CN118843052A - MEMS structures and sensors - Google Patents

Abstract

The present application discloses a MEMS structure and a sensor. The MEMS structure includes a first diaphragm, a second diaphragm and a third diaphragm which are stacked in sequence, an acoustic sealing cavity is formed between the first diaphragm and the third diaphragm; a first back plate which is stacked between the first diaphragm and the second diaphragm, and a second back plate which is stacked between the second diaphragm and the third diaphragm; wherein at least two of the first diaphragm, the second diaphragm and the third diaphragm are respectively provided with a plurality of first through holes which are connected to the acoustic sealing cavity, and the first through holes are used to allow gas to pass through and can block solids and liquids. The MEMS structure provided by the present application improves the service life of the device while ensuring the acoustic performance of the device.

Description

MEMS structures and sensors

Technical Field

The present application relates to the technical field of electronic equipment, and more specifically, to a MEMS structure and a sensor.

Background Art

In the prior art, two diaphragms are usually connected by a support column to improve the vibration consistency of each diaphragm. However, the two ends of the support column are usually connected to the diaphragm by bonding, which makes it easy for the connection to fail when the diaphragm vibrates, resulting in a decrease in its acoustic performance and a shortened service life of the device.

Summary of the invention

One object of the present application is to provide a new technical solution for MEMS structures and sensors.

According to a first aspect of the present application, a MEMS structure is provided, comprising:

A first diaphragm, a second diaphragm and a third diaphragm are stacked in sequence, and an acoustic sealing cavity is formed between the first diaphragm and the third diaphragm;

A first back plate stacked between the first diaphragm and the second diaphragm, and a second back plate stacked between the second diaphragm and the third diaphragm;

At least two of the first diaphragm, the second diaphragm and the third diaphragm are respectively provided with a plurality of first through holes connected to the acoustic sealing cavity, and the first through holes are used to allow gas to pass through and can block solids and liquids.

Optionally, the aperture of the first through hole is 0.1 um to 0.5 um.

Optionally, the distance between two adjacent first through holes is 10 um to 50 um.

Optionally, the at least two diaphragms include the second diaphragm.

Optionally, an aperture ratio of the first through hole on the second diaphragm is greater than an aperture ratio of the first through hole on the first diaphragm and/or the second diaphragm.

Optionally, a plurality of second through holes are respectively arranged on the first back plate and the second back plate;

The position of the first through hole on the second diaphragm is staggered with the position of the second through hole, and both the first diaphragm and the third diaphragm are used to connect high-impedance electrical signals.

Optionally, a plurality of second through holes are respectively arranged on the first back plate and the second back plate;

The position of the first through hole on the second diaphragm is opposite to the position of the second through hole, and the first back plate and the second back plate are both used for connecting high-impedance electrical signals.

Optionally, the MEMS structure further includes a third through hole, and the first diaphragm, the second diaphragm and the third diaphragm are all peripherally clamped stress membranes;

The third through hole passes through the first diaphragm, the first back plate, the second diaphragm, the second back plate and the center position of the third diaphragm in sequence, and is not connected to the acoustic sealing cavity.

Optionally, a substrate is provided on a side of the third diaphragm away from the second diaphragm, and the first through hole is not provided on the third diaphragm.

According to a second aspect of the present application, a sensor is provided, comprising: the MEMS structure described in the first aspect.

According to one embodiment of the present application, the acoustic performance of the MEMS structure is improved by providing three diaphragms and forming an acoustically sealed cavity between the diaphragms, and consistent vibration of the three diaphragms is achieved by providing a plurality of first through holes on at least two diaphragms, thereby improving the service life of the device while ensuring the acoustic performance of the device.

Other features and advantages of the present application will become apparent from the following detailed description of exemplary embodiments of the present application 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 application and, together with the description, serve to explain the principles of the application.

FIG. 1 is one of schematic diagrams of a MEMS structure provided in the present application.

FIG. 2 is a second schematic diagram of a MEMS structure provided by the present application.

FIG. 3 is a third schematic diagram of a MEMS structure provided by the present application.

FIG. 4 is a fourth schematic diagram of a MEMS structure provided by the present application.

FIG. 5 is a fifth schematic diagram of a MEMS structure provided by the present application.

FIG. 6 is one of the electrical connection schematic diagrams of a MEMS structure provided in the present application.

FIG. 7 is a second electrical connection schematic diagram of a MEMS structure provided by the present application.

FIG. 8 is a third electrical connection schematic diagram of a MEMS structure provided in the present application.

