JP2800888B2 - Magnetic sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic sensor, and more particularly, to a magnetic sensor in which a ferromagnetic magnetoresistive element and a waveform processing circuit are integrated on a single chip.

[0002]

2. Description of the Related Art As a conventional technique, first, Japanese Patent Laid-Open Publication No.
An integrated magnetoresistive sensor described in Japanese Patent No. 02549 is cited.

The basic structure of the present invention is shown in a circuit diagram of FIG. 3 and a pattern layout diagram of FIG.

According to this example, the magnetoresistive elements 1-4 are set to 1
A bridge that outputs a difference between the potential between −2 and 3-4 is configured, and a voltage signal generated in the bridge is input to the comparator 5. Further, by connecting the non-inverting input terminal of the comparator 5 to an external terminal via the semiconductor resistor 6, the hysteresis of the comparator 5 using an external signal can be adjusted. In the magnetoresistive element, 1 and 4, 2 and 3 are patterned in the same direction, respectively.
1 and 2, 3 and 4 are each patterned in the vertical direction. The resistance of the magnetoresistive element decreases when a magnetic field in the width direction of the pattern is applied.
Since the resistance change hardly occurs in 3, a potential difference occurs in the bridge circuit.

In this example, since the hysteresis control terminal 13 can be externally controlled from the non-inverting input terminal via the semiconductor resistor 6, even if intermittent power is supplied to the power terminal 14, information from an external circuit can be obtained. (High or Low) enables intermittent operation while having hysteresis. That is, the magnetoresistive elements 1 to 4
In addition, the circuit configuration is such that the intermittent operation can be stably performed in order to save the current flowing through the comparator 5.

Reference numeral 15 denotes an output terminal, and 16 denotes a GND terminal.

Next, in the driving circuit of the magnetoresistive element described in Japanese Patent Application Laid-Open No. 3-257287, an intermittent power supply is applied only to the magnetoresistive element portion consuming the largest amount of current, and the analog signal divided into a pulse state is supplied. Is shaped using an integrating circuit.

[0008]

The above prior arts include:
There are the following problems.

A first problem is that, in the prior art, the magneto-resistive element is connected in a bridge form between the power supply and GND.
Since the current flowing through this portion is large, it is difficult to use it for battery driving or the like.

The reason is that it is difficult to realize high resistance because the sheet resistance of the magnetoresistive element is low, and the magnetoresistive effect decreases when the pattern width is reduced.
This is because when the pattern length is increased, the size of the element increases.

The second problem is that, as shown in the prior art, the power supply is intermittently driven to save power, and the intermittent signal is processed by the receiving circuit connected to the back. It is too large to be formed on one chip.

The reason for this is that a circuit for intermittent power supply, a circuit for reproducing an intermittently operated output, and the like are required. If a capacitor such as an integrating circuit is required, it cannot be realized only by a semiconductor integrated circuit, but cannot be realized on a printed circuit board. This is because the circuit occupied by several tens of times in total area ratio is required.

A third problem is that a high-speed response cannot be made.

The reason is that, since the driving is intermittent, only a resistance change sufficiently slower than the driving frequency of the power supply can be detected. In addition, since the power supply also needs time to rise and fall, it can be said that the configuration is not suitable for high-speed operation.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and realizes a magnetic sensor capable of operating at high speed with low power consumption on a one-chip semiconductor integrated circuit with a simple circuit. As an issue. Also, the present invention
Another object is to reduce the number of failures such as disconnection of the pattern and to improve the reliability in order to shorten the pattern length of the element.

[0016]

The magnetic sensor of the present invention comprises:
A composite bridge circuit is formed by combining a magnetoresistive element (MR element) with a semiconductor resistor and a transistor. Specifically, as shown in FIG. 2, the MR element 1 and the MR element 2 are patterned in the same direction, and the MR element 3 and the MR element 4 are patterned in the same direction in a direction perpendicular to the same direction. , 1 and 2, 3 and 4 are set so as to cause a resistance change in pairs. These MR elements 1 to 4 are connected to the bases and collectors of the transistors 11 and 12, respectively, and the semiconductor resistors 7 to 10 connect between the power supply and the base and between the emitter and the ground of each transistor. The magnetic sensor is configured by combining these two sets of composite bridge circuits and the comparator 5.

