GB2356059A

GB2356059A - Multilayer magnetoresistive sensor/bridge circuit arrangement

Info

Publication number: GB2356059A
Application number: GB0025192A
Authority: GB
Inventors: Gunther Haas; Martin Freitag; Andrew Johnson
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1999-10-15
Filing date: 2000-10-13
Publication date: 2001-05-09
Anticipated expiration: 2020-10-13
Also published as: FR2800915A1; GB0025192D0; GB2356059B; GB2356059A8; DE19949714A1

Abstract

A magnetically sensitive component (30), in particular a sensor element, with at least two magnetoresistive layer systems (20) produced in regions on a substrate (10), is proposed. Here each of the layer systems (20) has at least one reference layer (2, 2'), at least one intermediate layer (3) adjacent to the reference layer (2, 2') and at least one detection layer (1) adjacent to the intermediate layer (3), and are connected as bridge resistors (R<SB>2</SB>, R<SB>4</SB>) in an electrical circuit in the form of a Wheatstone bridge (21). Moreover, at least one of the reference layers (2, 2') has at least one magnetoresistive layer system (20), at least one first partial layer (2a, 2a') and at least one second partial layer (2b, 2b'), wherein the first partial layer (2a, 2a') exhibits a magnetisation (m<SB>2</SB>) and the second partial layer is an antiferromagnetic partial layer (2b, 2b'). The magnetically sensitive component (30) is especially suitable for contactless and largely temperature-independent and offset-free recording of speeds and angles based on the GMR or TMR effect. In this connection it can also be used in the presence of strong external magnetic fields.

Description

2356059 Magnetically sensitive component, in Rarticular a sensor element

with macTnetoresistive laver systems in a bridae 5 circuit The invention concerns a magnetically sensitive component, in particular a sensor element, with at least two magnetoresistive layer systems in a bridge circuit on a substrate according to the preamble of the main claim.

Prior art

Known magnetoresistive sensor elements which operate on the so-called "spin valve principle" usually consist of a soft magnetic detection layer with a first magnetisation m, aligned parallel to the detection layer and adjustable by an external magnetic field, a hard magnetic reference layer with a predetermined spatial alignment of an associated unvarying second magnetisation m, aligned parallel to the reference layer, as well as a non-magnetic metallic intermediate layer. With suitable dimensioning of the layer thicknesses and suitable choice of material, this system then exhibits a change in the electrical resistance when an electric cur'rent flows within the plane of the intermediate layer in accordance with R = RO + C cos E) where e denotes the angle between the directions of the two magnetisations associated with the reference layer and the detection layer (GMR or giant magneto resistor effect"). The resistance change is typically in the range between 5 % and 10 % and can be measured by varying the direction of the magnetisation ml, for example via an external magnetic 3S field.

Furthermore, the hard magnetic reference layer usually consists of either a thin layer of relatively hard magnetic material, or two layers one above the other in the form of a soft or relatively hard magnetic partial layer adjoining the intermediate layer, and an adjacent antiferromagnetic partial layer which determines or stabilises the spatial orientation of the magnetisation of the magnetic layer adjoining the intermediate layer.

The operation of such magnetoresistive sensor elements is based on the fact that the direction of the magnetisation mi of the detection layer is very easily orientated and for the most part parallel, to a component of an external magnetic field lying within the plane of the detection layer, whereas the direction of the magnetisation m2 of the reference layer should remain predominantly unaffected by such external fields, thus ensuring a reliable reference for the determination of the angle 0.

Regarding further details of magnetoresistive sensor elements and possible applications, reference should be made to C. Tsang et al., "Design, Fabrication and Testing of Spin-valve Read Heads for High Density Recording", IEEE Trans. Magn., 30, (1994), page 3801 ff, for example.

In order to use a magnetoresistive layer system in a sensor element, for example for contactless measurement of external magnetic fields, for use in motor vehicles as an APS wheel sensor, steering angle sensor or replacement potentiometer, etc., it is imperative that the sensor element delivers a temperature- independent output voltage and - to improve the measuring accuracy - one that has the smallest possible offset over the widest possible temperature range. To achieve this it is already known for a sensor element with two or four magnetoresistive layer systems to be connected in the form of a Wheatstone bridge circuit in order to eliminate the offset voltage of an individual magnetoresistive layer system, that, compared to the measuring signal, is relatively large and ternperaturedependent.