FIG. 9 is a fourth electrical connection schematic diagram of a MEMS structure provided in the present application.

Description of reference numerals:

1. First diaphragm; 2. Second diaphragm; 3. Third diaphragm; 4. First back plate; 5. Second back plate; 6. First through hole; 7. Second through hole; 8. Third through hole; 9. Insulator; 10. Substrate; 11. Acoustic sealing chamber.

DETAILED DESCRIPTION

Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, 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 application.

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

Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

As shown in Figures 1 to 9, according to the first aspect of the present application, a MEMS (Micro-Electro-Mechanical Systems) structure is provided, including: a first diaphragm 1, a second diaphragm 2 and a third diaphragm 3 stacked in sequence, with an acoustic sealing cavity 11 formed between the first diaphragm 1 and the third diaphragm 3; a first back pole plate 4 stacked between the first diaphragm 1 and the second diaphragm 2, and a second back pole plate 5 stacked between the second diaphragm 2 and the third diaphragm 3; wherein at least two of the first diaphragm 1, the second diaphragm 2 and the third diaphragm 3 are respectively provided with a plurality of first through holes 6 connected to the acoustic sealing cavity 11, and the first through holes 6 are used to allow gas to pass through and can block solids and liquids.

Specifically, in this embodiment, the MEMS structure includes three diaphragms and two back plates, namely, from top to bottom, the first diaphragm 1, the first back plate 4, the second diaphragm 2, the second back plate 5 and the third diaphragm 3. Among them, the four sides of each diaphragm and the back plate are fixed on the insulating member 9, which, on the one hand, realizes electrical mutual insulation, and on the other hand, supports and spaces each device, so that a set spacing is left between the first diaphragm 1, the first back plate 4, the second diaphragm 2, the second back plate 5 and the third diaphragm 3 to realize the acoustic function of the device. Among them, the area between the first diaphragm 1 and the third diaphragm 3 is an acoustic sealing cavity 11, that is, the area between the first diaphragm 1 and the second diaphragm 2, and the area between the second diaphragm 2 and the third diaphragm 3 are all acoustic sealing cavities 11.

In practical applications, the above-mentioned MEMS structure adopts the vibration form of three diaphragms, and at least two diaphragms are provided with multiple first through holes 6, and the first through holes 6 can connect the acoustic sealing cavity 11 and the external air, that is, it can allow gas to pass through the first through holes 6, so that multiple diaphragms can vibrate in coordination, achieve a wider range of frequency response and a larger acoustic effective area, and can provide more signal sources, such as using differential signal processing to eliminate common mode noise, improve signal-to-noise ratio and sound quality, etc., significantly improving the acoustic performance of the device. Among them, the first through hole 6 can also block external solid debris and liquids such as water vapor, while ensuring the acoustic performance, improving the protection ability of the device.

In the above embodiment, at least two diaphragms are provided with a plurality of first through holes 6, for example, the first diaphragm 1 and the second diaphragm 2 are provided with a plurality of first through holes 6 respectively, and the third diaphragm 3 is not provided, refer to FIG2; or the first diaphragm 1 and the third diaphragm 3 are provided with a plurality of first through holes 6 respectively, and the second diaphragm 2 is not provided, refer to FIG3; or the second diaphragm 2 and the third diaphragm 3 are provided with a plurality of first through holes 6 respectively, and the first diaphragm 1 is not provided; and or the first diaphragm 1, the second diaphragm 2 and the third diaphragm 3 are provided with a plurality of first through holes 6 respectively, refer to FIG1, FIG4 and FIG5. Among them, the diaphragm can be made of low stress polysilicon (such as 10MPa to 30MPa) or a composite film composed of thin silicon nitride (such as thickness <0.1um); the back plate can be made of a composite film formed by high stress thick silicon nitride (such as stress>200MPa, thickness>0.3um) and conductive polysilicon or metal.

A plurality of first through holes 6 can be evenly distributed on the diaphragm, and the size of the aperture can generally be set to 0.01um to 1um, so as to meet the purpose of the first through holes 6 allowing gas to pass through and blocking solids and liquids from passing through. In addition, the distance between two adjacent first through holes 6 can be set to 5um to 100um, so as to meet the circulation requirements of the airflow without affecting the vibration performance of the diaphragm. In addition, the shape of the first through hole 6 can be polygonal or circular, preferably hexagonal. Through the setting of the first through hole 6, the release of the MEMS device is completed, so that the acoustic sealing cavity 11 can communicate with the outside world and balance the atmospheric pressure when the three diaphragms are working, and the acoustic performance of the MEMS device is not affected, and the risk of structural failure is avoided, thereby ensuring the service life of the device.

