JP2010056260A - Magnetic switch and magnetic field detection method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic switch that can distinguish a positive magnetic field from a negative magnetic field to detect them and can be manufactured by simple structure at low cost. <P>SOLUTION: A magnetic switch 10 is at least provided with: a semiconductor substrate 11 equipped with an integrated circuit (illustration is elminated) for performing, e.g, switching operation; a magnetoresistance element 13 provided at one surface 11a side of the semiconductor substrate 11 and having a magnetic sensing direction in the in-plane direction; and a bias magnet provided at the other surface 11b side of the semiconductor substrate 11 and applying a bias magnetic field to the magnetoresistance element 13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic switch, and more particularly to a magnetic switch and a magnetic field detection method for performing a switching operation by discriminating between a positive magnetic field and a negative magnetic field using a magnetoresistive effect.

  Magnetic switches are used as sensors that detect the strength of magnetic flux density and the direction of a magnetic field. For example, in the conventional magnetic switch 100 shown in the upper part of FIG. 9, four MR (magnetoresistive) films 101 to 104 are connected to form a Wheatstone bridge circuit.

  Then, changes in OUT1 and OUT2, which are two output signals output from the magnetic switch 100 according to the strength of the magnetic field, are, for example, as shown in the waveform diagram at the bottom of FIG. In this waveform diagram, the positive and negative magnetic fields are shown in the X-axis direction, and the magnetic field strength is shown in the Y-axis direction. According to this waveform diagram, the conventional magnetic sensor 100 outputs the output voltage value so as to be symmetric with respect to the Y-axis, and therefore cannot determine whether the magnetic field is positive or negative, and simply determines the absolute value of the magnetic field strength. It only stays detectable.

For this reason, as a magnetic sensor capable of detecting positive and negative magnetic fields separately, for example, a magnetic switch using two Hall ICs respectively corresponding to the positive magnetic field and the negative magnetic field, or using an exchange bias by a GMR sensor, Known are magnetic switches that can discriminate between positive and negative, or magnetic switches that include a coil that applies a bias magnetic field (see, for example, Patent Document 1).
JP 2000-35470 A

  However, the conventional magnetic switch capable of discriminating between the positive and negative magnetic fields as described above has the following problems. That is, in a magnetic switch using two Hall ICs, the manufacturing cost is increased by using two Hall ICs. In addition, the magnetic switch using the exchange bias by the GMR sensor has a complicated structure and requires many steps for its manufacture, which also increases the manufacturing cost. Furthermore, in a magnetic switch provided with a coil for applying a bias magnetic field, it is necessary to keep a current flowing through the coil during operation, resulting in an increase in power consumption.

  The present invention has been made in view of the above circumstances, and provides a magnetic switch that can be detected by distinguishing between a positive magnetic field and a negative magnetic field and that can be manufactured at a low cost with a simple configuration. Objective.

  It is another object of the present invention to provide a magnetic field detection method capable of reliably distinguishing whether an external magnetic field is a positive magnetic field or a negative magnetic field.

The magnetic switch according to claim 1 of the present invention includes a semiconductor substrate, a magnetoresistive element formed on the semiconductor substrate, a bias magnet that applies a bias magnetic field to the magnetoresistive element, and an external that is applied to the magnetoresistive element. It has at least a first output unit and a second output unit that output a voltage corresponding to the strength of the magnetic field.
The magnetic switch according to a second aspect of the present invention is the magnetic switch according to the first aspect, wherein the first output unit outputs a voltage corresponding to the magnetic field strength of the positive magnetic field among the external magnetic fields applied to the magnetoresistive element. The second output unit outputs a voltage corresponding to the magnetic field strength of a negative magnetic field among the external magnetic fields applied to the magnetoresistive element.
According to a third aspect of the present invention, in the magnetic switch according to the first or second aspect, the bias magnet is formed by applying a paste-like magnetic material.
A magnetic switch according to a fourth aspect of the present invention is the magnetic switch according to the first or second aspect, wherein the bias magnet is a sintered magnetic thin film.
According to a fifth aspect of the present invention, there is provided a magnetic field detection method comprising: a semiconductor substrate; a magnetoresistive element formed on the semiconductor substrate; a bias magnet that applies a bias magnetic field to the magnetoresistive element; and the magnetoresistive element. Using a magnetic switch having at least a first output unit and a second output unit that outputs a voltage corresponding to the strength of an external magnetic field, the first output signal output from the first output unit, and the second output unit The bias magnetic field is applied to the magnetoresistive element so that either one of the second output signals output from is output as a positive magnetic field and the other as a negative magnetic field, and the external magnetic field is a positive magnetic field or a negative magnetic field. It distinguishes and detects.

