Magnetic multi-turn sensor and method of manufacture

Abstract

To provide a magnetic multi-turn sensor comprising a continuous coil of magnetoresistive elements and a method of manufacturing the sensor.SOLUTION: The continuous coil is formed on a substrate such as a silicon wafer that has been fabricated to form a trench and bridge arrangement that enables the inner and outer spirals to be connected without interfering with the magnetoresistive elements of the spiral winding in between. Once the substrate has been fabricated with the trench and bridge arrangement, a film of the magnetoresistive material can be deposited to form a continuous coil on the surface of the substrate, where a portion of the coil is formed in the trench and a portion of the coil is formed on the bridge.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 075453, filed September 8, 2020, the contents of which are incorporated by reference in their entirety herein.

[0002] The present disclosure relates to a magnetic multi-rotation sensor, and more particularly to a closed-loop magnetic multi-rotation sensor and a method of manufacture. [Background technology]

[0003] Magnetic multi-turn sensors are commonly used in applications where the number of times a device is turned needs to be monitored. An example is a vehicle steering wheel. Magnetic multi-turn sensors typically contain a magnetoresistive element that is sensitive to an applied external magnetic field. The resistance of the magnetoresistive element can be changed by rotating the magnetic field within the vicinity of the sensor. The variation in the resistance of the magnetoresistive element can be tracked to determine the number of turns within the magnetic field, which can be translated into the number of turns within the device being monitored.

[0004] Magnetic multi-turn sensors typically comprise multiple magnetoresistive elements laid out as strips in a spiral or closed-loop configuration. One advantage of closed-loop multi-turn sensors is that they effectively provide a large number of spirals connected together, thus allowing a very large number of turns to be counted. Summary of the Invention [Means for solving the problem]

[0005] The present disclosure provides a magnetic multi-turn sensor including a continuous coil of magnetoresistive elements and a method of manufacturing the sensor. The continuous coil is formed on a substrate, such as a silicon wafer, that is fabricated to form a trench and bridge arrangement that allows an inner spiral and an outer spiral to be connected without interfering with the magnetoresistive elements of the spiral winding therebetween. Once the substrate is fabricated with the trench and bridge arrangement, a film of magnetoresistive material can be deposited to form the continuous coil on the surface of the substrate, with a portion of the coil formed in the trench and a portion of the coil formed on the bridge.

[0006] A first aspect provides a magnetic multi-rotation sensor comprising a plurality of magnetoresistive sensor elements connected in series and arranged in a continuous spiral configuration, and a substrate in which the plurality of magnetoresistive elements are formed, the substrate comprising a trench configured to receive at least one magnetoresistive element, and at least one bridge formed over the trench, the at least one bridge configured to support the at least one magnetoresistive element.

[0007] The trench may be configured to receive a number of magnetoresistance elements defining one side of a continuous spiral, and the substrate includes a bridge configured to receive one magnetoresistance element connecting the inner and outer loops of the spiral.

[0008] The trench may be configured to receive one magnetoresistance element connecting the inner and outer loops of the spiral, and the substrate includes at least one bridge formed over the trench to receive a plurality of magnetoresistance elements defining one side of the spiral.

[0009] The substrate may include a plurality of bridges formed over the trenches to receive a plurality of magnetoresistance elements defining one side of the spiral, each bridge receiving one magnetoresistance element.

[0010] The magnetoresistance element may be one of a giant magnetoresistance (GMR) element and a tunneling magnetoresistance (TMR) element.

[0011] The substrate may include a wafer layer, an intermediate layer formed on the wafer layer, and a mask layer formed on the intermediate layer.

[0012] The trench may be formed by removing a portion of the intermediate layer and a portion of the mask layer.

[0013] The bridge may be formed by preserving a portion of the mask layer over the trench.

[0014] The wafer layer may comprise one of a silicon layer, a glass layer, or a sapphire layer.

[0015] The intermediate layer may comprise one of an oxide layer, a nitride layer, and an oxynitride layer.

[0016] The mask layer may comprise an epi-silicon layer.

[0017] The mask layer may comprise a hard mask layer for selective etching.

[0018] The mask layer may comprise one of a silicon oxide layer, a silicon oxynitride layer, and a silicon nitride layer.

[0019] A further aspect provides a method of manufacturing a closed-loop magnetic multi-rotation sensor, the method including forming a substrate comprising a wafer, an intermediate layer, and a mask layer; etching regions of the mask layer and the intermediate layer to form trenches in the substrate, where one or more portions of the mask layer are preserved to form at least one bridge over the trench; and depositing a magnetoresistive film on the substrate to form a continuous spiral of magnetoresistive elements, where at least one magnetoresistive element is formed in the trench.

