JP2005056950A - Magnetoresistive element and magnetic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To constitute a magnetoresistive element as a structural body excellent in temperature characteristic by exactly measuring a change in weak magnetic field intensity even if all the magnetoresistive elements are disposed in a constant magnetic field. <P>SOLUTION: A three terminal magnetoresistive element or a four terminal magnetoresistive element is formed by a plurality of magnetoresistive elements in which a thin-film layer formed by growing a semiconductor crystal on a substrate is used as an operating layer of a magnetosensitive section. Impurities for increasing the number of carriers are doped in the operating layer to increase carriers, and the magnetoresistive effect of the plurality of magnetoresistive elements are made so that a change in magnetic reluctance rate to a change in magnetic flux density due to an external magnetic field differ from each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetoresistive element and a magnetic sensor, and more particularly, to a magnetoresistive element having high sensitivity and excellent temperature stability for detecting magnetic patterns such as banknotes and detecting rotation of gears.

  In general, a magnetoelectric conversion element applies a bias between the input terminals of an element, and a path of a carrier flowing in the element changes according to a change in a surrounding magnetic field. An element that can measure the magnetic field intensity by changing the resistance value. There exists a magnetoresistive element as an element from which the resistance value of the element changes.

  As the use of the magnetoresistive element, the magnetic sensor is provided as a detection element for detecting a magnetic pattern of a magnetic printed matter represented by a bill or the like, or detecting a rotation of a gear made of a ferromagnetic material. . A magnetic pattern is printed on the magnetic print using magnetic ink. This printed magnetic pattern has a planar structure made of magnetic fine particles (hereinafter referred to as magnetic powder) formed on the surface or inside of the substrate.

  The conventional magnetoresistive element is configured as a three-terminal or four-terminal magnetoresistive element for the above-described applications.

  FIG. 23 shows a configuration example of a conventional three-terminal magnetoresistive element.

  The three-terminal magnetoresistive element has a first terminal electrode 1, a second terminal electrode 2 (that is, an output terminal 2), and a third terminal electrode 3 as terminal electrodes for external connection, and the magnetoresistive elements 4, 5, A short-circuit electrode 6 is provided.

  As shown in FIG. 24, the magnetoresistive elements 4 and 5 are connected in series, and the first terminal electrode 1 and the third terminal electrode 3 are connected to a constant voltage power source Vin (hereinafter, this connection form is referred to as a half-bridge circuit). Called).

  Such a three-terminal magnetoresistive element is often used for magnetic pattern detection and gear rotation detection, and a four-terminal magnetoresistive element is often used for gear rotation detection.

  25 and 26 show the principle of detecting a magnetic pattern such as banknotes using a three-terminal magnetoresistive element.

  The magnetoresistive elements (MR elements) 4 and 5 are arranged close to each other in a uniform bias magnetic field formed by the permanent magnet 15. A magnetic printed matter 16 on which a magnetic pattern is printed is scanned facing the magnetoresistive elements 4 and 5. The magnetic pattern is composed of magnetic ink 17 containing magnetic powder.

  A detection signal when the magnetic ink 17 containing magnetic powder is scanned in the three-terminal magnetoresistive element including the half-bridge circuit of FIG. 24 will be described.

  When the magnetic print 16 is scanned, the position changes in the order of positions P → Q → R in FIG. The scanning direction of the magnetic print 16 is from left to right.

  In the state of FIG. 25A, the magnetic flux density immediately below the magnetoresistive element 4 increases, and the resistance value of the magnetoresistive element 4 increases. As a result, the potential of the output terminal 2 is increased. The arrows in the figure represent magnetic field lines.

  In the state of FIG. 25 (b), the magnetic flux densities immediately below the magnetoresistive elements 4 and 5 are equal and the resistance value is also the same. As a result, the output terminal 2 is in an intermediate state.

  In the state of FIG. 25C, the magnetic flux density immediately below the magnetoresistive element 5 increases, and the resistance value of the magnetoresistive element 5 increases. As a result, the potential of the output terminal 2 is lowered.

  Thus, by scanning the magnetic printed matter 16, a detection signal having a differential waveform as shown in FIG. 26 is obtained (hereinafter referred to as a spatial difference detection method). The advantages of this conventional spatial difference detection method are disclosed in Patent Document 1 and Patent Document 2.

  FIG. 27 shows the principle of detecting the rotation of a gear using a three-terminal magnetoresistive element.

  The magnetoresistive elements 4 and 5 are connected in series as shown in the half-bridge circuit of FIG. 24 and are also connected to a constant voltage power source Vin.

  As shown in FIG. 29, the distance between the centers of the magnetoresistive elements 4 and 5 is adjusted to the distance between the peaks and valleys of the gear 18 made of iron or the like.

  With this arrangement, the principle of scanning of the magnetic printed matter 16 described with reference to FIG. 25 can be applied as it is, and when the gear 18 is rotated, a sin waveform is applied to the output terminal 2 of the half bridge circuit as shown in FIG. can get.

  FIG. 30 shows a configuration example of a conventional four-terminal magnetoresistive element.

  This four-terminal magnetoresistive element has a first terminal electrode 7, a second terminal electrode 8, a third terminal electrode 9, and a fourth terminal electrode 10 as terminal electrodes for external connection, and further includes four magnetoresistive resistors. Elements 11, 12, 13, and 14 are provided.

  In this four-terminal magnetoresistive element, the magnetoresistive elements 11, 12, 13, and 14 are connected in a loop shape, and the first terminal electrode 7 and the third terminal electrode 9 are connected to a constant voltage power source Vin (hereinafter referred to as “the constant voltage power source Vin”). This connection form is called a full bridge circuit).

  FIG. 32 shows an example when a four-terminal magnetoresistive element is used.

  The output signal waveform as shown in FIG. 33 is obtained at the output terminal (−) 8 of the full bridge circuit shown in FIG. 31, and the waveform of the output signal as shown in FIG. 34 is obtained at the output terminal (+) 10. Is obtained.

  The waveform of the output signal in FIG. 34 has a phase shifted by a half cycle with respect to the waveform of the output signal in FIG. 33, and the output voltage is changed between the output terminal (−) 8 and the output terminal (+) 10. It is common to get.

