WO2011134732A1

WO2011134732A1 - Wheatstone bridge having xmr spin-valve systems

Info

Publication number: WO2011134732A1
Application number: PCT/EP2011/054933
Authority: WO
Inventors: Manfred Rührig; Roland Weiss
Original assignee: Siemens Aktiengesellschaft
Priority date: 2010-04-30
Filing date: 2011-03-30
Publication date: 2011-11-03
Also published as: DE102010018874A1

Abstract

The invention relates to a Wheatstone bridge comprising bridge elements (1, 2, 3, 4) connected in a bridge circuit, each consisting of XMR/GMR spin-valve systems. Two selected bridge elements (2, 4) arranged diagonally to each other are bombarded with ions, whereby the XMR/GMR effect of the two selected bridge elements is reduced or destroyed. A monolithically integratable bridge structure is advantageously achieved in said system with low conditioning expenditure.

Description

description

Wheatstone Bridge with XMR Spinvalve Systems The invention relates to a Wheatstone bridge with bridging ^elements interconnected in bridge circuits, which consist of a GMR or TMR Spinvalve system and a process for their production. MR sensors, in particular GMR sensors, are an alternative to Hall sensors in the magnetic field-based position, speed, speed, field or even current sensor. Especially in the field of position and current sensors are during In recent years, MR-based sensors have been introduced into the marketplace. The main advantages compared to Hall sensors are in the simpler system structure, the greater noise immunity, due to the greatly reduced external field sensitivity and the lower Rau ^¬ rule. Above all, fully integrated solutions are suitable for MR-based sensors because the MR elements can be applied as a back-end process and thus do not require any additional chip area. For many applications, especially in the position, speed and current sensors, four MR elements into a so-called Wheatstone bridge are each comparable switches to a more accurate - to achieve measurement - temperature fluctuations inde ^¬ hängigere.

Magnetoresistive sensors are formed in a known manner in the form of Wheatstone bridges in order to minimize or completely suppress environmental influences such as temperature changes to the measurement signal. The construction of such Wheatstonebrü ^¬ CKEN requires that adjacent bridge arms of a half bridge when exposed to an external magnetic field with respect. the magnetoresistive change in resistance behaves contrary. This is comparatively easy to implement when using anisotropic magnetic materials, as in the permalloy (Ni81Fel9) used in classical MR sensors, in that Direction of two MR strip conductors within a half-bridge or by the use of Barberpolen the direction of the current flowing in the magnetoresistive bridge arms current is impressed differently.

Furthermore, layer systems with a so-called spinvalve effect are known, which are preferably used for detecting small fields or also for angle detection, as shown for example in DE 43 01 704 A1. These layer systems have in common that they consist of individual magnetic layers, in which ideally a sensor layer is magnetically easily rotatable and a reference layer is magnetically immovable. These layers may be so far only as a single magnetoresistive strip sensors manufactured is, thus, although comparatively high signals he ^¬ but are targetable, at all further interfering influences, such as temperature changes, affect the measuring signal.

Wheatstone bridges made of four sensor strips are known, but generally require complex conditioning methods.

In the following, XMR is a generic term for X-magnetoresistive effects, e.g. GMR (Giant Magnetoresistance), CMR (Colossal Magnetoresistance), AMR (Anisotropic Magnetoresistance) or TMR (Tunnel Magneto Resistance).

If previously XMR spinvalve sensors were used as Wheatstone bridges for field measurement (for position, speed, and speed sensors), considerable effort had to be made to condition or shield corresponding XMR elements.

In the conditioning of monolithically integrated field sensors, the reference layers of the individual sensor elements are through consuming processes in different Rich ^¬ obligations aligned. An example of such a process is shown in DE 100 28 640 B4. Alternatively, the orientation of the reference layer in different directions and two XMR elements can be shielded by a magnetic shielding against the action of äuße ^¬ ren magnetic field. This requires a comparatively thick, structured layer of low coercivity ferromagnetic material (eg, permalloy). The application of effective shielding is therefore associated with relatively high costs. Alternatively, the bridge may also carry a plurality of hybrid ge ^¬ twisted against each other individual chips, the XMR elements or half-bridges from XMR elements can be constructed. However, this can not be combined with the monolithic integration on an evaluation circuit.