In detail, to achieve this a sensor element is produced from four magnetoresistive layer systems in the form of four individual resistors Ri to R4. which are usually constructed as meander-type printed conductors, patterned and connected up as a Wheatstone bridge via additional electrical printed conductors and contact pads in the known manner. Alternatively, it is also known for just two magnetoresistive layer systems to be used in the form of two half bridges with two further external conventional resistors and connected in the known manner as a'Wheatstone bridge.

In the first-named bridge circuit, for example, if the magnetisation directions of the magnetisation M2 of the reference layers in the resistors R, and R3 differ from those in the resistors R2 and R4 exactly by 1800, then this results in a temperature- independent, zero-offset bridge output voltage:

UB = 2UOCcos a To be able to manufacture such a sensor element in compact form on a substrate, for example a chip, it is furthermore known for the reference layer to be constructed in the form of three partial layers one above the other, whereby two thin cobalt layers, each of different thickness and opposite magnetisation, each having a resulting magnetic moment, are separated from each other by a copper layer with a thickness of a few A, and which are magnetically coupled to each other via the copper layer. A reference layer constructed in this manner is termed an "artificial anti f erromagnet 11 or "artificial antiferromagnetic" reference layer, since neither cobalt nor copper are antiferromagnetic.

With such known sensor elements, the reference S magnetisations m2 of the reference layers of the individual magnetoresistive layer systems can be produced only after the production of the magnetoresistive layer systems in a bridge circuit on a chip, whereby the magnetisations m2 of the individual reference layers of the magnetoresistive layer systems are only produced and defined locally by means of an external magnetic field.

In the sensor elements known from the prior art, this is possible because the "artificial anti f erromagnet ic reference layer can be influenced by the resulting magnetic moment of its two cobalt partial layers due to a usually particularly strong local external magnetic field applied during the manufacture of the sensor element, for example via magnetic write heads, and by and large this allows the direction of the magnetisation m2 of the reference layer to be adjusted. Local differently-aligned reference magnetisations m2 can thus be obtained in different magnetoresistive layer systems on the chip during production by means of a single injection via strong local external magnetic fields.

Such a sensor element is already offered by Infineon Technologies AG, 81609 Munich, under the designation GMR B6 and is described on the Internet along with further details of its construction and operation under http://www.infineon. com/products/38/38.htm Advantages of the invention Compared to the prior art, the magnetically sensitive component with magnetoresistive layer systems in a bridge circuit according to the invention has the advantage that a largely zero- offset and temperature -dependent output voltage can be obtained with it over a wide temperature range from -400C to 1500C, wherein the magnetically sensitive component, for example as a sensor element, is advantageously constructed in a very compact form on a substrate or chip, preferably in a monolithic, integrated form. This eliminates expensive subsequent construction and subsequent connection of the individual magnetoresistive layer systems or additional resistors, respectively.

Furthermore, the magnetically sensitive component according to the invention can be produced by a conventional process employed in mass production for the manufacture of layer systems and their microfabrication, that can be easily controlled.

Moreover, it is very advantageous that the magnetically sensitive component according to the invention, in particular when used as a sensor element, always remains unchanged even under the influence of strong external magnetic fields or magnetic interference fields, 'and that no irreversible impairments or a relevant drifting of the sensor characteristic over time or the GMR or TMR ("Tunnel Magneto Resistor") effect occurs in the individual layer systems, in particular due to a change in the direction of the magnetisation m2 of the reference layer and thus of the reference value for the angle e.

Here strong magnetic fields are understood to be in particular magnetic fields with H > 15 kA/m.

The magnetically sensitive component according to the invention thus exhibits high reliability, noise immunity and measurement accuracy, in particular with respect to the angular accuracy, as well as stability over time and 5 reproducibility of the measurement results.

Advantageous developments of the invention are revealed in the steps detailed in the sub-claims.

It is therefore especially advantageous that the measuring range of the sensor element according to the invention can encompass an angular range of 3600 when operated as an angular sensor.

it is furthermore advantageous if the reference layer has patterning, in particular a topography with a corrugated or sawtooth profile with uniaxial preferred direction, wherein the individual corrugations of this topography are advantageously aligned as near parallel as possible to the direction of the magnetisation of the reference layer. This form of patterning results in a particularly stable direction of the magnetisation of the reference layer that is insensitive to interference.

Incidentally, the layer system according to the invention can also be operated as a TMR ("Tunnel Magneto Resistor") sensor element or a TMR memory cell. For this it is only necessary for the intermediate layer to be constructed in the form of a thin dielectric layer and an electric current applied perpendicular to the plane of the intermediate layer. In this case the intermediate layer acts as a tunnel barrier, wherein advantageously large resistance changes occur in this tunnel barrier for currents perpendicular to the plane of the intermediate layer as a function of an external magnetic field.

