Magnetoresistive sensor module with a structured metal sheet for illumination and method for manufacturing the same

In the method of manufacturing a magnetoresistive sensor module, at first a composite arrangement out of a semiconductor substrate and a metal-insulator arrangement is provided, wherein a semiconductor circuit arrangement is integrated adjacent to a main surface of the semiconductor substrate into the same, wherein the metal-insulator arrangement is arranged on the main surface of the semiconductor substrate and comprises a structured metal sheet and insulation material at least partially surrounding the structured metal sheet, wherein the structured metal sheet is electrically connected to the semiconductor circuit arrangement. Then, a magnetoresistive sensor structure is applied onto a surface of the insulation material of the composite arrangement, and finally an electrical connection between the magnetoresistive sensor structure and the structured metal sheet is established, so that the magnetoresistive sensor structure is connected to the integrated circuit arrangement.

PRIORITY

This application claims priority from German Patent Application No. 10 2005 008 368.4, which was filed on Feb. 23, 2005, and German Patent Application No. 10 2005 047 414.4, which was filed on Oct. 4, 2005, which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to magnetoresistive sensor modules and, in particular, to a procedure for manufacturing magnetoresistive sensor modules, preferably with a multiplicity of individual magnetoresistive sensor elements for the detection and evaluation of external magnetic fields.

BACKGROUND

Sensors converting magnetic or magnetically coded information to an electric signal play an ever-greater role in today's technology. They find application in all fields of technology in which the magnetic field may serve as an information carrier, i.e. in vehicle technology, mechanical engineering/robotics, medical technology, non-destructive materials testing, and in micro-system technology. With the aid of such sensors, a multiplicity of different mechanical parameters are sensed, such as position, velocity, angular position, rotational speed, acceleration, etc., but current flow, wear, or corrosion may also be measured.

For the sensing and evaluation of magnetic or magnetically coded information, magnetoresistive devices or sensor elements are increasingly employed in technology. Magnetoresistive devices, which may be arranged as single elements or also in form of a plurality of connected single elements, increasingly find application today in numerous applications for contactless position and/or movement detection of a giver object with reference to a sensor arrangement, particularly in automobile technology, such as for ABS systems, traction control systems, etc. For this purpose, rotation angle sensors on the basis of magnetoresistive elements or structures, which will generally be referred to as xMR structures in the following, are frequently used. In the following description, the term “xMR structure” shall include all known magnetoresistive structures, such as AMR (anisotropic magnetoresistance) structures, GMR (giant magnetoresistance) structures, CMR (colossal magnetoresistance) structures, TMR (tunnel magnetoresistance) structures, or EMR (extraordinary magnetoresistance) structures. In technical applications of GMR sensor arrangements, so-called spin valve structures are preferably used today, as illustrated inFIGS. 5a-c, for example.

In the following, it will now at first be briefly gone into GMR structures in general. GMR structures are almost always operated in a so-called CIP (current-in-plane) configuration, i.e. the applied current flows in parallel to the sheet structure. In the GMR structures, there are some basic types that have gained acceptance in practice. In practice, e.g. when employed in automobile technology, above all large temperature windows, for example from −40° C. to +150° C., and small field strengths of few kA/m are necessary for optimum and safe operation. The most important GMR structures for the practical employment are illustrated inFIGS. 5a-c.

The GMR structure illustrated inFIG. 5ashows the case of a coupled GMR system500, in which magnetic layers502,506, e.g. of cobalt (Co), are separated by a non-magnetic layer504, e.g. of copper (Cu). The thickness of the non-magnetic layer504is chosen so that antiferromagnetic coupling of the soft-magnetic layers502,506develops without a magnetic field applied. This is meant to be illustrated by the depicted arrows. An external field then forces the parallel orientation of the magnetization of the soft-magnetic layers502,506, whereby the resistance of the GMR structure decreases.

The GMR structure illustrated inFIG. 5bshows a spin valve system501, in which the non-magnetic layer504is chosen so thick that no more coupling of the soft-magnetic layers502,506develops. The lower magnetic layer506is strongly coupled to an antiferromagnetic layer508, so that it is magnetically hard (comparable with a permanent magnet). The upper magnetic layer502is soft magnetic and serves as measuring layer. It may be remagnetized by already a small external magnetic field M, whereby the resistance R changes.

In the following, it is now gone into the spin valve arrangement501illustrated inFIG. 5bin greater detail. Such a spin valve structure501consists of a soft-magnetic layer502, which is separated, by a non-magnetic layer504, from a second soft-magnetic layer506, the magnetization direction of which is, however, pinned by the coupling with an antiferromagnetic layer508by means of the so-called “exchange bias interaction”. The principle functioning of a spin valve structure may be illustrated by means of the magnetization and R(H) curve inFIG. 5b. The magnetization direction of the magnetic layer506is pinned in negative direction. If the external magnetic field M is increased from negative to positive values, the “free”, soft-magnetic layer502switches near the zero crossing (H=0), and the resistance R rises sharply. The resistance R then remains high until the external magnetic field M is great enough to overcome the exchange coupling between the soft-magnetic layer506and the antiferromagnetic layer508and to switch also the magnetic layer506.

The GMR structure illustrated inFIG. 5cdiffers from the GMR structure illustrated inFIG. 5bin that here the lower antiferromagnetic layer508is replaced by a combination of a natural antiferromagnet510and a synthetic antiferromagnet (SAF)506,507,509on top, consisting of the magnetic layer506, a ferromagnetic layer507, and a non-magnetic layer509in between. In this manner, the magnetization direction of the magnetic layer506is pinned. The upper, soft-magnetic layer502in turn serves as measuring layer, the magnetization direction of which may easily be rotated by an external magnetic field M. The advantage of the use of the combination of natural and synthetic antiferromagnets as compared to the construction according toFIG. 5bis the greater field and temperature stability.