The object of the invention is to provide a Wheatstone bridge with XMR sensors with little conditioning time to verwirk ^¬ union. The object is solved by the features of the independent claims.

Further developments of the invention are described in the dependent claims.

By irradiation with heavy ions (eg copper, iron, nickel, cobalt, tungsten, platinum, iridium, xenon, ruthenium) at low to medium energies of about 20 keV to 300 keV and high implantation doses in the range of 10 ¹⁴ to 10 ¹⁸ ions / cm 2, the respective XMR / GMR element will be so beschä ^¬ over, that it shows no significant XMR / GMR effects more. Are specifically two diagonally opposed bridge elements of the Wheatstone bridge so damaged, there remain two selected, diagonally opposite, magnetically aligned in parallel XMR / GMR bridge elements func tional, ^¬. This completes the conditioning. The conditioning is thus limited to the cost-effective Ion implantation of a variety of Wheatstone bridges on a wafer

The damage to the XMR / GMR bridge elements is mainly caused by two processes:

1. The first relevant process is the so-called mixing, ie mixing processes of the different substances at their respective interfaces as a result of radiation-induced decomposition of the atoms in the area of the interfaces.

2. The second process for damaging the GMR effect is the effect of the implanted ions themselves by reducing the mean free path of the conduction electrons in the copper interlayer. In particular, the targeted damage to the copper layer between the reference layer and the measurement ^¬ layer by the implantation of the elements ruthenium, iron, nickel, cobalt in the region of the copper layer proves to be very effective.

The number of dislocations upon bombardment with a 100 keV iron ion is maximum at a depth between 10 and 20 nm. Higher depths can be achieved for example by higher Accelerati ^¬ supply energies. For most top-pinned GMR Spinvalve sensors, the layers that are mainly damaged are 15-40 nm deep. As iron, cobalt, nickel, since they act comparatively strong scattering in copper on conduction electrons and accordingly increase the electrical resistance significantly even in low concentration.

During implantation, the XMR-bridge elements that are not to be deactivated by the radiation damage the ions, with an ion-impermeable layer, for example a photoresist layer with at least 50 nm thickness, above ^¬ geous enough, however, usually greater 300nm covered. As the base resistance can be increased by the implantation of ions in the XMR-layer must be in the layout, the strip width and the strip length of the two selected Brü ^¬ ckenelemente be adjusted accordingly, so that the four bridge elements have to complete processing and conditioning the same ohmic resistance ,

Advantageously, a monolithically integrable bridge structure with low conditioning effort is achieved in this system.

In the figures, further developments and various embodiments of the invention are shown.

Show it:

1 shows the layer structure of a first GMR Spinvalve magnetic field sensor in section,

FIG. 2 shows a plan view of the GMR spin-valve magnetic field sensor according to FIG. 1,

Figure 3 shows the diagram of a Wheatstone bridge with as XMR

Spinvalve magnetic field sensors formed bridge elements

In the figures, identical or corresponding Einhei ^¬ th have the same references. The figures are described in groups together.

FIGS. 1 and 2 show a layer system for a GMR spin-valve magnetic field sensor. Is shown in Figure 1, the layer structure, ie the cut strip by a measuring ^¬, and in Figure 2 the top view of such a sensor stripe.

The so-called "free layer" layers of nickel-iron (permalloy) are pinned with iridium-manganese, which is a natural antiferromagnet. In detail, in the figures 1, reference numeral 10 represents a seed layer (Ta) layer, for example, a 3.5nm thick Tan ^¬ tal having thereon 2nm located Ni-Fe layer 12 is formed. On top there is a reference layer 20, which in detail consists of, for example, 10 nm iridium-manganese (IrMn) layer 21, a 2.5 nm thick cobalt-iron (Fe) layer, a 0.8 nm ruthenium (Ru). Layer (Ru) and a 2.5nm thick cobalt-iron (CoFe) layer consists. For separation there is a 2 μm thick copper (Cu) layer thereon.

