Piezoelectric micropump based on MEMS (Micro Electro Mechanical System) process and preparation method thereof

Abstract

The invention discloses a piezoelectric micropump based on MEMS technology and a preparation method thereof, the main body structure of the pump comprises a third structure layer, a second structure layer, a first structure layer and a piezoelectric excitation unit which are stacked in sequence, a piezoelectric excitation power supply comprises a bottom electrode, a piezoelectric film and a top electrode which are stacked in sequence, the second structure layer is internally provided with a cavity, and the first structure layer and the top electrode are stacked in sequence. The first structural layer in the longitudinal projection area range of the port, close to the first structural layer, of the cavity is a vibrating diaphragm, and a first channel communicated with the cavity is formed in the position, close to the third structural layer, of the side wall of the second structural layer. The preparation method comprises the following steps: preparing tablets; growing and patterning a piezoelectric layer; patterning the bottom silicon; according to the embodiment of the invention, the piezoelectric driving structure and the flow channel structure are all processed, manufactured and integrally formed through a semiconductor material and a process by utilizing an MEMS (Micro Electro Mechanical System) process, the traditional bonding is replaced, and the problems of untight connection, air leakage and the like caused by assembly are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of pumps with flexible working elements, and in particular to a piezoelectric micropump based on MEMS technology and a preparation method thereof. Background Art

[0002] MEMS piezoelectric micropumps are a new type of fluid actuator. They do not require an additional drive motor, but instead utilize the inverse piezoelectric effect of piezoelectric film to deform the piezoelectric diaphragm. This deformation then creates a change in the volume of the pump chamber to achieve fluid output, or utilize the piezoelectric diaphragm to generate fluctuations to transfer liquids or gases.

[0003] In the existing technology, most piezoelectric pumps use piezoelectric ceramic sheets as driving components. The cavity, flow channel, air inlet structure, and air outlet structure are all made of metal, polymer, glass and other materials, and then glued and assembled. The process is complicated and the device consistency is low. During the assembly process, problems such as loose connections or air leakage are prone to occur.

[0004] In summary, the present application proposes a piezoelectric thin film micropump based on MEMS technology and its preparation process to solve the above-mentioned problems.

[0005] After searching, the Chinese patent application number is: CN202111290662.3, and the name is "A high-precision MEMS micropump based on piezoelectric diaphragm". It discloses a three-layer structure formed by etching and bonding processes with the pump body as the substrate. The main material is silicon. It is biocompatible and has higher precision than micropumps made of polymers such as PDMS. The shortcoming of this patent is that the three-layer structure is a bonding process, which affects the alignment between structures to a certain extent. Summary of the Invention

[0006] In order to solve the technical problems existing in the background technology, the present invention proposes a piezoelectric micropump based on MEMS technology and a preparation method thereof.

[0007] The present invention proposes a piezoelectric micropump based on MEMS technology, comprising a pump main structure, the pump main structure comprising a third structural layer, a second structural layer, a first structural layer and a piezoelectric excitation unit stacked in sequence, the piezoelectric excitation unit comprising a bottom electrode, a piezoelectric film and a top electrode stacked in sequence on the first structural layer;

[0008] A cavity is provided on the second structural layer, and the first structural layer within the longitudinal projection area of ​​the cavity close to the port of the first structural layer is a diaphragm. The cavity provides a vibration space for the diaphragm, and a first channel connected to the cavity is provided on the second structural layer.

[0009] As a further optimized solution of the present invention, the first structural layer is connected to the second structural layer via a first growth layer; and / or

[0010] The third structural layer is connected to the second structural layer through the second growth layer; the first growth layer and / or the second growth layer is a silicon oxide structural layer.

[0011] As a further optimized solution of the present invention, the third structure layer, the second structure layer and the first structure layer are all silicon structure layers.

[0012] As a further optimized solution of the present invention, the cavity is a truncated cone structure, and the port area of ​​the cavity close to the first structural layer is smaller than the port area of ​​the cavity close to the third structural layer.

[0013] As a further optimized solution of the present invention, when the medium flowing through the cavity is gas, it also includes a packaging structure, which is used to encapsulate the pump main structure, an air inlet is opened on the top of the packaging structure, and an air outlet is opened on the side wall of the packaging structure corresponding to the position of the first channel.

