CN216253241U

CN216253241U - MEMS structure

Info

Publication number: CN216253241U
Application number: CN202122623872.1U
Authority: CN
Inventors: 夏永禄; 刘端
Original assignee: Anhui Aofei Acoustics Technology Co ltd
Current assignee: Anhui Aofei Acoustics Technology Co ltd
Priority date: 2021-10-29
Filing date: 2021-10-29
Publication date: 2022-04-08
Anticipated expiration: 2031-10-29

Abstract

The application discloses MEMS structure includes: a substrate having a first cavity; a first piezoelectric composite vibration layer formed over the substrate and suspended over the first cavity; a second piezoelectric composite vibration layer formed over the first piezoelectric composite vibration layer and suspended over a second cavity; a spacer layer formed between the first piezoelectric composite vibration layer and the second piezoelectric composite vibration layer, and the second cavity separates the first piezoelectric composite vibration layer and the second piezoelectric composite vibration layer. In summary, the MEMS structure includes a first piezoelectric composite vibration layer and a second piezoelectric composite vibration layer separated by a spacer layer and a second cavity, so that a larger output voltage can be obtained, and the sensitivity of the MEMS structure is improved.

Description

MEMS structure

Technical Field

The present application relates to the field of Electro-acoustic conversion devices, and in particular, to a Micro-Electro-mechanical system (MEMS) structure.

Background

The MEMS piezoelectric microphone is prepared by utilizing a micro-electro-mechanical system technology and a piezoelectric film technology, and has small size, small volume and good consistency due to the adoption of semiconductor planar technology, bulk silicon processing technology and other technologies. Meanwhile, compared with a condenser microphone, the microphone also has the advantages of no need of bias voltage, large working temperature range, dust prevention, water prevention and the like. At present, the MEMS piezoelectric microphone is mainly of a cantilever beam structure and a composite piezoelectric vibration membrane structure, but the sensitivity is low, and the development of the MEMS piezoelectric microphone is still restricted.

SUMMERY OF THE UTILITY MODEL

To solve the problems in the related art, the present application provides a MEMS structure capable of obtaining a MEMS structure with high sensitivity.

The technical scheme of the application is realized as follows:

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

a substrate having a first cavity;

a first piezoelectric composite vibration layer formed over the substrate and suspended over the first cavity;

a second piezoelectric composite vibration layer formed over the first piezoelectric composite vibration layer and suspended over a second cavity;

a spacer layer formed between the first piezoelectric composite vibration layer and the second piezoelectric composite vibration layer, and the second cavity separates the first piezoelectric composite vibration layer and the second piezoelectric composite vibration layer.

Wherein the MEMS structure includes a barrier layer formed between the substrate and the first piezo-electric composite vibration layer.

The first piezoelectric composite vibration layer comprises a first vibration support layer, a first electrode layer, a first piezoelectric layer and a second electrode layer which are sequentially stacked, wherein the first vibration support layer is formed above the barrier layer and suspended above the first cavity.

Wherein the spacer layer is formed over the first vibration support layer and the spacer layer is spaced apart from the first electrode layer, the first piezoelectric layer, and the second electrode layer.

Wherein the second piezoelectric composite vibration layer includes a second vibration support layer, a third electrode layer, a second piezoelectric layer, and a fourth electrode layer, which are sequentially stacked, wherein the second vibration support layer is formed above the spacer layer and suspended above the second cavity.

Wherein the first piezoelectric layer and the second piezoelectric layer are equal in size length.

Wherein the projection area of the first piezoelectric layer and the second piezoelectric layer in the vertical direction is smaller than the projection area of the first cavity and the second cavity in the vertical direction.

The first piezoelectric composite vibration layer is provided with a first through hole, and the first through hole is communicated with the first cavity and the second cavity; and the second piezoelectric composite vibration layer is provided with a second through hole which is communicated with the second cavity.

In summary, the MEMS structure includes a first piezoelectric composite vibration layer and a second piezoelectric composite vibration layer separated by a spacer layer and a second cavity, so that a larger output voltage can be obtained, and the sensitivity of the MEMS structure is improved.

