EP0654145A1 - Magnetic field sensor composed of a magnetic reversal conductor and one or several magnetoresistive resistances - Google Patents

Magnetic field sensor composed of a magnetic reversal conductor and one or several magnetoresistive resistances

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Publication number
EP0654145A1
EP0654145A1 EP94920425A EP94920425A EP0654145A1 EP 0654145 A1 EP0654145 A1 EP 0654145A1 EP 94920425 A EP94920425 A EP 94920425A EP 94920425 A EP94920425 A EP 94920425A EP 0654145 A1 EP0654145 A1 EP 0654145A1
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EP
European Patent Office
Prior art keywords
magnetic field
magnetoresistive
layer strips
field sensor
magnetic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP94920425A
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German (de)
French (fr)
Inventor
Fritz Dettmann
Uwe Loreit
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IMO Institut fur Mikrostrukturtechnologie und Optoelektronik eV
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IMO Institut fur Mikrostrukturtechnologie und Optoelektronik eV
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Publication of EP0654145A1 publication Critical patent/EP0654145A1/en
Withdrawn legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
    • G01R33/09—Magnetoresistive devices
    • G01R33/096—Magnetoresistive devices anisotropic magnetoresistance sensors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
    • G01R33/09—Magnetoresistive devices

Definitions

  • Magnetic field sensor made up of a magnetic reversal line and one or more magnetoresistive resistors
  • a method for eliminating zero drift in magnetoresistive sensor bridges is described in Technical Information 901 228 from Philips Components.
  • the magnetoresistive sensor bridge is placed in a wound coil.
  • Short current pulses in alternating directions through the spu generate enough magnetic field to set the self-magnetization of the magnetoresistive layer strips in the corresponding direction. Since the sensor sign changes its polarity when the direction of magnetization is reversed, the separation of the alternating component proportional to the magnetic field from the direct component means that the zero voltage of the sensor bridge also contains its drift.
  • the manufacture of such coils is expensive. Their inductance limits the measuring frequency.
  • the adjustment of the sensor elements in the coil is a complex operation, especially if all three magnetic field components are to be measured in a rough arrangement.
  • the object of the invention is to provide a magnetic field sensor with a minimal zero point drift, d can be produced inexpensively entirely in thin-film technology and in which restrictions i of the measurement frequency are not caused by the sensor element.
  • the object is achieved by the thin-film arrangements described in the claims.
  • a single magnetic field-dependent resistor which consists of one or more magnetoresistive layer strips, on a highly conductive thin-layer conductor strip perpendicular to its longitudinal direction.
  • the highly conductive thin-film conductor strip i, however, has a meandering structure. So that despite the alternating magnetic field direction alternating across the meandering stripes, a current arises which flows in the same direction in all sub-areas under the influence of a field to be measured.
  • meandering the hodüeitßhige Thin-layer conductor strip advantageously results in that only a small current is required for reversing the direction of magnetization.
  • the magnetic stray field outside the sensor chip is very small, since the magnetic fields of the meandering strips lying next to one another largely remain due to their opposite direction.
  • the magnetic field sensors can thus be operated in close proximity to one another.
  • the magnetic reversal conductor also has a very low inductance, so that the measuring frequency is no longer limited by it.
  • the magnetic field sensor When the magnetic field sensor is operated with a magnetoresistive resistor, a constant current is fed into this. The voltage at the magnetoresistive resistor is measured as the output signal. After a current pulse in a specific direction through the highly conductive thin-film conductor strip, the self-magnetization in the areas of the magnetoresistive resistance is defined in a certain way. In this state, the magnetic field to be measured causes an increase in the resistance value of the magnetoresistive resistor. The output voltage is therefore greater than i case free of magnetic fields. If a current pulse m in the opposite direction to the previous one is now fed into the highly conductive thin-film conductor strips, the directions d self-magnetizations are reversed.
  • the field to be measured thus reduces the resistance and the output voltage is smaller than in the case without a magnetic field.
  • an AC voltage is present at the output, the amplitude of which is proportional to the magnetic field to be measured. Any influences, such as the temperature, which lead to a slow dri of the resistance value of the magnetoresistive layer strip, have no influence on the AC output voltage. However, the decrease in the magnetoressitive effect with increasing temperature is noticeable in the output AC voltage ampute.
  • a further highly conductive layer strip is present under each magnetoresistive layer strip isolated in the same direction.
  • the current through this highly conductive layer strip is controlled by the sensor output voltage so that the applied z measuring magnetic field is just canceled by it.
  • the magnetoresistive magnetic field sensor acts as a zero detector.
  • the output variable of the arrangement is the size of the compensation current, which does not depend on the temperature of the arrangement. Likewise, non-linearities in the sensor characteristic no longer play a role, since the sensor is not controlled.
  • a single magnetoresistive resistor not only a single magnetoresistive resistor is used, but there are four parallel magnetoresistive resistors consisting of several areas above the thin-layer magnetizing conductor and the highly conductive compensation conductor, the areas of which alternate with Barber pole structures with alternating positive and negative angles
  • the longitudinal direction of the magnetoresistive layer strips are provided in such a way that they alternately begin with areas of positive and negative Barberpolst ⁇ ikturwinkel.
