MEMS ultrasonic transducer made of double piezoelectric materials, manufacturing method and electronic equipment

Abstract

The invention discloses an MEMS ultrasonic transducer made of double piezoelectric materials, a manufacturing method and electronic equipment, the MEMS ultrasonic transducer comprises a substrate with a concave cavity and a vibrating diaphragm, the vibrating diaphragm comprises a first sandwich structure which is arranged on the substrate and is provided with a first piezoelectric layer, a filling layer arranged on the first sandwich structure, and a second sandwich structure which is arranged on the filling layer and is provided with a second piezoelectric layer; the first piezoelectric layer of the first sandwich structure is an AlN layer, and the second piezoelectric layer of the second sandwich structure is a PZT layer; or the first piezoelectric layer of the first sandwich structure is a PZT layer, and the second piezoelectric layer of the second sandwich structure is an AlN layer. According to the MEMS ultrasonic transducer with the double piezoelectric materials, the two piezoelectric layers are made of different materials, the vibrating diaphragm of the ultrasonic transducer comprises the PZT layer and the AlN layer at the same time, the PZT layer and the AlN layer form strong mechanical coupling, and behavior modes of the PZT layer and the AlN layer influence each other, so that the PZT layer and the AlN layer have a better matching relation, and the transmitting sensitivity and the receiving sensitivity of the ultrasonic transducer are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a piezoelectric micro-electro-mechanical system (MEMS) ultrasonic transducer and a manufacturing method, in particular to a MEMS ultrasonic transducer with double piezoelectric materials and a manufacturing method and an electronic device. BACKGROUND

[0002] The piezoelectric micro-electro-mechanical system (MEMS) ultrasonic transducer can emit and receive ultrasonic waves and is widely used. However, its transmitting sensitivity and receiving sensitivity need to be further improved. The piezoelectric micro-electro-mechanical system ultrasonic transducer based on PZT has high transmitting sensitivity and low receiving sensitivity; and the piezoelectric micro-electro-mechanical system ultrasonic transducer based on AlN has low transmitting sensitivity and high receiving sensitivity. The piezoelectric micro-electro-mechanical system ultrasonic transducers based on PZT and AlN are arranged side by side to make full use of the advantages of both, but the area utilization rate is low.

[0003] Therefore, the prior art has problems to be further improved and developed. SUMMARY

[0004] (I) Invention purpose: in order to solve the above problems existing in the prior art, the purpose of the present application is to provide a MEMS ultrasonic transducer with double piezoelectric materials of a new structure.

[0005] (II) Technical scheme: in order to solve the above technical problems, the present application provides a MEMS ultrasonic transducer with double piezoelectric materials, comprising a substrate with a concave cavity and a diaphragm, wherein the diaphragm comprises: a first sandwich structure with a first piezoelectric layer arranged on the substrate, a filling layer arranged on the first sandwich structure, and a second sandwich structure with a second piezoelectric layer arranged on the filling layer. The first piezoelectric layer of the first sandwich structure is an AlN layer, and the second piezoelectric layer of the second sandwich structure is a PZT layer; or the first piezoelectric layer of the first sandwich structure is a PZT layer, and the second piezoelectric layer of the second sandwich structure is an AlN layer.

[0006] The MEMS ultrasonic transducer with double piezoelectric materials, wherein the thickness ratio T1 is defined as the value of the thickness of the PZT layer to the thickness of the AlN layer, the thickness ratio T2 is defined as the value of the thickness of the filling layer to the thickness of the PZT layer, and the normalized sensitivity product is obtained by extracting the product of the transmitting sensitivity and the receiving sensitivity and performing normalization operation.

[0007] The MEMS ultrasonic transducer with double piezoelectric materials, wherein when the thickness ratio T2 is constant, the thickness ratio T1 ranges from not less than 50% of the maximum sensitivity product under the thickness ratio T2.

[0008] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein, when 0≤T2<0.2, the thickness ratio T1 ranges from greater than or equal to 1 to less than or equal to 15; when 0.2≤T2<0.5, the thickness ratio T1 ranges from greater than or equal to 0.8 to less than or equal to 15; when 0.5≤T2<0.7, the thickness ratio T1 ranges from greater than or equal to 0.6 to less than or equal to 15.

[0009] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein, when the thickness ratio T2 is constant, the thickness ratio T1 ranges from no less than 80% of the maximum sensitivity product at the T2 value.

[0010] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein, when 0≤T2<0.2, the thickness ratio T1 ranges from greater than or equal to 1.5 to less than or equal to 5; when 0.2≤T2<0.5, the thickness ratio T1 ranges from greater than or equal to 1.25 to less than or equal to 5; when 0.5≤T2<0.7, the thickness ratio T1 ranges from greater than or equal to 1 to less than or equal to 5; when 0.7≤T2<1, the thickness ratio T1 ranges from greater than or equal to 0.8 to less than or equal to 5.

[0011] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein, the thickness ratio T1 ranges from no less than 95% of the maximum sensitivity product, and the thickness ratio T1 ranges from greater than or equal to 2 to less than or equal to 3.

[0012] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein, in the part with the electrically connected terminal, the extension of the first sandwich structure is a stepped structure, and the steps of the stepped structure are sequentially higher in the direction from the substrate upward.

[0013] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein, the stepped structure comprises a first step and a second step from the substrate upward, the height of the first step is lower than that of the second step, the first step corresponds to the upper surface and the side surface of the first bottom electrode, and the second step corresponds to the side surface of the first piezoelectric layer and the upper surface and the side surface of the first top electrode.

[0014] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein, the filling layer covers the upper surface of the substrate and the continuous surface of the stepped structure of the extension of the first sandwich structure.

[0015] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein the upper surface of the filling layer is flat, and the upper surface of the filling layer is covered with a second sandwich structure.

[0016] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein the lower bottom of the concave cavity is provided with a through opening.

[0017] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein the piezoelectric thin film material of the PZT layer is PZT, and the PZT is lead zirconate titanate or doped lead zirconate titanate; and the piezoelectric thin film material of the AlN layer is AlN, and the AlN is aluminum nitride or doped aluminum nitride.

[0018] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein the first sandwich structure comprises, from bottom to top, a first bottom electrode, a first piezoelectric layer, and a first top electrode; and the second sandwich structure comprises, from bottom to top, a second bottom electrode, a second piezoelectric layer, and a second top electrode.

[0019] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein when the piezoelectric layer is a PZT layer, the first bottom electrode of the first sandwich structure or the second bottom electrode of the second sandwich structure is composed of multiple material layers, and the material layers are arranged in the order of zirconium oxide, platinum, SRO or titanium, platinum, and a buffer layer from bottom to top, wherein the zirconium oxide or titanium serves as a seed layer.