[0014] As a further optimized solution of the present invention, a second channel communicating with the cavity is opened on the side wall of the bottom of the second structural layer opposite to the first channel, that is, the second channel is opposite to the first channel.

[0015] As a further optimized solution of the present invention, the cross-sectional area of ​​the first channel gradually decreases from the side away from the cavity to the side close to the cavity; and / or

[0016] The cross-sectional area of ​​the second channel gradually increases from the side away from the cavity to the side close to the cavity.

[0017] As a further optimized solution of the present invention, the specifications of the second channel are greater than those of the first channel, and the specifications include one or more of width, height, and volume.

[0018] As a further optimized solution of the present invention, when the medium flowing through the cavity is gas, the piezoelectric micropump also includes a packaging structure, an air outlet is opened at the position of the packaging structure corresponding to the first channel, and an air inlet is opened at the top of the packaging structure near the second channel.

[0019] As a further optimized solution of the present invention, there are at least two groups of cavities, and at least two groups of the cavities are distributed in a linear array on the second structural layer. Each group of the cavities has a first channel and a second channel. There is a piezoelectric excitation unit above each group of cavities. Each group of cavities provides a vibration space for the corresponding diaphragm, and at least two groups of the cavities are connected.

[0020] As a further optimized solution of the present invention, at least two groups of the cavities are connected in series, the first channel of one cavity in two adjacent groups of the cavities is connected to the second channel of the other cavity, and the medium is ejected after multiple pressurizations.

[0021] As a further optimized solution of the present invention, at least two groups of the cavities are connected in parallel, a first flow channel and a second flow channel are provided on the second structural layer, the first channels of at least two groups of cavities are connected to the second flow channel, and the second channels of at least two groups of cavities are connected to the first flow channel, a medium inlet connected to the first flow channel is provided on the second structural layer, and a medium outlet connected to the second flow channel is provided on the second structural layer.

[0022] A method for preparing a piezoelectric micropump based on a MEMS process, for preparing the piezoelectric micropump as described above, comprises the following steps:

[0023] S1, preparing an SOI wafer, the SOI wafer including a bottom silicon layer, a buried oxide layer, and a top silicon layer stacked in sequence, wherein the bottom silicon layer is the second structural layer and the top silicon layer is the first structural layer;

[0024] S2, growing a piezoelectric excitation unit on the first structural layer;

[0025] S3, patterning the bottom silicon to form a cavity and a first channel;

[0026] S4, bottom packaging: making the third structural layer seal the cavity away from one end of the first structural layer.

[0027] In the present invention, the proposed piezoelectric micropump based on MEMS technology and its preparation method are compared with the prior art in which piezoelectric ceramic sheets are used as driving components, and the cavity, flow channel, air inlet structure, and air outlet structure are all made of metal, high molecular polymer, glass and other materials, and can only be achieved by bonding and assembly. Bonding and assembly will inevitably bring about problems such as complex procedures, poor consistency, high cost, and low yield, and at the same time cannot realize the development trend of miniaturization of piezoelectric pumps. The embodiment of the present invention uses MEMS technology to realize that the piezoelectric driving structure and the flow channel structure are all processed and manufactured by semiconductor materials and processes, and are integrally formed, replacing traditional bonding and assembly. The process is simple, the consistency is high, the cost is low, and the yield is high, and it also has the characteristics of miniaturization.

[0028] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic structural diagram of a piezoelectric micropump based on MEMS technology proposed in an embodiment of the present invention;

[0030] Figure 2 for Figure 1 Structural explosion diagram;

[0031] Figure 3 for Figure 1 sectional view of

[0032] Figure 4 for Figure 3 A top view of the second structural layer;

[0033] Figure 5 for Figure 1 Schematic diagram of the structure of the medium-pressure electric film;

[0034] Figure 6-8 A schematic diagram of another embodiment of a piezoelectric micropump based on MEMS technology proposed by the present invention;

[0035] Figure 9 A schematic diagram of another embodiment of a piezoelectric micropump based on MEMS technology proposed by the present invention;

[0036] Figure 10-11 A schematic diagram of another embodiment of a piezoelectric micropump based on MEMS technology proposed by the present invention;

