CN214409044U

CN214409044U - Piezoelectric type MEMS acceleration sensor

Info

Publication number: CN214409044U
Application number: CN202120476987.XU
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: 2021-03-05
Filing date: 2021-03-05
Publication date: 2021-10-15
Anticipated expiration: 2031-03-05

Abstract

The application discloses piezoelectric type MEMS acceleration sensor includes: a substrate having a cavity; a vibration support layer formed over the substrate and covering the cavity; a first electrode layer formed over the vibration support layer; a first piezoelectric layer formed over the first electrode layer; a second electrode layer formed over the first piezoelectric layer; an opening located above the cavity and extending continuously from the upper surface of the second electrode layer to the lower surface of the first electrode layer; and the mass block is positioned in the opening area and is in direct contact with the vibration supporting layer. The resonance frequency of the MEMS acceleration sensor is easy to adjust.

Description

Piezoelectric type MEMS acceleration sensor

Technical Field

The present application relates to the field of MEMS (Micro-Electro-Mechanical Systems, abbreviated as Micro Electro Mechanical Systems), and in particular, to a piezoelectric MEMS acceleration sensor.

Background

The MEMS acceleration sensor mainly comprises a capacitance type acceleration sensor and a piezoelectric type acceleration sensor. The capacitive acceleration sensor mainly detects acceleration through capacitance change, and is a main technology used in the current market and equipment. The MEMS acceleration sensor is a sensor prepared by utilizing a micro-electro-mechanical system technology and a piezoelectric film technology, and has small size, small volume and good consistency because of adopting the technologies of a semiconductor plane process, bulk silicon processing and the like. Compared with a capacitor microphone, the piezoelectric acceleration sensor has the advantages of no need of bias voltage, large working temperature range, dust prevention, water prevention and the like, is suitable for being used as a wake-up device, has a larger dynamic measurement range due to no limitation of a capacitor gap, and has stronger impact resistance.

However, the conventional piezoelectric acceleration sensor has the problem that the resonant frequency is not easy to adjust, and an effective solution is not provided at present.

SUMMERY OF THE UTILITY MODEL

To solve the problems in the related art, the application provides a MEMS acceleration sensor capable of adjusting a resonant frequency.

The technical scheme of the application is realized as follows:

the application provides a MEMS acceleration sensor, includes:

a substrate having a cavity;

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

a first electrode layer formed over the vibration support layer;

a first piezoelectric layer formed over the first electrode layer;

a second electrode layer formed over the first piezoelectric layer;

an opening located above the cavity and extending continuously from an upper surface of the second electrode layer to a lower surface of the first electrode layer;

a mass located within the open area and in direct contact with the vibration support layer.

Wherein a projected area of the opening is located within the cavity.

Wherein a projection area of the proof mass is smaller than a projection area of the opening, and the proof mass is located at the center of the opening.

Wherein the mass is located above the vibrating support layer.

Wherein the mass is located below the vibration support layer.

Wherein the density of the mass block is greater than that of silicon nitride.

The MEMS acceleration sensor is provided with a plurality of through holes which are formed in the opening and penetrate through the vibration supporting layer, wherein the through holes are distributed in a circular shape.

The first electrode layer and the second electrode layer are provided with at least two mutually isolated partitions, the partitions of the first electrode layer and the second electrode layer which correspond to each other form electrode layer pairs, and the electrode layer pairs are sequentially connected in series.

The vibration supporting layer comprises a single-layer or multi-layer composite membrane structure formed by silicon nitride, silicon oxide, monocrystalline silicon and polycrystalline silicon.

The thickness of the vibration supporting layer is 0.8 micrometer, the thickness of the first electrode layer is 0.1 micrometer, the thickness of the piezoelectric layer is 0.7 micrometer, and the thickness of the second electrode layer is 0.1 micrometer.