  In this way, the amplitude of the output signal is twice that of the waveform of FIG. 26, and finally the waveform of the output signal as shown in FIG. 35 is obtained. The rotation detection of the gear is also based on the spatial difference detection method.

JP 52-73793 A JP-A-52-73794

  For the three-terminal magnetoresistive element in FIG. 24 as described above, when the magnetic field in the magnetoresistive element 4 and the magnetic field in the magnetoresistive element 5 are different, the four-terminal magnetoresistive element in FIG. When the magnetic field at 13 and the magnetic fields at the magnetoresistive elements 12 and 14 are different, the detection can be performed efficiently.

  However, the first problem is that these three-terminal magnetoresistive elements and four-terminal magnetoresistive elements cannot accurately measure the magnetic field strength when all of the magnetoresistive elements are placed in a uniform magnetic field. There is.

  That is, in a three-terminal magnetoresistive element, when the entire element is placed in a uniform magnetic field, the magnetoresistive elements 4 and 5 both increase in resistance in the same manner, so that an output signal can be obtained from the output terminal 2. The phenomenon of not occurring occurs. The same problem occurs with a four-terminal magnetoresistive element.

  As a second problem, in the three-terminal magnetoresistive element, when the resistance value of the magnetoresistive element 3 and the resistance value of the magnetoresistive element 4 are different, the output terminal 2 has 1/2 of the input voltage Vin (Vin / 2), and if the temperature coefficient of the resistance value of each magnetoresistive element is different, the output voltage value of the output terminal 2 causes a temperature drift.

  The cause of the difference in the temperature coefficient of the resistance value may be nonuniformity between the magnetoresistive element 3 and the magnetoresistive element 4 having an impurity concentration that determines the temperature change of the electrical conductivity of the semiconductor that is the operation layer.

  In a three-terminal magnetoresistive element configured with a half bridge circuit as shown in FIG. 24, if the temperature coefficient of the resistance value is different, the output voltage output from the output terminal 2 will drift in temperature.

  Further, in the four-terminal magnetoresistive element configured by a full bridge circuit as shown in FIG. 31, when the resistance value of the magnetoresistive element 11 and the resistance value of the magnetoresistive element 12 are different, When the resistance value and the resistance value of the magnetoresistive element 14 are different, the output terminals 8 and 10 have a problem that the output voltage does not become zero and an offset voltage is generated even when the magnetic field is zero.

  Furthermore, when the conventional 3-terminal magnetoresistive element or 4-terminal magnetoresistive element is mounted on one surface of a permanent magnet and configured as a magnetic sensor to detect a magnetic pattern of a magnetic print, Detecting the edge part of the magnetic pattern, that is, only detecting the presence or absence of the pattern, faithfully and accurately detecting the change in magnetic flux corresponding to the slight shading change of the magnetic powder contained in the magnetic pattern Is impossible.

  Therefore, an object of the present invention is to accurately measure a weak change in magnetic field strength even when all magnetoresistive elements are arranged in a uniform or constant magnetic field and to have excellent temperature characteristics. An object of the present invention is to provide a magnetoresistive element and a magnetic sensor that can be configured as a structure.

  According to the present invention, a three-terminal magnetoresistive element or a four-terminal magnetoresistive element is constituted by a plurality of magnetoresistive elements having a thin film layer obtained by growing a semiconductor crystal on a substrate as an operating layer of a magnetosensitive portion. Since an impurity for increasing carriers is added to the layer, the magnetic and electrical characteristics between the magnetoresistive elements can be made uniform, and the magnetoresistive effect of the plurality of magnetoresistive elements is Since the rate of change in magnetic resistance with respect to the change in magnetic flux density due to an external magnetic field is made different from each other, even if all magnetoresistive elements are placed in a uniform or constant magnetic field, the weak change in magnetic field strength can be accurately detected. In addition, the structure can be configured as a structure having excellent temperature characteristics.

  Further, according to the present invention, by configuring as a magnetic sensor including a three-terminal magnetoresistive element or a four-terminal magnetoresistive element, not only detection of the edge portion of the magnetic pattern, that is, detection of the presence or absence of the pattern, It is also possible to detect a slight change in shading, and it is also possible to perform highly accurate detection even when detecting rotation of a gear or the like.

  In the present invention, two magnetoresistive elements are connected in series, thereby having three terminals of first and second input terminals for applying an external voltage and one output terminal for taking out an output signal. Each of the magnetoresistive elements is a thin film magnetoresistive element having a thin film layer obtained by growing a semiconductor crystal on a substrate as an operating layer of the magnetosensitive portion, and the operation of the semiconductor thin film magnetoresistive element. The layer is a semiconductor thin film to which an impurity for increasing carriers is added as an operating layer, and the composition of the operating layer is InxGa1-xAsySb1-y (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) The impurity is silicon or tin, the magnetoresistive element connected between the first input terminal and the output terminal, and the magnetoresistive element connected between the output terminal and the second input terminal. A magnetoresistive element is an external magnetic field. By magnetoresistance ratio comprises different magnetoresistive each other with respect to a change in flux density, constituting a three-terminal magneto-resistance element.

  Here, the magnetoresistive element connected between the first input terminal and the output terminal has a short-circuit electrode, and the magnetism connected between the output terminal and the second input terminal. The resistance element may not have a short-circuit electrode.

  A resistance value of the magnetoresistive element connected between the first input terminal and the output terminal, and a resistance value of the magnetoresistive element connected between the output terminal and the second input terminal. And may be equal to each other.

  The present invention is a magnetic sensor for detecting a signal by utilizing a magnetoresistive effect of a magnetoresistive element, the three-terminal magnetoresistive element and a magnetic field applying means for applying an external magnetic field to the three-terminal magnetoresistive element. Here, all the two magnetoresistive elements constituting the three-terminal magnetoresistive element are mounted on the same surface of the magnetic field applying means and disposed in a constant magnetic field of the external magnetic field. In the configuration, the magnetic sensor may be configured by detecting an output signal output from an output terminal configuring the three-terminal magnetoresistive element based on different magnetoresistive effects of the magnetoresistive elements.

