JP2010078360A - Magnetic sensor and magnetic sensor manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic sensor which has superior temperature characteristics and can determine the direction of a magnetic field and a magnetic sensor manufacturing method. <P>SOLUTION: The magnetic sensor 1 includes a semiconductor chip 3 formed with first to fourth GMR elements 30 to 33 and a magnet 2 arranged on the back of the installation surface of a lead frame 10. A first magnetic vector 21 acts on the first and third GMR elements 30, 32 by the magnet 2, while a second magnetic vector 22, which is opposite in direction to the first magnet vector 21, acts on the second and fourth GMR elements 31, 33. The magnetic sensor 1 is formed with a first half-bridge circuit 34 by the first GMR element 30 and the second GMR element 31 and is formed with a second half-bridge circuit 35 by the fourth GMR element 33 and the third GMR element 32. By calculating the difference between the output voltages V1 and V2 of the first and second half-bridge circuits 34, 35, respectively, the direction of an external magnetic field 4 can be determined. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic sensor and a method for manufacturing the magnetic sensor.

  As a conventional technique, a first half magnetoresistive element whose magnetoresistance value changes according to a change in the direction of an external magnetic field and a first fixed resistor having a resistance value that is not affected by the external magnetic field are connected in series. A second half bridge in which a bridge circuit, a second giant magnetoresistive element whose magnetoresistance value changes according to a change in the direction of the external magnetic field, and a second fixed resistor having a resistance value not affected by the external magnetic field are connected in series Difference between the first output voltage that is the midpoint potential of the first half-bridge circuit and the second output voltage that is the midpoint potential of the second half-bridge circuit. A magnetic switch including a detection circuit that calculates a value and outputs a switching signal by comparing the difference value with a threshold value is known (see, for example, Patent Document 1).

According to this magnetic switch, when the first and second giant magnetoresistive elements are manufactured, adjacent to each other from the wafer on which a large number of giant magnetoresistive elements in which the magnetization directions of the respective layers are formed in the same state are arranged. Since a pair of giant magnetoresistive elements can be cut out as a single substrate, it is not necessary to perform alignment work, and assembly work can be facilitated.
JP 2007-220367 A

  However, in the conventional magnetic switch, the first and second giant magnetoresistive elements and the first and second resistive elements have different resistance temperature coefficients. There was a problem that the accuracy changed. Further, the conventional magnetic switch has a problem that the direction of the magnetic field cannot be determined because the giant magnetoresistive element does not have anisotropy.

  Accordingly, an object of the present invention is to provide a magnetic sensor that has excellent temperature characteristics and can determine the direction of a magnetic field, and a method for manufacturing the magnetic sensor.

(1) In order to achieve the above object, the present invention provides a magnetic field generator for generating a magnetic field in a first direction and a second direction opposite to the first direction, and a voltage at one end. A first giant magnetoresistive element provided at a position where the magnetic field in the first direction generated from the magnetic field generator is applied, one end is grounded, and the other end is the first giant magnetoresistive element A second giant magnetoresistive element connected to the element to form a first half-bridge circuit and provided at a position where the magnetic field in the second direction generated from the magnetic field generator acts; A third giant magnetoresistive element provided at a position where the magnetic field in the first direction generated from the magnetic field generator is applied, the voltage is applied to one end, and the other end is the third giant magnetoresistive element. The second half bridge is connected to the magnetoresistive element. Constitute a circuit, to provide a magnetic sensor in which the magnetic field of said generated second direction is provided with a fourth giant magnetoresistive element provided in a position acting from the magnetic field generator.

(2) In order to achieve the above object, the first to fourth giant magnetoresistive elements are provided on a plane perpendicular to the magnetization direction of the magnetic field generating unit. Provide a sensor.

(3) In order to achieve the above object, the magnetic field generator is magnetized after being sealed with resin together with the first to fourth giant magnetoresistive elements. Provide a sensor.

