WO2020029360A1

WO2020029360A1 - Sensor

Info

Publication number: WO2020029360A1
Application number: PCT/CN2018/104432
Authority: WO
Inventors: 邹泉波; 冷群文; 王喆
Original assignee: 歌尔股份有限公司; 北京航空航天大学青岛研究院
Priority date: 2018-08-06
Filing date: 2018-09-06
Publication date: 2020-02-13
Also published as: CN109211281A; CN109211281B

Abstract

Disclosed in the present invention is a sensor, wherein a detection structure comprises a first magnet, a second magnet, and a magnetoresistive sensor disposed in a common magnetic field formed by the first magnet and the second magnet. When at an initial position, the magnetoresistive sensor is located at a position in which the magnetic field direction of the first magnet is opposite to the magnetic field direction of the second magnet. The magnetoresistive sensor is configured to, during the vibration of a diaphragm, sense a variation in the common magnetic field of the first magnet and the second magnet and then output a variation electrical signal. Further comprised is a driving device for adjusting mutual positions between the magnetoresistive sensor and the first magnet and second magnet. Regarding the sensor of the present invention, the relative position between the magnetoresistive sensor and the first magnet and second magnet may be finely adjusted by means of the driving device, ensuring that the magnetoresistive sensor may work in a suitable magnetic field, and preventing an impact on sensor sensitivity due to fabrication and assembly errors.

Description

A sensor

Technical field

The present invention relates to the field of measurement. More specifically, the present invention relates to a sensor, such as a microphone, a pressure sensor, and a displacement sensor.

Background technique

Existing mainstream sensors, such as microphones, pressure sensors, displacement sensors, etc., are detected by the principle of a flat capacitor. For example, in the structure of Michael Wind, the plate capacitor includes a substrate and a back plate and a diaphragm formed on the substrate. There is a gap between the back plate and the diaphragm, so that the back plate and the diaphragm constitute a flat plate type. Capacitor sensing structure.

In order to take full advantage of the mechanical sensitivity of the diaphragm, the microphone needs to design a huge back cavity with environmental pressure to ensure that the rigidity of the flowing air is far from the diaphragm. The volume of the dorsal cavity is usually much larger than 1 mm ³ , for example, it is usually designed to be 1-15 mm ³ . And when the microphone chip is packaged, its cavity needs to be opened. This limits the design of the smallest MEMS microphone package (> 3mm ³ ).

This is because if the volume of the back cavity is too small, it is not conducive to the circulation of air, and the rigidity of this air will greatly reduce the mechanical sensitivity of the diaphragm. In addition, for equalizing pressure, dense through holes are usually designed on the back plate. The gap caused by air viscosity or the air flow resistance in the perforation becomes the dominant factor of MEMS microphone noise, which limits the high signal-to-noise performance of the microphone.

In the traditional detection structure using the principle of magnetoresistance, a detection structure of a single magnet or a single magnetoresistive sensor is used. Because the linear range of the magnetoresistive sensor is very narrow, the detection sensitivity of the magnetoresistive sensor is very low.

Fig. 7a shows a coordinate diagram of the distribution of a single magnet and a single magnetoresistive sensor in the prior art, where the center position of the magnet is the coordinate origin. Fig. 7b shows a simulation diagram of the magnetic field distribution in Fig. 7a. The size of the permanent magnet is 10μm * 5μm * 0.5μm. The abscissa represents the vertical distance z (m) of the magnetoresistive sensor relative to the center of the permanent magnet, and the ordinate represents the magnetic field strength Bx (T) and the magnetic field change gradient dB / dz (T / m). Line a in the figure represents the change curve of Bx (T) with z (m), and line b represents the change curve of magnetic field change gradient dB / dz (T / m) with z (m).

It can be seen from FIG. 7b that the starting point of the linear detection area of the magnetoresistive sensor (eg, giant magnetoresistive GMR) is a position about 18 μm from the center z (m) of the permanent magnet. At this time, the magnetic field change gradient dB / dz (T / m) is about 4700 T / m (below 10 ⁴ T / m). Maximum intrinsic sensitivity of the microphone _{_{Soc = V B * S R *}} S B * S M ~ 2V * (0.3% / Gs) * (10 4 T / m) * (5nm / Pa) = 3mV / Pa, much lower than The sensitivity of a conventional microphone is 13mV / Pa. Where V _B is the GMR bias, S _R = (ΔR / R) / ΔB, S _B = ΔB / ΔZ is the magnetic field gradient, and S _M = ΔZ / ΔP is the mechanical sensitivity.

Therefore, a new magnetic sensor detection structure is needed to improve the detection sensitivity.

Summary of the invention

An object of the present invention is to provide a new technical solution for a sensor.

According to a first aspect of the present invention, there is provided a sensor including a first substrate and a diaphragm supported above the first substrate by a first spacer, and further comprising a detection structure for outputting an electric signal characterizing a deformation of the diaphragm. The detection structure includes a first magnet, a second magnet, and a magnetoresistive sensor disposed in a common magnetic field formed by the first magnet and the second magnet; in an initial position, the magnetoresistive sensor is located in a magnetic field direction of the first magnet and The magnetic field direction of the second magnet is opposite; the magnetoresistive sensor is configured to sense a change in the common magnetic field of the first magnet and the second magnet during the vibration of the diaphragm and output a changed electrical signal;

It also includes a driving device for adjusting the mutual position between the magnetoresistive sensor, the first magnet and the second magnet.

Optionally, the driving device is a piezoelectric sheet or an electrode sheet for providing an electrostatic force.

Optionally, at the initial position, the magnetoresistive sensor receives the magnetic field of the first magnet, which is equal to the magnitude of the magnetic field received by the second magnet and has the opposite direction.

