JP4291455B2 - Magnetic field sensor - Google Patents

Description

[実験例２]
【００５８】
ガラス基板上にポリイミド樹脂を全面に塗布し３５０℃で熱硬化処理を行った。熱硬化処理後のポリイミドの膜厚は１μｍであった。この上にスパッタ下地膜を用いて、電気めっき法により下部コイル２１を形成した。なお、不要なスパッタ下地膜はアルゴンイオンミリングにて除去した。この際、ポリイミド膜が全面に塗布されているために、ガラス基板がミリングされることはない。次いで、ノボラック系フォトレジストを用いて、パターンニングした後、熱硬化処理を行い、上部絶縁層を形成した。この際に、同一のフォトレジストフレームを用いて、最初にＮｉＦｅを２μｍ、次ぎに銅を１μｍ、さらにＮｉＦｅを２μｍ成膜し、３層構造とした。この際に、永久磁石により磁性体コアの長手方向に磁場を印加しながら成膜を行い、誘導磁気異方性を長手方向に付与した。磁気コア寸法は等は実施例１と同様とした。磁気コアの上に下部絶縁層と同様な手法で上部絶縁層を設け、さらにこの上に下部コイルと同様な手法で上部コイルを設けた。また、本素子は、ウエハーから切断後、励磁電流発生回路、信号処理回路が設けられている半導体基板の所定のパッドとワイヤーボンダーにより、電気的に接続させ、さらにエポキシ樹脂により、半導体基板との一体化モジュールとして評価を進めた。その結果、この磁界センサモジュールにおいては、前記実施例１と同等の出力であったが、ノイズ成分が５０％低減したこと、すなわち、信号／ノイズの比であるＳ／Ｎでは２倍の改善がなされたことが確認できた。
【００５９】
【発明の効果】
上記の結果より本発明の効果は明らかである。すなわち、本発明の磁界センサは、略長方形状の磁性体コアを有し、当該磁性体コアの長手方向と同一方向の外部磁界成分を検出する磁界センサであって、前記磁性体コアの長手方向両端部には高周波電流を通電するための通電部が形成されており、前記磁性体コア周辺近傍には導体コイルが巻かれ、当該導体コイルを用い、前記磁界成分を検出できるようになっており、前記磁性体コアは、その長手方向が磁化容易軸方向である磁気異方性を有してなるように構成されているので、従来のセンサと比べて、極めて高感度となり、しかも小型化が図れるという効果を奏する。
【図面の簡単な説明】
【図１】本発明の磁界センサの好適な一例を概略的に示した斜視図である。
【図２】図１のＡ−Ａ断面矢視図である。
【図３】本発明の磁界センサの好適な一例を概略的に示した斜視図である。
【図４】一軸磁気異方性を示す磁性体コアを用いた素子のインダクタンスの周波数特性を示すグラフである。
【図５】本発明の磁界センサの励磁電流に対するインダクタンス変化を示すグラフである。
【図６】本発明の磁界センサ(ライン（ａ）)と従来の磁界センサ（ライン（ｂ））のインダクタンスの外部磁界依存性を示すグラフである。
【符号の説明】
１…磁界センサ
５…基板
９…高周波電源
１１、１２、１３、１４…磁性体コア
２０…導体コイル
４１，４２…通電部
５１、５２…電極端子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic field sensor that converts an external magnetic field into an electric signal, and more particularly to a small thin-film geomagnetic sensor.
[0002]
[Prior art]
As a method for detecting a minute magnetic field such as geomagnetism, a flux gate magnetic field sensor has been well known. This magnetic field sensor is a traditional high-sensitivity magnetic sensor that was also used for lunar exploration in the Apollo program in the 1960s.
[0003]
The principle of operation of this fluxgate magnetic field sensor is explained by a mechanism in which the external magnetic flux penetrating through the magnetic body is reduced by passing an exciting current through the exciting coil and saturating the magnetic body. In other words, the sensor uses a change in magnetic inductance. Although such a fluxgate magnetic field sensor has high sensitivity and excellent reliability, it is currently used only for special purposes because the magnetic core is large and it is difficult to reduce the size and price. .