(4) In order to achieve the above object, the first giant magnetoresistive element has substantially the same shape as the third giant magnetoresistive element, and the third giant magnetoresistive element. And the second giant magnetoresistive element has a shape substantially the same as the shape of the fourth giant magnetoresistive element, and the fourth giant magnetoresistive element The magnetic sensor according to (1), which is disposed so as not to overlap a gap formed in the above.

(5) In order to achieve the above object, the present invention provides the magnetic sensor according to (1), wherein the magnetic field generation unit is formed with the first to fourth giant magnetoresistive elements.

(6) In order to achieve the above object, the present invention provides a manufacturing process for manufacturing a semiconductor chip having a full bridge circuit composed of first to fourth giant magnetoresistive elements, and a first step of mounting the semiconductor chip on a lead frame. 1 mounting step, a second mounting step of mounting a magnetic member on a surface facing the mounting surface of the lead frame on which the semiconductor chip is mounted, a pad provided on the semiconductor chip, and the pad corresponding to the pad A wiring step for wiring with a predetermined place of the lead frame, a sealing step for sealing the lead frame, the semiconductor chip and the magnetic member with a resin, a magnetization step for magnetizing the magnetic member, The manufacturing method of the magnetic sensor provided with this is provided.

  According to such an invention, the temperature characteristic is excellent and the direction of the magnetic field can be determined.

  Embodiments of a magnetic sensor and a method for manufacturing the magnetic sensor according to the present invention will be described below in detail with reference to the drawings.

[Embodiment]
(Configuration of magnetic sensor)
FIG. 1 is a schematic view of a magnetic sensor according to an embodiment of the present invention, and FIG. 2A is a diagram illustrating first and second GMRs (Giant Magneto Resistance) according to an embodiment of the present invention. FIG. 4 is a schematic diagram regarding the arrangement of element groups, and FIG. 2A and 2B show the inside of the magnetic sensor 1.

  As shown in FIG. 1, the magnetic sensor 1 is a resin-encapsulated semiconductor device. The magnetic sensor 1 is electrically formed by a resin mold 12 formed of resin to protect the inside, and a wiring pattern and solder of a substrate to be mounted. A plurality of outer leads 11 connected to each other.

  Further, as shown in FIGS. 2A and 2B, the magnetic sensor 1 is a magnet provided on a surface facing the mounting surface of the lead frame 10 and the lead frame 10 on which the semiconductor chip (chip) 3 is mounted. (Magnetic field generator) 2, first and second GMR element groups 3A and 3B, first to fourth pads (pads) 300 to 303, and first to fourth pads (pads) 310 to 313 The semiconductor chip 3 is formed and schematically configured.

(Lead frame configuration)
The lead frame 10 is manufactured from a metal thin plate by pressing or etching, and has an island (not shown) provided in the center and a plurality of inner leads (not shown) electrically independent of the island. The inner lead is electrically connected to the outer lead 11.

(Composition of magnet)
As shown in FIGS. 2A and 2B, the magnet 2 has a rectangular shape, and its magnetization direction is N pole and S pole from the lead frame 10 side, and a magnetic path from the N pole to the S pole. Is generated. The semiconductor chip 3 is disposed on a plane perpendicular to the magnetization direction. This magnetization direction is not limited to this, and the lead frame 10 side may be the south pole.

  As shown in FIG. 2A, the magnet 2 generates a magnetic field 20 in the direction (first direction) shown as the first magnetic vector 21 with respect to the first GMR element group 3A. A magnetic field 20 is generated in the direction indicated by the second magnetic vector 22 (second direction) for the GMR element group 3B. The first and second magnetic vectors 21 and 22 indicate the strength and direction of the magnetic field 20 in the plane in which the first and second GMR element groups 3A and 3B are formed.

  The magnet 2 is, for example, a resin in which a magnetic member such as flight or neodymium is mixed, and after the resin mold 12 is formed, the magnet 2 is magnetized in the above magnetization direction by a magnetizing device. Therefore, since the magnet 2 is magnetized after being sealed by the resin mold 12, it is easy to mount and to provide a magnetic sensor with small variations in characteristics.