  In the present invention, four terminals, that is, first and second input terminals for applying an external voltage and two output terminals for extracting an output signal are provided by connecting four magnetoresistive elements in a closed loop circuit. The four terminals are configured to be connected in the order of the first input terminal, the first output terminal, the second input terminal, and the second output terminal along one direction in the closed loop circuit. The magnetoresistive element is a thin film magnetoresistive element having a thin film layer obtained by growing a semiconductor crystal on a substrate as an operating layer of a magnetosensitive portion, and the operating layer of the semiconductor thin film magnetoresistive element The semiconductor thin film to which an impurity for increasing carriers is added is used as an operating layer, and the composition of the operating layer is InxGa1-xAsySb1-y (0 ≦ x ≦ 1, 0 ≦ y ≦ 1). Is silicon or tin, and in the closed loop circuit The four magnetoresistive elements connected from the first input terminal to the first input terminal through the second output terminal along the one direction are sequentially arranged in the first, second, When the third and fourth magnetoresistive elements are used, the first magnetoresistive element and the second magnetoresistive element that are adjacently connected in the closed loop circuit are adjacently connected in the closed loop circuit. In addition, the third magnetoresistive element and the fourth magnetoresistive element have magnetoresistive effects having different magnetoresistance change rates with respect to changes in magnetic flux density due to an external magnetic field, and are opposed to each other in the closed loop circuit. The first magnetoresistive element and the third magnetoresistive element, and the second magnetoresistive element and the fourth magnetoresistive element that are oppositely connected in the closed loop circuit are respectively Magnetic flux density due to external magnetic field By magnetoresistance ratio comprises equal magnetoresistive each other with respect to reduction to form a four-terminal magneto-resistance element.

  Here, the first magnetoresistive element and the third magnetoresistive element that are oppositely connected in the closed loop circuit have a short-circuit electrode, and the second magnetoresistive that is oppositely connected in the closed loop circuit. The resistor element and the fourth magnetoresistive element may be configured without a short-circuit electrode.

  The resistance value of the first magnetoresistive element that is oppositely connected in the closed loop circuit and the resistance value of the third magnetoresistive element are equal to each other, and the second magnetoresistance element is oppositely connected in the closed loop circuit. The resistance value of the magnetoresistive element and the resistance value of the fourth magnetoresistive element may be equal to each other.

  The resistance value of the first magnetoresistive element and the resistance value of the second magnetoresistive element that are adjacently connected in the closed loop circuit, and the third magnetoresistance that is adjacently connected in the closed loop circuit The resistance value of the element and the resistance value of the fourth magnetoresistive element may be equal to each other.

  The present invention is a magnetic sensor for performing signal detection using the magnetoresistive effect of a magnetoresistive element, wherein the 4-terminal magnetoresistive element and a magnetic field applying means for applying an external magnetic field to the 4-terminal magnetoresistive element Here, all the four magnetoresistive elements constituting the four-terminal magnetoresistive element are mounted on the same surface of the magnetic field applying means and disposed in a constant magnetic field of the external magnetic field. In the configuration, based on the magnetoresistive effect of each of the magnetoresistive elements, by detecting output signals output from the first output terminal and the second output terminal constituting the four-terminal magnetoresistive element, A magnetic sensor may be configured.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  A first embodiment of the present invention will be described with reference to FIGS.

[3-terminal magnetoresistive element]
(Basic configuration)
First, a schematic configuration of the three-terminal magnetoresistive element according to the present invention will be described.
FIG. 1 shows a configuration example of a three-terminal magnetoresistive element 100.

  The three-terminal magnetoresistive element 100 includes two magnetoresistive elements 30 and 31, terminal electrodes 1 and 3 for applying a DC voltage Vin, and a terminal electrode 2 for outputting an output voltage Vout as an output signal. Consists of

  The magnetoresistive element 30 has a structure having a short-circuit electrode, and the magnetoresistive element 31 has a structure not having a short-circuit electrode.

  FIG. 2 shows a circuit configuration of the three-terminal magnetoresistive element 100. The magnetoresistive element 30 and the magnetoresistive element 31 are connected in series via the terminal electrode 2, and a constant voltage power source Vin (= 5 V) is connected between the terminal electrodes 1 and 3.

  The thus configured magnetoresistive elements 30 and 31 are transfer molded using an epoxy resin to form a three-terminal magnetoresistive element 100.

  FIG. 3 shows a mounting configuration of the molded three-terminal magnetoresistive element 100.

  Reference numeral 19 denotes an operation layer of the magnetoresistive elements 30 and 31. Reference numeral 20 denotes an electrode corresponding to the terminal electrode 1 of the terminal electrodes 1, 2 and 3. 21 is a mold resin. Reference numeral 22 denotes a terminal connected to each of the terminal electrodes 1, 2, and 3.

  The operation layer 19 of the magnetoresistive elements 30 and 31 preferably has as high an electron mobility as possible in order to obtain a high magnetoresistance change rate, and is made of Si, GaAs, InSb, InAs, or a mixed crystal system thereof. InAsSb and the like are preferable.

  The substrate of the magnetoresistive elements 30 and 31 may be any material as long as it exhibits a solid shape. For example, a semiconductor, a dielectric, a ceramic, or a glass substrate can be used. Further, when a substrate such as GaAs, Si, InP, or GaP is used among the semiconductor substrates, high electron mobility can be obtained particularly in the operation layer 19, which is particularly preferable.

  As a method of adding an impurity for increasing carriers into the operation layer 19, it may be performed simultaneously with the formation of the operation layer 19, or may be implanted using an ion implantation method after film formation. For example, in the case of a III-V group compound semiconductor such as InSb or InAs, an impurity to be used may be a group IV element such as Si or Sn or a group VI element typified by Se, Te, or S. Of these, Si and Sn are particularly preferable.

  Adding an impurity for increasing carriers to the operating layer 19 has an effect of improving the temperature characteristics of the manufactured magnetoresistive elements 30 and 31.