  According to the present invention, a bias is applied to a semiconductor substrate as a means for applying a bias magnetic field to a magnetoresistive element as compared with a magnetic switch using a conventional Hall IC or a magnetic switch using an exchange bias by a GMR sensor. Since it is only necessary to provide a magnet, it is possible to manufacture a magnetic switch that can output by distinguishing between a positive magnetic field and a negative magnetic field at a low cost with a simple manufacturing process.

  In addition, by using a paste magnet or a sintered thin film magnet as a means for applying such a bias magnetic field, a current is supplied to the coil during operation as compared with a magnetic switch having a coil for applying a bias magnetic field. A magnetic switch with low power consumption can be realized without having to keep flowing.

  In the magnetic switch of the present invention, a bias magnetic field is applied to the magnetoresistive element by a bias magnet, so that a positive magnetic field and a negative magnetic field can be separately output from the first output unit and the second output unit. As a result, the switching operation can be performed by distinguishing between the positive magnetic field and the negative magnetic field.

  Hereinafter, an embodiment of a magnetic switch according to the present invention will be described with reference to the drawings. Note that the present invention is not limited to such an embodiment. In addition, in the drawings used in the following description, in order to make the features of the present invention easier to understand, there is a case where a main part is shown in an enlarged manner for convenience, and the dimensional ratio of each component is the same as the actual one. Not necessarily.

FIG. 1 is a plan view showing an example of the magnetic switch of the present invention. 2 is a cross-sectional view taken along the line AA of the magnetic switch of FIG.
The magnetic switch 10 includes, for example, a semiconductor substrate 11 provided with an integrated circuit (not shown) that performs a switching operation, and a magnetoresistive element 13 that is provided on one surface 11a side of the semiconductor substrate 11 and has a magnetosensitive direction in the in-plane direction. The bias magnet 12 is provided on the other surface 11b side of the semiconductor substrate 11 and applies a bias magnetic field to the magnetoresistive element 13 at least.

  In addition, on the one surface 11a side of the semiconductor substrate 11, for example, a first output unit 21 and a second output unit 22 that respectively output output voltages of two potentials described later are formed. Further, a current supply unit 23 and a ground unit 24 for supplying a sense current to each unit such as the magnetoresistive element 13 and an IC (not shown) connected to the magnetic switch 10 are formed. The first output unit 21, the second output unit 22, the current supply unit 23, and the ground unit 24 may be bumps made of, for example, solder balls.

  The magnetoresistive element 13 is made of, for example, an anisotropic magnetoresistive material (MR) formed along the one surface 11a of the semiconductor substrate 11 and having a magnetosensitive direction in the in-plane direction. Such an anisotropic magnetoresistive material can be composed of a magnetic film made of a ferromagnetic material such as iron-nickel (FeNi), iron-nickel-cobalt (NiFeCo), and preferably includes permalloy.

  FIG. 3 is a plan view showing the outer shape of the magnetoresistive element. The magnetoresistive element 13 includes, for example, four sets of MR thin film resistors 13a, 13b, 13c, 13d each having a meander shape, and terminals a, b, c, d is provided to form a Wheatstone bridge circuit.

  As a method for forming each of the MR thin film resistors 13a, 13b, 13c, and 13d, for example, there is a method in which a pattern forming step by a photolithography method and a film forming step by a plating method or a sputtering method are combined.

  The formation patterns of the MR thin film resistors 13a, 13b, 13c, and 13d are arranged in predetermined directions. In the case of the magnetoresistive element 13 shown in FIG. 3, the two MR thin film resistors 13a and 13d are arranged so as to extend along the X direction on the one surface 11a of the semiconductor substrate 11, and the other two MR thin film resistors 13b. , 13c are arranged so as to extend along the Y direction orthogonal to the X direction on the one surface 11a of the semiconductor substrate 11.

