CN111417060B

CN111417060B - Manufacturing method of MEMS structure

Info

Publication number: CN111417060B
Application number: CN202010316634.3A
Authority: CN
Inventors: 刘端
Original assignee: Anhui Aofei Acoustics Technology Co ltd
Current assignee: Anhui Aofei Acoustics Technology Co ltd
Priority date: 2020-04-21
Filing date: 2020-04-21
Publication date: 2021-04-06
Anticipated expiration: 2040-04-21
Also published as: CN111417060A

Abstract

The application discloses a manufacturing method of an MEMS structure, which comprises the following steps: forming a piezoelectric composite vibration layer above the front surface of the substrate; etching the back surface of the substrate until the piezoelectric composite vibration layer is reached, so that the substrate comprises an outer ring body and a support plate arranged in the outer ring body and connected with the outer ring body, wherein a cavity is formed between the support plate and the outer ring body; the piezoelectric composite vibration layer is cut through etching, so that the piezoelectric composite vibration layer comprises a fixed end connected with the supporting plate and a free end suspended above the cavity. The manufacturing method of the MEMS structure reduces the process difficulty and improves the performance of the MEMS structure.

Description

Manufacturing method of MEMS structure

Technical Field

The present application relates to the field of semiconductor technology, and more particularly, to a method for manufacturing a MEMS (micro electro Mechanical Systems, abbreviated as micro electro Mechanical Systems) structure.

Background

MEMS microphones (microphones) mainly include both capacitive type and piezoelectric type. 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 capacitor microphone, the MEMS piezoelectric microphone also has the advantages of no bias voltage, large working temperature range, dust prevention, water prevention and the like, but the sensitivity is low, so that the development of the MEMS piezoelectric microphone is restricted. Moreover, the diaphragm of the MEMS piezoelectric microphone is easily warped when the size is large.

In order to solve the problems of low sensitivity and easiness in warping of a diaphragm of a piezoelectric MEMS structure in the related art, no effective solution is provided at present.

Disclosure of Invention

In order to solve the problems in the related art, the application provides a manufacturing method of an MEMS structure, which can improve the sensitivity and reduce the probability of membrane warping.

The technical scheme of the application is realized as follows:

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

forming a piezoelectric composite vibration layer above the front surface of the substrate;

etching the back surface of the substrate until the piezoelectric composite vibration layer is reached, so that the substrate comprises an outer ring body and a support plate arranged in the outer ring body and connected with the outer ring body, wherein a cavity is formed between the support plate and the outer ring body;

the piezoelectric composite vibration layer is cut through etching, so that the piezoelectric composite vibration layer comprises a fixed end connected with the supporting plate and a free end suspended above the cavity.

Wherein after the cavity is formed and before the piezoelectric composite vibration layer is divided by etching, a sacrificial support layer is conformally formed on the back surface of the substrate, and the sacrificial support layer is removed after the piezoelectric composite vibration layer is divided.

Wherein, in the step of etching the back surface of the substrate until reaching the piezoelectric composite vibration layer, the support plate is caused to extend from the outer ring body toward the center of the outer ring body;

in the step of etching and dividing the piezoelectric composite vibration layer, the piezoelectric composite vibration layer is made to include one or more diaphragms, fixed ends of each of the diaphragms are connected to the support plate, and free ends of each of the diaphragms are suspended above the cavity.

Wherein in the step of etching and dividing the piezoelectric composite vibration layer, fixed ends of adjacent diaphragms are made different.

Wherein in the step of etching and dividing the piezoelectric composite vibration layer, the fixed ends of at least two adjacent diaphragms are made to be the same.

Wherein, in the step of etching and dividing the piezoelectric composite vibration layer, the projection profile of the free end of each diaphragm in the vibration direction is located inside the corresponding cavity.

In the step of etching and dividing the piezoelectric composite vibration layer, the projection profile of the free end of each diaphragm in the vibration direction is the same as the projection profile of the corresponding cavity in the vibration direction.