[0004]
In recent years, as the application of large CRTs of 20 inches or more to geomagnetic correction and car navigation systems has started, small magnetic sensors using ferromagnetic ribbons or thin films have been reported. In particular, sensor elements that apply a high-frequency current directly to a ferromagnetic ribbon or thin film and use a magnetic field generated thereby have been attracting attention. Such so-called direct energization has the advantage of realizing high-efficiency magnetization without the influence of a demagnetizing field.
[0005]
For example, Japanese Patent No. 2617498 discloses a magnetic field sensor that applies a pulse current to a conductive band-shaped ferromagnetic magnetic core and detects an external magnetic field by an electric signal from a conductor winding wound around the magnetic core. ing. The magnetic material used here is an amorphous wire having no magnetostriction or a strip-shaped amorphous ribbon.
[0006]
Japanese Patent Application Laid-Open No. 8-75835 discloses a magnetic impedance effect element in which a magnetic thin film is formed on a substrate and electrodes are provided at both ends in the longitudinal direction. This magneto-impedance effect was proposed by Dr. Toshio Mori, one of the inventors in the publication, but in the short side (width) direction and circumferential direction of a rectangular or linear ferromagnetic material. It is characterized by providing magnetic anisotropy in advance. The magnetic field from the longitudinal direction rotates the magnetization vector of the magnetic material, increasing the permeability in the width direction, thereby increasing the skin effect, thereby increasing the impedance of the ferromagnetic material. That is, it uses a completely different principle from the fluxgate magnetic field sensor.
[0007]
Further, Japanese Patent Application Laid-Open No. 8-330745 discloses a magnetic detection element based on the magnetic impedance effect in which a magnetic thin film is formed on the entire upper surface of a rectangular substrate. In this case as well, similarly to the above publication, since the magneto-impedance effect is used, the magnetization easy axis direction, that is, the magnetic anisotropy is the width direction, and the magnetic field detection direction which is the longitudinal direction of the element is the magnetization difficult axis direction. It is an important point.
[0008]
[Problems to be solved by the invention]
As described above, in the conventionally known flux gate type magnetic field sensor using the magnetic inductance effect, a large amount of external magnetic flux must be introduced into the magnetic body when no exciting current is applied. Therefore, in a magnetic material having magnetic anisotropy, it is necessary to make the magnetization detection direction, which is the longitudinal direction of the element, coincide with the hard magnetization axis direction. In other words, it is necessary to make the easy axis direction, which is the magnetic anisotropy direction, orthogonal to the magnetization detection direction. In such a sensor mechanism, for example, if the magnetic field intensity at which the hard axis direction is saturated is Hkh, and the magnetic field intensity at which the easy axis direction is saturated is Hke, then Hkh >> Hke. For this reason, when the magnetic anisotropy direction is orthogonal to the magnetization detection direction, it is advantageous to detect a magnetic field corresponding to a large Hkh, but a small Hkh is required to detect a minute magnetic field.
[0009]
Also, the magneto-impedance effect elements proposed in the above two publications are structurally similar to conventionally known magnetic inductance elements, and the magnetization detection direction needs to be the hard magnetization axis.
[0010]
In particular, when a magnetic thin film is used as a magnetic core, if an attempt is made to reduce Hkh, the magnetic anisotropy is disturbed, resulting in a characteristic close to an isotropic film, the permeability of the hard axis is lowered, and the magnetization is reduced. There has been a problem that the coercive force of the easy shaft increases.
[0011]
The present invention has been devised under such circumstances, and an object of the present invention is to solve the above-described conventional problems and to provide a highly sensitive and compact magnetic field sensor.
