JP2000049029A - Manufacture of layer structure containing artificial antiferromagnetic system and magnetoresistance sensor system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a layer structure where a magnetoresistance sensor system comprising at least two sensor elements is formed, a method for allowing the layer structure or a corresponding sensor element to be oriented anti-parallel to the magnetization of a bias layer in a homogeneous adjustment magnetic field by a simple method, and a magnetoresistance sensor system. SOLUTION: A magnetoresistance sensor system has at least at artificial antiferromagnetic system(AAF system) comprising at least one bias layer 5, at least one magnetic flux guiding layer 7 formed. At least one combination layer 6, which provided between the layers, combines the adjoining both magnetic layers in antiferromagnetism, with at least two sensor elements being provided, such that a range where layer structure is affected and that which is not affected partially effect on the symmetry of the AAF system for different behaviors in a homogeneous magnetic field, after the AAF system has been formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to at least one bias layer, at least one flux induction layer, and at least one coupling layer disposed between these layers and anti-ferromagnetically coupling two adjacent magnetic layers. Artificial-antiferrom system
The present invention relates to a method for manufacturing a layered structure that can form a magnetoresistive sensor system having at least two sensor elements, including a magnetic-system (hereinafter, referred to as an AAF system).

[0002]

2. Description of the Prior Art For forming a sensor bridge which can be used, for example, for a 360 ° angle detector and which exhibits a magnetoresistive effect, two of the four sensors forming this bridge are used. Need to be oriented in the opposite direction with respect to the magnetization of the bias layer with respect to the other sensors to obtain a corresponding signal over the entire angular range. This is also necessary in the case of sensors based on magnetic tunneling or operating with spin valve transistors. This is performed by a magnetic adjustment field (adjustment magnetic field). The disadvantage in this case, however, is that in the adjacent sensor elements forming the bridge, the adjustment field must be oriented differently from sensor element to sensor element and the direction of magnetization must be forced. This is due to the fact that the structure of all sensor elements is the same in the sensor bridge or on the entire sensor substrate including multiple sensor bridges.

[0003]

SUMMARY OF THE INVENTION The object of the invention is to provide a method in which a layer structure or a corresponding sensor element can be achieved or formed in a simple manner with different orientations of the magnetization of the bias layer in a homogeneous adjusting field. Is to do.

[0004]

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided, in accordance with the present invention, an AAF system that is partially formed after an AAF system has been formed to allow for partially anti-parallel orientation of the bias layer magnetization. Affect the symmetry of the system,
In a homogeneous magnetic field, a range affected by the layer structure and a range not affected by the layer structure behave differently.

In other words, the invention starts with one and the same layer structure for all sensor elements or for all areas in which sensor elements are to be formed. According to the present invention, the partial symmetry of the system allows to form different ranges which exhibit different behavior. According to the invention, a mask can be used to partially affect the layer structure.

[0006] According to a first embodiment of the present invention, an auxiliary layer is formed which is partially magnetically coupled to one or more regions and which produces a partially asymmetric behavior in regions within a homogeneous magnetic field. You may make it contribute. That is, another layer is added, but this layer is added only to the area where the magnetization must be adjusted in the opposite direction to the area without the auxiliary layer. According to the invention, this partial auxiliary layer can then be deposited through a mask. Alternatively, a completed layer is first applied and the area corresponding to the area which should not be affected by this layer is removed by means of a mask.

[0007] As described above, an auxiliary layer is deposited on the AAF system. In order to protect the AAF system against damage or possible changes in the composition of the layer during the deposition process, it is advantageous to apply a cover layer on the bias layer or flux induction layer before forming the auxiliary layer. .

After completion of the layer structure, the adjustment can be effected by means of a homogeneous magnetic field, after which the auxiliary layer is advantageously not necessary for the final formation of the sensor system and its operation, and is therefore advantageously removed. If the auxiliary layer is previously applied as a complete layer over the entire substrate and only a certain area is removed, a second mask can be used for the removal. The second mask must be processed so that other areas of the auxiliary layer can also be removed.

Another method for forming a partial auxiliary layer, on the other hand, involves a partial A
The composition and / or thickness of one layer of the AF system is changed. This change in composition or thickness also affects the behavior of each region in a homogeneous magnetic field, so that antiparallel orientation can be achieved. According to the invention, this modification may be performed by partial oxidation, partial implantation and / or in a partial etching step. Again, in order to protect the AAF system at least to the extent that it must not be affected, the present invention may apply a cover layer on top of the bias layer or flux induction layer prior to this effect, and modify this layer. The area to be removed is optionally removed using a mask. Such a mask is advantageously formed by lithography, in particular by photolithography.

