CN110149582B - Preparation method of MEMS structure - Google Patents

Abstract

The present application provides a method for manufacturing a MEMS (Micro Electro Mechanical System) structure, comprising: forming a plurality of parallel first grooves by etching on the front surface of a substrate, and depositing and forming a piezoelectric composite vibration layer on the substrate, wherein, The piezoelectric composite vibration layer formed on the bottom and sidewall of the first groove constitutes a corrugated portion, wherein the corrugated portion is formed on the entire surface area of the piezoelectric composite vibration layer; The second groove is formed by etching on the substrate; the backside of the substrate is etched to form a cavity, the second groove is adjacent to the periphery of the cavity, and the piezoelectric composite vibration layer is formed directly above the cavity, and is located in the second groove. The portion of the substrate between the groove and the cavity supports the piezoelectric composite vibration layer. The manufactured MEMS structure improves the displacement and deformation of the piezoelectric composite vibration layer under the action of sound pressure, reduces the residual stress, and further improves the sensitivity of the MEMS structure.

Description

A kind of preparation method of MEMS structure

technical field

The present application relates to the field of semiconductor technology, and in particular, to a method for preparing a MEMS (abbreviation for MicroelectroMechanical Systems, that is, a microelectromechanical system) structure.

Background technique

MEMS microphones (microphones) mainly include two types: capacitive and piezoelectric. MEMS piezoelectric microphone is a microphone prepared by using micro-electromechanical system technology and piezoelectric film technology. Due to the use of semiconductor planar technology and bulk silicon processing technology, it is small in size, small in volume and good in consistency. At the same time, compared with the condenser microphone, it has the advantages of no bias voltage, large operating temperature range, dustproof and waterproof, etc., but its sensitivity is relatively low, which restricts the development of MEMS piezoelectric microphones. Among them, the large residual stress of the vibrating membrane is an important reason for its low sensitivity.

For the problem of how to reduce the residual stress of the piezoelectric MEMS structure and improve the deformation of the vibrating membrane in the related art, no effective solution has been proposed yet.

SUMMARY OF THE INVENTION

In view of the problem of relatively large residual stress in the related art, the present application proposes a method for fabricating a MEMS structure, which can effectively reduce the residual stress.

The technical solution of the present application is realized as follows:

According to one aspect of the present application, there is provided a method of fabricating a MEMS (Micro Electro Mechanical System) structure, comprising:

A plurality of parallel first grooves are formed by etching on the front surface of the substrate, and a piezoelectric composite vibration layer is deposited on the substrate, wherein the the piezoelectric composite vibration layer constitutes a corrugated portion, wherein the corrugated portion is formed on the entire surface area of the piezoelectric composite vibration layer;

At the periphery of the piezoelectric composite vibration layer, a second groove is formed by etching on the exposed substrate;

The backside of the substrate is etched to form a cavity, the second groove is disposed adjacent to the periphery of the cavity, the piezoelectric composite vibration layer is formed directly above the cavity, and is located on the first The portion of the substrate between the two grooves and the cavity supports the piezoelectric composite vibration layer.

Wherein, the method for forming the piezoelectric composite vibration layer includes:

depositing a support material on the substrate having the first groove to form a vibration support layer;

depositing a first electrode material on the vibration support layer, and 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;

A second electrode material is deposited over the first piezoelectric layer, and the second electrode material is patterned to form a second electrode layer.

Wherein, the vibration support layer, the first electrode layer, the first piezoelectric layer, and the second electrode layer formed on the bottom and sidewalls of the first groove constitute the corrugated portion.

Wherein, the first electrode layer, the first piezoelectric layer and the second electrode layer formed on the bottom and sidewalls of the first groove are removed by etching, and the first electrode layer, the first piezoelectric layer and the second electrode layer are left on the bottom of the first groove. The vibration support layer on the bottom and side walls constitutes the corrugated portion.

Wherein, the center plane of one of the first grooves passes through the center point of the piezoelectric composite vibration layer, and the piezoelectric composite vibration layer is divided into two regions.

Wherein, the plurality of parallel first grooves are arranged at equal intervals.

Wherein, the method for forming the piezoelectric composite vibration layer further includes:

Etching the substrate to form a plurality of parallel third grooves, wherein the center plane of one of the third grooves passes through the center point of the piezoelectric composite vibration layer, the first groove and the third groove The slot divides the piezoelectric composite vibration layer into four regions;

The piezoelectric composite vibration layer is formed by depositing on the substrate having the first groove and the third groove.

Wherein, the method of manufacturing the MEMS structure further includes etching the first electrode layer and the second electrode layer respectively to form a fourth groove, and the fourth groove connects the first electrode layer and the second electrode layer. The two electrode layers are separated into at least two partitions, and the partitions of the first electrode layer and the second electrode layer corresponding to each other constitute an electrode layer pair, and then a plurality of the electrode pairs are connected in series.

Wherein, the vibration support layer includes a single-layer or multi-layer composite film structure composed of silicon nitride, silicon oxide, monocrystalline silicon, and polycrystalline silicon.

Wherein, the vibration support layer includes a piezoelectric material layer and electrode material layers located above and below the piezoelectric material layer, wherein the piezoelectric material layer includes zinc oxide, aluminum nitride, organic piezoelectric film, zirconium One or more layers of lead titanate (PZT) or perovskite piezoelectric films.

Wherein, the method of fabricating the MEMS structure further includes etching to form a plurality of through holes penetrating the piezoelectric composite vibration layer, wherein the plurality of through holes are closer to the piezoelectric composite than the corrugated portion The center of the vibration layer.

Wherein, etching forms the plurality of through holes continuously penetrating the vibration support layer, the first electrode layer, the first piezoelectric layer and the second electrode layer.

Wherein, etching forms a fifth groove extending from the upper surface of the second electrode layer to the lower surface of the first electrode layer, and the plurality of through holes are located in the fifth groove, and the plurality of through holes are located in the fifth groove. The through holes only penetrate through the vibration support layer.

Wherein, the dividing line formed by connecting the plurality of through holes passes through the center of the piezoelectric composite vibration layer, wherein the center plane of at least one of the first grooves passes through the center point of the piezoelectric composite vibration layer, The center plane of the first groove is coplanar with the dividing line.

In the MEMS structure manufactured by the above method, the piezoelectric composite vibration layer is formed just above the cavity and in the middle of the second groove, so that part of the substrate material between the second groove and the cavity supports the piezoelectric composite Therefore, the displacement and deformation of the piezoelectric composite vibration layer under the action of sound pressure are improved, the residual stress is reduced, and the MEMS structure is improved. sensitivity.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present application. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without any creative effort.

Various aspects of the present application may be better understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, in accordance with standard industry practice, the various components are not drawn to scale and are used for illustration purposes only. In fact, the dimensions of the various components may be arbitrarily increased or decreased for clarity of discussion.

1 is a schematic perspective view of a MEMS structure according to some embodiments of the present application;

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

Fig. 3 is the enlarged schematic diagram of the corrugated part shown in Fig. 2;

4, 5 and 7 are cross-sectional views of intermediate stages of forming a MEMS structure according to some embodiments of the present application;

6 is a schematic perspective view of a MEMS structure according to other embodiments of the present application.

Detailed ways

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. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art fall within the protection scope of this application.

The following disclosure provides many different embodiments or examples for implementing different features of the present application. Specific examples of elements and arrangements are described below to simplify the present application. Of course these are only examples and are not intended to be limiting. For example, the dimensions of the elements are not limited to the disclosed ranges or values, but may depend on process conditions and/or desired properties of the device. Furthermore, in the following description, forming the first part over or on the second part may include embodiments in which the first part and the second part are formed in direct contact, and may also include an embodiment that may be formed between the first part and the second part Additional parts so that the first part and the second part may not be in direct contact with each other. Various components may be arbitrarily drawn in different sizes for simplicity and clarity.

Also, for ease of description, spatially relative terms such as "beneath", "below", "lower", "above" ", "upper", etc. may be used herein to describe the relationship of one element or component to another (or other) elements or components as illustrated in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Additionally, the term "made of" may mean "comprising" or "consisting of."

According to the embodiments of the present application, a MEMS structure 100 is provided, which can reduce the low-frequency sound leakage while reducing the residual stress and increasing the strain of the piezoelectric composite vibration layer 20, and improve the stability of the microphone operation and preparation.

Referring to FIGS. 1 and 2 , wherein FIG. 2 is a cross-sectional perspective view taken along line A-A of FIG. 1 . 1 and 2 illustrate a MEMS structure according to one embodiment of the present application. The MEMS structure will be described in detail below.

The MEMS structure includes a substrate 10 , wherein the substrate 10 has a cavity 11 disposed adjacently and a first groove 12 formed at the periphery of the cavity 11 . Substrate 10 includes silicon or any suitable silicon-based compound or derivative (eg, silicon wafer, SOI, polysilicon on SiO2/Si).

The piezoelectric composite vibration layer 20 is formed right above the cavity 11 and in the middle of the first groove 12 . And the piezoelectric composite vibration layer 20 has a corrugated portion 26 . Referring to FIG. 3 , FIG. 3 is an enlarged schematic view of the corrugated portion 26 . The corrugated portion 26 will be described in detail below.

In the MEMS structure of the above embodiment, the piezoelectric composite vibration layer 20 is formed right above the cavity 11 and located in the middle of the first groove 12 , so that part of the substrate material between the first groove 12 and the cavity 11 The piezoelectric composite vibration layer 20 is supported, so that the piezoelectric composite vibration layer 20 is transformed from a clamped state to a quasi-simply supported state. Therefore, the displacement and deformation of the piezoelectric composite vibration layer 20 under the action of sound pressure are improved, thereby improving the performance of the piezoelectric composite vibration layer 20. Sensitivity of MEMS structures. Moreover, the corrugated portion 26 of the piezoelectric composite vibrating layer 20 can make the “tight” vibrating film “soft”, so that under the same sound pressure, each area of the piezoelectric composite vibrating layer 20 obtains a larger Displacement and deformation, thereby further improving the sensitivity of the MEMS structure.

The process method for forming the MEMS structure will be described in detail below. For clearer description, the following FIGS. 4 , 5 and 7 are not drawn according to the scale shown in FIG. 1 , but the size of the first groove 12 is relatively enlarged for easy understanding and description.

Referring generally to FIG. 4 , in some embodiments, the substrate 10 is etched to form a plurality of parallel second grooves 13 and an additional plurality of parallel third grooves 14 . The center plane of one of the second grooves 13 passes through the center point of the substrate 10 , and the second groove 13 divides the substrate 10 into two regions. And the center plane of one of the third grooves 14 passes through the center point of the substrate 10 , and the second groove 13 and the third groove 14 divide the substrate 10 into four regions. In some embodiments, a plurality of parallel second grooves 13 are arranged at equal intervals. In some embodiments, the plurality of parallel third grooves 14 are arranged at equal intervals.

Next, see Figure 5. A vibration support layer 24 , a first electrode layer 21 , a first piezoelectric layer 22 and a second electrode layer 23 are sequentially deposited and patterned on the substrate 10 having the second groove 13 and the third groove 14 . Among them, the vibration support layer 24 , the first electrode layer 21 , the first piezoelectric layer 22 and the second electrode layer 23 constitute the piezoelectric composite vibration layer 20 . It is worth noting that the piezoelectric composite vibration layer 20 includes portions formed on the bottoms and side walls of the second groove 13 and the third groove 14 , ie, the corrugated portion 26 shown in FIG. 3 .

Since the piezoelectric composite vibration layer 20 has portions formed on the bottoms and side walls of the second groove 13 and the third groove 14 , ie, corrugated portions 26 , these corrugated portions 26 divide the piezoelectric composite vibration layer 20 into four The edges of each region are connected by the corrugated portion 26, so that the stress of the entire piezoelectric composite vibration layer 20 is released, and at the same time, the effect of a cantilever-like structure is achieved, so that the “tight” piezoelectric composite vibration layer 20 Turn soft". In this way, under the action of the same sound pressure, each region of the piezoelectric composite vibration layer 20 obtains a larger displacement and strain, and also achieves the effect of improving the sensitivity of the MEMS structure.

In other embodiments, the first electrode layer 21 , the first piezoelectric layer 22 and the third electrode layer 23 in the second groove 13 and the third groove 14 may be removed by etching. Only the vibration support layer 24 remains in the second groove 13 and the third groove 14 . In this case, the corrugated portion 26 includes only the material of the vibration support layer 24 .

In some embodiments, the substrate 10 may have only the second groove 13 and not the third groove 14 .

In some embodiments, the vibration support layer 24 includes a single-layer or multi-layer composite film structure composed of silicon nitride (Si ₃ N ₄ ), silicon oxide, monocrystalline silicon, polycrystalline silicon, or other suitable supporting materials.

In some embodiments, the vibration support layer 24 may include a piezoelectric material layer and electrode material layers above and below the piezoelectric material layer. Wherein, the piezoelectric material layer includes one or more layers of zinc oxide, aluminum nitride, organic piezoelectric film, lead zirconate titanate (PZT), perovskite piezoelectric film, or other suitable materials. In this case, the vibration support layer 24 simultaneously functions as support and piezoelectricity.

In some embodiments, the first piezoelectric layer 22 can convert the applied pressure into a voltage, and the first electrode layer 21 and the second electrode layer 23 can transmit the generated voltage to other integrated circuit devices. In some embodiments, the first piezoelectric layer 22 includes zinc oxide, aluminum nitride, organic piezoelectric films, lead zirconate titanate (PZT), perovskite piezoelectric films, or other suitable materials. The first electrode layer 21 and the second electrode layer 23 include aluminum, gold, platinum, molybdenum, titanium, chromium and their composite films or other suitable materials.

6, in some embodiments in which the second groove 13 and the third groove 14 are not formed in the middle portion of the substrate 10, the middle portion of the substrate 10 is etched to form a continuous penetrating vibration support layer 24 , a plurality of through holes 25 of the first electrode layer 21 , the first piezoelectric layer 22 and the second electrode layer 23 . Alternatively, a fifth groove (not shown in the figure) extending from the upper surface of the second electrode layer 23 to the lower surface of the first electrode layer 21 may be formed by etching in the middle portion of the substrate 10, and the plurality of through holes 25 are located In the fifth groove, in this case, the plurality of through holes 25 only penetrate the vibration support layer 24 . In other words, the plurality of through holes 25 in the embodiment of the present application can continuously penetrate four layers such as the vibration support layer 24 , the first electrode layer 21 , the first piezoelectric layer 22 , and the second electrode layer 23 , or can only A vibration support layer 24 is penetrated.

The plurality of through holes 25 are closer to the center of the piezoelectric composite vibration layer 20 than the corrugated portion 26 . In some embodiments, the dividing line formed by connecting the plurality of through holes 25 passes through the center point of the piezoelectric composite vibration layer 20 . The center plane of at least one second groove 13 passes through the center point of the piezoelectric composite vibration layer 20 , and the center plane of the second groove 13 is coplanar with the dividing line. The plurality of through holes 25 release the stress in the middle portion of the piezoelectric composite vibration layer 20, and at the same time achieve the effect of a cantilever-like structure. In some embodiments, the step of forming the plurality of vias 25 may be omitted or skipped.

Next, in some embodiments, the vibration support layer 24 , the first electrode layer 21 , the first piezoelectric layer 22 and the second electrode layer 23 are etched, thereby exposing portions of the substrate 10 .

Referring to FIG. 7 , in some embodiments, on the periphery of the first electrode layer 21 , the first piezoelectric layer 22 and the second electrode layer 23 , a first electrode layer extending into the substrate 10 is etched on the exposed substrate 10 and formed A groove 12 . In other embodiments, the first electrode layer 21 , the first piezoelectric layer 22 and the second electrode layer 23 may be etched to expose the peripheral portion of the vibration support layer 24 . Next, a groove extending into the substrate 10 is formed by etching on the periphery of the vibration support layer 24 , and the part of the groove located in the substrate 10 constitutes the first groove 12 . The portion of the substrate 10 and the portion of the vibration support layer 24 outside the first groove 12 are then removed, resulting in the first groove 12 shown in FIG. 7 .

In some embodiments, the backside of the substrate 10 is etched to form the cavity 11 , and the first groove 12 is provided at the periphery of the cavity 11 . Also, the vibration support layer 24 , the first electrode layer 21 , the first piezoelectric layer 22 and the second electrode layer 23 are formed right above the cavity 11 . Specifically, an insulating material (not shown in the figure) and a photoresist are sequentially deposited on the backside of the substrate 10 by a standard photolithography process, the photoresist is patterned to form a mask layer, and the exposed insulating material and photoresist are etched. substrate 10, thereby forming a cavity 11. The insulating material on the backside of the substrate 10 is then removed. In FIG. 7 , the size of the portion of the substrate 10 located between the second groove 13 and the cavity 11 is small, so that the piezoelectric composite vibration layer 20 and the substrate 10 can only be contacted and supported in a small area, thereby improving the The displacement and deformation of the piezoelectric composite vibration layer 20 under the action of sound pressure.

Based on the above embodiment, referring to FIG. 3 , after the cavity 11 is formed, the piezoelectric composite vibration layer 20 is formed into a corrugated portion 26 as shown in FIG. 3 . The piezoelectric composite vibration layer 20 is formed just above the cavity 11 and located in the middle of the first groove 12, so that part of the substrate material between the first groove 12 and the cavity 11 supports the piezoelectric composite vibration layer 20, and then The piezoelectric composite vibration layer 20 is transformed from a clamped state to a quasi-simply supported state, therefore, the displacement and deformation of the piezoelectric composite vibration layer 20 under the action of sound pressure are improved, thereby improving the sensitivity of the MEMS structure.

Further, the method of manufacturing the MEMS structure further includes etching the first electrode layer 21 and the second electrode layer 23 respectively to form a fourth groove (not shown in the figure), and the fourth groove connects the first electrode layer 21 and the second electrode layer 21 and the second electrode layer 23 respectively. The electrode layer 23 is separated into at least two sub-regions, and the sub-regions of the first electrode layer 21 and the second electrode layer 23 corresponding to each other constitute electrode layer pairs, and then a plurality of electrode layer pairs are connected in series, so that a plurality of piezoelectric films of cantilever beam structure are formed. The transducers are electrically connected in series, thereby further improving the sensitivity of the MEMS structure.

To sum up, with the help of the above technical solutions of the present application and the method for manufacturing a MEMS structure, the residual stress of the piezoelectric composite vibration layer 20 is reduced, and the deformation of the piezoelectric composite vibration layer 20 under the action of sound pressure is improved, Thus, the sensitivity of the MEMS structure is improved.

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the scope of the present application. within the scope of protection.

Claims (14)

1. a method of manufacturing MEMS structure, is characterized in that, comprises: A plurality of parallel first grooves are formed by etching on the front surface of the substrate, and a piezoelectric composite vibration layer is deposited on the substrate, wherein the The piezoelectric composite vibration layer constitutes a corrugated portion, wherein the corrugated portion is formed on the entire surface area of the piezoelectric composite vibration layer, wherein one of the first grooves is in the radial direction of the piezoelectric composite vibration layer, and dividing the piezoelectric composite vibration layer into at least two regions; The backside of the substrate is etched to form a cavity, and the piezoelectric composite vibration layer is formed just above the cavity. 2. The method for manufacturing a MEMS structure according to claim 1, wherein the method for forming the piezoelectric composite vibration layer comprises: depositing a support material on the substrate having the first groove to form a vibration support layer; depositing a first electrode material on the vibration support layer, and 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; A second electrode material is deposited over the first piezoelectric layer, and the second electrode material is patterned to form a second electrode layer. 3 . The method for manufacturing a MEMS structure according to claim 2 , wherein the vibration support layer, the first electrode layer, the first A piezoelectric layer and the second electrode layer constitute the corrugated portion. 4 . The method of claim 2 , wherein the first electrode layer and the first piezoelectric layer formed on the bottom and sidewalls of the first groove are removed by etching. 5 . and the second electrode layer, the vibration support layer remaining on the bottom and side walls of the first groove constitutes the corrugated portion. 5 . The method of claim 1 , wherein the plurality of parallel first grooves are arranged at equal intervals. 6 . 6. The method for manufacturing a MEMS structure according to claim 1, wherein the method for forming the piezoelectric composite vibration layer further comprises: The substrate is etched to form a plurality of parallel third grooves, wherein one of the third grooves is in the radial direction of the piezoelectric composite vibration layer, and the first groove and the third groove connect the The piezoelectric composite vibration layer is divided into at least four regions; The piezoelectric composite vibration layer is formed by depositing on the substrate having the first groove and the third groove. 7. The method of manufacturing a MEMS structure according to claim 2, wherein the method of manufacturing the MEMS structure further comprises etching the first electrode layer and the second electrode layer respectively to form a fourth groove, The fourth groove separates the first electrode layer and the second electrode layer into at least two sub-regions, and the sub-regions of the first electrode layer and the second electrode layer corresponding to each other constitute an electrode layer pair, Then, a plurality of the electrode layer pairs are serially connected in series. 8 . The method of claim 2 , wherein the vibration support layer comprises a single-layer or multi-layer composite film structure composed of silicon nitride, silicon oxide, monocrystalline silicon, and polycrystalline silicon. 9 . 9 . The method of claim 2 , wherein the vibration support layer comprises a piezoelectric material layer and electrode material layers located above and below the piezoelectric material layer, wherein the pressure The electrical material layer includes one or more layers of zinc oxide, aluminum nitride, organic piezoelectric films, lead zirconate titanate (PZT), or perovskite piezoelectric films. 10 . The method for manufacturing a MEMS structure according to claim 2 , wherein the method for manufacturing the MEMS structure further comprises etching to form a plurality of through holes penetrating the piezoelectric composite vibration layer, wherein the plurality of Each through hole is closer to the center of the piezoelectric composite vibration layer than the corrugated portion. 11 . The method of claim 10 , wherein etching is formed to continuously penetrate the vibration support layer, the first electrode layer, the first piezoelectric layer and the second electrode layer. 12 . of the plurality of through holes. 12. The method of claim 10, wherein etching forms a fifth groove extending from the upper surface of the second electrode layer to the lower surface of the first electrode layer, and the The plurality of through holes are located in the fifth groove, and the plurality of through holes only penetrate the vibration support layer. 13 . The method for manufacturing a MEMS structure according to claim 10 , wherein a dividing line formed by connecting the plurality of through holes passes through the center of the piezoelectric composite vibration layer, wherein at least one of the first The center plane of the groove passes through the center point of the piezoelectric composite vibration layer, and the center plane of the first groove is coplanar with the dividing line. 14 . The method for manufacturing a MEMS structure according to claim 1 , wherein on the periphery of the piezoelectric composite vibration layer, a second groove is formed on the exposed substrate by etching, and the second groove is formed. 15 . A groove is disposed adjacent to the periphery of the cavity, and the substrate at a portion between the second groove and the cavity supports the piezoelectric composite vibration layer.

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