[0012]
[Means for Solving the Problems]
In order to solve such a problem, the magnetic field sensor of the present invention is a magnetic field sensor that has a substantially rectangular magnetic core and detects an external magnetic field component in the same direction as the longitudinal direction of the magnetic core. In addition, energization portions for energizing a high frequency current are formed at both longitudinal ends of the magnetic core, a conductor coil is wound around the periphery of the magnetic core, and the magnetic field component is used by using the conductor coil. The magnetic core is configured to have magnetic anisotropy whose longitudinal direction is the easy magnetization axis direction.
[0013]
In a preferred embodiment of the present invention, the main factor for forming the magnetic anisotropy is induced magnetic anisotropy.
[0014]
As a preferred embodiment of the present invention, when the length of the magnetic core is L and the width is W, the ratio L / W, which is the ratio of these, is 10 or more and 1000 or less.
[0015]
Further, as a preferred aspect of the present invention, a plurality of the magnetic cores are combined and arranged in parallel with a predetermined gap therebetween, and a high-frequency current is passed through substantially both ends in the longitudinal direction of the magnetic cores. And a plurality of magnetic cores are configured to be connected substantially in parallel or in series.
[0016]
As a preferred embodiment of the present invention, the magnetic core has a thickness of 1 to 30 μm.
[0017]
As a preferred embodiment of the present invention, the magnetic core is configured such that the coercive force Hce measured in the direction of the easy axis of the magnetic core is 0.1 Oe or more and 3 Oe or less.
[0018]
Moreover, as a preferable aspect of the present invention, the frequency of the high-frequency current supplied to the energization unit is configured to be 0.1 MHz or more and 1000 MHz or less.
[0019]
As a preferred embodiment of the present invention, the magnetic core is configured to be a multilayer film having a nonmagnetic layer as an intermediate layer and divided into at least two upper and lower magnetic layers.
[0020]
The magnetic field sensor using the magnetic inductance effect of the present invention is a magnetic field sensor that has a substantially rectangular magnetic core and detects an external magnetic field component in the same direction as the longitudinal direction of the magnetic core. The core has a mechanism in which the longitudinal direction is the easy magnetization axis direction and high-frequency excitation is performed in the hard magnetization axis direction by passing a high-frequency current of 0.1 MHz to 1000 MHz in the longitudinal direction of the magnetic core, Compared to the state where no current is applied, more external magnetic flux in the longitudinal direction can be introduced into the magnetic core in the state where the current is applied. It is comprised so that it may detect as an inductance change of the conductor coil wound by the body.
[0021]
According to the present invention, in particular, since the longitudinal direction of the magnetic core is the easy axis direction and the magnetization detection direction, a large output can be obtained with a small magnetic field about the coercivity of the easy axis direction of the magnetic body. . Furthermore, high-frequency driving is possible for excitation in the hard axis direction, and high output can be realized at the same time.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments of the present invention will be described in detail.
[0023]
FIG. 1 is a perspective view schematically showing a preferred embodiment of a magnetic field sensor 1 of the present invention, and FIG. 2 is a cross-sectional view taken along the line AA in FIG.
[0024]
As shown in these drawings, the magnetic field sensor of the present invention has magnetic cores 11, 12, 13, and 14 made of a substantially rectangular ferromagnetic material on a substrate 5. The conductor coil 20 is wound in a state where these magnetic cores 11, 12, 13, 14 are collectively shown in the figure. In the case of the present embodiment, the four magnetic cores are connected in parallel and in series, each having two substantially rectangular magnetic cores (11 and 12, 13 and 14). That is, a current-carrying part 41 and a current-carrying part 42 that are integrally connected are formed at one end of each of the magnetic cores 11 and 12 and the magnetic cores 13 and 14, respectively. At the other end, there is provided a conductive film 60 for folding which integrally connects the four core end portions. The energization portions 41 and 42 are formed to energize a high-frequency current, and are connected to a high-frequency power source 9 as illustrated.