  • the vi resistors are connected to a Wheatstone bridge. If the magnetic reversal conductor is again operated in alternating pulses in the opposite direction, an AC voltage signal appears at the bridge output. Only a DC voltage signal is now superimposed on this, which results from d possibly unequal four resistance values of the bridge. However, this DC voltage component i is significantly lower than that when using a single resistor, which enables simple evaluation. Of course, the compensation of the magnetic field to be measured can also be used hi.
  • the bridge arrangement can consist of four resistors, all of which are formed from an even number of regions. Only the order of the angle of the barber pole structure changes from one resistance to another.
  • the magnetization direction is set in the areas by a first strong current pulse through the ummagnetization conductor.
  • the sensor bridge is thus sensitive to magnetic fields and can be used in the usual way without further magnetic reversal. Since all four resistors of the bridge consist of the same areas, the same changes can be expected in all resistors when the temperature of the sensor arrangement changes. This also applies to the proportion of change that arises from the variable layer tensions and, as a result, from magnetostriction.
  • the sensor bridge therefore has a reduced zero point drift compared to known sensor bridge arrangements and is therefore also suitable for measuring smaller fields in normal operation.
  • FIG. 1 shows a magnetoresistive resistor over a flat magnetic reversal conductor.
  • FIG. 2 shows how a flat compensation conductor is additionally arranged.
  • Figure 3 contains a complex arrangement with sensor bridge, magnetic reversal conductor and compensation conductor.
  • FIG. 1 shows a meandered, highly conductive, flat thin-film conductor 6, which is located on a layer support, into which a current IM can be fed when connected at both ends.
  • Areas 1 of magnetoresistive layer strips with their longitudinal direction perpendicular to the meander strips of the thin layer conductor 6 are insulated above this thin layer conductor 6.
  • Barber pole structures are located on the areas 1 of the magnetoresistive layer strips, which alternately form a negative angle 3 and a positive angle 4 with the longitudinal direction of the areas 1.
  • the areas 1 are all electrically connected in series by means of highly conductive, non-magnetic connections 2, so that a single resistor is present.
  • the series connection is electrical at the contact surfaces 5 connectable.
  • a constant current is fed in during operation of the magnetic field sensor.
  • the magnetization directions in the areas 1 are set as indicated by the corresponding arrows.
  • An external magnetic field H g to be measured causes an increase in the resistance value in all areas 1 compared to the field-free state in the magnetization directions shown.
  • a current pulse in the opposite direction through the magnetic reversal conductor 6 rotates the magnetizations of all areas 1 in the opposite direction.
  • the external magnetic field H g thus causes a decrease in resistance.
  • an alternating voltage can be tapped off the magnetoresistive resistor, the amplitude of which is proportional to the magnetic field strength of H. A certain minimum field strength is required to remagnetize the magnetoresistive areas.
  • the field strength that is generated by the re-magnetization current is inversely proportional to the width of the thin-film conductor.
  • the meandering significantly reduces the width and thus drastically reduces the current value required for magnetic reversal.
  • a high resistance value can easily be achieved. Since the change in resistance is proportional to the resistance value and this in turn is included as a proportionality factor in the AC output voltage, a high output voltage amplitude is also ensured.
  • the fact that the magnetoresistive resistance through the connections is also in the form of a meander has the advantage that the sensor element can be accommodated on a chip surface of small dimensions.
  • the arrangement shown in FIG. 2 differs from that in FIG. 1 only by an additional, highly conductive layer meander 7, which is arranged under the magnetoresistive regions 1.
  • the magnetic field of the current 1 ⁇ through this meander 7 is directed against the external magnetic field H g at the location of the areas 1.
  • a signal can be derived from the AC output voltage of the magnetoresistive resistor, which ensures that the current 1 ⁇ is set precisely to such a value that the external magnetic field at the location of the regions 1 is eliminated.
  • the compensation current Ij ⁇ set in this way now represents the sensor output signal.
  • the magnetoresistive resistor now only acts as a zero detector. Temperature dependencies and non-linearities in its characteristic are thus eliminated.
  • regions 1 of the magnetoresistive resistors are connected to one another by connecting lines 2 and 10 in such a way that a bridge is created.
  • the contact surfaces 8 are provided for the bridge operating voltage, the contact surfaces 9 for the bridge output voltage.
  • a magnetic reversal conductor 6 and a compensation line 7 are also present here, as in FIG. 2. Compensation of the external magnetic field to be measured is of course also possible here if the alternating voltage signal of the bridge output is used to regulate the current 1 ⁇ .
  • each bridge resistor consists of an even number of regions 1. The only difference is the angle of the barber pole structures of the regions 1 located next to one another. Bridge resistors are therefore composed of completely identical components. Temperature changes, the resistances will also change by the same values.

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Magnetic Variables (AREA)
  • Hall/Mr Elements (AREA)

Abstract

A sensor based on the magnetoresistive effect contains a meander-shaped magnetic reversal conductor (6) integrated into the thin layer arrangement. The magnetoresistive layer strips are provided with areas (1) with alternatively positive and negative, inclined barber pole structures (3) adapted to the meandrous structure of the conductor. The current required to reverse the magnetisation of the areas (1) is particularly weak. By periodically reversing the magnetisation of the areas (1), a drift-free alternating voltage is obtained as output signal of the sensor. This freedom from drift is a precondition for using the magnetic field sensor to accurately measure weak magnetic fields.

