WO2013014321A2

WO2013014321A2 - Methods and systems for mems cmos devices including a multiwire compass

Info

Publication number: WO2013014321A2
Application number: PCT/ES2012/070569
Authority: WO
Inventors: Josep MONTANYÀ SILVESTRE; Juan José VALLE FRAGA; Laura BARRACHINA SARALEGUI
Original assignee: Baolab Microsystems Sl
Priority date: 2011-07-25
Filing date: 2012-07-25
Publication date: 2013-01-31
Also published as: WO2013014321A8; TW201319604A; WO2013014321A3

Abstract

The systems and methods described provide for a magnetometer device that includes a resonating element having an inner wire enclosed in a shielding electrode. The shielding electrode decreases the effect of interference on the resonating element. A sensing electrode is disposed proximate to the resonating element. The device further includes a source for generating current that is connected to the resonating element. The current when applied through the inner wire causes a displacement of the resonating element. The magnetometer device measures a magnetic field of the resonating element as a capacitance variation between the shielding electrode and the sensing electrode. The systems and methods herein provide for an accelerometer device that includes a resonating element having an inner core of dielectric material enclosed in a shielding electrode. The accelerometer device measures an acceleration of the resonating element as a capacitance variation between the shielding electrode and the sensing electrode.

Description

METHODS AND SYSTEMS FOR MEMS DEVICES (SYSTEMS

MICROELECTROMECHANICAL) CMOS (SEMICONDUCTOR

COMPLEMENTARY OF METAL OXIDE) INCLUDING A MULTIDEL COMPASS THREAD

Cross Reference to Related Requests

This application claims priority over the provisional US patent application. No. 61 / 511,324 filed on July 25, 2011, the provisional US patent application. No. 61 / 606,091 filed on March 2, 2012, and the provisional US patent application. No. 61 / 646,664 filed on May 14, 2012, which are incorporated by reference herein in their entirety.

Background

Motion sensor devices such as magnetometers and accelerometers are typically embedded in today's electronic devices. In one aspect, such devices are typically manufactured using a MEMS-based micro-electromechanical process and include an anchored test mass. Any movement of the test mass causes a capacitance variation with respect to a reference electrode, and the variation is measured to determine the target vector, such as a magnetic field or acceleration.

However, the anchored test mass is typically susceptible to interference from the environment such as electromagnetic or electrostatic dispersion fields or other effects such as those. The interference may affect the sensitivity of the motion sensor device that has the test mass and makes it unsuitable for high sensitivity applications, for example, magnetic resonance imaging (MRI). The reduced sensitivity results in a lower signal-to-noise ratio (SNR) and can make measurements made using the motion sensor device inaccurate.

Therefore, there is a need for a motion sensor device that is minimally susceptible to interference and offers a high SNR.

Summary The systems and methods described herein address deficiencies in the prior art by allowing the manufacture of a motion sensor device, whether based on MEMS, based on NEMS or based on CMOS MEMS, which is minimally susceptible to interference In the case of a magnetometer device in which an objective magnetic field to be measured is larger than the earth's magnetic field (approximately 60 μΤ), the sensitivity needs of the magnetometer device is generally low. However, if the target magnetic field to be measured is small, for example, in the vicinity or lower than the geomagnetic noise (approximately 0.1 nT), a high sensitivity magnetometer device may be necessary. Such magnetometer devices are typically needed in medical and biomedical applications, such as MRI and molecule labeling, and radio communications, such as a receiving antenna for RF signals.

The systems and methods described herein are provided for a magnetometer device that includes a resonant element having an inner wire enclosed in a protective electrode. The protective electrode can decrease unwanted effects of interference on the resonant element and improve the SNR of the magnetometer device. The protective electrode that encloses the inner wire It can also allow an easier measurement of the capacitance variation between the resonant element and a sensitive electrode. A constant voltage can be applied to the protective electrode with respect to the sensitive electrode such that the capacitance variation is not affected by any voltage drop in the inner wire. Without the protective electrode, the voltage drop due to current flow and the resistance of the inner wire can induce electrostatic force and / or electrostatic interference. These can interfere with the capacitance variation and introduce errors in the measurement of a target magnetic field. In one aspect, the systems and methods described herein are provided for a magnetometer device. A sensitive electrode is disposed within the magnetometer device, and a resonant element is disposed close to the sensitive electrode. The resonant element includes a protective electrode arranged around an inner wire. The device also includes a source for generating current that is connected to the resonant element. The current, when applied through the inner wire, causes a displacement of the resonant element perpendicular to the magnetic field. The magnetometer device measures a magnetic field of the resonant element as a variation of capacitance between the protective electrode and the sensitive electrode.

In some embodiments, the device further includes a plurality of resonant elements arranged close to the resonant element present, and a plurality of guide wires arranged close to the resonant elements. The guide wires electrically connect the resonant elements such that the same current propagates through all the resonant elements. In some embodiments, the current applied to the resonant element is periodic.