[0025]
A magnetic coil 20 for detecting a magnetic field is wound around these magnetic cores 11, 12, 13, and 14. The conductor coil 20 is usually formed as a thin film coil 20, and electrode terminals 51 and 52 are provided on the lead portion of the coil. In general, the electrode terminals 51 and 52 are connected to a power source and a signal processing unit provided outside by a wire bonder. Of course, it is also possible to provide solder bumps on the electrode terminals 51 and 52 and mount them on a printed circuit board or the like with the board surface facing up. Alternatively, it is possible to form a sensor on a substrate having a through hole and mount the sensor surface on a printed circuit board or the like.
[0026]
In the present invention, the easy magnetization axis direction (α) of the magnetic cores 11, 12, 13, and 14 is set in the same direction as the longitudinal direction of the magnetic core, and the external magnetic field detection direction (Hex) is also set. Moreover, it is the same direction as the longitudinal direction of a magnetic body core. Even if the direction of the external magnetic field deviates from the longitudinal direction of the magnetic core, an external magnetic field component in the same direction as the core longitudinal direction can be detected.
[0027]
In the present invention, a signal generated in the conductor coil 20 wound around the ferromagnetic cores 11, 12, 13, 14 by applying a high-frequency current from the current-carrying portions 41, 42 of the magnetic core, 52 as an output.
[0028]
As shown in FIG. 1, a plurality of ferromagnetic cores are combined, arranged in parallel with a predetermined gap therebetween, and a high frequency current is passed through substantially both ends in the longitudinal direction of these magnetic cores. Compared with the case where a single wide core is used, the current-carrying part is formed integrally, and the plurality of magnetic cores are configured to be connected substantially in parallel or in series. The effect of the above is reduced and the effective permeability of the magnetic core is increased, so that a high output can be obtained. In addition, since the magnetic domain structure of the magnetic core is improved, the effect of reducing the noise component is exhibited.
[0029]
As shown in FIG. 1, the short sides at both ends of the magnetic cores 11, 12, 13, and 14 each form an acute angle (a shape with a sharp tip). The form is also regarded as one of a substantially rectangular shape. By forming an acute angle, the magnetic domain structure can be stabilized and noise can be reduced as compared with a so-called simple rectangular magnetic material. That is, the “substantially rectangular shape” referred to in the present invention indicates a state in which the length L (FIG. 1) is longer than the width W (FIG. 2). The length L in the case where an acute angle is formed at the short side portion of the end portion of the magnetic core refers to the entire length. In one magnetic core, the value of L / W, which is the ratio of the length (L) to the width (W), is preferably 10 or more and 1000 or less, particularly preferably 10 or more and 300 or less. When the value of L / W is less than 10, the magnetic field sensitivity decreases due to the demagnetizing field effect. On the other hand, when the value of L / W exceeds 1000, patterning of the magnetic core element becomes difficult, or the element becomes long and large. The number of magnetic cores wound around one conductor coil 20 is not necessarily one, and several narrow magnetic cores can be used (embodiment of the present invention).
[0030]
The conductor coil 20 in FIG. 1 has a simple winding coil shape as a detection coil, but this may be a thin film coil 20 formed based on a so-called thin film process as described above. preferable. FIG. 2 partially shows a cross section of the thin film coil 20, and the thin film coil (detection coil) is usually formed by coupling the lower coil portion 21 and the upper coil portion 25. In this case, in order to insulate from the magnetic cores 11, 12, 13, and 14, the insulating layers 71 and 72 are formed so as to surround the magnetic core.
[0031]
If the current-carrying portions 41 and 42 made of copper and the conductive film 60 for folding are formed at the same time as the thin-film coil is formed, the manufacturing process can be rationalized.
[0032]
The gap between the adjacent magnetic cores is about 0.1 to 50 μm.
[0033]
The material of the magnetic cores 11, 12, 13, and 14 used in the present invention can be selected from known soft magnetic materials having various uniaxial magnetic anisotropies such as NiFe, NiFeMo, CoFe, and CoNiFe. A high-speed quenching ribbon or a bulk plate can be used for the production method, but a magnetic thin film having a thickness of 1 μm or more and 30 μm or less obtained by patterning a thin film formed by a vacuum film forming method or a plating method is particularly preferable. When the film thickness is less than 1 μm, the output decreases, and when the film thickness exceeds 30 μm, it becomes difficult to impart good uniaxial magnetic anisotropy.