[0037] Figure 12-13 A schematic diagram of another embodiment of a piezoelectric micropump based on MEMS technology proposed by the present invention;

[0038] Figure 14 A schematic diagram of another embodiment of a piezoelectric micropump based on MEMS technology proposed by the present invention;

[0039] Figure 15-16 A schematic diagram of another embodiment of a piezoelectric micropump based on MEMS technology proposed by the present invention;

[0040] Figure 17 A schematic diagram of another embodiment of a piezoelectric micropump based on MEMS technology proposed by the present invention;

[0041] Figure 18-20 A schematic diagram of another embodiment of a piezoelectric micropump based on MEMS technology proposed by the present invention;

[0042] Figure 21 A schematic diagram of another embodiment of a piezoelectric micropump based on MEMS technology proposed by the present invention;

[0043] Figure 22-24 for Figure 3 Schematic diagram of the process flow;

[0044] Figures 25-28 for Figure 9 Schematic diagram of the process flow.

[0045] In the figure: 1. Pump main structure; 11. Piezoelectric excitation unit; 111. Bottom electrode; 112. Piezoelectric film; 113. Top electrode; 12. First structural layer; 121. First growth layer; 13. Second structural layer; 131. Cavity; 132a. Second channel; 132b. First channel; 14. Third structural layer; 141. Second growth layer; 1A. First pump body; 1B. Second pump body; 21. First flow channel; 21a. First medium diversion inlet; 21b. Second medium diversion inlet; 21c. Medium inlet; 31. Second flow channel; 31a. First medium diversion outlet; 31b. Second medium diversion outlet; 31c. Medium outlet; 4. Packaging structure; 41. Air inlet; 42. Air outlet. DETAILED DESCRIPTION

[0046] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar symbols throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention, and are not to be construed as limiting the present invention.

[0047] Example 1

[0048] like Figure 1-Figure 4 A piezoelectric micropump based on MEMS technology is shown, comprising a pump main structure, wherein the pump main structure comprises a third structure layer 14, a second structure layer 13, a first structure layer 12 and a piezoelectric excitation unit 11 stacked in sequence;

[0049] See also Figure 5 The piezoelectric excitation unit 11 includes a bottom electrode 111, a piezoelectric film 112, and a top electrode 113 stacked in sequence, the bottom electrode 111 contacts the first structural layer 12, and the piezoelectric excitation unit is grown by a MEMS process;

[0050] A cavity 131 is provided on the second structural layer 13, which provides a space for the diaphragm to vibrate. The first structural layer 12 within the longitudinal projection area of ​​the cavity 131 near the port of the first structural layer 12 is the diaphragm. The piezoelectric film 112 drives the diaphragm to deform and vibrate through the piezoelectric effect. When the piezoelectric film causes the diaphragm to move away from the third structural layer 14, a negative pressure is formed inside the cavity 131; when the piezoelectric film causes the diaphragm to move toward the direction close to the third structural layer 14, a positive pressure is formed inside the cavity 131, instantaneously compressing the medium inside the cavity 131. A first channel 132b is opened at the bottom of the second structural layer 13. One end of the first channel 132b is connected to the cavity 131. The flow direction of the medium in the first channel 132b intersects with the axis of the cavity 131. Specifically, the flow direction of the medium in the first channel 132b is perpendicular to the axis of the cavity 131. The other end passes through the side wall of the second structural layer 13. When a negative pressure is formed in the cavity 131, the medium enters the cavity 131 through the first channel 132b. When a positive pressure is formed in the cavity 131, the medium in the cavity 131 is compressed, so that the medium forms a jet and is ejected through the first channel 132b.

[0051] Compared with the prior art, in which piezoelectric ceramic sheets are used as driving components, while the cavity, flow channel, air inlet structure, and air outlet structure are all made of metal, high polymer, glass, and other materials, and can only be achieved by bonding and assembly, which inevitably leads to problems such as complex procedures, poor consistency, high cost, and low yield, and at the same time cannot achieve the development trend of miniaturization of piezoelectric pumps, the embodiment of the present invention utilizes MEMS technology to realize that the piezoelectric driving structure and the flow channel structure are all processed and manufactured using semiconductor materials and processes, and are integrally formed, replacing traditional bonding and assembly, with simple procedures, high consistency, low cost, and high yield, while also having the characteristics of miniaturization;

[0052] In addition, the flow direction of the medium in the first channel 132b of the present invention intersects with the axis of the cavity 131. The first channel 132b is horizontal, and the axis of the cavity 131 is vertical, which further increases the overall accuracy.