The two MR thin film resistors 13a and 13d arranged facing the X direction are provided with a plurality of MR films arranged parallel to each other with the X direction as the longitudinal direction, and adjacent MR films are in a meander shape (zigzag folding). Shape) and electrically connected in the Y direction through an MR film or a conductive film.
Further, the two MR thin film resistors 13b and 13c arranged in the Y direction are provided with a plurality of MR films arranged in parallel with the Y direction as the longitudinal direction, and adjacent MR films have meander shapes at the ends. It is electrically connected in the X direction via an MR film or a conductive film so as to have a (zigzag folded shape).

  The four MR thin film resistors 13a to 13d are preferably formed from MR films of the same material. As a result, the four elements have the same characteristic variation with respect to temperature, so that the temperature characteristics of the magnetic device are improved. When the folded portion is formed of a conductive film, a conductor film such as gold (Au), copper (Cu), or aluminum (Al) can be used.

  The magnetoresistive element 13 constitutes a Wheatstone bridge circuit. For this reason, in the four MR thin film resistors 13a to 13d, elements arranged in different directions (X direction or Y direction) are arranged adjacent to each other and connected via wiring. These wirings can be composed of a conductor film such as gold (Au), copper (Cu), aluminum (Al), or the like. The four MR thin film resistors are preferably the same in material, pattern shape and resistance value except that they are arranged by changing the direction by 90 °. As an aspect of arranging the four MR thin film resistors, for example, an arrangement of 2 × 2 in length and width as shown in FIG. 3 can be cited, but other arrangements are adopted by connecting the MR thin film resistors with appropriate wiring. It is also possible.

  In such a Wheatstone bridge circuit, when the power supply voltage (sense current) is connected to the terminal a and the ground level is connected to the terminal b, the output of the magnetoresistive element 13 is between the other two terminals c and d. It can be obtained as a potential difference (bridge output). Since the bridge output increases or decreases to reflect the magnitude of the applied magnetic field, the magnitude of the bridge output (voltage) is compared with a predetermined threshold, and the output voltage is greater than the predetermined threshold (high level state), Switching operation can be performed by determining whether the output voltage is smaller than a predetermined threshold value (low level state). The switching operation is performed by, for example, an integrated circuit (not shown) formed on the semiconductor substrate 11.

  As shown in FIG. 2, the bias magnet 12 applies a bias magnetic field B along the in-plane direction M where the magnetoresistive element 13 is formed in a state where no external magnetic field is applied. The bias magnet 12 is preferably a paste magnet or a thin film magnet that can be formed by a process having a high affinity with a semiconductor process when stacked on the semiconductor substrate 11. The hard magnetic material constituting the magnet is not particularly limited, but samarium-cobalt (SmCo), iron-platinum (FePt), cobalt-platinum (CoPt), neodymium-iron-boron (NdFeB), and the like. Available.

  Paste magnets are formed on either surface of a substrate by a method such as applying a paste-like magnetic material, for example, a hard magnetic paste obtained by mixing magnetic powder such as NdFeB with a binder resin, for example, a phenol epoxy resin. After firing and heating, it can be provided by magnetizing and magnetizing in a predetermined direction.

  The thin film magnet is a sintered magnetic thin film, and its production method is not particularly limited, but includes sputtering, vapor deposition, plating, and printing of a bonded magnet. For patterning the thin film magnet into an arbitrary shape, for example, a photolithography technique such as etching or lift-off can be used. The produced thin film magnet is annealed as necessary, and then magnetized in the magnetic sensitive direction as a magnetic sensor.

  The bias magnet 12 is provided on the other surface 11 b opposite to the one surface 11 a of the semiconductor substrate 11. In this case, since the distance between the bias magnet 12 and the magnetoresistive element 13 is defined by the thickness of the semiconductor substrate 11, the magnetic field applied to the magnetoresistive element can be accurately controlled.

  The arrangement of the magnetoresistive element and the bias magnet with respect to the semiconductor substrate is not limited to that shown in FIG. For example, as shown in FIG. 4, a magnetic switch 40 in which a magnetoresistive element 42 is formed on one surface 41 a of a semiconductor substrate 41 and a bias magnet 43 is arranged on the magnetoresistive element 42 may be used. For example, as shown in FIG. 5, for example, a magnetic switch 50 in which a bias magnet 53 is formed on one surface 51 a of the semiconductor substrate 51 and a magnetoresistive element 52 is disposed on the bias magnet 53 may be used.

