CN118142831A - An integrated waveguide piezoelectric micromechanical ultrasonic transducer and a method for manufacturing the same - Google Patents

Abstract

The present invention provides an integrated waveguide piezoelectric micromechanical ultrasonic transducer and a preparation method thereof, belonging to the technical field of micromechanical ultrasonic transducers. It includes a waveguide section and a PMUT chip, the PMUT chip includes a substrate, an AlN seed layer, a bottom electrode layer, an AlN piezoelectric layer, a top electrode layer, an insulating layer and a lead layer stacked from bottom to top, the substrate is an SOI substrate, the SOI substrate includes a bottom silicon layer, a buried oxide layer and a structural silicon layer stacked from bottom to top, the AlN seed layer is located on the surface of the structural silicon layer; the waveguide section is a cavity, the cavity is obtained by ion etching the bottom silicon layer, and the depth of the cavity is equal to the thickness of the bottom silicon layer. In the present invention, the existence of the waveguide section can guide sound waves, concentrate sound wave energy, better transmit sound energy and realize system miniaturization, while improving the emission performance.

Description

An integrated waveguide piezoelectric micromechanical ultrasonic transducer and a method for manufacturing the same

Technical Field

The present invention relates to the technical field of micromechanical ultrasonic transducers, and in particular to an integrated waveguide piezoelectric micromechanical ultrasonic transducer and a preparation method thereof.

Background technique

Micro-electromechanical systems (MEMS) technology has developed rapidly due to the valuable advantages of microstructures such as small size, low unit cost, high sensitivity, low power consumption, and fast dynamic response. Micromachined ultrasonic transducers (MUTs) are a potential solution to overcome the shortcomings of traditional body transducers. MUTs have two transduction mechanisms: capacitive micromachined ultrasonic transducers (CMUTs) and piezoelectric micromachined ultrasonic transducers (PMUTs). Compared with CMUTs, PMUTs do not require polarization voltages, which reduces the circuit complexity of catheter-based ultrasound applications, and do not require small capacitor gaps, which reduces manufacturing complexity. The thin film piezoelectric materials of PMUTs are mostly lead zirconate titanate (PZT) and aluminum nitride (AlN). PZT has a higher piezoelectric constant, but is incompatible with complementary metal oxide semiconductors (CMOS) and requires a manufacturing temperature of up to 800°C. AlN is lead-free, has a low deposition temperature (<400°C), and is fully compatible with CMOS manufacturing processes suitable for mass production.

The MUT vibrates in a bending vibration mode (d31), and the compliant thin film structure makes the transducer design flexible and compact. However, for applications in direct contact with human tissue, the fine thin film structure of the MUT poses durability issues. Some researchers have tried to solve this problem by coating the MUT array with a polymer layer, but this layer increases the distance between the MUT imager and the imaging surface, which in turn leads to diffraction, scattering, and expansion effects, greatly reducing the imaging contrast and spatial resolution. PDMS (polydimethylsiloxane) is also used as a good acoustic impedance matching medium between the silicon membrane and the finger, but this layer needs to be directly exposed to the environment and is limited by the robustness of the brittle vibrating membrane.

Summary of the invention

In view of this, the object of the present invention is to provide an integrated waveguide piezoelectric micromechanical ultrasonic transducer and a method for manufacturing the same. The waveguide PMUT based on AIN piezoelectric material proposed in the present invention can be connected to a CMOS circuit at the wafer level, and can realize the operation of individually addressing each MUT unit in the array.

In order to achieve the above-mentioned invention object, the present invention provides the following technical solutions:

The present invention provides an integrated waveguide piezoelectric micromechanical ultrasonic transducer, comprising a waveguide section and a PMUT chip, wherein the PMUT chip comprises a substrate, an AlN seed layer, a bottom electrode layer, an AlN piezoelectric layer, a top electrode layer, an insulating layer and a lead layer stacked in sequence from bottom to top, wherein the substrate is an SOI substrate, wherein the SOI substrate comprises a bottom silicon layer, a buried oxide layer and a structural silicon layer stacked in sequence from bottom to top, wherein the AlN seed layer is located on the surface of the structural silicon layer;

The waveguide section is a cavity, and the cavity is obtained by ion etching the bottom silicon layer. The depth of the cavity is equal to the thickness of the bottom silicon layer.

Preferably, the cavity is a cuboid, the bottom surface of the cuboid is a square, and the side length of the square is the side length of the vibrating diaphragm of the integrated waveguide piezoelectric micromechanical ultrasonic transducer.