[0020] At least one magnetoresistive element may then be formed on the at least one bridge.

[0021] A plurality of magnetoresistance elements may be formed in the trench to define one side of the spiral, with at least one magnetoresistance element formed on at least one bridge connecting the inner and outer loops of the spiral.

[0022] Alternatively, multiple magnetoresistance elements may be formed on at least one bridge to define one side of the spiral, with at least one magnetoresistance element formed in the trench connecting the inner and outer loops of the spiral.

[0023] Etching regions of the mask layer and the intermediate layer may further include forming ramps in the mask layer and the intermediate layer at each end of the trench.

[0024] Etching the areas of the mask layer and the intermediate layer may include lithographic etching.

[0025] Depositing the magnetoresistive film may include using a tilt and rotate deposition system.

[0026] The method may further include etching the magnetoresistive film to form a magnetoresistive element.

[0027] Ion beam etching or angled reactive ion (RIE) etching may be used to form at least one magnetoresistance element in the trench.

[0028] In some cases, the wafer layer comprises a glass layer or a sapphire layer, in which case depositing the magnetoresistive film may include depositing a layer of photoresist material, depositing a layer of magnetoresistive film, and directing ultraviolet light from beneath the substrate to lift off one or more portions of the photoresist material and the magnetoresistive film.

[0029] The intermediate layer may comprise one of an oxide layer, a nitride layer, and an oxynitride layer.

[0030] The mask layer may comprise an epi-silicon layer.

[0031] The mask layer may comprise a hard mask layer for selective etching. For example, the hard mask layer may comprise one of a silicon oxide layer, a silicon oxynitride layer, and a silicon nitride layer.

[0032] In such cases, a selective etchant is applied to etch areas of the intermediate layer under areas of the hard mask layer to form at least one bridge. For example, the selective etchant may include one of potassium hydroxide (KOH), ethylenediaminepyrocatechol (EDP), or tetramethylammonium hydroxide (TMAH).

[0033] Another arrangement described herein provides a magnetic multi-rotation sensor comprising a plurality of magnetoresistive sensor elements connected in series and arranged in a continuous spiral configuration, and a substrate on which the plurality of magnetoresistive elements are formed, the substrate comprising at least one bridge formed over a first portion of the magnetoresistive elements, the at least one bridge being configured to support at least one magnetoresistive element.

[0034] The bridge may be formed from a strip of magnetic material over the first portion of the magnetoresistive element, and the magnetic material may be a soft ferromagnetic material, for example, a soft magnetic material including one of nickel, iron, or cobalt, or an alloy containing at least one of nickel, iron, or cobalt.

[0035] The first portion of the magnetoresistive elements may be a plurality of magnetoresistive elements defining one side of a continuous spiral, and the bridge is configured to receive one magnetoresistive element connecting the inner and outer loops of the spiral.

[0036] The present disclosure will now be described, by way of example only, with reference to the accompanying drawings. [Brief description of the drawings]

[0037] [Figure 1] 1 illustrates a magnetic multi-rotation sensor according to one embodiment of the present disclosure. [Diagram 2] 1 further illustrates a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Diagram 3] 13 further illustrates a magnetic multi-rotation sensor according to a further embodiment of the present disclosure; [Figure 4A] 1A-1C are schematic side views illustrating a method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Figure 4B] 1A-1C are schematic side views illustrating a method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Figure 4C] 1A-1C are schematic side views illustrating a method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Figure 4D] 1A-1C are schematic side views illustrating a method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Diagram 5] 1 shows a magnetic multi-rotation sensor according to a further embodiment of the present disclosure. [Figure 6] FIG. 2 is a diagram illustrating electrical connections of a magnetic multi-rotation sensor according to one embodiment of the present disclosure. [Figure 7] 1 illustrates a method for connecting magnetoresistive sensing elements of a multi-rotation sensor according to one embodiment of the present disclosure. [Figure 8A] 13 illustrates a further method of connecting magnetoresistive sensing elements of a multi-rotation sensor according to an embodiment of the present disclosure. [Figure 8B] 13 illustrates a further method of connecting magnetoresistive sensing elements of a multi-rotation sensor according to an embodiment of the present disclosure. [Figure 9A]A method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure is further illustrated. [Figure 9B] A method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure is further illustrated. [Figure 10A] 1 illustrates a further method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Figure 10B] 1 illustrates a further method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Figure 10C] 1 illustrates a further method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Figure 10D] 1 illustrates a further method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Figure 11A] 1 illustrates a further method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Figure 11B] 1 illustrates a further method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Figure 11C] 1 illustrates a further method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Figure 11D] 1 illustrates a further method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Figure 12] 1 illustrates a method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure. [Figure 13] 1 illustrates a portion of a magnetic multi-rotation sensor according to one embodiment of the present disclosure. [Figure 14] 13 illustrates a portion of a magnetic multi-rotation sensor according to a further embodiment of the present disclosure. [Figure 15A] A method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure is further illustrated. [Figure 15B] A method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure is further illustrated. [Figure 16A] A method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure is further illustrated. [Figure 16B] A method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure is further illustrated. [Figure 17A] A method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure is further illustrated. [Figure 17B] A method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure is further illustrated. [Figure 18A] A method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure is further illustrated. [Figure 18B] A method of manufacturing a magnetic multi-rotation sensor according to an embodiment of the present disclosure is further illustrated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Magnetic multi-turn sensors can be used to monitor the revolution count of a rotating shaft. To do this, a magnet is typically attached to the end of the rotating shaft, and the multi-turn sensor is sensitive to the rotation of the magnetic field as the magnet rotates with the shaft. Such magnetic sensing can be applied to a variety of different applications, such as automotive applications, medical applications, industrial control applications, consumer applications, and many other applications that utilize information about the position of rotating parts.