Description

Magnetfeldsensor, aufgebaut aus einer Ummagnetisierungsleitung und einem oder mehrere magnetoresistiven Widerständen Magnetic field sensor, made up of a magnetic reversal line and one or more magnetoresistive resistors
Beschreibungdescription
Die Messung von Magnetfeldern geringer Stärke, wie beispielsweise des Erdmagnetfeldes, ist bekanntli mit Sensoren möglich, die den anisotropen magnetoresistiven Effekt nutzen. Trotz ausreichen Magnetfeldempfindlichkeit ergeben sich bei größeren Temperaturänderungen jedoch wegen der nic unerheblichen Nullpunktdrift der Sensoren größere Probleme.The measurement of magnetic fields of low strength, such as the earth's magnetic field, is known to be possible with sensors that use the anisotropic magnetoresistive effect. In spite of sufficient magnetic field sensitivity, larger problems arise due to the negligible zero point drift of the sensors.
Eine Methode zur Eliminierung der Nullpunktdrift bei magnetoresistiven Sensorbrücken wird in d Technischen Information 901 228 von Philips Components beschrieben. Die magnetoresistive Sensorbrüc wird in einer gewickelten Spule plaziert. Kurze Stromimpulse abwechselnder Richtung durch die Spu erzeugen genügend Magnetfeld, um die Eigenmagnetisiening der magnetoresistiven Schichtstreifen in d entsprechende Richtung einzustellen. Da mit der Umkehr der Magnetisienmgsrichtung das Sensorsign seine Polarität ändert, ist mit Trennung des magnetfeldproportionalen Wechselanteils vom Gleichanteil, d die Nullspannung der Sensorbrücke enthält auch deren Drift eliminiert. Die Herstellung solcher Spulen i jedoch aufwendig. Ihre Induktivität begrenzt die Meßfrequenz. Die Justierung der Sensorelemente in d Spule ist ein aufwendiger Arbeitsvorgang, insbesondere, wenn alle drei Magnetfeldkomponenten im Rau mit einer Anordnung gemessen werden sollen.A method for eliminating zero drift in magnetoresistive sensor bridges is described in Technical Information 901 228 from Philips Components. The magnetoresistive sensor bridge is placed in a wound coil. Short current pulses in alternating directions through the spu generate enough magnetic field to set the self-magnetization of the magnetoresistive layer strips in the corresponding direction. Since the sensor sign changes its polarity when the direction of magnetization is reversed, the separation of the alternating component proportional to the magnetic field from the direct component means that the zero voltage of the sensor bridge also contains its drift. However, the manufacture of such coils is expensive. Their inductance limits the measuring frequency. The adjustment of the sensor elements in the coil is a complex operation, especially if all three magnetic field components are to be measured in a rough arrangement.
Aufgabe der Erfindung ist es, einen Magnetfeldsensor mit minimaler Nullpunktdrift anzugeben, d vollständig in Dünnschichttechnik kostengünstig gefertigt werden kann und bei dem Einschränkungen i der Meßfrequenz durch das Sensorelement nicht verursacht werden.The object of the invention is to provide a magnetic field sensor with a minimal zero point drift, d can be produced inexpensively entirely in thin-film technology and in which restrictions i of the measurement frequency are not caused by the sensor element.
Die Aufgabe wird durch die in den Ansprüchen beschriebenen Dünnschichtanordnungen gelöst. I einfachsten Fall genügt es, einen einzigen magnetfeldabhängigen Widerstand, der aus einem oder mehrere magnetoresistiven Schichtstreifen besteht isoliert auf einem zu dessen Längsrichtung senkrechte hochleitfahigen Dünnschichtleiterstreifen anzuordnen. Der hochleitfahige Dünnschichtleiterstreifen i jedoch mäanderfbrmig strukturiert. Damit trotz der über den nebeneinanderüegenden Mäanderstreife abwechselnden Magnetfeldrichtung bei Stromdurchfluß ein Widerstand entsteht der sich in alle Teilbereichen unter dem Einfluß eines zu messenden Feldes gleichsinnig ändert wurden di magnetoresistiven Schichtstreifen in solche Bereiche zerlegt die Barberpolstrukturen mit entgegengesetz gerichtetem Neigungswinkel zur Streifenlängsrichtung haben. Durch die Mäandrierung des hodüeitßhige Dünnschichtleiterstreifens ergibt sich vorteilhafterweise, daß für die Umkehr der Magnetisierungsrichtu nur ein geringer Strom benötigt wird. Weiterhin ist das außerhalb des Sensorchips vorhandene magnetisc Streufeld sehr gering, da sich die Magnetfelder der nebeneinanderliegenden Mäanderstreifen wegen ihr entgegengesetzten Richtung weitgehend auflieben. Damit können die Magnetfeldsensoren in unmittelbar Nähe zueinander betrieben werden. Aus dem gleichen Grunde hat der Ummagnetisierungsleiter auch ei sehr geringe Induktivität, so daß Begrenzungen der Meßfrequenz durch diese nicht mehr auftreten.The object is achieved by the thin-film arrangements described in the claims. In the simplest case, it is sufficient to arrange a single magnetic field-dependent resistor, which consists of one or more magnetoresistive layer strips, on a highly conductive thin-layer conductor strip perpendicular to its longitudinal direction. The highly conductive thin-film conductor strip i, however, has a meandering structure. So that despite the alternating magnetic field direction alternating across the meandering stripes, a current arises which flows in the same direction in all sub-areas under the influence of a field to be measured. By meandering the hodüeitßhige Thin-layer conductor strip advantageously results in that only a small current is required for reversing the direction of magnetization. Furthermore, the magnetic stray field outside the sensor chip is very small, since the magnetic fields of the meandering strips lying next to one another largely remain due to their opposite direction. The magnetic field sensors can thus be operated in close proximity to one another. For the same reason, the magnetic reversal conductor also has a very low inductance, so that the measuring frequency is no longer limited by it.