[0053] Example 2

[0054] See also Figure 6 Based on the MEMS-based piezoelectric micropump of Example 1, the piezoelectric micropump in this embodiment is used as an air pump, that is, the medium flowing through the cavity 131 is gas. The piezoelectric micropump also includes a packaging structure 4, which is used to encapsulate the pump main structure 1. The packaging structure 4 has an air outlet 42 at a position corresponding to the first channel 132b, and an air inlet 41 at the top of the packaging structure 4. The medium in Example 1 is gas, and the gas flows through the first channel 132b into the cavity 131 through the air inlet 41. After forming a jet, the gas flows through the first channel 132b and is discharged from the air outlet 42, which can dissipate heat for the carrier.

[0055] Example 3

[0056] See also Figure 7-Figure 8 In the MEMS-based piezoelectric micropump of Example 1 or Example 2, a second channel 132a is provided on the sidewall of the bottom of the second structural layer 13 opposite to the first channel 132b. One end of the second channel 132a is connected to the cavity 131, and the other end passes through the sidewall of the second structural layer 13. When a negative pressure is formed in the cavity 131, the medium enters the cavity 131 through the second channel 132a. When a positive pressure is formed in the cavity 131, the medium in the cavity 131 is compressed, forming a jet and ejected through the first channel 132b, thereby dissipating heat from the carrier. Optionally, please refer to Figure 9 The cavity 131 is a truncated cone structure, and the inner diameter of the cavity 131 near the first structural layer 12 is smaller than the inner diameter of the cavity 131 near the third structural layer 14 .

[0057] See also Figure 10-11 Optionally, the cross-sectional area of ​​the first channel 132b gradually decreases from the side away from the cavity 131 to the side close to the cavity 131. Optionally, the cross-sectional area of ​​the second channel 132a gradually increases from the side away from the cavity 131 to the side close to the cavity 131, further increasing the accuracy of the piezoelectric micropump.

[0058] Example 4

[0059] See also Figure 12-13 Based on the MEMS-based piezoelectric micropump proposed in Example 3, the specifications of the second channel 132a are larger than those of the first channel 132b (the specifications here include parameters such as width, height and volume, and are not limited to a specific parameter). In order to ensure the formation of the jet, a sufficient amount of medium is ensured to enter the cavity 131.

[0060] Example 5

[0061] See also Figure 14 Based on the piezoelectric micropump based on MEMS technology proposed in Example 4, the piezoelectric micropump in this embodiment is used as an air pump, that is, the medium flowing through the cavity 131 is gas. The piezoelectric micropump also includes a packaging structure 4, and the packaging structure 4 has an outlet 42 at a position corresponding to the first channel 132b, and an inlet 41 is provided at the top of the packaging structure 4 near the second channel 132a. The medium in Example 4 is gas, and the gas flows through the second channel 132a through the inlet 41, forms a jet, flows through the first channel 132b, and is discharged from the outlet 42, which can dissipate heat for the carrier.

[0062] As a further technical solution of the present invention, there are at least two groups of cavities 131 on the pump main structure 1, and at least two groups of the cavities 131 are distributed in a linear array on the second structural layer 13. Each group of the cavities 131 has a first channel 132b and a second channel 132a. There is a piezoelectric excitation unit 11 above each group of cavities 131. Each group of cavities 131 provides a vibration space for the corresponding diaphragm, and at least two groups of the cavities 131 are connected.

[0063] Example 6

[0064] See also Figure 15-16 As shown, two groups of cavities 131 are connected in series. The first channel 132b of one group of cavities 131 is connected to the second channel 132a of the other group of cavities 131. After entering the second channel 132a of one cavity 131 and being pressurized, the medium flows through the second channel 132b and the first channel 132a into the other cavity 131. After secondary pressurization, it is ejected from the first channel 132b of the other cavity 131 to dissipate heat from the carrier. The two groups of cavities 131 are connected in series, allowing the air to be secondary pressurized before being ejected, improving the heat dissipation effect. At the same time, the MEMS process allows the two pump main structures to be integrally formed.