In the following, it is now gone into so-called TMR structures in general. For TMR structures, the application spectrum is very similar to that of GMR structures.FIG. 6shows a typical TMR structure. The tunnel magnetoresistance TMR is obtained in tunnel contacts, in which two ferromagnetic electrodes602,606are decoupled by a thin, insulating tunnel barrier604. Electrons can tunnel through this thin barrier604between the two electrodes602,606. The tunnel magnetoresistance is based on the tunnel current being dependent on the relative orientation of the magnetization direction in the ferromagnetic electrodes.

The magnetoresistive structures (GMR/TMR) previously described thus have an electrical characteristic dependent on an applied magnetic field, i.e. the resistivity of an xMR structure of a magnetoresistive device is influenced by an influencing external magnetic field.

In bridge arrangement, rotation angle sensors on the basis of the GMR effect may provide an inherent 360° uniqueness of the magnetic field to be detected and have relatively high sensitivity with reference to the magnetic field to be detected.

In order to realize 360° detection by means of a magnetoresistive structure and particularly an GMR/TMR spin valve structure of a plurality of magnetoresistive devices, to detect the rotation direction of a wheel or a shaft with reference to the sensor arrangement, for example, eight magnetoresistive devices are connected with two Wheatstone bridge arrangements (connected in parallel), wherein one of the bridge circuits has reference magnetizations aligned perpendicularly to those of the other bridge circuit. Within each bridge circuit of four magnetoresistive devices, the reference magnetizations are arranged in antiparallel manner, so that both bridge circuits provide sinusoidal signals dependent on the rotation angle of an external magnetic field, which are 90° phase shifted with respect to each other. Via an arctan computation of both output signals, i.e. the output signal of the first and second bridge circuits, the angle over a 360° range can be uniquely determined.

The reference magnetizations of the individual elements of the GMR/TMR spin valve structure may have up to four locally different directions. For adjusting the reference direction, the spin valve layer system has to be heated above the so-called “blocking temperature” (depending on magnetoresistive material system employed) up to 400° C. and cooled again in a lateral magnetic field of the desired direction. This procedure is also referred to as conditioning the magnetoresistive structure. For manufacturing a magnetoresistive sensor structure, locally heating the respective individual elements is therefore required, without also heating neighboring magnetoresistive elements above the blocking temperature during the magnetization procedure. Here, one possibility is locally illuminating with a laser with sufficient radiation energy per unit area, for example.

InFIG. 7, a principle circuit diagram of a possible connection in form of a double bridge circuit700with eight magnetoresistive magnetic field sensor elements is illustrated. The double bridge arrangement700includes a first bridge circuit arrangement702and a second bridge circuit arrangement704, each out of four magnetoresistive individual elements702a-b,704a-b, the magnetizations of which are indicated with reference to the x-axis and y-axis illustrated inFIG. 7. The first bridge circuit702includes two magnetoresistive devices702awith permanent magnetization antiparallel to the x-axis indicated and two magnetoresistive devices702bwith permanent magnetization parallel to the x-axis. The double bridge circuit arrangement700further includes a second bridge circuit704, which comprises two magnetoresistive devices704awith permanent magnetization in the y direction and two magnetoresistive devices704bwith permanent magnetization antiparallel to the y direction each. The individual magnetoresistive devices702a,702b,704a,704bare connected, as indicted inFIG. 7, wherein the first and second bridge circuits702and704are connected to each other in parallel and further connected between a supply voltage and a ground potential.

During the operation of the magnetoresistive sensor arrangement700ofFIG. 7, the first bridge circuit702provides an output signal VXbetween the two center taps of the first bridge circuit, wherein the second bridge circuit704provides an output signal VYbetween the two center taps of the second magnetoresistive bridge circuit. The connection of the magnetoresistive devices702a,band704a,bdescribed with reference toFIG. 7allows for the detection of an external, rotating magnetic field over an angle range of 360°. The sinusoidal output signals VXand VYof the two bridge circuits connected in parallel are obtained as a function of the rotating, external magnetic field, wherein the two output signals VXand VYare phase shifted with reference to each other by an angle of 90° each.

GMR sensor elements are constructed such that meander-shaped GMR structures form the resistance elements, which are preferably connected in a bridge circuit. Meander-shaped structures are used to provide sufficiently long, magnetoresistive resistance elements, so that sufficiently high changes in resistance can be determined.

Manufacturing processes known in the prior art for GMR/TMR sensor elements include only the construction of a GMR/TMR sensor device and its contacting. Up to now, only GMR or TMR sensor structures in form of discrete devices are known. GMR/TMR sensor devices previously known in the prior art substantially are magnetoresistive resistance structures accommodated in normal SMD (surface mounted device) packages, wherein a GMR sensor device and its pin occupancy (terminal occupancy) are shown inFIG. 8a, for example. InFIG. 8b, the accompanying functional block diagram is illustrated in principle. The sensor device illustrated inFIG. 8ais to be coupled externally with an evaluating circuit (not shown inFIGS. 8a-b).

An electronic circuit externally associated with the GMR sensor device800is required to calibrate the sensor output signal (out+, out−), in order to obtain high absolute accuracy of a GMR sensor arrangement on the one hand. An electronic circuit is also required to condition the sensor output signal and also to provide the sensor output signal in a correspondingly processed, digital or analog interface for further evaluation. Such an additional electronic circuit has to be made available in form of a second device on a circuit board, for example.