Wherein the width of the piezoelectric composite vibration layer is gradually reduced from the fixed end to the free end.

Wherein a width of the piezoelectric composite vibration layer is kept constant from the fixed end to the free end.

Wherein the method of forming the piezoelectric composite vibration layer includes:

depositing a support material on the substrate to form a vibrating support layer;

depositing a first electrode material on the vibrating support layer, patterning the first electrode material to form a first electrode layer;

depositing a piezoelectric material over the first electrode layer and patterning the piezoelectric material to form a first piezoelectric layer;

depositing a second electrode material over the first piezoelectric layer, and patterning the second electrode material to form a second electrode layer.

Therefore, compare and do not contain the technical scheme of backup pad in MEMS structure, this application has shortened the cantilever beam from the stiff end to the length of free end through setting up one or more backup pads to the probability of the diaphragm warpage of piezoelectricity composite vibration layer has been reduced. Moreover, the probability of warping of the diaphragm of the piezoelectric composite vibration layer is reduced, so that the process difficulty of the MEMS structure is reduced, and the yield and the stability of the device are improved. In addition, a fixed end and a free end are freely designed in the MEMS structure, so that the sensitivity of a plurality of cantilever beam structures in the piezoelectric composite vibration layer is effectively improved. In a word, the manufacturing method of the MEMS structure provided by the application reduces the process difficulty and improves the performance of the MEMS structure.

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 MEMS structure provided in accordance with some embodiments;

FIG. 2 is an exploded view of the MEMS structure shown in FIG. 1;

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

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

fig. 5 to 9 are sectional views along a direction parallel to the support plate at intermediate stages of fabricating the MEMS structure shown in fig. 3.

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.

Referring to fig. 1, in accordance with an embodiment of the present application, a MEMS structure is provided that may be used in, but is not limited to, a sensor such as a microphone or microphone, or other actuator. In some embodiments, the MEMS structure includes a substrate 10 and a piezoelectric composite vibration layer 20.

Referring to fig. 2, the substrate 10 includes an outer ring body 11 and a support plate 12 disposed inside the outer ring body 11 and connected to the outer ring body 11, wherein the support plate 12 and the outer ring body 11 have a cavity 13 therebetween.

A piezoelectric composite vibration layer 20 is formed over the substrate 10, the piezoelectric composite vibration layer 20 including a fixed end connected to the support plate 12 and a free end suspended over the cavity 13.

In this MEMS structure, since the substrate 10 includes the outer ring body 11 and the support plate 12, and the piezoelectric composite vibration layer 20 is fixedly connected to the support plate 12 to constitute a cantilever. Thus, the present application provides new MEMS structures and simplifies the process steps. The MEMS structure and the method of fabricating the same will be described in detail below.

Referring to fig. 5, step S101, a piezoelectric composite vibration layer 20 is formed over the front surface of the substrate 10. The material of the substrate 10 includes silicon or any suitable silicon-based compound or derivative (e.g., silicon wafer, SOI, SiO 2). The method of forming the piezoelectric composite vibration layer 20 includes:

depositing a support material on the substrate 10 forms a vibrating support layer 21. The vibration support layer 21 includes 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 consideration of the problem of controlling the stress of the vibration support layer 21, the vibration support layer 21 may be provided in a multi-layer structure to reduce the stress. The method of forming the vibration support layer 21 includes a thermal oxidation method or a chemical vapor deposition method. In some embodiments, the step of forming the vibration support layer 21 may be skipped or omitted.

A first electrode material is deposited on the vibration support layer 21, and patterned to form a first electrode layer 22.

A piezoelectric material is deposited over the first electrode layer 22 and patterned to form a first piezoelectric layer 23. In some embodiments, the material of the first piezoelectric layer 23 includes one or more layers of zinc oxide, aluminum nitride, an organic piezoelectric film, lead zirconate titanate, a perovskite-type piezoelectric film, or other suitable materials. Methods of forming the first piezoelectric layer 23 include magnetron sputtering, deposition, or other suitable methods.