In some embodiments, the device includes a voltage source connected to the protective electrode that applies a constant voltage to the protective electrode. In some embodiments, two or more resonant elements are mechanically coupled with such that they share a resonant frequency. The mechanical coupling of the resonant elements may include physically connecting their respective protective electrode with conductive material. In some embodiments, the sensitive electrode is oriented with respect to the displacement of the resonant element that occurs in the plane, thereby allowing the measurement of the magnetic field in the Z direction. In some embodiments, the sensitive electrode is oriented with respect to the displacement of the resonant element that occurs outside the plane, thereby allowing the measurement of the magnetic field in the X or Y direction. In some embodiments, the orientation of the resonant element for measurements in the X direction is orthogonal to the orientation of the resonant element for measurements in the Y direction. In some embodiments, two or more sensitive electrodes are oriented such that they measure the displacement of the resonant element in multiple directions. For example, two sensitive electrodes may be oriented to measure the displacement of the resonant element in the X and Z directions.

In some embodiments, the sensitive electrode is supported at least on some edges of the device by a plurality of dense column distributions. In some embodiments, each column is in contact with only one of the sensitive electrode and a lower electrode. In some embodiments, each column is in contact with both the sensitive electrode and the lower electrode.

In some embodiments, the sensitive electrode is surrounded by a protective electrode to minimize parasitic capacitance. In some embodiments, an upper electrode and a lower electrode of the device are connected by two columns having rust in between, thereby receiving support for the upper electrode from the two columns. In some embodiments, a plurality of resonator devices can be used to form a three-dimensional compass, an accelerometer or any other suitable device. In another aspect, the systems and methods described herein provide a magnetometer device. A source for generating a current disposed within the magnetometer device, and a plurality of resonant elements are arranged close to the source. Only one of the resonant elements is connected to the source. The device also includes a plurality of guide wires arranged close to the resonant elements. The guide wires electrically connect the resonant elements in such a way that the current applied in the resonant element connected to the source is propagated through the resonant elements. The guide wires can be arranged in such a way that they do not affect the capacitance variation. For example, the result can be achieved by arranging metallic wires without releasing. This can ensure that the displacement (and the capacitance variation) with respect to the guide wires does not cancel the capacitance variation such that the net capacitance variation becomes zero.

In even another aspect, the systems and methods described herein are provided for an accelerometer device. A sensitive electrode is disposed within the accelerometer device, and a resonant element is disposed close to the sensitive electrode. The resonant element includes a protective electrode disposed around an inner core of dielectric material. The device also includes a source to generate a voltage. The source is connected to the resonant element and applies the voltage. The accelerometer device measures an external acceleration of the resonant element as a variation of capacitance between the protective electrode and the sensitive electrode. Displacement can occur due to external acceleration, while voltage can be applied to measure capacitance variation.

In yet another aspect, the systems and methods described herein are provided for a chip comprising a MEMS device arranged in an integrated circuit. The chip includes electronic elements formed on a substrate of semiconductor material and a stack of interconnection layers produced above the substrate of semiconductor material. The interconnection layers include a plurality of layers of conductive material. Each layer of conductive material is separated by a layer of dielectric material. The MEMS device is formed within the interconnection layer stack by applying HF (hydrogen fluoride) gas to the interconnection layer stack. The MEMS device includes a protective electrode of conductive material disposed around an inner core of dielectric material. Brief description of the drawings

Other advantages and characteristics of the systems and methods described in this specification can be appreciated from the following description, which provides a non-limiting description of the illustrative embodiments, referring to the accompanying drawings, in which:

Fig. 1 depicts a schematic cross section of a prior art motion sensor device; Fig. 2 depicts a schematic cross section of a motion sensor device, according to an illustrative embodiment of the invention;

Fig. 3A depicts a cross section of a MEMS device having a plurality of resonant elements, according to an illustrative embodiment of the invention;

Fig. 3B represents a cross section of a MEMS device having a plurality of resonant elements, according to another illustrative embodiment of the invention; Fig. 4 depicts a schematic flow of a current through a plurality of resonant elements, according to an illustrative embodiment of the invention;

Fig. 5A represents a cross section of a MEMS device having a plurality of resonant elements and corresponding guide wires, according to an illustrative embodiment of the invention;

Fig. 5B represents a cross section of a MEMS device having a resonant element and corresponding guide wires, according to an illustrative embodiment of the invention;

Fig. 6 represents a plurality of elements that are mechanically coupled, according to an illustrative embodiment of the invention; Fig. 7 A represents a cross section of a MEMS device having a plurality of resonant elements that are mechanically coupled, according to an illustrative embodiment of the invention;

Fig. 7B depicts a cross section of a MEMS device having a plurality of resonant elements that are mechanically coupled, according to another illustrative embodiment of the invention;

Fig. 8A represents a schematic orientation for a resonant element, according to an illustrative embodiment of the invention;

Fig. 8B represents a schematic orientation for a resonant element, according to another illustrative embodiment of the invention;

Fig. 8C represents a schematic orientation for a resonant element, according to even another illustrative embodiment of the invention; Fig. 9 represents a cross section of a MEMS device having a plurality of resonant elements and support anchors, according to an illustrative embodiment of the invention;