[0020] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein when the piezoelectric layer is an AlN layer, the first bottom electrode of the first sandwich structure or the second bottom electrode of the second sandwich structure is composed of multiple material layers, and the material layers are arranged in the order of aluminum nitride and molybdenum from bottom to top, wherein the aluminum nitride serves as a seed layer.

[0021] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein the material of the first top electrode of the first sandwich structure or the second top electrode of the second sandwich structure comprises metal materials such as molybdenum, platinum, magnesium, aluminum, ruthenium, titanium, iridium, osmium, silver, gold, titanium, tungsten, copper, and chromium, and alloys or composite layers of the metals.

[0022] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein the diaphragm is square in plan view, and the diaphragm is divided into four triangular diaphragms by a cross-shaped slit; or the diaphragm is circular in plan view, and the second top electrode and the first top electrode of the diaphragm are circular in shape, and the area of the second top electrode is smaller than the area of the first top electrode.

[0023] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein the left edge of the filling layer extends to align with the left edge of the substrate, and the right edge of the filling layer participates in forming the slit near the central axis.

[0024] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein the material of the filling layer comprises silicon, polysilicon, polymer, amorphous silicon, silicon dioxide, silicon nitride, silicon carbide, and aluminum nitride.

[0025] The MEMS ultrasonic transducer of bimorph piezoelectric material, wherein the filling layer completely wraps the epitaxial end face of the first sandwich structure covering the diaphragm.

[0026] The method for manufacturing the MEMS ultrasonic transducer of bimorph piezoelectric material, comprising the following steps: Step one, processing a concave cavity on the substrate, covering the concave cavity of the substrate by a sacrificial layer; Step two, sequentially depositing a first sandwich structure on the surface of the substrate and the surface of the sacrificial layer; Step three, covering the filling layer material on the surface of the substrate and the first sandwich structure; Step four, forming a second sandwich structure on the surface of the filling layer; The first piezoelectric layer of the first sandwich structure is an AlN layer, and the second piezoelectric layer of the second sandwich structure is a PZT layer; or the first piezoelectric layer of the first sandwich structure is a PZT layer, and the second piezoelectric layer of the second sandwich structure is an AlN layer.

[0027] The method for manufacturing the MEMS ultrasonic transducer of bimorph piezoelectric material, wherein the first sandwich structure in step three comprises a first bottom electrode, a first piezoelectric layer and a first top electrode deposited in sequence.

[0028] The method for manufacturing the MEMS ultrasonic transducer of bimorph piezoelectric material, wherein step three further comprises the following steps: forming a slit near the central region by patterning and etching process to make the right edge of the first sandwich structure.

[0029] The method for manufacturing the MEMS ultrasonic transducer of bimorph piezoelectric material, wherein step three further comprises the following steps: The left edge of the first piezoelectric layer and the first top electrode is recessed to the right relative to the left edge of the first bottom electrode to form a stepped structure by patterning and etching process.

[0030] The manufacturing method of the MEMS ultrasonic transducer of the double piezoelectric material, wherein the step four comprises: forming a slit on the right edge of the second sandwich structure close to the central area through a patterning and etching process; and forming a protective layer on the upper surface of the second sandwich structure and the slit through a deposition and grinding process.

[0031] The manufacturing method of the MEMS ultrasonic transducer of the double piezoelectric material, wherein the step four further comprises: after the piezoelectric micro-electro-mechanical system ultrasonic transducer is turned upside down, a through-type opening is made on the back of the substrate through a patterning and deep etching process, and the boundary of the through-type opening is located inside the lower surface boundary of the cavity.

[0032] The manufacturing method of the MEMS ultrasonic transducer of the double piezoelectric material, wherein the step four further comprises: the protective layer and the sacrificial layer are removed through an etching and releasing process.

[0033] The manufacturing method of the MEMS ultrasonic transducer of the double piezoelectric material, wherein the step four further comprises: the upper surface of the filling layer is planarized.

[0034] An electronic device, comprising: a processor, a memory, a communication interface and a communication bus, the processor, the memory and the communication interface complete the communication among each other through the communication bus, and the processor is connected with the MEMS ultrasonic transducer of the double piezoelectric material.