Optionally, the first substrate, the first spacer, and the diaphragm surround a vacuum cavity; wherein the static deflection distance of the diaphragm under atmospheric pressure is smaller than the distance between the diaphragm and the first substrate; The device is arranged on the diaphragm;

The first magnet and the second magnet are sequentially arranged horizontally on the diaphragm in the same direction of the magnetic poles, and the magnetoresistive sensor is disposed on a first substrate at a position corresponding to the first magnet and the second magnet;

Alternatively, the first magnet and the second magnet are sequentially horizontally arranged on the first substrate in the same manner as the directions of the magnetic poles, and the magnetoresistive sensor is disposed on the diaphragm corresponding to the first magnet and the second magnet.

Optionally, the first substrate has a hollow cavity communicating with the outside, and further includes a cantilever spaced from the diaphragm, the cantilever and the diaphragm are suspended above the cavity in the first substrate, and the diaphragm An open cavity is enclosed with the first spacer and the substrate; the driving device is arranged on the diaphragm and / or on a cantilever;

The first magnet and the second magnet are sequentially arranged horizontally on the diaphragm in the same direction of the magnetic poles, and the magnetoresistive sensor is disposed on a cantilever corresponding to the first magnet and the second magnet;

Alternatively, the first magnet and the second magnet are sequentially horizontally arranged on the cantilever in the same direction as the magnetic pole direction, and the magnetoresistive sensor is disposed on the diaphragm corresponding to the first magnet and the second magnet. .

Optionally, the first substrate, the first spacer, and the diaphragm surround a vacuum cavity; wherein the static deflection distance of the diaphragm under atmospheric pressure is smaller than the distance between the diaphragm and the first substrate;

It further includes a cantilever spaced from the diaphragm through the second spacer, and the diaphragm and the second spacer and the cantilever surround an open cavity; the driving device is arranged on the diaphragm and / or the cantilever;

The magnetoresistive sensor is disposed on a diaphragm, the first magnet and the second magnet are respectively disposed on a first substrate and a cantilever located on both sides of the diaphragm, and the first magnet and the second magnet have opposite magnetic pole directions. Layout.

Optionally, the first magnet and the second magnet are symmetrical with respect to the magnetoresistive sensor.

Optionally, the first substrate has a hollow cavity in communication with the outside, and a first cantilever and a second cantilever are respectively provided on opposite sides of the diaphragm, and the diaphragm and the first cantilever and the second cantilever are connected to each other. Are spaced apart from each other, and both sides of the diaphragm are in communication with the outside; the driving device is arranged on the diaphragm and / or the first cantilever and / or the second cantilever;

The magnetoresistive sensor is disposed on the diaphragm, the first magnet and the second magnet are disposed on the first cantilever and the second cantilever, respectively, and the first magnet and the second magnet are arranged in opposite directions of the magnetic poles.

Optionally, the first magnet and the second magnet are magnetized films.

Optionally, the sensors are a microphone, a pressure sensor, and a displacement sensor

In the sensor of the present invention, when the magnetoresistive sensor vibrates with the diaphragm, the magnetoresistive sensor vibrates up and down at its initial position. Because the magnetoresistive sensor is affected by two magnets at the same time, the two magnets cooperate to reduce the strength of the entire magnetic field, and increase the sensitivity of the magnetic field change within the linear range of the magnetoresistive sensor. Detection sensitivity.

The relative position between the magnetoresistive sensor, the first magnet, and the second magnet can be fine-tuned by the driving device to ensure that the magnetoresistive sensor can work in a suitable magnetic field, which avoids the influence on the sensitivity of the sensor due to manufacturing and assembly errors.

Other features and advantages of the present invention will become clear from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

1 to 4 are schematic structural diagrams of four different embodiments of the sensor of the present invention.

5a is a coordinate diagram of a magnetoresistive sensor and two magnets in the embodiments shown in FIG. 1 and FIG. 2.

FIG. 5b is a simulation diagram of the magnetic field distribution in the embodiments shown in FIG. 1 and FIG. 2.

FIG. 6a is a coordinate diagram of a magnetoresistive sensor and two magnets in the embodiments shown in FIG. 3 and FIG. 4. FIG.

FIG. 6b is a simulation diagram of the magnetic field distribution in the embodiments shown in FIG. 3 and FIG. 4. FIG.

Fig. 6c is an enlarged view of the linear detection area of the magnetoresistive sensor in Fig. 6b.

Fig. 7a is a coordinate diagram of a single magnetoresistive sensor and a single magnet in the prior art.

Fig. 7b is a simulation diagram of a magnetic field distribution in the prior art shown in Fig. 7a.

detailed description

Various exemplary embodiments of the present invention will now be described in detail with reference to the drawings. It should be noted that, unless specifically stated otherwise, the relative arrangement of components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present invention.

The following description of at least one exemplary embodiment is actually merely illustrative and is in no way intended to limit the invention and its application or uses.

Techniques, methods, and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but where appropriate, the techniques, methods, and equipment should be considered as part of the description.

In all examples shown and discussed herein, any specific value should be construed as exemplary only and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

It should be noted that similar reference numerals and letters indicate similar items in the following drawings, so once an item is defined in one drawing, it need not be discussed further in subsequent drawings.

The sensor provided by the present invention may be a microphone, a pressure sensor, a displacement sensor, or other sensors well known to those skilled in the art. For example, when applied to a pressure sensor, the diaphragm is sensitive to external pressure, and changes in external pressure will drive the diaphragm to deform. When applied to a displacement sensor, a driving rod can be set to be connected with the diaphragm, and the diaphragm is deformed by the driving rod, which will not be listed one by one here.

For the convenience of description, a microphone is taken as an example to describe the technical solution of the present invention in detail.

A microphone provided by the present invention includes a substrate, a diaphragm supported above the substrate through a spacer, and a detection structure for outputting an electrical signal characterizing a deformation of the diaphragm. When sound acts on the diaphragm, the diaphragm will deform under the effect of sound pressure. At this time, the detection structure will output a changed electrical signal to characterize the degree of deformation of the diaphragm and achieve acoustic-electrical conversion.

The detection structure includes a first magnet, a second magnet, and a magnetoresistive sensor disposed in a common magnetic field formed by the first magnet and the second magnet. The first magnet and the second magnet are arranged correspondingly so that the magnetic fields of the two magnets interact with each other. The magnetoresistive sensor simultaneously senses the magnetic fields of the first magnet and the second magnet, so that the magnetoresistive sensor can sense the change in the common magnetic field of the first magnet and the second magnet during the vibration of the diaphragm, thereby outputting a changed electrical signal.