  As shown in FIG. 2B, the magnet 2 is mounted on the back surface side of the mounting surface of the lead frame 10, but the present invention is not limited to this, and the first and second GMR elements are used based on the application. A magnetic film may be formed below or above the groups 3A and 3B, the first to fourth pads 300 to 303, and the first to fourth pads 310 to 313. Since the magnet 2 is formed as a magnet film, the magnetic sensor 1 is smaller and can reduce variations in sensor characteristics.

(Configuration of semiconductor chip)
As an example, the semiconductor chip 3 is formed with first and second GMR element groups 3A and 3B, first to fourth pads 300 to 303, and first to fourth pads 310 to 313 on a wafer by photolithography. The semiconductor element is cut into a predetermined size. Since the semiconductor chip 3 is cut out from the wafer, the magnetic sensor 1 can perform highly accurate detection by using the first to fourth GMR elements 30 to 33 having uniform characteristics.

(Configuration of first GMR element group)
FIG. 3A is a schematic diagram of the first GMR element group according to the embodiment of the present invention, and FIG. 3B is a schematic diagram of the second GMR element group.

  As shown in FIG. 3A, the first GMR element group 3A includes a first GMR element (first giant magnetoresistive element) 30 and a third GMR element (third giant magnetoresistive element). 32, first and second pads 300 and 301 that are electrode pads of the first GMR element 30, and third and fourth pads 302 and 303 that are electrode pads of the third GMR element 32. In general, it is structured. The first to fourth pads 300 to 303 are wired at predetermined locations on the lead frame 10 by wire bonding.

  As shown in FIG. 3A, the first GMR element 30 has, for example, a plurality of folded shapes, in other words, loose shapes, and substantially the same shape based on the loose shapes. 32 has.

  Specifically, the first and third GMR elements 30 and 32 are arranged in combination so that their shapes are inverted and fit into the respective gaps, that is, the region occupied by the first GMR element 30 and the third The external magnetic field 4 and the magnetic field 20 act on both the first and third GMR elements 30 and 32 in the same manner, that is, the external magnetic field 4. And the same magnetic resistance value by the action of the magnetic field 20.

(Configuration of second GMR element group)
As shown in FIG. 3B, the second GMR element group 3B includes a second GMR element (second giant magnetoresistive element) 31 and a fourth GMR element (fourth giant magnetoresistive element). 33, first and second pads 310 and 311 which are electrode pads of the second GMR element 31, and third and fourth pads 312 and 313 which are electrode pads of the fourth GMR element 33. In general, it is structured. The first to fourth pads 310 to 313 are wired at predetermined locations on the lead frame 10 by wire bonding.

  As an example, as shown in FIG. 3A, the second GMR element 31 has a plurality of folded shapes, in other words, a loose shape, and a substantially identical shape based on the loose shape is the fourth GMR element. 33 has.

  Specifically, the second and fourth GMR elements 31 and 33 are arranged in combination so that their shapes are inverted and fit into the respective gaps, that is, the region occupied by the second GMR element 31 and the fourth And the external magnetic field 4 and the magnetic field 20 act on both the second and fourth GMR elements 31 and 33 in the same manner, that is, the external magnetic field 4. And the same magnetic resistance value by the action of the magnetic field 20.

  Moreover, the 1st-4th GMR elements 30-33 are roughly comprised from the multilayer film which laminated | stacked the magnetic layer and the nonmagnetic layer as an example.

  This magnetic layer is configured so that the magnetization direction is changed by a magnetic field acting from the outside. When no magnetic field is acting from the outside, the magnetization direction of the magnetic layer is alternated by the exchange interaction, and from the outside. When the magnetic field acts, the magnetization direction of the magnetic layer is configured to be aligned in one direction.

  In the first to fourth GMR elements 30 to 33, when the magnetization direction in the magnetic layer changes, the magnetoresistance value changes, and when the magnetization direction of the magnetic layer is aligned, the magnetoresistance value becomes small and alternately. The magnetic resistance value increases when

  As is well known, the first to fourth GMR elements 30 to 33 can obtain a linear change in magnetoresistance depending on the thickness of the nonmagnetic layer.