[0035] (Three) beneficial effects: the MEMS ultrasonic transducer of the double piezoelectric material provided by the application has different materials of two piezoelectric layers, the diaphragm of the ultrasonic transducer comprises a PZT layer and an AlN layer, the PZT layer and the AlN layer form strong mechanical coupling, the behavior modes of the PZT layer and the AlN layer influence each other, and therefore the PZT layer and the AlN layer have an optimal matching relationship, thereby improving the performance of the transmitting sensitivity and the receiving sensitivity of the ultrasonic transducer. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a schematic view of the relationship between the thickness ratio T1, the thickness ratio T2 and the normalized sensitivity product in the MEMS ultrasonic transducer of the double piezoelectric material of the application; Figure 2 is a top view of the MEMS ultrasonic transducer of the double piezoelectric material with a cross-shaped slit type of the application; Figure 3 is a top view of the MEMS ultrasonic transducer of the double piezoelectric material with a cross-shaped slit type of the application; Figure 2 is a structure schematic view of a cross-sectional view along the OA direction; Figure 4 is a top view of the MEMS ultrasonic transducer of the double piezoelectric material with a cross-shaped slit type of the application; Figure 2Structure schematic diagram of the cross-sectional view along the OA direction; Figure 5 is a top view of the MEMS ultrasonic transducer with cross-shaped slit type double piezoelectric material of the present application Figure 2 Structure schematic diagram of the cross-sectional view along the OA direction, and the first piezoelectric layer of the first sandwich structure of the ultrasonic transducer is set as an AlN layer, and the second piezoelectric layer of the second sandwich structure is set as a PZT layer; Figure 6 is a top view of the MEMS ultrasonic transducer with cross-shaped slit type double piezoelectric material of the present application Figure 2 Structure schematic diagram of the cross-sectional view along the OA direction, and the first piezoelectric layer of the first sandwich structure of the ultrasonic transducer is set as an AlN layer, and the second piezoelectric layer of the second sandwich structure is set as a PZT layer; Figure 7 is a top view of the MEMS ultrasonic transducer with cross-shaped slit type double piezoelectric material of the present application Figure 8 is a top view of the MEMS ultrasonic transducer with cross-shaped slit type double piezoelectric material of the present application Figure 7 Structure schematic diagram of the cross-sectional view along the OA direction; Figure 9 is a top view of the MEMS ultrasonic transducer with cross-shaped slit type double piezoelectric material of the present application Figure 7 Structure schematic diagram of the cross-sectional view along the OA direction; Figure 10 is a top view of the MEMS ultrasonic transducer with cross-shaped slit type double piezoelectric material of the present application Figure 7 Structure schematic diagram of the cross-sectional view along the OA direction, and the first piezoelectric layer of the first sandwich structure of the ultrasonic transducer is set as an AlN layer, and the second piezoelectric layer of the second sandwich structure is set as a PZT layer; Figure 11 is a top view of the MEMS ultrasonic transducer with cross-shaped slit type double piezoelectric material of the present application Figure 7 Structure schematic diagram of the cross-sectional view along the OA direction, and the first piezoelectric layer of the first sandwich structure of the ultrasonic transducer is set as an AlN layer, and the second piezoelectric layer of the second sandwich structure is set as a PZT layer; Figure 12 is a top view of the MEMS ultrasonic transducer with cross-shaped slit type double piezoelectric material of the present application Figure 13 is a top view of the MEMS ultrasonic transducer with cross-shaped slit type double piezoelectric material of the present application Figure 14 is a top view of the MEMS ultrasonic transducer with cross-shaped slit type double piezoelectric material of the present application Figure 15 is the effect diagram of step 104 of the first preferred embodiment of the MEMS ultrasonic transducer manufacturing method with cross-shaped slit type double piezoelectric material of the present application; Figure 16 is the effect diagram of step 105 of the first preferred embodiment of the MEMS ultrasonic transducer manufacturing method with cross-shaped slit type double piezoelectric material of the present application; Figure 17 is the effect diagram of step 106 of the first preferred embodiment of the MEMS ultrasonic transducer manufacturing method with cross-shaped slit type double piezoelectric material of the present application; Figure 18 is the effect diagram of step 107 of the first preferred embodiment of the MEMS ultrasonic transducer manufacturing method with cross-shaped slit type double piezoelectric material of the present application; Figure 19 is the effect diagram of step 108 of the first preferred embodiment of the MEMS ultrasonic transducer manufacturing method with cross-shaped slit type double piezoelectric material of the present application; Figure 20 is the effect diagram of step 109 of the first preferred embodiment of the MEMS ultrasonic transducer manufacturing method with cross-shaped slit type double piezoelectric material of the present application; Figure 21 is the effect diagram of step 110 of the first preferred embodiment of the MEMS ultrasonic transducer manufacturing method with cross-shaped slit type double piezoelectric material of the present application; Figure 22 is the effect diagram of step 111 of the first preferred embodiment of the MEMS ultrasonic transducer manufacturing method with cross-shaped slit type double piezoelectric material of the present application; Figure 23 is the effect diagram of step 112 of the first preferred embodiment of the MEMS ultrasonic transducer manufacturing method with cross-shaped slit type double piezoelectric material of the present application; Figure 24 is the effect diagram of step 113 of the first preferred embodiment of the MEMS ultrasonic transducer manufacturing method with cross-shaped slit type double piezoelectric material of the present application; Figure 25 is the effect diagram of step 114 of the first preferred embodiment of the MEMS ultrasonic transducer manufacturing method with cross-shaped slit type double piezoelectric material of the present application; Figure 26 is the effect diagram of step 115 of the first preferred embodiment of the MEMS ultrasonic transducer manufacturing method with cross-shaped slit type double piezoelectric material of the present application; Figure 27 is the effect diagram of step 201 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with cross-shaped slit type double piezoelectric material of the present application; Figure 28is the effect diagram of step 202 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 29 is the effect diagram of step 203 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 30 is the effect diagram of step 204 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 31 is the effect diagram of step 205 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 32 is the effect diagram of step 206 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 33 is the effect diagram of step 207 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 34 is the effect diagram of step 208 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 35 is the effect diagram of step 209 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 36 is the effect diagram of step 210 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 37 is the effect diagram of step 211 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 38 is the effect diagram of step 212 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 39 is the effect diagram of step 213 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 40 is the effect diagram of step 214 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 41is the effect picture of step 215 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 42 is the effect picture of step 216 of the second preferred embodiment of the MEMS ultrasonic transducer manufacturing method with the cross-shaped slit type double piezoelectric material of the application; Figure 43 is the structural schematic diagram of the electronic device of the MEMS ultrasonic transducer with the double piezoelectric material of the application. DETAILED DESCRIPTION

[0037] The application will be further described below in connection with preferred embodiments, and more details are set forth in the following description in order to fully understand the application, however, the application can be implemented in many different ways other than the description, and the person skilled in the art can make similar generalization and deduction according to the actual application without departing from the connotation of the application, therefore, the protection scope of the application should not be limited by the content of the specific embodiments.

[0038] The drawings are the schematic diagrams of the embodiments of the application, and it should be noted that the drawings are only examples, not drawn according to the condition of the same scale, and should not be used as the limitation of the actual claimed protection scope of the application.

[0039] The MEMS ultrasonic transducer with the double piezoelectric material provided by the application, the first preferred embodiment, comprises a substrate S100 with a concave cavity and a diaphragm; the diaphragm comprises: a first sandwich structure arranged on the substrate S100, a filling layer F200 arranged on the first sandwich structure, and a second sandwich structure arranged on the filling layer F200; the first sandwich structure comprises, from the substrate upwards, a first bottom electrode B100, a first piezoelectric layer P100, and a first top electrode T100 in sequence; the second sandwich structure comprises, from the filling layer upwards, a second bottom electrode B200, a second piezoelectric layer P200, and a second top electrode in sequence; the filling layer F200 and the first and second sandwich structures arranged above and below are collectively referred to as the diaphragm, that is, the acoustic unit.

[0040] Preferably, the first piezoelectric layer is an AlN layer, and the second piezoelectric layer is a PZT layer, or the first piezoelectric layer is a PZT layer, and the second piezoelectric layer is an AlN layer.

[0041] The application provides a MEMS ultrasonic transducer of double piezoelectric materials, the ultrasonic transducer comprises two piezoelectric layers, one of which is an AlN layer, and the other is a PZT layer, the piezoelectric film material of the PZT layer is PZT, and the PZT is lead zirconate titanate or doped lead zirconate titanate; the piezoelectric film material of the AlN layer is AlN, and the AlN is aluminum nitride or doped aluminum nitride. The two piezoelectric layers and the corresponding top electrode and bottom electrode form two sandwich structures, one of which is stacked on the other, and a filling layer structure is arranged between the two sandwich structures. The diaphragm of the ultrasonic transducer comprises the PZT layer and the AlN layer, and therefore the PZT layer and the AlN layer form a strong mechanical coupling, the behavior mode of the PZT layer and the AlN layer is influenced by each other, and therefore the PZT layer and the AlN layer have an optimal matching relationship, the performance of the transmitting sensitivity and the receiving sensitivity of the ultrasonic transducer is improved. The materials of the two piezoelectric layers are different, and the thickness ratio of the two piezoelectric layers is set to further optimize the sensitivity performance of the whole ultrasonic transducer.

