CN219019031U

CN219019031U - MEMS structure

Info

Publication number: CN219019031U
Application number: CN202223111644.7U
Authority: CN
Inventors: 李冠华; 刘端
Original assignee: Anhui Aofei Acoustics Technology Co ltd
Current assignee: Anhui Aofei Acoustics Technology Co ltd
Priority date: 2022-11-16
Filing date: 2022-11-16
Publication date: 2023-05-12
Anticipated expiration: 2032-11-16

Abstract

The application discloses MEMS structure includes: a substrate having a cavity; a vibration supporting layer formed over the substrate and covering the cavity; a mass formed below the vibration supporting layer and suspended within the cavity; a lower electrode layer formed over the vibration supporting layer; a piezoelectric layer formed over the lower electrode layer; and an upper electrode layer formed over the piezoelectric layer, and divided into an outer ring electrode layer and an inner ring electrode layer by a dividing groove. In the MEMS structure provided by the application, the mass block is arranged below the vibration supporting layer, so that the amplitude of the MEMS structure is improved, and the sound pressure level of the MEMS structure is further improved.

Description

MEMS structure

Technical Field

The present application relates to the field of MEMS (Micro-Electro-Mechanical System, i.e. microelectromechanical systems) technology, and in particular to a MEMS structure.

Background

The piezoelectric MEMS speaker is a small electroacoustic device using a piezoelectric material as a sound conversion element, and the principle is to utilize the inverse piezoelectric effect, and to make the diaphragm vibrate by inputting a voltage signal to the diaphragm having the piezoelectric material, thereby driving the diaphragm and surrounding air to vibrate to radiate sound. Compared with the traditional moving-coil loudspeaker, the piezoelectric MEMS loudspeaker has the advantages of small volume, low power consumption, simple process, low cost and the like, and can be widely applied to various portable electronic devices.

Disclosure of Invention

Aiming at the problems in the related art, the application provides an MEMS structure which can improve the output sound pressure level.

The technical scheme of the application is realized as follows:

according to one aspect of the present application, there is provided a MEMS structure comprising:

a substrate having a cavity;

a vibration supporting layer formed over the substrate and covering the cavity;

a mass formed below the vibration supporting layer and suspended within the cavity;

a lower electrode layer formed over the vibration supporting layer;

a piezoelectric layer formed over the lower electrode layer;

and an upper electrode layer formed over the piezoelectric layer, and divided into an outer ring electrode layer and an inner ring electrode layer by a dividing groove.

The dividing grooves are formed in positive and negative stress dividing lines corresponding to the intrinsic modes of the MEMS structure.

Wherein the inner ring electrode layer and the outer ring electrode layer are driven by electric signals with a phase difference of 180 degrees, and the lower electrode layer is grounded.

The inner ring electrode layer is annular, and the outer ring electrode layer and the inner ring electrode layer are in a concentric circle structure.

Wherein the outer diameter of the outer ring electrode layer is aligned with the outer edge of the substrate.

Wherein the inner diameter of the inner ring electrode layer is aligned with the outer diameter edge of the mass.

Wherein the MEMS structure is applied to a MEMS speaker.

In the MEMS structure provided by the application, the mass block is arranged below the vibration supporting layer, so that bending rigidity of the middle part of the MEMS structure is increased, the middle part is made to do piston type movement, the amplitude of the MEMS structure is improved, and the sound pressure level of the MEMS structure is further improved.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 illustrates a perspective view of a MEMS structure provided in accordance with some embodiments;

FIG. 2 illustrates a top view of a MEMS structure provided in accordance with some embodiments;

FIG. 3 illustrates a cross-sectional view of a MEMS structure provided in accordance with some embodiments;

FIG. 4 illustrates a vibration mode diagram of a MEMS structure provided in accordance with some embodiments;

fig. 5 illustrates a sound pressure level frequency response curve of a MEMS structure provided in accordance with some embodiments.

Detailed Description

The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application are within the scope of the protection of the present application.

In accordance with embodiments of the present application, a MEMS structure is provided that may be used, but is not limited to, a sensor such as a microphone or microphone, or other actuator. The MEMS structure includes a substrate 10, a vibration supporting layer 20b, a mass 20a, a lower electrode layer 20c, a piezoelectric layer 20d, and an upper electrode layer. The MEMS structure will be described in detail below.

Referring to fig. 1, 2 and 3, the substrate 10 has a cavity 11. A vibration supporting layer 20b is formed over the substrate 10 and covers the cavity 11. The mass 20a is formed below the vibration supporting layer 20b and is suspended within the cavity 11. The lower electrode layer 20c is formed above the vibration supporting layer 20 b. The piezoelectric layer 20d is formed above the lower electrode layer 20 c.