However, if too many impurities are added, there is a problem in that the electron mobility that affects the sensitivity of the magnetoresistive element is lowered. Therefore, the number of added carriers is from 4 × 10 ¹⁶ / cm ^3. It is preferably 1 × 10 ¹⁸ / cm ³ , more preferably 5 × 10 ¹⁶ / cm ³ to 5 × 10 ¹⁷ / cm ³ .

  As a method for forming the operation layer 19, a vacuum deposition method is generally used, but a molecular beam epitaxy (MBE) method is a particularly preferable method because it has high controllability of the film thickness and composition of the thin film. For this reason, there is almost no difference in the characteristics of a plurality of elements arranged in the magnetic pattern detection device of the present invention.

  The electrode material used for the electrode 20 is a Cu single layer, Ti / Au, Ni / Au, Cr / Cu, Cu / Ni / Au, Ti / Au / Ni, Cr / Au / Ni, Cr / Ni / Au / Ni. It is good also as such lamination | stacking. The electrode material may be any material as long as it can withstand the operating conditions and environmental conditions in which the manufactured element is used.

  The electrode 20 may be formed by a general vacuum vapor deposition method such as electron beam vapor deposition or resistance thermal vapor deposition, a sputtering method or a plating method. Further, in order to improve the ohmic contact with the electrode operation layer after forming the electrode, it is also preferable to perform heat treatment using a rapid temperature rising thermal annealing (RTA) method.

  As an example of the thin film forming method, details will be described in the case where a Sn-doped InSb thin film is formed as an operation layer using GaAs as a substrate using a molecular beam epitaxy method.

First, the surface oxygen is desorbed by heating at 650 ° C. while irradiating the GaAs substrate 23 with a thickness of 0.35 μm. Next, the temperature is lowered at 580 ° C. to form a GaAs buffer layer with a thickness of 200 nm. Next, the temperature was lowered to 400 ° C. while irradiating As, and then a Sn-doped InSb thin film 6 having a thickness of 1 μm of the operation layer 19 was formed while simultaneously irradiating the substrate with Sn, In, and Sb. At this time, the Sn cell temperature was adjusted so that the electron concentration of the InSb thin film 6 was 7 × 10 ¹⁶ / cm ³ .

(Production method)
Next, a method for manufacturing the three-terminal magnetoresistive element 100 will be described.

  4A to 4E show a manufacturing process of the three-terminal magnetoresistive element 100. FIG.

  The manufacturing process of the three-terminal magnetoresistive element 100 can use a normal photolithography technique.

  First, as shown in FIG. 4A, a photoresist is uniformly coated on the InSb surface of the InSb / GaAs substrate by a spin coater. The photoresist coating condition is 2.5 μm thickness when rotated for 20 seconds at a rotational speed of 3200 rpm with a viscosity of 100 cp.

  Next, as shown in FIG. 4B, after exposure and development using a photomask for mesa etching of InSb, an InSb thin film is formed into a desired shape 25 with a hydrochloric acid / hydrogen peroxide etching solution. Etch.

  Here, an example in which the operation layer 19 is etched using the wet etching method has been introduced, but mesa etching may be performed by dry milling using ion milling or reactive ion etching.

  Next, as shown in FIG. 4C, after applying the photoresist again, exposure and development for forming the short-circuit electrode 6 are performed, the electrode is deposited by the vacuum deposition method, and the short-circuit electrode is formed by the lift-off method. 6 is formed. After forming a resist pattern with a photoresist, a stacked electrode made of 50 nm thick Ti, 400 nm thick Au, and 50 nm thick Ni is formed as the short-circuit electrode 6 by the electron beam method, and desired using a lift-off method. The short-circuit electrode 6 having the shape is produced.

  Next, as shown in FIG. 4D, a silicon nitride thin film 26 having a thickness of 300 nm is formed as a protective film by plasma CVD, and a silicon nitride film only on the electrode pad portion is formed using a reactive ion etching apparatus. Removed.

  Finally, as shown in FIG. 4E, the electrode pad portion 27 was formed in the same manner as the method for forming the short-circuit electrode 6. As an electrode pad, a laminated electrode made of 50 nm thick Ti and 400 nm thick Au was used. In order to improve the contact with the operation layer 19, heat treatment was performed at 500 ° C. for 2 minutes in an inert gas atmosphere. The electrode pad portion 27 and the terminal electrodes 1, 2, and 3 in FIG. 1 are the same.

  Then, after being separated into element chips by dicing, the element chips were die-bonded on the lead frame, and the electrodes on the element chip and the lead frame were connected by Au wire wires. Thereafter, transfer molding was performed with an epoxy resin to complete a three-terminal magnetoresistive element.

  FIG. 5 shows the manufactured three-terminal magnetoresistive element 100.

  When the width (element width) 28 of the InSb thin film after mesa etching is W and the distance (element length) 29 between the short-circuit electrodes 6 is L, L / W is the shape factor.

(Magnetic properties)
Next, the magnetic characteristics of the magnetoresistive element 30 will be described.

FIG. 6 shows a magnetoresistive effect that is a magnetic characteristic of the magnetoresistive element 30. A uniform magnetic field was applied to the magnetoresistive element 30 with an electromagnet, and the relationship between the magnetoresistance change rate ΔR / R ₀ and the magnetic flux density was measured.

6, a _{ΔR = R B -R 0, R} B is the resistance in a magnetic field, _{R 0} is the resistance in those without a magnetic field.

  FIG. 7 shows a graph obtained by re-plotting the magnetoresistance change rate and the shape factor L / W at a magnetic flux density of 2000 (G). From this graph, it can be seen that the rate of change in magnetoresistance sharply decreases when the shape factor L / W is about 0.3. From this result, the shape factor L / W of the magnetoresistive element 30 was set to 0.2, and the shape factor L / W of the magnetoresistive element 31 was set to 25.

  FIG. 8 shows a configuration for measuring the magnetic characteristics of the three-terminal magnetoresistive element 100.

  The three-terminal magnetoresistive element 100 was placed in the uniform magnetic field of the electromagnet 33 with the rare earth magnet 15 (8 mm × 6 mm × 4.5 mm) attached to the N pole side. The rare earth magnet 15 has a surface magnetic flux density of about 2.5 kG. The magnetic field of the electromagnet 33 was changed, and the voltage (Vout) of the terminal electrode 2 (that is, the output terminal 2) was measured. As for the direction of the magnetic field of the electromagnet 33, the arrow in the figure is the positive direction.