Advantageously, by and large, the layer system according to the invention is suitable for use in a magnetic memory cell (MRAM or "Magnetic Random Access Memory"), a magnetic disc read head, a GMR ("Giant Magneto Resistor") sensor, a TMR ("Tunnel Magneto Resistor") sensor or generally in a magnetic sensor for contactless detection of displacement, speed and angular velocity, as well as physical measured variables, for example in motor vehicles.

Drawings Exemplary embodiments of the invention are explained in further detail in the description below with the"aid of the drawings. Figure 1 shows a simple schematic sketch of a magnetoresistive layer system, Figures 2 and 3 explain a first exemplary embodiment of a magnetically sensitive component with magnetoresistive layer systems in a plan view of a bridge circuit, Figures 4a and 4b show sectional views of a second exemplary embodiment for producing a magnetically sensitive component on a substrate with magnetoresistive layer systems in strip-like regions, Figure 4c shows a further development of Figure 4b, wherein a layer system is produced from Figure 3, based on Figure 4b and as an alternative to Figure 4c Figure 5 shows a further exemplary embodiment and Figure 6 shows an alternative exemplary embodiment to Figure 2 as shown in Figure 4a or Figure 5.

Exemplary embodiments First of all Figure 1 shows a schematic sketch of a magnetoresistive layer system 20 with a detection layer 1 made from a soft magnetic material, which has a magnetisation mi which has a direction indicated for example by the arrow. Furthermore, the layer system 20 has an intermediate layer 3 made of an electrically conductive, non-magnetic material, through which a current I flows in the plane of the intermediate layer 3. Finally, a reference layer 2 made from a hard magnetic material and which has a magnetisation m2, whose direction is indicated by the arrow, for example, is placed on the intermediate layer 3 on the side opposite the detection layer 1.

Figure 2 shows a schematic sketch of an electrical circuit in the form of a Wheatstone bridge 21 which consists of a first half bridge 22 and a second half bridge 23, each having the respective bridge resistors Ri and R2 and R3 and R4' In a Wheatstone bridge 21 an externally injected voltage U. is first applied and, furthermore, the bridge resistors R1, R21 R3 and R4 are adjusted or rated so that the bridge voltage UB is minimal or preferably zero. Furthermore, in Figure 2, each of the bridge resistors R1. R21 R3 and R4 is formed by a magnetoresistive layer system 20; in Figure 2, the direction of the magnetisation m2 of the reference layer being indicated in each case by the arrows in Figure 1.

Figure 3 explains a first exemplary embodiment of a magnetically sensitive component 30 with magnetoresistive layer systems 20 in a bridge circuit. For this the magnetoresistive layer systems 20 are arranged on a substrate 10 in a first strip-like region 31 and a third strip-like region 33, the magnetoresistive layer systems 20 forming the bridge resistors Ri and R3 having a magnetisation m2 orientated parallel to each other, and the magnetoresistive layer systems 20 forming the bridge resistors R2 and R4 also having a magnetisation m2 orientated parallel to each other. The direction of the magnetisation m2 of the layer systems 20 forming the bridge resistors Ri and R3 and the direction of the magnetisation M2 of the layer systems 20 forming the bridge resistors R2 and R4 are, furthermore, opposite to each other.

Analogous with Figure 2, the connection of the individual bridge resistors as shown in Figure 3 is effected in the known manner by printed conductors, not shown, which have been deposited or produced via known patterning processes in microfabrication technology. Since the bonding, voltage supply and interconnection are known to the expert, these are not dealt with in detail here.

Figures 4a and 4b and 4a to 4c, respectively, explain the manufacturing process of' a magnetically sensitive component 30 on a substrate 10, a magnetically sensitive component 30 with the general construction shown in Figure 3 resulting at the end of this manufacturing process. Figure 4c is a sectional view of Figure 3.

In detail, to produce a magnetically sensitive component 30 according to the invention, the starting point, as shown in Figure 4a, is a substrate 10, for example a silicon wafer or chip, whose surface consists of thermally oxidised silicon. Furthermore, an optional buffer layer 11 consisting of a tantalum or NiFe layer, each with a thickness of a few nm, is next deposited on the surface of the substrate 10 by the sputter technique, for example. A detection layer 1 which preferably consists of a soft magnetic material, in particular NiFe or FeCo, is then deposited on the buffer layer 11 in the known manner. Here the detection layer 1 is deposited in the known manner so that it has a magnetisation ml, whose direction can be varied under the influence of an external magnetic field, and which is adjusted in each case so that it is orientated at least largely parallel to a component of the external magnetic field that is aligned parallel to the plane of the detection layer 1 at the location of the respective magnetoresistive layer system 20 to be produced at that point.