[0065] Example 7

[0066] See also Figure 17 Based on the preferred embodiment of Example 6, the embodiment of the present invention proposes a piezoelectric micropump, in which multiple cavities 131 are connected in series, and the first channel 123b of one cavity 131 in two adjacent groups of cavities 131 is connected to the second channel 132a of the other cavity 131. The medium is ejected after multiple pressurizations, further improving the heat dissipation effect, and multiple pump main body structures are all integrally formed through MEMS technology.

[0067] Example 8

[0068] See also Figure 18-20Based on the preferred embodiment of Example 6, the embodiment of the present invention proposes a piezoelectric micropump, wherein two groups of cavities 131 are provided, and the two groups of cavities 131 are connected in parallel. Specifically, a first flow channel 21 and a second flow channel 31 are opened on the second structural layer 13, and the first channels 132b of the two groups of cavities 131 are both connected to the second flow channel 31, and the second channels 132a of the two groups of cavities 131 are both connected to the first flow channel 21. A medium inlet 21c connected to the first flow channel 21 is opened on the second structural layer 13, and a medium outlet 31c connected to the second flow channel 31 is opened on the second structural layer 13. The medium enters the first flow channel 21 through the medium inlet 21c, and then enters the two groups of cavities 131 through the two second channels 132b connected to the first flow channel 21. Then, the medium enters the second flow channel 31 through the first channel 132a connected to each cavity 131, and then the medium is discharged through the medium outlet 31c.

[0069] Specifically, the portion of the first flow channel 21 that connects to one second channel 132a is the first medium inlet 21a, the portion of the first flow channel 21 that connects to the other second channel 132a is the second medium inlet 21b, the portion of the second flow channel 31 that connects to one first channel 132b is the first medium outlet 31a, and the portion of the second flow channel 31 that connects to the other first channel 132b is the second medium outlet 31b. The medium enters the first flow channel 21 through the medium inlet 21c, then enters the two second channels 132b through the first and second medium inlets 21a and 21b, and then enters the two sets of cavities 131. After being pressurized, the medium enters the second flow channel 31 through the first and second medium outlets 31a and 31b, and is discharged through the medium outlet 31c. The two sets of cavities are connected in parallel, increasing the amount of air per unit time and improving heat dissipation. Furthermore, the MEMS process allows the pump body structure to be integrally formed.

[0070] Embodiment 9

[0071] See also Figure 21 Based on a preferred embodiment of Example 8, the embodiment of the present invention proposes a piezoelectric micropump, which can connect multiple cavities 131 in parallel, further increase the amount of air per unit time, further improve the heat dissipation effect, and multiple pump main body structures, front cavities and rear cavities are integrally formed.

[0072] The following is based on Figure 22-Figure 28 The specific process of the piezoelectric micropump preparation process in the embodiment of the present invention is described.

[0073] Example 10

[0074] See also Figure 22-24 This embodiment proposes a preparation process for preparing the piezoelectric micropump proposed in Example 1, comprising the following steps:

[0075] S1, wafer preparation. Prepare an SOI wafer, which includes bottom silicon, buried oxide layer, and top silicon (the second structure layer 13 (bottom silicon), first growth layer 121 (buried oxide layer), and first structure layer 12 (top silicon) in Example 1) stacked in sequence.

[0076] S2, grow the piezoelectric layer (i.e., the piezoelectric excitation unit in Example 1). S2-1, sputter-grow a PZT lower electrode 111 on the second structural layer 12 (top silicon); S2-2, sputter-grow a PZT thin film 112 on the PZT lower electrode 111; S2-3, sputter-grow a PZT upper electrode 113 on the PZT thin film 112; S2-4, sequentially pattern the PZT upper electrode 113, PZT thin film 112, and PZT lower electrode 111.

[0077] S3, patterning the bottom silicon. S3-1, dry-etching the bottom silicon to form the first channel 132b and part of the cavity 131 in Example 1; S3-2, dry-etching the bottom silicon to form the cavity 131 in Example 1.