According to the prior art, it is indeed also possible to accommodate the electronic circuit for evaluating or rendering the GMR sensor output signal on an additional semiconductor chip to the GMR sensor element within a device package, wherein the GMR sensor element and the semiconductor chip are connected to each other by means of bond wires, for example. But this procedure is problematic in that the necessary chip areas and the connection of both chips, i.e. of the GMR sensor element and the electronic evaluation and rendering circuit, generate corresponding, additional chip costs and assembly costs due to the greater package effort owing to the additional bondings between the GMR sensor element and the semiconductor chip. This additional package effort may also lead to increased parasitic influences, which may affect the sensor properties. Moreover, it should be noted that the final sensor application is limited to the package shapes customary in the market for reception and connection of two chips, i.e. the GMR sensor element and the electronic evaluating and rendering circuit.

SUMMARY

Starting from this prior art, it is an object of the present invention to provide a simplified procedure for manufacturing a magnetoresistive sensor arrangement, with which a magnetoresistive sensor module, which can be accommodated in space-saving manner, can be realized.

In accordance with a first aspect, the present invention provides a method of manufacturing a magnetoresistive sensor module, with the steps of: providing a composite arrangement out of a semiconductor substrate, wherein a semiconductor circuit arrangement is integrated adjacent to a main surface of the semiconductor substrate into the same, and a metal-insulator arrangement, wherein the metal-insulator arrangement is arranged on the main surface of the semiconductor substrate and has a structured metal sheet and insulation material at least partially surrounding the structured metal sheet, wherein the structured metal sheet is electrically connected to the semiconductor circuit arrangement, applying a magnetoresistive sensor structure onto a surface of the insulation material of the composite arrangement, and establishing an electrical connection between the magnetoresistive sensor structure and the structured metal sheet, so that the magnetoresistive sensor structure is connected to the integrated circuit arrangement.

In accordance with a second aspect, the present invention provides a magnetoresistive sensor module, having: a composite arrangement out of a semiconductor substrate, wherein a semiconductor circuit arrangement is integrated adjacent to a main surface of the semiconductor substrate into the same, and a metal-insulator arrangement, wherein the metal-insulator arrangement is arranged on the main surface of the semiconductor substrate and has a structured metal sheet and insulation material at least partially surrounding the structured metal sheet, wherein the structured metal sheet is electrically connected to the semiconductor circuit arrangement, and a magnetoresistive sensor structure, which is applied on a surface of the insulation material of the composite arrangement, wherein an electrical connection between the magnetoresistive sensor structure and the structured metal sheet is made, so that the magnetoresistive sensor structure is connected to the integrated circuit arrangement.

The inventive procedure for manufacturing a magnetoresistive sensor element includes the following steps. At first, a composite arrangement of a semiconductor substrate and a metal-insulator arrangement are provided. The semiconductor substrate has an active semiconductor circuit arrangement integrated in the semiconductor substrate adjacent to a main surface thereof. The metal-insulator arrangement is arranged on the main surface of the semiconductor substrate and comprises a structured metal sheet and insulating material at least partly surrounding the structured metal sheet, wherein the structured metal sheet is electrically connected to the semiconductor circuit arrangement.

A magnetoresistive structure is now applied on a surface of an exposed area of the insulation material of the composite arrangement, wherein also an electrical connection between the magnetoresistive structure and the structured metal sheet is made, so that the magnetoresistive structure is connected to the integrated circuit arrangement (via the structured metal sheet).

The magnetoresistive sensor module according to the invention includes a composite arrangement of a semiconductor substrate and a metal-insulator arrangement, wherein a semiconductor circuit arrangement is integrated in the semiconductor substrate adjacent to a main surface thereof. The metal-insulator arrangement is arranged on the main surface of the semiconductor substrate and comprises a structured metal sheet and insulation material at least partly surrounding the structured metal sheet, wherein the structured metal sheet is electrically connected to the semiconductor circuit arrangement. On a surface or an exposed area of the insulation material of the composite arrangement, now a magnetoresistive structure is applied, wherein this is electrically connected to the structured metal sheet, so that the magnetoresistive structure is electrically connected to the integrated circuit arrangement.

The present invention is based on the finding that a magnetoresistive sensor device and, in particular, a GMR/TMR sensor module may be obtained by expanding the manufacturing process for an integrated semiconductor circuit arrangement on a semiconductor substrate, such as a semiconductor wafer, in that, in addition to the integrated semiconductor circuit arrangements in the semiconductor substrate and a metal-insulator layer stack arranged on top, a magnetoresistive layer structure (xMR structure) is applied on an outwardly exposed area of the insulation material of the metal-insulator layer arrangement, wherein preferably vias are further provided both between the at least one structured metal sheet on the one hand to the integrated circuit arrangements on the semiconductor substrate and vias to pads of the magnetoresistive structure.

Preferably, an optional passivation layer, for example, of oxide or nitride material, for performing a protective function is now also applied on the magnetoresistive structure on the metal-insulator layer stack, wherein an additional passivation layer of photoimide material, for example, may be applied in addition, wherein highly positive properties with reference to accommodation in one package may be obtained with this.

Corresponding to the advantageous procedure for manufacturing a magnetoresistive sensor module according to the present invention, the xMR process module (for the magnetoresistive structure) is preferably placed between the last metal sheet of the basic manufacturing process and the passivation layer arrangement disposed thereon. For example, in case of a GMR sensor element, the GMR sensor element is now preferably connected to a metal sheet of the metal-insulator layer stack from underneath, wherein this is obtained by the use of a manufacturing process for an additive tungsten plug or a tungsten plug already present, for example. Via the connection to the metal sheet, an electrical connection of the magnetoresistive sensor element with the active semiconductor circuit arrangement on the semiconductor substrate is now also possible.

In the case of the contacting of a TMR sensor element, for example, an electrical connection of this sensor element with the active semiconductor circuit arrangement on the semiconductor substrate may be achieved by arranging an additive metal sheet above the TMR layer structure, for example with gold or with an alternative metal compound, which may be connected to the TMR layer structure via vias.

The inventive concept for manufacturing a magnetoresistive sensor module thus enables an arrangement, which is space saving with reference to the existing chip area, of the magnetoresistive sensor structure to be performed on active electronic devices, i.e. semiconductor circuit arrangements.