[0034]
As a method for imparting uniaxial magnetic anisotropy in the longitudinal direction of each of the magnetic cores 11, 12, 13, and 14, there is induced magnetic anisotropy or strained magnetic anisotropy, or a method in which both are combined. preferable. Particularly preferred is induced magnetic anisotropy. This is because it is easy to manage anisotropy directionality and anisotropy value (size).
[0035]
The coercive force Hce in the easy axis direction of the magnetic cores 11, 12, 13, and 14 is preferably 0.1 Oe or more and 3 Oe or less. When the coercive force Hce is less than 0.1 Oe, the detectable magnetic field range becomes extremely small, and when the coercive force Hce exceeds 3 Oe, the magnetic field sensitivity is lowered.
[0036]
In the magnetic field sensor of the present invention, a high-frequency current flows in the longitudinal direction of the magnetic cores 11, 12, 13, and 14. The high-frequency current in the present invention is a general term for currents whose current values change with time, and can be used in any waveform such as a sine wave, a rectangular wave, a sawtooth wave, and a pulse wave. In the case of a sine wave, the frequency is preferably from 0.1 MHz to 1000 MHz. If the frequency is out of the range, the output is reduced in any case.
[0037]
The operating principle of the present invention is completely different from various known magnetic field sensors. That is, the conventional magnetic field sensor using the magnetic inductance effect has a mechanism in which the external magnetic flux penetrating through the magnetic core is reduced by passing an exciting current through the exciting coil and saturating the magnetic core. On the other hand, the action of the magnetic field sensor of the present invention is completely opposite. In other words, the present invention has a mechanism in which the longitudinal direction of the substantially rectangular magnetic core is the axis of easy magnetization (direction (α) in FIG. 1), and a high-frequency current is passed in the longitudinal direction of the magnetic core. Compared with the case where no current is applied (state where current value = 0), more external magnetic flux in the longitudinal direction is introduced into the magnetic body when the current is supplied, and this magnetic flux causes the external magnetic field Hex to be introduced into the magnetic body. A magnetic inductance effect is used, which is detected as an inductance change of a coil wound around.
[0038]
FIG. 3 shows a different embodiment of the magnetic field sensor of the present invention. In FIG. 3, current-carrying portions 41 and 42 that are integrally joined are formed at both ends of four magnetic cores 11, 12, 13, and 14. The magnetic cores are simply connected in parallel. The conductive film 60 for folding as shown in FIG. 1 does not exist. In this case (FIG. 3), there is an advantage that the structure is simple and the production yield is high, and in the form of FIG. 1, a signal due to the excitation current is added to the detection coil in order to cancel the magnetic flux change due to the excitation current. There is a merit that it is not.
[0039]
Hereinafter, the configuration and operation principle of the present invention will be described in detail, including comparison with the prior art.