In the common magnetic field of the first magnet and the second magnet, in some positions, the magnetic fields of the two magnets are opposite to each other. At this position, the common magnetic field of the two magnets received by the magnetoresistive sensor is weakened compared to a single magnet. The initial position of the magnetoresistive sensor is a position where the magnetic field of the first magnet is opposite to that of the second magnet.

Preferably, at the initial position, the magnetoresistive sensor receives the magnetic field of the first magnet, and the magnetic field of the second magnet has the same magnitude and opposite direction. That is to say, at this position, the magnetoresistive sensor is subjected to the same magnitude of the magnetic field of the two magnets, and the directions are opposite. At this time, the common magnetic field of the two magnets received by the magnetoresistive sensor is zero.

The ideal position between the magnetoresistive sensor and the first and second magnets is fixed. When the sensor is manufactured and assembled, it will inevitably affect the position due to errors. Therefore, a drive device is required to adjust the magnetoresistive sensor. Mutual position with the first magnet and the second magnet.

The driving device may be, for example, a piezoelectric sheet or an electrode sheet for providing an electrostatic force. For example, when a piezoelectric sheet is selected, AlN, PZT, or ZnO materials, which are well known to those skilled in the art, may be used. By applying a DC bias voltage to the piezoelectric sheet, the piezoelectric sheet shifts the components carried by a certain distance, and the position is adjusted.

For example, when the driving device is an electrode sheet, an electrostatic force can be applied to the carried component through the electrode sheet, so that the carried component is offset by a certain distance, and the position adjustment is also realized.

The technical solution of the present invention is described in detail below in combination with specific embodiments.

Example 1

Specifically, in an embodiment of the present invention, referring to FIG. 3, the present invention provides a microphone including a first substrate 100 and a diaphragm 120 supported above the first substrate 100 through a first spacer 140. The first substrate 100, the first spacer 140, and the diaphragm 102 surround a vacuum cavity 130.

The first substrate 100 of the present invention may be made of single crystal silicon or other materials well known to those skilled in the art, and the first spacer 140 and the first spacer 140 may be formed by layer-by-layer deposition, patterning, and sacrificial processes. The vibration film 120 and the vacuum chamber 130 supported on the first substrate 100 can be sealed by, for example, low pressure plasma enhanced chemical vapor deposition (PECVD) at 200-350 ° C. This MEMS process belongs to the common knowledge of those skilled in the art and will not be described in detail here. The vacuum chamber 130 is preferably less than 1 kPa, which makes the residual gas viscosity in the vacuum chamber 130 much lower than the air viscosity at standard pressure.

Since a vacuum cavity lower than atmospheric pressure is formed between the diaphragm 120 and the first substrate 100, the diaphragm 120 will statically deflect under atmospheric pressure and no sound pressure, that is, the diaphragm 120 will face the first substrate 100. The direction is statically deflected. In order to prevent the diaphragm 120 from being deflected to contact the first substrate 100 when it is stationary, the static deflection distance of the diaphragm 120 is designed to be smaller than the distance between the diaphragm 120 and the first substrate 100. This can be achieved mainly by changing the rigidity of the diaphragm 120 and / or changing the distance between the diaphragm 120 and the first substrate 100.

For example, the size of the diaphragm 120 can be increased. Of course, the rigidity of the diaphragm 120 can also be improved by selecting a suitable material of the diaphragm 120. For example, the diaphragm 120 may be designed to have a mechanical sensitivity of 0.02 to 0.9 nm / Pa. That is to say, each time the pressure of 1Pa, the diaphragm 120 will deflect from 0.02-0.9nm. The rigidity of this diaphragm 120 is 10-100 times that of the traditional diaphragm, making the diaphragm 120 hard enough to resist the external Atmospheric pressure.

The corresponding initial gap between the diaphragm 120 and the first substrate 100 can be designed in the range of 1-100 μm, and in cooperation with the rigid diaphragm 120 described above, the problem that the diaphragm 120 collapses does not occur under atmospheric pressure.

In order to increase the sensitivity of the MEMS microphone, the MEMS microphone can use a highly sensitive detection member. In a specific embodiment of the present invention, the high-sensitivity detection member may use a magnetoresistive sensor 110 that outputs an electrical signal according to a change in a magnetic field, such as a giant magnetoresistive sensor (GMR) or a tunnel magnetoresistive sensor (TMR). By using the high-sensitivity magnetoresistive sensor 110 to obtain the detected electrical signal, the influence of the rigidity of the diaphragm on the overall sensitivity of the microphone can be compensated, and the acoustic performance of the thin and light microphone is ensured.

Referring to FIG. 3, a first magnet 150 and a second magnet 160 are provided on the first substrate 100 at a position on the side of the vacuum chamber 130. The first magnet 150 and the second magnet 160 may be magnetic films, and the magnetic films may be directly used. The magnetic material may be formed by magnetizing the thin film. In a specific embodiment of the present invention, the magnetic thin film may be made of CoCrPt or CoPt.

The first magnet 150 and the second magnet 160 may be formed on the first substrate 100 by deposition or other means known to those skilled in the art. Specifically, during manufacture, an insulating layer 170 may be deposited on the first substrate 100 first, and then a first magnet 150 and a second magnet 160 may be formed by a deposition and patterning process. In order to protect the first magnet 150 and the second magnet 160, a passivation layer 180 covering the first magnet 150 and the second magnet 160 may also be deposited on the insulating layer 170. The insulating layer and the passivation layer may be made of materials well known to those skilled in the art. It is no longer specified.

The first magnet 150 and the second magnet 160 are disposed adjacent to each other, and are sequentially horizontally arranged on the first substrate 100 in the same manner in the direction of the magnetic poles. For example, at the time of fabrication, two independent films are formed first, and then the two films are magnetized simultaneously. After magnetization, referring to the view direction of FIG. 3, the left side of the first magnet 150 and the second magnet 160 are both N poles, and the right side are S poles; vice versa.