[0042] The application optimizes the thickness ratio of the PZT layer and the AlN layer, under the condition that the resonant frequency of the device is kept unchanged, the thickness ratio T1 is defined as the value of the thickness ratio of the PZT layer to the thickness of the AlN layer, the thickness ratio T2 is defined as the value of the thickness ratio of the filling layer to the thickness of the PZT layer, and the product of the transmitting sensitivity and the receiving sensitivity is extracted and normalized to obtain the normalized sensitivity product. Wherein, the X axis represents the thickness ratio T1, the Y axis represents the normalized sensitivity product, and the trend curve represents the thickness ratio T2, as shown in the figure. Figure 1 When the thickness ratio T2 is constant, the normalized sensitivity product increases first and then decreases with the increase of the thickness ratio T1, and the optimal thickness ratio T1 decreases with the increase of the thickness ratio T2. In addition, with the increase of the thickness ratio T2, the normalized sensitivity product at the optimal thickness ratio T1 decreases.

[0043] Preferably, when the thickness ratio T2 is constant, the thickness ratio T1 is selected in the range of not less than 50% of the maximum sensitivity product under the thickness ratio T2, when 0≤T2<0.2, the thickness ratio T1 is greater than or equal to 1 and less than or equal to 15; when 0.2≤T2<0.5, the thickness ratio T1 is greater than or equal to 0.8 and less than or equal to 15; when 0.5≤T2<0.7, the thickness ratio T1 is greater than or equal to 0.6 and less than or equal to 15; when 0.7≤T2<1, the thickness ratio T1 is greater than or equal to 0.5 and less than or equal to 15.

[0044] Preferably, when the thickness ratio T2 is constant, the thickness ratio T1 is preferably selected in the range of not less than 80% of the maximum sensitivity product under the thickness ratio T2, when 0.2≤T2<0.5, the thickness ratio T1 ranges from greater than or equal to 1.25 to less than or equal to 5; when 0.2≤T2<0.5, the thickness ratio T1 ranges from greater than or equal to 1.25 to less than or equal to 5; when 0.5≤T2<0.7, the thickness ratio T1 ranges from greater than or equal to 1 to less than or equal to 5; when 0.7≤T2<1, the thickness ratio T1 ranges from greater than or equal to 0.8 to less than or equal to 5.

[0045] Preferably, the thickness ratio T1 ranges from no less than 95% of the maximum sensitivity product, then T1 ranges from greater than or equal to 2 to less than or equal to 3; the MEMS ultrasonic transducer of the double piezoelectric material provided by the present application can be a piezoelectric micro-electro-mechanical system ultrasonic transducer with a cross-shaped slit type, such as Figures 2-6 as shown.

[0046] The second preferred embodiment of the present application is a MEMS ultrasonic transducer of the double piezoelectric material with a cross-shaped slit type, as shown in Figure 2 the vibrating diaphragm is divided into four triangular vibrating diaphragms by the cross-shaped slit, the first triangular vibrating diaphragm T210 includes the second top electrode one module T200 of the upper layer, the second triangular vibrating diaphragm T210a includes the second top electrode two module T200a of the upper layer, the third triangular vibrating diaphragm T210b includes the second top electrode three module T200b of the upper layer, and the fourth triangular vibrating diaphragm T210c includes the second top electrode four module T200c of the upper layer, the triangular vibrating diaphragm includes the top electrode of the four acoustic region surfaces.

[0047] The present application sets several contacts and other electrical connection structures for inputting electrical signals beside the acoustic region of each triangular region in the first triangular vibrating diaphragm T210, the second triangular vibrating diaphragm T210a, the third triangular vibrating diaphragm T210b, and the fourth triangular vibrating diaphragm T210c, such as Figure 2 , Figure 3The first, second, third and fourth contact metal layers M101, M111, M121 and M131 are connected to the first, second, third and fourth bottom and top electrodes B100, B200, T100 and T200 through surface conductor structures. Take the first triangular diaphragm T210 as an example. The first, second, third and fourth contact metal layers M101, M111, M121 and M131 are distributed on the left side of the edge of the first triangular diaphragm T210. The fourth contact metal layer M131 is directly connected to the second top electrode through a surface conductor structure. The first contact metal layer M101 is connected to the first metal layer M100 through a surface conductor structure, and the first metal layer M100 is further connected to the first bottom electrode B100 located in the deep layer. The second contact metal layer M111 is connected to the second metal layer M110 through a surface conductor structure, and the second metal layer M110 is further connected to the first top electrode T100 located in the deep layer. The third contact metal layer M121 is connected to the third metal layer M120 through a surface conductor structure, and the third metal layer M120 is further connected to the second bottom electrode B200 located in the deep layer.

[0048] The contact and electrical connection structures of the second, third and fourth triangular diaphragms are the same as those of the first triangular diaphragm, and will not be described here.

[0049] The first bottom electrode B100 of the first sandwich structure is electrically led out through the metal layer M100 in the through hole of the filling layer F200 and the second piezoelectric layer P200. The first top electrode T100 of the first sandwich structure is electrically led out through the metal layer M110 in the through hole of the filling layer F200 and the second piezoelectric layer P200. The second bottom electrode B200 of the second sandwich piezoelectric unit is electrically led out through the metal layer M120 in the through hole of the second piezoelectric layer P200.

[0050] The second preferred embodiment of the MEMS ultrasonic transducer with double piezoelectric materials of cross-shaped slit type is described in detail taking the PZT layer of the first sandwich structure covered by the lower surface of the filling layer F200 as an example, and the AlN layer of the second sandwich structure on the upper surface of the filling layer F200 as an example of the second piezoelectric layer P200.

[0051] The top view of the second preferred embodiment of the MEMS ultrasonic transducer with double piezoelectric materials of the application Figure 2 The cross section along the OA direction is a structure with an electrical connection terminal part as shown in Figure 3 The substrate S100 with a concave cavity has a through-type opening on the lower bottom of the concave cavity.

[0052] The first bottom electrode B100 is composed of multiple layers of materials, which are arranged in the order from bottom to top as zirconium oxide, platinum, SRO or titanium, platinum, buffer layer, wherein the zirconium oxide or titanium serves as a seed layer, and the SRO or buffer layer is used to optimize the growth of the PZT layer of the first piezoelectric layer P100 which it contacts.

[0053] The left edge of the first bottom electrode B100 is indented to the right relative to the left edge of the substrate S100. The piezoelectric thin film material of the first piezoelectric layer P100 is PZT, which is lead zirconate titanate or doped lead zirconate titanate, etc. The metal material of the first top electrode T100 includes molybdenum, platinum, magnesium, aluminum, ruthenium, titanium, iridium, osmium, silver, gold, titanium, tungsten, copper, chromium, etc., as well as alloys or composite layers of the metals. Among them, the edges of the first top electrode T100, the first piezoelectric layer P100 and the first bottom electrode B100 on the side close to the central axis OO' are substantially aligned, while on the side away from the central axis OO', the first top electrode T100 and the first piezoelectric layer P100 are indented to the right relative to the first bottom electrode B100, thereby exposing a portion of the first bottom electrode B100 to the left side of the first top electrode T100 and the first piezoelectric layer P100.