Bei Betrieb des Magnetfeldsensors mit einem magnetoresistiven Widerstand wird in diesen e Konstantstrom eingespeist. Als Ausgangssignal wird die Spannung am magnetoresistiven Widersta gemessen. Nach einem Stromimpuls bestimmter Richtung durch den hochleitfahige Dünnschichtleiterstreifen ist die Eigenmagnetisierung in den Bereichen des magnetoresistiven Widerstand in bestimmter Weise festgelegt. Das zu messende Magnetfeld bewirkt in diesem Zustand eine Zunahme d Widerstandswertes des magnetoresistiven Widerstandes. Die Ausgangsspannung ist also größer als i magnetfeldfreien Fall. Wird jetzt in den hochleitfahigen Dünnschichtleiterstreifen ein Stromimpuls m entgegengesetzter Richtung zum vorhergehenden eingespeist, kehren sich die Richtungen d Eigenmagnetisierungen um. Damit bewirkt das zu messende Feld eine Widerstandsverringerung und di Ausgangsspannung ist kleiner als im magnetfeldfreien Fall. Mit ständig wechselnder Impulsrichtung ist als am Ausgang eine Wechselspannung vorhanden, deren Amplitude dem zu messenden Magnetfel proportional ist. Irgendwelche Einflüsse, wie beispielsweise die Temperatur, die zu einer langsamen Dri des Widerstandswertes des magnetoresistiven Schichtstreifens führen, haben keinen Einfluß auf di Ausgangswechselspannung. Allerdings macht sich die Abnahme des magnetoressitiven Effektes mi steigender Temperatur in der Ausgangswechselspannungsampütude bemerkbar.When the magnetic field sensor is operated with a magnetoresistive resistor, a constant current is fed into this. The voltage at the magnetoresistive resistor is measured as the output signal. After a current pulse in a specific direction through the highly conductive thin-film conductor strip, the self-magnetization in the areas of the magnetoresistive resistance is defined in a certain way. In this state, the magnetic field to be measured causes an increase in the resistance value of the magnetoresistive resistor. The output voltage is therefore greater than i case free of magnetic fields. If a current pulse m in the opposite direction to the previous one is now fed into the highly conductive thin-film conductor strips, the directions d self-magnetizations are reversed. The field to be measured thus reduces the resistance and the output voltage is smaller than in the case without a magnetic field. With a constantly changing pulse direction, an AC voltage is present at the output, the amplitude of which is proportional to the magnetic field to be measured. Any influences, such as the temperature, which lead to a slow dri of the resistance value of the magnetoresistive layer strip, have no influence on the AC output voltage. However, the decrease in the magnetoressitive effect with increasing temperature is noticeable in the output AC voltage ampute.
Deshalb ist in einer anderen Ausführung der Erfindung unter jedem magnetoresistiven Schichtstreife isoliert in gleicher Richtung ein weiterer hochleitfahiger Schichtstreifen vorhanden. Der Strom durch dies hochleitfahigen Schichtstreifen wird von der Sensorausgangsspannung so gesteuert daß das angelegte z messende Magnetfeld durch ihn gerade aufgehoben wird. Die dazu notwendige Schaltung ist jedoch nich Gegenstand dieser Erfindung. Der magnetoresistive Magnetfeldsensor wirkt in diesem Fall als Nulldetektor Ausgangsgröße der Anordnung ist die Größe des Kompensationsstromes, die von der Temperatur de Anordnung nicht abhängt. Ebenso spielen Nichtiinearitäten in der Sensorkennlinie keine Rolle mehr, da de Sensor ja nicht ausgesteuert wird.In another embodiment of the invention, therefore, a further highly conductive layer strip is present under each magnetoresistive layer strip isolated in the same direction. The current through this highly conductive layer strip is controlled by the sensor output voltage so that the applied z measuring magnetic field is just canceled by it. However, the circuit necessary for this is not the subject of this invention. In this case, the magnetoresistive magnetic field sensor acts as a zero detector. The output variable of the arrangement is the size of the compensation current, which does not depend on the temperature of the arrangement. Likewise, non-linearities in the sensor characteristic no longer play a role, since the sensor is not controlled.