As described above, this layer structure is a unitary structure that is not divided into separated sensor elements. To structure the individual isolated sensor elements corresponding to the ultimately affected and unaffected areas,
Advantageously, those regions arranged on a common substrate are decoupled or separated from one another before the adjustment of the magnetization, which is easily achieved by a partial etching step, especially before the removal of the mask takes place. .

The invention further relates to a layer structure for forming a magnetoresistive sensor element or a magnetoresistive sensor system manufactured by the above method.

In another aspect, the invention comprises at least two sensor elements, each having at least one bias layer, at least one flux induction layer, and at least one disposed therebetween to couple the two layers antiferromagnetically. The invention relates to a magnetoresistive sensor system having an AAF system consisting of two tie layers. The sensor system provides a sensor element or a portion of a plurality of sensor elements with an asymmetric behavior of the sensor element in a homogeneous magnetic field to allow anti-parallel orientation of the bias layer magnetization. In that it comprises at least one magnetically coupled auxiliary layer that contributes to

In this case, according to the invention, the auxiliary layer contributes to the moment, ie the magnetic moment of the layer to which the auxiliary layer is connected is increased. Additionally or alternatively, the auxiliary layer contributes to the holding force, i.e. the total frictional moment of the connection between the auxiliary layer and the layer connected thereto is changed. Similarly, the auxiliary layer also contributes to magnetic anisotropy leading to partial asymmetry. The auxiliary layer may be a ferromagnetic, antiferromagnetic or ferrimagnetic layer. The phase transition temperature of the auxiliary layer, possibly the Curie temperature or the Neel temperature, may be below the operating temperature range of the sensor system. If the operating temperature range is, for example, room temperature, the sensor system is cooled to a temperature below the phase transition temperature for adjustment. That is, the sensor system is brought to a temperature range to which the auxiliary layer can contribute. In contrast, at the operating temperature, the auxiliary layer behaves paramagnetically.

The auxiliary layer may be applied directly on the bias layer or the flux induction layer, or alternatively, the bias layer or the flux induction layer may be provided with a cover layer, on which the auxiliary layer is applied and both layers You may make it couple | bond magnetically. It is furthermore advantageous if the auxiliary layer is removable, in particular etchable. In the case of a sensor system, each of the four sensors of the sensor system may be subject to possible variations in the sensor elements, especially if they are not formed on a common substrate, temperature fluctuations that may affect the measurement signal. It is advantageous to combine the components in a Wheatstone bridge manner. Thus, sufficient temperature compensation can be obtained.

The invention further relates to another magnetoresistive sensor system corresponding to a sensor system of the type described above. The sensor system may have a layer of a sensor element or a layer of a plurality of sensor elements, and thus each A, to allow anti-parallel orientation of the magnetizations of the plurality of bias layers.
The advantage is that the symmetry of the AF system is influenced such that the affected and unaffected sensor elements behave differently in a homogeneous magnetic field. According to the invention, this layer can change its composition and / or its thickness by this effect, which can be achieved by partial oxidation, partial implantation and / or partial etching. In this case as well, it is advantageous to combine the four sensor elements in each case in a Wheatstone bridge manner in consideration of temperature compensation.

Finally, the present invention provides another sensor system comprising at least one bias layer and a plurality of magnetic flux guiding layers, wherein one of the sensors is provided to allow the magnetization of the bias layer to be antiparallel. A part of the magnetic flux induction layer of the sensor element or the plurality of sensor elements has been removed,
Thereby, different layer behaviors can be achieved in a homogeneous magnetic field as well.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The advantages and features of the present invention will be clarified with reference to the embodiments described below and the drawings.