[0040]
FIG. 4 shows an example of a graph showing how the inductance of a magnetic element having a substantially rectangular magnetic body having a coil wound around the magnetic body core depends on the frequency. Has been. In the case where the longitudinal direction of the magnetic core is the easy axis (line (a) in the figure), the inductance decreases at a frequency of 1 MHz or more, and at 10 MHz, the inductance is 1 μH or less. On the other hand, when the longitudinal direction of the magnetic core is the hard axis (line (b) in the figure), the inductance is maintained at 20 μH even at a high frequency of 10 MHz or higher. In the magnetic field sensor using the magnetic inductance effect, an output is obtained in proportion to the drive frequency. That is, in order to obtain a high output, it is preferable to drive at a high frequency. For this purpose, in a conventionally known magnetic field sensor, the longitudinal direction of the magnetic material is the hard axis (or conversely, the direction perpendicular to the longitudinal direction is the easy axis). )
[0041]
In contrast, the magnetic field sensor of the present invention uses the longitudinal direction of the magnetic core as the easy axis of magnetization, but the present invention further includes a mechanism for passing a high-frequency excitation current in the longitudinal direction of the magnetic core. That is, as shown in FIG. 5, a phenomenon is used in which a high-frequency excitation current is passed through the magnetic core and the magnetization direction is rotated by 90 degrees to increase the inductance. As shown by the line (a) in FIG. 4, the inductance of 10 MHz in the state where no exciting current is applied is 1 μH or less, but the inductance is reduced to 20 μH by supplying 100 mA as shown in FIG. Was rising. Further, it has been confirmed by the present inventors that the frequency dependency of the inductance in the energized state is exactly the same as the line in FIG. 4B and shows a high value up to 100 MHz. That is, the magnetic field sensor of the present invention uses the longitudinal direction of the magnetic core as the easy axis of magnetization, but it can be seen that high frequency driving is possible. The exciting current is preferably 10 to 1000 mA, particularly preferably 100 to 300 mA. When the excitation current is less than 10 mA, the magnetization direction is not sufficiently moved. When the excitation current exceeds 1000 mA, the magnetization is too strong and the change due to the external magnetic field becomes small.
[0042]
Further, FIG. 5 shows the external magnetic field dependency of the inductance in a state where an excitation current of 100 mA is applied to the element ((a) in the figure) whose longitudinal axis is the easy axis of magnetization, and the magnetic core. 2 shows the external magnetic field dependence of the inductance of the element ((b) in the figure) whose longitudinal direction is the hard axis of magnetization. In both cases, the inductance when no external magnetic field is applied (Hex = 0) is 20 μH, but (a) the element decreases abruptly with a small external magnetic field, whereas (b) the element decreases gently. To do. A point A shown in FIG. 5 corresponds to (a) the saturation magnetic field Hke in the direction of the easy axis of the element, and B point corresponds to the saturation magnetic field Hkh in the direction of the hard axis of the element (b). Note that Hke ideally coincides with the coercive force Hce ideally in the easy axis direction, but in an actual element, Hke ≧ Hce due to various effects.
[0043]
In a magnetic body having uniaxial magnetic anisotropy, since Hce << Hkh, the magnetic field sensor of the present invention has extremely high magnetic field sensitivity.
[0044]
In addition, the magnetic field sensor of this invention can comprise not only a simple output signal from a coil but also various detection circuits used in conventionally known magnetic field sensors. For example, (1) using an appropriate bias magnetic field, (2) processing a difference signal between signals obtained for positive and negative excitation currents, and (3) current in the coil so that the output signal is constant. Is applied to process the current value.
[0045]
Further, in order to stabilize the magnetic domain structure of the substantially rectangular ferromagnetic thin film (magnetic core) used in the magnetic field sensor of the present invention, a nonmagnetic layer is provided as an intermediate layer, and the upper and lower magnetic layers are magnetically separated. It is also preferable to configure it to be coupled. In that case, it is also possible to use a conductive layer as an intermediate layer. In this case, the excitation current flows mainly through the conductive layer located in the middle. Further, in order to stabilize the magnetic domain, a high coercive force thin film can be formed in the vicinity of both ends in the longitudinal direction.
[0046]
In the magnetic field sensor of the present invention, it is preferable to provide a known organic and / or inorganic protective film 75 on the uppermost surface as shown in FIG. Furthermore, it is also possible to perform the resin sealing process similar to other electronic components. In this case, it is desirable to previously form a protective layer with a resin different from the sealing resin as the stress relaxation layer before sealing the resin so that a large stress is not applied to the magnetic core.
[0047]
Further, by combining two magnetic field sensors of the present invention, a three-axis magnetic field sensor can be formed by combining three two-axis magnetic field sensors. At this time, the directions in which the currents of the magnetic cores constituting each sensor flow are arranged orthogonal to each other. In the case of two axes, it is possible to form element portions on the front and back of a single substrate, or to stack two sensors on a single substrate.