Thus, it is an advantage of the present invention that a magnetoresistive sensor device, and particularly a GMR or TMR sensor device, may be manufactured and integrated with the integrated electronic semiconductor devices within a semiconductor manufacturing process. Moreover, according to the inventive concept, adding the manufacturing process for the magnetoresistive sensor element to the basic semiconductor manufacturing process may now be done so that the integrated semiconductor devices obtained in the basic semiconductor manufacturing process remain substantially uninfluenced by the manufacturing steps of the magnetoresistive sensor element.

It is particularly advantageous in the inventive concept for manufacturing a magnetoresistive sensor module that the manufacturing process block for manufacturing the magnetoresistive sensor element may substantially be applied to all other semiconductor manufacturing processes and semiconductor circuit arrangements or applications in modular manner.

A technical realization of the manufacturing method according to the invention thus allows for the manufacture of magnetic field sensor modules in vertical integration by means of a metal layer stack with one or more metal layers and insulating layers there between. The metal layer stack is arranged above the active chip area in a dielectric, for example oxide material, wherein the permanently magnetizable magnetic field sensor structure is preferably arranged within a passivation layer, e.g. a plasma nitride layer. Furthermore, vias for connecting the magnetic field sensor structure to a metal layer of the metal layer stack are illustrated.

With reference to the present invention, it is to be noted that the metal layer stack with the xMR layer structure may be manufactured in substantially technology-independent manner. The metal layer stack with the xMR-layer structure may thus be integrated onto the chip passivation above the active chip area in vertical integration or without active circuit and without routing in horizontal integration.

The wiring of the xMR magnetic field sensor structure may take place above the xMR magnetic field sensor structure by introducing an additional metal plane or on a metal plane already present by the interconnects or vias. Below the xMR layer stack, on the metal layer, a metallic protection plate, for example, is allowed for, which on the one hand protects the underlying logic circuits in the active chip area from the laser light in a laser writing process and on the other hand balances the temperature gradients, which may exert a strong influence on the accuracy on the xMR magnetic field sensor structure by causing an offset signal.

The metal planes of the metal layer stack may themselves also be embodied as lightproof shields. In this, it is to be noted that the metal planes of the metal layer stack may be embodied as current conductor structures for contacting different sensor structure portions, for example, with certain parts of the integrated circuit arrangement (e.g. via vias). These individual current conductor structures, however, must not abut each other and hence are preferably separated from each other by an insulation layer. This insulation layer is, however, generally translucent. So as to not put the underlying active circuits in the semiconductor material at risk by incident laser light in the writing procedure, additional metal plates or also other opaque arrangements, which are disposed directly under the clearances or gaps in the metal layer plane (in the layout), should be introduced on one of the metal layers. According to the present invention, it is possible that a metal plane or also a combination of several metal planes forms the shield lightproof with reference to the laser light wavelengths used.

DETAILED DESCRIPTION

In the following, with reference toFIG. 1, a first embodiment according to the invention of a magnetoresistive sensor module and the corresponding method of manufacturing the same will now be explained in detail.

FIG. 1shows a schematic cross-sectional illustration through a magnetoresistive sensor module100according to a first embodiment of the present invention. The magnetoresistive sensor module100includes a semiconductor substrate102, e.g. of silicon and/or polysilicon material with a first main surface102a, wherein a semiconductor circuit arrangement104is integrated adjacent to the main surface102aof the semiconductor substrate102into the same. According to the present invention, the semiconductor circuit arrangement104integrated into the semiconductor substrate102may substantially be manufactured by means of arbitrary MOS and bipolar techniques or combinations of these techniques (BiCMOS processes), wherein the integrated circuit arrangement104may comprise both active devices, such as transistors, and passive devices, such as diodes, resistors, and capacitors.

With reference to the present invention, it is to be noted that the inventive concept is indeed exemplarily explained on the basis of a magnetoresistive module100, but with the inventive concept also being advantageously applicable to methods for the mass production of magnetoresistive sensor modules on wafer level with a multiplicity of magnetoresistive devices.

In the following, it is now exemplarily gone into a basic CMOS process. In a basic CMOS process, at first the p and n wells for the creation of the substrate areas of the n channel and p channel MOS transistors, respectively, are manufactured (well process module). What follows in the course of the process is the insulation of neighboring transistors by generating a so-called field oxide between the transistors. In the so-called active areas, i.e. the regions not covered by the field oxide, the MOS transistors then develop. With this, the front part of the overall process, which provides the transistors and their mutual insulation, is completed. It is also referred to as FEOL (front end of line). In the BEOL (back end of line) part, it is now about contacting and connecting the individual mono- or polycrystalline semiconductor areas (e.g. silicon areas) of the FEOL part according to the desired integrated circuit arrangement104. For the contacting and connection of the semiconductor areas, at least one metal sheet108ais required, as this is illustrated inFIG. 1, wherein often two or more metal sheets are also used, wherein it is spoken of a multi-sheet metallization in this case. The passivation supposed to protect the integrated circuit against mechanical damage due to environmental influences and against the intrusion of impurities then forms the conclusion of the overall process.

With progressive structural shrinkage with at the same time ever greater thickness of the overall layer construction, the leveling of surfaces with steep steps plays an ever greater role, so that leveling methods may be required also according to the present invention, in order to obtain as-plane-as-possible surfaces of the various levels, such as the metal sheet108aor the insulation layers108b, and thus the magnetoresistive structure110.

