CN111137843A

CN111137843A - MEMS diaphragm and MEMS sensor chip

Info

Publication number: CN111137843A
Application number: CN201911411547.XA
Authority: CN
Inventors: 何宪龙
Original assignee: Gettop Acoustic Co Ltd
Current assignee: Gettop Acoustic Co Ltd
Priority date: 2019-12-31
Filing date: 2019-12-31
Publication date: 2020-05-12
Anticipated expiration: 2039-12-31
Also published as: CN111137843B

Abstract

The invention provides an MEMS diaphragm and an MEMS sensor chip, wherein the MEMS diaphragm comprises a sensing part and a peripheral part surrounding the periphery of the sensing part, a plurality of outer grooves and two inner grooves are arranged between the peripheral part and the sensing part, the outer grooves are annularly arranged on the inner edge of the peripheral part, the two inner grooves are annularly arranged on the outer edge of the sensing part, and the two inner grooves are asymmetrical relative to the center of the sensing part. When the MEMS diaphragm is subjected to pressure higher than a preset pressure, the sensing part can move in a seesaw mode, namely a valve mode relative to the peripheral part, stress is released in time, external mechanical force such as larger pressure can be released, and the diaphragm is not resisted by the external mechanical force, so that the mechanical reliability and the sensitivity of the MEMS diaphragm and the MEMS sensor chip are improved.

Description

MEMS diaphragm and MEMS sensor chip

Technical Field

The invention relates to the technical field of Micro-Electro-mechanical systems (MEMS), in particular to an MEMS membrane and an MEMS sensor chip.

Background

The mems sensor is widely applied to various acoustic receivers or force sensors, and has characteristics of small size, low power consumption, high sensitivity, etc., which are the design targets, and it can be known from the theoretical simulation result that the influence of residual stress has a great influence on the mechanical sensitivity of the vibration film in the acoustic sensor.

The mems device includes a capacitive sensor structure, which is generally a sensing film coupled with a back electrode to form two parallel plate capacitor structures for sensing vibration or pressure change. The material properties of the sensing film determine the device sensitivity performance, but the thermal residual stress generated during the semiconductor processing process cannot be avoided. The existing process technology still cannot precisely control the film stress, and thus the sensitivity of the micro-electromechanical device is low or the sensitivity varies.

Therefore, how to provide a sensing film with good stress releasing effect and high mechanical sensitivity is a problem that needs to be solved in the industry.

Disclosure of Invention

In view of this, the present invention provides an MEMS membrane with good stress release effect and high mechanical reliability.

The invention also provides an MEMS sensor chip applying the MEMS membrane.

The invention provides an MEMS (micro-electromechanical system) membrane, which comprises a sensing part and a peripheral part surrounding the periphery of the sensing part, wherein a plurality of outer grooves and two inner grooves are arranged between the peripheral part and the sensing part, the outer grooves are annularly arranged at the inner edge of the peripheral part, the two inner grooves are annularly arranged at the outer edge of the sensing part, and the two inner grooves are asymmetrical relative to the center of the sensing part.

Preferably, an included angle between a connecting line of two ends of one of the inner grooves and the center of the sensing part is larger than an included angle between a connecting line of two ends of the other of the inner grooves and the center of the sensing part.

Preferably, the sensing portion is circular, the two inner grooves extend along a circumferential direction of the sensing portion, the outer grooves extend along another circumferential direction, the another circumferential direction is concentric with the circumferential direction of the sensing portion, and the center of the circle coincides with the center of the sensing portion.

Preferably, the end of the outer groove is provided with a first bending portion, and the first bending portion extends towards the outer side of the MEMS membrane, or the first bending portion extends towards the inner side of the MEMS membrane.

In some embodiments, the first bend is U-shaped.

In some embodiments, the first bend comprises a curved segment, a straight segment, or a combination of the curved segment and the straight segment.

Preferably, the end of the inner groove extends towards the inner side or the outer side of the MEMS membrane to form a second bent portion, the second bent portion is U-shaped, and the second bent portion includes an arc-shaped section, a straight-line section, or a combination of the arc-shaped section and the straight-line section.