In einer weiteren Ausgestaltung der Erfindung wird nicht nur ein einziger magnetoresistiver Widerstan verwendet, sondern es sind über dem Dünnschichturnmagnetisierungsleiter und dem hochleitfahige Kompensationsleiter vier parallele aus mehrereren Bereichen bestehende magnetoresistive Widerständ vorhanden, deren Bereiche mit Barberpolstrukturen abwechselnden positiven und negativen Winkels zu Längsrichtung der magnetoresistiven Schichtstreifen versehen sind und zwar so, daß sie jewe abwechselnd mit Bereichen positiven und negativen Barberpolstπikturwinkels beginnen. Die vi Widerstände sind zu einer Wheatstone-Brücke verschaltet. Wird der Ummagnetisierungsleiter wieder Impulsen abwechselnd entgegengesetzter Richtung betrieben, so erscheint am Brückenausgang e Wechselspannungssignal. Diesem ist jetzt nur ein Gleichspannungssignal überlagert, das sich aus d möglicherweise ungleichen vier Widerstandswerten der Brücke ergibt Dieser Gleichspamiungsanteil i jedoch wesentlich geringer als der bei der Verwendung eines einzigen Widerstandes, was ein einfache Auswertung ermöglicht. Selbstverständlich ist die Kompensation des zu messenden Magnetfeldes auch hi anwendbar.In a further embodiment of the invention, not only a single magnetoresistive resistor is used, but there are four parallel magnetoresistive resistors consisting of several areas above the thin-layer magnetizing conductor and the highly conductive compensation conductor, the areas of which alternate with Barber pole structures with alternating positive and negative angles The longitudinal direction of the magnetoresistive layer strips are provided in such a way that they alternately begin with areas of positive and negative Barberpolstπikturwinkel. The vi resistors are connected to a Wheatstone bridge. If the magnetic reversal conductor is again operated in alternating pulses in the opposite direction, an AC voltage signal appears at the bridge output. Only a DC voltage signal is now superimposed on this, which results from d possibly unequal four resistance values of the bridge. However, this DC voltage component i is significantly lower than that when using a single resistor, which enables simple evaluation. Of course, the compensation of the magnetic field to be measured can also be used hi.
Die Brückenanordnung kann aus vier Widerständen bestehen, die alle aus einer geraden Zahl von Bereich gebildet sind. Nur die Reihenfolge des Winkels der Barberpolstruktur ändert sich von einem Widersta zum anderen. Durch einen ersten starken Stromimpuls durch den Ummmagnetisierungsleiter wird d Magnetisierungsrichtung in den Bereichen eingestellt. Damit ist die Sensorbrücke magnetfeldempfindlic und kann so in üblicher Weise ohne weitere Ummagnetisierung benutzt werden. Da alle vier Widerstän der Brücke aus gleichen Bereichen bestehen, ist bei veränderlicher Temperatur der Sensoranordnung in alle Widerständen mit gleichen Änderungen zu rechnen. Das gilt auch für den Anderunganteil, der über di veränderlichen Schichtspannungen und in deren Folge durch die Magnetostriktion entsteht. Di Sensorbrücke hat also eine reduzierte Nullpunktdrift gegenüber bekannten Sensorbrückenanordnungen un ist deshalb auch im üblichen Betrieb zur Messung kleinerer Felder geeignet. Ein konstanter Strom durch de Ummagnetisierungsleiter kann jetzt zur Erzeugung eines bestimmten Stabilisierungsmagnεtfeldes diene über das eine bestimmte Sensorempfindlichkeit eingestellt wird. Die erfindungsge äße Anordnung ist als bei Anwendung unterschiedlicher Auswerteverfahren für die Magnetfeldmessung vorteilhaft einsetzbar. Die Erfindung wird im folgenden an Ausfuhrungsbeispielen näher erläutert. In Figur 1 ist dazu ei magnetoresistiver Widerstand über einem ebenen Ummagnetisierungsleiter dargestellt. Figur 2 zeigt, wi zusätzlich dazu ein ebener Kompensationsleiter angeordnet ist. Figur 3 enthält eine komplexe Anordnun mit Sensorbrücke, Ummagnetisierungsleiter und Kompensationsleiter.The bridge arrangement can consist of four resistors, all of which are formed from an even number of regions. Only the order of the angle of the barber pole structure changes from one resistance to another. The magnetization direction is set in the areas by a first strong current pulse through the ummagnetization conductor. The sensor bridge is thus sensitive to magnetic fields and can be used in the usual way without further magnetic reversal. Since all four resistors of the bridge consist of the same areas, the same changes can be expected in all resistors when the temperature of the sensor arrangement changes. This also applies to the proportion of change that arises from the variable layer tensions and, as a result, from magnetostriction. The sensor bridge therefore has a reduced zero point drift compared to known sensor bridge arrangements and is therefore also suitable for measuring smaller fields in normal operation. A constant current through the magnetic reversal conductor can now be used to generate a specific stabilizing magnetic field via which a specific sensor sensitivity is set. The arrangement according to the invention can be used advantageously when using different evaluation methods for magnetic field measurement. The invention is explained in more detail below using exemplary embodiments. For this purpose, FIG. 1 shows a magnetoresistive resistor over a flat magnetic reversal conductor. FIG. 2 shows how a flat compensation conductor is additionally arranged. Figure 3 contains a complex arrangement with sensor bridge, magnetic reversal conductor and compensation conductor.