  Next, as an operation of the magnetic switch having the above-described configuration, a magnetic field detection method of the present invention will be described with reference to FIGS. The output of the magnetic switch corresponds to two types of strength of the magnetic field, the output at low intensity from the first output unit (OUT1) 21, and the output at high intensity from the second output unit (OUT2) 22. Output each. FIG. 6 shows the output waveform at this time. The output waveform from the first output unit 21 is indicated by OUT1, and the output waveform from the second output unit 22 is indicated by OUT2.

  As shown in FIG. 6, the bias magnet 12 provided on the one surface 11a of the semiconductor substrate 11 shifts the output signals OUT1 and OUT2 output from the first output unit 21 and the second output unit 22, respectively, in the direction of the bias magnetic field. Let In a steady state where no external magnetic field is applied, the shift amount due to the bias magnetic field is set to be between the output signal OUT1 (a) and the output signal OUT2 (a). Accordingly, only the output signal OUT1 (a) operates in the positive magnetic field region, and the output signal OUT2 (a) operates in the negative magnetic field. Therefore, the output signal OUT1 (a) can be output by a positive magnetic field, and the output signal OUT2 (a) can be output by a negative magnetic field.

  In a conventional magnetic switch without a bias magnetic field, that is, without a bias magnet, the output signal is symmetric with respect to the Y axis, as shown in FIG. Only the absolute value of intensity could be detected. However, a bias magnet 12 is provided as in the magnetic switch 10 of the present invention, a bias magnetic field is applied to the magnetoresistive element 13 by the bias magnet 12, and the shift amount due to the bias magnetic field is set between the output signal OUT1 and the output signal OUT2. By setting, a positive magnetic field and a negative magnetic field can be output separately from the first output unit 21 and the second output unit 22, respectively. Thereby, the magnetic switch 10 can perform a switching operation by distinguishing between a positive magnetic field and a negative magnetic field.

  Further, compared with a magnetic switch using a Hall IC or a magnetic switch using an exchange bias by a GMR sensor, such as a conventional magnetic switch that can output by distinguishing between a positive magnetic field and a negative magnetic field, the magnetoresistive element 13 As a means for applying the bias magnetic field, it is only necessary to provide the bias magnet 12 on the one surface 11a of the semiconductor substrate 11. Therefore, a magnetic switch capable of distinguishing and outputting a positive magnetic field and a negative magnetic field at a low cost by a simple manufacturing process is manufactured. It becomes possible to do.

  Further, as a means for applying a bias magnetic field to the magnetoresistive element 13, by using a paste magnet or a sintered thin film magnet, compared with a magnetic switch having a coil for applying a bias magnetic field at the time of operation, A magnetic switch with low power consumption can be realized without having to keep current flowing through the coil.

  In addition, since both the bias magnet 12 and the magnetoresistive element 13 can be formed using a process having a high affinity with a semiconductor process, it is easy to accurately adjust the positional relationship between the magnet and the element. Moreover, since all are laminated | stacked and integrated on a semiconductor substrate, the magnetic switch 10 can be reduced in size.

Hereinafter, specific preparation examples of the magnetic switch of the present invention using a paste magnet as a bias magnet will be listed.
1. First, an MR sensor wafer having two switch outputs according to the strength of the magnetic field is manufactured, and wafer level package processing is performed.
2. Next, a paste-like magnetic material is printed on the back surface of the wafer. The component of the paste magnet is a mixture of NdFeB magnet powder and phenol epoxy resin, and the blending ratio of the magnet and the resin may be about 75:25 by weight ratio.
3. Heat in an oven at 150 ° C. for 30 minutes. The thickness of the paste magnet after heating is 35 to 40 μm, and the thickness is maintained so as not to hinder mounting.
4). Divide into individual elements (dicing). Here, the size of the chip including the bump is, for example, about 0.97 × 0.97 × 0.5 mm.
5). Measure the switching magnetic field of each chip.
6). The paste magnet is magnetized in the coil of the applied magnetic field.
7). Measure the switching magnetic field after magnetization.