Preferably, the end of the first bending part is an arc-shaped end; and/or the tail end of the second bending part is a circular arc-shaped tail end.

Preferably, a first connecting arm is formed between two adjacent outer slots, a second connecting arm is formed between two adjacent inner slots, an annular connecting arm is formed between the outer slots and the two inner slots, the annular connecting arm is connected to the peripheral portion through the first connecting arm, the annular connecting arm is connected to the sensing portion through the second connecting arm, and the first connecting arm and the second connecting arm are mutually staggered in the circumferential direction of the annular connecting arm.

Preferably, the number of outer slots is greater than the number of inner slots.

Preferably, the sensing portion moves in a seesaw manner with respect to the peripheral portion when the MEMS diaphragm is subjected to a pressure greater than a predetermined pressure.

Preferably, the circumferential width of the first connecting arm decreases and then increases first along the radial direction of the MEMS diaphragm; and/or the circumferential width of the second connecting arm is firstly reduced and then increased along the radial direction of the MEMS diaphragm.

Preferably, each of the first connecting arms has the same circumferential width, and each of the second connecting arms has the same circumferential width.

In some embodiments, the annular connecting arms have a uniform radial width.

In some embodiments, the width of the annular connecting arms is greater at the ends proximal to the inner and/or outer slots than at the ends distal thereto.

In some embodiments, the radial width of the portion of the annular connecting arm adjacent to the second connecting arm is greater than the radial width of the other portions of the annular connecting arm.

The invention further provides an MEMS sensor chip which comprises the MEMS diaphragm.

In summary, the present invention provides an MEMS membrane, in which a plurality of outer slots and two inner slots are disposed between a sensing portion and an outer peripheral portion, an annular connecting arm is formed between the outer slots and the inner slots, a first connecting arm is formed between two adjacent outer slots, and a second connecting arm is formed between two adjacent inner slots. The outer grooves are annularly arranged on the inner edge of the peripheral portion, the two inner grooves are annularly arranged on the outer edge of the sensing portion, and the two inner grooves are asymmetric with respect to the center of the sensing portion. When the MEMS diaphragm is subjected to pressure higher than a preset pressure, the sensing part can move in a seesaw mode, namely a valve mode relative to the peripheral part, stress is released in time, external mechanical force such as larger pressure can be released, and the diaphragm is not resisted by the external mechanical force, so that the mechanical reliability and the sensitivity of the MEMS diaphragm and the MEMS sensor chip are improved. When the MEMS membrane is under the action of less than a preset pressure intensity, such as sound pressure, the average displacement of the sensing part is large, so that the sensitivity of the MEMS membrane can be improved.

The first connecting arm and the second connecting arm are arranged in a staggered mode in the circumferential direction, the arc design of the tail end of the first bending part and the tail end of the second bending part can reduce stress concentration, the first bending part and the second bending part which extend in a bending mode enable the mechanical sensitivity of the sensing part to be improved, and the reliability of the diaphragm is improved.

In some embodiments, the annular connecting arm and the second connecting arm drive the sensing portion to move, and the annular connecting arm and the second connecting arm are located far away from the clamped point and are not affected by the position of the clamped point due to semiconductor process variation, so that the motion of the sensing portion is insensitive to the position variation of the clamped point, and the sensing stability and reliability of the MEMS membrane can be improved.

Drawings

Fig. 1 is a schematic structural diagram of a MEMS membrane of the present invention.

FIG. 2 is a schematic structural view of the MEMS diaphragm of the present invention moving in a seesaw manner.

Detailed Description

Before the embodiments are described in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in other forms of implementation. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," "having," and the like, herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. In particular, when "a certain element" is described, the present invention is not limited to the number of the element being one, and may include a plurality of the elements.

Fig. 1 is a schematic structural diagram of a MEMS diaphragm according to an embodiment of the present invention. The MEMS membrane 10 is used in a micro-electromechanical device, for example, in a micro-electromechanical sensor, a micro-electromechanical condenser microphone. The MEMS membrane 10 includes a sensing portion 12 and a peripheral portion 14, wherein the sensing portion 12 is located on an inner side of the MEMS membrane 10, and the peripheral portion 14 is located on an outer side of the MEMS membrane 10 and surrounds the sensing portion 12. The sensing portion 12 is used for sensing an external pressure, for example, sensing a sound pressure, and when the micro-electromechanical condenser microphone is applied, the sensing portion 12 moves relative to the backplate under the action of the sound pressure, so that a capacitance between the sensing portion and the backplate changes to generate a corresponding electrical signal. The peripheral portion 14 is used to connect and support the sensing portion 12.

The region between the sensing portion 12 and the peripheral portion 14 is provided with a plurality of outer grooves 16 and two inner grooves 18, the plurality of outer grooves 16 are annular and are arranged at the inner edge of the peripheral portion 14 at intervals, the plurality of outer grooves 16 jointly define an outer circle, the two inner grooves 18 are annular and are arranged at the outer edge of the sensing portion 12 at intervals, and the two inner grooves 18 jointly define an inner circle. In this embodiment, the outer circle and the inner circle are concentric, and the center of the circle coincides with the center of the sensing portion 12. The outer slots 16 and the two inner slots 18 form an annular connecting arm 20 therebetween, and the peripheral portion 14 is connected to the sensing portion 12 through the annular connecting arm 20. The outer groove 16, the inner groove 18 and the annular connecting arm 20 separate the peripheral portion 14 from the sensing portion 12, and prevent the force generated by elastic deformation from being transmitted to the sensing region when the peripheral portion 14 is deformed, so as to improve the stability of the sensing portion 12 and the stability of the linear output of the MEMS diaphragm 10. The widths of the outer groove 16, the inner groove 18 and the annular connecting arm 20 may be determined according to actual design requirements for distributing stress and reducing stress concentration on the MEMS membrane 10.

In some embodiments, the annular connecting arm 20 has a uniform radial width, i.e., the outer slots 16 each extend in an outer circumferential direction and the two inner slots 18 each extend in an inner circumferential direction.

In other embodiments, the annular connecting arms 20 may also have varying radial widths, for example, increasing their radial width in areas of greater stress to increase their rigidity, for example, the annular connecting arms 20 may have a greater width near the ends of the inner and/or

outer slots

18, 16 than at the ends remote therefrom.

The end of the outer grooves 16 is provided with a first bending part, which may be arranged to extend towards the outside of the membrane or towards the inside of the membrane. The ends of both inner grooves 18 extend towards the inner side of the diaphragm, and the two inner grooves 18 are asymmetric about the center of the sensing part 12. The arrangement is such that when the MEMS diaphragm 10 is subjected to less than a predetermined pressure, the sensing portion 12 remains substantially planar and moves in a direction perpendicular to the MEMS diaphragm 10 in a piston-like motion, i.e., straight up and down, relative to the peripheral portion 14; when the MEMS membrane 10 is subjected to more than another predetermined pressure, in particular a larger pressure, the sensing portion 12 is able to move in a see-saw fashion with respect to the peripheral portion 14 and to release the pressure.

In this embodiment, the sensing portion 12, the annular connecting arm 20 and the peripheral portion 14 can be integrally formed. The MEMS membrane 10 may be made of carbon-based polymer, silicon nitride, polysilicon, silicon dioxide, silicon carbide, arsenide, carbon, and metals such as germanium, gallium, titanium, gold, iron, copper, chromium, tungsten, aluminum, platinum, nickel, tantalum, or alloys thereof. The MEMS membrane 10 may be square, circular, or other shapes, and in this embodiment, a circle is illustrated. That is, the peripheral portion 14 is also circular.