Referring to the embodiment of FIG. 3, the magnetoresistive sensor 110 is disposed on one side of the vacuum chamber on the diaphragm 120, and the magnetoresistive sensor 110 is disposed corresponding to the first magnet 150 and the second magnet 160 on the first substrate 100. In order to draw out the electrical signals of the magnetoresistive sensor 110, a lead portion may be provided on one side of the vacuum chamber on the diaphragm 120, and one end of the lead portion is connected to the magnetoresistive sensor 110, and the other end extends from the diaphragm 120 to the first A pad 190 is formed outside the diaphragm 120 at the position of the spacer 140.

When the diaphragm 120 receives external sound pressure, the diaphragm 120 deforms in the direction of the first substrate 100. At this time, the magnetoresistive sensor 110 on the diaphragm 120 is close to the first magnet 150 and the second magnet 160, so that the magnetic The resistance sensor 110 can sense a change in a common magnetic field of the first magnet 150 and the second magnet 160, thereby outputting a changed electrical signal, and achieving acoustic-electric conversion.

The magnetoresistive sensor 110 may be disposed above the center line of the first magnet 150 and the second magnet 160. When the left side of the first magnet 150 and the second magnet 160 are both N poles and the right side are both S poles, the magnetic field directions of the first magnet 150 and the second magnet 160 are both returned from the N pole to the S pole. Therefore, at a position above the center line of the first magnet 150 and the second magnet 160, the magnetic directions of the first magnet 150 and the second magnet 160 are opposite and the magnetic field strength is approximately the same. This position is the initial position of the magnetoresistive sensor 110.

When the magnetoresistive sensor 110 vibrates with the diaphragm 120, the magnetoresistive sensor 110 vibrates up and down at the initial position. Because the magnetoresistive sensor 110 is affected by two magnets at the same time, the two magnets cooperate to reduce the strength of the entire magnetic field, and increase the sensitivity of the magnetic field change within the linear range of the magnetoresistive sensor 110, and finally increase the magnetoresistance The detection sensitivity of the sensor 110.

FIG. 6 a shows a coordinate diagram of the distribution of two magnets and a magnetoresistive sensor in the embodiment shown in FIG. 3. In this coordinate diagram, the origin position is located at the center of the two magnets. 6b and 6c show simulation diagrams of magnetic field distribution in the embodiment shown in FIG. 3. The size of both magnets is 6 μm * 4 μm * 0.5 μm, and the gap between the two magnets is 2 μm. The abscissa in Fig. 6b and Fig. 6c represent the vertical distance z (m) of the magnetoresistive sensor with respect to the center position of the two magnets, and the ordinate represents the magnetic field strength B (T) and the magnetic field change gradient dB / dx (T / m) . Line a1 in the figure represents the change curve of B (T) with z (m), and line b1 represents the change curve of magnetic field change gradient dB / dx (T / m) with z (m).

The magnetic field strength of the initial position of the magnetoresistive sensor 110 is 0, that is, the position where B (T) in line a1 is 0, and at this time, z (m) is about 4 μm. The distance between the center of each magnet is 4 μm. At this initial position, the value of the line b1 is approximately 2.0 * 10 ⁵ T / m. That is, the gradient of the magnetic field change at this position is 2.0 * 10 ⁵ T / m. Compared with the traditional single magnet structure, the sensitivity to magnetic field changes is greatly improved. In addition, the area of the line b1 on the left and right sides of the initial position is relatively flat, which ensures that the magnetoresistive sensor 110 can be located in its linear detection area.

In the microphone of the present invention, a vacuum cavity is enclosed between the diaphragm 120 and the first substrate 100, and the viscosity of the air in the vacuum cavity is much lower than the viscosity of the air in the ambient pressure, so that the acoustic resistance can reduce the vibration of the diaphragm 120. Effect, improving the signal-to-noise ratio of the microphone. In addition, since the MEMS microphone of this structure does not require a large-capacity back cavity, the overall size of the MEMS microphone can be greatly reduced, and the reliability of the microphone is enhanced.

The magnetoresistive sensor 110 is disposed on a side of the diaphragm 120 away from the vacuum chamber 130, that is, the magnetoresistive sensor 110 is disposed on the outside or the upper side of the diaphragm 120. The magnetoresistive sensor 110 is between the first magnet 150 and the second magnet 160. Although it is blocked by the diaphragm 120, the magnetic fields of the first magnet 150 and the second magnet 160 can still pass through the diaphragm 120 and be sensed by the magnetoresistive sensor 110, so it will not affect the performance of the MEMS microphone.

Of course, the magnetoresistive sensor 110 may also be disposed in the multilayer film 120 to protect the magnetoresistive sensor 110. In an optional embodiment of the present invention, the diaphragm 120 may adopt a composite structure. For example, in order to form a vacuum cavity, a cover layer having a sacrificial hole needs to be provided first, and the sacrificial layer below the cover layer is etched through the sacrificial hole; A filling layer is then deposited over the cover layer to seal the sacrificial holes in the cover layer to form a vacuum cavity. The magnetoresistive sensor 11 may be disposed on or in a filling layer, and finally a passivation layer is deposited for protection, so that the magnetoresistive sensor 110 is formed in the composite structure of the diaphragm 120.

For those skilled in the art, the first magnet 150 and the second magnet 160 may be disposed on the diaphragm 120 and the magnetoresistive sensor 110 may be disposed on the first substrate 100. When the diaphragm 120 vibrates, the positions of the first magnet 150 and the second magnet 160 are changed, and the same effect can be achieved, which is not described in detail here.

Whether the magnetoresistive sensor 110 is disposed on the diaphragm 120 or the first substrate 100, a driving device such as a piezoelectric sheet 200 can be disposed on the diaphragm 120, and the piezoelectric sheet 200 can be passed by a person skilled in the art. The well-known manner is formed at the corresponding position of the diaphragm 120, and the electrical signal of the piezoelectric sheet 200 can be drawn out through the conductive portion, and a corresponding external pad is formed at an outer position of the diaphragm 120.

When the magnetoresistive sensor 110 deviates from the center line positions of the first magnet 150 and the second magnet 160, a DC bias voltage can be applied to the piezoelectric sheet 200, and the piezoelectric sheet 120 can be used to drive the diaphragm 120 to generate a certain displacement, and finally make the magnetic The resistance sensor 110 is located on the centerline position of the first magnet 150 and the second magnet 160, thereby ensuring the sensitivity of the sensor.

Example 2

Referring to FIG. 4, different from Embodiment 1, in this embodiment, the first substrate 100 has a hollow cavity 101 communicating with the outside, and further includes a cantilever 171 spaced from the diaphragm 120, an edge of the diaphragm 120 and The end of the cantilever 171 is directly or indirectly connected to the first substrate 100, so that the diaphragm 120 and the main body portion of the cantilever 171 are suspended above the cavity 101 in the first substrate 100.

The cantilever 171 and the diaphragm 120 are separated by a first spacer. The height of the first spacer is the initial gap between the diaphragm 120 and the cantilever 171. Because the structure of the back plate is abandoned, the structural design of the cantilever 171 is adopted, so that the diaphragm 120, the first spacer, and the cantilever 171 form an open cavity, and the cantilever 171 will not seal the cavity. This is completely different from the traditional sealed cavity enclosed between the diaphragm and the back plate.

Because of adopting this open design, when the diaphragm 120 vibrates, the airflow can flow smoothly, there will be no gap due to air viscosity or air flow resistance in the perforation, which can greatly improve the signal and noise of the microphone. ratio. The first magnet 150, the second magnet 160, and the magnetoresistive sensor 110 can be selectively disposed on the diaphragm 120 and the cantilever 171.

The microphone of the present invention may be an arrangement manner of the diaphragm above, cantilever down, or an arrangement manner of the diaphragm below, and the diaphragm above.

In a specific embodiment, the cantilever 171 is located below the diaphragm 120. Referring to FIG. 4, one end of the cantilever 171 may be connected to the first substrate 100, and the other end may extend toward the axis direction of the hollow cavity and be suspended above the hollow cavity. The edge of the diaphragm 120 is supported above the cantilever 171 through the first spacer 140.

Optionally, one cantilever 171 may be provided, one end of which is directly or indirectly connected to the first substrate 100, and the other end extends toward the center of the diaphragm 120 and is suspended. Two cantilever arms 171 can also be provided, and they can be arranged according to specific needs. Optionally, the cantilever 171 spans the hollow cavity, and both ends thereof are directly or indirectly connected to the first substrate 100.

Optionally, in order to ensure the stability of the cantilever 171, a support portion for supporting the cantilever 171 is formed in the hollow cavity of the first substrate 100, and the shape and size of the support portion are matched with the cantilever 171, so that the support portion will not face the The hollow cavity of the first substrate 100 causes excessive blocking. The support portion and the first substrate 100 may be integrated. When the hollow cavity is formed on the first substrate 100 by etching or a method well known to those skilled in the art, the structure of the support portion is formed at the same time.

The first magnet 150 and the second magnet 160 may be disposed on the cantilever 171, and the magnetoresistive sensor 110 may be disposed on the diaphragm 120. When the diaphragm 120 vibrates, the position of the driving magnetoresistive sensor 110 changes.

The first magnet 150 and the second magnet 160 may be provided on the diaphragm 120, and the magnetoresistive sensor 110 may be provided on the cantilever 171. When the diaphragm 120 vibrates, the positions of the first magnet 150 and the second magnet 160 are changed, which is not described in detail here.

Whether the magnetoresistive sensor 110 is disposed on the diaphragm 120 or the cantilever 171, a driving device such as the piezoelectric sheet 200 may be disposed on the diaphragm 120, and the piezoelectric sheet 200 may be well-known by those skilled in the art. The method is formed at the corresponding position of the diaphragm 120, and the electrical signal of the piezoelectric sheet 200 can be drawn out through the conductive portion, and a corresponding external pad is formed at an outer position of the diaphragm 120. When the magnetoresistive sensor 110 deviates from the center line positions of the first magnet 150 and the second magnet 160, a DC bias voltage can be applied to the piezoelectric sheet 200, and the piezoelectric sheet 120 can be used to drive the diaphragm 120 to generate a certain displacement, and finally make the magnetic The resistance sensor 110 is located on the centerline position of the first magnet 150 and the second magnet 160, thereby ensuring the sensitivity of the sensor.

For those skilled in the art, the piezoelectric sheet 200 can also be set on the cantilever 171, and the relative position between the magnetoresistive sensor 110 and the first magnet 150 and the second magnet 160 can be calibrated by changing the position of the cantilever 171. Not specific here

Alternatively, a piezoelectric sheet is provided on the diaphragm 120 and the cantilever 171 at the same time, and the relative positions between the magnetoresistive sensor 110 and the first magnet 150 and the second magnet 160 are calibrated by the two piezoelectric sheets. Specific description.

Example 3

Referring to FIG. 1, the present invention provides a microphone including a first substrate 1 and a diaphragm 2 supported above the first substrate 1 through a first spacer 6. The first substrate 1 and the first spacer 6 The diaphragm 2 surrounds a vacuum chamber 5.

The first substrate 1 of the present invention may be made of single crystal silicon or other materials well known to those skilled in the art, and the first spacer 6 and the first spacer 6 may be formed by layer-by-layer deposition, patterning, and sacrificial processes. The diaphragm 2 supported on the first substrate 1 and the vacuum chamber 5 can be sealed, for example, by a low pressure plasma enhanced chemical vapor deposition (PECVD) at 200-350 ° C. This MEMS process belongs to the common knowledge of those skilled in the art and will not be described in detail here. The vacuum chamber 5 is preferably less than 1 kPa, which makes the residual gas viscosity in the vacuum chamber 5 much lower than the air viscosity at standard pressure.