A second electrode material is deposited over the first piezoelectric layer 23 and patterned to form a second electrode layer 24. The material of the first electrode layer 22 and the second electrode layer 24 includes aluminum, gold, platinum, molybdenum, titanium, chromium, and composite films composed of these or other suitable materials. Methods of forming the first electrode layer 22 and the second electrode layer 24 include physical vapor deposition or other suitable methods.

In this embodiment, the first electrode layer 22, the first piezoelectric layer 23, and the second electrode layer 24 constitute a piezoelectric composite layer. 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. The first electrode layer 22 and the second electrode layer 24 have at least two partitions isolated from each other, the partitions of the first electrode layer 22 and the second electrode layer 24 corresponding to each other constitute electrode layer pairs, and the plurality of electrode layer pairs are connected in series in sequence.

In some embodiments, a second piezoelectric layer (not shown) is formed over the second electrode layer 24, and a third electrode layer (not shown) is formed over the second piezoelectric layer. The material of the second piezoelectric layer includes one or more layers of zinc oxide, aluminum nitride, an organic piezoelectric film, lead zirconate titanate, a perovskite-type piezoelectric film, or other suitable materials. The material and formation method of the second piezoelectric layer may be the same as or different from those of the first piezoelectric layer 23. The material of the third electrode layer includes aluminum, gold, platinum, molybdenum, titanium, chromium, and a composite film composed of these materials or other suitable materials. The material and the formation method of the third electrode layer may be the same as or different from those of the first electrode layer 22. In addition, in this embodiment, the piezoelectric composite layer of the MEMS structure has the first electrode layer 22, the first piezoelectric layer 23, the second electrode layer 24, the second piezoelectric layer, and the third electrode layer, so that a bimorph structure is formed, and the piezoelectric conversion efficiency of the MEMS structure is improved. In addition, in an embodiment where the vibration support layer 21 is not provided, a second piezoelectric layer and a third electrode layer may be formed in order above the second electrode layer 24. In the embodiment where the vibration support layer 21 is provided, there is no second piezoelectric layer and no third electrode layer above the second electrode layer 24. It is noted that in the embodiment shown in fig. 5 of the present application, the piezoelectric composite vibration layer 20 includes a vibration support layer 21, a first electrode layer 22, a first piezoelectric layer 23, and a second electrode layer 24.

Referring to fig. 6, step S102, the back surface of the substrate 10 is etched until the piezoelectric composite vibration layer 20 is reached, so that the substrate 10 includes the outer ring body 11 and the support plate 12 disposed inside the outer ring body 11 and connected to the outer ring body 11. Wherein a cavity 13 is formed between the support plate 12 and the outer ring body 11. The cavity 13 may be formed by DRIE (abbreviation of Deep Reactive Ion Etching) or wet Etching. In some embodiments, the support plate 12 extends from the outer ring body 11 toward the center of the outer ring body 11. In other embodiments, the support plate 12 may have a curved shape in a top-down view, or the support plate 12 may not pass through the center of the outer ring body 11. The number of the support plates 12 may be one or more.

Referring to fig. 7, in step S103, a sacrificial support layer 30 is conformally formed on the back surface of the substrate 10. In a subsequent step, the sacrificial support layer 30 is used to support the piezoelectric composite vibration layer 20. The material of the sacrificial support layer 30 includes aluminum material, LTO (Low Temperature Oxide), or other corrosion prone material. Methods of forming the sacrificial support layer 30 include chemical vapor deposition, physical vapor deposition, or other suitable methods.

Referring to fig. 8, in step S104, the piezoelectric composite vibration layer 20 is etched and divided such that the piezoelectric composite vibration layer 20 includes a fixed end connected to the support plate 12 and a free end suspended above the cavity 13. The piezoelectric composite vibration layer 20 includes one or more diaphragms 20a, a fixed end of each diaphragm 20a being connected to the support plate 12, and a free end of each diaphragm 20a being suspended above the cavity 13. The free end of each diaphragm 20a has a projection profile in the vibration direction inside the corresponding cavity 13. The projected contour of the free end of each diaphragm 20a in the vibration direction is similar in shape to the projected contour of the corresponding cavity 13 in the vibration direction.

