WO2021056606A1 - Mems chip and electronic device - Google Patents

Abstract

A MEMS chip and an electronic device, the MEMS chip comprising a substrate (11) having a back cavity (12), and a back electrode and two sensing films (14, 16) arranged on the substrate (11), the back electrode and the two sensing films (14, 16) being positioned on the back cavity (12), the two sensing films (14, 16) respectively forming a capacitor structure with the back electrode, the two sensing films (14, 16) respectively being positioned on the upper and lower sides of the back electrode, and at least one of the two sensing films (14, 16) comprising an active area (10a) opposite to the back cavity (12), an inactive area (10b) arranged on the outside of the active area (10a), and an isolation area positioned between the active area (10a) and the inactive area (10b), the isolation area comprising two insulating rings (18, 19) respectively connected to the active area (10a) and the inactive area (10b), and a buffer area (17) connected between the two insulating rings (18, 19), the two insulating rings (18, 19) being arranged around the effective area (10a); a sealed cavity (29) is formed between the two sensing films (14, 16), the cavity (29) being filled with gas with a viscosity coefficient less than air or the cavity (29) being filled with air having an air pressure less than standard atmospheric pressure.

Description

A MEMS chip and electronic equipment Technical field

The present invention relates to the field of microelectromechanical technology, and more specifically, to a MEMS chip and electronic equipment.

Background technique

In existing MEMS chips (for example, MEMS microphones), in order to reduce the parasitic capacitance in the low-vibration area around the diaphragm and improve the sensitivity of the MEMS chip, an insulating ring made of silicon nitride is usually added to the diaphragm. The insulating ring separates the diaphragm into an effective area located in the middle and an ineffective area located at the periphery of the effective area. The ineffective area of the diaphragm is connected to the back electrode through an internal circuit, thereby achieving an equipotential between the ineffective area and the back electrode and eliminating the parasitic capacitance between the two.

However, this approach causes a potential difference to be formed between the effective area and the ineffective area. When foreign matter in the external environment falls on the insulating ring, and the size of the foreign matter is greater than the width of the insulating ring, the effective area and the ineffective area will be connected together, which will cause leakage and cause poor product quality of the MEMS chip.

Therefore, it is necessary to provide a new technical solution to solve at least one of the above-mentioned technical problems.

Summary of the invention

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

According to the first aspect of the present invention, a MEMS chip is provided. The chip includes a substrate with a back cavity, a back electrode provided on the substrate, and two sensing films, the back electrode and the two sensing films are located on the back cavity, and the two sensing films Are respectively located on the upper and lower sides of the back electrode, and respectively form a capacitor structure with the back electrode, at least one of the two sensing films includes an effective area opposite to the back cavity, and is arranged outside the effective area The ineffective area and the isolation area located between the effective area and the ineffective area, the isolation area includes two insulating rings connected to the effective area and the ineffective area respectively, and connected to the two The buffer zone between the insulating rings, the two insulating rings are arranged around the effective area; a sealed cavity is formed between the two sensing films, and the gas with a viscosity coefficient less than air is filled in the cavity, Or, the cavity is filled with air whose air pressure is lower than the standard atmospheric pressure.

Optionally, the material of the insulating ring is silicon nitride or silicon oxynitride.

Optionally, the material of the buffer zone is the same as the material of the effective area.

Optionally, the invalid region and the back electrode are connected.

Optionally, the ineffective area is connected to the substrate.

Optionally, the back electrode includes a conduction layer and a reinforcement layer located on at least one surface of the conduction, and the conduction layer and the reinforcement layer are compounded together.

Optionally, the gas with a viscosity coefficient less than air is isobutane, propane, propylene, H ₂ , ethane, ammonia, acetylene, ethyl chloride, ethylene, CH ₃ Cl, methane, SO ₂ , H ₂ S , At least one of chlorine, CO ₂ , N ₂ O, and N2.

Optionally, two through holes are provided on the two sensing films, at least one through hole is provided on the back electrode, and the positions of the two through holes and the through holes correspond to each other, and the through holes are also provided with through holes. The two through-holes and the sealed film layer of the through-hole, both ends of the film layer are respectively sealedly connected with the inner surfaces of the two sensing films.