[0048]
The magnetic field sensor of the present invention described above is particularly preferably formed by a thin film process similar to that of a thin film magnetic head.
[0049]
【Example】
The present invention will be described in further detail with reference to specific examples.
[Experiment 1]
(Examples 1-4, Comparative Examples 1-2)
[0050]
A magnetic field sample as shown in FIG. 3 was prepared as follows.
[0051]
Preparation of concrete samples
[0052]
A lower coil 21 was formed on the silicon wafer substrate 5 having an oxide film on the surface by electroplating. Note that both ends of the coil lead wire are produced when the lower coil 21 is produced in order to improve the yield. Next, a magnetic core made of a NiFeMo plating film (magnetostriction almost zero composition) was formed on the lower insulating layer 71 made of a thermosetting novolac resin. The length L of the magnetic core was fixed to 2 mm, and the width W and the film thickness d were various shapes shown in Table 1 below. In Table 1, “100 × 3” indicates a state in which three magnetic cores having a width of 100 μm are formed and connected in parallel.
[0053]
After forming the magnetic film, the upper coil 25 was formed through the upper insulating layer 72. When the upper coil 25 is exposed to the photoresist, an auxiliary exposure mask is used because the resist film thickness is distributed. Finally, an insulating layer was formed as the protective layer 75 to obtain a magnetic field sensor.
[0054]
The patterning of the magnetic core was performed by frame plating or etching using a resist pattern exposed and developed using a mask by a photoresist method.
[0055]
In Examples 1 to 4, the NiFeMo plating film was formed while applying a 600 G DC magnetic field in the longitudinal direction of the magnetic material, and induced magnetic anisotropy was imparted in the longitudinal direction. In contrast, in the first comparative example, inductive magnetic anisotropy was imparted in the same manner in the element width direction, and in the second comparative example, the film was formed in a rotating magnetic field to make an isotropic film. The magnetic properties (Hce, Hkh) of a 1 cmφ plated film subjected to the same film formation method were evaluated with a vibrating sample magnetometer.
[0056]
Furthermore, a high frequency current of 5 MHz sine waveform is applied to the magnetic core of the completed magnetic field sensor, the output value by geomagnetism (0.3 Oe) is obtained, converted to output per 1T (Tesla), and each sample element is compared. did. The results are shown in Table 1.
[0057]
[Table 1]

[Experiment 2]
[0058]
A polyimide resin was applied on the entire surface of a glass substrate and heat-cured at 350 ° C. The film thickness of the polyimide after the thermosetting treatment was 1 μm. A lower coil 21 was formed thereon by electroplating using a sputter base film. Unnecessary sputter base film was removed by argon ion milling. At this time, since the polyimide film is applied to the entire surface, the glass substrate is not milled. Next, after patterning using a novolac photoresist, a thermosetting process was performed to form an upper insulating layer. At this time, using the same photoresist frame, a NiFe film having a thickness of 2 μm, a copper film having a thickness of 1 μm, and a NiFe film having a thickness of 2 μm were formed to form a three-layer structure. At this time, film formation was performed while applying a magnetic field in the longitudinal direction of the magnetic core with a permanent magnet to impart induced magnetic anisotropy in the longitudinal direction. The magnetic core dimensions were the same as in Example 1. An upper insulating layer was provided on the magnetic core in the same manner as the lower insulating layer, and an upper coil was further provided thereon in the same manner as the lower coil. In addition, this element is electrically connected by a wire bonder to a predetermined pad of a semiconductor substrate provided with an exciting current generation circuit and a signal processing circuit after being cut from the wafer, and is further connected to the semiconductor substrate by an epoxy resin. Evaluation progressed as an integrated module. As a result, in this magnetic field sensor module, the output was the same as in the first embodiment, but the noise component was reduced by 50%, that is, the signal / noise ratio S / N was doubled. It was confirmed that it was done.