A nickel-iron (NiFe) layer followed by the copper layer with a thickness of 8 nm, for example, in the ERAL ^¬ NEN terminology "Free Layer" (free layer) is referred to. Free Layer on the layer 30, a pinning layer on the strength, for example lOnm is arranged insbeson ^¬ particular from iridium manganese (IrMn) consists. This is again in a known manner a passivation layer 50, which consists for example of a TaN layer of strength lOnm.

A GMR sensor according to FIGS. 1 and 2 is irradiated from above with a bombardment of ions 6 of an ion source 7 as described in more detail in FIG. The goal is to destroy the XMR effect that occurs through the quantum mechanical XMR effects in layers 30, 25, 24. The material and the energy of the Io ^¬ NEN 6 is selected so that the ions 6, the layers 50, 40, 30 substantially without or with little interaction penetrate and their in the layers 25, 24, 23

"destructive" effect by causing impurities 8 to mingle with the quantum effects crucial

Interfaces with each other and by implanting (sticking) of the interfering ions 6 in these layers 25, 24, 23, 22 unfold. The average penetration depth of the ions 6 is thus substantially between 28 nm-35, 9 nm. In alternative embodiments of GMR sensors, the layers relevant for the GMR effect lie in depths between 15 nm and 40 nm. FIG. 3 shows a Wheatstone bridge with bridging elements 1, 2, 3, 4, each consisting of a GMR or TMR spinvalve system. For example, the four bridge elements 1, 2, 3, 4 may each be ^¬ weils formed of a GMR spin valve system of Figures 1 and 2. FIG. Two bridge elements 1, 2 each; 3, 4 form a Halbbrü ^¬ blocks. The bridge elements 1, 2, 3, 4 are magnetized substantially pa ^¬ rallel, which is represented by the arrows with the Magnetisie ^¬ tion direction Ml, M2, M3, M4. The respective directions of magnetization M2, M4 of two selected, diagonally arranged bridge elements 2, 4, which lie in adjacent half bridges 1, 2 and 3, 4, are reduced or destroyed by bombardment of ions 6, which is represented by dashed arrows. By the bombardment of ions 6, the selected bridge elements 2, 4 have a reduced or completely destroyed GMR, or TMR effect. A supply voltage Ub supplies the Wheatsto ^¬ nebrücke 1, 2, 3, 4. A sensor voltage Us between the respective resistors of the bridge elements 1, 2 or 3, 4 of the two half-bridges 1, 2; 3, 4 can be tapped. When an external magnetic field H is applied, the resistances of the unselected bridge elements 1, 3 that are dependent on the external magnetic field H change, which can be measured by changing the sensor voltage Us. Many disruptive effects, such as changes in resistance due to temperature changes, are ideally largely eliminated by the structure of the Wheatstone bridge with four substantially identical bridge elements 1, 2, 3, 4. The Wheatstone bridge described above is as follows Herge provides ^¬:

On the two non-selected, diagonally arranged bridge elements 1, 3 is an ion-impermeable Layer 5 with a thickness D of at least 50 nm, ^{vorzugswei ¬} se with a thickness D of at least 300 nm applied. The layer 5 is formed for example as a photoresist. Now, the entire Wheatstone element according to FIG. 3 with all four bridge elements 1, 2, 3, 4 is inserted into an ion beam chamber. By irradiating the Wheatstone bridge with ions 6, the unselected bridge elements 1, 3 remain intact. By contrast, ions 6 are injected into the selected bridge elements 2, 4, which have their effect, above all, in the layers 25, 24, 23 relevant to the GMR effect, as a result of which stable impurities 8 are formed in the boundary layers of the active GMR layers to be damaged and the ions 6 in the highly electrically conductive GMR layer, for example, in Figure 1, the conductive Cu layer 25, are introduced. As a result, the conduction electrons of the highly conductive GMR layer 25 are strongly scattered, whereby the electric

(Basic) resistance of the bridge element increases. Since the basic resistance of each of the four bridge elements 1, 2, 3, 4 in the ground state should be equal to compensate for disturbances such as temperature drift, this increase in electrical resistance by layout measures of two diagonally opposite bridge elements 1, 3 or 2, 4 balanced in advance. This happens for example by the fact that the non-selected elements 2, 4 a shorter sensor length A2, A3 and / or a wider sensor width B2, B3, A3 having at Ver ^¬ equal to the widths Bl, B3 and lengths AI of the selected bridge elements 1, 3 ,

The ion impermeable layer 5 can maintain 6 or be removed by conventional mechanical, physika ^¬ metallic or chemical processes after the bombardment of ions.