  The first to fourth GMR elements 30 to 33 are arranged at substantially the same temperature conditions and are formed on the semiconductor chip 3, so that their temperature characteristics are equal. Therefore, the magnetic sensor 1 can accurately detect a change in the magnetic field even with respect to a temperature change. This indicates that the magnetic sensor 1 can operate with high accuracy even if it is mounted on a vehicle that requires high heat resistance.

(About connection of the first to fourth GMR elements)
FIG. 4 is an equivalent circuit diagram of the magnetic sensor according to the embodiment of the present invention. As shown in FIG. 4, the magnetic sensor 1 includes a first half by a first GMR element 30 on which a first magnetic vector 21 acts and a second GMR element 31 on which a second magnetic vector 22 acts. A bridge circuit 34 is formed, and a second half bridge circuit 35 is formed by the third GMR element 32 on which the first magnetic vector 21 acts and the fourth GMR element 33 on which the second magnetic vector 22 acts. In addition, a full bridge circuit is formed by the first and second half bridge circuits 34 and 35.

  As an example, the applied voltage Vcc supplied from the power supply circuit of the substrate to be mounted is applied between the first GMR element 30 and the fourth GMR element 33, and the second GMR element 31. The third GMR element 32 is connected to the ground circuit of the substrate on which it is mounted, and the first half-bridge circuit 34 is the midpoint voltage of the first GMR element 30 and the second GMR element 31. The output voltage V <b> 1 is output, and the second half bridge circuit 35 outputs an output voltage V <b> 2 that is a midpoint voltage between the fourth GMR element 33 and the third GMR element 32.

  FIG. 5 is a graph showing the relationship between the output voltage and the external magnetic field according to the embodiment of the present invention. In this graph, the output voltage V (mV) is plotted on the vertical axis, the magnetic field strength B (mT) is plotted on the horizontal axis, the applied voltage Vcc is 5 V, and the magnetic field strength of the external magnetic field 4 is changed. is there. In addition, when the external magnetic field 4 takes a positive value shown in FIG. 5, as an example, it shows that the external magnetic field 4 is applied in the direction of the arrow shown in FIG. 4, and when taking a negative value, As an example, it is assumed that the external magnetic field 4 in the direction opposite to the direction of the arrow shown in FIG. 4 is applied.

  The output voltage V is a difference value between the output voltage V1 of the first half bridge circuit 34 and the output voltage V2 of the second half bridge circuit 35, and the output voltage V = V1−V2.

(Operation)
Hereinafter, operations related to the magnetic sensor according to the present embodiment will be described in detail with reference to the drawings. First, the manufacturing method of the magnetic sensor 1 will be described based on the flowchart of FIG.

  First, the first to fourth GMR elements 30 to 33, the first to fourth pads 300 to 303, and the first to fourth pads 310 to 313 are formed on the wafer by photolithography, and subjected to a predetermined process. Then, the semiconductor chip 3 is cut out from the wafer (S1; production process).

  The semiconductor chip 3 is bonded to the island of the lead frame 10 with an adhesive or the like, and the semiconductor chip 3 is mounted on the lead frame 10 (S2; first mounting step).

  A magnet member that has not yet been magnetized is bonded to the back side of the mounting surface of the lead frame 10 on which the semiconductor chip 3 is mounted with an adhesive or the like (S3; second mounting step).

  The first to fourth pads 300 to 303 and the first to fourth pads 310 to 313 are wired to predetermined locations of the lead frame 10 by wire bonding (S4; wiring step).

  After the unnecessary portion of the lead frame 10 is cut off, the whole is sealed with resin so that the outer lead 11 comes out, a resin mold 12 is formed, and the resin is completely cured at a predetermined temperature (S5; sealing) Process).

  The magnet member is magnetized by the magnetizing device to form the magnet 2, and the outer lead 11 is bent to manufacture the magnetic sensor 1 (S6; magnetizing step).