Fig. 10 depicts a cross section of a MEMS device having a plurality of resonant elements and support anchors, according to another illustrative embodiment of the invention; Fig. 11 A represents a cross section of a first set of process flow steps for manufacturing a MEMS device having a plurality of resonant elements, according to an illustrative embodiment of the invention;

Fig. 11B represents a cross section of a second set of process flow steps for manufacturing a MEMS device having a plurality of resonant elements, according to an illustrative embodiment of the invention;

Fig. 11C depicts a cross section of a third set of process flow steps for manufacturing a MEMS device having a plurality of resonant elements, according to an illustrative embodiment of the invention;

Fig. 12A depicts a schematic view of a MEMS device having a thin finger, according to an illustrative embodiment of the invention; and Fig. 12B represents a schematic view of a MEMS device having a thin finger, according to another illustrative embodiment of the invention. Detailed description of some embodiments

To provide a full understanding of the systems and methods described in this specification, certain illustrative embodiments will now be described. However, one skilled in the art will understand that the systems and methods described herein can be adapted and modified as appropriate for the application being addressed and that the systems and methods described herein can be used in other suitable applications, and that those other additions and modifications will not depart from the scope thereof.

Fig. 1 depicts an illustrative schematic cross section of a prior art motion sensor device 100. The device 100 includes a resonant element in the form of test mass 102, which is anchored by springs 104. The test mass 102 is arranged in the vicinity of a sensitive electrode 106. In some embodiments, the device 100 functions as a magnetometer, for example, a magnetometer based on Lorentz force or a compass, which is a specific case of a magnetometer. Such a magnetometer depends on the mechanical movement of the test mass 102 due to the Lorentz force acting on the test mass when a current is applied to the test mass 102 in the presence of a target magnetic field. The test mass 102 can be brought to its resonance in order to obtain the maximum output signal. The mechanical movement of the test mass 102 can be felt either electronically or optically. A piezoresistive and electrostatic transduction method can be used for electronic detection. Displacement measurement with laser source or LED source can be used for optical detection.

A current is applied to the test mass 102 in the presence of the target magnetic field. The applied current can be monotonous or periodic. As a result, the test mass 102 exhibits a movement with respect to the electrode Sensitive 106, causing a capacitance variation between the test mass 102 and the sensitive electrode 106. In one embodiment, the capacitance variation can be measured using a load amplifier that produces a voltage proportional to the capacitance between the test mass 102 and the sensitive electrode 106. The output voltage of the load amplifier can be connected to a comparator that compares the output voltage corresponding to the new capacitance with a reference voltage corresponding to the original capacitance. The reference voltage and the output voltage can be received in analog or digital form in a processor to calculate the target magnetic field. In another embodiment, the capacitance variation is produced as a current and is calculated on the basis of output and reference currents.

However, the motion sensor device described above may be susceptible to interference from electromagnetic or electrostatic dispersion fields or other similar effects, leading to lower sensitivity. In addition, interference from Brownian noise due to the air medium present within the device may further affect the sensitivity of the device. For example, interference may affect the capacitance variation between test mass 102 and sensitive electrode 106. As a result, the target magnetic field can be measured by incorrectly interpreting the device unsuitable for its intended purpose.

An illustrative embodiment of a motion sensor device for addressing such interference is depicted in Fig. 2. Fig. 2 depicts an illustrative schematic cross section of a motion sensor device 200. The device 200 includes a resonant element having a wire 202 enclosed in oxide 204 and a protective electrode 206, in addition to the sensitive electrode 208. The mechanical structure depicted includes oxide 204 and a protective electrode 206 protects the wire 202 from interference effects. The mechanical structure can also act as an electrical protector between the sensitive electrode 208 and the wire 202. The Mechanical structure can also act as a mechanical barrier against chemical attack agents used during the manufacturing process of a CMOS. Since the wire 202 is embedded in the oxide, its electro-migration limit does not change. The mechanical structure may include a mixture of one or more metals and oxide. In addition, the mismatch of the thermal expansion coefficient (CTE) between the resonant element and the underlying wafer can be reduced, producing a better robustness against temperature. In some embodiments, a voltage source is connected to the mechanical structure to apply a constant voltage. The mechanical structure allows an extra electrical point that can be set at a desired voltage that facilitates electronic design.

In some embodiments, the device 200 includes multiple threads embedded in rust. The wires can be connected in series through guide wires included in the device 200. The Lorentz current through a wire interacts with the magnetic field and creates a magnetic force that excites the vibration of the structure. Connecting the wires in series can create a multiplicative effect on Lorentz's strength, achieving high performance with a low current value. As a result, only one electrical source may be necessary to supply current to the wires in the device 200. In one embodiment, the wires are connected in parallel. The current can be divided between the wires that need a higher current to be introduced compared to the serial configuration. In series configuration, the current can propagate through the resonant wires in the same direction. Otherwise, if any of the resonant wires had current flowing in the opposite direction to other resonant wires, the effects on each other can be nullified. The guide wires can ensure that such cancellation does not take place, which may be the case if the resonant wires were simply connected end to end without guide wires.