FIG. 1 shows a section of the layer structure.
This layer structure includes a substrate layer 1, a buffer layer 2, a measurement layer 3, a decoupling layer 4, a bias layer 5, an antiferromagnetic coupling layer 6, and a magnetic flux guiding layer 7. Layers 5, 6, 7 form an AAF system. This layer structure, which is provided as homogeneously as possible over the entire sensor substrate, is only partially shown in the drawing, but is provided thereon with a cover layer 8 which protects the underlying AAF system. Applying an auxiliary layer that makes a significant contribution to magnetism over a partial cover layer so that the behavior of the AAF system in a homogeneous magnetic field can be partially influenced so as to obtain partially different behaviors . Cover layer 8
Couples the applied auxiliary layer to the underlying layer of the AAF system (in this example, the flux guiding layer 7). Each first
Around a partly selected area of the auxiliary layer corresponding to a sensor element of the type (the area without the auxiliary layer is the second
A sensor element of the type described above, which differs in the magnetization layer and the bias layer), is provided with a lithographic mask 9 having corresponding windows 10 on the cover layer (see FIG. 2). Through this window 10 an auxiliary layer 11 (in this case only shown with broken lines) is deposited. Auxiliary layer 11
By coupling this to the underlying magnetic flux guiding layer 7, the behavior of this AAF system area in the magnetic field is partially changed, so that a reverse biasing of the sensor element can be achieved. Prior to adjusting the magnetization with a homogeneous magnetic field, the individual areas are separated from one another by a partial selective etching process, which is performed primarily along the edges of the mask, vertically, to structure the sensor element. After adjusting the magnetization, the auxiliary layer and the mask, and in some cases, the cover layer can be removed.

The auxiliary layer is advantageously a ferromagnetic material having a low Curie temperature or an antiferromagnetic material having a low Neel temperature. The phase transition temperature of the auxiliary layer is below the operating temperature range of the sensor system, so that the auxiliary layer is paramagnetic in the operating temperature range, ie the magnetic behavior is not affected. To adjust the magnetization of the bias layer, a sensor system whose operating temperature is, for example, room temperature is cooled to a temperature below the phase transition temperature,
The auxiliary layer can therefore contribute in each case.

Unlike the method of applying the auxiliary layer as described above, the auxiliary layer may be applied first on the large surface and then partially removed by a mask. Subsequent removal requires a second mask.

The contribution of the auxiliary layer is a contribution to the moment, and may additionally or additionally be a contribution to the coercive force and / or the magnetic anisotropy.

When contributing to the moment, the auxiliary layer produces a magnetic moment at a controlled temperature. This moment depends on the selection of the auxiliary layer and, if appropriate, the cover layer, of the bias layer 5.
Can be parallel or antiparallel to magnetize. The direction of the magnetization M2 of the magnetic flux induction layer 7 is given by the following equation (1).

(Equation 1) Where M1 = saturation magnetization of bias layer M2 = saturation magnetization of flux induction layer d2 = thickness of bias layer d2 = thickness of flux induction layer Hein = adjustment magnetic field.

When M2d2> M1d1, the magnetization M2 is parallel to the adjusting magnetic field. The auxiliary layer produces an auxiliary moment mz at the regulated temperature. At this time, the direction of the magnetization of M2 is given by equation (2).

(Equation 2) Where the + sign indicates a parallel join of mz to M2,
The sign of-represents antiparallel coupling. The direction of M2 is given by equation (3)

(Equation 3) When it satisfies, it can be inverted.

The material of the auxiliary layer is Tbx (FeyCo
1-y) 1-x, Smx (FeyCo1-y) 1-x,
Hox (FeyCo1-y) 1-x, Dyx (FeyC
o1-y) 1-x, Ndx (FeyCo1-y) 1-x
Rare earth rich / rare earth / transition material alloys as well as weakened ferromagnetic materials can be used.

As described above, the control of the direction of magnetization can also be performed through coercive force or magnetic anisotropy. In this case, it is assumed that M2d2 = M1d1. Next, an antiferromagnetic or substantially antiferromagnetic auxiliary layer at the adjusted temperature is observed. This auxiliary layer is also directly or indirectly connected to the flux guiding layer 7 of the AAF system via a cover layer. When cooled below the Neel temperature, the magnetic spin becomes AA saturated by the magnetic field.
Oriented in the direction of the F system. However, since the antiferromagnetic auxiliary layer has no magnetic net (net) moment, the magnetization direction of M2 according to the above equation (1) is not specified. In this case, coercivity and magnetic anisotropy are important for orientation. In the case of the control by the coercive force, that is, the influence on the direction caused by the rotational friction, the equation (1) is expressed by the following equation (4).
a)

(Equation 4) [Where T1 = volume density of rotational friction of bias layer T2 = volume density of rotational friction of magnetic flux guide layer]

For uniaxial anisotropy having an easy axis parallel to the adjustment magnetic field of each layer and magnetic anisotropy constants K1, K2 and Kz, the equation (4b)

(Equation 5) Is applicable.

At temperatures below the Neel temperature, the auxiliary layer shows no magnetic moment, but in most cases the rotational friction Tzdz or the anisotropic energy Kzdz is quite large. The direction of the magnetization is therefore determined by the coercive force equation (5a).

(Equation 6) Or (5b) based on magnetic anisotropy

(Equation 7) It is performed based on.

Since it is clear that Tzdz is always positive, the reversal of the magnetization M2 is only possible when T2d2-T1d1 is less than 0, ie when the bias layer exhibits the maximum total friction. After reducing the magnetic field to zero at low temperature,
2 is antiparallel to the tuning field in the masked area and parallel in the unmasked area.

On the other hand, since Kz can have both positive and negative signs, M2 can be parallel to the tuning field even at low temperatures.

In this case, as a material, Tbx (FeyCo1) having a compensation temperature close to the adjustment temperature and a low Curie temperature is used.
-Y) 1-x, Hox (FeyCo1-y) 1-x, D
Rare earth rich rare earth / transition material alloys such as yx (FeyCo1-y) 1-x can be used. Similarly, pure antiferromagnets such as MnO, FeO, V2O3 or MnS can be used.

FIGS. 3 and 4 show another method for adjusting the antiparallel magnetization. Starting from the layer structure according to FIG. 3 in which the AAF system consists of a total of four magnetically active layers 12, 13, 14, 15, by means of a physical or chemical etching step, the structuring forms a first type of sensor element. To a certain extent, the layer 15 and the underlying tie layer 16
For example, as shown in FIG.
The following equation (6)

(Equation 8) In the condition (1), the antiparallel portion of the bias layer 12 in the structured range is obtained with respect to the unstructured range when the adjusting magnetic field is applied. The "+" sign of the M12d12 term corresponds to ferromagnetic coupling of the layer 12 to the layer 13, and the "-" sign corresponds to antiferromagnetic coupling of the layer 12 to the layer 13. In order to improve the homogeneity of the system (temperature-independent offset voltage), the sensor bridge portion, which has not yet been structured after adjustment, can also remove the layer 15 and the coupling layer 16.

[Brief description of the drawings]

FIG. 1 is a cutaway view of a layer structure without a mask.

FIG. 2 is a cutaway view of a layer structure with a mask.

FIG. 3 is a cross-sectional view of a layer structure including a multi-layer AAF system.

FIG. 4 is the layer structure of FIG. 3 with the magnetically relevant layers of the AAF system partially removed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate layer 2 Buffer layer 3 Measurement layer 4 Decoupling layer 5 Bias layer 6, 16 Coupling layer 7 Magnetic flux induction layer 8 Cover layer 9 Mask 10 Window 11 Auxiliary layer 12, 13, 14, 15 Magnetic effect layer

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Laurent Mattheis Germany 07743 Jena ter Rustrasse 36

Claims (34)