In practical applications, MEMS devices are usually connected to ASIC (Application Specific Integrated Circuit) devices to achieve specific acoustic performance. For example, in one embodiment, a plurality of first through holes 6 are respectively provided on the first diaphragm 1, the second diaphragm 2 and the third diaphragm 3 in the MEMS device, which are used to balance the acoustic sealing cavity 11 with the external air pressure, and the substrate 10 is provided on the outside of the third diaphragm 3, and the sound signal originates from the side of the substrate 10. When the circuit is connected to the ASIC device, as shown in Figures 6 to 9, Vb is the electrostatic bias, Gnd is the ground, and Vo/Vo+/Vo- are high-impedance electrical signal output nodes connected to the ASIC device.

It can be seen that, compared with the dual-diaphragm MEMS structure with a primary differential signal, the triple-diaphragm structure provided in the present application has a secondary differential structure, so the bias ratio (Vb/Vp, where Vp is the single-ended pull-in voltage, i.e., only one diaphragm and one adjacent back plate are voltaged) that can be added can be higher (e.g., 100-130%), so as to improve the sensitivity and signal-to-noise ratio of the MEMS structure. An acoustically sealed cavity 11 is formed between the upper and lower diaphragms (the first diaphragm 1 and the third diaphragm 3), so that the sound signal will form a pressure difference in the diaphragm system (i.e., the lower surface of the third diaphragm 3 and the upper surface of the first diaphragm 1) without loss.

Since the volume of air in the acoustic sealing cavity 11 is extremely small, its acoustic compliance can be ignored, that is, since the elastic constant of the air spring is very large, the air is incompressible and can only flow, so the three diaphragms can only move together within the acoustic frequency range. This not only ensures the normal operation of the acoustic device, but also naturally protects the diaphragm on the outside of the back plate, ensuring that it will not be separated from the high-strength back plate system due to acoustic/mechanical shock or high-pressure airflow during extreme applications or reliability testing, and "fly out" of the device structure to cause failure.

As shown in FIGS. 6 to 8, a dual bias voltage (i.e., positive and negative Vb) setting is adopted, and the third diaphragm 3 closest to the substrate 10 and the first diaphragm 1 having parasitic capacitance with the package tube shell are biased at a fixed potential, which can eliminate the adverse effects of parasitic capacitance as much as possible, and may also be beneficial to shielding external electromagnetic interference. As shown in FIG. 9, a single bias voltage Vb setting is adopted, and the effective electrode area of the third diaphragm 3 is completely placed in the back hole BH area in the layout design, and the parasitic capacitance is minimized, and a differential output signal like SDM can also be formed.

Optionally, the diameter of the first through hole 6 is 0.1 um to 0.5 um.

Specifically, in practical applications, the smaller the aperture of the first through hole 6, the more its acoustic performance can be improved, but too small an aperture will lead to processing difficulties, which will greatly increase the production cost. An aperture that is too large will affect the vibration of the diaphragm, resulting in a decrease in acoustic performance. For example, when the aperture is 0.5um to 1um, the acoustic performance of the MEMS device in the low-frequency response drops significantly, which is manifested in a large signal-to-noise ratio. Therefore, the present application sets the aperture of the first through hole 6 to 0.1um to 0.5um, which not only ensures that the production cost will not increase significantly, but also ensures the acoustic performance. Preferably, the aperture of the first through hole 6 is 0.2um to 0.4um, which can further take into account the cost and acoustic performance of the MEMS structure.

Optionally, referring to FIG. 1 to FIG. 3 , the distance between two adjacent first through holes 6 is 10 um to 50 um.

Specifically, in practical applications, if the distance between two adjacent first through holes 6 is too large, it will lead to greater manufacturing difficulties and affect the production yield of the device. For example, in the commonly used MEMS production, the through holes on the diaphragm can be obtained by chemical corrosion. If the distance between the two through holes is too large, the corrosion time of the corrosive liquid will increase, which will cause some metal parts in the MEMS device to corrode, affecting the final product quality. Therefore, the present application sets the distance between two adjacent first through holes 6 at 10um to 50um, which can further ensure the product yield of the device and reduce production costs. Preferably, the distance between two adjacent first through holes 6 is 15um to 30um. Among them, the distance between two adjacent first through holes 6 can also be understood as the distance between a first through hole 6 and each of the surrounding first through holes 6, which can be set within the above range.