Preferably, through-hole openings are provided on the surfaces of the bottom electrode layer and the top electrode layer.

Preferably, the bottom electrode layer and the top electrode layer are independently made of Pt, Ti, Al or Mo.

Preferably, the insulating layer is made of silicon dioxide.

The present invention also provides a method for preparing the integrated waveguide piezoelectric micromechanical ultrasonic transducer described in the above technical solution, comprising the following steps:

Depositing on the surface of the SOI substrate to sequentially form an AlN seed layer, a bottom electrode layer precursor, an AlN piezoelectric layer precursor, and a top electrode layer precursor, and then sequentially patterning the top electrode layer precursor, the AlN piezoelectric layer precursor, and the bottom electrode layer precursor to form the bottom electrode layer, the AlN piezoelectric layer, and the top electrode layer;

Deposition is performed on the surfaces of the bottom electrode layer, the AlN piezoelectric layer and the top electrode layer to form the insulating layer;

Deposition is performed on the surface of the insulating layer to form the lead layer, thereby obtaining the PMUT chip;

The bottom silicon layer is ion-etched to form the cavity, thereby obtaining the integrated waveguide piezoelectric micromechanical ultrasonic transducer.

Preferably, the method for patterning the top electrode layer precursor and the bottom electrode layer precursor is fluorine-based plasma etching, and the method for patterning the AlN piezoelectric layer precursor is chlorine-based plasma etching.

Preferably, the area of the patterned top electrode layer precursor is 44.5% of the area of the vibrating diaphragm of the integrated waveguide piezoelectric micromechanical ultrasonic transducer.

Preferably, before forming the insulating layer, the method further comprises performing ion etching on the surfaces of the bottom electrode layer and the top electrode layer to form the through hole openings.

Preferably, the ion etching is deep reactive ion etching.

The present invention provides an integrated waveguide piezoelectric micromechanical ultrasonic transducer, comprising a waveguide section and a PMUT chip, wherein the PMUT chip comprises a substrate, an AlN seed layer, a bottom electrode layer, an AlN piezoelectric layer, a top electrode layer, an insulating layer and a lead layer stacked from bottom to top, wherein the substrate is an SOI substrate, wherein the SOI substrate comprises a bottom silicon layer, a buried oxide layer and a structural silicon layer stacked from bottom to top, wherein the AlN seed layer is located on the surface of the structural silicon layer; wherein the waveguide section is a cavity, wherein the cavity is obtained by ion etching the bottom silicon layer, and wherein the depth of the cavity is equal to the thickness of the bottom silicon layer. The present invention proposes an integrated waveguide piezoelectric micromechanical ultrasonic transducer, wherein the existence of the waveguide section can guide sound waves, concentrate sound wave energy, better transmit sound energy and realize system miniaturization.

Compared with the prior art, the present invention has the following beneficial effects:

The integrated waveguide piezoelectric micromechanical ultrasonic transducer based on AIN piezoelectric material proposed in the present invention can be connected to the CMOS circuit at the wafer level to realize the operation of individually addressing each MUT chip unit in the array. Compared with the complex signal processing required for phased array ultrasonic imaging, the existence of the waveguide section can read out the ultrasonic image pixel by pixel, isolate the pulse echo signal path of each PMUT from its adjacent pulse echo signal path, and at the same time improve the transmission performance of the integrated waveguide piezoelectric micromechanical ultrasonic transducer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the preparation process of the integrated waveguide piezoelectric micromechanical ultrasonic transducer of the present invention;

FIG2 is a cross-sectional view of the integrated waveguide piezoelectric micromechanical ultrasonic transducer manufactured in Example 1 of the present invention when performing ultrasonic imaging;

In FIG3 , (a) is a simulated sound pressure diagram of the PMUT device of the comparative example at 75 ns, (b) is a simulated sound pressure diagram of the PMUT device of the comparative example at 950 ns, (c) is a simulated sound pressure diagram of the PMUT device of Example 1 at 75 ns, and (d) is a simulated sound pressure diagram of the PMUT device of Example 1 at 950 ns;

The electrode layer in Figures 1 and 2 includes a bottom electrode layer and a top electrode layer.