In a next step, an intermediate layer 3 is then deposited on the detection layer 1. In the illustrated example this intermediate layer 3 consists of an electrically conductive material, preferably a non- magnetic metal such as copper. 5 However, if it is wished to construct a TMR sensor element instead of a GMR sensor element, a dielectric material, preferably aluminum oxide, is also a suitable material for the intermediate layer 3. Since the basic mode of operation of GMR sensor elements or TMR sensor elements is known, their mode of operation is not dealt with in detail here.

After the intermediate layer 3 is deposited, as shown by Figure 4a, a pattern in the form of a sacrificial layer 12 is produced in the region of a second strip-like area 32, for example by depositing a suitably structured photoresist as masking. After this sacrificial layer 12 is deposited, a first partial layer 2a of the reference layer 2, which preferably consists of a hard magnetic material, for example cobalt with a homogenous magnetic orientation, or a soft magnetic material, for example NiFe or FeCo, is extensively deposited on the reference layer 2, in particular also on the sacrificial layer 12. A second partial layer 2b consisting of an antiferromagnetic material is then produced on the first partial layer 2a.

In detail, to achieve this, the second partial layer 2b is formed for example by an NiO, iridium-manganese, platinummanganese or manganese-iron layer with a thickness of a few nm. At the same time, to produce the direction of the magnetisation m2 during the deposition of the second partial layer 2b and preferably also during the deposition of the first partial layer 2a of the reference layer 2, a homogeneous external magnetic field H is applied, whose direction is identified in Figure 4a by the arrow, and which produces in the reference layer 2 a corresponding orientation of the magnetisation M2 of the reference layer 2.

In detail, due the deposition during an applied orientated external magnetic field H, the second antiferromagnetic partial layer 2b produces in the known manner a permanent induction and stabilisation of the direction of the magnetisation of the first partial layer 2a, so that after the deposition and after the external magnetic field H applied during the deposition is switched off, its direction is no longer able to be changed by external magnetic fields or interference fields occurring thereafter. The direction of the magnetisation m2 is thus permanently fixed in the reference layer 2.

is Figure 4b illustrates how, after the deposition of the reference layer 2, the sacrificial layer 12 is removed by a so-called known lift-off process, so that a patterning of the surface of the substrate 10 is produced in adjacent, strip-like areas 31, 32, only the reference layer 2 with its associated magnetisation m2 remaining in the area 31. On the other hand, the reference layer 2 previously deposited on the sacrificial layer 12 has been removed in the region of the second strip-like area 32.

The surface of the layer system according to Figure 4b is then further patterned so that two plane or meander-shaped bridge resistors are produced inside each of the first and second strip-like areas 31, 32. For this, the two bridge resistors R2 and R4 are fabricated from the first area 31 and the two bridge resistors R. and R6 from the second area 32 as shown in Figure 6, and connected up via the two half bridges 22, 23 to form the Wheatstone bridge 21. In this exemplary embodiment the bridge resistors R5 and R6 are purely ohmic resistors formed by the intermediate layer 3 or detection layer 1, respectively, which exhibit no GMR effect.

In a further development of Figure 4b, Figure 4c explains a further exemplary embodiment and provides for an'additional second reference layer 2' to be deposited on the substrate 10. Firstly, its construction is fully analogous with the construction of the reference layer 2, but it extends over the entire surface of the substrate 10. Furthermore, during the deposition of the second reference layer 2' the direction of the external magnetic field H applied during the deposition is opposite to the direction of the chosen external magnetic field H during the deposition of the first reference layer 2.

As a result, a third strip-like area 33 in which the second reference layer 2' is located on the intermediate layer 3, !5 that itself is reconstructed from a third partial layer 2aand a fourth partial layer 2b-, is produced on the substrate 10. In this case the construction of the third partial layer 2a- is analogous to the first partial layer 2a and the fourth partial layer 2b' is analogous to the second partial layer 2b in Figure 4a.

However, the two reference layers 2' and 2 in Figure 4c differ in that the directions of the respective magnetisations m2 and M2,, respectively, are opposite to each other.