[0059]
【The invention's effect】
The effects of the present invention are clear from the above results. That is, the magnetic field sensor of the present invention is a magnetic field sensor that has a substantially rectangular magnetic core and detects an external magnetic field component in the same direction as the longitudinal direction of the magnetic core, the longitudinal direction of the magnetic core. Current-carrying parts for conducting high-frequency currents are formed at both ends, and a conductor coil is wound around the magnetic core, so that the magnetic field component can be detected using the conductor coil. The magnetic core has a magnetic anisotropy whose longitudinal direction is the direction of the easy axis of magnetization. Therefore, the magnetic core has extremely high sensitivity and can be downsized. There is an effect that can be achieved.
[Brief description of the drawings]
FIG. 1 is a perspective view schematically showing a preferred example of a magnetic field sensor of the present invention.
FIG. 2 is a cross-sectional view taken along the line AA in FIG.
FIG. 3 is a perspective view schematically showing a preferred example of the magnetic field sensor of the present invention.
FIG. 4 is a graph showing frequency characteristics of inductance of an element using a magnetic core exhibiting uniaxial magnetic anisotropy.
FIG. 5 is a graph showing an inductance change with respect to an exciting current of the magnetic field sensor of the present invention.
FIG. 6 is a graph showing the external magnetic field dependence of the inductance of the magnetic field sensor of the present invention (line (a)) and the conventional magnetic field sensor (line (b)).
[Explanation of symbols]
1 ... Magnetic field sensor
5 ... Board
9 ... High frequency power supply
11, 12, 13, 14 ... magnetic core
20: Conductor coil
41, 42 ... energization part
51, 52 ... Electrode terminals

Claims (9)

In a magnetic field sensor having a substantially rectangular magnetic core and detecting an external magnetic field component in the same direction as the longitudinal direction of the magnetic core,
Current-carrying portions for passing a high-frequency current are formed at both ends in the longitudinal direction of the magnetic core, a conductor coil is wound around the periphery of the magnetic core, and the magnetic field component is It can be detected,
The magnetic core has a magnetic anisotropy whose longitudinal direction is an easy magnetization axis direction. The magnetic field sensor according to claim 1, wherein a main factor of formation of the magnetic anisotropy is induced magnetic anisotropy. 3. The magnetic field sensor according to claim 1, wherein when the length of the magnetic core is L and the width is W, a value of L / W that is a ratio thereof is 10 or more and 1000 or less. A plurality of the magnetic cores are combined and arranged in parallel with a predetermined gap therebetween, and energizing portions for energizing a high frequency current are integrally formed at both ends in the longitudinal direction of the magnetic cores. 4. The magnetic field sensor according to claim 1, further comprising: a formed portion, wherein the plurality of magnetic cores are connected substantially in parallel or in series. The magnetic field sensor according to claim 1, wherein the magnetic core has a thickness of 1 to 30 μm. 6. The magnetic field sensor according to claim 1, wherein the magnetic core has a coercive force Hce measured in the direction of the easy axis of the magnetic core of 0.1 Oe or more and 3 Oe or less. . The magnetic field sensor according to any one of claims 1 to 6, wherein a frequency of a high-frequency current to be supplied to the energization unit is 0.1 MHz to 1000 MHz. 8. The magnetic field sensor according to claim 1, wherein the magnetic core is a multilayer film having a nonmagnetic layer as an intermediate layer and divided into at least two upper and lower magnetic layers. In a magnetic field sensor having a substantially rectangular magnetic core and detecting an external magnetic field component in the same direction as the longitudinal direction of the magnetic core,
The magnetic core has a mechanism in which the longitudinal direction is an easy magnetization axis direction and a high-frequency excitation is performed in the hard magnetization axis direction by passing a high frequency current of 0.1 MHz to 1000 MHz in the longitudinal direction of the magnetic core. Compared with the state where the current is not supplied, more external magnetic flux in the longitudinal direction can be introduced into the magnetic core in the state where the current is supplied. Is detected as a change in inductance of a conductor coil wound around the magnetic material. A magnetic field sensor using a magnetic inductance effect.

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