[0054] The first sandwich structure of the diaphragm has a step-shaped extension of the electrical connection terminal, and the steps are sequentially raised in the direction from the substrate S100 upwards. The step-shaped extension includes a first step and a second step from the substrate S100 upwards, the height of the first step is lower than that of the second step, the first step corresponds to the upper surface and side surface of the first bottom electrode B100, and the second step corresponds to the side surface of the first piezoelectric layer P100 and the upper surface and side surface of the first top electrode T100. The filling layer F200 covers the continuous surface composed of the substrate S100 and the extension of the first sandwich structure. The continuous surface includes part of the upper surface of the substrate S100, part of the upper surface and side surface of the first bottom electrode B100, the upper surface and side surface of the first top electrode T100, and the side surface of the first piezoelectric layer P100, the left edge of the filling layer F200 extends to align with the left edge of the substrate S100, and the right edge of the filling layer F200 participates in forming the slit near OO'. The filling layer F200 of the present application completely wraps the extension of the first sandwich structure covering the diaphragm, and therefore can enhance the mechanical strength of the first piezoelectric layer, the first bottom electrode and the first top electrode, and increase the electrical breakdown strength.

[0055] The top surface of the filling layer F200 is flat and covered with a second bottom electrode B200 in a second sandwich structure. This second bottom electrode B200 is composed of multiple material layers, arranged from bottom to top: aluminum nitride and molybdenum, with the aluminum nitride serving as a seed layer. The left edge of the second bottom electrode B200 is indented to the right relative to the left edge of the first top electrode T100. The surface of the second bottom electrode B200 and a portion of the surface of the filling layer F200 are covered with a second piezoelectric layer P200 in a second sandwich structure. The second piezoelectric layer P200 is made of AlN, which is aluminum nitride or doped aluminum nitride. The left edge of the second piezoelectric layer P200 extends to align with the left edge of the substrate S100 and the filling layer F200. The right edge of the second piezoelectric layer P200 extends to substantially align with the right edge of the filling layer F200 and contributes to the formation of the slit near OO'. The surface of the second piezoelectric layer P200 is covered with a second top electrode T200 having a second sandwich structure. The metal material of the second top electrode T200 includes, but is not limited to, molybdenum, platinum, magnesium, aluminum, ruthenium, titanium, iridium, osmium, silver, gold, titanium, tungsten, copper, chromium, and the like, as well as alloys or composite layers of such metals. The right edge of the second top electrode T200 is slightly indented to the left or substantially aligned with the right edge of the second bottom electrode B200, and the left edge of the second top electrode T200 is indented to the right relative to the left edge of the second bottom electrode B200.

[0056] A top view of a second preferred embodiment of the present invention Figure 2 The cross section along the OB direction is the structure without the electrical connection terminal part, such as Figure 4 As shown: The left edges of the first bottom electrode B100 and the first top electrode T100 of the first sandwich structure and the second bottom electrode B200 and the second top electrode T200 of the second sandwich structure only extend a short distance to the left relative to the upper left edge of the concave cavity. Figure 4 The cross-sectional structure in Figure 3 In the through-hole type electrical connection structure, the left edges of the second bottom electrode B200, the second top electrode T200 of the second sandwich structure and the first top electrode T100 of the first sandwich structure are basically aligned with the left edges of the electrodes located thereunder, and there is no significant feature of indentation to the right.

[0057] The third preferred embodiment of the present invention is the MEMS ultrasonic transducer with a cross-shaped slit-type dual piezoelectric material, which is described in detail by taking the first piezoelectric layer P100 of the first sandwich structure covered by the lower surface of the filling layer F200 as an AlN layer and the second piezoelectric layer P200 of the second sandwich structure on the upper surface of the filling layer F200 as a PZT layer as an example. Figure 5 and Figure 6 shown.

[0058] The third preferred embodiment of the present invention is Figure 2 The cross section along the OA direction is a structure with electrical connection terminal parts, such as Figure 5 As shown, the difference from the second preferred embodiment is that: The right edge of the first piezoelectric layer P100 slightly crosses the right edge of the first bottom electrode B100 and contributes to the formation of the slit to the right of the central axis. The edges of the first top electrode T100 and the first bottom electrode B100 are substantially aligned on the side close to the central axis oo', and on the side away from oo'. The filling layer F200 covers the top and side surfaces of the first top electrode T100 and a portion of the top surface of the first piezoelectric layer P100. The second bottom electrode B200, the second piezoelectric layer P200, and the second top electrode T200 extend to the right edge until they are substantially aligned with the right edge of the filling layer F200 or slightly indented to the left, and contribute to the formation of the slit near oo'. The top surface of the filling layer F200 is flat. Because the upper surface of the filling layer F200 is flat, any layer of the second sandwich structure is also flat and will not bend, thus ensuring the reliability of the second sandwich structure. If there is no filling layer F200, the unevenness of the surface of the first sandwich structure will be transmitted to the second sandwich structure, resulting in a decrease in the reliability of the second sandwich structure. Alternatively, if the surface of the filling layer F200 is uneven, the unevenness of the surface of the first sandwich structure will also be transmitted to the second sandwich structure, resulting in a decrease in the reliability of the second sandwich structure.

[0059] The third preferred embodiment of the present invention is Figure 2 The cross section along the OB direction is the structure without the electrical connection terminal part, such as Figure 6 As shown, the second preferred embodiment is viewed from above Figure 2 The cross section along the OB direction Figure 4 The description is the same and will not be repeated here.

[0060] The fourth preferred embodiment of the present invention is a slitless dual piezoelectric MEMS ultrasonic transducer, such as Figures 7-11 Because there are no slits in the diaphragm region, the areas of the second top electrode T200 and the first top electrode T100 are reduced to circular shapes. The area of ​​the second top electrode T200 is larger than that of the first top electrode T100. The diaphragm region is composed of a series of circular first and second sandwich structures, with the centers of the first and second sandwich structures being located at the same position.

[0061] The present invention sets a number of contacts and other electrical connection structures for inputting electrical signals next to the acoustic area of ​​the first triangular diaphragm T200 area, such as Figure 7 、 Figure 8As shown. The first contact metal layer M101, the second contact metal layer M111, the third contact metal layer M121, and the fourth contact metal layer M131 are distributed on the left side of the edge of the first triangular diaphragm T200. The fourth contact metal layer M131 is directly connected to the second top electrode through a surface conductor structure. The first contact metal layer M101 is connected to the first metal layer M100 through a surface conductor structure, and the first metal layer M100 is further connected to the first bottom electrode B100 located in a deep layer. The second contact metal layer M111 is connected to the second metal layer M110 through a surface conductor structure, and the second metal layer M110 is further connected to the first top electrode T100 located in a deep layer. The third contact metal layer M121 is connected to the third metal layer M120 through a surface conductor structure, and the third metal layer M120 is further connected to the second bottom electrode B200 located in a deep layer.

[0062] The first bottom electrode B100 of the first sandwich structure of the present invention is electrically led out through the metal layer M100 in the through hole of the filling layer F200 and the second piezoelectric layer P200; the first top electrode T100 of the first sandwich structure is electrically led out through the metal layer M110 in the through hole of the filling layer F200 and the second piezoelectric layer P200; the second bottom electrode B200 of the second sandwich piezoelectric unit is electrically led out through the metal layer M120 in the through hole of the second piezoelectric layer P200.

[0063] The fourth preferred embodiment of the present invention is a slitless dual piezoelectric MEMS ultrasonic transducer, which is Figure 7 The cross section along the OA direction is a structure with electrical connection terminal parts, such as Figure 8 In a fourth preferred embodiment of the dual piezoelectric material MEMS ultrasonic transducer, the first sandwich structure includes a PZT layer, and the second sandwich structure includes an AlN layer.

[0064] like Figure 8 As shown, the cross-sectional view also extends a certain distance to the right of point 0, thereby showing the cross-sectional structure of the second top electrode T200 located on the right side of the central axis oo' and the portion below it. The slitless dual piezoelectric material MEMS ultrasonic transducer has a substrate S100, a concave cavity F100 is formed on the upper surface of the substrate S100, and a through-type opening is also formed within the lower bottom boundary of the concave cavity F100. The upper surface of the concave cavity F100 of the substrate S100 and the surface around the cavity are covered with a first bottom electrode B100 with a first sandwich structure, wherein the first bottom electrode B100 is composed of multiple material layers. The materials are arranged in the order of zirconium oxide, platinum, SRO or titanium, platinum, and buffer layer from bottom to top, wherein zirconium oxide or titanium acts as a seed layer, and SRO or buffer layer is used to optimize the growth of the PZT thin film it contacts.

[0065] A fourth preferred embodiment of the present application is a MEMS ultrasonic transducer of a double piezoelectric material without a slit, in a plan view Figure 7 A cross section along the OA direction is a structure with an electrical connection terminal portion, as shown in Figure 8 .

[0066] The first sandwich structure of the diaphragm has a step structure, and the steps are sequentially higher in a direction from the substrate S100 upward. The step structure includes a first step and a second step in a direction from the substrate S100 upward, the first step has a height lower than the second step, the first step corresponds to an upper surface and a side surface of the first bottom electrode B100, and the second step corresponds to a side surface of the first piezoelectric layer P100 and an upper surface and a side surface of the first top electrode T100.

[0067] A left side edge of the first bottom electrode B100 is recessed to the right relative to a left side edge of the substrate S100. The first bottom electrode B100 is covered with the first piezoelectric layer P100 of the first sandwich structure, the first piezoelectric layer P100 is made of PZT, and the PZT includes lead zirconate titanate, doped lead zirconate titanate, etc. The first piezoelectric layer P100 is covered with the first top electrode T100 of the first sandwich structure, and the metal material of the first top electrode T100 includes but is not limited to molybdenum, platinum, magnesium, aluminum, ruthenium, titanium, iridium, osmium, silver, gold, titanium, tungsten, copper, chromium, etc., and alloys or composite layers of the metals. The left side edge of the first top electrode T100 and the first piezoelectric layer P100 is recessed to the right relative to the left side edge of the first bottom electrode B100, so that a part of the first bottom electrode B100 is exposed to the left side of the first top electrode T100 and the first piezoelectric layer P100.

[0068] The filling layer F200 covers part of the upper surface of the substrate S100 and the step structure of the extension end surface of the first sandwich structure, and the step structure includes part of the upper surface and the side surface of the first bottom electrode B100, the upper surface and the side surface of the first top electrode T100, and the side surface of the first P100. The left side edge of the filling layer F200 extends to align with the left edge of the substrate S100.

[0069] A second bottom electrode B200 of a second sandwich structure is formed on the surface of the filling layer F200 after planarization, and is composed of multiple material layers, the materials of which are arranged in the order from bottom to top as aluminum nitride, molybdenum, wherein the aluminum nitride serves as a seed layer. The left edge of the second bottom electrode B200 is indented to the right relative to the left edge of the first top electrode T100. A second piezoelectric layer P200 of a second sandwich structure is formed on the surface of the second bottom electrode B200 and part of the surface of the filling layer F200, and is composed of AlN, including aluminum nitride or doped aluminum nitride, etc. The left edge of the second piezoelectric layer P200 extends to align with the left edge of the substrate S100 and the filling layer F200. A second top electrode T200 of a second sandwich structure is formed on the surface of the second piezoelectric layer P200, and the metal material of the second top electrode T200 includes but is not limited to molybdenum, platinum, magnesium, aluminum, ruthenium, titanium, iridium, osmium, silver, gold, titanium, tungsten, copper, chromium, etc. as well as alloys or composite layers of the metals. The left edge of the second top electrode T200 is greatly indented to the right of the upper left boundary of the concave cavity F100, thereby reducing the area of the effective diaphragm area of the second sandwich structure.

[0070] The upper surface of the first bottom electrode B100 near the left edge is exposed to the bottom of the through hole of the filling layer F200 and the second piezoelectric layer P200, the upper surface of the first top electrode T100 near the left edge is exposed to the bottom of the through hole of the filling layer F200 and the second piezoelectric layer P200, and the upper surface of the second bottom electrode B200 near the left edge is exposed to the bottom of the through hole of the second piezoelectric layer P200.

[0071] The first metal layer M100 covers at least part of the surface of the first piezoelectric layer P100 exposed to the bottom of the corresponding through hole, the side wall of the corresponding through hole, and part of the upper surface of the second piezoelectric layer P200 located to the left of the second top electrode T200; the second metal layer M110 covers at least part of the surface of the first top electrode T100 exposed to the bottom of the corresponding through hole, the side wall of the corresponding through hole, and part of the upper surface of the second piezoelectric layer P200 located to the left of the second top electrode T200; the third metal layer M120 covers at least part of the surface of the second bottom electrode B200 exposed to the bottom of the corresponding through hole, the side wall of the corresponding through hole, and part of the upper surface of the second piezoelectric layer P200 located to the left of the second top electrode T200.

[0072] The first bottom electrode B100 of the first sandwich structure is electrically led out through the metal layer M100 in the via hole of the filling layer F200 and the second piezoelectric layer P200; the first top electrode T100 of the first sandwich structure is electrically led out through the metal layer M110 in the via hole of the filling layer F200 and the second piezoelectric layer P200; and the second bottom electrode B200 of the second sandwich piezoelectric unit is electrically led out through the metal layer M120 in the via hole of the second piezoelectric layer P200.

[0073] The fourth preferred embodiment of the present application is a slits-free type MEMS ultrasonic transducer with double piezoelectric materials, in a top view Figure 7 The cross section along the direction of OB is the structure without the electrically connected terminal part, as shown in Figure 9 .

[0074] The left edge of the second bottom electrode B200 of the second sandwich structure is in a substantially aligned state with the left edge of the first bottom electrode B100 of the first sandwich structure located below it, without a significant feature of being indented to the right side.