It should be noted that the outer side and the inner side are relative to the central portion of the entire MEMS membrane 10, the outer side is a direction away from the central portion, and the inner side is a direction toward the central portion. In this embodiment, the outer slots 16 together define an outer circle, the two inner slots 18 together define an inner circle, the outer circle and the inner circle are concentric, and the peripheral portion 14 and the sensing portion 12 are both circular, so that the center of the circle is also the center of the peripheral portion 14 and the sensing portion 12, or the center of the circle of the MEMS membrane 10, and the centers of the circles are the same. The center of the MEMS membrane 10 can also be understood as the center of the circle.

The two inner grooves 18 are asymmetric with respect to the center of the sensing part 12, that is, the two inner grooves 18 are asymmetric with respect to the center of the sensing part 12.

More specifically, an included angle formed between a line connecting both ends of one of the two inner grooves 18a and the center of the sensing part 12 is larger than an included angle formed between a line connecting both ends of the other one of the two inner grooves 18b and the center of the sensing part 12. In other words, the circumferential length of the inner groove 18a is greater than the circumferential length of the inner groove 18 b. The design is such that when the MEMS diaphragm 10 is subjected to a pressure higher than the other predetermined pressure, i.e. a larger impact, the sensing part 12 moves in a seesaw manner with respect to the peripheral part 14, as shown in fig. 2, i.e. the portion of the sensing part 12 enclosed by the inner groove 18a is tilted in a pressure direction (upward in the figure) with respect to the peripheral part 14 and the portion of the sensing part 12 enclosed by the inner groove 18b is tilted in a direction opposite to the pressure direction (downward in the figure) with respect to the peripheral part 14, and opens in a valve manner, thereby forming a leakage path to release the larger impact.

The number of the outer grooves 16 may be plural, preferably four or more, and further preferably eight according to specific design requirements and practical use conditions. In the embodiment shown in fig. 1-2, the number of outer slots 16 is set to eight.

The eight outer slots 16 are evenly spaced circumferentially, and each outer slot 16 is uniform in shape and configuration. The outer slots 16 may or may not be equal in length. In some embodiments, the number of outer slots 16 is greater than the number of inner slots 18. The shape and structure of only one outer groove 16 will be described below.

The end of the outer slot 16 is provided with a first bending part 22, and the first bending part 22 can extend towards the outside or towards the inside. The first bend 22 may comprise a curved segment, a straight segment, or a combination of curved and straight segments. That is, the end of the outer groove 16 may extend outward or inward in a curved shape, may extend outward or inward in a linear shape, or may extend outward or inward in a curved shape first and then in a linear shape or first and then in a curved shape.

In the illustrated embodiment, each outer slot 16 is provided at both ends with a first bend 22. In order to reduce stress concentration, the end of the first bent portion 22 may have a circular arc shape.

The end of the inner groove 18 is provided with a second bent portion 24, and the second bent portion 24 extends toward the inner side. The second bend 24 may also comprise a curved segment, a straight segment, or a combination of curved and straight segments. That is, the end of the inner tank 18 may extend inward in a curved shape, may extend inward in a straight shape, may extend inward in a curved shape first and then in a straight shape, or may extend inward in a straight shape first and then in a curved shape.

In the illustrated embodiment, the ends of each inner groove 18 are provided with second bends 24. In order to reduce stress concentration, the end of the second bent portion 24 may have a circular arc shape.

It should be understood that, in the present invention, the first bent portions 22 of all the outer slots 16 extend toward the outer side at the same time, or extend toward the inner side at the same time. The second bends 24 of all of the inner slots 18 extend simultaneously toward the inner side. In some embodiments, it is also possible that the first bent portion 22 of the partial outer groove 16 extends toward the outside, and the first bent portion 22 of the partial outer groove 16 extends toward the inside.