Following the completion of the layer construction as shown in Figure 4c and its fabrication into bridge resistors Ri to R4 as shown in Figure 3, the surface of the substrate 10 is the provided in the known manner by depositing conductive layers for interconnection as well as isolation and protective layers in accordance with the prior art.

This interconnection is implemented in such a way that two magnetoresistive layer systems 20 are produced in the region of the third strip-like region 33, which are connected as bridge resistors Ri and R3. as shown in Figure 3. Similarly, the connection in the first strip-like area 31 is realised in such a way that two magnetoresistive layer systems 20, that are interconnected as bridge resistors R2 and R4. are produced, as shown in Figure 3. 5 An electrical circuit in the form of a Wheatstone bridge 21 is produced in this way, the bridge resistors R, to R4 being formed by magnetoresistive layer systems 20, of which each pair has respective magnetisation directions M2 and M2, that are parallel to each other. The third area 33 therefore corresponds to the first strip 5 in Figure 3 and the first area 31 the second strip 6 in Figure 3. Furthermore, the Wheatstone bridge thus produced consists of a first half bridge 22 and a second half bridge 23 and is connected in the known manner to the applied external voltage UO and on the other hand with a device for measuring the bridge voltage U., Incidentally, it is obvious that several Wheatstone bridges 21 can be produced on the substrate 10 according to Figure 4b or Figure 4c, by patterning the substrate 10 in strip-like areas, each of which has suitable, if necessary, different magnetisation directions.

If several Wheatstone bridges 21 are produced on or fabricated from one substrate 10, this is preferably achieved in such a way that the magnetisation directions M2 and m2,, respectively, between the individual bridges 21 are orientated perpendicular to each other in each of the various layer systems 20 which form these Wheatstone bridges 21. In this way an angular measurement over a full 3600 is possible with a magnetically sensitive component 30, the other advantages according to the invention being retained.

Figure 6 explains an exemplary embodiment in which, compared to Figure 2 or Figure 3, the bridge resistors R.

and R6 are constructed as inactive bridge resistors. As shown by Figure 6, a Wheatstone bridge thus contains two half bridges 22, 23 which have a respective bridge resistor R21 R4, which themselves are formed by a magnetoresistive layer system 20 with a reference layer 2, 2-. As already explained above, in detail the substrate 10 if first patterned exactly like the first exemplary embodiment, so that a layer construction of the magnetically sensitive component 30 is produced, as explained with the aid of Figure 4b. However, the deposition of the second reference layer 2', as explained in the above exemplary embodiment with the aid of Figure 4c, is dispensed with, and patterning of the first and second area 31, 32, respectively, is carried out directly, as shown in Figure 4b.

In detail, for this, two magnetoresistive layer systems 20, which have an identical direction of magnetisation m2, are fabricated from the first area 31, and subsequently form the bridge resistors R2 and R4 as shown in Figure 6. Here the direction of the magnetisation m2 in Figure 6 is shown by the arrow. Furthermore, as shown in Figure 4b, the second area 32 is likewise patterned in the known manner so that two inactive bridge resistors R. and R6 are produced.

Following this, these bridge resistors R2, R41 R.. and R6 are interconnected in the known manner to form the Wheatstone bridge 21 as shown in Figure 6, and, as already stated in the previous exemplary embodiment, provided with conductive layers for interconnection, as well as isolation and protective layers in accordance with the prior art.

The two inactive bridge resistors R. and R. in Figure 6 are thus formed by the intermediate layer 3 and are purely ohmic resistors that are not sensitive to the direction of an external magnetic field. The Wheatstone bridge 21 shown in Figure 6 therefore contains only two magnetoresistive layer systems 20, which have identical magnetisation direction and where a magnetoresistive layer system 20 is assigned to each half bridge 22, 23 of the Wheatstone bridge 2 1.

With the same injected voltage U01 the available bridge output voltage UB of the Wheatstone bridge 21 as shown in Figure 6 actually amounts to only half that of the circuit shown in Figure 2 with four magnetoresistive layer systems 20 as bridge resistors R1, R21 R3 and R4. However, the advantage of a temperature- independent offset of the bridge output voltage U. is also obtained in Figure 6 since all bridge resistors R2. R41 R. and R. consist of the same material.

Incidentally, it should be mentioned that it is also possible to construct the bridge resistors R. and R. as external ohmic resistors, that is to say as resistors that have not been produced on the substrate 10, but are connected as external resistors in the known manner by means of an electronic circuit to the magnetically sensitive bridge resistors R2 and R4 located on the substrate 10, in the manner explained, in the fashion of a Wheatstone bridge or two half bridges.

