Piezoelectric micropump based on MEMS chip and preparation process

Abstract

The invention discloses a piezoelectric micropump based on an MEMS chip and a preparation technology, and relates to the technical field of piezoelectric micropump semiconductor technologies, the piezoelectric micropump comprises an SOI substrate and a piezoelectric layer, the SOI substrate comprises bottom silicon, a buried oxide layer and top silicon, the bottom silicon is provided with a back cavity, the piezoelectric layer is arranged on the surface, away from the bottom silicon, of a vibrating diaphragm, the surface, close to the piezoelectric layer, of the top silicon is provided with a jet flow cavity in a sealed mode, and the jet flow cavity is communicated with the buried oxide layer. A jet flow hole penetrates through the buried oxide layer, the top silicon and the piezoelectric layer, an air outlet plate is arranged on the surface, away from the top silicon, of the bottom silicon in a sealed mode, the air outlet plate and the back cavity form an airflow cavity, and air outlet holes are formed in the air outlet plate in a penetrating mode. And the airflow cavity is constructed by using the back cavity of the piezoelectric micropump, so that the airflow cavity does not need to be formed by additional packaging, the piezoelectric micropump is miniaturized, and the application range of equipment is expanded.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric micropump semiconductor process technology, and in particular to a piezoelectric micropump based on a MEMS chip and its fabrication process. Background Technology

[0002] The jet stroke refers to the effective displacement distance of the fluid ejected by the diaphragm during a single working cycle of a piezoelectric micropump when the fluid is propelled by the diaphragm to form a jet. It reflects the fluid output of the piezoelectric micropump in a single operation and is a key parameter affecting flow rate, accuracy, and response speed. A large jet stroke is suitable for high-flow-rate, high-viscosity media applications, such as industrial spraying and chemical processes; a small jet stroke is suitable for high-precision, high-frequency response applications, such as biomedicine and microelectronics manufacturing.

[0003] In piezoelectric micropumps, a jet cavity needs to be constructed to meet the jet stroke, and an airflow cavity also needs to be constructed to achieve air interaction. In existing technologies, traditional piezoelectric micropumps are divided into two types: forward-firing and backward-firing. In forward-firing, a jet cavity needs to be formed by encapsulating a jet plate of a certain height, and an airflow cavity needs to be formed by encapsulating an air outlet plate of a certain height. This encapsulation process, creating two types of jet and airflow cavities of a certain height, increases the encapsulation size, reduces the device's adaptability, and runs counter to the trend of miniaturization (e.g., Figure 1 (As shown). During back-facing emission, a jet cavity needs to be formed using a jet plate and the back cavity of the underlying silicon. However, the thickness of the underlying silicon in standardized SOI substrates is typically 400 micrometers, resulting in a fixed jet stroke. Reducing the jet stroke requires adding a process to thin the underlying silicon, complicating the process and increasing the risk of fragmentation (e.g., ...). Figure 2 (As shown in a); to increase the jet stroke, a jetting plate of a certain height needs to be packaged on the back of the bottom silicon to form a jetting cavity, and then an outlet plate of a certain height needs to be packaged externally to form an airflow cavity. This complex process also leads to an increase in size (e.g. Figure 2 (as shown in b).

[0004] For the reasons mentioned above, this invention proposes a piezoelectric micropump based on an SOI substrate and its fabrication method to solve the aforementioned problems. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a piezoelectric micropump based on a MEMS chip and its fabrication process, thereby solving the problems faced by existing traditional piezoelectric micropumps during launch, such as increased packaging size, reduced equipment adaptability, complex processes, and increased risk of fragmentation.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A piezoelectric micropump based on a MEMS chip and its fabrication process, comprising an SOI substrate, wherein a back cavity is formed on the back side of the substrate and a piezoelectric layer corresponding to the back cavity is formed on the front side of the substrate;

[0008] A sealed jet cavity is provided on the front side of the substrate, and an airflow cavity is formed based on the back cavity. A jet hole is connected between the jet cavity and the airflow cavity, and an air outlet is provided in the airflow cavity.

[0009] As a further embodiment of the present invention, the piezoelectric layer includes a bottom electrode, a piezoelectric thin film layer and a top electrode stacked sequentially.

[0010] As a further embodiment of the present invention, the substrate includes a bottom silicon layer, a buried oxide layer and a top silicon layer stacked sequentially, wherein the bottom silicon layer has through holes to form the back cavity.

[0011] As a further embodiment of the present invention, the jet hole is located at the center of the diaphragm, and the centerline of the jet hole coincides with the centerline of the air outlet.