A first cantilever 3 is also provided above the diaphragm 2, and the first cantilever 3 and the diaphragm 2 are separated by a second spacer (no reference numeral is added in FIG. 1). The height of the second spacer is the diaphragm. The initial gap between 2 and the first cantilever 3. The diaphragm 2, the second spacer portion, and the first cantilever 3 form an open type cavity, so that the first cantilever 3 does not seal the cavity.

One end of the first cantilever 3 may be connected to the second spacer, and the other end may extend toward the axis direction of the receiving cavity and be suspended above the receiving cavity. Optionally, one of the first cantilever arms 3 may be provided, one end of which is directly or indirectly connected to the second spacer, and the other end extends toward the center of the diaphragm 2 and is suspended. The first cantilever 3 can also be provided with two, and can be arranged according to specific needs. Optionally, the first cantilever 3 spans the cavity, and both ends thereof are directly or indirectly connected to the second spacer.

In order to increase the sensitivity of the microphone, the microphone may employ a highly sensitive detection member. In a specific embodiment of the present invention, the high-sensitivity detection member may use a magnetoresistive sensor 8 that outputs an electrical signal according to a change in a magnetic field, such as a giant magnetoresistive sensor (GMR) or a tunnel magnetoresistive sensor (TMR). By using a high-sensitivity magnetoresistive sensor 8 to obtain the detected electrical signal, the influence of the diaphragm stiffness on the overall sensitivity of the microphone can be compensated, and the acoustic performance of the thin and light microphone is guaranteed.

Referring to FIG. 1, a first magnet 7 is provided on the first substrate 1 at a position on the side of the vacuum chamber 5, and a second magnet 9 is provided on the first cantilever 3. The first magnet 7 and the second magnet 9 may be used. Magnetic film, the magnetic film may be directly made of magnetic material, or the film may be magnetized after the film is formed. In a specific embodiment of the present invention, the magnetic thin film may be made of CoCrPt or CoPt.

The first magnet 7 can be formed on the first substrate 1 by deposition or other means known to those skilled in the art. Specifically, at the time of fabrication, an insulating layer 10 can be deposited on the first substrate 1 first, and then a first magnet 7 can be formed by a deposition and patterning process. In order to protect the first magnet 7, it can also be deposited on the insulating layer 10 A layer of passivation layer 11 covering the first magnet 7. The insulating layer and the passivation layer can be made of materials well known to those skilled in the art, and will not be described in detail here.

The second magnet 9 can also be formed on the first cantilever 3 in the same manner, which will not be described in detail here.

The first magnet 7 and the second magnet 9 are arranged on the first substrate 1 and the first cantilever 3 in a manner that the magnetic pole directions are opposite to each other. Referring to the view direction of FIG. 1, when the left side of the first magnet 7 is N-pole and the right side is S-pole, the left side of the second magnet 9 is S-pole and the right side is N-pole; vice versa.

Referring to the embodiment of FIG. 1, the magnetoresistive sensor 8 is disposed on the diaphragm 2. In order to lead out the electrical signals of the magnetoresistive sensor 2, a lead portion may be provided on the diaphragm 2, and one end of the lead portion is connected to the magnetoresistive sensor 8. The other end extends to the position of the first spacer 6 on the diaphragm 2, and a pad 15 is formed on the outside of the diaphragm 2. It should be noted that the lead portion may pass through to the outside of the first substrate 1 and form a pad, which is not described in detail here.

When the diaphragm 2 is subjected to external sound pressure, the diaphragm 2 is deformed in the direction of the first substrate 1. At this time, the magnetoresistive sensor 8 on the diaphragm 2 is close to the first magnet 7 and away from the second magnet 9, so that The magnetoresistive sensor 8 can sense the change of the common magnetic field of the first magnet 7 and the second magnet 9 and output a changed electric signal, thereby realizing the conversion of acoustic electricity.

Preferably, the first magnet 7 and the second magnet 9 are preferably symmetrical with respect to the magnetoresistive sensor 8, and this position of the magnetoresistive sensor 8 is the initial position.

The magnetoresistive sensor 8 may be disposed on a side of the diaphragm 2 away from the vacuum chamber 5, or on the side of the diaphragm 2 near the vacuum chamber 5, or the magnetoresistive sensor 8 may be disposed in the diaphragm 2. In an optional embodiment of the present invention, the diaphragm 2 may adopt a composite structure. For example, in order to form a vacuum cavity, a cover layer 12 having a sacrificial hole needs to be provided first, and the sacrificial layer below the cover layer 12 is etched through the sacrificial hole. Afterwards, a filling layer 13 is deposited on the cover layer 12 to close the sacrificial holes on the cover layer 12 to form a vacuum cavity. The magnetoresistive sensor 8 may be disposed on or in the filling layer 13, and finally a passivation layer 14 is deposited for protection. The magnetoresistive sensor 8 is formed in the composite structure of the diaphragm 120 and is located at the center of the first magnet 7 and the second magnet 9.

When the left side of the first magnet 7 is N pole, the right side is S pole, and the left side of the second magnet 9 is S pole, and the right side is N pole, the magnetic field directions of the first magnet 7 and the second magnet 9 are both From N pole to S pole. This vertical arrangement makes the magnetic field directions of the first magnet 7 and the second magnet 9 opposite to each other and the magnetic field strengths are approximately the same at the positions of the centers of the first magnet 7 and the second magnet 9.

When the magnetoresistive sensor 8 vibrates with the diaphragm 2, the magnetoresistive sensor 8 will use the center position as an initial position to perform up and down vibration. At this initial position, the magnetoresistive sensor 8 is subjected to the same magnitude of the magnetic field of the two magnets, and their directions are opposite. For example, when the diaphragm 2 is deformed toward the cantilever 3, the magnetoresistive sensor 8 is closer to the first magnet 7 and away from the second magnet 9. According to the characteristics of the magnet, it can be known that the magnetoresistive sensor 8 is more affected by the first magnet 7 than it is. Affected by the second magnet 8; vice versa.