Figure 5 explains a further exemplary embodiment.for realising a magnetically sensitive component 30 with a Wheatstone bridge 21, that is connected according to Figure 6. The embodiment of Figure 5 differs from that of Figure 4b only in that in Figure 5 the f irst partial layer 2a is also deposited in a fourth area 34 that corresponds to the second area 32 in Figure 4b.

In detail, to achieve this, as shown in Figure 5, the first partial layer 2a has been deposited on the entire surface of the substrate 10. Following this, a patterning of the surface of the substrate 10 is then carried out in striplike areas 31, 34, for example via a suitable masking in the region of the fourth area 34, which then follows a deposition of the second partial layer 2b while simultaneously applying the external magnetic field H as in Figure 4b for producing an orientated magnetisation m 2 in the first area 31. The masking in the region of the fourth area is then removed again.

Otherwise, the production of the layer structure as shown in Figure 5 is completely analogous to the exemplary embodiment explained with the aid of Figures 4a and 4b, that is to say in Figure 5 a soft magnetic first partial layer 2a, consisting of NiFe, for example, is first deposited on the surface of the intermediate layer 3 and after this the antiferromagnetic partial layer 2b, for example consisting of NiO or iridium-manganese, is deposited in the first strip-like area 31.

The result of this is that the soft magnetic first partial layer 2a in the strip-like fourth area 34 is always orientated in the direction of an external magnetic field, so that no magnetic field-dependent resistance change is caused, whereas in the first strip-like area 31, due to the antiferromagnetic partial layer 2b in the first partial layer 2a, there is always at least a largely unaffected residual magnetisation whose direction is constant, and which is therefore available as a reliable reference, even in the presence of strong external magnetic fields or interference fields.

Thus, all in all, a change in the direction of the magnetisation in the detection layer 1 is brought about in the first strip-like area 31 by an external magnetic field, so that a magnetoresistive effect occurs, wherein the fact that the antiferromagnetic second partial layer 2b has no resulting external magnetic moment is utilised to the effect that it cannot subsequently be orientated or influenced by an external magnetic field.

Incidentally it is obvious that the sequence of layers explained with the aid of Figures 4a to 4c and 5 can also be interchanged in the magnetically sensitive component 30. It is thus easy, for example, to first deposit a buffer layer 11 on the substrate 10, then on top of that a first reference layer 2 and optionally a second reference layer 2', onto which the intermediate layer 3, followed by the detection layer 1, is then deposited. Furthermore, the magnetically sensitive component 30 can also use the so-

called TMR effect instead of the GMR effect, whereby the intermediate layer 3 is not made conductive but formed from a dielectric material, in particular A1203' In this case, the current I gen erated by the external voltage source U. does not flow in the plane of the intermediate layer 3 but perpendicular to it, wherein the intermediate layer 3 forms a tunnel barrier and the tunnel current is determined by the direction of the magnetisations of the detection layer 1 or the first and/or second reference layer 2, 2'. Such circuits are known to the expert.

Moreover, in certain cases it is advantageous to provide the first and third partial layer 2a, 2a' of the reference layers 2 and 2', respectively, at least of a magnetoresistive layer system 20 of the magnetically sensitive component 30, at least on the surface and at least in regions with a patterning that, in addition to the effect of the antiferromagnetic second and fourth partial layer 2b, 2b', respectively, counteracts a change in the direction of the magnetisation m2 of the first and third partial layer 2a, 2a', respectively.

This patterning is preferably a corrugated or sawtooth topography whose structures at least largely exhibit a uniaxial preferred direction which is orientated at least largely parallel to the direction of the magnetisation M2 and/or at least largely parallel to the direction of the magnetisation m2, List of reference numbers 1 Detection layer 2 First reference layer 2a First partial layer 2b Second partial layer 2' Second reference layer 2a' Third partial layer 2b' Fourth partial layer 3 Intermediate layer First strip 6 Second strip Substrate 11 Buffer layer 12 Sacrificial layer Layer system 21 Wheatstone bridge 22 First half bridge 23 Second half bridge Magnetically sensitive component 31 First area 32 Second area 33 Third area 34 Fourth area

Claims

1. Magnetically sensitive component, in particular a sensor element, having at least two magnetoresistive layer systems (20) exhibiting a GMR or TMR effect, produced in regions on a substrate (10), each with at least one reference layer (2, 2'), at least one intermediate layer (3) adjacent to the reference layer (2, 2') and at least one detection layer (1) adjacent to the intermediate layer (3), wherein the magnetoresistive layer systems (20) are connected as bridge resistors (R2, R4) in an electrical circuit in the form of a Wheatstone bridge (21), characterised in that at least one of the reference layers (2, 2-) has at least one magnetoresistive layer system (20), at least one first partial layer (2a, 2a') and at least one second partial layer (2b, 2b'), wherein the first partial layer (2a, 2a') has a magnetisation (m2) and the second partial layer is an antiferromagnetic partial layer (2b, 2b-).