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 perspective cross-sectional view of a MEMS structure provided in accordance with some embodiments;

fig. 2-12 illustrate schematic diagrams of methods of fabricating MEMS structures provided in accordance with some embodiments.

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.

According to an embodiment of the present application, there is provided a MEMS structure capable of improving sensitivity and improving output energy. The MEMS structure can be applied to sensors, such as microphones, and also to actuators, such as speakers. Referring to fig. 1, the MEMS structure, which will be described in detail below, includes a substrate 10, a first piezo-electric composite vibration layer 20, a second piezo-electric composite vibration layer 30, and a spacer layer 40.

Referring collectively to fig. 1 to 12, a substrate 10 has a first cavity 11. The substrate 10 comprises silicon or any suitable silicon-based compound or derivative (e.g., silicon wafer, SOI, polysilicon on SiO 2/Si).

A barrier layer 12 is formed over the substrate 10. The material of the barrier layer 12 comprises silicon dioxide. The first cavity 11 penetrates the substrate 10 and the barrier layer 12 in the vertical direction.

The first piezoelectric composite vibration layer 20 is formed over the barrier layer 12 and suspended over the first cavity 11. The first piezoelectric composite vibration layer 20 includes a first vibration support layer 21, a first electrode layer 22, a first piezoelectric layer 23, and a second electrode layer 24, which are stacked in this order. Wherein a first vibration support layer 21 is formed above the barrier layer 12 and suspended above the first cavity 11. The first piezoelectric layer 23 can convert the applied pressure into a voltage, and the first electrode layer 22 and the second electrode layer 24 can transmit the generated voltage to other integrated circuit devices. In some embodiments, the first vibrating support layer 21 comprises a single or multi-layer composite membrane structure of silicon nitride (Si3N4), silicon oxide, single crystal silicon, polycrystalline silicon, or other suitable support material. In some embodiments, the first piezoelectric layer 23 comprises zinc oxide, aluminum nitride, an organic piezoelectric film, lead zirconate titanate (PZT), a perovskite-type piezoelectric film, or other suitable material. The first electrode layer 22 and the second electrode layer 24 include aluminum, gold, platinum, molybdenum, titanium, chromium, and composite films thereof or other suitable materials.

A spacer layer 40 is formed over the first vibration support layer 21, and the spacer layer 40 is separated from the first electrode layer 22, the first piezoelectric layer 23, and the second electrode layer 24. The material of the spacer layer 40 includes silicon oxide, PSG (phospho-silicate glass).

The second piezoelectric composite vibration layer 30 is formed over the first piezoelectric composite vibration layer 20 and suspended over the second cavity 50. The second piezoelectric composite vibration layer 30 includes a second vibration support layer 31, a third electrode layer 32, a second piezoelectric layer 33, and a fourth electrode layer 34, which are laminated in this order. Wherein the second vibration support layer 31 is formed over the spacer layer 40 and suspended over the second cavity 50.

The spacer layer 40 is formed between the first piezo-electric composite vibration layer 20 and the second piezo-electric composite vibration layer 30, and the second cavity 50 separates the first piezo-electric composite vibration layer 20 and the second piezo-electric composite vibration layer 30.

In some embodiments, the materials and functions of the respective layers of the first piezoelectric composite vibration layer 20 and the second piezoelectric composite vibration layer 30 are the same. The first electrode layer 22, the first piezoelectric layer 23, and the second electrode layer 24 in the first piezoelectric composite vibration layer 20 realize conversion between acoustic energy and electric energy based on a piezoelectric effect or an inverse piezoelectric effect, and thus the first electrode layer 22, the first piezoelectric layer 23, and the second electrode layer 24 function as a first functional layer for energy conversion. Similarly, the third electrode layer 32, the second piezoelectric layer 33 and the fourth electrode layer 34 are also second functional layers for energy conversion. In some embodiments, the projection area of the first functional layer in the vertical direction is smaller than the projection area of the first cavity 11 and the second cavity 50 in the vertical direction. The projection area of the second functional layer in the vertical direction is smaller than the projection areas of the first cavity 11 and the second cavity 50 in the vertical direction. The first piezoelectric layer 23 and the second piezoelectric layer 33 are equal in size length. Further, the projection area of the first piezoelectric layer 23 and the second piezoelectric layer 33 in the vertical direction is smaller than the projection area of the first cavity 11 and the second cavity 50 in the vertical direction. Because the first functional layer and the second functional layer are suspended, the residual stress of the first piezoelectric composite vibration layer 20 and the second piezoelectric composite vibration layer 30 is released, the warpage of the first piezoelectric composite vibration layer 20 and the second piezoelectric composite vibration layer 30 is reduced, and the sensitivity is improved.