[0012] As a further embodiment of the present invention, the bottom silicon sidewall is provided with an air intake channel communicating with the back cavity.

[0013] As a further aspect of the present invention:

[0014] The top silicon surface extends beyond the piezoelectric layer region and is connected to a sealed jet plate to form a jet cavity;

[0015] An air outlet plate is provided on the bottom surface of the silicon substrate, and the air outlet plate and the back cavity form the airflow cavity.

[0016] A fabrication process for a piezoelectric micropump based on a MEMS chip includes the following steps:

[0017] S1, Prepare an SOI substrate. The SOI substrate includes a bottom silicon layer, a buried oxide layer, and a top silicon layer stacked sequentially.

[0018] S2, a piezoelectric layer is grown on the top silicon;

[0019] S3, patterned bottom silicon, forming a back cavity;

[0020] S4, dry etching of the piezoelectric layer and substrate to form jet holes;

[0021] S5, dry etching of thin silicon wafer to form vent holes, bonding thin silicon wafer to the surface of bottom silicon away from the piezoelectric layer;

[0022] S6, dry etching is used to form a jet cavity on the thick silicon wafer, bonding the thick silicon wafer to the surface of the top silicon wafer away from the bottom silicon wafer.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention utilizes the back cavity of the bottom silicon itself and the air outlet plate to form an airflow cavity, eliminating the need for additional encapsulation of a separate airflow cavity structure. This significantly reduces the overall size of the piezoelectric micropump, conforming to the trend of miniaturization. This design allows the device to adapt to smaller installation spaces, and it has stronger adaptability, especially in fields such as integrated electronic devices and micro medical devices.

[0025] 2. This invention forms a jet cavity by sealing the top silicon surface, and the jet stroke is directly determined by the internal height of the jet plate, eliminating the need for thinning or additional processing of the bottom silicon of the SOI substrate. This allows the jet stroke to be flexibly adjusted according to requirements, satisfying both high-flow scenarios such as industrial spraying and high-precision scenarios such as biomedicine, significantly broadening the application range of the equipment.

[0026] 3. Compared to traditional back-emitting piezoelectric micropumps, this invention eliminates the need to reduce the jet stroke by thinning the silicon substrate, and also eliminates the need for additional jetting plates on the back of the silicon substrate to increase the jet stroke. It employs semiconductor processes such as dry etching and bonding, resulting in a simpler and more controllable process, facilitating standardized production and improving efficiency. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a traditional piezoelectric micropump emitting power in the forward direction.

[0028] Figure 2 This is a schematic diagram of a traditional piezoelectric micropump emitting light from the back.

[0029] Figure 3 This is a schematic diagram of the structure of the piezoelectric micropump based on an SOI substrate proposed in Embodiment 1 of the present invention;

[0030] Figure 4 for Figure 3 Exploded view of the structure;

[0031] Figure 5 for Figure 3 Schematic diagram of the middle jet plate;

[0032] Figure 6 for Figure 3 A schematic diagram of the structure of the medium-voltage electrical layer.

[0033] 1. Vent plate; 11. Vent hole;

[0034] 2. Substrate; 21. Bottom silicon; 211. Back cavity / gas flow cavity; 212. Inlet channel; 22. Buried oxide layer; 23. Top silicon;

[0035] 3. Piezoelectric layer; 31. Bottom electrode; 32. Piezoelectric thin film layer; 33. Top electrode;

[0036] 4. Jet plate; 41. Jet cavity;

[0037] a. Jet orifice. Detailed Implementation

[0038] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0039] Traditional piezoelectric micropumps are relatively large, making it difficult to meet the miniaturization and integration demands of current electronic devices. In applications with extremely demanding space requirements, such as wearable devices and implantable medical devices, large-volume piezoelectric micropumps are simply unsuitable. Furthermore, the flow and pressure output performance of existing piezoelectric micropumps is not stable enough to provide stable and reliable power support for the system.

[0040] To address the aforementioned issues, this invention discloses a piezoelectric micropump based on an SOI substrate and its fabrication process.

[0041] Example 1:

[0042] Please see Figures 3 to 6 The piezoelectric micropump based on SOI substrate 2 proposed in this embodiment of the invention includes SOI substrate 2 and piezoelectric layer 3.

[0043] The SOI substrate 2 includes a bottom silicon 21, a buried oxide layer 22 and a top silicon 23 stacked sequentially, and a piezoelectric layer 3 is disposed on the surface of the top silicon 23.

[0044] The bottom silicon 21 has a through hole, which forms a back cavity 211. The back cavity 211 provides space for the diaphragm to vibrate, and the piezoelectric layer 3 provides the force to drive the diaphragm to vibrate. When a suitable voltage is applied to the piezoelectric layer 3, the piezoelectric layer 3 will deform due to the piezoelectric effect. This deformation will be transmitted to the diaphragm connected to it, causing the diaphragm to vibrate.

[0045] Furthermore, such as Figure 3 The top surface region of the top silicon 23 is larger than the region of the piezoelectric layer 3. The area of ​​the top surface of the top silicon 23 that extends beyond the piezoelectric layer 3 is sealed with a jet plate 4, which together form a jet cavity 41. Figure 5 As shown, the jet cavity 41 is a square or cylindrical cavity, and the jet stroke is determined by the internal height of the jet plate 4. Figure 4 As shown, an air outlet plate 1 is provided on the bottom surface of the bottom silicon 21, and the air outlet plate 1 and the back cavity 211 form an airflow cavity 211.

[0046] Through holes are formed in the buried oxide layer 22, top silicon 23 and piezoelectric layer 3 to form jet holes a. The center line of the through hole a coincides with the center line of the diaphragm. The jet hole a connects the jet cavity 41 and the air flow cavity 211. At the center of the air outlet plate 1, through holes are formed to form air outlet holes 11.

[0047] The vent 11 is connected to the back cavity / airflow cavity 211. When the diaphragm vibrates under the drive of the piezoelectric layer 3, it causes pressure changes in the jet cavity 41 and the airflow cavity 211. When the diaphragm vibrates upward, the pressure in the jet cavity 41 decreases, and external gas is drawn into the jet cavity 41 through the jet hole a; while when the diaphragm vibrates downward, the pressure in the jet cavity 41 increases, and gas enters the airflow cavity 211 through the jet hole a, and is then discharged through the vent 11. This periodic pressure change enables directional gas flow, allowing the entire piezoelectric micropump based on the SOI substrate 2 to perform the function of gas delivery.

[0048] Furthermore, the centerline of jet hole a coincides with the centerline of vent hole 11. Due to the centrosymmetric structure of SOI substrate 2 and piezoelectric layer 3, the diaphragm experiences relatively uniform force in all directions during vibration, ensuring the stability and consistency of diaphragm vibration, thereby improving the overall efficiency and reliability of the piezoelectric micropump. Moreover, the centrosymmetric design also facilitates the realization of the manufacturing process, reducing manufacturing difficulty and cost.

[0049] Preferably, such as Figure 4 As shown, an air inlet channel 212 communicating with the back cavity 211 is formed on the side wall of the bottom silicon 21. By setting the air inlet channel 212, external gas can enter the back cavity / airflow cavity 211 more smoothly, thereby providing a sufficient gas source for subsequent gas to enter the jet cavity 41. The design of the air inlet channel 212 optimizes the gas inflow path and reduces the resistance and loss of gas during the entry process. At the same time, the reasonable setting of the size and shape of the air inlet channel 212 can precisely control the gas flow rate and velocity entering the back cavity 211 to meet the needs of the piezoelectric micropump under different operating conditions.

[0050] Furthermore, such as Figure 6 As shown, the piezoelectric layer 3 includes a bottom electrode 31, a piezoelectric thin film layer 32 and a top electrode 33 stacked sequentially. This stacked structure enables the piezoelectric layer 3 to generate an effective piezoelectric effect under the action of an electric field.

[0051] The piezoelectric micropump based on SOI substrate 2 proposed in this embodiment encapsulates a jet plate 4 on the front side of the piezoelectric layer 3 to form a jet cavity 41 with the required jet stroke. Backward emission is achieved by creating a through-hole, and the back cavity 211 of the SOI substrate 2 is encapsulated as a gas flow cavity 211. Compared to... Figure 1The traditional piezoelectric micropump shown does not require a separate encapsulated airflow chamber 211, thus reducing the size of the piezoelectric micropump and allowing it to adapt to different installation scenarios. Compared to... Figure 2 The conventional piezoelectric micropump shown has a jet stroke determined by the height of the jet plate 4. When a small jet stroke is required, it replaces the method of thinning the bottom silicon 21, which simplifies the process and reduces the risk of breakage. When a large jet stroke is required, it replaces the method of encapsulating a jet cavity 41 and a gas flow cavity 211 of a certain height on the back of the bottom silicon 21. This simplifies the process and reduces the size, realizing the development prospect of miniaturization of piezoelectric micropumps.

[0052] Example 2:

[0053] Based on the piezoelectric micropump of Example 1, this example proposes a preparation method, including the following steps:

[0054] S1. Prepare SOI substrate 2. SOI substrate 2 includes bottom silicon 21, buried oxide layer 22 and top silicon 23 stacked sequentially.