Detailed ways

The present invention provides an integrated waveguide piezoelectric micromechanical ultrasonic transducer, comprising a waveguide section and a PMUT chip, wherein the PMUT chip comprises a substrate, an AlN seed layer, a bottom electrode layer, an AlN piezoelectric layer, a top electrode layer, an insulating layer and a lead layer stacked in sequence from bottom to top, wherein the substrate is an SOI substrate, wherein the SOI substrate comprises a bottom silicon layer, a buried oxide layer and a structural silicon layer stacked in sequence from bottom to top, wherein the AlN seed layer is located on the surface of the structural silicon layer;

The waveguide section is a cavity, and the cavity is obtained by ion etching the bottom silicon layer. The depth of the cavity is equal to the thickness of the bottom silicon layer.

In the present invention, the PMUT chip includes a substrate, an AlN seed layer, a bottom electrode layer, an AlN piezoelectric layer, a top electrode layer, an insulating layer and a lead layer stacked in sequence from bottom to top, the substrate is an SOI substrate, and the SOI substrate includes a bottom silicon layer, a buried oxide layer and a structural silicon layer stacked in sequence from bottom to top, and the AlN seed layer is located on the surface of the structural silicon layer.

In the present invention, the PMUT chip comprises an SOI substrate. In a specific embodiment of the present invention, the SOI substrate is preferably a 4-inch SOI substrate.

In the present invention, the PMUT chip includes an AlN seed layer stacked on the surface of the structural silicon layer.

In the present invention, the thickness of the AlN seed layer is preferably 0.2 μm.

In the present invention, the PMUT chip includes a bottom electrode layer stacked on the surface of the AlN seed layer.

In the present invention, the material of the bottom electrode layer is preferably independently Pt, Ti, Al or Mo.

In the present invention, the thickness of the bottom electrode layer is preferably 0.2 μm.

In the present invention, the PMUT chip includes an AlN piezoelectric layer stacked on the surface of the bottom electrode layer.

In the present invention, the thickness of the AlN piezoelectric layer is preferably 1.5 μm, and the AlN piezoelectric layer preferably adopts a 002 crystal orientation.

In the present invention, the PMUT chip includes a top electrode layer stacked on the surface of the AlN piezoelectric layer.

In the present invention, the material of the top electrode layer is preferably independently Pt, Ti, Al or Mo.

In the present invention, the thickness of the top electrode layer is preferably 0.2 μm.

In the present invention, the area of the top electrode layer is preferably 44.5% of the vibrating diaphragm area of the integrated waveguide piezoelectric micromechanical ultrasonic transducer (the axial diaphragm coverage area rate is 44.5%), and the size is preferably 67% of the side length (relative to the released diaphragm). The size and area of the top electrode layer are limited to the above range because: through finite element analysis, under this condition, good coupling with the basic vibration mode of the diaphragm can be achieved.

In the present invention, the surfaces of the bottom electrode layer and the top electrode layer are preferably provided with through-hole openings, and the through-hole openings are for allowing the lead metal to contact the bottom electrode layer and the top electrode layer, and finally applying voltage to the electrodes.

In the present invention, the PMUT chip includes an insulating layer stacked on the surface of the top electrode layer.

In the present invention, the material of the insulating layer is preferably silicon dioxide.

In the present invention, the thickness of the insulating layer is preferably 300 nm.

In the present invention, the PMUT chip includes a lead layer stacked on the surface of the insulating layer.

In the present invention, the lead layer preferably includes Ti and Au stacked in sequence, the thickness of the Ti is preferably 20 μm, the thickness of the Au is preferably 200 μm, and the Ti is preferably stacked on the surface of the insulating layer.

In the present invention, the integrated waveguide piezoelectric micromechanical ultrasonic transducer includes a waveguide section, the waveguide section is a cavity, the cavity is obtained by ion etching the bottom silicon layer, and the depth of the cavity is equal to the thickness of the bottom silicon layer.

In the present invention, the cavity is preferably a rectangular parallelepiped, the bottom surface of the rectangular parallelepiped is preferably a square, and the side length of the square is preferably the side length of the vibrating diaphragm of the integrated waveguide piezoelectric micromechanical ultrasonic transducer.