By means of the technical scheme, the resonant frequency of the piezoelectric type MEMS acceleration sensor is easy to adjust.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used 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 it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 illustrates a schematic diagram of a piezoelectric MEMS acceleration sensor provided in accordance with some embodiments;

FIG. 2 shows a cross-sectional perspective view of the piezoelectric MEMS acceleration sensor of FIG. 1;

FIG. 3 illustrates a schematic diagram of a piezoelectric MEMS acceleration sensor provided in accordance with some embodiments;

FIG. 4 shows a cross-sectional perspective view of the piezoelectric MEMS acceleration sensor of FIG. 3;

figures 5 and 6 illustrate perspective and top views, respectively, of a piezoelectric MEMS acceleration sensor provided in accordance with some embodiments;

FIG. 7 shows a cross-sectional perspective view of the piezoelectric MEMS acceleration sensor of FIG. 5;

FIG. 8 shows a graph of the resonant frequency of the piezoelectric MEMS acceleration sensor of FIG. 1 as a function of the thickness of the mass;

fig. 9 shows a frequency response curve of the piezoelectric MEMS acceleration sensor of fig. 1.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments that can be derived from the embodiments given herein by a person of ordinary skill in the art are intended to be within the scope of the present disclosure.

The application provides a MEMS acceleration sensor, easily adjusts resonant frequency. The piezoelectric MEMS acceleration sensor will be described in detail below.

The substrate 10 has a cavity 11. The substrate 10 may have various shapes such as a circle or a square. The material of the substrate 10 comprises silicon or any suitable silicon-based compound or derivative (e.g., silicon wafer, SOI, polysilicon on SiO 2/Si).

The vibration support layer 20d is formed over the substrate 10 and covers the cavity 11. The vibration support layer 20d includes a single-layer or multi-layer composite film structure made of silicon nitride, silicon oxide, single crystal silicon, or polycrystalline silicon.

The first electrode layer 20c is formed over the vibration support layer 20 d.

The first piezoelectric layer 20b is formed over the first electrode layer 20 c. The first piezoelectric layer 20b includes one or more layers of zinc oxide, aluminum nitride, an organic piezoelectric film, lead zirconate titanate (PZT), a perovskite-type piezoelectric film, or other suitable materials.

The second electrode layer 20a is formed over the first piezoelectric layer 20 b. The first piezoelectric layer 20b can convert the applied pressure into a voltage, and the first electrode layer 20c and the second electrode layer 20a can transmit the generated voltage to other integrated circuit devices. The first electrode layer 20c and the second electrode layer 20a include aluminum, gold, platinum, molybdenum, titanium, chromium, and composite films composed thereof or other suitable materials. In some embodiments, the first electrode layer 20c and the second electrode layer 20a have at least two partitions isolated from each other, the partitions of the first electrode layer 20c and the second electrode layer 20a corresponding to each other form an electrode layer pair, and the electrode layer pairs are sequentially connected in series, so that the sensitivity of the piezoelectric MEMS acceleration sensor can be improved.

The opening 30 is located above the cavity 11 and extends continuously from the upper surface of the second electrode layer 20a to the lower surface of the first electrode layer 20 c. The projected area of the opening 30 is located within the cavity 11.

In the embodiment of the first piezoelectric layer 20b without the opening 30, the positive and negative charges generated by the first piezoelectric layer 20b are easily neutralized to cause a decrease in the output electrical signal. Therefore, the first piezoelectric layer 20b with the opening 30 provided by the present application avoids causing neutralization of positive and negative charges, thereby improving the sensitivity of the piezoelectric MEMS acceleration sensor.

In order to adjust the resonance frequency of the piezoelectric MEMS acceleration sensor, the present application also provides a mass 20e in the area of the opening 30, and the mass 20e is in direct contact with the vibrating support layer 20 d. The projected area of the mass 20e is smaller than the projected area of the opening 30, and preferably, the mass 20e is located at the center of the opening 30.

In the embodiment shown in fig. 1 and 2, the mass 20e is located above the vibrating support layer 20 d. In the embodiment shown in fig. 3 and 4, the mass 20e is located below the vibrating support layer 20 d. The mass 20e has a density greater than that of silicon nitride. Specifically, the mass 20e has a density greater than 3.2kg/dm 3. The material of the mass 20e may include tungsten, gold, silver, iron, and the like. In addition, the present application can control the resonant frequency range of the piezoelectric MEMS acceleration sensor by adjusting the thickness of the mass 20 e.