[0039] Magnetic multi-turn sensors typically include giant magnetoresistance (GMR) or tunnel magnetoresistance (TMR) elements that are sensitive to an applied external magnetic field, arranged in a spiral or closed loop configuration. As the external magnetic field rotates, domain walls propagate through the spirals, thereby changing the magnetic alignment of each magnetoresistance element as it passes. The resistance of the magnetoresistance elements changes as the magnetic alignment changes, and the resistance variations are tracked to determine the number of turns of the magnetic field. One of the main advantages of closed-loop sensors is that they effectively provide a large number of spirals connected together, thus allowing a very large number of turns to be counted. However, there are many challenges in the fabrication of such sensors, as the magnetoresistance film is thin, so it can be difficult to connect the inner and outer spirals, and connecting wires that cross the remainder of the spiral can break the domain walls, leading to non-propagation and corrupted turn counts.

[0040] The present disclosure provides a magnetic multi-turn sensor with a continuous coil of magnetoresistive elements and a method of manufacturing the same that allows for connecting an inner spiral and an outer spiral without interfering with the magnetoresistive elements in between. The continuous coil is formed on a substrate, such as a silicon wafer, that is fabricated to form a trench and bridge arrangement that provides a shielded crossing above or below the spiral. Once the substrate is fabricated with the trench and bridge arrangement, a film of magnetoresistive material can be deposited to form a continuous coil on the surface of the substrate. In so doing, a multi-turn sensor with a continuous coil is provided that can measure a large number of revolutions using no or very little power. The non-volatile nature of the magnetic domain position, i.e., the pattern in which the magnetoresistive elements change magnetic domains as the domain walls propagate through the spiral, allows the multi-turn sensor to count the number of revolutions in an external magnetic field without power. As the magnetic field rotates, the magnetic domains of each of the magnetoresistive elements change in a specific pattern, which provides a corresponding pattern of resistance measured across the multi-turn sensor. Thus, power can be applied when a readout is required, and the measured resistance at that point corresponds to a specific point in the pattern, i.e., a specific number of revolutions.

[0041] 1 and 2 show a multi-rotation sensor 1 according to one embodiment of the present disclosure. The sensor 1 comprises a substrate 10, e.g., a silicon-based substrate having a surface 11, in which a trench 12 is formed in one area of ​​the substrate surface 11 by etching the substrate surface 11, as shown in more detail in FIG. 2. The trench 12 is formed such that a portion of the substrate surface 11 is preserved to form a bridge 14 over the trench 12. A film of magnetoresistive material can then be deposited on the substrate 10 to form a magnetoresistive track 16 arranged in a spiral configuration having a number of segments arranged in series with one another. Each arm of the spiral thus provides a magnetoresistive sensing element capable of changing resistance in response to a change in magnetic alignment state in the presence of an externally applied magnetic field. The magnetoresistive track 16, which defines one side 15 of the spiral, is arranged to pass through the trench 12 and under the bridge 14. At each end of the trench 12 , a ramp 13 A, 13 B may be provided to provide a smooth path from the bottom of the trench 12 to the upper substrate surface 11 and to allow the magnetoresistive track 16 to enter and exit the trench 12 .