2. Magnetically sensitive component according to Claim 1, characterised in that the electrical circuit in the form of a Wheatstone bridge has two half bridges (22, 23), each of which has at least one magnetoresistive layer system (20)

3. Magnetically sensitive component according to Claim 1, characterised in that the electrical circuit has at least one Wheatstone bridge (21) with four magnetoresistive layer sys tems (20) as bridge resistors (R1, R21 R3/ R4), and/or that the electrical circuit has at least one Wheatstone bridge (21) with two half bridges (22, 23), each of which has a magnetoresistive layer system (20) as a bridge resistor (R2. R4) and a resistor (R., R6) that is independent of an external magnetic field.

4. Magnetically sensitive component according to Claim 1, characterised in that the magnetoresistive layer systems (20) are connected in such a way that a bridge output voltage (U.), that can be varied by an external magnetic field, is at least largely temperature- independent and/or largely offset-free at least in the range from -400C to 1500C.

5. Magnetically sensitive component according to Claim 1, characterised in that in at least one layer system (20) the detection layer (1) is arranged on a substrate (10) that is provided in particular with a buffer layer (11), and that the intermediate layer (3) is arranged on the detection layer (1) and the reference layers (2, 2') are arranged on the intermediate layer (3).

6. Magnetically sensitive component according to Claim 1, characterised in that in at least one magnetoresistive layer system (20) the reference layers (2, 2') are arranged on a substrate (10) that is provided in particular with a buffer layer (11), and that the intermediate layer (3) is arranged on the reference layers (2, 2') and the detection layer (1) is arranged on the intermediate layer (3).

7. Magnetically sensitive component according to Claim 1, characterised in that each of the detection layers (1) of the magnetoresistive layer systems (20) has a first magnetisation (ml) at least in the region of its surface facing the intermediate layer (3).

8. Magnetically sensitive component according to Claim 1, characterised in that in at least one magnetoresistive layer system (20) the direction of the magnetisation (M2) of the first partial layer (2a, 2a') is orientated at least largely parallel to the plane of the first partial layer (2a, 2a-) and the direction of the first magnetisation (ml) of the detection layer (1) is orientated at least largely parallel to the plane of the detection layer (1) 5

9. Magnetically sensitive component according to Claim 1, characterised in that in at least one magnetoresistive layer system (20) the direction of the magnetisation (M2) of the first partial layer (2a, 2a') is always at least largely unchanged even under the influence of, in particular, an arbitrarily orientated and/or strong, magnetic external field.

10. Magnetically sensitive component according to Claim 7, characterised in that in at least one magnetoresistive layer system (20) the direction of the magnetisation (ml) of the detection layer (1) can be varied under the influence of an external magnetic field, and adjusted in each case so that it is orientated at least largely parallel to a component of the external magnetic field that is aligned parallel to the plane of the detection layer (1) at the location of the respective magnetoresistive layer system (20).

11. Magnetically sensitive component according to Claim 1, characterised in that at least one intermediate layer (3) of a magnetoresistive layer system (20) has an electrically conductive material, ii7l particular a non-magnetic metal, and/or that at least one intermediate layer (3) of a magnetoresistive layer system (20) has a dielectric material, in particular A1203.

12. Magnetically sensitive component according to Claim 1, characterised in that at least one detection layer (1) of at least one magnetoresistive layer system (20) has, at least in regions, a soft magnetic material, in particular NiFe or FeCo.

13. Magnetically sensitive component according to Claim 1, characterised in that at least one first partial-layer (2a, 2a') has, at least in regions, a hard magnetic material, in particular cobalt with homogeneous magnetic orientation, or a relatively soft magnetic material, in particular, NiFe or FeCo.

14. Magnetically sensitive component according to Claim 1, characterised in that at least one second partial layer (2b, 2b') has an antiferromagnetic material, in particular NiO, IrMn, MnFe or PtMn.

15. Magnetically sensitive component according to Claim 1, characterised in that the substrate (10) is a silicon substrate or a thermally oxidised silicon substrate, in particular a wafer or chip, and that the magnetically sensitive component (30) is constructed on the substrate (10) in a monolithic, integrated form.