  FIG. 9 shows the relationship between the magnetic flux density and the output voltage Vout as a measurement result of the magnetic characteristics of the three-terminal magnetoresistive element 100.

  The vertical axis represents a value obtained by subtracting Vin / 2 from the voltage (Vout) of the output terminal 2 (hereinafter abbreviated as a signal output voltage), that is, a Vout−Vin / 2 value. The horizontal axis represents the magnetic flux density of the magnetic field applied by the electromagnet 33.

  The positive direction of the magnetic field of the electromagnet 33 is a direction that cancels out the lines of magnetic force from the rare earth magnet N-pole, and the resistance value of the magnetoresistive element 30 decreases from the magnetic characteristics of FIGS. Since the magnetoresistive element 31 has almost no sensitivity to changes in magnetic flux, the resistance value hardly changes from the magnetic characteristics shown in FIGS. As a result, the potential of the output terminal 2 of the circuit shown in FIG.

  On the other hand, the negative direction with respect to the magnetic field of the electromagnet 33 is the direction in which the magnetic field lines from the N pole of the rare earth magnet 15 increase, and the resistance value of the magnetoresistive element 30 increases. As a result, the potential of the output terminal 2 decreases. It can be seen that the output voltage Vout of the output signal is linear with respect to the applied magnetic field of the electromagnet 33 and a uniform magnetic field can be detected.

  Furthermore, by making the resistance values of the magnetoresistive element 30 and the magnetoresistive element 31 equal, it was possible to satisfy Vout = Vin / 2 when the magnetic flux density was zero.

(Temperature dependence)
Next, the temperature dependence of the three-terminal magnetoresistive element 100 will be described.

  FIG. 10 shows the measurement result of the temperature dependence of the output voltage Vout of the output signal when the magnetic flux density is zero (the state where the three-terminal magnetoresistive element 100 is not attached to the rare earth magnet 15). As a result of measuring the value of Vout−Vin / 2 as the output voltage of the output signal in the temperature range of −60 ° C. to + 160 ° C., it is found that the value becomes zero and there is almost no temperature drift.

(Magnetic sensor)
Next, an example in which a magnetic sensor including the three-terminal magnetoresistive element 100 is configured and a magnetic pattern is detected will be described as an application example.

  11 and 12 show an MR head 36 as a magnetic sensor including a three-terminal magnetoresistive element 100 for obtaining a signal proportional to a change in magnetic flux due to an actual magnetic pattern (hereinafter referred to as an absolute magnetic flux change amount detection). The schematic structure of is shown.

  FIG. 11 shows a configuration example of the MR head 36 on which the three-terminal magnetoresistive element 100 is mounted.

  The MR head 36 is manufactured as the MR head 36 by inserting the rare earth magnet 15 having the three-terminal magnetoresistive element 100 attached to the N pole side surface into the CAN 34 and potting with the epoxy resin 35. In actual detection of the magnetic pattern, the one sealed with CAN 34 is used.

  Then, as shown in FIG. 12, the MR head 36 is fixed to the printed circuit board 37, and as shown in FIG. 2, it is connected to the constant voltage power source Vin between the terminal electrodes 1 and 3 of the half bridge circuit. The printed circuit board 37 has a DC amplifier circuit (inverted amplifier circuit) as shown in FIG. 13 for amplifying the output signal (output voltage Vout) output from the output terminal 2 of the three-terminal magnetoresistive element 100 of the MR head 36. ) 150 is formed.

  The magnetic print 38 is scanned in the direction of the arrow shown in FIG. 12 and passes below the three-terminal magnetoresistive element 100 that constitutes the MR head 36.

  FIG. 13 shows a configuration example of the DC amplifier circuit 150.

  The DC amplifier circuit 150 is configured by amplifier circuits 151 and 152 connected in two stages, and its input terminal is connected to the output terminal 2 of the three-terminal magnetoresistive element 100 constituting the MR head 36. The output signal 41 (Vp) is output from the output terminal 40 of the second stage amplifier circuit 152. The output signal 41 is amplified by direct current amplification, so that the gain is about 10,000 times.

  FIG. 14 shows a configuration example of a magnetic pattern used for magnetic detection.

  As the magnetic ink 39 constituting the magnetic pattern, four types (A, B, C, D) having different magnetic powder contents are prepared. One of the magnetic inks 39 has a width of 0.8 mm and a length of 8.0 mm. Four magnetic inks 39 are arranged in the order of A, B, C, and D at intervals of 4.5 mm and printed on the magnetic printed matter 38 to form a magnetic pattern.

  The contents of the magnetic powder contained in the four types of magnetic inks A, B, C, and D are A = 50%, B = 40%, C = 20%, and D = 10%.

  Then, in a state where the magnetic print 38 on which such a magnetic pattern is formed is substantially in contact with the MR head 36 provided with the three-terminal magnetoresistive element 100, scanning is performed in the direction of the arrow in FIG. .

  FIG. 15 shows a signal waveform corresponding to the magnetic pattern detected by the MR head 36. It can be seen that signals are detected in proportion to the amount of magnetic powder contained in the magnetic patterns A, B, C, and D. Therefore, it can be seen that the difference in the magnetic pattern, that is, the content of the magnetic powder in the magnetic printed matter 38 can be detected accurately and faithfully.

  FIG. 16 shows the signal detection principle of the magnetic pattern.

  Here, the principle of detecting a magnetic pattern signal made of magnetic ink 39 containing magnetic powder formed on a magnetic print 38 using the MR head 36 of FIG. 11 will be described.

  In FIG. 16, when the magnetic printed matter 38 is scanned, it moves from left to right as indicated by positions A → B → C. The arrows in the figure represent the lines of magnetic force applied from the magnet 15.

  In FIG. 16A, the distance from the three-terminal magnetoresistive element 100 to the magnetic powder contained in the magnetic ink is farther than the range exerted by the magnetic lines of force of the magnet 15, so that the magnetic flux density immediately below the three-terminal magnetoresistive element 100 is Is not affected by the magnetic ink 38.