[0075] Since Figure 7 the cross section line OB does not pass through the extended end of the first top electrode T100, the left edge of the first top electrode T100 in Figure 9 is also greatly indented to the right side of the left upper edge of the concave cavity, thereby reducing the effective acoustic area of the first sandwich structure.

[0076] The fifth preferred embodiment of the present application is the slits-free type piezoelectric micro-electro-mechanical system ultrasonic transducer, the first sandwich structure of the ultrasonic transducer comprises an AlN layer, and the second sandwich structure comprises a PZT layer, as shown in Figure 10 and Figure 11 .

[0077] The fifth preferred embodiment of the slits-free type piezoelectric micro-electro-mechanical system ultrasonic transducer of the present application, in a top view Figure 7 The cross section along the direction of OA is the structure with the electrically connected terminal part, as shown in Figure 10The cross-sectional view also shows that the second top electrode T200 is located right below the portion of the second top electrode T200 on the right side of the central axis oo'. The piezoelectric micro-electro-mechanical system ultrasonic transducer has a substrate S100, a concave cavity F100 is formed on the upper surface of the substrate S100, and a through-type opening is formed within the lower bottom boundary of the concave cavity F100. The upper surface of the concave cavity F100 and the surface around the cavity of the substrate S100 are covered with a first bottom electrode B100 of a first sandwich structure, wherein the first bottom electrode B100 is composed of multiple layers of materials, and the materials are arranged in the order from bottom to top as aluminum nitride, molybdenum, wherein the aluminum nitride serves as a seed layer. The left edge of the first bottom electrode B100 is recessed to the right relative to the left edge of the substrate S100. The surface of the substrate S100 is covered with a first piezoelectric layer P100 of a first sandwich structure, and the material of the first piezoelectric layer P100 is AlN, which includes aluminum nitride, doped aluminum nitride, etc. The left edge of the first piezoelectric layer P100 extends to the left edge of the substrate S100. The surface of the first piezoelectric layer P100 is covered with a first top electrode layer T100 of a first sandwich structure, and the metal material of the first top electrode T100 includes but is not limited to molybdenum, platinum, magnesium, aluminum, ruthenium, titanium, iridium, osmium, silver, gold, titanium, tungsten, copper, chromium, etc., as well as alloys or composite layers of the metals. The left edge of the first top electrode layer is recessed to the right relative to the left edge of the first bottom electrode B100, thereby exposing a portion of the first bottom electrode B100 to the left side of the first top electrode T100.

[0078] The filling layer F200 covers the upper surface and side surface of the first top electrode T100 and part of the upper surface of the first piezoelectric layer P100, and the left edge of the filling layer F200 extends to the left edge of the substrate S100.

[0079] The upper surface of the filling layer F200 is planarized, and a second bottom electrode B200 of a second sandwich structure is covered on the upper surface. The second bottom electrode B200 is composed of multiple material layers, and the materials are arranged in the order from bottom to top as zirconium oxide, platinum, SRO or titanium, platinum, and a buffer layer, in which the zirconium oxide or titanium serves as a seed layer. The left edge of the second bottom electrode B200 is indented to the right relative to the left edge of the first top electrode T100. Because the upper surface of the filling layer F200 is planar, any layer of the second sandwich structure is also planar and does not bend, so that the reliability of the second sandwich structure can be ensured. If there is no filling layer F200, the unevenness of the surface of the first sandwich structure will be transmitted to the second sandwich structure, resulting in a decrease in the reliability of the second sandwich structure. If the surface of the filling layer F200 is uneven, the unevenness of the surface of the first sandwich structure will also be transmitted to the second sandwich structure, resulting in a decrease in the reliability of the second sandwich structure. A second piezoelectric layer P200 of the second sandwich structure is covered on the surface of the second bottom electrode B200 and part of the surface of the filling layer F200. The material of the second piezoelectric layer P200 is PZT, which includes lead zirconate titanate, doped lead zirconate titanate, etc. The left edge of the second piezoelectric layer P200 is aligned with the left edge of the second bottom electrode B200. A second top electrode T200 of the second sandwich structure is covered on the surface of the second piezoelectric layer P200. The metal material of the second top electrode T200 includes but is not limited to molybdenum, platinum, magnesium, aluminum, ruthenium, titanium, iridium, osmium, silver, gold, titanium, tungsten, copper, chromium, etc., as well as alloys or composite layers of the metals. The left edge of the second top electrode T200 is indented to the right relative to the left edge of the second bottom electrode B200.

[0080] The upper surface of the first bottom electrode B100 near the left edge is exposed to the bottom of the through hole of the first piezoelectric layer P100 and the filling layer F200. The upper surface of the first top electrode T100 near the left edge is exposed to the bottom of the through hole of the first piezoelectric layer P100 and the filling layer F200. The upper surface of the second piezoelectric layer P200 near the left edge is exposed to the bottom of the through hole of the second piezoelectric layer P200.

[0081] The first metal layer M100 covers at least part of the surface of the first piezoelectric layer P100 exposed to the bottom of the corresponding through hole, and covers the sidewall of the corresponding through hole. The second metal layer M110 covers at least part of the surface of the first top electrode T100 exposed to the bottom of the corresponding through hole, covers the sidewall of the corresponding through hole, and covers part of the upper surface of the second piezoelectric layer P200 located to the left of the second top electrode T200. The third metal layer M120 covers at least part of the surface of the second bottom electrode B200 exposed to the bottom of the corresponding through hole, covers the sidewall of the corresponding through hole, and covers part of the upper surface of the second piezoelectric layer P200 located to the left of the second top electrode T200.

[0082] The filling layer F200 covers the upper surface and side surface of the first top electrode T100 and part of the upper surface of the first piezoelectric layer P100.

[0083] The first bottom electrode B100 of the first sandwich structure is electrically led out through the metal layer M100 in the through hole of the filling layer F200; the first top electrode T100 of the first sandwich structure is electrically led out through the metal layer M110 in the through hole of the filling layer F200; the second bottom electrode B200 of the second sandwich piezoelectric unit is electrically led out through the metal layer M120 in the through hole of the second piezoelectric layer P200.

[0084] In the top view Figure 7 The cross section along the direction of OB is the structure of the non-electrically connected terminal part, as shown in Figure 11 The top view Figure 2 of the second preferred embodiment is different from that of the first preferred embodiment in that: Figure 4 Since there is no through hole type electrically connected structure in Figure 11 as in Figure 10 , the left edge of the second bottom electrode B200 of the second sandwich structure is in a state of substantial alignment with respect to the left edge of the first bottom electrode B100 of the first sandwich structure located thereunder, without the feature of significant indentation to the right side.

[0085] Since the cross section line OB in Figure 7 does not pass through the extended end of the first top electrode T100, the left edge of the first top electrode T100 in Figure 11 is also substantially indented to the right side of the left upper edge of the concave cavity, thereby reducing the effective acoustic area of the first sandwich structure.