In Figur 1 ist ein mäandrierter hochleitfähiger ebener Dünnschichtleiter 6, der sich auf einem Schichtträge befindet dargestellt, in den bei Anschluß an beiden Enden ein Strom IM eingespeist werden kann. Übe diesem Dünnschichtleiter 6 sind isoliert Bereiche 1 von magnetoresistiven Schichtstreifen mit ihre Längsrichtung senkrecht zu den Mäanderstreifen des Dünnschichtleiters 6 angeordnet. Auf den Bereichen 1 der magnetoresistiven Schichtstreifen befinden sich Barberpolstrukturen, die abwechselnd einen negative Winkel 3 und einen positiven Winkel 4 mit der Längsrichtung der Bereiche 1 bilden. Die Bereiche 1 sin alle durch gut leitfähige, nicht magnetische Verbindungen 2 elektrisch in Reihe geschaltet so daß ei einziger Widerstand vorhanden ist. Die Reihenschaltung ist an den Kontaktflächen 5 elektrisc anschließbar. Im Betrieb des Magnetfeldsensors wird hier ein Konstantstrom eingespeist. Nach eine Stromimpuls durch den Ummagnetisierungsleiter 6 in der durch den Pfeil charakterisierten Richtung sin die Magnetisierungsrichtungen in den Bereichen 1 wie durch die entsprechenden Pfeile angezeig eingestellt. Ein zu messendes externes Magnetfeld Hg bewirkt bei den gezeichnete Magnetisierungsrichtungen eine Erhöhung des Widerstandswertes in allen Bereichen 1 gegenüber de feldfreien Zustand. Ein Stromimpuls entgegengesetzter Richtung durch den Ummagnetisierungsleiter 6 dreh die Magnetisierungen aller Bereiche 1 in die entgegengesetzte Richtung. Damit wird durch das extern Magnetfeld Hg eine Widerstandsabπahme bewirkt. Am magnetoresistiven Widerstand ist so bei periodische Ummagnetisierung eine Wechselspannung abgreifbar, deren Amplitude der Magnetfeldstärke von H proportional ist. Zur Ummagnetisierung der magnetoresistiven Bereiche ist eine bestimmt Mindestfeldstärke erforderlich. Die Feldstärke, die durch den Ummagnertisierungsstrom erzeugt wir, ist de Breite des Dünnschichtleiters umgekehrt proportional. Durch die Mäandrierung wird die Breite wesentlic herabgesetzt und damit der zum Ummagnetisieren nötige Stromwert drastisch verringert. Durch di Aufteilung des magnetoresistiven Widerstandsleiters in viele Bereiche 1 kann ohne weiteres ein hohe Widerstandswert realisiert werden. Da die Widerstandsänderung dem Widerstandswert proportional ist un diese wiederum als Proportionalitätsfaktor in die Ausgangswechselspannung eingeht, ist auch für eine hoh Ausgangsspannungsamplitude gesorgt. Daß der magnetoresistive Widerstand durch die Verbindungen ebenfalls in Form eines Mäanders ausgebildet ist hat den Vorteil, daß das Sensorelement auf Chipfläche geringer Abmessung untergebracht werden kann.FIG. 1 shows a meandered, highly conductive, flat thin-film conductor 6, which is located on a layer support, into which a current IM can be fed when connected at both ends. Areas 1 of magnetoresistive layer strips with their longitudinal direction perpendicular to the meander strips of the thin layer conductor 6 are insulated above this thin layer conductor 6. Barber pole structures are located on the areas 1 of the magnetoresistive layer strips, which alternately form a negative angle 3 and a positive angle 4 with the longitudinal direction of the areas 1. The areas 1 are all electrically connected in series by means of highly conductive, non-magnetic connections 2, so that a single resistor is present. The series connection is electrical at the contact surfaces 5 connectable. A constant current is fed in during operation of the magnetic field sensor. After a current pulse through the magnetic reversal conductor 6 in the direction characterized by the arrow, the magnetization directions in the areas 1 are set as indicated by the corresponding arrows. An external magnetic field H g to be measured causes an increase in the resistance value in all areas 1 compared to the field-free state in the magnetization directions shown. A current pulse in the opposite direction through the magnetic reversal conductor 6 rotates the magnetizations of all areas 1 in the opposite direction. The external magnetic field H g thus causes a decrease in resistance. With periodic magnetic reversal, an alternating voltage can be tapped off the magnetoresistive resistor, the amplitude of which is proportional to the magnetic field strength of H. A certain minimum field strength is required to remagnetize the magnetoresistive areas. The field strength that is generated by the re-magnetization current is inversely proportional to the width of the thin-film conductor. The meandering significantly reduces the width and thus drastically reduces the current value required for magnetic reversal. By dividing the magnetoresistive resistance conductor into many areas 1, a high resistance value can easily be achieved. Since the change in resistance is proportional to the resistance value and this in turn is included as a proportionality factor in the AC output voltage, a high output voltage amplitude is also ensured. The fact that the magnetoresistive resistance through the connections is also in the form of a meander has the advantage that the sensor element can be accommodated on a chip surface of small dimensions.