The magnetoresistive sensor module100illustrated inFIG. 1comprises an insulation layer106(ZOX=Zwischenoxid=intermediate oxide) above the semiconductor substrate and the semiconductor circuit arrangement104integrated therein, corresponding to conventional semiconductor manufacturing processes. The insulation layer106may for example have a thickness on the order of 0.1 and 2 μm, and preferably in a range of about 0.5 μm. On the insulation layer106, which preferably comprises oxide material, a metal-insulator arrangement108consisting of at least one metal sheet108aand an insulation layer108b(at least partially) surrounding this metal sheet108ais arranged.

A magnetoresistive sensor structure110is applied on the metal-insulator arrangement108on an (outwardly) exposed area of the insulation material108b. The thickness of the magnetoresistive sensor structures110ranges from about 2 to 200 μm, and preferably about 50 nm. In the scope of the present description, all xMR structures are understood as magnetoresistive structures or sensor structures, i.e. particularly AMR (anisotropic magnetoresistance) structures, GMR (giant magnetoresistance) structures, CMR (colossal magnetoresistance) structures, EMR (extraordinary magnetoresistance) structures, and TMR (tunnel magnetoresistance) structures, as well as magnetoresistance structures and spin valve structures. Here, it is to be noted that the above enumeration is not to be viewed as comprehensive, wherein substantially all magnetoresistive structures and elements can be employed with reference to the present invention.

As illustrated inFIG. 1, the metal sheet108ais preferably connected to connecting areas on the integrated semiconductor circuit arrangement104via vias112. Furthermore, electrically conductive vias112are arranged between the structured metal sheet108aand preferably connecting areas of the magnetoresistive sensor structure110, so that preferably an electrical connection of the magnetoresistive structure110with default connecting areas of the active circuit arrangement104can be made. In the following, it will still be gone into specific embodiments of the vias112in greater detail.

Furthermore, as shown inFIG. 1with reference to the magnetoresistive sensor module100illustrated there, a covering, completing cap layer arrangement114is optionally arranged on the metal-insulator arrangement108and the magnetoresistive sensor structure110arranged thereon.

As already indicated previously, the course of the process for the manufacture of the active and passive devices of the circuit arrangement104in the semiconductor substrate102is dealt with in the front part of the overall manufacturing process (FEOL=front end of line). In the BEOL (back end of line) part of the overall process, the individual devices are now connected to each other so that the desired magnetoresistive sensor module100is obtained.

Although diffused regions as well polysilicon or polycide traces may be utilized intensively for the electrical connection of the various devices of the integrated circuit arrangement104in integrated circuits, only low-ohmic metallic metal structures, such as the metal sheet108a, are referred to as conductive traces in the following description. Although aluminum is presently still prevalent as material for conductive trace structures, tungsten is extremely advantageous at via diameters below about 0.5 μm due to its leveling function. Moreover, however, copper also increasingly finds industrial application, which is more lowly ohmic and current loadable than aluminum. With reference to the present invention, however, substantially all sufficiently low-ohmic and current-loadable metals, such as also TiN, may be used as starting material for the structured metal sheet108a.

In order to protect the magnetoresistive sensor module100illustrated inFIG. 1according to the invention with the integrated circuit arrangement104, the metal sheet108a, and the magnetoresistive sensor structure110against corrosion and mechanical damage, after the structuring or after the structured application of the magnetoresistive sensor structure110, a passivation layer arrangement114may optionally be applied, which is opened only at those locations at which optional connecting wires (bond wires; not shown inFIG. 1) can be attached at pads (not shown inFIG. 1). The passivation layer arrangement114may for example consist of an oxide, e.g. plasma oxide, or a nitride, e.g. plasma nitride, each with a layer thickness of about 0.1 to 5 μm, and preferably from about 0.5 to 1 μm. But double layers of oxide and/or nitride materials with the above layer thicknesses are also possible.

The metal sheets preferably have a thickness of about 0.1 to 2.5 μm, and preferably from about 0.35 to 0.55 μm.

The procedure for manufacturing a magnetoresistive sensor module according to the present invention may thus be summarized as follows. The basic process of the basic semiconductor manufacturing process is performed until the manufacture of the metal sheet108a. Annealing the device present until then may take place with an anneal procedure (if required). The magnetoresistive sensor structure110is now structuredly applied on an exposed area of the insulation layer108b. The insulation layer108bthus serves for electrical insulation of the magnetoresistive sensor structure from the metal sheet108a, wherein the insulation layer108bmay, if required, be planarized for creating a defined and planar surface for the magnetoresistive sensor structure110. For this, so-called CMP (chemical mechanical polishing) methods or corresponding planarization methods may be employed, for example.

For contacting the magnetoresistive sensor structure, the metal sheet108aof the basic process (i.e. prior to applying the magnetoresistive sensor structure110) is now provided with vias112through the insulation layer108b, wherein the vias are filled with metal, e.g. tungsten, and the surface is planarized flush with the insulation layer108b. Then, the magnetoresistive sensor structure is applied and structured. Of course, it is also possible that the magnetoresistive sensor structure is applied in already structured manner. Optionally, then the passivation layer arrangement114is applied, wherein here a further anneal procedure may additionally take place, which should, however, be compatible with the magnetoresistive sensor structure already applied. Finally, now optional contact pads may be opened on the metal sheet108or also on the magnetoresistive sensor structure110with a standard process of the basic semiconductor manufacturing process.

In above anneal procedures, temperatures from 150 to 350° C. may be used.

In the following, with reference toFIG. 2, a further embodiment of an inventive magnetoresistive sensor module200according to the present invention will now be explained. For simplification of the following description, inFIG. 2, functionally like functional elements have the same reference numerals as inFIG. 1, wherein repeated description of these features is omitted. Furthermore, all above statements with reference to the functional elements illustrated inFIG. 1are equally applicable to the corresponding functional elements inFIG. 2.

As can be seen in the magnetoresistive sensor module200illustrated inFIG. 2, this exemplarily comprises five metal sheets108a-1to180a-5, further designated with M1-M5. Furthermore, the additional passivation layer116is illustrated inFIG. 2. Furthermore, an opening118for an optional bond wire120with a bond contact is illustrated inFIG. 2.