In some embodiments, the protective electrode 206 may include a thin finger or path on its surface in front of the sensitive electrode 208. The thin finger may be manufactured as a path that has no metal disposed thereon. As such, The thin finger is essentially deposited as a projection on the surface of the sensitive electrode 208. Since the thin finger is disposed closer to the sensitive electrode 208, it can help increase the capacitance variation between the protective electrode 206 and the sensitive electrode 208 with respect to a similar displacement of the protective electrode 206. In some embodiments, the movement of the thin finger also produces a topological change because the thin finger enters the cavity of the sensitive electrode 208, which is then added to the capacitance of its walls as well as to the surface. As a result, the capacitance variation by vertical displacement may be higher, and therefore the electrostatic pressure may be higher as well.

Both devices 100 and 200 can be configured to function as magnetometers, accelerometers or any other suitable sensor device. They can be manufactured using the nanoEMS ™ process described in U.S. Patent Application Publication. commonly possessed no. 2010/0295138, entitled "Methods and Systems for the Manufacture of MEMS CMOS Devices", and hereby incorporated by reference in its entirety.

Fig. 3A depicts an illustrative cross section of a MEMS device 300 having a plurality of resonant elements and a sensitive electrode 308. In some embodiments, the MEMS device 300 includes about 50 to 100 resonant elements. Each resonant element includes a wire 302 embedded in oxide 304. The resonant element also includes a protective electrode 306 made of conductive material. In one embodiment, the MEMS device 300 is configured to be a magnetometer. When a current is applied to the resonant element in the presence of an objective magnetic field, the resonant element may exhibit a movement with respect to the sensitive electrode 308, causing a capacitance variation between the resonant element and the sensitive electrode 308. In one embodiment, the Capacitance variation can be measured using a load amplifier that produces a voltage proportional to the capacitance between the element resonant and sensitive electrode 308. Multiple resonant elements or distributions may be included for redundancy and / or for measuring the magnetic field in multiple dimensions. For example, each of three resonant elements can measure the magnetic field in the X, Y, and Z directions. In some embodiment, the sensing electronics for the magnetometer includes a transimpedance amplifier (which converts current to voltage).

The resonant element may include more than one thread. This is illustrated in the MEMS device 350 of Fig. 3B. Fig. 3B depicts an illustrative cross section of a MEMS device 350 having a plurality of resonant elements. Each resonant element includes threads 352 and 354 embedded in oxide 356. In some embodiments, each resonant element includes up to about twelve resonant elements. The resonant element also includes a protective electrode 358 made of conductive material. In one embodiment, the MEMS 350 device is configured to be a magnetometer. When a current is applied to the resonant element in the presence of an objective magnetic field, the resonant element may exhibit a movement with respect to the sensitive electrode 360, causing a capacitance variation between the resonant element and the sensitive electrode 360. In one embodiment, the Capacitance variation can be measured using a load amplifier that produces a voltage proportional to the capacitance between the resonant element and the sensitive electrode 360. Multiple resonant elements or distributions can be included for redundancy and / or for measuring the magnetic field in multiple dimensions. For example, each of three resonant elements can measure the magnetic field in the X, Y, and Z directions.

In some embodiments, multiple oxide-embedded wires of a resonant element in series can be connected by guide wires arranged in the MEMS device. The Lorentz current through each wire interacts with the magnetic field and can create a magnetic force that excites the vibration of the resonant element. Connecting the wires in series can create a multiplicative effect in the Lorentz force, achieving high performance with a low current value. As a result, only one electrical source may be necessary to supply current to the wires in the resonant element. The electrical source may be a current source, a voltage source or any other suitable source. The current can propagate in the same direction in all resonant elements.

Both devices 300 and 350 can be configured to function as magnetometers, accelerometers or any other suitable sensor device. They can be manufactured using the nanoEMS ™ process described in U.S. Patent Application Publication. Commonly possessed No. 2010/0295138, entitled "Methods and Systems for the Manufacture of MEMS CMOS Devices", and hereby incorporated by reference in its entirety.

Fig. 4 depicts an illustrative schematic flow 400 of current through a plurality of wires 402. The wires 402 may be embedded in oxide of a single resonant element or may be scattered over multiple resonant elements. The wires 402 may vary from about 300 to about 400 μηι in length. In some embodiments, threads 402 may be approximately 800 μιη long. In any case, the wires 402 are connected in series by the guide wires 404 and require only one electrical source to propagate the current through the wires 402. The wires 404 connected in series function as a single resonant element and can allow a Low current requirement (for example, less than 1 mA) for a motion sensor device having such a configuration. The current can propagate in the same direction in all resonant elements.