(Operation of magnetic sensor)
Next, the operation of the magnetic sensor 1 will be described in detail with reference to the drawings. As shown in FIG. 4, when the external magnetic field 4 acts on the magnetic sensor 1, the external magnetic field 4 is in the same direction as the first magnetic vector 21 and is opposite in direction to the second magnetic vector 22. Yes.

  Since the direction of the external magnetic field 4 is the same as that of the first magnetic vector 21, the first and third GMR elements 30, 32 in which the magnetic field 20 acts in the direction of the first magnetic vector 21 have their magnetoresistance. The value is smaller than the magnetoresistance value when the external magnetic field 4 does not act.

  Further, the second and fourth GMR elements 31 and 33 in which the magnetic field 20 acts in the direction of the second magnetic vector 22 have the direction of the external magnetic field 4 opposite to that of the second magnetic vector 22. The magnetoresistance value is larger than the magnetoresistance value when the external magnetic field 4 does not act.

  The output voltage V1 output from the first half-bridge circuit 34 is proportional to the ratio between the magnetoresistance value of the second GMR element 31 and the total magnetoresistance value of the first and second GMR elements 30 and 31, The output voltage V2 output from the second half-bridge circuit 35 is proportional to the ratio of the magnetoresistance value of the third GMR element 32 and the total magnetoresistance value of the third and fourth GMR elements 32 and 33. Therefore, V2 <V1, and the output voltage V, which is the difference value, is a positive value.

  When the external magnetic field 4 does not act on the magnetic sensor 1, the first to fourth GMR elements 30 to 33 have the same magnetic resistance value. As shown, it is 0 mv.

  When the external magnetic field 4 is in the direction opposite to the direction indicated by the arrow in FIG. 4, that is, when the strength of the external magnetic field 4 is a negative value, the external magnetic field 4 has the first magnetic vector as described above. 21 is the opposite direction to the second magnetic vector 22 and acts from the same direction as the second magnetic vector 22. Therefore, the magnetoresistance value of the second GMR element 31 is smaller than the magnetoresistance value when the external magnetic field 4 does not act. Thus, the magnetoresistance value of the third GMR element 32 is larger than the magnetoresistance value when the external magnetic field 4 does not act.

  Therefore, V1 <V2, and the output voltage V, which is the difference value, becomes a negative value as shown in FIG.

  Since the first to fourth GMR elements 30 to 33 can obtain almost linear changes in magnetoresistance, the magnetic sensor 1 outputs output voltages V1 and V2 for determining the direction of the external magnetic field 4 as shown in FIG. Can be output.

(effect)
(1) According to the magnetic sensor 1 in the above-described embodiment, the direction of the magnetic field can be determined using the GMR element.

(2) According to the magnetic sensor 1 in the above-described embodiment, since the first to fourth GMR elements 30 to 33 are arranged at close positions, the first to fourth GMR elements 30 to 33 are the same. Since the temperature is changed, and the change in the external magnetic field 4 is detected by the difference value between the output voltages V1 and V2 from the first and second half bridge circuits 34 and 35, the temperature characteristics are excellent.

(3) According to the magnetic sensor 1 in the above-described embodiment, since the first to fourth GMR elements 30 to 33 are used, a linear and high output voltage V can be obtained.

(4) According to the magnetic sensor 1 in the above-described embodiment, the first and third GMR elements 30 and 32 and the second and fourth GMR elements 31 and 33 are configured such that the occupied regions overlap each other. In other words, the magnetoresistance values of the first and third GMR elements 30 and 32 and the second and fourth GMR elements 31 and 33 that are arranged so as to fit in the gaps between the shapes and are arranged in the same region. Therefore, the magnetic field can be detected more accurately.

(5) According to the magnetic sensor 1 in the above-described embodiment, since the magnet 2 can be formed together with the first to fourth GMR elements 30 to 33, the size can be further reduced. Variations in characteristics can be reduced.