Referring to fig. 1, 3 and 4, in some embodiments, each diaphragm 20a has a direction extending from the corresponding fixed end to the free end, and the fixed ends of adjacent diaphragms 20a are different.

In some embodiments, each diaphragm 20a has a direction extending from the corresponding fixed end to the free end, and the fixed ends of at least two adjacent diaphragms 20a are the same. These embodiments are not shown in the figures.

In the embodiment shown in fig. 1 and 3, the width of the piezoelectric composite vibration layer 20 is gradually reduced from the fixed end to the free end.

In the embodiment shown in fig. 4, the width of the piezoelectric composite vibration layer 20 is kept constant from the fixed end to the free end.

Referring to fig. 9, in step S105, the sacrificial support layer 30 is removed after the piezoelectric composite vibration layer 20 is divided. After removal of the sacrificial support layer 30, the free end of each membrane 20a is unconstrained, thereby achieving a cantilever beam structure for each membrane 20 a.

In the MEMS structure formed based on the above manufacturing method, one or more support plates 12 are provided within the outer ring body 11 of the substrate 10, and the one or more support plates 12 are used as fixed ends of cantilevers of the diaphragms 20a of the piezoelectric composite vibration layer 20. Therefore, compared with the technical scheme that the MEMS structure does not contain the support plate 12, the length of the cantilever beam from the fixed end to the free end is shortened by arranging one or more support plates 12, and the probability of warping of the diaphragm 20a of the piezoelectric composite vibration layer 20 is reduced. Moreover, the probability of warping of the diaphragm 20a of the piezoelectric composite vibration layer 20 is reduced, so that the process difficulty of the MEMS structure is reduced, and the yield and the stability of the device are improved. In addition, the fixed end and the free end are freely designed in the MEMS structure in the present application, so that the sensitivity of the multiple cantilever structures in the piezoelectric composite vibration layer 20 is effectively improved.

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 method of fabricating a MEMS structure, comprising:

the etching is cut apart piezoelectricity composite vibration layer makes piezoelectricity composite vibration layer include with stiff end that the backup pad is connected with suspend in the free end of cavity top, piezoelectricity composite vibration layer's width is followed the stiff end to the free end reduces gradually or keeps invariable.

2. The method of fabricating a MEMS structure according to claim 1, wherein after the cavity is formed and before the piezoelectric composite vibration layer is divided by etching, a sacrificial support layer is conformally formed on a back surface of the substrate, and the sacrificial support layer is removed after the piezoelectric composite vibration layer is divided.

3. The method of manufacturing a MEMS structure of claim 1,

in the step of etching the back surface of the substrate until reaching the piezoelectric composite vibration layer, causing the support plate to extend from the outer ring body toward the center of the outer ring body;

4. The method of manufacturing a MEMS structure according to claim 3, wherein in the step of etching and dividing the piezoelectric composite vibration layer, fixed ends of adjacent diaphragms are made different.

5. The method of manufacturing a MEMS structure according to claim 3, wherein in the step of etching and dividing the piezoelectric composite vibration layer, fixed ends of at least two adjacent diaphragms are made the same.

6. The method of manufacturing a MEMS structure according to claim 3, wherein in the step of etching and dividing the piezoelectric composite vibration layer, a projection profile of a free end of each of the diaphragms in a vibration direction is located inside the corresponding cavity.

7. The method of manufacturing a MEMS structure according to claim 6, wherein in the step of etching and dividing the piezoelectric composite vibration layer, a projected contour of a free end of each of the diaphragms in the vibration direction is made to be the same shape as a projected contour of the corresponding cavity in the vibration direction.

8. The method of manufacturing a MEMS structure according to claim 1, wherein the method of forming the piezoelectric composite vibration layer includes: