CN113301484A - MEMS structure and manufacturing method thereof - Google Patents

Abstract

The application discloses MEMS structure includes: a substrate having a cavity; a piezoelectric composite vibration layer formed over the substrate and covering the cavity, wherein the piezoelectric composite vibration layer over the cavity has a gap extending from an upper surface of the piezoelectric composite vibration layer through to a lower surface of the piezoelectric composite vibration layer, and the gap communicates with the cavity, the gap dividing the piezoelectric composite vibration layer into a cantilever beam film at the periphery and a diaphragm at the center. The application improves the sensitivity and the reliability of the MEMS structure. In addition, the application also provides a manufacturing method of the MEMS structure.

Description

MEMS structure and manufacturing method thereof

Technical Field

The present application relates to the field of micro-mechanical technology, and more particularly, to a MEMS device

(Micro-Electro-Mechanical System) structure and method of making the same.

Background

Piezoelectric microphones have many advantages over conventional capacitive MEMS microphones, including dust resistance, water resistance, and higher maximum output sound pressure (AOP). The method is limited by a sputtering growth process of the piezoelectric film layer, the stress of the piezoelectric film layer is large and is distributed unevenly, and large gradient stress exists along the thickness direction of the growth of the piezoelectric film layer. Due to the existence of the stress and the gradient stress, the warping, the deformation and the like of the diaphragm cannot be avoided no matter the periphery of the piezoelectric composite vibration layer is fixed or the local fixation is carried out in the piezoelectric composite vibration layer. The deformation and warpage also affect the reliability and sensitivity of the piezoelectric microphone.

Aiming at the problems of low reliability and low sensitivity of the piezoelectric MEMS microphone in the related technology, no effective solution is provided at present.

Disclosure of Invention

The MEMS structure is provided for solving the problems of low reliability and low sensitivity of a piezoelectric MEMS microphone in the related art, and can improve the reliability and the 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 cavity;

a piezoelectric composite vibration layer formed over the substrate and covering the cavity, wherein the piezoelectric composite vibration layer over the cavity has a gap extending from an upper surface of the piezoelectric composite vibration layer through to a lower surface of the piezoelectric composite vibration layer, and the gap communicates with the cavity, the gap dividing the piezoelectric composite vibration layer into a cantilever beam film at the periphery and a diaphragm at the center.

Wherein the piezoelectric composite vibration layer includes:

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

a first electrode layer formed over the support layer;

a first piezoelectric layer formed over the first electrode layer;

a second electrode layer formed over the first piezoelectric layer,

wherein the gap extends from an upper surface of the second electrode layer to a lower surface of the support layer.

And the vibrating diaphragm is fixed above the substrate through uniformly arranged supporting angles.

The cantilever beam films are arranged at uniform intervals and are fan-shaped.

The cantilever beam films are arranged at uniform intervals and are arc-shaped, oval, triangular or other polygons.

In another aspect, the present application further provides a method for manufacturing a MEMS structure, including:

providing a substrate;

forming a support layer, a first electrode layer, a first piezoelectric layer, and a second electrode layer in this order over the substrate, and forming a gap extending from an upper surface of the second electrode layer to a lower surface of the support layer;

the substrate is etched from a bottom of the substrate to form a cavity, and the cavity is in communication with the gap.

Wherein an etch stop layer is formed over the substrate prior to forming the support layer, the etch stop layer being removed after forming the cavity.

Based on the MEMS structure, the gaps are arranged on the piezoelectric composite vibration layer to form a peripheral cantilever beam film and a central vibration film, so that the influence of deformation and warping on the reliability and sensitivity of the MEMS structure is reduced. The cantilever beam film and the vibrating diaphragm form higher voltage, so that the sensitivity of the MEMS structure is improved, and the reliability of the MEMS structure is improved. In addition, the application also provides a manufacturing method 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 perspective view of a MEMS structure, in accordance with some embodiments;

FIG. 2 is a cross-sectional perspective view of the MEMS structure of FIG. 1;

FIG. 3 is a top view of the MEMS structure of FIG. 1;

FIG. 4 illustrates a perspective view of a MEMS structure according to some embodiments;

FIG. 5 is a top view of the MEMS structure of FIG. 4;

fig. 6-12 are cross-sectional views of intermediate stages in the fabrication of a MEMS structure.

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, a MEMS structure is provided for a sensor such as a microphone or other actuator. The MEMS structure will be described in detail below.

Referring to fig. 1, 2 and 3, the MEMS structure includes a substrate 10 having a cavity 11, the substrate 10 comprising silicon or any suitable silicon-based compound or derivative (e.g., silicon wafer, SOI, polysilicon on SiO 2/Si).

The piezoelectric composite vibration layer is formed over the substrate 10 and covers the cavity 11. The piezoelectric composite vibration layer above the cavity 11 has a gap 26, the gap 26 extending from the upper surface of the piezoelectric composite vibration layer through to the lower surface of the piezoelectric composite vibration layer, the gap 26 dividing the piezoelectric composite vibration layer into a peripheral cantilever membrane 30 and a central diaphragm 40.

The diaphragm 40 is fixed above the substrate 10 via evenly arranged support corners. In some embodiments, the cantilever membranes 30 are uniformly spaced apart, and the cantilever membranes 30 are fan-shaped (as shown in fig. 3). In some embodiments, the cantilever membranes 30 are uniformly spaced, and the cantilever membranes 30 have a circular arc shape (as shown in fig. 4), an oval shape, a triangular shape, or other polygonal shapes. And the number of the cantilever beam membranes 30 is at least one or more. The fixed end of the cantilever membrane 30 is attached to the substrate 10 and the free end is suspended over the cavity 11.