[0042] To form the bridge 14, the trench 12, and the ramps 13A, 13B leading into and out of the trench 12, the substrate 10 may be etched using a multi-step lithographic etching process. For example, there may be a first lithographic exposure and etch for the body of the trench 12, a second lithographic exposure and etch for the ramps 13A and 13B of the trench 12, and a third lithographic exposure and etch for the planar surface 11 surrounding the trench 12 and the bridge 14.

[0043] The outer spiral winding 17 passes around the outer periphery of the trench 12 and is connected to the inner spiral winding 19 via a connecting magnetoresistive track 18 deposited on the bridge 14. This bridge 14 and trench 12 arrangement thus allows the connecting magnetoresistive track 18 to cross one side 15 of the spiral without impeding the domain propagation of the magnetoresistive track on that side 15. Preferably the connecting magnetoresistive track 18 is a magnetoresistive track that contributes to the revolution counting of the multi-turn sensor, however it will be understood that in other arrangements the connecting part may comprise some other soft ferromagnetic material.

[0044] In an alternative arrangement, as shown in FIG. 3, the sensor 2 comprises a narrow trench 22 formed in the substrate 20, providing a crossing for a connecting magnetoresistive track 28 from the inner spiral winding to the outer spiral winding, and one or more bridges 24 formed over the narrow trench 22 supporting the magnetoresistive track 25 on that side of the spiral. That is, the magnetoresistive track 25 of the spiral crosses over the connecting magnetoresistive track 28. In the example of FIG. 3, one wide bridge 24 is formed supporting all of the magnetoresistive tracks 25 forming one side of the spiral. In other arrangements, several individual bridges may be formed over the narrow trenches 22, each supporting a single magnetoresistive track 25. As mentioned above, the trench 22 and bridge 24 arrangement may be formed by etching the substrate 20.

[0045] 4A-D show a first stage in a method of fabricating a multi-rotation sensor according to an embodiment of the present disclosure. As shown in FIG. 4A, a substrate is fabricated by first growing or depositing an intermediate layer 202, preferably an oxide layer, on a silicon wafer 200. However, it will be understood that the wafer 200 may be formed from a UV-transparent material such as glass or sapphire, in which case the oxide layer 202 is deposited thereon. The oxide layer 202 may also be a layer of nitride, oxynitride, or similar material. A mask layer 204, e.g., epi-silicon or similar material, is then deposited on the oxide layer 202. The thickness of the mask layer 204 depends at least in part on the thickness of the bridge 24.

[0046] Next, as shown in FIG. 4B, a photoresist layer 206 is formed on the substrate to etch a trench 208, as shown in FIG. 4C, and the oxide layer 202 is removed to deepen the trench 208 to a certain depth. As shown in FIG. 4D, a portion of the mask layer 204 is preserved to form a bridge 210 over the trench 208. The trench 208 and the bridge 210 may also be etched using stepwise lithographic etching. For example, a first lithographic exposure and etching for the body of the trench 208, a second lithographic exposure and etching for the ramps of the trench 208 (i.e., ramps 13A and 13B in FIGS. 1-3), and a third lithographic exposure and etching for the planar surfaces surrounding the trench 208 (i.e., top surface 11 and bridge 14 in FIGS. 1-3).

[0047] The manner in which the trenches are formed is further illustrated by Figures 9A-B. As shown in Figure 9A, the substrate includes a wafer 900 formed of silicon with Miller indices of (100), or a UV-transparent material such as glass or sapphire. An oxide layer 902 is formed on the wafer 200, followed by a mask layer 904 formed of epi-silicon or the like. As previously described, a resist 906 is deposited on the substrate, and a pattern 908 is formed on the resist to expose what will become the trenches and define the bridges. The mask layer 904 and oxide layer 902 are then etched to form trenches 910 and bridges 912, as shown in Figure 9B. Although a single narrow bridge 912 with a wide trench 910 is shown, it will of course be understood that by using an appropriate pattern in the resist, any suitable number and size of bridges and trenches may be formed.

[0048] If an ultraviolet-transparent material such as glass or sapphire is used for the substrate, a lift-off process may be used to form the magnetoresistive tracks in the trenches and on the bridges, as shown in Figures 10A-10D. In the exposed trench portion, a photoresist material 1002 may be sprayed onto the transparent substrate 1000, as shown in Figure 10A. Then, a layer of magnetoresistive material 1004 is deposited on the substrate 1000 and the photoresist material 1002, as shown by Figure 10B. Then, a lift-off process and resist removal is performed, as shown in Figures 10C and 10D, whereby ultraviolet light from below and above the substrate 1000 is used to remove the photoresist material 1002 and lift off a portion of the magnetoresistive material 1004, and the remaining magnetoresistive material 1004 forms the tracks of the multi-turn sensor.