  In FIG. 16B, since the magnetic permeability of the magnetic powder is considerably larger than that of air, the magnetic lines of force of the magnet 15 are drawn into the magnetic powder, so that the three-terminal magnetic resistance is generated by the magnetic interaction between the magnetic lines of force and the magnetic powder. The magnetic flux density immediately below the element 100 increases, and the resistance value of one magnetoresistive element 30 increases. If the magnetic powder has the same magnetic permeability, the magnetic flux density changes in proportion to the content of the magnetic powder contained in the magnetic pattern.

  In FIG. 16C, similarly to FIG. 16A, the magnetic flux density immediately below the three-terminal magnetoresistive element 100 is not affected by the magnetic ink 38.

  FIG. 17 shows the detection principle of the output signal 41 (signal output voltage Vp) appearing at the output terminal 40 of FIG.

  At position A in FIG. 17, since the resistance values of the magnetoresistive element 30 and the magnetoresistive element 31 constituting the three-terminal magnetoresistive element 100 are equal, the output voltage 2 is Vin / 2. Note that the position A corresponds to the position A in FIG.

  At position B in FIG. 17, since the resistance value of the magnetoresistive element 30 increases, the output voltage 2 becomes lower than Vin / 2. Note that the position B corresponds to the position B in FIG.

  At position C in FIG. 17, since the resistance values of the magnetoresistive element 30 and the magnetoresistive element 31 are equal, the output voltage 2 is Vin / 2. Note that the position C corresponds to the position C in FIG.

  By scanning the magnetic print 38 in this way, an output signal as shown in FIG. 17 is obtained. In the output signal 41, the magnetic flux density immediately below the three-terminal magnetoresistive element 100 is changed by the magnetic interaction generated when the magnetic field of the magnetic ink 38 constituting the magnetic pattern approaches a constant magnetic field from the magnet 15, It is measured in proportion to the changed magnetic flux density. As described above, since the three-terminal magnetoresistive element 100 can obtain the signal output voltage Vp proportional to the change in the magnetic flux density, the output signal 41 is the degree of shading of the magnetic powder contained in the magnetic pattern printed on the banknote or the like. It is detected as a highly accurate signal that is proportional to

  The three-terminal magnetoresistive element 100 is not limited to the magnetic pattern detection process as described above, and can be applied to other detection processes such as the above-described rotation detection of the gear.

Next, a second embodiment of the present invention will be described with reference to FIGS.
[4-terminal magnetoresistive element]
In this example, a four-terminal magnetoresistive element is manufactured.

  FIG. 18 shows the configuration of the four-terminal magnetoresistive element 200.

  The four-terminal magnetoresistive element 200 applies two magnetoresistive elements 42 and 44 having the same magnetic characteristics, two magnetoresistive elements 43 and 45 having the same magnetic characteristics, and a DC voltage Vin. It consists of terminal electrodes 7 and 9 and terminal electrodes 8 and 10 for outputting an output voltage Vout as an output signal.

  The magnetoresistive elements 42 and 44 have a structure having a short-circuit electrode, and the shape factor L / W = 0.2 in FIG. 7 is set. The magnetoresistive elements 43 and 45 have a structure having no short-circuit electrode, and the shape factor L / W = 25 in FIG. 7 is set. The resistance values of the magnetoresistive elements 42, 43, 44, 45 are all made equal.

  The four-terminal magnetoresistive element 200 was transfer molded with epoxy resin to complete the magnetoresistive element 46.

  FIG. 19 shows a circuit configuration of the four-terminal magnetoresistive element 200. The magnetoresistive elements 42, 43, 44, 45 are connected in a loop, and the terminal electrodes 7, 9 are connected to a constant voltage power source Vin (= 5V).

  FIG. 20 shows an example of measuring the magnetic characteristics of the four-terminal magnetoresistive element 200.

  In order to measure the magnetic characteristics of the four-terminal magnetoresistive element 200, it was placed in the uniform magnetic field of the electromagnet 33 in a state of being attached to the N pole side of the rare earth magnet 15. The surface magnetic flux density of the rare earth magnet 15 was about 2.5 kG. The magnetic field of the electromagnet 33 was changed, and the voltage (Vout) between the terminal electrode 8 (output terminal 8) (−) and the terminal electrode 10 (output terminal 10) (+) was measured. As for the direction of the magnetic field of the electromagnet 33, the arrow in the figure is the positive direction.

  FIG. 21 shows the relationship between the magnetic flux density and the output voltage Vout as a measurement result of the magnetic characteristics of the four-terminal magnetoresistive element 200.

  The vertical axis represents the voltage (Vout) between the output terminal 8 (−) and the output terminal 10 (+), and the horizontal axis represents the magnetic flux density of the magnetic field applied by the electromagnet 33. The positive direction of the magnetic field of the electromagnet 33 is a direction that promotes the magnetic field lines from the north pole of the rare earth magnet 15, and the resistance values of the magnetoresistive elements 42 and 43 increase. Since the magnetoresistive elements 43 and 45 are hardly sensitive to changes in magnetic flux, their resistance values hardly change. As a result, the potential of the output terminal 8 (−) decreases and the potential of the output terminal 10 (+) increases. When the voltage (Vout) between the output terminal 8 (−) and the output terminal 10 (+) is taken as the output voltage, the output voltage is linear with respect to the applied magnetic field of the electromagnet 33 and has a uniform magnetic field. It can be detected. Note that the output voltage of the four-terminal magnetoresistive element 200 can be doubled as compared with the signal output voltage of the three-terminal magnetoresistive element 100 of the first example described above.

  As shown in FIG. 8 described above, when the direction of the magnetic field of the rare earth magnet 15 and the direction of the magnetic field of the electromagnet 33 are reversed, the voltage (Vout) between the output terminal 8 (−) and the output terminal 10 (+) is increased. It has a negative inclination with respect to the direction of the magnetic field of the electromagnet 33.

  Further, since the resistance values of the magnetoresistive elements 42, 43, 44 and 45 are all equal, Vout = 0 can be obtained when the magnetic flux density is zero.