Die in Figur 2 gezeigte Anordnung unterscheidet sich von der in Figur 1 lediglich durch einen zusätzlichen gut leitenden Schichtmäander 7, der unter den magnetoresistiven Bereichen 1 angeordnet ist. Das Magnetfeld des Stromes 1^ durch diesen Mäander 7 ist dem externen Magnetfeld Hg am Ort der Bereiche 1 entgegengerichtet. Aus der Ausgangswechselspannung des magnetoresistiven Widerstandes läßt sich ein Signal ableiten, das dafür sorgt, daß der Strom 1^ genau auf einen solchen Wert eingestellt wird, daß das externe Magnetfeld am Ort der Bereiche 1 aufgehoben ist. Der so eingestellte Kompensationsstrom Ijς stellt nun das Sensorausgangssignal dar. Der magnetoresistive Widerstand wirkt hier nur noch als Nulldetektor. Temperaturabhängigkeiten und Nichtlinearitäten in seiner Kennlinie sind so eliminiert.The arrangement shown in FIG. 2 differs from that in FIG. 1 only by an additional, highly conductive layer meander 7, which is arranged under the magnetoresistive regions 1. The magnetic field of the current 1 ^ through this meander 7 is directed against the external magnetic field H g at the location of the areas 1. A signal can be derived from the AC output voltage of the magnetoresistive resistor, which ensures that the current 1 ^ is set precisely to such a value that the external magnetic field at the location of the regions 1 is eliminated. The compensation current Ij ς set in this way now represents the sensor output signal. The magnetoresistive resistor now only acts as a zero detector. Temperature dependencies and non-linearities in its characteristic are thus eliminated.
In Figur 3 sind die Bereiche 1 der magnetoresistiven Widerstände durch Verbindungsleitungen 2 und 10 so miteinander verbunden, daß eine Brückenschahung entsteht. Die Kontaktflächen 8 sind für die Brückenbetriebsspannung, die Kontaktflächen 9 für die Brückenausgangsspannung vorgesehen. Ein Ummagnetisierungsleiter 6 und eine Kompensationsleitung 7 sind wie in Figur 2 auch hier vorhanden. Kompensation des externen zu messenden Magnetfeldes ist hier selbstverständlich ebenso möglich, wenn zur Regelung des Stromes 1^ das Wechseispannungsignai des Brückenausgangs verwendet wird. In der Figur 3 besteht jeder Brückenwiderstand aus einer geraden Anzahl von Bereichen 1. Unterschiedli ist nur der Winkel der Barberpolstrukturen der jeweils nebeneinander befindlichen Bereiche 1. Brückenwiderstände sind also aus völlig gleichen Bestandteilen zusammengesetzt. Temperaturänderungen werden sich die Widerstände also auch um gleiche Werte ändern. Das trifft auch f die sich aus der über die Magnetostriktion erzeugte Widerstandsänderung durch Drehung d Magnetisierungsrichtung zu. Unterschiede in dieser Größe stellen bei bisher bekannten magnetoresistiv Brückenanordnungen den Hauptanteil der Nullpunktdrift der Brückenausgangsspannung dar. Deshalb h die hier vorgestellte Brücke auch bei Betrieb mit Gleichspannung eine stark reduzierte Nullpunktdri Damit ist auch das Betreiben des Brückensensors ohne ständige periodische Ummagnetisierung der Bereic 1 vorteilhaft möglich. Ein Gleichstrom durch den Ummagnetisierungsleiter 6 kann in diesem Fall z Erzeugung eines magnetischen Gleichfeldes am Ort der Bereiche 1 genutzt werden und so die einm eingestellte Magnetisierungsrichtung stabilisieren. In FIG. 3, regions 1 of the magnetoresistive resistors are connected to one another by connecting lines 2 and 10 in such a way that a bridge is created. The contact surfaces 8 are provided for the bridge operating voltage, the contact surfaces 9 for the bridge output voltage. A magnetic reversal conductor 6 and a compensation line 7 are also present here, as in FIG. 2. Compensation of the external magnetic field to be measured is of course also possible here if the alternating voltage signal of the bridge output is used to regulate the current 1 ^. In FIG. 3, each bridge resistor consists of an even number of regions 1. The only difference is the angle of the barber pole structures of the regions 1 located next to one another. Bridge resistors are therefore composed of completely identical components. Temperature changes, the resistances will also change by the same values. This also applies to the change in resistance generated by magnetostriction by rotating the magnetization direction. Differences in this size represent the main part of the zero point drift of the bridge output voltage in previously known magnetoresistive bridge arrangements. That is why the bridge presented here has a greatly reduced zero point dri even when operated with direct voltage. In this case, a direct current through the magnetic reversal conductor 6 can be used to generate a magnetic direct field at the location of the regions 1 and thus stabilize the magnetization direction set.