[0049] An alternative method of forming the bridge and trench arrangement is to use a bulk micromachining approach, where the bridge is formed by a hard mask layer and selective etching. In such a case, the substrate (i.e., silicon wafer 200 and oxide layer 202) is provided with a hard mask layer, such as a silicon oxide layer, silicon oxynitride, and silicon nitride, that is inert to the etchant (e.g., potassium hydroxide (KOH), ethylenediaminepyrocatechol (EDP), or tetramethylammonium hydroxide (TMAH)) used to form the trench. Using a selective etchant that attacks the oxide layer 202 but not the mask layer allows the formation of a trench under the bridge.

[0050] During this process, special attention must be paid to the orientation of the bridge relative to the crystallographic directions of the substrate. The bridge must be tilted relative to the {110} planes because the {111} planes act as natural etch stops. An "n" isotropic etch can then be used to smooth the sidewall profile and flatten the bottom of the trench. Another option is to tilt the substrate underneath the bridge to orient the trench at an angle relative to the {110} planes, so that the {111} planes have a different orientation toward the trench opening.

[0051] An example of this bulk micromachining approach is shown in Figures 11A-11D. As shown in Figure 11A, a wafer 1100 and an oxide layer 1102 are provided. The wafer 1100 is formed of silicon with Miller indices of (110) and has a long edge of <112> The short side is aligned in the direction <111> At this point, <112> The direction is <110> It is 54.74° from the plane, creating a ramp with a perpendicular side on the long side and a 35.3° ramp on the short side.

[0052] As shown in FIG. 11B, a masking layer 1104 formed from an oxide or nitride (such as those mentioned above) is formed on the oxide layer 1102. Then, as shown in FIG. 11C, an etchant (such as a KOH etchant) is used to etch trenches 1106 and bridges 1108, the depth of the trenches 1106 depending on the time in the etchant. In some cases, as shown in FIG. 11D, the bridges 1108 may need to be formed at an angle due to the etchant leaving facets under the bridges 1108. By tilting the masking layer 1104, which allows an undercut to form the bridges 1108, the portion of the wafer 1100 at the bridges 1108 has walls that are sloped at an angle of, for example, 35 degrees. This also facilitates access to the area directly under the bridges 1108, thereby facilitating uniform deposition of the magnetoresistive material in the trenches 1106. Similarly, the masking layer 1104 in the area of ​​the trench 1106 may also be sloped to form sloped walls of the trench 1106, which may again be at an angle of 35 degrees. However, it will be appreciated that the sloped walls of the trench 1106 and bridge 1108 may be at any suitable angle.

[0053] The width of the trench 208 and bridge 210 depends at least in part on the number of magnetoresistance tracks formed along the trench. If the trench 208 receives one side of the spiral, as shown in Figures 1-3, then the width of the trench 208 depends at least in part on how many windings the spiral has and the spacing between each set of tracks, while the bridge 210 may be wide enough to support the tracks connecting the inner and outer spiral windings. If the trench 208 is positioned to receive a track connecting the inner and outer spiral windings, the trench 208 may be wide enough to receive one track. In such a case, as shown in Figure 14, one bridge 1404 formed over the trench 1402 is wide enough to receive all the tracks 1408 on that side of the spiral, while the trench 1402 is wide enough to receive the connecting track 1406. Alternatively, as shown in Figure 13, several bridges 1304 may be formed to receive each track 1308 individually.

[0054] In either case, the bridge 210 should be as narrow as possible to limit the amount of shadowing, while the trench 208 is preferably as wide as possible to reduce shadowing effects. For example, for a magnetoresistive track 350 nm wide, a bridge 210 of around 3 μm and a trench of around 29 μm may be provided. Similarly, if there are multiple tracks running alongside each other, along a trench or across one or more bridges, the tracks should be spaced an appropriate distance apart so as not to interfere with each other.

[0055] The depth of the trenches 208 should also be selected to minimize the amount of shadowing while at the same time allowing the magnetoresistive tracks to easily move in and out of the trenches 208 .

[0056] It will be appreciated that other suitable fabrication methods may be used to etch the trench and bridge arrangement. For example, the ramps on either end of the trench may be formed using a "bird's beak" as a fabrication process. Similarly, microlenses may be used in lithographic exposures to etch the trench under the bridge.