Referring to fig. 5, 6 and 7, in order to reduce residual stress and balance air pressure, the piezoelectric MEMS acceleration sensor may further include a plurality of through holes 40 formed in the opening 30 and penetrating through the vibration support layer 20d, wherein the through holes 40 are distributed in a circular shape. In addition, the provision of the through hole 40 may further increase the amplitude and output electrical signal of the piezoelectric MEMS acceleration sensor.

Fig. 8 shows the variation of the resonant frequency of the structure with the thickness of the mass 20e for specific dimensions and material parameters. Wherein the thickness of the vibration supporting layer 20d is 0.8 μm, the material is silicon nitride, and the radius is 500 μm. The first electrode layer 20c and the second electrode layer 20a had a thickness of 0.1 μm, inner and outer diameters of 350 μm and 500 μm, respectively, and were made of aluminum. The first piezoelectric layer 20b has a thickness of 0.7 μm, inner and outer diameters of 350 μm and 500 μm, respectively, and is made of zinc oxide. The mass 20e is located at the center of the vibrating support layer 20d, has a radius of 100 μm, and is made of iron. It can be seen from fig. 8 that as the thickness of the mass 20e increases, the resonant frequency gradually decreases and the controllable range is very large.

Fig. 9 shows the frequency response of the structure at the above specific dimensions and material parameters. At this time, the mass 20e has a thickness of 100 μm and a corresponding resonance frequency of about 3000 Hz. It can be seen from fig. 9 that the structure also has a bandwidth close to 2000Hz at this time.

To sum up, with the help of the above-mentioned technical scheme of this application, the resonant frequency of the piezoelectric type MEMS acceleration sensor that this application provided can be adjusted to about 3000Hz, is fit for doing the sound inductor. The piezoelectric MEMS acceleration sensor is arranged in an in-ear earphone, and can receive vibration transmitted from a vocal cord to ears through a skull when speaking, so as to sense sound. When applied in combination with a microphone, the piezoelectric MEMS accelerometer can filter the sound coming through the microphone or be used directly as a sound pickup in a noisy environment. Piezoelectric MEMS acceleration sensors are not sensitive to noise relative to the microphone and can therefore be used to filter the microphone signal or reduce background noise.

The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A MEMS acceleration sensor, characterized by comprising:

a substrate having a cavity;

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

a first electrode layer formed over the vibration support layer;

a first piezoelectric layer formed over the first electrode layer;

a second electrode layer formed over the first piezoelectric layer;

2. MEMS acceleration sensor according to claim 1, characterized in, that the projected area of the opening is located within the cavity.

3. MEMS acceleration sensor according to claim 2, characterized in, that the projected area of the mass is smaller than the projected area of the opening and that the mass is located in the center of the opening.

4. MEMS acceleration sensor according to claim 3, characterized in, that the mass is located above the vibrating support layer.

5. MEMS acceleration sensor according to claim 3, characterized in, that the mass is located below the vibrating support layer.

6. MEMS acceleration sensor according to claim 1, characterized in, that the density of the mass is larger than the density of silicon nitride.

7. The MEMS acceleration sensor of claim 1 further comprising through holes formed in the opening and extending through the vibration support layer, wherein the through holes are distributed in a circle.

8. The MEMS acceleration sensor of claim 1, characterized in that the first electrode layer and the second electrode layer have at least two mutually isolated sections, the mutually corresponding sections of the first electrode layer and the second electrode layer constituting electrode layer pairs, a plurality of the electrode layer pairs being connected in series in sequence.

9. The MEMS acceleration sensor of claim 1, characterized in that the vibrating support layer comprises a single or multilayer composite membrane structure of silicon nitride, silicon oxide, monocrystalline silicon, polycrystalline silicon.

10. The MEMS acceleration sensor of claim 1 characterized in that the thickness of the vibration support layer is 0.8 micron, the thickness of the first electrode layer is 0.1 micron, the thickness of the piezoelectric layer is 0.7 micron, the thickness of the second electrode layer is 0.1 micron.