In the embodiment shown in fig. 1-2, the first bend 22 at the end of the outer channel 16 is U-shaped. More specifically, the first bent portion 22 at the end of the outer slot 16 extends toward the outside, and the first bent portion 22 is an arc-shaped segment, and the arc-shaped segment extends toward the outside in a half-round bracket shape. For an outer slot 16, the first bends 22 at the ends of the outer slot 16 can be considered as forming a complete bracket. For two adjacent outer slots 16, the two adjacent first bends 22 of the two adjacent outer slots 16 can be regarded as two opposite semicircular brackets. The second bend 24 at the end of the inner groove 18 is U-shaped. Specifically, the second bent portion 24 at the end of the inner groove 18 extends toward the inner side, and the second bent portion 24 is also an arc-shaped segment extending toward the inner side in a half-bracket shape. For an inner groove 18, the two second bent portions 24 at the two ends of the inner groove 18 can be regarded as forming a complete round bracket. For adjacent

inner grooves

18a and 18b, the two second bent portions 24 of the inner groove 18a adjacent to the inner groove 18b can be regarded as two semicircular brackets with opposite directions.

First connecting arms 26 are formed between adjacent outer slots 16, and second connecting arms 28 are formed between the ends of adjacent

inner slots

18a and 18b, wherein in the illustrated embodiment, each first connecting arm 26 has the same structure and shape, and each second connecting arm 28 has the same structure and shape. The first connecting arm 26 extends outwardly from the outer edge of the annular connecting arm 20, the second connecting arm 28 extends inwardly from the inner edge of the annular connecting arm 20, and the first connecting arm 26 and the second connecting arm 28 are offset from each other in the circumferential direction of the annular connecting arm 20. In the present embodiment, the two second connecting arms 28 correspond to positions in which the centers of the two circumferentially opposite outer grooves 16 are offset toward the same side, respectively.

Since the first bent portion 22 is an arc-shaped segment extending outward in a half-bracket shape, and the second bent portion 24 is an arc-shaped segment extending inward in a half-bracket shape, the circumferential width of the first connecting arm 26 is first reduced and then increased outward in the radial direction of the MEMS diaphragm 10; the circumferential width of the second connecting arms 28 first decreases and then increases radially inward of the MEMS diaphragm 10.

The circumferential width of the first connecting arm 26 may be set to be greater than, equal to or less than the circumferential width of the second connecting arm 28 according to the specific design requirements and practical use of the MEMS membrane 10. In the present embodiment, the circumferential widths of the first connecting arm 26 and the second connecting arm 28 are set to be the same.

Thus, the peripheral portion 14 is integrally connected to the sensing portion 12 by the first connecting arm 26, the annular connecting arm 20 and the second connecting arm 28.

When the MEMS membrane 10 is subjected to a pressure lower than the predetermined pressure, for example, receives a normal sound pressure, the sensing portion 12 can be kept substantially flat and move relative to the peripheral portion 14 in a direction perpendicular to the membrane toward the force receiving direction, at this time, the second connecting arm 28 moves vertically along with the sensing portion 12, the annular connecting arm 20 is connected between the first connecting arm 26 and the second connecting arm 28 in a warped manner, the average displacement of the sensing portion is large, and the sensitivity of the sensing portion can be improved.

In the use process, the MEMS membrane is fixed to an application scene such as an MEMS microphone through the fixed point, and in the MEMS membrane of the above embodiment, the annular connecting arm 20 and the second connecting arm 28 drive the sensing portion 12 to move, and the annular connecting arm 20 and the second connecting arm 28 are located far away from the fixed point, and are not affected by the position of the fixed point due to semiconductor process variation, so that the movement of the sensing portion 12 is insensitive to the position variation of the fixed point, thereby improving the sensing stability and reliability of the MEMS membrane.

In summary, in the MEMS membrane provided in the embodiments of the present invention, the plurality of outer slots and the two inner slots are disposed between the sensing portion and the outer peripheral portion, the ends of the outer slots extend outward, and the ends of the inner slots extend inward. An annular connecting arm is formed between the outer grooves and the inner grooves, a first connecting arm is formed between every two adjacent outer grooves, and a second connecting arm is formed between every two adjacent inner grooves. The plurality of outer grooves are annularly arranged on the inner edge of the peripheral part, the two inner grooves are annularly arranged on the outer edge of the sensing part, the two inner grooves are asymmetrically arranged on the center of the sensing part, the rigidity, the mechanical strength and the mechanical reliability of the diaphragm are improved, the sensing part moves relative to the peripheral part along the direction vertical to the diaphragm when the MEMS diaphragm is subjected to pressure intensity smaller than a preset pressure intensity, the average displacement of the sensing part is large, and the sensitivity of the sensing part can be improved.