  In this example, the resistance values of the magnetoresistive elements 42, 43, 44, 45 are all made equal, but the resistance value of the magnetoresistive element 42 and the resistance value of the magnetoresistive element 43 are made equal, Even when the resistance value of the magnetoresistive element 45 is made equal, and the resistance value of the magnetoresistive element 42 and the resistance value of the magnetoresistive element 44 are different, Vout = 0 can be set when the magnetic flux density is zero, In addition, magnetic characteristics as shown in FIG. 21 can be obtained.

  Further, the temperature characteristics of the output voltage of the four-terminal magnetoresistive element 200 were also measured in the same manner as in the first example described above, but there was almost no temperature drift of the output voltage.

(Modification)
As a modification of the four-terminal magnetoresistive element 250, a structure as shown in FIG. The magnetoresistive elements 42 and 44 having the same magnetic characteristics and the magnetoresistive elements 43 and 45 having the same magnetic characteristics are arranged close to each other in the same direction. Thereby, simplification of a manufacturing process, improvement of electrical characteristics, and the like can be achieved. Further, even in such a structure, the magnetic characteristics and the temperature dependence were measured, but were the same as the characteristics of the four-terminal magnetoresistive element 200 in FIG.

  The present invention relates to a magnetoresistive element and a magnetic sensor, and more particularly, to a magnetoresistive element having high sensitivity and excellent temperature stability for detecting magnetic patterns such as banknotes and detecting rotation of gears. As a result, even when all the magnetoresistive elements are arranged in a constant magnetic field, it is possible to accurately measure a weak change in magnetic field strength and to construct a structure having excellent temperature characteristics. It becomes.

It is a top view which shows the structure of the 3 terminal magnetoresistive element which is the 1st Embodiment of this invention. It is a circuit diagram which shows the connection form of the half bridge circuit which comprises a 3 terminal magnetoresistive element. It is a block diagram which shows the external appearance structure of the molded 3 terminal magnetoresistive element. It is process drawing explaining the manufacturing process of the magnetoresistive element applied to this invention. It is a top view for demonstrating the shape factor (L / W) of a magnetoresistive element. It is a graph which shows the relationship of the magnetic flux density-magnetoresistance change rate of a magnetoresistive element. It is a graph which shows the relationship of the magnetoresistive change rate-form factor of a magnetoresistive element. It is explanatory drawing which shows the structure which measures the magnetic characteristic of a 3 terminal magnetoresistive element. It is a graph which shows the relationship between the magnetic flux density of a 3 terminal magnetoresistive element-the detection voltage of an output signal. It is a graph which shows the relationship between the temperature-output signal voltage of a 3 terminal magnetoresistive element. It is explanatory drawing which shows the structure of MR head using a 3 terminal magnetoresistive element as a magnetic sensor. It is explanatory drawing which shows the detection method of a magnetic pattern. It is a circuit diagram which shows the direct current amplifier connected to MR head. It is explanatory drawing which shows the shape of the magnetic pattern used for a measurement. It is a wave form diagram which shows the detection signal of a magnetic pattern. It is explanatory drawing which shows the principle of the spatial difference detection method which is the conventional magnetic pattern detection method. It is a wave form diagram which shows the output signal detected by the conventional space difference detection method. It is a top view which shows the structure of the 4 terminal magnetoresistive element which is the 2nd Embodiment of this invention. It is a circuit diagram which shows the connection form of the full bridge circuit which comprises a 4-terminal magnetoresistive element. It is explanatory drawing which shows the structure which measures the magnetic characteristic of a 4-terminal magnetoresistive element. It is a graph which shows the magnetic flux density-detection voltage relationship of a 4-terminal magnetoresistive element. It is a top view which shows the modification of 4 terminal magnetoresistive element. It is a block diagram which shows the conventional 3 terminal magnetoresistive element. It is a circuit diagram of a 3 terminal magnetoresistive element. It is explanatory drawing which shows the principle of the spatial difference detection method which is the conventional magnetic pattern detection method. It is a wave form diagram which shows the output signal detected by the conventional space difference detection method. It is explanatory drawing which shows the principle of the rotation detection method of the gearwheel using a 3 terminal magnetoresistive element. It is a wave form diagram which shows the output signal detected by the rotation detection method of the gearwheel using a 3 terminal magnetoresistive element. It is explanatory drawing which shows the arrangement | positioning relationship between two magnetoresistive elements and the crests and valleys of a gear. It is a block diagram which shows the conventional 4 terminal magnetoresistive element. It is a circuit diagram of a 4-terminal magnetoresistive element. It is explanatory drawing which shows the principle of the rotation detection method of the gearwheel using a 4 terminal magnetoresistive element. It is a wave form diagram which shows the output signal detected by the output terminal (-) in the rotation detection method of the gearwheel using a 4 terminal magnetoresistive element. It is a wave form diagram which shows the waveform of the output signal detected by the output terminal (+) by the rotation detection method of the gearwheel using a 4 terminal magnetoresistive element. It is a wave form diagram which shows the difference signal of the output signal detected by the output terminal (-) and the output terminal (+) in the rotation detection method of the gearwheel using a 4 terminal magnetoresistive element.

Explanation of symbols

1 Terminal electrode (input terminal)
2 Terminal electrode (output terminal)
3 Terminal electrode (input terminal)
4 Magnetoresistive element 5 Magnetoresistive element 6 Short-circuit electrode 7 Terminal electrode (input terminal)
8 Terminal electrode (Output terminal)
9 Terminal electrode (input terminal)
10 Terminal electrode (output terminal)
11 magnetoresistive element 12 magnetoresistive element 13 magnetoresistive element 14 magnetoresistive element 15 rare earth magnet 16 magnetic print 17 magnetic ink 18 gear 19 operation layer 20 terminal electrode 21 mold resin 22 terminal 23 GaAs substrate 24 InSb thin film 25 mesa-etched InSb thin film 26 Silicon nitride thin film 27 Electrode pad portion 28 Element width 29 Element length 30 Magnetoresistive element 31 Magnetoresistive element 32 having no short-circuit electrode Three-terminal magnetoresistive element 33 Electromagnet 34 CAN
35 Epoxy resin 36 MR head 37 Printed circuit board 38 Magnetic printed matter 39 Magnetic ink 40 Output terminal 41 after DC amplification Detection signal 42 Magnetoresistive element 43 Magnetoresistive element 44 without short-circuited electrode Magnetoresistive element 45 Magnetoresistance without short-circuiting electrode Element 46 Four-terminal magnetoresistive element 100 Three-terminal magnetoresistive element 150 DC amplifier circuit 151,152 Amplifier circuit 200,250 Four-terminal magnetoresistive element