The first piezoelectric composite vibration layer 20 has a first through hole 25, and the first through hole 25 communicates the first cavity 11 and the second cavity 50. The second piezoelectric composite vibration layer 30 has a second through hole 35, and the second through hole 35 communicates with the second cavity 50. The first through holes 25 and the second through holes 35 are respectively distributed at equal intervals, which helps to further release the residual stress and achieve the balance of the upper and lower air pressures of the first piezoelectric composite vibration layer 20 and the second piezoelectric composite vibration layer 30.

From the above, the MEMS structure includes the first piezoelectric composite vibration layer 20 and the second piezoelectric composite vibration layer 30 separated by the spacer layer 40 and the second cavity 50, so that a larger output voltage can be obtained, and the sensitivity of the MEMS structure is improved.

In addition, the application also provides a method for manufacturing the MEMS structure, which comprises the following specific steps:

referring to fig. 2 and 3, step 1, silicon, which is a material of the substrate 10, is provided, and a barrier layer 12 is obtained on the front side of the substrate 10 after a thermal oxidation treatment.

Referring to fig. 4, step 2, a first vibration support layer 21 is formed and patterned. The forming method comprises chemical vapor deposition.

Referring to fig. 5, step 3, a first electrode layer 22 is formed and patterned. The forming method comprises physical vapor deposition.

Referring to fig. 6, step 4, a first piezoelectric layer 23 is formed and patterned. Methods of formation include sputtering, Metal Organic Chemical Vapor Deposition (MOCVD), and chemical solution deposition techniques.

Referring to fig. 7, step 5, a second electrode layer 24 is formed and patterned. The forming method comprises physical vapor deposition.

Referring to fig. 8, step 6, a spacer layer 40 is formed and planarized by CMP (chemical mechanical polishing). The forming method comprises chemical vapor deposition.

Referring to fig. 9 and 10, step 7, in conformity with steps 2 to 5, forms the second piezoelectric composite vibration layer 30.

Referring to fig. 11, step 8, a back side deep silicon etch forms the first cavity 11 and removes a portion of the barrier layer 12.

Referring to fig. 12, step 9, portions of the spacer layer 40 are wet removed to form the second cavity 50, the first via 25 and the second via 35.

The present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A MEMS structure, comprising:

a substrate having a first cavity;

2. The MEMS structure of claim 1, comprising a barrier layer formed between the substrate and the first piezoelectric composite vibration layer.

3. The MEMS structure of claim 2, wherein the first piezoelectric composite vibration layer comprises a first vibration support layer, a first electrode layer, a first piezoelectric layer, and a second electrode layer, which are sequentially stacked, wherein the first vibration support layer is formed over the barrier layer and suspended over the first cavity.

4. The MEMS structure of claim 3, wherein the spacer layer is formed over the first vibrating support layer and the spacer layer is spaced apart from the first electrode layer, the first piezoelectric layer, and the second electrode layer.

5. The MEMS structure of claim 4, wherein the second piezoelectric composite vibration layer comprises a second vibration support layer, a third electrode layer, a second piezoelectric layer, and a fourth electrode layer, which are sequentially stacked, wherein the second vibration support layer is formed over the spacer layer and suspended over the second cavity.

6. The MEMS structure of claim 5, wherein the first piezoelectric layer and the second piezoelectric layer are equal in size length.

7. The MEMS structure of claim 6, wherein a projected area of the first piezoelectric layer and the second piezoelectric layer in a vertical direction is smaller than a projected area of the first cavity and the second cavity in a vertical direction.

8. The MEMS structure of claim 1, wherein the first piezo-electric composite vibration layer has a first via hole thereon, the first via hole communicating the first cavity and the second cavity; and the second piezoelectric composite vibration layer is provided with a second through hole which is communicated with the second cavity.