Claims

Patentansprüche Claims
1. Magnetfeldsensor, aufgebaut aus einer Ummagnetisierungsleitung und einem oder mehrereren magnetoresistiven Widerständen, die durch Schichtstreifen mit Barberpolstruktur gebildet sind , dadurch gekennzeichnet, daß ein oder mehrere parallel angeordnete magnetoresistive Schichtstreifen jeweils aus hintereinander geschalteten, magnetisch getrennten Bereichen (1) bestehen, die Barberpolstrukturen (3; 4) mit abwechselnd positivem (4) und negativem Winkel (3) zur Schichtstreifenlängsrichtung tragen und daß ein als Ummagnetisierungsleitung dienender hochleitfähiger Dünnschichtieiterstreifen (6), dessen Längsrichtung mit der Längsrichtung der magnetoresistiven Schichtstreifen einen Winkel bildet und von diesen isoliert ist, mäanderfbrmig darunter angeordnet ist.1. Magnetic field sensor, composed of a magnetic reversal line and one or more magnetoresistive resistors, which are formed by layer strips with barber pole structure, characterized in that one or more magnetoresistive layer strips arranged in parallel each consist of magnetically separated areas (1) connected in series, the barber pole structures ( 3; 4) with alternating positive (4) and negative angle (3) to the longitudinal direction of the layer strip and that a highly conductive thin-film conductor strip (6) serving as a magnetic reversal line, the longitudinal direction of which forms an angle with the longitudinal direction of the magnetoresistive layer strip and is insulated from it, meandering underneath is arranged.
2. Magnetfeldsensor nach Anspruch 1, dadurch gekennzeichnet, daß der Winkel zwischen den Längsrichtungen der magnetoresistiven Schichtstreifen und der hochleitfahigen Dünnschichtieiterstreifen 90° ist.2. Magnetic field sensor according to claim 1, characterized in that the angle between the longitudinal directions of the magnetoresistive layer strips and the highly conductive thin-film strip is 90 °.
3 Magnetfeldsensor nach Anspruch 1 und 2, dadurch gekennzeichnet, daß mehrere gleiche parallel angeordnete magnetoresistive3 magnetic field sensor according to claim 1 and 2, characterized in that several identical magnetoresistive arranged in parallel
Schichtstreifen mäanderfbrmig verbunden sind, und so alle einen einzigen Widerstand bilden.Layer strips are meandering connected, and so all form a single resistor.
4. Magnetfeldsensor nach Anspruch 1, dadurch gekennzeichnet, daß zur Kompensation des von außen auf den Sensor wirkenden Magnetfeldes unter den magnetoresistiven Schichtstreifen weitere hochleitfähige Schichtstreifen (7), deren Längsrichtung mit der der magnetoresistiven Schichtstreifen übereinstimmt, isoliert von den anderen Schichten vorhanden sind, und in der Fläche zwischen jeweils zwei magnetoresistiven Schichtstreifen ein Verbindungsleiter verläuft, so daß ein weiterer Mäander entsteht.4. A magnetic field sensor according to claim 1, characterized in that to compensate for the magnetic field acting on the sensor from the outside under the magnetoresistive layer strips, further highly conductive layer strips (7), the longitudinal direction of which coincides with that of the magnetoresistive layer strips, are present in isolation from the other layers, and A connecting conductor runs in the area between two magnetoresistive layer strips, so that a further meander is formed.
5. Magnetfeldsensor nach Anspruch 1 oder 4, dadurch gekennzeichnet, daß vier parallele, aus mehreren Bereichen (1) bestehende magnetoresistive Schichtstreifen vorhanden sind, die mit Bereichen (1) beginnen, die abwechselnd Barberpolstrukturen mit positivem (3) und negativem (4) Winkel tragen und die zu einer Wheatstonebrücke verschaltet sind.5. Magnetic field sensor according to claim 1 or 4, characterized in that there are four parallel magnetoresistive layer strips consisting of a plurality of regions (1) which begin with regions (1) which alternate Barber pole structures with positive (3) and negative (4) angles wear and which are connected to a Wheatstone bridge.
6. Magnetfeldsensor nach Anspruch S, dadu rch geken n ze i c hnet , daß jeder Brückenwiderstand aus mehreren magnetoresistiven Schichtstreifen besteht 6. Magnetic field sensor according to claim S, dadu rch geken n ze i c hnet that each bridge resistor consists of several magnetoresistive layer strips
EP94920425A 1993-06-09 1994-05-31 Magnetic field sensor composed of a magnetic reversal conductor and one or several magnetoresistive resistances Withdrawn EP0654145A1 (en)

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DE4319146 1993-06-09
DE4319146A DE4319146C2 (en) 1993-06-09 1993-06-09 Magnetic field sensor, made up of a magnetic reversal line and one or more magnetoresistive resistors
PCT/EP1994/001789 WO1994029740A1 (en) 1993-06-09 1994-05-31 Magnetic field sensor composed of a magnetic reversal conductor and one or several magnetoresistive resistances

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JP3465059B2 (en) 2003-11-10
WO1994029740A1 (en) 1994-12-22
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JPH08503778A (en) 1996-04-23
DE4319146A1 (en) 1994-12-15

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