Since the magnetoresistive sensor 8 is subjected to the action of two magnets at the same time, the two magnets cooperate to reduce the strength of the entire magnetic field, and increase the sensitivity of the magnetic field change within the linear range of the magnetoresistive sensor 8, and finally increase the magnetic resistance Detection sensitivity of the sensor 8.

Fig. 5a shows a coordinate diagram of the distribution of two magnets and a magnetoresistive sensor in the embodiment shown in Fig. 1. In this coordinate diagram, the origin position is located at the center position of the lower magnet. Fig. 5b shows a simulation diagram of a magnetic field distribution in the embodiment shown in Fig. 1. The size of both magnets is 2μm * 1μm * 0.1μm, and the distance between the two magnets is 2μm. The abscissa in FIG. 5b represents the vertical distance z (m) of the magnetoresistive sensor with respect to the center position of the lower magnet, and the ordinate represents the magnetic field strength Bx (T) and the magnetic field change gradient dB / dz (T / m). Line a2 in the figure represents the change curve of Bx (T) with z (m), and line b2 represents the change curve of the magnetic field change gradient dB / dz (T / m) with z (m).

The magnetic field strength of the initial position of the magnetoresistive sensor 8 is 0, that is, the position where Bx (T) in line a2 is 0, and at this time, z (m) is about 1 μm (1.0E-06), that is, the initial position of the magnetoresistive sensor 8 is The magnetoresistive sensor 8 is located at a distance of 1 μm from the center of the lower magnet. At this initial position, the value of the line b2 is approximately 1.6 * 10 ⁶ T / m. That is, the gradient of magnetic field change at this position is 1.6 * 10 ⁶ T / m. Compared with the traditional single magnet structure, the sensitivity to magnetic field changes is greatly improved. In addition, the area of the line b2 on the left and right sides of the initial position is relatively flat, which ensures that the magnetoresistive sensor 8 can be located in its linear detection area. In the microphone of the present invention, a vacuum cavity is enclosed between the diaphragm 2 and the first substrate 1. The viscosity of the air in the vacuum cavity is much lower than the air viscosity in the ambient pressure, so that the acoustic resistance can reduce the vibration of the diaphragm 2 Effect, improving the signal-to-noise ratio of the microphone. In addition, since the MEMS microphone of this structure does not require a large-capacity back cavity, the overall size of the MEMS microphone can be greatly reduced, and the reliability of the microphone is enhanced.

The microphone of the present invention can be combined with a bonding process in addition to being manufactured by a surface micromachining or bulk silicon micromachining process. Referring to FIG. 1, the first cantilever 3 may be disposed on the second substrate 4 and combined with the diaphragm 2 through a bonding process, which is not described in detail here.

For calibration, the piezoelectric sheet 16 may be disposed on the first cantilever 3, and the piezoelectric sheet 16 may be formed at a corresponding position of the first cantilever 3 in a manner known to those skilled in the art, and the piezoelectric sheet may be formed by a conductive part An electrical signal of 16 is drawn, and a corresponding external pad is formed on the outer position of the first cantilever 3. When the magnetoresistive sensor 8 deviates from the center positions of the first magnet 7 and the second magnet 9, a DC bias voltage can be applied to the piezoelectric sheet 16 to drive the first cantilever 3 to a certain displacement through the piezoelectric sheet, thereby By changing the position of the second magnet 9, the magnetoresistive sensor 8 is finally located at the center of the first magnet 7 and the second magnet 9, thereby ensuring the sensitivity of the sensor.

For those skilled in the art, it is also possible to set the piezoelectric sheet 16 on the diaphragm 2 and adjust the position between the magnetoresistive sensor 8 and the first magnet 7 and the second magnet 9 by changing the position of the diaphragm 2. position.

Alternatively, a piezoelectric sheet 16 is provided on the first cantilever 3 and the diaphragm 2 at the same time, and the relative positions between the magnetoresistive sensor 8 and the first magnet 7 and the second magnet 9 are calibrated by the two piezoelectric sheets. It will not be described in detail here.

Example 4

Referring to FIG. 2, different from Embodiment 3, in this embodiment, the first substrate 1 has a hollow cavity 16 communicating with the outside, and further includes a second cantilever located below the diaphragm 2 and separated from the diaphragm 2. 17. The edge of the diaphragm 2 and the end of the second cantilever 17 are directly or indirectly connected to the first substrate 1, so that the main part of the diaphragm 2 and the second cantilever 17 is suspended in the cavity 16 of the first substrate 1. Above.

The second cantilever 17 and the diaphragm 2 are separated by a first spacer. The height of the first spacer is the initial gap between the diaphragm 2 and the second cantilever 17. Because the structure of the back plate is abandoned, the structural design of the second cantilever 17 is adopted, so that the diaphragm 2 and the first spacer and the second cantilever 17 form an open cavity, and the second cantilever 17 will not face each other. This cavity creates a seal, which is completely different from the traditionally sealed cavity enclosed between the conventional diaphragm and the back plate.

Because of adopting this open design, when the diaphragm 2 vibrates, the airflow can flow smoothly, there will be no gap due to air viscosity or air flow resistance in the perforation, which can greatly improve the signal and noise of the microphone. ratio.

One end of the second cantilever 17 may be connected to the first substrate 1, and the other end may extend toward the axis direction of the hollow cavity and be suspended above the hollow cavity. The edge of the diaphragm 2 is supported above the second cantilever 17 through the first spacer.

Optionally, one of the second cantilever arms 17 may be provided, one end of which is directly or indirectly connected to the first substrate 1, and the other end extends toward the center of the diaphragm 2 and is suspended. The second cantilever 17 can also be provided with two, and can be arranged according to specific needs. Optionally, the second cantilever 17 spans the hollow cavity, and both ends thereof are directly or indirectly connected to the first substrate 1.

Optionally, in order to ensure the stability of the second cantilever 17, a support portion for supporting the second cantilever 17 is formed in the hollow cavity of the first substrate 1, and the shape and size of the support portion match the second cantilever 17. Therefore, the support portion does not cause excessive blocking to the hollow cavity of the first substrate 1. The support portion and the first substrate 1 may be integrated. When the hollow cavity is formed on the first substrate 1 by etching or a method well known to those skilled in the art, the structure of the support portion is formed at the same time.