The above statements explained inFIG. 1thus are substantially also applicable to the magnetoresistive sensor module200according to the invention illustrated inFIG. 2.

In the magnetoresistive sensor module illustrated inFIG. 2, the basic process of the basic semiconductor manufacturing process is also processed until the last metal sheet108a-5(M5), wherein at this point also an anneal procedure may be performed. So that the magnetoresistive sensor structure110to be applied later can be electrically insulated, on the last metal sheet108a-5, an insulation layer108b-5(at least partially) surrounding it is further applied. It is to be noted that the first four metal sheets108a-1to108a-4also comprise (at least partially) surrounding insulation areas108b-1to108b-4.

For example, if the topmost insulation layer108b-5has manufacture-induced uneven spots and should thus be planarized in order to create a defined and planar surface for the magnetoresistive sensor structure110still to be applied, a CMP treatment of the surface of the insulation layer108b-5can also be performed here. For contacting the magnetoresistive sensor structure still to be applied, the last metal sheet108a-5of the basic process is provided with vias112through the insulation layer108b-5, wherein the created vias are filled with metal, e.g. tungsten, and the surfaces thereof are preferably planarized flush with the surface of the topmost insulation layer108b-5. Then, the magnetoresistive sensor structure110is applied and structured. Finally, a suitable passivation arrangement114,116is optionally applied, which for example comprises an oxide/nitride passivation layer114and an additional passivation layer116of photoimide material. At this time, an additional anneal procedure may also take place here, which should, however, be compatible with the magnetoresistive sensor structure already applied. Finally, so-called connecting pads122are opened with the standard process of the basic manufacturing process, so that the magnetoresistive sensor module200according to the invention illustrated inFIG. 2may be connected to a lead frame (not shown inFIG. 2) of a device package by means of optional bond wires120, for example.

In the following, with reference toFIG. 3, a further embodiment of an inventive magnetoresistive sensor module300according to the present invention will now be explained. For simplification of the following description, functionally like functional elements inFIG. 3have the same reference numerals as inFIGS. 1or2, wherein repeated description of these features is omitted. Furthermore, all above statements with reference to the functional elements illustrated inFIGS. 1or2are equally applicable to the corresponding functional elements inFIG. 3.

As can be seen fromFIG. 3, the magnetoresistive sensor module300illustrated there comprises a metal sheet302with an insulation layer304(at least partially) surrounding it. This metal sheet302is disposed opposite the first metal sheet108awith reference to the magnetoresistive sensor structure110, so that the magnetoresistive sensor structure110may be regarded as between the metal sheets108aand302. It should, however, become clear that, corresponding to the embodiment of the inventive magnetoresistive sensor module200ofFIG. 2, a substantially arbitrary number of metal sheets108a, i.e. at least one metal sheet, may also be arranged here on the semiconductor substrate102and below the magnetoresistive sensor element110. Furthermore, of course several metal sheets302may also be disposed above the magnetoresistive sensor structure110and also be structured, in order to form conductor structures, for example, if this is required.

In the present description, the terms “above” or “below” are to be referred to directions “in” the drawing plane ofFIGS. 1-3.

The arrangement of the inventive magnetoresistive sensor module300illustrated inFIG. 3obviously is especially advantageous for TMR sensor structure, since there the current direction may flow perpendicularly through the magnetoresistive structures. Thereby, a simplified electrical connection and coupling of the magnetoresistive sensor structure110may be achieved. However, it should also become clear that substantially all under the term “magnetoresistive sensor structures” can be electrically contacted with the additional metallization sheet302by means of additional vias112.

In the embodiment illustrated inFIG. 3, it is thus only required to provide a further insulation layer304and also the additional metal sheet302in the manufacturing process after applying the magnetoresistive structure110. On this arrangement, optionally a passivation arrangement or an additional passivation arrangement (not shown inFIG. 3) may now also be applied again, as already illustrated on the basis ofFIGS. 1 and 2. Furthermore, the optional passivation arrangement or additional passivation arrangement may be opened to expose connecting contacts122for optional contacting, for example, by means of bond wires on the additional metal sheet302.

From the embodiments of the inventive magnetoresistive sensor modules100,200and300illustrated on the basis ofFIGS. 1,2and3and the accompanying manufacturing methods, it becomes clear that the inventive concept for manufacturing an magnetoresistive sensor module according to the invention may be integrated into a conventional semiconductor manufacturing process of an integrated semiconductor circuit, wherein the magnetoresistive sensor structure may here either be placed between the last metal sheet of the basic manufacturing process and the passivation or may also be placed between two arbitrary neighboring metal sheets. The contacting of the magnetoresistive sensor structure may be achieved from underneath (with reference to the magnetoresistive sensor structure in direction of the semiconductor substrate) by the use of a standard inter-metal contact process (i.e. e.g. W plugs). Furthermore, contacting the magnetoresistive sensor element110may be obtained from above either by an additional metal layer302(cf.FIG. 3) or by an additional metal contact (via). The latter procedure is therefore particularly suited for TMR sensor structures.

Moreover, the inventive procedure for manufacturing a magnetoresistive sensor module is advantageous in that a surface planarized with a CMP procedure and conditioned correspondingly, for example, is used as starting point and growth foundation for the magnetoresistive sensor structure, which is preferably embodied as an xMR layer stack. With this, according to the present invention, a magnetoresistive sensor module integrated with an active circuit arrangement can be obtained.