[0057] Once the substrate has been formed with the trench and bridge arrangement, a film of magnetoresistive material may be deposited on the substrate and etched to form the magnetoresistive tracks 16 shown in Figures 1-3.

[0058] The thickness of the magnetoresistive track affects its operating behavior in the field strength window where an externally applied magnetic field, e.g. a resistor, changes the magnetic alignment. It is therefore important that the magnetoresistive film is deposited uniformly to provide a track of uniform thickness, thereby avoiding errors in the rotation count. To deposit the film in a uniform layer under the bridge, angled physical vapor deposition can be used, where the sputtering system is titled at an angle and the substrate is rotated. Figure 12 shows a cross section of a wafer 1200 with a bridge 1204 and a trench 1206 formed therein and a substrate comprising an oxide layer 1202. A film 1208 is deposited on the bridge 1204 and in the trench 1206 such that a track of uniform thickness is formed. This is done by tilting the sputtering system at different angles depending on the target area. For example, a 90° angle to the wafer 1200 may be used to deposit the film 1208 on the bridge 1204, and a minimum angle is then used to deposit the film 1208 directly under the bridge 1204 in the area indicated by 1210. Using the same angle for all regions means a thinner film on the ramp portion of trench 1206, with potential pinning sites or discontinuities in region 12010. Thus, the tilt angle can be selected such that the film is deposited uniformly under the bridges, without any shadowing caused by the bridges and trench walls.

[0059] In some arrangements, the angled deposition may be performed on the free layer of the magnetoresistive film. In some arrangements, the angled deposition may be performed only on the free layer of the magnetoresistive film, i.e., the ferromagnetic material that has a magnetization that is free to change direction and thereby provide a change in resistance when an external magnetic field rotates. It is therefore important that this portion of the film is uniform to ensure consistent readings, as it is the magnetization of this portion of the magnetoresistive stack that is being measured.

[0060] Once the film is uniformly deposited, it is etched to form the tracks, for example using ion beam etching or reactive ion etching. For the portion under the bridge, the reactive ion etching may be done at an angle to again etch the film in a uniform manner. Of course, it will be appreciated that any suitable angle may be used depending on the depth of the trench and the thickness of the bridge. Similarly, it will be appreciated that other methods of etching the tracks may also be used.

[0061] In some cases, once the magnetoresistive film is deposited in the trench and etched to provide the magnetoresistive track of the sensor spiral, the trench may be filled with a polyimide material which may help provide mechanical robustness to the structure during any subsequent processing steps.

[0062] Figures 15A-B through 18A-B further show how the magnetoresistive tracks are formed when the bridge 1504 is configured to receive a magnetoresistive track 1508 on one side of the spiral, while the trench 1502 is positioned to receive a single track 1506 connecting the inner and outer spiral windings.

[0063] The first stage in the method is shown in Figures 15A and 15B, where Figure 15B shows a cross-sectional view of Figure 15A looking down the length of the trench 1502 perpendicular to axis A. First, magnetoresistive material is blanket deposited on top of the substrate 1500, so that magnetoresistive material is deposited on the bridge 1504 and along the trench 1502. A lithographic pattern is then used to etch multiple tracks 1508 along the bridge 1504 and a single track 1506 along the trench 1502. The trench 1502 is formed to be the same width as the target width of the magnetoresistive track 1506, and therefore there is no need to define the width of the track 1506 during the lithographic etch. However, regions of magnetoresistive material 1510 may be left on the sidewalls of the trench 1502.

[0064] To address this, the width of trench 1502 in the region of bridge 1504 is increased, as shown in Figures 16A and 16B. Again, Figure 16B shows a cross-sectional view of Figure 16A looking down the length of trench 1502. The overlapping region of magnetoresistive material 1510 may then be removed using some suitable method, for example using eco-snow cleaning techniques or ion beam etching, thereby providing a single magnetoresistive track 1506 running along the length of the trench, as shown in Figures 17A-17B and 18A-18B.

[0065] 5 provides an alternative embodiment of the present disclosure in which no trench is formed in the substrate, but a bridge 52, e.g., a permalloy strip or bridge formed using any of the methods described herein, is formed over the magnetoresistive track 58 of the spiral to connect the inner and outer spiral windings 54, 56. In such an arrangement, the bridge 52 may be formed from a soft magnetic material, preferably a soft ferromagnetic material, including one of nickel, iron, or cobalt, or an alloy containing at least one of nickel, iron, or cobalt.

[0066] Figures 6 to 8B show how the magnetoresistive tracks may be connected. Figure 6 shows a magnetic multi-turn sensor 4 similar to that described with reference to Figures 1 to 3, comprising a plurality of magnetoresistive tracks arranged in a spiral. The inner magnetoresistive track (corresponding to resistance R15) is connected to the outer magnetoresistive track (corresponding to resistance R16) via a connecting magnetoresistive track (corresponding to resistance R1) that crosses the spiral via a trench and bridge arrangement 40, as described above. The spiral includes a plurality of metallic contacts 42 along the spiral which may be provided via deposition of metallic material to define a plurality of magnetoresistive sensing elements R1 to R16, which may be connected to a power supply to enable their resistance to be measured.

[0067] For example, the magnetoresistance elements R1-R6 may be connected in a Wheatstone bridge arrangement, as shown in Figure 7. Alternatively, as shown in Figures 8A and 8B, the magnetoresistance elements R1-R6 may be connected in a matrix arrangement, with the lines indicated at 80 indicating the path of the spiral itself, as described in more detail in German Patent Application Publication No. DE102017104551A1 and US Patent Application Publication No. 2017 / 261345, the contents of which are incorporated herein by reference in their entirety.

[0068] Purpose

[0069] Any of the principles and advantages discussed herein may be applied to other systems, not limited to the systems described above. Some embodiments may include a subset of the features and / or advantages described herein. Elements and acts of the various embodiments described above may be combined to provide further embodiments. The acts of the methods described herein may be performed in any order as desired. Furthermore, the actions of the methods described herein may be performed serially or in parallel as desired. Although the circuits are shown in a particular arrangement, other equivalent arrangements are possible.

[0070] Any of the principles and advantages discussed herein may be implemented in connection with any other system, apparatus, or method that may benefit from any of the teachings herein. For example, any of the principles and advantages described herein may be implemented in connection with any device that has a need to correct rotational angular position data that originates from a rotating magnetic field. Additionally, the device may include any magnetoresistance or Hall effect device that is capable of sensing a magnetic field.

[0071] Aspects of the present disclosure may be implemented in a variety of electronic devices or systems. For example, phase correction methods and sensors implemented according to any of the principles and advantages described herein may be included in a variety of electronic devices and / or applications. Examples of electronic devices and applications include, but are not limited to, servos, robotics, aircraft, submarines, toothbrushes, biomedical sensing devices, and parts of consumer electronic products such as semiconductor die and / or package modules, electronic test equipment, and the like. Electronic devices may include unfinished products, including those for industrial, automotive, and / or medical applications.

[0072] Unless the context clearly requires otherwise, throughout the description and claims, words such as "comprising," "comprising," "including," and the like should be interpreted in an inclusive sense, i.e., "including, but not limited to," and not in an exclusive or exhaustive sense. As generally used herein, the words "coupled" or "connected" refer to two or more elements that may be directly connected or connected via one or more intermediate elements. Thus, the various schematic diagrams shown in the figures depict example arrangements of elements and components, but additional intervening elements, devices, features, or components may be present in an actual embodiment (assuming the functionality of the depicted circuit is not adversely affected). As used herein, the word "based on" is generally intended to encompass "based only on" and "based at least in part on." Together, when used in this application, the words "herein," "on," "under," and words of similar meaning refer to this application as a whole, and not to any particular portion of this application. Where the context permits, words in the Detailed Description using the singular or plural can also include the plural or singular, respectively. The word "or" referring to a list of two or more items is intended to cover all interpretations of the following word, i.e., any item in the list, every item in the list, and combinations of items in the list. All numerical values ​​or distances provided herein are intended to include similar values ​​within the measurement error.

[0073] Although specific embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the present disclosure. Indeed, the novel apparatus, systems, and methods described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions, and changes in the form of the methods and systems described herein may be made without departing from the spirit of the present disclosure. [Explanation of symbols]

[0074] 1 Multi-turn sensor 2 Sensors 10 Substrate 11 Board surface 12. Trench 13A, 13B Lamps 14 Bridge 15 Side 16 Magnetic Resistance Tracks 17 Outer spiral winding 18 connected magnetoresistive tracks 19 Inner spiral winding 20 Substrate 22 Trench 24 Bridge 25 Magnetic Resistance Tracks 28 connected magnetic resistance tracks 40 Bridge arrangement 42 Metal Contacts 52 Bridge 54, 56 Spiral winding 58 Magnetic Resistance Tracks 200 silicon wafers 202 Intermediate layer, oxide layer 204 Mask Layer 206 Photoresist layer 208 Trench 210 Bridge 900 wafers 902 Oxide layer 904 Mask Layer 906 Resist 908 Patterns 910 Trench 912 Bridge 1000 Transparent Substrate 1002 Photoresist materials 1004 Magnetoresistive materials 1100 Wafer 1102 Oxide layer 1104 Masking Layer 1106 Trench 1108 Bridge 1200 wafers 1204 Bridge 1206 Trench 1208 Membrane 1304 Bridge 1308 Trucks 1402 Trench 1404 Bridge 1406 Connecting Tracks 1408 Trucks 1500 boards 1502 Trench 1504 Bridge 1508 Magnetic Resistance Track

Claims

1. A magnetic multi-rotation sensor, a plurality of magnetoresistive sensor elements connected in series and arranged in a continuous spiral configuration; A substrate on which the plurality of magnetoresistive elements are formed, a trench configured to receive at least one magnetoresistive element; and a substrate comprising at least one bridge formed over the trench, the at least one bridge configured to support at least one magnetoresistance element.

2. 2. The magnetic multi-rotation sensor of claim 1, wherein the trench is configured to receive a plurality of magnetoresistance elements defining one side of the continuous spiral configuration, and the substrate includes a bridge configured to receive a magnetoresistance element connecting an inner loop and an outer loop of the continuous spiral configuration.

3. 2. The magnetic multi-rotation sensor of claim 1, wherein the trench is configured to receive one magnetoresistance element connecting inner and outer loops of the continuous spiral configuration, and the substrate includes the at least one bridge formed over the trench to receive a plurality of magnetoresistance elements defining one side of the continuous spiral configuration.

4. 2. The magnetic multi-rotation sensor of claim 1, wherein the substrate comprises a plurality of bridges formed over the trenches to receive a plurality of magnetoresistance elements defining one side of the continuous spiral configuration, each bridge receiving one magnetoresistance element.

5. 5. The magnetic multi-rotation sensor according to claim 1, wherein the plurality of magnetoresistance elements are one of giant magnetoresistance (GMR) elements or tunnel magnetoresistance (TMR) elements.

6. 1. A method of manufacturing a closed loop magnetic multi-rotation sensor, comprising: forming a substrate comprising a wafer, an intermediate layer, and a mask layer; etching regions of the mask layer and intermediate layer to form a trench in the substrate, wherein one or more portions of the mask layer are preserved to form at least one bridge over the trench; depositing a magnetoresistive film on the substrate to form a continuous spiral of magnetoresistive elements, at least one magnetoresistive element being formed in the trench.

7. The method of claim 6 , wherein the at least one magnetoresistive element is then formed on the at least one bridge.

8. 8. The method of claim 6 or 7, wherein a plurality of magnetoresistance elements are formed in the trench to define one side of the spiral, and the at least one magnetoresistance element formed on the at least one bridge connects an inner loop and an outer loop of the spiral.

9. 8. The method of claim 6 or 7, wherein a plurality of magnetoresistance elements are formed on the at least one bridge to define one side of the spiral, and the at least one magnetoresistance element formed in the trench connects an inner loop and an outer loop of the spiral.

10. 8. The method of claim 6 or 7, wherein etching areas of the mask layer and intermediate layer further comprises forming ramps in the mask layer and intermediate layer at each end of the trench.

11. The method of claim 6 or 7, wherein etching the mask layer and the intermediate layer regions comprises lithographic etching.

12. The method of claim 6 or 7, wherein depositing the magnetoresistive film comprises using a tilt and rotate deposition system.

13. The method of claim 6 or 7, further comprising etching the magnetoresistive film to form the magnetoresistive element.

14. The method of claim 13 , wherein ion beam etching or angled reactive ion (RIE) etching is used to form the at least one magnetoresistance element in the trench.

15. The wafer comprises a glass or sapphire layer, and depositing the magnetoresistive film comprises: depositing a layer of photoresist material; depositing a layer of magnetoresistive film; and directing ultraviolet light from beneath the substrate to lift off one or more portions of the photoresist material and the magnetoresistive film.

16. The method of claim 6 or 7, wherein the intermediate layer comprises one of an oxide layer, a nitride layer, and an oxynitride layer.

17. The method of claim 6 or 7, wherein the mask layer comprises an epi-silicon layer.

18. The method of claim 6 or 7, wherein the mask layer comprises a hard mask layer for selective etching.

19. 20. The method of claim 18, wherein a selective etchant is applied to etch areas of the intermediate layer below areas of the hard mask layer.

20. 20. The method of claim 19, wherein the selective etchant comprises one of potassium hydroxide (KOH), ethylenediaminepyrocatechol (EDP), or tetramethylammonium hydroxide (TMAH).

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