[0055] The prepared SOI substrate 2 is cleaned and dried to remove surface impurities and moisture, ensuring the stability of subsequent processes.

[0056] S2, a piezoelectric layer 3 is grown on the top silicon 23. The piezoelectric layer 3 includes a bottom electrode 31, a piezoelectric thin film layer 32 and a top electrode 33. The piezoelectric layer 3 can be grown by magnetron sputtering. The magnetron sputtering process has many advantages, as it can precisely control the thickness and compositional uniformity of the piezoelectric layer 3.

[0057] First, a bottom electrode 31 is sputtered using a suitable metal material, such as platinum. By adjusting sputtering parameters, such as sputtering power, sputtering time, and gas flow rate, the bottom electrode 31 is uniformly deposited on the surface of the top silicon 23. Next, a piezoelectric thin film layer 32 is sputtered. The material for the piezoelectric thin film layer 32 is typically a material with good piezoelectric properties, such as lead zirconate titanate (PZT). Finally, a top electrode 33 is sputtered, again using a suitable metal material, such as gold, to complete the growth of the piezoelectric layer 3.

[0058] S3, patterned bottom silicon 21, forming back cavity 211.

[0059] The back cavity 211 is fabricated on the silicon substrate 21 using processes such as ion etching. The required depth and shape of the back cavity 211 are etched onto the silicon substrate 21, and this back cavity 211 will be used as a gas flow chamber 211. During etching, care must be taken to maintain the perpendicularity and surface flatness of the back cavity 211 to improve the performance of the micropump. Simultaneously, the etched surface of the silicon substrate 21 is cleaned and passivated to enhance its corrosion resistance and stability.

[0060] S4. Dry etching of piezoelectric layer 3 and substrate 2 to form jet hole a. Determine a suitable etching gas, such as fluorine-based gas. During the etching process, the etching rate must be strictly controlled, which can be achieved by adjusting parameters such as gas flow rate and radio frequency power to ensure the uniformity and accuracy of etching.

[0061] The size and shape of the jet orifice a need to be determined based on the specific design requirements of the piezoelectric micropump. During the etching process, the depth and diameter of the jet orifice a must be monitored in real time to ensure they meet design standards.

[0062] S5, dry etching of thin silicon wafer to form vent holes 11, bonding thin silicon wafer to the surface of bottom silicon 21 away from piezoelectric layer 3.

[0063] First, prepare a thin silicon wafer as the vent plate 1, and use a dry etching process to form vent holes 11 on it.

[0064] Before etching, the thin silicon wafer needs to be cleaned to remove surface impurities and contaminants to ensure effective etching. Then, appropriate etching parameters need to be determined, including the type and flow rate of the etching gas, and the etching time. A fluorine-based gas similar to that used in the etching jet a can be selected, and parameters such as the gas flow rate can be adjusted according to the size and precision requirements of the outlet hole 11.

[0065] After etching, the thin silicon wafer is cleaned and inspected to remove residual reactants and impurities from the etching process. The treated thin silicon wafer is then bonded to the surface of the base silicon 21 furthest from the piezoelectric layer 3. The bonding process requires precise control of temperature, pressure, and other conditions to ensure a strong, sealed connection between the thin silicon wafer and the base silicon 21. Methods such as anodic bonding can be used. During the bonding process, it is crucial to maintain the alignment accuracy between the thin silicon wafer and the base silicon 21 to prevent misalignment of structures such as the vent 11 and the back cavity 211, which could affect the normal operation of the piezoelectric micropump.

[0066] S6, dry etching is used to form a jet cavity 41 on the thick silicon wafer, and the thick silicon wafer is bonded to the surface of the top silicon 23 away from the bottom silicon 21.

[0067] First, a thick silicon wafer is prepared as the jet plate 4, and its surface is treated to remove the oxide layer and impurities, making the silicon wafer surface clean and flat. Then, using dry etching techniques such as plasma etching, the thick silicon wafer is etched according to the pattern of the photoresist mask to form a jet cavity 41 with specific size and shape.

[0068] Then, the processed thick silicon wafer is bonded to the surface of the top silicon 23 away from the bottom silicon 21. During bonding, temperature, pressure and alignment accuracy need to be precisely controlled. A suitable bonding method is used to form a stable and reliable connection between the thick silicon wafer and the top silicon 23, avoiding gaps or misalignments, so as to ensure the overall performance and working stability of the piezoelectric micropump.

[0069] Furthermore, before bonding the thick silicon wafer to the surface of the top silicon 23 away from the bottom silicon 21, an air intake channel 212 communicating with the back cavity 211 can be opened on the side of the bottom silicon 21. The air intake channel 212 can be opened using a combination of photolithography and wet etching.