16. Magnetically sensitive component according to Claim 5 or Claim 6, characterised in that the buffer layer (11) is a tantalum layer or a NiFe layer.

17. Magnetically sensitive component according to at least one of the preceding Claims, characterised in that the second partial layer (2b, 2b') induces a magnetisation in the first partial layer (2a, 2a') at least in the surface.

18. Magnetically sensitive component according to at least one of the preceding Claims, characterised in that the magnetically sensitive component (30) has at least two magnetoresistive layer systems (20), wherein the magnetisation (m2) of at least one first partial layer (2a, 2a') of a layer system (20) is, at least approximately, opposed to the magnetisation (m2) of at least one partial layer (2a, 2a') of another layer system (20).

19. Magnetically sensitive component according to at least one of the preceding Claims, characterised in that the magnetically sensitive component (30) has at least two magnetoresistive layer systems (20), wherein the magnetisation (m2) of at least one first partial layer (2a, 2a-) of a layer system (20) is, at least approximately, perpendicularly opposed to the magnetisation (m2) of at least one partial l'ayer (2a, 2a-) of another layer system (20).

20. Magnetically sensitive component according to at least one of the preceding Claims, characterised in that the substrate (10) is subdivided into at least two strip-like regions (31, 32, 33, 34), wherein two adjacent areas (31, 32) have differently aligned directions of magnetisation (m2. M2,) of at least one reference layer (2, 2'), that are in particular at least approximately opposite or rotated by 900 to each other, wherein the directions of the magnetisations (m2, m2') are at least more or less unchanged under the influence of an external magnetic field, or wherein of two adjacent regions (31, 32) of one region (32) without a reference layer, one is a region with a non-magnetic reference layer or one is a region (34) with a soft magnetic reference layer (2a), whose direction of magnetisation can be aligned at least largely parallel to an external magnetic field, and wherein one is a region (31) with at least one reference layer (2, 2') with a magnetisation (m2) that is more or less unchanged under the influence of an external magnetic field.

21. Magnetically sensitive component according to Claim 20, characterised in that the magnetically sensitive component (30) has at least two magnetoresistive layer systems (20) in at least two regions (31, 33) with reference layers (2, 2') with differently oriented magnetisation (m2, M2') that is at least more or less unchanged under the influence of an external magnetic field.

22. Magnetically sensitive component according to Claim 20, characterised in that the magnetically sensitive component (30) has at least one magnetoresistive layer system (20) in one region (31, 33) with a reference layer (2, 2') with a magnetisation (m2) that is at least more or less unchanged under the influence of an external magnetic field, and that the magnetically sensitive component (30) has at least one magnetoresistive layer system (20) in one region (32) without a reference layer, one region with a non-magnetic reference layer or one region (34) with a soft magnetic reference layer (2a), whose direction of magnetisation can be orientated at least largely parallel to an external magnetic field.

23. Magnetically sensitive component according to at least one of the preceding Claims, characterised in that at least the first partial layer (2a, 2a') of the reference layer (2, 2') of at least one magnetoresistive layer system (20) is provided with patterning at least on the surface and at least in regions, in such a way that the patterning opposes a change in the direction of the magnetisation (m2) of the first partial layer (2a, 2a')

24. Magnetically sensitive component according to Claim 23, characterised in that the patterning is a topography with a corrugated or sawtooth profile, wherein its structures have at least a largely uni-axial preferred direction that is orientated at least largely parallel to the direction of the magnetisation (m2) of the first partial layer (2a, 2a').

25. Magnetically sensitive component according to Claim 23, characterised in that the detection layer (1) and/or the intermediate layer (3) have in particular a corrugated topography at least on one side, that at least largely corresponds to the patterning of the reference 5 layer (2, 2').

26. Magnetically sensitive component according to at least one of the preceding Claims, characterised in that at least one magnetoresistive layer system (20) exhibits a change in the electrical resistance of the intermediate layer (3) when under the influence of an external magnetic field, wherein the change in the electrical resistance is a function of the angle between the magnetisation (m,) of the first partial layer (2a, 2a') and the magnetisation (ml) of the detection layer (1), and wherein the electrical resistance of the intermediate layer (3) is the electrical resistance that can be measured when an electric current flows parallel to or perpendicular to the plane of the intermediate layer (3)

27. Any of the megnetically sensitive components substantially -as hereinbefore described with reference to the accompanying drawings.