Figs. 5A and 5B represent illustrative cross sections of MEMS devices having resonant elements connected in series. Fig. 5 A depicts an illustrative cross section of a MEMS device 500 having a plurality of resonant elements and corresponding guide wires. Each resonant element includes a 502 thread embedded in oxide. Each element Resonant also includes a protective electrode made of conductive material. The wires 502 for the resonant elements are connected in series through guide wires 504. Fig. 5B represents an illustrative cross-section of another MEMS device 550 having a resonant element and corresponding guide wires. In this embodiment, the resonant element includes multiple threads 552 embedded in oxide. The resonant element also includes a protective electrode made of conductive material. The wires 552 for the resonant elements are connected in series via guide wires 554. The guide wires 504 or 554 can be arranged under the resonant elements as illustrated in Figs. 5A and 5B, or may be arranged in any other suitable part of the MEMS device as necessary. The current can propagate in the same direction in the 502 or 552 threads. The 504 or 554 guide wires can be loose metal wires in such a way that they do not cancel their accumulated force effects. As mentioned before, connecting the wires in series can allow high performance of the MEMS device with a low current value. As a result, only one electrical source may be necessary to supply current to the wires in the resonant element. The electrical source may be a current source, a voltage source or any other suitable source. In some embodiments, wires 502 or 552 can be connected in parallel or a combination that includes serial and parallel configurations.

In one embodiment, MEMS 500 or 550 device is configured to be a magnetometer. When a current is applied to the resonant element in the presence of a target magnetic field, each resonant element can exhibit a movement with respect to a sensitive electrode, causing a capacitance variation between the resonant element and the sensitive electrode. In one embodiment, the capacitance variation can be measured using a charge amplifier that produces a voltage proportional to the capacitance between the resonant element and the sensitive electrode. In some embodiments, an amplifier of transimpedance to measure the capacitance variation for a MEMS compass device.

Both devices 500 and 550 can be configured to function as magnetometers, accelerometers or any other suitable sensor device. They can be manufactured using the nanoEMS ™ process described in U.S. Patent Application Publication. commonly possessed no. 2010/0295138, entitled "Methods and Systems for the Manufacture of MEMS CMOS Devices", and hereby incorporated by reference in its entirety.

In some embodiments, the mechanical structures of multiple resonant elements are mechanically coupled such that they vibrate with a single resonant frequency. This may be the case even if the resonant frequency of each resonant element is slightly different. This allows the resonant elements to interfere in a constructive manner and the felt current can be maximized. Fig. 6 depicts an illustrative mechanical structure 600 having a plurality of resonant elements 602 that are mechanically coupled. The N resonant elements (with stiffness from Ki to K) can be joined through couplings with stiffness K _C. If K _c «Ki and K _c « K ₂ and so on, the N resonant elements vibrate on the same frequency behaving as a single resonant element with stiffness Ki + K ₂ + ... + K. The low value of K _c can help keep the accumulated stiffness of the coupled resonant elements low.

In some embodiments, the protective electrodes of respective resonant elements may be connected by conductive material to achieve mechanical coupling. The conductive material may include metals such as aluminum, copper or any other suitable metal and / or alloys such as an AlCu alloy. The connection can be established in several parts of the protective electrode as illustrated in Figs. 7A and 7B. In some embodiments, the mechanical coupling conductive material may bend while allowing each Resonant element significantly maintain its curvature. This can help the resonant elements mechanically coupled to vibrate on a single resonant frequency. The low value of K _c can help ensure soft mechanical couplings for this purpose.

Fig. 7A depicts an illustrative cross-section of a MEMS device 700 having a plurality of resonant elements 702 that are mechanically coupled through a conductive material 704. Conductive material 704 connects the resonant elements 702 and may allow the elements resonants vibrate on a single resonant frequency. Fig. 7B depicts an illustrative cross section of another MEMS device 750 having a plurality of resonant elements 752 that are mechanically coupled through a conductive material 754. Conductive material 754 connects the resonant elements 752 in a different position to the depicted in Fig. 7A, but provide a similar ability to resonant elements to vibrate on a single resonant frequency.

Both 700 and 750 devices can be configured to function as magnetometers, accelerometers or any other suitable sensor device. They can be manufactured using the nanoEMS ™ process described in U.S. Patent Application Publication. commonly possessed no. 2010/0295138, entitled "Methods and Systems for the Manufacture of MEMS CMOS Devices", and hereby incorporated by reference in its entirety. Fig. 8A represents an illustrative schematic orientation 800 for the resonant element 802. A MEMS device that includes a resonant element 802 has the sensitive electrode oriented with respect to the displacement of the resonant element 802 that occurs outside the plane, thereby allowing the measurement of the magnetic field in the X direction. Fig. 8B represents an illustrative schematic orientation 840 for the resonant element 842. A MEMS device which includes a resonant element 842 has the sensitive electrode oriented with respect to the displacement of the resonant element 842 that occurs outside the plane, thereby allowing the measurement of the magnetic field in the Y direction. Fig. 8C represents an illustrative schematic orientation 880 for the resonant element 882. A MEMS device that includes a resonant element 882 has the sensitive electrode oriented with respect to the displacement of the resonant element that occurs in the plane, thereby allowing the measurement of the magnetic field in the Z direction. In some embodiments , a plurality of such resonant elements or distributions and the corresponding sensitive electrodes can be included in a MEMS device to form a three-dimensional magnetometer.