[0078] S4, bottom packaging: The third structure layer 14 in Example 1 is bonded to the bottom of the second structure layer 13 through a bonding process, and a second growth layer 141 is formed during the bonding process.

[0079] Example 11

[0080] See also Figures 25-28 This embodiment proposes a preparation process for preparing the piezoelectric micropump proposed in Example 3, comprising the following steps:

[0081] S1, wafer preparation: Prepare an SOI wafer, the SOI wafer including bottom silicon, buried oxide layer and top silicon (ie, the second structure layer 13, the first growth layer 121 and the first structure layer 12 in Example 3) stacked in sequence.

[0082] S2, grow the piezoelectric layer (i.e., the piezoelectric excitation unit in Example 3). S2-1, sputter-grow a PZT lower electrode 111 on the second structural layer; S2-2, sputter-grow a PZT thin film 112 on the PZT lower electrode 111; S2-3, sputter-grow a PZT upper electrode 113 on the PZT thin film 112; S2-4, sequentially pattern the PZT upper electrode 113, PZT thin film 112, and PZT lower electrode 111.

[0083] S3, patterning the bottom silicon. S3-1, dry-etching the bottom silicon to form the first channel 132b, a portion of the cavity 131, and the second channel 132a in Example 3. S3-2, wet-etching the bottom silicon to form a portion of the cavity 131 in Example 3. S3, dry-etching the bottom silicon to form the cavity 131 in Example 3.

[0084] S4, bottom packaging: The third structure layer 14 in Example 3 is bonded to the bottom of the second structure layer 13 through a bonding process, and a second growth layer 141 is formed during the bonding process.

[0085] Example 12

[0086] This embodiment proposes a preparation process for preparing Example 6 based on the preparation process proposed in Example 11.

[0087] In step S3, the bottom silicon is patterned. Step S3-1 involves dry etching the bottom silicon to form the first channel 1A-132b, a portion of the cavity 1A-132, the second channel 1B-132a, the first channel 1B-132b, the portion of the cavity 1B-131, and the second channel 1B-132a in Example 6. Step S3-2 involves wet etching the bottom silicon to form the portion of the cavity 131 in Example 6. Step S3 involves dry etching the bottom silicon to form the cavity 131 in Example 6.

[0088] Example 13

[0089] This embodiment proposes a preparation process for preparing Example 8 based on the preparation process proposed in Example 11.

[0090] In step S3, the bottom silicon is patterned. Step S3-1 involves dry etching the bottom silicon to form the first channel 1A-132b, a portion of the cavity 1A-132, the second channel 1B-132a, the first channel 1B-132b, a portion of the cavity 1B-131, the second channel 1B-132a, the first flow channel 21, and the second flow channel 31 in Example 8. Step S3-2 involves wet etching the bottom silicon to form a portion of the cavity 131 in Example 8. Step S3 involves dry etching the bottom silicon to form the cavity 131 in Example 8.

[0091] The preparation process of the piezoelectric micropump proposed in the embodiment of the present invention utilizes the MEMS process to integrally form multiple pump main structures, eliminating the need to assemble multiple single pump main structures, saving steps, and at the same time, increasing device consistency and miniaturization.

[0092] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A piezoelectric micropump based on MEMS technology, comprising a pump main structure (1), characterized in that: The pump main body structure (1) comprises a third structural layer (14), a second structural layer (13), a first structural layer (12), and a piezoelectric excitation unit (11) which are sequentially stacked. The piezoelectric excitation unit (11) comprises a bottom electrode (111), a piezoelectric film (112), and a top electrode (113) which are sequentially stacked on the first structural layer (12). A cavity (131) is provided on the second structural layer (13); the first structural layer (12) within the longitudinal projection area of ​​the cavity (131) close to the port of the first structural layer (12) is a diaphragm; the cavity (131) provides a vibration space for the diaphragm; and a first channel (132b) communicating with the cavity (131) is provided on the second structural layer (13).

2. The piezoelectric micropump based on MEMS technology according to claim 1, characterized in that: The first structural layer (12) is connected to the second structural layer (13) via a first growth layer (121); and / or The third structural layer (14) is connected to the second structural layer (13) via the second growth layer (141); The first growth layer (121) and / or the second growth layer (141) is a silicon oxide structure layer.