The present invention also provides a method for preparing the integrated waveguide piezoelectric micromechanical ultrasonic transducer described in the above technical solution, comprising the following steps:

Depositing on the surface of the SOI substrate to sequentially form an AlN seed layer, a bottom electrode layer precursor, an AlN piezoelectric layer precursor, and a top electrode layer precursor, and then sequentially patterning the top electrode layer precursor, the AlN piezoelectric layer precursor, and the bottom electrode layer precursor to form the bottom electrode layer, the AlN piezoelectric layer, and the top electrode layer;

Deposition is performed on the surface of the bottom electrode layer, the AlN piezoelectric layer and the top electrode layer to form the insulating layer

Deposition is performed on the surface of the insulating layer to form the lead layer, thereby obtaining the PMUT chip;

The bottom silicon layer is ion-etched to form the cavity, thereby obtaining the integrated waveguide piezoelectric micromechanical ultrasonic transducer.

The present invention deposits on the surface of an SOI substrate to sequentially form an AlN seed layer, a bottom electrode layer precursor, an AlN piezoelectric layer precursor and a top electrode layer precursor, and then sequentially pattern the top electrode layer precursor, the AlN piezoelectric layer precursor and the bottom electrode layer precursor to form a bottom electrode layer, an AlN piezoelectric layer and a top electrode layer.

In the present invention, the SOI substrate is preferably subjected to standard RCA cleaning before use. The present invention has no particular limitation on the specific method of the standard RCA cleaning, and a method well known to those skilled in the art may be used.

In the present invention, the deposition is preferably sputtering deposition. The present invention has no special limitation on the specific method of the sputtering deposition, and a method well known to those skilled in the art may be used.

In the present invention, the method for patterning the top electrode layer precursor and the bottom electrode layer precursor is preferably fluorine-based plasma etching, and the method for patterning the AlN piezoelectric layer precursor is preferably chlorine-based plasma etching.

In a specific embodiment of the present invention, patterning the top electrode layer precursor preferably comprises the following steps:

A negative photoresist mask is spin-coated on the surface of the top electrode layer precursor, and developed in a developer MF-319 to obtain a photolithographic pattern. The etching gas _SF6 is converted into plasma to etch the top electrode layer precursor.

In the present invention, the spin coating thickness is preferably 1.25 μm.

In a specific embodiment of the present invention, patterning the AlN piezoelectric layer precursor preferably includes the following steps:

A negative photoresist mask with a thickness of 1.25 μm was spin-coated on the surface of the AlN piezoelectric layer precursor, and a photolithographic pattern was obtained by developing in a developer MF-319. The etching gas Cl ₂ was converted into plasma to etch the AlN piezoelectric layer precursor.

In a specific embodiment of the present invention, patterning the bottom electrode layer precursor preferably comprises the following steps:

A negative photoresist mask is spin-coated on the surface of the bottom electrode layer precursor, and developed in a developer MF-319 to obtain a photolithographic pattern. The etching gas _SF6 is converted into plasma to etch the bottom electrode layer precursor.

In the present invention, the spin coating thickness is preferably 1.25 μm.

In the present invention, the area of the patterned top electrode layer precursor is preferably 44.5% of the area of the vibrating diaphragm of the integrated waveguide piezoelectric micromechanical ultrasonic transducer.

After forming the bottom electrode layer, the AlN piezoelectric layer and the top electrode layer, the present invention performs deposition on the surfaces of the bottom electrode layer, the AlN piezoelectric layer and the top electrode layer to form the insulating layer.

In the present invention, before forming the insulating layer, it is preferred that the method further comprises performing ion etching on the surfaces of the bottom electrode layer and the top electrode layer to form the through hole openings.

In the present invention, the insulating layer is preferably formed by plasma chemical vapor deposition (PCVD).

After forming the insulating layer, the present invention performs deposition on the surface of the insulating layer to form the lead layer to obtain the PMUT chip.

The present invention preferably uses a pad mask template to deposit and draw the lead layer on the surface of the insulating layer.

In the present invention, the Au-Ge eutectic bond on _SiO2 in the insulating layer provides mechanical anchoring and electrical contact for the PMUT, which is formed on a SOI MEMS wafer that is combined with a CMOS wafer that provides the signal processing electronics.

In the present invention, the array composed of the PMUT chips is connected to a rigid or flexible PCB through wires. Each PMUT chip in the prepared array has a dedicated receiving (Rx) amplifier, which is connected to the bottom electrode layer in the receiving stage, and the top electrode layer of each PMUT chip is connected to a 24V transmitting amplifier (Tx) in the transmitting stage. In order to protect the Rx amplifier from the influence of high-voltage signals, the transmitting/receiving conversion switch connects each bottom electrode layer to the ground in the transmission stage. FIG2 shows a cross-sectional view of the integrated waveguide piezoelectric micromechanical ultrasonic transducer described in Example 1 during ultrasonic imaging. The MEMS chip and the CMOS chip are bonded together using an Au-Ge common chip, and the waveguide etched into the 300μm thick Si structure layer of the MEMS chip is used to guide ultrasound to the imaging target.