Fig. 9 depicts an illustrative cross section of a MEMS device 900 having a plurality of resonant elements 902 and support anchors 906. The resonant elements can be designed in different ways, for example, in the form of bridges, cantilever beams, coils or any other suitable configuration. Cantilever beams can be much less sensitive to temperature variations than bridges. It may be desirable to use this type of structure if better robustness is sought against temperature. Bridges may be preferred if the length needs to be maximized. This is because the Applicant has experimentally verified that the residual tension in the metallic layers of the CMOS processes is generally of tension, and therefore tends to maintain a great degree of flatness in the bridges. For example, bridges can be used to build a magnetometer in which current is required to flow in one direction all the time. Since the bridges are connected in series, the current will flow only in one direction (due to the guide wires) and are well adapted to build a magnetometer. However, if the limitation is to reduce the frequency mismatch to maximize the quality factor, Q, of the distribution, then a cantilever beam structure may be a better option. Additionally, the proposed configuration may require anchors 906 to support the sensitive electrode 904, and ensure that the sensitive electrode 904 does not bend or damage the MEMS device. The anchors 906 can occupy variable spaces in a given die. For example, the occupied die area for a given set of anchors can be approximately 10 μηι x 10 μπι. In another example, the occupied area of dice can be approximately 5 μηι x 5 μηι. This set of anchors allows a denser distribution of anchor sets. The thicker the anchors, the more sets of anchors can be placed in a given die space. More anchors per area can also cover more parasitic capacitance. The best result can be obtained by minimizing the distance between sets of anchors so that the total area in the die dedicated to the anchors can be reduced. Additionally, thin anchors take up less space and allow more space for the MEMS device itself to be placed in the given space of the die. The anchors 906 are constructed in such a way that they are electrically isolated from the top to the bottom. The anchors are manufactured in such a way that when chemical attack with HF steam is carried out, it has to travel a longer path to record the oxide. As a result, part of the oxide 908 remains after etching with HF steam and insulates the anchors from the covers and / or the lower metal layer of the MEMS device.

Fig. 10 represents an illustrative cross section of a MEMS device 1000 having a plurality of resonant elements 1002 and support column anchors 1008. The term "anchor" and "column" can be used interchangeably in the context of this description. The MEMS 1000 device differs from the MEMS 900 device in certain aspects. For example, column anchors 1008 can support the upper metal covering or layer 1006 in the MEMS 1000 device, for example, spray deposition of Al or any other suitable thin film covering, and ensure that it does not bend. However, column anchors 1008 are metal-only structures, for example, metal columns and tracks. Such anchors can Short circuit cover 1006 with the bottom metal layer of the MEMS device. As illustrated in Fig. 10, a portion of the stack is replaced by dielectric material 1010 between column anchors 1008. The oxide portion may have a square shape or any other suitable shape such that the oxide is not etched by chemical attack. The cover 1006 cannot have relief holes to preserve the oxide below. The combination of metal and oxide can provide better robustness compared to other anchor implementations. The mechanical robustness of column anchors 1008 is independent of the etching time by chemical attack. Therefore, even long etch times cannot cause a decrease in the support provided by the column anchors 1008 in the covering 1006.

The MEMS 1000 device differs from the MEMS 900 device in another aspect. The sensitive electrode 1004 of the MEMS 1000 device is disposed within the cavity next to the resonant element 1002 and is electrically protected from the outside world. It is surrounded by a protective enclosure that includes conductive material of covering 1006, column anchors 1008, and the bottom layer of the MEMS device. As such, there is minimal or no interference by external electromagnetic or electrostatic fields. This reduces the parasitic capacitance in the sensitive electrode 1004 and further helps to increase the SNR of the MEMS 1000 device to allow a higher sensitivity. For example, the MEMS 1000 device can detect even smaller changes in a target magnetic field compared to the MEMS 900 device and allows a larger dynamic range for the target magnetic field. In addition, the proposed configuration can provide better performance during manufacturing as well as allow larger (or longer) resonant elements 102, if so desired.

Both 900 and 1000 devices can be configured to function as magnetometers, accelerometers or any other suitable sensor device. They can be manufactured using the nanoEMS process described in U.S. Patent Application Publication. commonly possessed no. 2010/0295138, entitled "Methods and Systems for the Manufacture of MEMS CMOS Devices", and hereby incorporated by reference in its entirety. The following describes process flow steps for manufacturing a MEMS device from a distribution through a CMOS MEMS based process, for example, a nanoEMS ™ process. However, manufacturing processes for the MEMS device should not be limited to CMS MEMS based processes and may include MEMS based processes, NEMS based processes and other suitable processes.

Fig. HA represents an illustrative cross section of a first set of process flow steps for manufacturing a MEMS device having a plurality of resonant elements. The thickness of the layers has been increased. In one embodiment, the MEMS device is manufactured using a standard CMOS process. In one embodiment, the MEMS device is manufactured in a cavity formed within interconnection layers of a CMOS chip. In an alternative embodiment, the MEMS device is manufactured as a stand-alone MEMS device. Initially a metallic layer is deposited. The metal layer can be made of, for example, AlCu metal alloy. A masking layer is deposited on top of the metal layer, and then the metal layer is etched by chemical attack to form the plates 1102. An Intermediate Metal Dielectric layer (FMD) is deposited on top of the plates 1102, followed by a masking layer and then The IMD layer is etched by chemical attack and is filled with metal to form separators or tracks 1106. In one embodiment, the IMD layer includes an undoped oxide layer. Another metal layer is deposited followed by a masking layer deposited on top of the metal layer, and then the metal layer is etched by chemical attack to form plates 1104. Another FMD layer is deposited on top of plates 1104, followed by a masking layer and then the IMD layer is etched by chemical attack and filled with metal to form separators or tracks 1108. The plates 1102 and 1104 and the separators 1106 and 1108 together form part of the protective electrode for the resonant element. A metal layer is deposited on the spacers 1 108 to form another part of the protective electrode. Another IMD layer is deposited on the bridge 410, followed by the upper metal layer 11 12. A masking layer is deposited on the upper metal layer 11 12. The upper metal layer 1 112 is then etched by chemical attack to form through holes 1 114. Through holes may allow the passage of the chemical attack agent, for example, gaseous HF, to etch the material under the upper metal layer 1112 by chemical attack.

Figs. 1 1B and 1 1C represent cross sections of a second and a third set of process flow steps for manufacturing a MEMS device having a plurality of resonant elements. A chemical attack agent, for example, dry HF, is released through the through holes 1 114 in the upper metal layer 11 12. The chemical attack agent etches part of the IMD layers by chemical attack to release the anchors and the MEMS device bridge, as shown in Fig. 11B. The oxide 1 142 of the IMD layers remains to provide support to the MEMS device. Finally, a metallization layer 1 182 is deposited on the upper metal layer 1 1 12 to seal the MEMS device from the outdoor environment, as shown in Fig. 1 1 C, for example, by normally sputtering deposition. ) of Al and modeling. In one embodiment, the MEMS device is manufactured using integrated chip technology based on MEMS, based on NEMS or based on CMOS MEMS.

In some embodiments, a MEMS device is arranged in an integrated circuit. The process flow stages of Figs. 1 1A-1 1 C are made in the interconnection layers of the integrated circuit. The layers that form the electrical and / or electronic elements in a semiconductor material substrate are produced. The interconnection layers are produced, including a lower layer of conductive material and an upper layer of conductive material, separated by at least one layer of dielectric material. The top layers or passivation layers, made with a sub-layer of silicon oxide and TiN on top, can be modeled to open then the necessary holes to apply the vHF later. A part of the MEMS device is formed within the interconnection layers by applying gaseous HF to the at least one layer of dielectric material according to the process flow steps described with respect to Figs. 11A-11C.

In some embodiments, a MEMS device includes a resonant element that has a protective electrode that includes a finger or thin path on its surface in front of a sensitive electrode. The thin finger can increase the sensitivity of inertia devices or any electrostatic device, and is not limited to the embodiment discussed below. The thin finger can be manufactured as a path that has no metal arranged on top of it. As such, the thin finger is essentially deposited as a protrusion on the surface of the sensitive electrode. Figs. 12A and 12B show illustrative embodiments of MEMS 1200 and 1250 devices having thin fingers. The device 1200 includes the sensitive electrode 1202 and the resonant element 1204 having a protective electrode that includes a thin finger 1206 on its surface in front of the sensitive electrode 1202. Similarly, the device 1250 includes the sensitive electrode 1252 and the resonant element 1254 having a protective electrode that includes a thin finger 1256 on its surface in front of the sensitive electrode 1252. While the sensitive electrode 1202 is a three-sided structure, the sensitive electrode 1252 includes four sides. Many variations of the sensitive electrode are possible as can be established by one skilled in the art.

Since the thin finger 1206 or 1256 is arranged closer to the sensitive electrode 1202 or 1252, it can help increase the capacitance variation between the resonant electrode 1204 or 1254 and the sensitive electrode 1202 with respect to a similar displacement of the resonant electrode. In some embodiments, the movement of the thin finger also produces a topological change because the thin finger enters the cavity of the sensitive electrode, which is then added to the capacitance of its walls as well as to the surface. As a result, the capacitance variation by vertical displacement may be higher, and therefore the electrostatic pressure can be higher too. In some embodiments, the fingers are more effective when the vertical separation is relatively larger than the lateral separation. In some embodiments, the potential improvement of vertical sensitivity may be up to about 550%. This can result in a linear reduction in size of up to about 2.35 in the resonant element for similar sensitivity, for example, a 42 μηι diameter element with thin fingers may be of sensitivity equivalent to a 100 μιη diameter element No thin fingers In some embodiments, multiple resonant elements can be manufactured in the interconnection layers and disposed on top of a specific application integrated circuit (ASIC) that can selectively control the resonant elements. In some embodiments, a single type of MEMS device is manufactured on top of the ASIC, for example, a magnetometer. Certain devices may not be used initially and be reserved for redundancy in case of failure of another device in use. In case of failure of a device due to issues during manufacturing, the redundant device can help improve performance. In the event of a device failure during operation, the redundant device can help improve long-term reliability.