Further, specific examples of producing the magnetic switch of the present invention using a sintered thin film magnet as a bias magnet will be listed. The thin film magnet is a magnetized one.
1. First, an MR sensor wafer having two switch outputs according to the strength of the magnetic field is manufactured, and wafer level package processing is performed.
2. Divide into individual elements (dicing). Here, the size of the chip including the bump is, for example, about 0.97 × 0.97 × 0.5 mm.
3. Measure the switching magnetic field of each chip.
4). A die bonder or the like is used to die-bond the sintered thin film magnet on the chip. The material of the sintered thin film magnet is, for example, NdFeB, and the size is, for example, about 0.8 × 0.6 × 0.3 mm. As the adhesive, for example, a silver paste can be preferably used.
5). Measure the switching magnetic field after magnetization.

  FIG. 7 shows an operation comparison of switching magnetic fields before and after magnetization of the magnetic switch of the present invention. According to the waveform diagram shown in FIG. 7, OUT1 and OUT2 exist in pairs in the positive magnetic field region and the negative magnetic field region before magnetization, respectively, but operate with a negative magnetic field after magnetization by applying a bias magnetic field. Is only OUT2, and it was confirmed that the switching operation can be performed by distinguishing between the positive magnetic field and the negative magnetic field.

  Next, the operation of the switching magnetic field after magnetization of the magnetic switch of the present invention is shown in FIG. According to the waveform diagram shown in FIG. 8, OUT2 operates in a negative magnetic field (−1 to −2 mT), and OUT1 operates in a positive magnetic field (0.1 to 0.5 mT). Accordingly, it was confirmed that a positive magnetic field and a negative magnetic field can be distinguished using a magnetic switch having two switch outputs. By setting an appropriate bias magnetic field, the absolute values of the switching magnetic field operations of OUT1 and OUT2 can be made equal.

  An appropriate bias magnetic field setting method is possible by, for example, changing the magnetization magnetic field or material. Further, in FIG. 8, since OUT1 is switched at a magnetic field of 3.5 mT, it can be seen that malfunction occurs when a magnetic field of 3.5 mT or more is applied. On the other hand, no malfunction occurs in the negative magnetic field direction. It has been found that by setting the switching magnetic field of OUT1 and OUT2 without the bias magnet to the high magnetic field side, it is possible to set the magnetic field that causes a malfunction to the high magnetic field side.

It is a top view which shows an example of the magnetic switch of this invention. It is sectional drawing in the AA line of the magnetic switch of FIG. It is a top view which shows the detail of a magnetoresistive element. It is a wave form diagram explaining an effect | action of the magnetic sensor of this invention. It is sectional drawing which shows another example of the magnetic switch of this invention. It is sectional drawing which shows another example of the magnetic switch of this invention. It is a wave form diagram which shows the verification result of this invention. It is a wave form diagram which shows the verification result of this invention. It is explanatory drawing explaining the effect | action of the conventional magnetic sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Magnetic switch, 11 Semiconductor substrate, 12 Bias magnet, 13 Magnetoresistive element, 21 1st output part, 22 2nd output part.

Claims (5)

  A semiconductor substrate, a magnetoresistive element formed on the semiconductor substrate, a bias magnet that applies a bias magnetic field to the magnetoresistive element, and a first output that outputs a voltage corresponding to the strength of an external magnetic field applied to the magnetoresistive element And a second output unit. A magnetic switch comprising:   The first output unit outputs a voltage corresponding to the magnetic field strength of a positive magnetic field among the external magnetic fields applied to the magnetoresistive element, and the second output unit is applied to the magnetoresistive element. 2. The magnetic switch according to claim 1, wherein a voltage corresponding to the magnetic field intensity of a negative magnetic field among the external magnetic fields is output.   The magnetic switch according to claim 1, wherein the bias magnet is formed by applying a paste-like magnetic material.   The magnetic switch according to claim 1, wherein the bias magnet is a sintered magnetic thin film. A semiconductor substrate, a magnetoresistive element formed on the semiconductor substrate, a bias magnet that applies a bias magnetic field to the magnetoresistive element, and a first output that outputs a voltage corresponding to the strength of an external magnetic field applied to the magnetoresistive element Using a magnetic switch having at least a first output portion and a second output portion,
Among the first output signal output from the first output unit and the second output signal output from the second output unit, either one is output as a positive magnetic field and the other is output as a negative magnetic field. A magnetic field detection method, wherein the bias magnetic field is applied to the magnetoresistive element to detect whether the external magnetic field is a positive magnetic field or a negative magnetic field.

Images