[0070] First, photoresist is coated on the side of the silicon substrate 21. The designed air intake channel 212 pattern is then transferred onto the photoresist using photolithography, forming a precise mask. Next, a suitable wet etchant is used to etch the silicon substrate 21 according to the pattern of the photoresist mask, thereby forming the air intake channel 212 that communicates with the back cavity 211. Through these process steps, a high-performance air intake channel 212 communicating with the back cavity 211 can be successfully formed on the side of the silicon substrate 21, providing a stable airflow input for the normal operation of the piezoelectric micropump.

[0071] This embodiment uses the above-described fabrication process to fabricate a piezoelectric micropump for the MEMS chip. This eliminates the need for a separate encapsulation of the airflow cavity 211, reducing the size of the piezoelectric micropump and allowing it to adapt to different installation scenarios. The jet stroke is determined by the height of the jet plate 4, which simplifies the process and reduces the size, realizing the development prospect of miniaturization of piezoelectric micropumps.

[0072] Meanwhile, the fabrication process precisely controls the temperature, pressure, and alignment accuracy during the bonding of the thick silicon wafer, resulting in a stable and reliable connection between the thick silicon wafer and the top silicon 23. This avoids gaps or misalignments, which greatly improves the overall performance and operational stability of the piezoelectric micropump, effectively reduces the failure rate caused by unstable connections, and extends the service life of the piezoelectric micropump.

[0073] Using this fabrication process, a high-performance air inlet channel 212, communicating with the back cavity 211, was successfully created on the side of the bottom silicon 21, providing a stable airflow input for the piezoelectric micropump. This allows the piezoelectric micropump to deliver gas more efficiently during operation, improving its working efficiency. Furthermore, the stable airflow input helps ensure the stability and accuracy of the piezoelectric micropump's output, enabling it to better meet the needs of practical applications.

[0074] Furthermore, the fabrication process in this embodiment exhibits excellent repeatability and controllability. In actual production, production can be carried out relatively stably according to predetermined process steps and parameters, ensuring that each fabricated piezoelectric micropump possesses similar performance and quality. This facilitates large-scale production and industrial application, effectively reducing production costs and improving production efficiency.

[0075] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0076] It should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and "set" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0077] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

Claims

1. A piezoelectric micropump based on a MEMS chip, comprising an SOI substrate, wherein a back cavity is formed on the back side of the substrate, and a piezoelectric layer corresponding to the back cavity is disposed on the front side of the substrate, characterized in that: The substrate has a sealed jet cavity on the front side and an airflow cavity is formed based on the back cavity. A jet hole is connected between the jet cavity and the airflow cavity, and an air outlet is provided in the airflow cavity.

2. The piezoelectric micropump based on a MEMS chip according to claim 1, characterized in that, The substrate comprises a bottom silicon layer, a buried oxide layer, and a top silicon layer stacked sequentially, wherein the bottom silicon layer has through holes to form the back cavity.

3. The piezoelectric micropump based on a MEMS chip according to claim 1, characterized in that, The jet hole is located at the center of the diaphragm, and the centerline of the jet hole coincides with the centerline of the air outlet.

4. The piezoelectric micropump based on a MEMS chip according to claim 2, characterized in that, The bottom silicon sidewall has an air intake channel that communicates with the back cavity.

5. The piezoelectric micropump based on a MEMS chip according to claim 2, characterized in that: The top silicon surface extends beyond the piezoelectric layer region and is connected to a sealed jet plate to form a jet cavity; An air outlet plate is provided on the bottom surface of the silicon substrate, and the air outlet plate and the back cavity form the airflow cavity.

6. The piezoelectric micropump based on a MEMS chip according to claim 1, characterized in that, The piezoelectric layer includes a bottom electrode, a piezoelectric thin film layer, and a top electrode stacked sequentially.

7. A fabrication process for fabricating the piezoelectric micropump based on a MEMS chip as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1, Prepare an SOI substrate. The SOI substrate includes a bottom silicon layer, a buried oxide layer, and a top silicon layer stacked sequentially. S2, a piezoelectric layer is grown on the top silicon; S3, patterned bottom silicon, forming a back cavity; S4, dry etching of the piezoelectric layer and substrate to form jet holes; S5, dry etching of thin silicon wafer to form vent holes, bonding thin silicon wafer to the surface of bottom silicon away from the piezoelectric layer; S6, dry etching is used to form a jet cavity on the thick silicon wafer, bonding the thick silicon wafer to the surface of the top silicon wafer away from the bottom silicon wafer.

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