After obtaining the PMUT chip, the present invention performs ion etching on the bottom silicon layer to form the cavity, thereby obtaining the integrated waveguide piezoelectric micromechanical ultrasonic transducer.

In the present invention, the ion etching is preferably deep reactive ion etching (DRIE), and the present invention releases the vibration layer from the back side of the wafer to form an acoustic waveguide. The present invention has no particular limitation on the specific method of the deep reactive ion etching, and a method well known to those skilled in the art can be used.

The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Example 1

The integrated waveguide piezoelectric micromachined ultrasonic transducer is prepared, comprising the following steps:

Step 1: First, select a 4-inch SOI substrate and clean the surface of the SOI film using standard RCA.

The process starts with (a) in Figure 1, where a 0.2 μm thick aluminum nitride (AlN) layer is sputtered as a seed layer, a 0.2 μm thick Mo bottom electrode layer precursor is grown on the seed layer by magnetron sputtering, 1.5 μm AlN (with 002 crystal orientation) is magnetron sputtered onto the Mo bottom electrode as a piezoelectric layer precursor, and then 0.2 μm Mo is magnetron sputtered onto the AlN piezoelectric layer as a top electrode layer precursor.

Step 2: As shown in FIG. 1( b), the top electrode layer precursor is patterned using fluorine-based plasma etching (specific steps are: spin coating a 1.25 μm thick negative photoresist mask on the surface of the top electrode layer precursor, developing in a developer MF-319 to obtain a photolithography pattern, converting the etching gas SF ₆ into plasma, and etching the top electrode layer precursor), the AlN piezoelectric layer precursor is patterned (specific steps are: spin coating a 1.25 μm thick negative photoresist mask on the surface of the AlN piezoelectric layer precursor, developing in a developer MF-319 to obtain a photolithography pattern, converting the etching gas Cl ₂ into plasma, and etching the AlN piezoelectric layer precursor) to generate vibration boundaries and using chlorine-based plasma etching to access the bottom electrode layer (specific steps are: spin coating a 1.25 μm thick negative photoresist mask on the surface of the bottom electrode layer precursor, developing in a developer MF-319 to obtain a photolithography pattern, converting the etching gas SF ₆ is converted into plasma and the bottom electrode layer precursor is etched). In order to improve the good coupling with the basic vibration mode of the diaphragm, the top electrode layer is designed to have an area diaphragm coverage rate of 44.5%.

Step 3: As shown in Figure 1(c), to protect the upper surface electrode of the PMUT sensor chip and prevent short circuit when working in a conductive medium, a 300nm plasma chemical vapor deposition (PCVD) _SiO2 film is deposited on its surface as an insulating layer.

Step 4: As shown in Figure 1(d), the via openings are patterned by reactive ion etching (RIE) of _SiO2 .

Step 5: As shown in Figure 1 (e), a pad mask template is used to deposit and draw metal pads (Ti/Au=20/200μm) on the surface of the Mo top electrode layer to complete the PMUT chip preparation. In this step, the Au-Ge eutectic bond on _SiO2 provides mechanical anchoring and electrical contact for the PMUT, which is formed on the SOI MEMS wafer, which is combined with the CMOS wafer that provides signal processing electronics.

Step 6: As shown in (f) in Figure 1, after the CMOS-MEMS wafer is bonded, the vibration layer is released from the back of the wafer by deep reactive ion etching (DRIE) to form a cavity with a bottom side length of 108 μm, a square shape and a height of 300 μm.

Comparative Example

The same as the first embodiment, the only difference is that no cavity is formed.