Optionally, as shown in FIG. 1 and FIG. 2 , the at least two diaphragms include the second diaphragm 2 .

Specifically, at least two diaphragms include a second diaphragm 2, which means that a plurality of first through holes 6 are arranged on at least the first diaphragm 1 and the second diaphragm 2, or a plurality of first through holes 6 are arranged on at least the second diaphragm 2 and the third diaphragm 3, so that when a plurality of first through holes 6 are arranged on only two diaphragms, the diaphragm without the first through holes 6 can be located on the outside of the MEMS structure, that is, the first through holes 6 are not arranged on the first diaphragm 1 or the third diaphragm 3, that is, only one side of the MEMS device is connected to the outside, which can prevent external debris from entering the acoustic sealing cavity 11 to a greater extent, thereby further improving the acoustic performance of the product.

Optionally, as shown in FIG. 4 and FIG. 5 , the aperture ratio of the first through hole 6 on the second diaphragm 2 is greater than the aperture ratio of the first through hole 6 on the first diaphragm 1 and/or the second diaphragm 2 .

Specifically, the porosity of the first through hole 6 refers to the ratio of the sum of the areas of all the first through holes 6 to the area of the diaphragm where they are located. Setting the porosity of the first through holes 6 on the second diaphragm 2 to be greater than the porosity of the first through holes 6 on the first diaphragm 1 and/or the second diaphragm 2 can balance the air pressure on both sides of the second diaphragm 2 and further improve the coordinated vibration effect of the three diaphragms. In practical applications, the porosity on the second diaphragm 2 can be set to 50% to 90%, preferably 60% to 80%. Among them, the size of the porosity can be achieved by adjusting the aperture of the first through hole 6 or the number of the first through holes 6, which can be designed according to actual needs, and the present application does not impose any restrictions on this.

Optionally, as shown in Figure 4, a plurality of second through holes 7 are respectively arranged on the first back pole plate 4 and the second back pole plate 5; the positions of the first through holes 6 on the second diaphragm 2 are staggered with the positions of the second through holes 7, and the first diaphragm 1 and the third diaphragm 3 are both used to connect high-impedance electrical signals.

Specifically, the second through holes 7 on the first back plate 4 and the second back plate 5 are usually sound holes to ensure the sensitivity and sound quality of the MEMS device, so that it can accurately and clearly capture audio signals. In this embodiment, the multiple second through holes 7 on the first back plate 4 and the second back plate 5 are relatively arranged, that is, the positions are the same, and the positions of the first through holes 6 and the second through holes 7 on the second diaphragm 2 are staggered, so that when the first diaphragm 1 and the third diaphragm 3 are connected to a high-impedance electrical signal, the direct capacitive coupling of the first diaphragm 1, the second diaphragm 2 and the third diaphragm 3 can be eliminated under the premise of greatly reducing the acoustic resistance, thereby improving the acoustic performance.

Optionally, as shown in Figure 5, multiple second through holes 7 are respectively arranged on the first back pole plate 4 and the second back pole plate 5; the position of the first through hole 6 on the second diaphragm 2 is opposite to the position of the second through hole 7, and the first back pole plate 4 and the second back pole plate 5 are both used to connect high-impedance electrical signals.

Specifically, in this embodiment, the multiple second through holes 7 on the first back pole plate 4 and the second back pole plate 5 are relatively arranged, that is, the arrangement positions are the same, and the positions of the first through holes 6 and the second through holes 7 on the second diaphragm 2 are relatively arranged, so that when the first back pole plate 4 and the third back pole plate are connected to a high-impedance electrical signal, the acoustic performance of the MEMS structure can be improved.

Optionally, as shown in Figures 1 to 5, the MEMS structure also includes a third through hole 8, and the first diaphragm 1, the second diaphragm 2 and the third diaphragm 3 are all peripherally fixed stress membranes; the third through hole 8 passes through the center positions of the first diaphragm 1, the first back plate 4, the second diaphragm 2, the second back plate 5 and the third diaphragm 3 in sequence, and is not connected to the acoustic sealing cavity 11.