[0017]

According to the present invention, by forming a composite bridge circuit, a semiconductor resistor and a silane transistor can be incorporated between the power supply and GND in addition to the MR element, so that current consumption can be controlled. In particular, since the semiconductor diffusion resistance can be set to a sufficiently high sheet resistivity as compared with the sheet resistivity of the MR element, high resistance can be obtained with a small area.

Further, in the present invention, the resistance change of the MR element provided between the base of the transistor and GND is represented by
Since the voltage is output as a voltage change from the change in the collector current, the above-mentioned electric conversion efficiency is improved as compared with a simple bridge circuit.

[0019]

Embodiments of the present invention will be described with reference to the drawings.

Referring first to FIG. 2, a preferred embodiment of the present invention is to form a semiconductor integrated circuit 17 on a semiconductor wafer and to form a transistor, a resistor, And a comparator (or an operational amplifier circuit). MR elements (magnetic resistance elements) 1 to 4 are formed in the vicinity of the semiconductor integrated circuit 17 by patterning using photolithography technology. In this example, the MR elements 1 and 2 and the MR elements 3 and 4 are patterned in the same direction. MR element 1
4 is connected to the semiconductor integrated circuit 17 by wiring means.

Next, a circuit forming method will be described with reference to FIG.

The MR element 1 has one terminal connected to the GND terminal 16, the other terminal connected to the base of the transistor 11,
Connected to the semiconductor resistor 7 connected to the power supply line. MR
The element 2 has one terminal connected to the power supply line and the other terminal connected to the collector of the transistor 11 and the input of the comparator 5. The emitter of the transistor 11 is connected to the semiconductor resistor 8
Is connected to the GND terminal 16 via the. The MR element 3
One terminal is connected to the GND terminal 16 and the other terminal is connected to the base of the transistor 12 and the semiconductor resistor 9 connected to the power supply line. The MR element 4 has one terminal connected to the power supply line, the other terminal connected to the collector of the transistor 12, and the input of the comparator 5. The emitter of the transistor 12 is connected to the GND terminal 16 via the semiconductor resistor 10.

The dimensions of the MR element 1 and the MR element 3 are determined so as to have the same resistance value, and the dimensions of the MR element 2 and the MR element 4 are also determined so as to have the same resistance value.

Next, the operation of the embodiment of the present invention will be described with reference to FIGS.

Now, it is assumed that a magnetic field is applied from the left side in FIG. At this time, since the MR elements 1 and 2 have a magnetic field in the width direction of the pattern, the resistance value decreases.
For the MR elements 3 and 4, this magnetic field becomes a magnetic field in the direction perpendicular to the width of the pattern, so that the resistance value does not change. In this state, the operation of FIG. 1 will be described. First, the resistance value of the MR element 1 decreases, so that the base potential of the transistor 11 decreases. As a result, the V _{BE of the} transistor 11 is
, The collector current also decreases. The collector potential V _OUT can be represented by V _OUT = V _CC -MR1 × I _C.

(MRI: resistance value of MR element 1, I _C : collector current of transistor) Also, since the resistance value of MR element 2 is simultaneously reduced,
The collector potential V _OUT when the resistance changes can be expressed by the following equation.

V _OUT = V _CC − (MR 1 −ΔR) × (I _C −ΔI _C ) Therefore, the resistance change of the two MR elements is transmitted to the voltage change by the product.

Similarly, a composite bridge circuit is formed by the MR elements 1 and 2, the MR elements 3 and 4 patterned in the vertical direction, the transistor 12, and the semiconductor resistors 9 and 10. When a magnetic field is applied from above, a change occurs in the collector potential of this circuit.