Claims (9)

By connecting two magnetoresistive elements in series, a three-terminal magnetoresistive element having three terminals, that is, first and second input terminals for applying an external voltage and one output terminal for extracting an output signal Because
Each of the magnetoresistive elements is a thin film magnetoresistive element in which a thin film layer obtained by growing a semiconductor crystal on a substrate is used as an operating layer of the magnetosensitive portion. In order to increase carriers in the operating layer of the semiconductor thin film magnetoresistive element The semiconductor thin film to which the impurities of
The composition of the operating layer is InxGa1-xAsySb1-y (0 ≦ x ≦ 1, 0 ≦ y ≦ 1), and the impurity is silicon or tin.
The magnetoresistive element connected between the first input terminal and the output terminal and the magnetoresistive element connected between the output terminal and the second input terminal are caused by an external magnetic field. A three-terminal magnetoresistive element comprising magnetoresistive effects having different magnetoresistance change rates with respect to changes in magnetic flux density. The magnetoresistive element connected between the first input terminal and the output terminal has a short-circuit electrode;
The three-terminal magnetoresistive element according to claim 1, wherein the magnetoresistive element connected between the output terminal and the second input terminal does not have a short-circuit electrode.   A resistance value of the magnetoresistive element connected between the first input terminal and the output terminal, and a resistance value of the magnetoresistive element connected between the output terminal and the second input terminal. The three-terminal magnetoresistive element according to claim 1 or 2, characterized by being equal to each other. A magnetic sensor that performs signal detection using the magnetoresistive effect of a magnetoresistive element,
A three-terminal magnetoresistive element according to any one of claims 1 to 3,
Magnetic field applying means for applying an external magnetic field to the three-terminal magnetoresistive element,
Here, in the configuration in which all two magnetoresistive elements constituting the three-terminal magnetoresistive element are mounted on the same surface of the magnetic field applying means and are disposed in a constant magnetic field of the external magnetic field, A magnetic sensor for detecting an output signal output from an output terminal constituting the three-terminal magnetoresistive element based on different magnetoresistive effects of the magnetoresistive elements. By connecting four magnetoresistive elements in a closed loop circuit, the magnetoresistive element has four terminals, ie, first and second input terminals for applying an external voltage and two output terminals for taking out an output signal, A four-terminal magnetoresistive element comprising four terminals connected in this order in the closed loop circuit in the order of a first input terminal, a first output terminal, a second input terminal, and a second output terminal Because
The magnetoresistive element is a thin film magnetoresistive element in which a thin film layer obtained by growing a semiconductor crystal on a substrate is used as an operating layer of the magnetosensitive portion, and the operating layer of the semiconductor thin film magnetoresistive element is used for increasing carriers. The operating layer is a semiconductor thin film to which impurities are added,
The composition of the operating layer is InxGa1-xAsySb1-y (0 ≦ x ≦ 1, 0 ≦ y ≦ 1), and the impurity is silicon or tin,
The four magnetoresistive elements connected in order from the first input terminal in the closed loop circuit to the first input terminal through the second output terminal along the one direction are sequentially arranged. When the first, second, third, and fourth magnetoresistive elements are used,
The first magnetoresistive element and the second magnetoresistive element that are adjacently connected in the closed loop circuit, and the third magnetoresistive element and the fourth magnetoresistive element that are adjacently connected in the closed loop circuit The magnetoresistive element has a magnetoresistive effect in which the magnetoresistance change rate with respect to the change in magnetic flux density due to the external magnetic field is different from each other, and
The first magnetoresistive element and the third magnetoresistive element that are oppositely connected in the closed loop circuit, and the second magnetoresistive element that is oppositely connected in the closed loop circuit, and the fourth magnetoresistive element. A magnetoresistive element is a four-terminal magnetoresistive element characterized in that each magnetoresistive effect has the same magnetoresistance change rate with respect to a change in magnetic flux density due to an external magnetic field. The first magnetoresistive element and the third magnetoresistive element oppositely connected in the closed loop circuit have a short-circuit electrode,
6. The four-terminal magnetoresistive element according to claim 5, wherein the second magnetoresistive element and the fourth magnetoresistive element that are oppositely connected in the closed loop circuit do not have a short-circuit electrode. The resistance value of the first magnetoresistive element that is oppositely connected in the closed loop circuit is equal to the resistance value of the third magnetoresistive element,
The 4-terminal according to claim 5 or 6, wherein a resistance value of the second magnetoresistive element and the fourth magnetoresistive element that are oppositely connected in the closed loop circuit are equal to each other. Magnetoresistive element.   The resistance value of the first magnetoresistive element and the resistance value of the second magnetoresistive element that are adjacently connected in the closed loop circuit, and the third magnetoresistance that is adjacently connected in the closed loop circuit 8. The four-terminal magnetoresistive element according to claim 5, wherein a resistance value of the element and a resistance value of the fourth magnetoresistive element are equal to each other. A magnetic sensor that performs signal detection using the magnetoresistive effect of a magnetoresistive element,
A four-terminal magnetoresistive element according to any one of claims 5 to 8,
Magnetic field applying means for applying an external magnetic field to the four-terminal magnetoresistive element,
Here, in a configuration in which all four magnetoresistive elements constituting the four-terminal magnetoresistive element are mounted on the same surface of the magnetic field applying means and disposed in a constant magnetic field of the external magnetic field, A magnetic sensor for detecting an output signal output from the first output terminal and the second output terminal constituting the four-terminal magnetoresistive element based on a magnetoresistive effect of each magnetoresistive element .

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