Claims

claims

1. Wheatstone bridge with bridge-connected bridge elements (1, 2, 3, 4), which consist of a GMR or TMR Spinvalve system, wherein

each two bridge elements form a half-bridge (1, 2 and 3, 4),

- The bridge elements (1, 2, 3, 4) are magnetized substantially parallel,

- Two diagonally arranged bridge elements (2, 4), each in adjacent half-bridges (1, 2 and 3, 4), by bombardment of ions (6) have a reduced or destroyed GMR or TMR effect.

2. Wheatstone bridge according to claim 1, characterized in that the injected ions (6) in the respective bombarded with ions (6) bridge element (2, 4) cause a) stable impurities (8) in the boundary layers of the quantum mechanically active, GMR or TMR area, and

b) the ions (6) in the electrically highly conductive layer (25), in particular of copper (Cu), the active intermediate ^¬ layers, are introduced, whereby the conduction electrons are strongly scattered and the electrical resistance increases, in particular by implanting the ions iron (Fe), cobalt (Co), nickel (Ni).

3. Wheatstone bridge according to claim 1 or 2, characterized in that the ions (6) are heavy ions and, for example, copper (Cu), iron (Fe), nickel (Ni), cobalt (Co), tungsten (Wo) , Platinum (Pt), iridium (Ir), argon (Ar) xenon (Xe) or ruthenium (Ru).

4. Wheatstone bridge according to one of the preceding claims, characterized in that the GMR effect relevant and to be damaged layers (25, 24, 23) lie in depths between 15 nm and 40 nm.

5. Wheatstone bridge according to one of the preceding claims, characterized in that the strip width or the strip length preferably of two diagonally opposite bridge elements (1, 3, 2, 4) are adjusted so that the four bridge elements after complete processing and

Conditioning by bombardment with the ions (6) have the same ohmic resistance.

6. A method for producing a Wheatstone bridge according to one of the preceding claims, characterized in that a) all the bridge elements (1, 2, 3, 4) are magnetized substantially paral ^¬ lel b) the surface areas (AI, A3) of two diagonally to each other arranged bridge elements (1, 3) with an ion ^¬ impermeable layer (5) are covered, c) the Wheatstone bridge with the surface areas (AI, A2, A3, A4) of all bridge elements (1,2,3,4) with ions (6 ) of a predetermined energy and a predetermined dose (number of ions (6) per square centimeter), the ion-impermeable layer (5) shielding the appropriately selected bridge elements (1,3) from the radiation of the ions (6) is of the GMR or TMR effect not only with the ion impermeable layer (5) covered bridge elements (2,4) is substantially reduced or zer ^¬ interfere.

7. The method according to claim 6, characterized in that the ions (6) particle energies of about 20keV to 300keV and a dose of about 1014 to ^ ions (6) / cm2 have.

8. The method according to claim 6 or 7, characterized marked, that the ion-impermeable protective layer (5) before ^¬ given from photoresist and the thickness (D) of the protective layer (5) is between 50nm and lym, preferably over 300nm.

9. The method according to any one of the preceding method claims, characterized in that the ions (6) are heavy Io ^¬ NEN, and for example, copper (Cu), iron (Fe), Ni ^¬ ckel (Ni), cobalt (Co), tungsten ( Where), platinum (Pt), iridium (Ir), argon (Ar), xenon (Xe) or ruthenium (Ru).

10. Method according to one of the preceding method claims, characterized in that an injected ion (6) approximately between one hundred (100) and four hundred (400), preferably between two hundred (200) and three hundred (300) stable impurities (8) in the for the GMR effect relevant layers (25,24,23) produced.