[0029]

Embodiments of the present invention will be described with reference to the drawings.

Referring first to FIG. 2, according to a first embodiment of the present invention, a bipolar semiconductor integrated circuit 17 is formed on a silicon wafer, and a bipolar transistor for forming a composite bridge with an MR element in the integrated circuit. Diffusion or polysilicon resistors, and comparators (or operational amplifier circuits)
Is formed. In the vicinity of the bipolar semiconductor integrated circuit 17, MR elements (magnetic resistance elements) 1 to 4 made of a thin film alloy of Ni—Fe or Ni—Fe—Co are patterned by photolithography. In this example, the MR elements 1 and 2 and the MR elements 3 and 4 are each patterned in the same direction. The MR elements 1 to 4 are connected to the bipolar semiconductor integrated circuit 17 by using wiring means made of gold or aluminum.

Next, a circuit forming method will be described with reference to FIG.

The MR element 1 has one terminal connected to the GND terminal 16 and the other terminal connected to the base of the bipolar transistor 11 and the semiconductor diffused resistor 7 connected to the power supply line. The MR element 2 has one terminal connected to the power supply line and the other terminal connected to the collector of the bipolar transistor 11 and the input of the comparator 5. The emitter of the bipolar transistor 11 is connected to the G
Connected to ND terminal 16. The MR element 3 has one terminal connected to the GND terminal 16 and the other terminal connected to the base of the bipolar transistor 12 and the semiconductor diffused resistor 9 connected to the power supply line. The MR element 4 has one terminal connected to the power supply line and the other terminal connected to the collector of the bipolar transistor 12 and the input of the comparator 5. The emitter of the bipolar transistor 12 is connected to the GND terminal 16 via the semiconductor diffused resistor 10.

Next, the operation of the embodiment of the present invention will be described with reference to FIGS.

Now, it is assumed that a magnetic field is applied from the left side in FIG. At this time, since the MR elements 1 and 2 have a magnetic field in the width direction of the pattern, the resistance value decreases. For the MR elements 3 and 4, this magnetic field becomes a magnetic field in the direction perpendicular to the width of the pattern, so that the resistance value does not change.
In this state, the operation of FIG. 1 will be described. First, the resistance value of the MR element 1 decreases, so that the base potential of the bipolar transistor 11 decreases. As a result, the V _{BE of the} bipolar transistor 11 decreases, and the collector current also decreases.

The collector potential V _OUT can be represented by the following equation (1).

[0036]

(Equation 1) V _CC: Collector Voltage MR1: resistance of the MR element 1 I _S: collector junction reverse saturation current q: electron charge quantity k: Boltzmann's constant T: absolute temperature In addition, at the same time resistance value MR element 2 is lowered So
The potential V _OUT of the collector when the resistance changes can be expressed by the following equation (2).

[0037]

(Equation 2) Therefore, the resistance change of the two MR elements is transmitted to the voltage change by the product of the exponential function and the exponential function.

Similarly, a composite type bridge circuit is formed by the MR elements 1 and 2, the MR elements 3 and 4 patterned in the vertical direction, the bipolar transistor 12, and the semiconductor resistors 9 and 10. When a magnetic field is applied from above, a change occurs in the collector potential of this circuit.

Next, a second embodiment of the present invention will be described.

In the first embodiment of the present invention, a bipolar semiconductor integrated circuit is used. In the second embodiment, a magnetic sensor is formed by using a MOS semiconductor integrated circuit. in this case,
If the base, emitter, and collector of the bipolar transistor correspond to the gate, source, and drain of the MOS transistor, similar characteristics can be obtained.
An S semiconductor integrated circuit can be used.

[0041]

As is clear from the above description, the present invention has the following effects.

The first effect is that the pattern length of the MR element can be shortened. As a result, the chip area required for the configuration of the magnetic sensor is greatly reduced, and the number of sensors that can be obtained per wafer increases.