In some embodiments, the multiple resonant elements are configured as sensors of different types. For example, resonant elements may include a magnetometer, a gyroscope and an accelerometer. In another example, resonant elements may include a 3D magnetometer, a 3D gyroscope and a 3D accelerometer. In some embodiments, the resonant elements are constructed on top of an ASIC and the ASIC can switch between each resonant element as necessary. For example, a configurable motion sensor cell can be formed including a magnetometer, gyroscope and accelerometer within the interconnection layers of the ASIC. The ASIC controller of the motion sensor cell can then select whether the sensor cell of Movement must offer the functionality of a magnetometer, gyroscope or accelerometer. In some embodiments, a hybrid motion sensor is constructed with redundant elements as well as multiple types of motion sensor devices, thereby offering the combined benefits of configuration capacity, redundancy and reliability.

Applicants consider that all functional combinations of the embodiments described herein are topics that can be patented. Those skilled in the art will know or be able to determine, by using nothing but routine experimentation, many equivalents of the embodiments and practices described herein. Accordingly, it will be understood that the systems and methods described herein should not be limited to the embodiments described herein, but it is to be understood, from the following claims, that it is to be interpreted as broadly as Allow the law. It should also be noted that, although the following claims are arranged in a particular manner such that certain claims depend on other claims, either directly or indirectly, any of the following claims may depend on any other of the following claims, either directly or indirectly to perform the various embodiments described herein. What is claimed is:

Claims

1. A magnetometer device, comprising:

a sensitive electrode disposed within the magnetometer device;

a resonant element disposed close to the sensitive electrode, wherein the resonant element includes a protective electrode disposed around an inner wire;

a source to generate a current connected to the resonant element to apply the current through the inner wire thereby causing a displacement of the resonant element;

wherein a magnetic field of the resonant element is measured as a capacitance variation between the protective electrode and the sensitive electrode.

2. The device of claim 1, further comprising:

a plurality of resonant elements arranged close to the resonant element;

the plurality of guide wires arranged close to the resonant elements, wherein the guide wires electrically connect the resonant elements such that the current propagates through the plurality of resonant elements in one direction.

3. The device of claim 1, further comprising:

a voltage source connected to the protective electrode to apply a constant voltage to the protective electrode with respect to the sensitive electrode.

4. The device of claim 1, wherein the current is periodic.

5. The device of claim 1, wherein the at least two resonant elements are mechanically coupled such that they share a resonant frequency, wherein the mechanical coupling of the at least two resonant elements comprises the physical connection of the respective protective electrodes with conductive material.

6. The device of claim 1, wherein the sensitive electrode is oriented with respect to the displacement of the resonant element that occurs in the plane, thereby allowing the measurement of the magnetic field in the Z direction.

7. The device of claim 1, wherein the sensitive electrode is oriented with respect to the displacement of the resonant element that occurs outside the plane, thereby allowing the measurement of the magnetic field in the X or Y direction.

8. The device of claim 5, wherein the orientation of the resonator element for measurements in the X direction is orthogonal to the orientation of the resonator element for measurements in the Y direction.

9. The device of claim 1, wherein the sensitive electrode is supported at least on some edges of the device by a plurality of dense column distributions.

10. The device of claim 9, wherein each column is in contact with only one of the sensitive electrode and a lower electrode.

11. The device of claim 1, wherein the sensitive electrode is surrounded by a protective electrode to minimize parasitic capacitance.

12. The device of claim 9, wherein an upper electrode and a lower electrode of the device are connected by two columns having rust in between, thereby receiving support for the upper electrode from the two columns.

13. A magnetometer device, comprising:

a source for generating a current disposed within the magnetometer device;

a plurality of resonant elements arranged close to the source, where only one of the resonant elements is connected to the source;

a plurality of guide wires arranged close to the resonant elements, wherein the guide wires electrically connect the resonant elements such that the current applied to the resonant element connected to the source is propagated through the rest of resonant elements in one direction .

14. An accelerometer device, comprising:

a sensitive electrode disposed within the accelerometer device;

a resonant element disposed close to the sensitive electrode, wherein the resonant element includes a protective electrode disposed around an inner core of dielectric material;

wherein an acceleration of the resonant element is measured as a variation of capacitance between the protective electrode and the sensitive electrode.

15. A chip comprising a MEMS device arranged in an integrated circuit comprising:

electronic elements formed in a substrate of semiconductor material; a stack of interconnection layers, produced on top of the substrate of semiconductor material, including a plurality of layers of conductive material, each layer is separated by a layer of dielectric material; Y

the MEMS device formed within the stack of interconnection layers by applying gaseous HF to the stack of interconnection layers, wherein the MEMS device includes a protective electrode of conductive material disposed around an inner core of dielectric material.