The first magnet 7 may be disposed on the second cantilever arm 17 to cooperate with the second magnet 9 on the first cantilever arm 3, which is not described in detail here.

For calibration, the piezoelectric sheet 16 may be disposed on the second cantilever 17. The piezoelectric sheet 16 may be formed at a corresponding position of the second cantilever 17 in a manner well known to those skilled in the art, and the piezoelectric sheet may be formed by a conductive portion. 16 electrical signals. When the magnetoresistive sensor 8 deviates from the center positions of the first magnet 7 and the second magnet 9, a DC bias voltage can be applied to the piezoelectric sheet 16 to drive the second cantilever 17 to a certain displacement through the piezoelectric sheet, thereby By changing the position of the first magnet 7, the magnetoresistive sensor 8 is finally located at the center position of the first magnet 7 and the second magnet 9, thereby ensuring the sensitivity of the sensor.

For those skilled in the art, the piezoelectric sheet 16 can also be set on the diaphragm 2 or the first cantilever 3, and the

magnetoresistive sensors

8 and 8 can be calibrated by changing the position of the diaphragm 2 or changing the position of the first cantilever 3. The relative positions between the first magnet 7 and the second magnet 9.

Alternatively, a piezoelectric sheet 16 may be selectively provided on the first cantilever 3, the diaphragm 2, and the second cantilever 17, and the two or three piezoelectric sheets may be used to calibrate the magnetoresistive sensor 8 and the first magnet 7. The relative position between the two magnets 9 is not described in detail here.

Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present invention. The scope of the invention is defined by the appended claims.

Claims

A sensor is characterized in that it comprises a first substrate and a diaphragm supported above the first substrate through a first spacer, and further comprises a detection structure for outputting an electrical signal characterizing the deformation of the diaphragm; the detection structure Including a first magnet, a second magnet, and a magnetoresistive sensor disposed in a common magnetic field formed by the first magnet and the second magnet; in an initial position, the magnetoresistive sensor is located in a magnetic field direction of the first magnet and a magnetic field of the second magnet In opposite directions; the magnetoresistive sensor is configured to sense a change in a common magnetic field of the first magnet and the second magnet and output a changed electrical signal during the vibration of the diaphragm;

It also includes a driving device for adjusting the mutual position between the magnetoresistive sensor, the first magnet and the second magnet.
The sensor according to claim 1, wherein the driving device is a piezoelectric sheet or an electrode sheet for providing an electrostatic force.
The sensor according to claim 1 or 2, wherein at the initial position, the magnetoresistive sensor receives the magnetic field of the first magnet, and the magnetic field of the magnetoresistive sensor has the same magnitude as the magnetic field of the second magnet, and the directions are opposite.
The sensor according to any one of claims 1 to 3, wherein the first substrate, the first spacer, and the diaphragm surround a vacuum cavity; wherein the static deflection distance of the diaphragm under atmospheric pressure Less than the distance between the diaphragm and the first substrate; the driving device is arranged on the diaphragm;

The first magnet and the second magnet are sequentially arranged horizontally on the diaphragm in the same direction of the magnetic poles, and the magnetoresistive sensor is disposed on a first substrate at a position corresponding to the first magnet and the second magnet;

Alternatively, the first magnet and the second magnet are sequentially horizontally arranged on the first substrate in the same manner as the directions of the magnetic poles, and the magnetoresistive sensor is disposed on the diaphragm corresponding to the first magnet and the second magnet.
The sensor according to any one of claims 1 to 4, wherein the first substrate has a hollow cavity in communication with the outside, and further comprises a cantilever spaced from the diaphragm, and the cantilever and the diaphragm are suspended It is above the cavity in the first substrate, and the diaphragm and the first spacer and the substrate form an open type cavity; the driving device is arranged on the diaphragm and / or on a cantilever;

The first magnet and the second magnet are sequentially arranged horizontally on the diaphragm in the same direction of the magnetic poles, and the magnetoresistive sensor is disposed on a cantilever corresponding to the first magnet and the second magnet;

Alternatively, the first magnet and the second magnet are sequentially horizontally arranged on the cantilever in the same direction as the magnetic pole direction, and the magnetoresistive sensor is disposed on the diaphragm corresponding to the first magnet and the second magnet. .
The sensor according to any one of claims 1 to 5, characterized in that the first substrate, the first spacer, and the diaphragm surround a vacuum cavity; wherein the static deflection distance of the diaphragm under atmospheric pressure Less than the distance between the diaphragm and the first substrate;

It further includes a cantilever spaced from the diaphragm through the second spacer, and the diaphragm and the second spacer and the cantilever surround an open cavity; the driving device is arranged on the diaphragm and / or the cantilever;

The magnetoresistive sensor is disposed on a diaphragm, the first magnet and the second magnet are respectively disposed on a first substrate and a cantilever located on both sides of the diaphragm, and the first magnet and the second magnet have opposite magnetic pole directions. Layout.
The sensor according to any one of claims 1 to 6, wherein the first magnet and the second magnet are symmetrical with respect to the magnetoresistive sensor.
The sensor according to any one of claims 1 to 7, wherein the first substrate has a hollow cavity communicating with the outside, and a first cantilever and a second cantilever are respectively provided on opposite sides of the diaphragm. The diaphragm is spaced apart from the first cantilever and the second cantilever, and both sides of the diaphragm are in communication with the outside; the driving device is arranged on the diaphragm and / or the first cantilever and / or the second cantilever ;

The magnetoresistive sensor is disposed on the diaphragm, the first magnet and the second magnet are disposed on the first cantilever and the second cantilever, respectively, and the first magnet and the second magnet are arranged in opposite directions of the magnetic poles.
The sensor according to any one of claims 1 to 8, wherein the first magnet and the second magnet are magnetized films.
The sensor according to any one of claims 1 to 9, wherein the sensor is a microphone, a pressure sensor, or a displacement sensor.