Since mechanical tension differences in the various layers in the inventive magnetoresistive sensor modules100,200,300illustrated inFIGS. 1,2, and3often cannot be avoided, insufficient sealing adhesion or tensions of the package molding compound may lead to cracks in the metallization layer (metal sheet108a) and, if several metal sheets108aare provided, above all in the topmost metallization layer as well as in the passivation layer arrangement114. In order to remedy this problem, the passivation layer thickness will preferably be as great as possible, i.e. preferably greater than the thickness of the metal sheet108a(or the topmost metal sheet108a). Furthermore, relatively wide metal trace structures are slotted. Furthermore, it should be avoided that conductive traces are provided in the area of the outer chip corners. An additional polyimide layer, which may have a thickness of 0.5 to 10 μm and preferably from about to 1 to 5 μm, for example, has turned out to be especially effective. This additional passivation layer (not shown inFIG. 1) preferably is as a so-called stress relief and furthermore provides for excellent adhesion between the molding compound and the chip surface in an accommodation of the inventive magnetoresistive sensor module in a package.

In the following, with reference toFIG. 4, a further embodiment of an inventive magnetoresistive sensor module400according to the present invention will now be explained. For simplification of the following description, functionally like functional elements inFIG. 4have the same reference numerals as inFIGS. 1-3, wherein repeated description of these features is omitted. Furthermore, all above statements with reference to the functional elements illustrated inFIGS. 1-3are equally applicable to the corresponding functional elements inFIG. 4.

For the detection of an angle unique in 360°, GMR/TMR spin valve structures require several magnetoresistive individual elements, which are arranged in a Wheatstone bridge circuit, for example, and the reference magnetization of which may comprise up to four locally different directions. For adjustment of the respective reference direction of each magnetoresistive individual element, the spin valve layer system now has to be heated above the so-called “blocking temperature”, which is up to 400° C. depending on the material system employed, and cooled again in a lateral magnetic field of the desired direction. For manufacturing a magnetoresistive sensor module in which all magnetoresistive sensor elements or sensor structures (e.g. bridge elements) are integrated on a chip, locally heating the respective elements is therefore required, without also heating neighboring elements above the “blocking temperature” during the magnetization procedure. For example, one possibility is locally illuminating with a laser light source with sufficient energy.

As it becomes obvious from the above statements on the embodiments ofFIGS. 1,2and3, for cost and performance reasons, it is advantageous to “vertically” integrate the magnetoresistive sensor structure together with the electronic evaluating/control circuitry on the semiconductor circuit substrate. For highest compatibility with the fabrication process, it is now required to enable also vertical integration, i.e. position the magnetoresistive sensor structures above the integrated electronic semiconductor circuit arrangements, as well as to implement a partly necessary additional passivation with a photosensitive polyimide. The polyimide material often is a very important constituent to noticeably improve the adhesion between the package and the chip surface. The photoimide material typically is between 2.5 μm and 6 μm thick. In order to obtain fabrication-suited yield, the electronic semiconductor circuit elements underlying the magnetoresistive structures must not be affected by the laser irradiation on the one hand, wherein the launched laser power should not scatter significantly across the semiconductor substrate (wafer) and also from wafer to wafer by layer thickness variations of the layers between the magnetoresistive structures and the laser, for example, on the other hand.

A further aspect of the present invention consists in using a metal sheet of the metal/insulator arrangement108of a magnetoresistive sensor module100,200,300fromFIGS. 1,2, and3, respectively, for protecting the sensitive areas of the substrate material104from inadvertent influence of the radiation from a laser light source in the conditioning. One of the metal sheets may be embodied as lightproof shield so that the proportion of the radiation emitted from the light source not absorbed by the magnetoresistive structure110is shielded, so that inadvertent illumination of a sensitive area of the substrate material104lying in the extension of the optical train and potential damage of devices or circuit elements resulting there from is prevented.

FIG. 4shows a schematic illustration of a top view onto a device according to a further embodiment of the present invention, whereinFIG. 4only shows a metal sheet108a, which includes the areas402to408galvanically separated in the plane of the metal sheet108a, and a magnetoresistive structure or GMR area110, which substantially has a meander structure. Here, the metal sheet108a, also referred to as M5inFIG. 4may match particularly the fifth metal sheet108a-5fromFIG. 2.

The metal plane108amay here at the same time be used as lightproof shield and as feeding structure for the magnetoresistive structure110. In this case, however, recesses, which prevent shorting the magnetoresistive structure110via the metal plane108a, have to be provided in the metal plane108a.FIG. 4exemplarily shows two such recesses in the metal sheet108a, which are designated with SAand SB. In the embodiment shown inFIG. 4, the area404and the area406of the metal sheet108aserve as connecting areas for the magnetoresistive structure110, which is also referred to as GMR inFIG. 4.

Between the area404or406and the magnetoresistive structure110, there is a metallic connection (via112; cf.FIGS. 1-3) passing substantially perpendicularly to the main surface of the substrate material and not shown inFIG. 4for perspective reasons. The areas404and406of the metal sheet108a, together with the areas402and408, form a lightproof shield for sensitive areas of the substrate material, which lie in the further course of the optical train of the radiation emitted from the light source in the step of heating the magnetoresistive structure110. Here, the metal sheet108aincludes at least a metal not transparent in the wavelength region of the radiation used, so that the radiation emitted by the light source and not absorbed by the magnetoresistive structure110is reflected or absorbed by the metal sheet108a.

Here, the metal sheet108a, apart from the function as lightproof shield, additionally fulfills the task to prevent additional heating of sensitive areas in the substrate material in the surroundings of the magnetoresistive structure by distributing the heat to a greater area of the composite arrangement due to the in general substantially better thermal conductivity of metals as compared with semiconducting or insulating materials. Hereby, the metal sheet108athus not only acts as a lightproof shield, but also as a heat barrier preventing or weakening the expansion of the heat deposited in the magnetoresistive structure110via thermal conduction to sensitive areas of the substrate material.