Optionally, a plurality of pads are buried on the substrate, and the plurality of pads are respectively connected to the back electrode, the substrate, and the sensing film through conductors located in the substrate.

Optionally, the isolation region includes two adjacent end portions, the two end portions extend in a radial direction, and the effective area extends outward to form a conductive portion, and the conductive portion is located at two Between the end portions, the two end portions and the conductive portion pass through the ineffective area together.

According to another aspect of the present disclosure, an electronic device is provided. The electronic device includes the aforementioned MEMS chip.

According to an embodiment of the present disclosure, in the embodiment of the present disclosure, the isolation region includes at least two insulating rings and a buffer zone located between the two insulating rings. In this way, the size of the isolation region in the radial direction can be significantly increased. In this way, the buffer area can more effectively prevent larger-sized external impurities from falling on the isolation region, which will cause the effective region and the ineffective region to form conduction. This buffer greatly improves the stability of the MEMS chip.

In addition, in the embodiments of the present disclosure, the durability and reliability of the MEMS chip are better.

In addition, the MEMS chip has high sensitivity.

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

Description of the drawings

The drawings incorporated in the specification and constituting a part of the specification illustrate the embodiments of the present invention, and together with the description are used to explain the principle of the present invention.

FIG. 1 is a cross-sectional view of a MEMS chip according to an embodiment of the present disclosure.

Fig. 2 is a top view of a MEMS chip according to an embodiment of the present disclosure.

Fig. 3 is a cross-sectional view of another MEMS chip according to an embodiment of the present disclosure.

Description of reference signs:

10a: effective area; 10b: ineffective area; 11: substrate; 12: back cavity; 13: conduction part; 14: second sensing film; 15: conduction layer; 16: first sensing film; 17: buffer zone 18: the first insulating ring; 19: the second insulating ring; 20: the first pad; 21: the second pad; 22: the third pad; 23: the fourth pad; 24a: the first conductor; 24b : Second conductor; 24c: third conductor; 24d: fourth conductor; 24e: fifth conductor; 25: first reinforcement layer; 26: second reinforcement layer; 27: through hole; 28: film layer; 29: cavity Body; 31: through hole.

detailed description

Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying 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 only illustrative, and in no way serves as any limitation to the present invention and its application or use.

The technologies, methods, and equipment known to those of ordinary skill in the relevant fields may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be regarded as part of the specification.

In all examples shown and discussed herein, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiment may have different values.

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

According to an embodiment of the present disclosure, a MEMS chip is provided. The MEMS chip may be a MEMS microphone chip or an environmental sensor chip. For example, the environmental sensor chip is a pressure sensor chip, a temperature sensor chip, a humidity sensor chip, and so on.

FIG. 1 is a cross-sectional view of a MEMS chip according to an embodiment of the present disclosure. Fig. 2 is a top view of a MEMS chip according to an embodiment of the present disclosure.

As shown in Figs. 1-2, the MEMS chip includes a substrate 11 having a back cavity 12, a back electrode disposed on the substrate 11, and two sensing films. For example, the substrate 11 is a semiconductor material. The substrate 11 is formed by vapor deposition. The back cavity 12 is formed on the substrate 11 by etching.

The back electrode and the sensing film are located on the back cavity 12. As shown in Figure 1, the two sensing films are located on the upper and lower sides of the back electrode, respectively. The two sensing films respectively form a capacitor structure with the back electrode.

As shown in FIG. 1, the two sensing films are the first sensing film 16 and the second sensing film 14 respectively. The first sensing film 16 is located above the back electrode, and the second sensing film 14 is located below the back electrode. The two sensing membranes are spaced from the back electrode to form a vibration space.

At least one of the sensing films includes an effective area 10a opposite to the back cavity 12, an ineffective area 10b arranged outside the effective area 10a, and an isolation area located between the effective area 10a and the ineffective area 10b. The effective area 10a and the back electrode respectively serve as two electrodes of the capacitor structure.

A through hole 27 is provided on the sensing film. The through holes 27 are used to balance the air pressure on both sides of the sensing film.

The isolation region separates the ineffective region 10b and the effective region 10a, so that the ineffective region 10b and the effective region 10a are insulated from each other. The ineffective region 10b and the back electrode are connected by a conductor (for example, the following fourth conductor 24d). The ineffective region 10b and the back electrode are conductive, that is to say, the two are equipotential, thereby eliminating the parasitic capacitance between the two.

The isolation region includes two insulating rings respectively connected to the effective region 10a and the ineffective region 10b, and a buffer zone 17 connected between the two insulating rings 18 and 19. The two insulating rings 18, 19 are arranged around the effective area 10a.

For example, the first insulating ring 18 is connected to the effective area 10a. The second insulating ring 19 is connected to the invalid region 10b. The buffer zone 17 is connected between the first insulating ring 18 and the second insulating ring 19.

For example, the material of the insulating ring (for example, the first insulating ring 18, the second insulating ring 19) is silicon nitride or silicon oxynitride. The insulation effect of the above-mentioned materials is good. The insulating rings (for example, the first insulating ring 18 and the second insulating ring 19) are circular rings. The ring makes the entire effective area 10a circular. The vibration of the circular effective region 10a is more balanced than other shapes. Of course, the insulating ring can also be an elliptical ring, a racetrack ring, etc.

For example, the two insulating rings 18, 19 are both circular rings, and the two insulating rings 18, 19 are arranged concentrically. The concentric arrangement makes the connection strength between the effective area 10a and the ineffective area 10b higher. The structure of the sensing membrane is more balanced. The vibration of the sensing film can be more balanced.

In other examples, the two insulating rings 18, 19 can also be arranged in an eccentric manner.

In the embodiment of the present disclosure, the isolation region includes at least two insulating rings 18 and 19 and a buffer zone 17 located between the two insulating rings 18 and 19. In this way, the size of the isolation region in the radial direction can be significantly increased. In this way, the buffer area 17 can more effectively prevent larger-sized external impurities from falling on the isolation region, which may cause the effective region 10a and the ineffective region 10b to become conductive. The buffer 17 greatly improves the stability of the MEMES chip.

In addition, if the width of the insulating ring is increased to increase the size of the isolation region in the radial direction, the greater the toughness of the insulating ring itself, the wider size will result in low strength of the insulating ring, which will make the MEMS chip The overall structure has poor strength and durability.

In the embodiment of the present disclosure, at least two insulating rings 18 and 19 are arranged, and a buffer zone 17 is arranged between the two insulating rings 18 and 19. This makes it possible to form the buffer zone 17 by using a material with high toughness and high durability without increasing the width of the insulating ring, thereby achieving an increase in the width of the isolation region in the radial direction. In this way, the durability and reliability of the MEMS chip are better.

For example, the material of the buffer zone 17 is polysilicon, graphene, etc. The above materials all have good toughness and structural strength. Those skilled in the art can set the width of the buffer zone 17 according to actual needs. The width is the dimension along the radial direction.

For example, the material of the buffer zone 17 and the effective area 10a are the same. For example, polysilicon or graphene materials are used. Because the material is the same, the preparation of the sensing film becomes easy.

In an example, the back electrode, the ineffective region 10b, and the substrate 11 are electrically connected. For example, the three are connected through a conductor provided in the substrate 11.

It is also possible that the back electrode, the substrate 11 and the ineffective region 10b of the sensing film are conducted through a conductor located outside the substrate 11. For example, the three are connected to external circuits. The external circuit is equipotential, so that the three are conductive.

In this way, the parasitic capacitance between the three can be effectively eliminated.

In an example, the back electrode includes a conductive layer and a reinforcing layer located on at least one surface of the conductive layer. The conducting layer and the reinforcing layer are compounded together.

For example, as shown in FIG. 1, the conductive layer plays a role of conducting electricity, and its material is polysilicon, graphene, and the like. The conduction layer is connected to the external circuit. The conduction layer is used to accommodate charges. The reinforcing layer has the characteristics of high structural strength, and its material is silicon nitride, silicon oxynitride, etc. A first reinforcement layer 25 is provided on the upper surface of the conductive layer, and a second reinforcement layer 26 is provided on the lower surface. In this way, the structural strength of the back electrode becomes greater, and the durability of the MEMS chip is good.

