in the pickup area 23 along the path that is magnetically connected). The direction of generation of magnetic flux is determined by the direction of the current flowing in the drive coil wound around the drive area. When an external magnetic field such as an earth magnetic field is applied from the top in a situation where the magnetic flux in the pickup region is directed upward by the magnetic flux generated in the drive region, the magnetic thin film of the drive region 24 is applied to the magnetic flux 27 caused by the drive coil. In addition, the magnetic flux 30 by the external magnetic field is added, and the added magnetic flux is connected to the pick-up area 23 so that the magnetic flux is added from the downward direction to the upward direction of the pickup area. On the other hand, in the pickup region, a reverse magnetic field due to an external magnetic field is applied to the magnetic flux 28 generated by the drive coil. When the magnetic thin film constituting the Z-axis thin film fluxgate has a configuration having the same magnetic characteristics, the externally applied magnetic field applies the magnetic field 30 to the drive region in the region 23 where pickup is performed, which is below the pickup region. The magnetic flux 30 'coming from the part is made. In addition, the externally applied magnetic field applies a downwardly directed magnetic field 29 that directly affects the pick-up area, so that the magnetic fields of these two components are not perfect but balanced. This results in the pick-up volts of the output signal appearing at the same location regardless of whether an external magnetic field is applied, resulting in little output peak movement regardless of the presence of the external magnetic field. That is, the Z-axis fluxgate made of the same material and configuration cannot detect the direction of the externally applied magnetic field.

FIG. 12 (b) is a view showing a change in magnetic flux inside a magnetic thin film when an external magnetic field is applied when the magnetic thin film constituting the thin film fluxgate for Z-axis is composed of magnetic thin films having different magnetic properties. The magnetic history curve of the magnetic thin film constituting the drive region 24 has a characteristic of laying down more than the magnetic history curve of the magnetic thin film of the pickup region. This means that when the external magnetic field is applied, the amount of change in magnetization occurs relatively small. When the external magnetic field is applied to the magnetic thin film having the structure as shown in FIG. 12 (b), the magnitude 30 of the magnetic flux additionally generated in the drive region 24 is relatively smaller than that in the structure of FIG. 12 (a). The magnitude of the magnetic flux 30 'additionally applied in the downward direction to the upward direction of the pickup area 23 results in the addition of a smaller magnetic flux as compared to the Z-axis fluxgate having the structure of FIG. . On the other hand, the magnitude of the external magnetic field 29 which directly affects the pick-up area according to the externally applied magnetic field has a large influence on the magnetic flux 23 generated by the drive coils directly. As shown in (a) of FIG. 12, the canceled size does not become '0' and the remaining magnetic flux is not canceled. Therefore, there is a magnetic flux having a size that affects the magnetic flux inside the magnetic thin film in the center pickup area. . This difference causes the peak shift of the output volt peak detected by the pickup coil in the pickup region.

The Z-axis thin film fluxgate according to the present invention does not use a method of measuring the distance between output peaks due to a simple longitudinal magnetization change in the form of a rod. By artificially changing the characteristics, each magnetic thin film makes a difference in the degree to which it responds to an externally applied magnetic field, finally generating a peak shift, and measuring the distance between the peaks to detect the direction of the externally applied magnetic field. use.

13 is a view showing the shape of the thin film fluxgate for Z-axis according to the present invention and the resulting electrical characteristics change. 13 (a) and 13 (b) are thin film fluxgates for Z-axis fabricated with the same magnetic thin film structure, and show the magnitude of output volt peaks varying depending on whether grooves 26 formed at the ends of the pickup region are formed. Drawing. The pickup bolt size is formed to be 10 mV or more with or without grooves, but the overall output bolt peak size increases by forming a groove at the end of the pickup area. This result seems to have the same effect as the electrical characteristic change of the thin film fluxgate for X and Y axes shown in FIG. 13 (a) and 13 (b) do not have a large peak shift with respect to the application of an external magnetic field, and thus the configuration shown in FIGS. 13 (c) and 13 (d) is preferable as the electronic compass component.

13 (c) and 13 (d) are views showing the shape of the Z-axis thin film fluxgate composed of the heterogeneous magnetic thin film according to the present invention and changes in electrical characteristics thereof. The Z-axis thin film fluxgate made of two kinds of laminated magnetic thin film structures is composed of two kinds of magnetic thin films, while the Z-axis thin film fluxgate made of the same magnetic thin film structure shows almost no peak shift with respect to an externally applied magnetic field. In the Z-axis flux gate, the peak shift with respect to the external magnetic field is largely generated. In addition, even when the pickup area was divided in the vertical direction as shown in FIG. The characteristic of the shape of (d) of FIG. 13 is characterized in that it is possible to widen the pickup area 23 that can participate in the pickup without increasing the number of pickup coils. As the pickup region widens, the magnitude of the output volt peak increases.

The thin film fluxgate according to the present invention may be manufactured by a manufacturing method as described above with reference to FIGS. 6 to 7. However, the technical core of the three-axis fluxgate according to the present invention is that the fluxgate for detecting the magnetic field component in the vertical direction is composed of a plurality of short thin film sensors to enable a flat shape. Even if the fluxgate is manufactured, it is of course included in the scope of the present invention.