The reason is that the impedance between the power supply and the GND is reduced by configuring the semiconductor integrated circuit and the MR element as a composite bridge.

The second effect is that low power consumption can be realized. As a result, power consumption can be reduced even in continuous operation without intermittent driving of the sensor which requires a complicated peripheral circuit.

The reason is that the current consumption can be controlled to any value by changing the design parameters of the composite bridge.

The third effect is that the reliability of the magnetic sensor is improved. Thereby, the reliability of the system employing the present magnetic sensor is improved.

The reason is that M which is formed of a very thin film
This is because the area of the R element portion and the folded portion are reduced, so that the number of locations where a failure easily occurs is relatively reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a magnetic sensor according to an embodiment of the present invention.

FIG. 2 is a pattern layout diagram of a magnetic sensor according to an embodiment of the present invention.

FIG. 3 is a circuit diagram of a conventional magnetic sensor.

FIG. 4 is a pattern layout diagram of a magnetoresistive element portion of a conventional magnetic sensor.

[Explanation of symbols]

 1-4 magnetoresistive (MR) element 5 comparator 6 semiconductor resistor for hysteresis 7-10 semiconductor resistor, semiconductor diffused resistor 11-12 transistor, bipolar transistor 13 external hysteresis terminal 14 power supply terminal 15 output terminal 16 GND terminal 17 semiconductor integrated circuit , Bipolar semiconductor integrated circuit

Claims (3)

(57) [Claims] A plurality of magnetoresistive elements formed by depositing a ferromagnetic alloy thin film on a substrate and patterning the ferromagnetic alloy thin film on a substrate, and a semiconductor integrated circuit formed on the same substrate as the magnetoresistive element. A first magnetoresistive element and a second magnetoresistive element patterned in the same direction, and a third magnetoresistive element patterned in a direction perpendicular to the first magnetoresistive element and the second magnetoresistive element. And a fourth magnetoresistive element, the first and third magnetoresistive elements are dimensioned so as to have the same resistance value, and one terminal is grounded and the other terminal is One magnetoresistive element is connected to the base of the first transistor and the first diffused resistor, and the third magnetoresistive element is connected to the second
Connected to the base of the transistor and the second diffused resistor,
The magnetoresistive element and the fourth magnetoresistive element are also dimensioned so as to have the same resistance value, each having one terminal connected to the power supply line, the other terminal connected to the collector of the first transistor, and the second terminal connected to the collector of the first transistor. And the input terminal of the comparator,
A magnetic sensor characterized in that a circuit is set such that the fourth magnetoresistive element is connected to the collector of the second transistor and the input terminal of the comparator. 2. The magnetic sensor according to claim 1, wherein said semiconductor integrated circuit is a bipolar semiconductor integrated circuit. 3. A plurality of magnetoresistive elements formed by depositing a ferromagnetic alloy thin film on a substrate and patterning it into a specific shape, and a MOS semiconductor integrated circuit formed on the same substrate as the magnetoresistive elements. A first magnetoresistive element and a second magnetoresistive element patterned in the same direction, and a third magnetoresistive pattern patterned in a direction perpendicular to the first magnetoresistive element and the second magnetoresistive element. An element and a fourth magneto-resistive element, the first and third magneto-resistive elements are dimensioned to have the same resistance value, and one of the terminals is grounded,
The other terminal is connected to the first magnetoresistive element to the gate of the first MOS transistor and the first diffused resistor, the third magnetoresistive element is connected to the gate of the second MOS transistor and the second diffused resistor, The magnetoresistive element and the fourth magnetoresistive element are also dimensioned so as to have the same resistance value. One terminal is connected to the power supply line, the other terminal is connected to the power supply line, and the second magnetoresistive element is connected to the drain of the first MOS transistor. And the fourth magneto-resistive element is connected to the second MO
A magnetic sensor, wherein a circuit is set to be connected to a drain of an S transistor and an input terminal of a comparator.