Based on the MEMS structure, the gap 26 is arranged on the piezoelectric composite vibration layer, the cantilever membrane 30 at the periphery and the vibration membrane 40 at the center are formed, so that the influence of deformation and warping on the reliability and sensitivity of the MEMS structure is reduced, the cantilever membrane 30 and the vibration membrane 40 form higher voltage, the sensitivity of the MEMS structure is improved, and the reliability of the MEMS structure is improved.

In the embodiment where the piezoelectric composite vibration layer is a single crystal wafer, the piezoelectric composite vibration layer includes the vibration support layer 21, the first electrode layer 22, the first piezoelectric layer 23, and the second electrode layer 24. Wherein a vibration support layer 21 is formed over the substrate 10 and covers the cavity 11. The first electrode layer 22 is formed over the vibration support layer 21. The first piezoelectric layer 23 is formed over the first electrode layer 22. The second electrode layer 24 is formed over the first piezoelectric layer 23. In other words, the gap 26 extends from the upper surface of the second electrode layer to the lower surface of the support layer, so that the gap 26 communicates with the 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 addition, the piezoelectric composite vibration layer may also be a bimorph structure, and the piezoelectric composite vibration layer may include a third electrode layer, a second piezoelectric layer, a fourth electrode layer, a third piezoelectric layer, and a fifth electrode layer that are stacked in this order from bottom to top. The piezoelectric composite vibration layer with the double-wafer structure also realizes the effect of converting sound energy into electric energy.

In some embodiments, the piezoelectric composite vibration layer further includes an etch stop layer 25, the etch stop layer 25 being formed between the vibration support layer 21 and the substrate 10. The etch stop layer 25 may also be removed.

In some embodiments, the vibration support layer 21 comprises silicon nitride (Si)₃N₄) Silicon oxide, monocrystalline silicon, polycrystalline silicon, or other suitable support material. The first piezoelectric layer 23 includes zinc oxide, aluminum nitride, an organic piezoelectric film, lead zirconate titanate (PZT), a perovskite-type piezoelectric film, or other suitable materials. 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.

In summary, the present application provides an MEMS structure, wherein the gap 26 is disposed on the piezoelectric composite vibration layer to form the peripheral cantilever membrane 30 and the peripheral vibrating membrane 40, so as to reduce the influence of deformation and warpage on the reliability and sensitivity of the MEMS structure, and the cantilever membrane 30 and the vibrating membrane 40 form a higher voltage, thereby improving the sensitivity of the MEMS structure and improving the reliability of the MEMS structure.

On the other hand, the application also provides a manufacturing method for forming the MEMS structure, and the flow is as follows:

referring to fig. 6, step S1, a substrate 10 is provided.

In step S2, an etch stop layer 25 is formed over the substrate 10, the material of the etch stop layer 25 including silicon oxide. The etch stop layer 25 may be formed by thermal oxidation, pecvd (Vapor deposition by plasma Enhanced Chemical Vapor deposition). In other embodiments, step S2 may be skipped or omitted.

Referring to fig. 7, 8, step S3, the vibration support layer 21, the first electrode layer 22, the first piezoelectric layer 23, and the second electrode layer 24 are sequentially formed over the etch stop layer 25.

Referring to fig. 9, in step S4, metal pads 27 are led out to the first electrode layer 22 and the second electrode layer 24.

Referring to fig. 10, step S5, the gap 26 extending from the upper surface of the second electrode layer 24 to the lower surface of the vibration support layer 21 is etched.

Referring to fig. 11, step S6, the substrate 10 is etched from the bottom of the substrate 10 to form the cavity 11, and the etching of the substrate 10 is terminated at the etch stop layer 25.

Referring to fig. 12, step S7, the etch stop layer 25 is etched away in other ways until the cavity 11 is in communication with the gap 26.

Based on the above manufacturing method, the above MEMS structure is obtained. The MEMS structure has high sensitivity and reliability.

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 (7)

1. A MEMS structure, comprising:

a substrate having a cavity;

a piezoelectric composite vibration layer formed over the substrate and covering the cavity, wherein the piezoelectric composite vibration layer over the cavity has a gap extending from an upper surface of the piezoelectric composite vibration layer through to a lower surface of the piezoelectric composite vibration layer, and the gap communicates with the cavity, the gap dividing the piezoelectric composite vibration layer into a cantilever beam film at the periphery and a diaphragm at the center.

2. The MEMS structure of claim 1, wherein the piezoelectric composite vibration layer comprises:

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

a first electrode layer formed over the support layer;

a first piezoelectric layer formed over the first electrode layer;

a second electrode layer formed over the first piezoelectric layer,

wherein the gap extends from an upper surface of the second electrode layer to a lower surface of the support layer.

3. The MEMS structure of claim 1, wherein the diaphragm is fixed above the substrate via uniformly disposed support angles.

4. The MEMS structure of claim 3, wherein the cantilever membranes are evenly spaced and are fan-shaped.

5. The MEMS structure of claim 3, wherein the cantilever membranes are evenly spaced and have a circular arc, oval, triangular or other polygonal shape.

6. A method of fabricating a MEMS structure, comprising:

providing a substrate;

forming a support layer, a first electrode layer, a first piezoelectric layer, and a second electrode layer in this order over the substrate, and forming a gap extending from an upper surface of the second electrode layer to a lower surface of the support layer;

the substrate is etched from a bottom of the substrate to form a cavity, and the cavity is in communication with the gap.

7. The method of fabricating a MEMS structure according to claim 6, wherein an etch stop layer is formed over the substrate prior to forming the support layer, the etch stop layer being removed after forming the cavity.

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