So that the metal plane108acan be used as a lightproof shield and as a signal plane at the same time, in the present embodiment for contacting the magnetoresistive structure110, like in the embodiment shown inFIG. 4, the metal sheet must have recesses to prevent shorting of the magnetoresistive structure110, as this has already been explained further above. In order to prevent the radiation emitted in the step of conditioning the magnetoresistive structure110from reaching sensitive areas of the substrate material lying in the further course of the optical train, the magnetoresistive structure110may comprise, apart from the actual meander structure of the magnetoresistive structure, such structures that cover the necessary recesses or gaps in the metal sheet108ain the extension of the optical train of the radiation emitted from the light source.

FIG. 4thus exemplarily shows a gap or a recess SAin the metal sheet108a, which galvanically separates the areas404and408of the metal sheet108afrom each other. AsFIG. 4also shows on the basis of the gap labeled SB, in the plane of the magnetoresistive structure and taking the optical train of the radiation emitted from the light source into account, a gap in the metal sheet108amay be filled by magnetoresistive material or by a magnetoresistive layer system so that the plane of the magnetoresistive structure110forms a lightproof shield together with the metal sheet108a.

In summary, it may thus be stated thatFIG. 4schematically shows an embodiment of the inventive lightproof shield below a magnetoresistive or GMR meander structure, in which the shielding and the wiring of the magnetoresistive or GMR structure take place in the same metal plane108aor M5.FIG. 1shows the corresponding lightproof shield below the GMR structure in cross section. In the embodiment shown inFIG. 4, the optical shield is embodied in the last metal plane108a1-5of a five metal sheet process. With simultaneous use of the fifth or last metal plane108a1-5for the contacting of the magnetoresistive structure110for the GMR/TMR wiring, the layout of the metal sheet108a1-5, however, has to be chosen so as to have no “gaps” for the laser light preferably incident perpendicularly.FIG. 4shows for this case that a gap SAhas to be provided between the wiring area404and the shield area408, in order to avoid shorting of the magnetoresistive structure or the GMR terminals. For optical shading of the underlying devices or a sensible area of the substrate material, this gap area SAcan be filled with GMR material or a magnetoresistive layer system, as this is exemplarily shown at the gap designated as SB, without significantly influencing the sensor properties of the magnetoresistive structure.

According to the present invention, thus an individual metal plane or also a combination of several metal planes may form the shield lightproof with reference to the conditioning radiation used, so that as much radiation energy as possible is kept away from the sensitive semiconductor substrate. Here, at least so much radiation energy should be shielded that no (e.g. thermal) impairment or damage of the circuit arrangements integrated in the semiconductor substrate can occur.

With reference to the inventive concept for manufacturing a magnetoresistive sensor module, it now also becomes clear that the inventive implementation may be achieved in a CMOS/BiCMOS-compatible manufacturing fabrication procedure for attaining fabrication-suited local laser conditioning of integrated magnetoresistive sensor elements and particularly GMR and TMR sensor elements with high yield, because the structured metal sheets of the metal-insulator arrangement, i.e. the metal layer stack above the semiconductor circuit substrate, may provide a lightproof shield below the magnetoresistive structure by the fact that the metal planes underlying the magnetoresistive sensor structure are embodied or structured corresponding to the irradiation angle of the laser irradiation (preferably a perpendicular incident angle) so that inadvertent illumination of the semiconductor circuit areas lying below the magnetoresistive sensor structures on the integrated semiconductor circuit substrate and its possible damage due to the laser irradiation can be prevented.

The inventive concept for manufacturing a magnetoresistive sensor module thus offers a series of advantages.

The method for integration of a magnetoresistive sensor structure with an active semiconductor circuit arrangement may thus be built into every basic semiconductor manufacturing process with slight adaptations. The applied magnetoresistive sensor structure is disposed on a surface that is planar and to be conditioned independently of the basic semiconductor manufacturing process. With this, the ideally planar contact area between magnetoresistive sensor structure and contact pads allows for an extremely robust and reliable contacting of the magnetoresistive sensor structure, i.e. the xMR layer systems. Problems like tear-offs, thinning, etc. can be avoided according to the invention. Furthermore, the active sensor layer, i.e. the magnetoresistive sensor structure110, is not changed by an etching process from above.

Due to the small thickness of the magnetoresistive sensor structures in the range from about 2 to 200 μm, and preferably about 50 μm, the final passivation with the passivation arrangement114and/or the additional passivation layer116is further disposed on a largely planar surface and thus is tight in a large process window. Optionally, it is also possible that the last inter-metal connections (via) of the basic semiconductor manufacturing process are used as a sensor terminal, i.e. as a terminal of the magnetoresistive sensor structure.

Moreover, in the inventive manufacturing method of a magnetoresistive sensor module, the final anneal procedure for the integrated process, i.e. the basic semiconductor manufacturing process, and for the magnetoresistive sensor module may take place independently, so that particularly the anneal process that can be performed at lower temperature for the sensor module may be performed later, without damaging the other integrated circuit parts, and the anneal procedure taking place at high temperatures for the remaining integration may conversely be performed prior to the creation of the sensor module, so that no impairment or destruction of the sensor module occurs.

Thus, it becomes clear that substantially only standard semiconductor manufacturing processes are required for the inventive method of manufacturing a magnetoresistive sensor module. The resulting magnetoresistive sensor module may be put on the active integrated semiconductor circuit in space-saving manner, wherein this is referred to as vertical integration in this connection.

Furthermore, at least one of the previously described metal sheets may be embodied below the magnetoresistive sensor structure as a lightproof shield, so that inadvertent illumination of the active circuit areas, underlying the magnetoresistive sensor structure, of the semiconductor circuit arrangement in the semiconductor substrate and its possible damage may thereby be prevented. With this, according to the invention, fabrication-suited local laser conditioning of integrated magnetoresistive sensor modules may be implemented with high yield in a CMOS/BiCMOS-compatible fabrication flow.