3. The piezoelectric micropump based on MEMS technology according to claim 2, characterized in that: The third structural layer (14), the second structural layer (13) and the first structural layer (12) are all silicon structural layers.

4. The piezoelectric micropump based on MEMS technology according to claim 1, characterized in that: The cavity (131) is a truncated cone structure, and the port area of ​​the cavity (131) close to the first structural layer (12) is smaller than the port area of ​​the cavity (131) close to the third structural layer (14).

5. The piezoelectric micropump based on MEMS technology according to claim 1, characterized in that: When the medium flowing through the cavity (131) is gas, it also includes a packaging structure (4), the packaging structure (4) is used to package the pump main structure (1), the top of the packaging structure (4) is provided with an air inlet (41), and the side wall of the packaging structure (4) is provided with an air outlet (42) at a position corresponding to the first channel (132b).

6. The piezoelectric micropump based on MEMS technology according to claim 1, characterized in that: A second channel (132a) communicating with the cavity (131) is provided on a side wall of the bottom of the second structural layer (13) opposite to the first channel (132b).

7. The piezoelectric micropump based on MEMS technology according to claim 6, characterized in that: The cross-sectional area of ​​the first channel (132b) gradually decreases from the side away from the cavity (131) to the side close to the cavity (131); and / or The cross-sectional area of ​​the second channel (132a) gradually increases from the side away from the cavity (131) to the side close to the cavity (131).

8. The piezoelectric micropump based on MEMS technology according to claim 1, characterized in that: The specifications of the second channel (132a) are greater than those of the first channel (132b), and the specifications include one or more of width, height, and volume.

9. The piezoelectric micropump based on MEMS technology according to claim 1, characterized in that: When the medium flowing through the cavity (131) is gas, the piezoelectric micropump further comprises a packaging structure (4), wherein the packaging structure (4) is provided with an air outlet (42) at a position corresponding to the first channel (132b), and an air inlet (41) is provided at a position on the top of the packaging structure (4) close to the second channel (132a).

10. The MEMS-based piezoelectric micropump according to any one of claims 1 to 9, characterized in that: At least two groups of cavities (131) are provided, and at least two groups of the cavities (131) are distributed on the second structural layer (13) in a linear array, each group of the cavities (131) has a first channel (132b) and a second channel (132a), and a piezoelectric excitation unit (11) is provided above each group of cavities (131). Each group of cavities (131) provides a vibration space for a corresponding diaphragm, and at least two groups of the cavities (131) are connected.

11. The MEMS-based piezoelectric micropump according to claim 10, characterized in that: At least two groups of cavities (131) are connected in series, the first channel (123b) of one cavity (131) in two adjacent groups of cavities (131) is connected to the second channel (132a) of the other cavity (131), and the medium is ejected after multiple pressurizations.

12. The piezoelectric micropump based on MEMS technology according to claim 10, characterized in that: At least two groups of the cavities (131) are connected in parallel, a first flow channel (21) and a second flow channel (31) are provided on the second structural layer (13), the first channels (132b) of at least two groups of the cavities (131) are communicated with the second flow channel (31), and the second channels (132a) of at least two groups of the cavities (131) are communicated with the first flow channel (21), a medium inlet (21c) communicated with the first flow channel (21) is provided on the second structural layer (13), and a medium outlet (31c) communicated with the second flow channel (31) is provided on the second structural layer (13).

13. A method for preparing a piezoelectric micropump based on MEMS technology, characterized in that: The method for preparing the piezoelectric micropump according to any one of claims 1 to 12 comprises the following steps: S1, preparing an SOI wafer, the SOI wafer comprising a bottom silicon layer, a buried oxide layer and a top silicon layer stacked in sequence, the bottom silicon layer being the second structural layer (13) and the top silicon layer being the first structural layer (12); S2, growing a piezoelectric excitation unit (11) on the first structural layer (12); S3, patterning the bottom silicon to form a cavity (131) and a first channel (132b); S4, bottom packaging: making the third structural layer sealing cavity (131) away from one end of the first structural layer (12).

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