The upper electrode layer is formed above the piezoelectric layer 20d, and the dividing groove 21 divides the upper electrode layer into an outer ring electrode layer 20e2 and an inner ring electrode layer 20e1. In some embodiments, the dividing grooves 21 are formed at positive and negative stress boundaries corresponding to the eigenmodes of the MEMS structure. In this way, the voltage with 180 DEG phase difference can be applied to the inner ring electrode layer 20e1 and the outer ring electrode layer 20e2 to excite the corresponding positive and negative stresses, so as to excite the eigenmodes to the maximum extent to obtain the maximum amplitude, and improve the output sound pressure level. In some embodiments, the lower electrode is grounded.

In some embodiments, the inner ring electrode layer 20e1 is annular, and the outer ring electrode layer 20e2 is concentric with the inner ring electrode layer 20e1. In some embodiments, the outer diameter of outer ring electrode layer 20e2 is aligned with the outer edge of substrate 10. In some embodiments, the inner diameter of the inner ring electrode layer 20e1 is aligned with the outer diameter edge of the mass 20a, so as to cover the area corresponding to the positive or negative stress in the eigenmodes, so as to excite the eigenmodes to the maximum extent, and not affect the piston motion of the diaphragm portion corresponding to the intermediate mass 20 a.

And the upper and lower electrode layers 20c may transmit a voltage into the MEMS structure, and the piezoelectric layer 20d may convert the applied voltage into a pressure. In other embodiments, the upper electrode layer may take other suitable shapes. Or the inner ring electrode layer 20e1 and the outer ring electrode layer 20e2 may have other suitable shapes.

In some embodiments, the substrate 10 comprises silicon or any suitable silicon-based compound or derivative (e.g., silicon wafer, SOI, polysilicon on SiO 2/Si). In some embodiments, the vibration supporting layer 20b includes a single-layer or multi-layer composite film structure of silicon nitride (Si 3N 4), silicon oxide, single crystal silicon, polysilicon, or other suitable supporting material. In some embodiments, the piezoelectric layer 20d includes zinc oxide, aluminum nitride, an organic piezoelectric film, lead zirconate titanate (PZT), a perovskite-type piezoelectric film, or other suitable material. The upper and lower electrode layers 20c comprise aluminum, gold, platinum, molybdenum, titanium, chromium, and combinations thereof, or other suitable materials.

Fig. 4 and 5 are vibration mode diagrams and sound pressure level frequency response curves at specific dimensions thereof. Wherein the voltage signal applied across the MEMS structure is 20Vpp. The phase difference of the electric signals of the inner ring electrode layer and the outer ring electrode layer is 180 degrees. The sound pressure level was calculated 3cm from the surface of the structure in the free field. The upper and lower electrode layers 20c in the MEMS structure are made of platinum, the piezoelectric layer 20d is made of lead zirconate titanate, and the vibration supporting layer 20b is made of silicon. Fig. 4 is a diagram of the vibration mode of the MEMS structure at a frequency of 1000Hz, and it can be seen that the MEMS structure exhibits a good piston motion, and the middle portion of the diaphragm of the MEMS structure has an amplitude of 40um or more. It can be seen from fig. 5 that the sound pressure level signals reach 62.5dB, 74.8dB, 93.1dB and 137dB at 1000Hz, 2000Hz, 5000Hz and 9500Hz, respectively, with very high output signals.

The output sound pressure level of the piezoelectric MEMS speaker of the prior art is generally low. In the MEMS structure provided by the present application, the electric signals with a phase difference of 180 degrees are applied to the inner ring electrode layer 20e1 and the outer ring electrode layer 20e2, so that the MEMS structure can generate larger amplitude. In addition, the mass block 20a is arranged below the vibration supporting layer 20b, so that bending rigidity of the middle part of the MEMS structure is increased, the middle part is made to perform piston type movement, the amplitude of the MEMS structure is improved, and the sound pressure level of the MEMS structure is further improved.

The foregoing description of the preferred embodiments of the present utility model is not intended to limit the utility model to the precise form disclosed, and any modifications, equivalents, and variations which fall within the spirit and principles of the present utility model are intended to be included within the scope of the present utility model.

Claims

1. A MEMS structure, comprising:

a substrate having a cavity;

a vibration supporting layer formed over the substrate and covering the cavity;

a lower electrode layer formed over the vibration supporting layer;

a piezoelectric layer formed over the lower electrode layer;

an upper electrode layer formed above the piezoelectric layer, and divided into an outer ring electrode layer and an inner ring electrode layer by a dividing groove;

2. The MEMS structure of claim 1 wherein the inner and outer ring electrode layers are driven with electrical signals 180 degrees out of phase, the lower electrode layer being grounded.

3. The MEMS structure of claim 2, wherein the inner ring electrode layer is annular and the outer ring electrode layer and the inner ring electrode layer are concentric.

4. A MEMS structure according to claim 3, wherein an outer diameter of the outer ring electrode layer is aligned with an outer edge of the substrate.

5. A MEMS structure according to claim 3, wherein an inner diameter of the inner ring electrode layer is aligned with an outer diameter edge of the proof mass.

6. The MEMS structure of claim 1, wherein the MEMS structure is applied to a MEMS speaker.