The transmission mode pulse response and performance of the piezoelectric micromechanical ultrasonic transducer prepared in the embodiment and the comparative example in liquid were evaluated. The commercial software COMSOL Multiphysics 5.6 was used to establish acoustic-piezoelectric-force multi-physics field modeling for PMUT devices with waveguide (Example 1) and without waveguide (Comparative example), and transient analysis was performed. FIG3 shows the simulated sound pressure of the acoustic pulse near (~100μm) and far (~700μm) from the PMUT surface under the 1V, 20MHz sine wave drive, at time t=75ns and 950ns. FIG3 (a) is the simulated sound pressure diagram of the PMUT device of the comparative example at 75ns, (b) is the simulated sound pressure diagram of the PMUT device of the comparative example at 950ns, (c) is the simulated sound pressure diagram of the PMUT device of Example 1 at 75ns, and (d) is the simulated sound pressure diagram of the PMUT device of Example 1 at 950ns. It can be seen that for the PMUT without waveguide, the peak pressure is reduced by nearly 2.7 times from 4kPa at 100μm to 1.5kPa at 700μm. In contrast, the PMUT with waveguide shows that the peak pressure is almost unchanged when the acoustic energy propagates in the waveguide section, and the sound pressure amplitude is almost unchanged from 140kPa at 100μm to 120kPa at 600μm.

In summary, the waveguide PMUT based on AIN piezoelectric material proposed in the present invention can be connected to the CMOS circuit at the wafer level to realize the operation of individually addressing each MUT chip in the array. Compared with the complex signal processing required for phased array ultrasonic imaging, the existence of the waveguide can read out the ultrasonic image pixel by pixel because the waveguide isolates the pulse echo signal path of each PMUT chip from its adjacent pulse echo signal path.

The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims (10)

1. The integrated waveguide piezoelectric micromachined ultrasonic transducer is characterized by comprising a waveguide section and a PMUT chip, wherein the PMUT chip comprises a substrate, an AlN seed layer, a bottom electrode layer, an AlN piezoelectric layer, a top electrode layer, an insulating layer and a lead layer which are sequentially stacked from bottom to top, the substrate is an SOI substrate, the SOI substrate comprises a bottom silicon layer, an oxygen-buried layer and a structural silicon layer which are sequentially stacked from bottom to top, and the AlN seed layer is positioned on the surface of the structural silicon layer;

The waveguide section is a cavity, the cavity is formed by ion etching of the bottom silicon layer, and the depth of the cavity is equal to the thickness of the bottom silicon layer.

2. The integrated waveguide piezoelectric micromachined ultrasonic transducer of claim 1, wherein the cavity is a cuboid, a bottom surface of the cuboid is a square, and a side length of the square is a side length of a vibrating diaphragm of the integrated waveguide piezoelectric micromachined ultrasonic transducer.

3. The integrated waveguide piezoelectric micromachined ultrasonic transducer of claim 1, wherein surfaces of the bottom electrode layer and the top electrode layer are provided with via openings.

4. An integrated waveguide piezoelectric micromachined ultrasonic transducer according to claim 1 or 3, wherein the material of the bottom electrode layer and the top electrode layer is independently Pt, ti, al or Mo.

5. The integrated waveguide piezoelectric micromachined ultrasonic transducer of claim 1, wherein the insulating layer is silicon dioxide.

6. The method for manufacturing an integrated waveguide piezoelectric micromechanical ultrasonic transducer according to any one of claims 1-5, characterized by comprising the steps of:

Depositing on the surface of the SOI substrate, sequentially forming an AlN seed layer, a bottom electrode layer precursor, an AlN piezoelectric layer precursor and a top electrode layer precursor, and then sequentially patterning the top electrode layer precursor, the AlN piezoelectric layer precursor and the bottom electrode layer precursor to form the bottom electrode layer, the AlN piezoelectric layer and the top electrode layer;

depositing on the surfaces of the bottom electrode layer, the AlN piezoelectric layer and the top electrode layer to form the insulating layer;

depositing on the surface of the insulating layer to form the lead layer, thereby obtaining the PMUT chip;

and performing ion etching on the bottom silicon layer to form the cavity, thereby obtaining the integrated waveguide piezoelectric micro-mechanical ultrasonic transducer.

7. The method of manufacturing according to claim 6, wherein the method of patterning the top electrode layer precursor and the bottom electrode layer precursor is fluorine-based plasma etching, and the method of patterning the AlN piezoelectric layer precursor is chlorine-based plasma etching.

8. The method of manufacturing according to claim 6 or 7, wherein the area of the patterned top electrode layer precursor is 44.5% of the vibrating diaphragm area of the integrated waveguide piezoelectric micromechanical ultrasonic transducer.

9. The method of manufacturing according to claim 6, further comprising ion etching the surfaces of the bottom electrode layer and the top electrode layer to form the via openings before forming the insulating layer.

10. The method of claim 6, wherein the ion etching is deep reactive ion etching.