In order to magnetize a plurality of short magnetic thin films arranged in the width direction thereof to the same type of induction magnetic field, a thin film fluxgate for vertical component sensing of a magnetic field is electrically connected to each other by electrically connecting drive coils disposed around each short magnetic thin film. It is preferable to magnetize a plurality of short thin films with one drive coil as shown in FIG.

Although the configuration of the present invention has been described in detail with reference to the preferred embodiments and the accompanying drawings, the protection scope of the present invention is not limited thereto. That is, it will be apparent to those skilled in the art that various modifications and design changes may be made without departing from the technical spirit of the present invention. Therefore, the protection scope of the present invention will be defined by the description of the claims below.

As described above, according to the present invention, three axes capable of three-dimensional azimuth measurement with a size of at least 4 mm (length) x 4 mm (width) x 1.2 mm (height) that can be mounted in a small portable device such as a mobile phone or a PDA. An electronic compass chip employing a thin film fluxgate can be fabricated, and an electronic compass capable of accurately detecting the orientation on the earth's surface even at a power supply of 5V or less, specifically 2V or less can be configured.

Claims (18)

A thin-film three-axis fluxgate that detects magnetic components in the three-axis direction, comprising: a one-bar-shaped thin film fluxgate for detecting two horizontal components arranged on the same plane for sensing horizontal two-axis components of a magnetic field; And a plurality of vertical component sensing thin film fluxgates for sensing vertical components of a magnetic field, wherein the vertical component sensing fluxgates are disposed substantially perpendicular to each of the two horizontal component sensing fluxgates and are horizontal. A thin-film three-axis fluxgate comprising a plurality of magnetic thin films having a shorter length than a component sensing fluxgate. The flux gate of claim 1, wherein the fluxgate for horizontal component detection comprises: A conductive coil for drive and pickup, a magnetic thin film, and an insulating thin film interposed between the coil and the magnetic thin film to prevent a short circuit therebetween, The conductive coil is configured by electrically contacting the upper coil thin film and the lower coil thin film, The insulating thin film includes a lower insulating film interposed between the lower coil thin film and the magnetic thin film, and an upper insulating film interposed between the upper coil thin film and the magnetic thin film. The magnetic thin film is a thin-film triaxial fluxgate formed by stacking two kinds of materials having different magnetic properties. The thin film type triaxial fluxgate of claim 2, wherein the lower coil thin film is formed by forming a groove into which the lower coil thin film is to be inserted from an insulating film on a substrate formed on a silicon wafer, and then deposits a groove depth. The thin film type triaxial fluxgate of claim 2, wherein the lower insulating thin film is composed of SiO ₂ having a thickness of 5,000 μm (0.5 μm) to 20,000 μm (2 μm) or less. The magnetic thin film of claim 2, wherein the magnetic thin film is formed by alternately forming an Al ₂ O ₃ thin film, which is an insulator, after forming NiFe, which is a magnetic material, and has a thickness of the NiFe magnetic thin film and the Al ₂ O ₃ insulator thin film. The thin film type triaxial fluxgate is 600 적어도 ± 300 Å and 150 Å ± 100, respectively, and is formed of at least three pairs of laminated films when the NiFe magnetic thin film and the Al ₂ O ₃ insulator thin film are referred to as a pair. . The thin film three-axis fluxgate of claim 2, wherein the magnetic thin film has a dumbbell shape in which both ends thereof are wider than a central portion thereof. The thin film triaxial fluxgate of claim 6, wherein the magnetic thin film has grooves formed at both ends thereof. The thin film triaxial fluxgate of claim 2, wherein the drive coil and the pickup coil have a line width of 7 ± 2 μm, and the drive coil and the pickup coil are alternately disposed. 3. The thin film triaxial flux of claim 2, wherein the drive coil and the pickup coil are disposed in a predetermined area only with a drive coil and an adjacent predetermined area with only a pickup coil, and the drive coil area and the pickup coil area are alternately disposed. gate. The thin film type triaxial fluxgate of claim 1, wherein the vertical component sensing fluxgate is configured to wind the plurality of magnetic thin films with one connected drive coil and one connected pickup coil. The thin film triaxial fluxgate of claim 10, wherein the magnetic foil has a straight center portion and two semicircular outlines connected to the center portion to have a “∞” shape. The thin film type triaxial fluxgate of claim 11, wherein a pickup coil is disposed at the center portion, and a drive coil is disposed at the outer portion. 12. The thin film triaxial fluxgate of claim 11, wherein the central portion and the outer portion have different magnetic properties. 15. The method of claim 13, wherein the central portion of the NiFe ferromagnetic thin film and the Al ₂ O ₃ insulator thin film thickness of 600Å ± 300Å, 150Å ± 100Å of the laminated thin film form, the outer portion of the NiFe ferromagnetic thin film and Al ₂ O ₃ A thin-film triaxial fluxgate configured in the form of a laminated thin film having an insulator thin film thickness of 1800Å ± 200Å and 150Å ± 100Å, respectively. The thin film triaxial fluxgate according to claim 13, wherein a laminated thin film is formed by using different magnetic bodies in the central portion and the outer portion. The thin film type triaxial fluxgate of claim 13, wherein the width of the center portion and the outer portion is adjusted to adjust the magnitude of the output peak or the magnitude of the peak shift. The thin film triaxial fluxgate according to claim 11, wherein the central portion is divided into two. The thin film triaxial fluxgate of claim 11, wherein a pickup coil is disposed at a central portion of the central portion, and drive coils are disposed at both ends of the central portion and the outer portion of the central portion.

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