Specifically, the peripheral fixed stress film has high mechanical sensitivity and high reliability, is easier to miniaturize the chip, and has a simple structure, low process difficulty, and has cost and yield advantages. The third through hole 8 is set as a vent hole of the MEMS structure, which can avoid damage to the diaphragm caused by strong airflow or high sound pressure impact when the MEMS structure is subjected to an air pressure greater than a certain pressure threshold, such as rupture, thereby extending the service life of the device. In this embodiment, the third through hole 8 is set at the center of the diaphragm and the back plate, so that an integral connection is formed at the position with a larger vibration amplitude on the diaphragm, avoiding the risk of damage to the central area of the diaphragm by large vibration, and further improving its service life.

In the above embodiment, the third through hole 8 is not connected to the acoustic sealing cavity 11, so that it can support and connect each diaphragm and the back plate without affecting the acoustic performance of the device.

Optionally, as shown in FIG. 2 , a substrate 10 is disposed on a side of the third diaphragm 3 away from the second diaphragm 2 , and the first through hole 6 is not disposed on the third diaphragm 3 .

Specifically, in this embodiment, a substrate 10 is arranged on the outer side of the third diaphragm 3, and in actual applications, the side of the MEMS structure with the substrate 10 is usually arranged on the outer side of the device, and the first through hole 6 is not arranged on the third diaphragm 3, so that the acoustic sealing cavity 11 can be connected to the outside through the first through hole 6 on the second diaphragm 2 and the first diaphragm 1, and can block most of the debris and water vapor through the third diaphragm 3, thereby improving the service life of the device.

According to a second aspect of the present application, a sensor is provided, comprising: the MEMS structure described in the first aspect.

Specifically, in this embodiment, the sensor adopts the MEMS structure provided in the first aspect, and because of its good acoustic performance and low failure risk of the first through hole 6, the acoustic performance and service life of the sensor are guaranteed, and it is suitable for mass production. The sensor can be a microphone or a speaker, etc., and can also be applied to electronic devices such as mobile phones and computers.

The above embodiments focus on the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. Considering the simplicity of the text, they will not be repeated here.

Although some specific embodiments of the present application have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are only for illustration, not for limiting the scope of the present application. It should be understood by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims (10)

1. A MEMS structure, comprising:

The first vibrating diaphragm, the second vibrating diaphragm and the third vibrating diaphragm are sequentially stacked at intervals, and an acoustic sealing cavity is formed between the first vibrating diaphragm and the third vibrating diaphragm;

a first back electrode plate which is overlapped between the first vibrating diaphragm and the second vibrating diaphragm at intervals, and a second back electrode plate which is overlapped between the second vibrating diaphragm and the third vibrating diaphragm at intervals;

Wherein at least two diaphragms among the first diaphragm, the second diaphragm and the third diaphragm are respectively provided with a plurality of first through holes communicated with the acoustic sealing cavity, the first through hole is used for allowing gas to pass through and can block solid and liquid.

2. The MEMS structure of claim 1 wherein the first via has a pore size of 0.1um to 0.5um.

3. The MEMS structure of claim 1 wherein a distance between two adjacent first vias is between 10um and 50um.

4. The MEMS structure of claim 1 wherein the at least two diaphragms include the second diaphragm.

5. The MEMS structure of claim 4, wherein an opening ratio of the first through hole on the second diaphragm is greater than an opening ratio of the first through hole on the first diaphragm and/or the second diaphragm.

6. The MEMS structure of claim 5 wherein the first and second back plates are each oppositely provided with a plurality of second through holes;

The position of the first through hole on the second vibrating diaphragm is staggered with the position of the second through hole, and the first vibrating diaphragm and the third vibrating diaphragm are both used for connecting high-impedance electric signals.

7. The MEMS structure of claim 5 wherein the first and second back plates are each oppositely provided with a plurality of second through holes;

The position of the first through hole on the second vibrating diaphragm is opposite to the position of the second through hole, and the first back electrode plate and the second back electrode plate are both used for connecting high-impedance electric signals.

8. The MEMS structure of claim 1, further comprising a third through hole, wherein the first diaphragm, the second diaphragm, and the third diaphragm are all peripherally clamped stress films;

The third through hole sequentially penetrates through the center positions of the first vibrating diaphragm, the first back electrode plate, the second vibrating diaphragm, the second back electrode plate and the third vibrating diaphragm, and is not communicated with the acoustic sealing cavity.

9. The MEMS structure of claim 1, wherein a side of the third diaphragm remote from the second diaphragm is provided with a substrate, and the third diaphragm is not provided with the first through hole.

10. A sensor for the use in a medical device, characterized by comprising the following steps: a MEMS structure as claimed in any one of claims 1 to 9.