Of course, it is also possible to compound the reinforcing layer on only one surface of the conducting layer.

For example, both sensing films include an effective area 10a and an ineffective area 10b. The effective areas 10a of the two sensing films are both circular and are arranged oppositely. The two sensing films have the same area. Through holes 27 are provided on the two sensing films.

The two sensing films 14, 16 vibrate in the same direction during operation. In this way, the capacitances formed between the two sensing films 14, 16 and the back electrodes are opposite to each other. After being processed by the ASIC chip, the two capacitance signals can effectively eliminate the noise signal after being superimposed, thereby achieving a noise reduction effect. The two sensing films 14, 16 make the noise of the MEMS chip smaller and the sensing accuracy higher.

Here, the noise signal is not limited to the sound signal, and may also be an undesirable signal that appears when measuring a pressure signal, a temperature signal, a humidity signal, and the like.

Fig. 3 is a cross-sectional view of another MEMS chip according to an embodiment of the present disclosure.

As shown in FIG. 3, the two sensing films 14, 16 each include an effective area 10a, an ineffective area 10b, and an isolation area. A through hole 27 is provided in the middle of the two sensing films 14 and 16. A plurality of through holes are provided on the back electrode. At least one through hole is opposed to the two through holes 27.

The MEMS chip also includes a cylindrical membrane layer 28 penetrating the two sensing membranes and the back electrode along the vibration direction. The two ends of the cylindrical film layer 28 are respectively opposed to the two through holes 27 and communicate with each other, so that a sealed cavity 29 is formed between the two sensing films. For example, the two ends of the film layer 28 are sealed to the inner surfaces of the two sensing films 14, 16 respectively. The channel enclosed by the film 28 can balance the air pressure inside and outside the back electrode.

In addition, the sensitivity of the MEMS can be adjusted by adjusting the inner diameter of the channel enclosed by the membrane layer 28. For example, when the MEMS chip is a microphone chip, the low-frequency sensitivity of the microphone chip can be improved by adjusting the inner diameter of the channel. For example, the low-frequency cutoff frequency can reach below 1KHz.

The cavity 29 is filled with a gas having a viscosity coefficient smaller than air. Since a through hole is provided on the back electrode, the gas flows in the cavity instead of being isolated by the back electrode. In this way, the gas can effectively reduce the resistance of the gas when the sensing membranes 14, 16 vibrate, especially when the gas passes through the through holes. In this way, the noise of the MEMS chip can be effectively reduced, and the sensitivity of the MEMS chip can be effectively improved.

For example, the gas with a viscosity coefficient less than air is isobutane, propane, propylene, H ₂ , ethane, ammonia, acetylene, ethyl chloride, ethylene, CH ₃ Cl, methane, SO ₂ , H ₂ S, chlorine , _{At least one of CO 2} , N ₂ O, and N2.

In other examples, the cavity 29 is sealed with air. The air pressure in the cavity 29 is lower than the standard atmospheric pressure, so as to achieve the set vacuum degree. For example, the cavity can be vacuum sealed by encapsulating under a set vacuum degree. Since the air pressure in the cavity is reduced, the viscosity coefficient of the gas in the cavity can be effectively reduced. Similarly, in this way, the noise of the MEMS chip can be effectively reduced, and the sensitivity of the MEMS chip can be effectively improved.

A plurality of pads are buried on the substrate 11. The effective area 10a of the first sensing film 16 is connected to the first pad 20 through the fifth conductor 24e. The back electrode is connected to the second pad 21 through the first conductor 24a. The effective area 10a of the second sensing film 14 is connected to the third pad 22 through the second conductor 24b. The substrate 11 is connected to the fourth pad 23 through the third conductor 24c. The ineffective region 10b of the first sensing film 16 and the ineffective region 10b of the second sensing film 14 are connected to the back electrode through the fourth conductor 24d to eliminate the parasitic capacitance between the three.