[Claims] At least one bias layer, at least one flux guide layer, and at least one coupling layer disposed between these layers and anti-ferromagnetically coupling two adjacent magnetic layers. A method of manufacturing a layer structure comprising an artificial antiferromagnetic system comprising at least two sensor elements, the method comprising the steps of: Partially affects the symmetry of the artificial antiferromagnetic system to allow for parallel orientation, and after forming the artificial antiferromagnetic system, the affected and unaffected areas of the layer structure will be A method for producing a layer structure including an artificial antiferromagnetic system, wherein the layer structure exhibits different behavior in the above. 2. The method according to claim 1, wherein a mask is used to partially affect the layer structure. 3. Forming, in a region or regions, a magnetically coupled auxiliary layer (11) which in a homogeneous magnetic field contributes to these regions exhibiting partially asymmetric behavior. The method according to claim 1 or 2, wherein: 4. The method according to claim 3, wherein the partial auxiliary layer is deposited through a mask. 5. The method according to claim 2, wherein a complete auxiliary layer is first applied and a corresponding area is removed from this layer by means of a mask. 6. A bias layer (5) before forming an auxiliary layer.
6. The method according to claim 2, wherein a cover layer (8) is applied on the magnetic flux guiding layer (7). 7. The method according to claim 2, wherein the auxiliary layer is removed after adjusting the magnetization with a homogeneous magnetic field. 8. The method according to claim 6, wherein a second mask or a first mask is used for the removal. 9. The method as claimed in claim 1, wherein the composition and / or the thickness of the layers of the artificial antiferromagnetic system are partially changed in order to influence them. 10. The method according to claim 9, wherein the modification is performed by partial oxidation, partial implantation and / or in a partial etching step. 11. A cover layer (8) is applied before the influence on the bias layer (5) or the flux guide layer (7) and, if necessary, a mask within the area of the cover layer (8) to be changed. The method according to claim 9 or 10, wherein the removal is carried out by using. 12. The method according to claim 1, wherein the layers involved in the magnetic behavior of the artificial antiferromagnetic system comprising a plurality of layers are partially removed for influencing. 13. The method according to claim 12, wherein the layer is removed by etching using a mask. 14. The method according to claim 12, further comprising removing the remaining area of the layer which has been partially removed after the adjustment by means of a homogeneous magnetic field. 15. The method according to claim 2, wherein each mask is formed by lithography, in particular by photolithography. 16. The method according to claim 1, further comprising decoupling or separating affected and unaffected areas of the layer structure arranged on the substrate to form individually separated sensor elements. 16. The method according to any one of 1 to 15. 17. The method according to claim 16, wherein these areas are decoupled or separated during a partial etching step, especially before the mask is removed. 18. A layer structure for forming a magnetoresistive sensor element or a magnetoresistive sensor system formed by the method according to claim 1. Description: 19. At least two sensor elements, each comprising at least one bias layer (5), at least one flux induction layer (7) and two adjacent magnetic layers arranged between these layers being made antiferromagnetic. In a magnetoresistive sensor system having an artificial antiferromagnetic system consisting of at least one coupling layer (6) that couples, one to allow the magnetization of the bias layer (5) to be partially antiparallel oriented. A sensor element or part of the plurality of sensor elements, comprising at least one magnetically coupled auxiliary layer (11), which contributes to the asymmetric behavior of the sensor element in a homogeneous magnetic field. Magnetoresistive sensor system. 20. The sensor system according to claim 19, wherein the auxiliary layer contributes to the moment. 21. Sensor system according to claim 18, wherein the auxiliary layer (11) contributes an additional coercivity if necessary. 22. The device according to claim 19, wherein the auxiliary layer contributes additional magnetic anisotropy.
22. The sensor system according to any one of claims 21 to 21. 23. The sensor system according to claim 19, wherein the auxiliary layer is a ferromagnetic, antiferromagnetic or ferrimagnetic layer. 24. The sensor according to claim 19, wherein the auxiliary layer has a phase transition temperature, possibly a Curie temperature or a Neel temperature, which is below the operating temperature range of the sensor system.
24. The sensor system according to any one of items 23 to 23. 25. A sensor as claimed in claim 19, wherein the auxiliary layer is provided directly on the bias layer or the magnetic flux guiding layer. system. 26. A cover layer (8) is provided on a bias layer (5) or a magnetic flux induction layer (7), and an auxiliary layer (11) provided thereon is magnetically coupled. A sensor system according to any one of claims 19 to 24. 27. The auxiliary layer according to claim 19, wherein the auxiliary layer is removable, in particular etchable.
The sensor system according to any one of the above. 28. A system comprising four or multiple sensor elements, each having four Wheatstone elements.
A bridge is formed.
8. The sensor system according to any one of 7 above. 29. At least two sensor elements, each having at least one bias layer (5), at least one magnetic flux guiding layer (7) and an adjacent magnetic layer disposed between these layers to antiferromagnetically couple. At least one
In a magnetoresistive sensor system having an artificial antiferromagnetic system comprising two tie layers (6), a bias layer (5)
In order to allow for the antiparallel orientation of the magnetization of a single or multiple sensor elements, the symmetry of the artificial antiferromagnetic system and of some of the layers of the sensor element is affected in a homogeneous magnetic field. A magnetoresistive sensor system, wherein the affected sensor element and the unaffected sensor element are affected so as to behave differently. 30. The sensor system according to claim 29, wherein the composition and / or the thickness of the layer are changed by an influence. 31. The sensor system according to claim 30, wherein this layer has been affected by partial oxidation, partial implantation and / or partial etching. 32. A sensor comprising four or multiple sensor elements, each having four Wheatstone elements.
A bridge is formed.
A sensor system according to any one of the preceding claims. 33. At least two sensor elements, each comprising at least one bias layer, a plurality of flux guide layers, and at least one coupling layer for antiferromagnetically coupling the bias layer and one flux guide layer. In a magnetoresistive sensor system having an artificial antiferromagnetic system, a flux guiding layer (15) of a sensor element or a portion of a plurality of sensor elements to enable antiparallel orientation of the magnetization of the bias layer. A magnetoresistive sensor system characterized in that the magnetic field is removed. 34. A sensor comprising four or multiple sensor elements, each having four Wheatstone elements.
34. The sensor system according to claim 33, wherein the sensor system forms a bridge.