When the MEMS diaphragm is subjected to pressure higher than another preset pressure, the sensing part moves in a seesaw mode relative to the peripheral part, stress is released in time, external mechanical force such as larger pressure can be released, and the diaphragm is not resisted by the external mechanical force, so that the mechanical reliability and the sensitivity of the MEMS diaphragm and the MEMS sensor chip are improved. The first connecting arm and the second connecting arm are arranged in a staggered mode in the circumferential direction, the arc design of the tail end of the first bending part and the tail end of the second bending part can reduce stress concentration, the first bending part and the second bending part which extend in a bending mode enable the mechanical sensitivity of the sensing part to be improved, and the reliability of the diaphragm is improved.

The concepts described herein may be embodied in other forms without departing from the spirit or characteristics thereof. The particular embodiments disclosed should be considered illustrative rather than limiting. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. Any changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

1. The MEMS diaphragm comprises a sensing part and a peripheral part surrounding the periphery of the sensing part, and is characterized in that a plurality of outer grooves and two inner grooves are arranged between the peripheral part and the sensing part, the outer grooves are annularly arranged on the inner edge of the peripheral part, the two inner grooves are annularly arranged on the outer edge of the sensing part, and the two inner grooves are asymmetrical with respect to the center of the sensing part.

2. The MEMS diaphragm of claim 1, wherein an angle between a line connecting both ends of one of said inner grooves and a center of said sensing portion is larger than an angle between a line connecting both ends of the other of said inner grooves and a center of said sensing portion.

3. The MEMS diaphragm according to claim 2, wherein the sensing portion has a circular shape, the two inner grooves extend in a circumferential direction of the sensing portion, respectively, the plurality of outer grooves extend in another circumferential direction, respectively, the another circumferential direction being concentric with the circumferential direction of the sensing portion, the center of the circle coinciding with a center of the sensing portion.

4. The MEMS diaphragm according to claim 1, wherein the end of the outer groove has a first bent portion, the first bent portion has a U-shape, and the first bent portion extends toward the inner side or the outer side of the MEMS diaphragm.

5. The MEMS diaphragm of claim 1, wherein the end of the inner groove extends toward the inner or outer side of the MEMS diaphragm to form a second bent portion, the second bent portion comprising an arc-shaped segment, a straight segment, or a combination thereof.

6. The MEMS diaphragm according to claim 4 or 5,

the tail end of the first bending part is an arc-shaped tail end; and/or

The tail end of the second bending part is an arc-shaped tail end.

7. The MEMS membrane of any one of claims 1 to 5, wherein a first connecting arm is formed between two adjacent outer grooves, a second connecting arm is formed between two adjacent inner grooves, and a ring-shaped connecting arm is formed between the plurality of outer grooves and the two inner grooves, the ring-shaped connecting arm being connected to the peripheral portion by the first connecting arm and connected to the sensing portion by the second connecting arm, the first connecting arm and the second connecting arm being offset from each other in a circumferential direction of the ring-shaped connecting arm.

8. The MEMS diaphragm of claim 7,

the circumferential width of the first connecting arm is firstly reduced and then increased along the radial direction of the MEMS diaphragm; and/or

The circumferential width of the second connecting arm is firstly reduced and then increased along the radial direction of the MEMS diaphragm.

9. The MEMS diaphragm of claim 7,

the annular connecting arms have a uniform radial width; or

The width of the annular connecting arms is greater at the ends close to the inner and/or outer slots than at the ends remote therefrom.

10. The MEMS diaphragm of claim 1 wherein the number of outer grooves is greater than the number of inner grooves, the sensing portion moving in a see-saw fashion relative to the peripheral portion when the MEMS diaphragm is subjected to greater than a predetermined pressure.

11. A MEMS sensor chip, characterized in that it comprises a MEMS membrane according to any of claims 1 to 10.