Among them, the fourth pad 23 and the second pad 21 are respectively connected to two external pads of the ASIC chip, and the two external pads are conductive, so that the back electrode and the substrate 11 are conductive. The formation of equipotential, which can avoid the generation of parasitic capacitance.

In an example, as shown in FIG. 2, the isolation region includes two ends arranged adjacently. The two ends are spaced apart. The two ends extend in the radial direction. The effective area 10 a extends outward to form a conductive portion 13. The conduction portion 13 is used for conduction between the effective area 10a and the external circuit. The conducting portion 13 is located between the two end portions. The two ends and the conducting portion 13 pass through the ineffective area 10b together.

In this example, the arrangement of the two ends extending outward and the conductive portion 13 facilitates the connection between the effective area 10a and the external circuit.

In addition, through the isolation of the two end portions, the conductive portion 13 can be insulated from the ineffective region 10b.

According to another embodiment of the present disclosure, an electronic device is provided. For example, electronic devices are mobile phones, smart watches, walkie-talkies, computers, smart boxes, VR devices, AR devices, headsets, smart speakers, smart screens, environmental monitoring devices, etc. The electronic device includes the aforementioned MEMS chip.

The electronic equipment has the characteristics of stable quality and good durability.

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 illustration and not for limiting 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 (11)

1. A MEMS chip, characterized in that it comprises a substrate with a back cavity, a back electrode provided on the substrate and two sensing films, the back electrode and the two sensing films are located on the back cavity , The two sensing films are respectively located on the upper and lower sides of the back electrode, and respectively form a capacitor structure with the back electrode, at least one of the two sensing films includes an effective area opposite to the back cavity, An ineffective area arranged outside the effective area and an isolation area located between the effective area and the ineffective area, the isolation area including two insulating rings respectively connected to the effective area and the ineffective area, And a buffer zone connected between the two insulating rings, the two insulating rings are arranged around the effective area; a sealed cavity is formed between the two sensing films, and the cavity is filled with adhesive A gas with a hysteresis coefficient less than air, or air with a pressure lower than the standard atmospheric pressure is filled in the cavity.
2. The MEMS chip of claim 1, wherein the material of the insulating ring is silicon nitride or silicon oxynitride.
3. The MEMS chip of claim 1, wherein the material of the buffer zone is the same as the material of the effective area.
4. The MEMS chip of claim 1, wherein the ineffective area and the back electrode are connected.
5. 4. The MEMS chip according to claim 4, wherein the ineffective area is connected to the substrate.
6. The MEMS chip according to claim 1, wherein the back electrode comprises a conductive layer and a reinforcing layer located on at least one surface of the conductive layer, and the conductive layer and the reinforcing layer are compounded together.
7. The MEMS chip according to claim 1, wherein the gas with a viscosity coefficient less than air is isobutane, propane, propylene, H ₂ , ethane, ammonia, acetylene, ethyl chloride, ethylene, CH ₃ At least one of Cl, methane, SO ₂ , H ₂ S, chlorine, CO ₂ , N ₂ O, and N2.
8. The MEMS chip according to any one of claims 1-7, characterized in that: two through holes are provided on the two sensing films, at least one through hole is provided on the back electrode, and two through holes are provided on the back electrode. The positions of the through holes and the through holes correspond to each other, and further include a sealed film layer penetrating through the two through holes and the through hole, and two ends of the film layer are respectively connected with the two sensing films. The inner surface is hermetically connected.
9. The MEMS chip according to claim 8, wherein a plurality of pads are buried on the substrate, and the plurality of pads are connected to the back electrode and the back electrode through a conductor located in the substrate. The substrate and the sensing film are connected.
10. The MEMS chip according to any one of claims 1-7, wherein the isolation region includes two end portions arranged adjacently, the two end portions extend in a radial direction, and the effective area is Extending outward to form a conducting part, the conducting part is located between the two end parts, and the two end parts and the conducting part pass through the ineffective area together.
11. An electronic device, characterized by comprising the MEMS chip according to any one of claims 1-10.

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