(6) The magnetic sensor 1 in the above-described embodiment can be reduced in variation in sensor characteristics by being a resin-sealed type.

(7) According to the manufacturing method of the magnetic sensor 1 in the above-described embodiment, the magnet 2 can be magnetized after the resin mold 12 is formed.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from or changing the technical idea of the present invention.

FIG. 1 is a schematic view of a magnetic sensor according to an embodiment of the present invention. FIG. 2A is a schematic diagram relating to the arrangement of the first and second GMR element groups according to the embodiment of the present invention, and FIG. 2B is a side view. FIG. 3A is a schematic diagram of the first GMR element group according to the embodiment of the present invention, and FIG. 3B is a schematic diagram of the second GMR element group. FIG. 4 is an equivalent circuit diagram of the magnetic sensor according to the embodiment of the present invention. FIG. 5 is a graph showing the relationship between the output voltage and the external magnetic field according to the embodiment of the present invention. FIG. 6 is a flowchart relating to the manufacture of a magnetic sensor according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Magnetic sensor, 2 ... Magnet, 3 ... Semiconductor chip, 3A ... 1st GMR element group, 3B ... 2nd GMR element group, 4 ... External magnetic field, 10 ... Lead frame, 11 ... Outer lead, 12 ... Resin Mold, 20 ... magnetic field, 21 ... first magnetic vector, 22 ... second magnetic vector, 30 ... first GMR element, 31 ... second GMR element, 32 ... third GMR element, 33 ... fourth 34 ... first half bridge circuit, 35 ... second half bridge circuit, 300 to 303 ... first to fourth pads, 310 to 313 ... first to fourth pads, V ... output voltage , V1 ... output voltage, V2 ... output voltage, Vcc ... applied voltage

Claims (6)

A magnetic field generator for generating a magnetic field in a first direction and a second direction opposite to the first direction;
A first giant magnetoresistive element provided at a position where a voltage is applied to one end and the magnetic field in the first direction generated from the magnetic field generating unit acts;
A position where one end is grounded and the other end is connected to the first giant magnetoresistive element to form a first half-bridge circuit, and the magnetic field in the second direction generated from the magnetic field generating unit acts A second giant magnetoresistive element provided in
A third giant magnetoresistive element provided at a position where one end is grounded and the magnetic field in the first direction generated from the magnetic field generating unit acts;
The voltage is applied to one end and the other end is connected to the third giant magnetoresistive element to form a second half-bridge circuit, and the magnetic field in the second direction generated from the magnetic field generator is A fourth giant magnetoresistive element provided at the position of action;
Magnetic sensor equipped with.   The magnetic sensor according to claim 1, wherein the first to fourth giant magnetoresistive elements are provided on a plane perpendicular to a magnetization direction of the magnetic field generation unit.   The magnetic sensor according to claim 1, wherein the magnetic field generator is magnetized after being sealed with resin together with the first to fourth giant magnetoresistive elements. The first giant magnetoresistive element has substantially the same shape as the third giant magnetoresistive element, and is disposed so as not to overlap a gap formed in the third giant magnetoresistive element.
The second giant magnetoresistive element has substantially the same shape as that of the fourth giant magnetoresistive element, and is disposed so as not to overlap a gap formed in the fourth giant magnetoresistive element. The magnetic sensor according to claim 1.   The magnetic sensor according to claim 1, wherein the magnetic field generator is formed together with the first to fourth giant magnetoresistive elements. A production process for producing a semiconductor chip having a full bridge circuit composed of first to fourth giant magnetoresistive elements;
A first mounting step of mounting the semiconductor chip on a lead frame;
A second mounting step of mounting a magnetic member on a surface facing the mounting surface of the lead frame on which the semiconductor chip is mounted;
A wiring step of performing wiring between a pad provided on the semiconductor chip and a predetermined location of the lead frame corresponding to the pad;
A sealing step of sealing the lead frame, the semiconductor chip and the magnetic member with a resin;
A magnetization step of magnetizing the magnetic member;
A method of manufacturing a magnetic sensor comprising:

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