[0086] The material of the filling layer F200 can be selected from silicon, polysilicon, polymer, amorphous silicon, silicon dioxide, silicon nitride, silicon carbide, and aluminum nitride, etc. The upper surface of the filling layer F200 is a plane parallel to the surface of the substrate S100.

[0087] The manufacturing method of the MEMS ultrasonic transducer of the double piezoelectric material of the present application comprises the following steps: Step one, processing a concave cavity on a substrate, covering the concave cavity of the substrate by a sacrificial layer; Step two, depositing a first sandwich structure on the surface of the substrate and the surface of the sacrificial layer in sequence; Step three, covering the surface of the substrate and the first sandwich structure with a filling layer material; Step four, forming a second sandwich structure on the surface of the filling layer; ​The first piezoelectric layer of the first sandwich structure is an AlN layer, and the second piezoelectric layer of the second sandwich structure is a PZT layer; or the first piezoelectric layer of the first sandwich structure is a PZT layer, and the second piezoelectric layer of the second sandwich structure is an AlN layer.

[0088] The manufacturing method of the MEMS ultrasonic transducer of the double piezoelectric material is described in detail taking the MEMS ultrasonic transducer of the double piezoelectric material with a slit as an example.

[0089] The first preferred embodiment of the manufacturing method of the MEMS ultrasonic transducer of the double piezoelectric material takes the first sandwich structure including a PZT layer and the second sandwich structure including an AlN layer as an example, that is, takes the case that the first sandwich structure including a PZT layer is located below the second sandwich structure including an AlN layer as an example, and can include the following steps: Step 101, a concave cavity is processed on the substrate S100, wherein the material of the substrate S100 includes monocrystalline silicon or the like, as shown in Figure 12 .

[0090] Step 102, the concave cavity of the substrate S100 is covered by a sacrificial layer F100, as shown in Figure 13 , and the sacrificial layer F100 is filled in the cavity only through a grinding process or the like, and the upper surface of the sacrificial layer F100 is basically flush with the surface of the substrate S100 located at the periphery of the concave cavity.

[0091] Step 103, a first bottom electrode B100, a first piezoelectric layer P100 and a first top electrode T100 are sequentially deposited on the surface of the substrate S100 and the surface of the sacrificial layer F100, so as to form a first sandwich structure, as shown in Figure 14 . The first bottom electrode B100 has a composite material layer structure, and the material layers from bottom to top are zirconium oxide, platinum, SRO or titanium, platinum, a buffer layer, wherein the zirconium oxide or titanium acts as a seed layer. The first piezoelectric layer P100 is a PZT layer, and the PZT is lead zirconate titanate or doped lead zirconate titanate or the like. The metal material of the first top electrode T100 can be selected from but not limited to molybdenum, platinum, magnesium, aluminum, ruthenium, titanium, iridium, osmium, silver, gold, titanium, tungsten, copper, chromium and alloys or composite layers of the metals.

[0092] Step 104, the left edge of the first sandwich structure is indented to the right relative to the left edge of the substrate S100 through a patterning and etching process, as shown in Figure 15 , and the right edge of the first sandwich structure forms a slit near the central area. The edge of the first sandwich structure has a certain inclination angle, and the size of the inclination angle will change according to different etching process conditions.

[0093] Step 105, further shrink the left side edge of the first piezoelectric layer P100 and the first top electrode T100 relative to the left side edge of the first bottom electrode B100 by a patterning and etching process, to form a step-like structure, thereby exposing part of the upper surface of the first bottom electrode B100 to the left of the left side edge of the first piezoelectric layer P100 and the first top electrode T100, as shown in Figure 16 .

[0094] The present application is to form a slit near the center region of the right side edge of the first sandwich structure by a patterning and etching process.

[0095] Step 106, cover the surface of part of the substrate S100, part of the surface and side of the first bottom electrode B100, the surface of the first top electrode T100, the side of the first top electrode T100 and the first piezoelectric layer P100, and the surface of the sacrificial layer F100 exposed in the slit with the filling layer F200 material by a deposition process. Flatten the upper surface of the filling layer F200 by a flattening process such as grinding, as shown in Figure 17 .

[0096] Step 107, form the second bottom electrode B200 of the second sandwich structure on the surface of the filling layer F200 by a deposition and patterning process, shrink the left side edge of the first bottom electrode B100 relative to the left side edge of the first top electrode T100 to the right, shrink the right side edge of the first top electrode T100 relative to the edge of the filling layer F200 to the left, and align the right side edge of the first bottom electrode B100 with the right side edge of the first sandwich structure, as shown in Figure 18 . The second bottom electrode B200 is composed of multiple material layers, and the materials are arranged in the order from bottom to top as aluminum nitride, molybdenum, wherein the aluminum nitride serves as a seed layer.

[0097] Step 108, form the second piezoelectric layer P200 on the surface and side of the second bottom electrode B200 and the surface of the filling layer F200 exposed to both sides of the second bottom electrode B200 by a deposition process, as shown in Figure 19 .

[0098] Step 109, form the second top electrode T200 of the second sandwich structure on the surface of the second piezoelectric layer P200 by a deposition and patterning process, wherein the left side boundary of the second top electrode T200 is shrunk to the right relative to the left side boundary of the second bottom electrode B200, and the right side boundary is basically aligned with the right side boundary of the lower layer electrodes, or is slightly shrunk to the left relative to the right side boundary of the second bottom electrode B200, as shown in Figure 20 .

[0099] Step 110: Through holes are formed in the second piezoelectric layer P200 by patterning and etching processes, wherein the first through hole C100, the second through hole C110, and the third through hole C120 are located on the left side of the second top electrode T200, and are respectively located above the first bottom electrode B100, the first top electrode T100, and the second bottom electrode B200, and a portion of the surface of the second bottom electrode B200 is exposed at the bottom of the third through hole C120; the slit R100 formed together with the through hole by the process is as follows: Figure 21 shown.

[0100] Step 111: Continue to make through holes in the filling layer F200 through patterning and etching processes, such as Figure 22 As shown, the first through hole C100 and the second through hole C110 are further deepened to form the deepened first deep through hole C101 and the second deep through hole C111, thereby exposing portions of the surfaces of the first bottom electrode B100 and the first top electrode T100 at the bottoms of the first deep through hole C101 and the second deep through hole C111, respectively. Simultaneously, a portion of the filling layer F200 on the right side is further etched away using a patterning and etching process to form a slit R101.

[0101] Step 112: A first metal layer M100, a second metal layer M110, and a third metal layer M120 are formed by deposition, patterning, and etching processes. The first metal layer M100 covers the bottom of the first bottom electrode B100, the second metal layer M110 covers the top of the first top electrode T100, and the third metal layer M120 covers the top of the second bottom electrode B200, the sidewalls of the corresponding through holes, and the partial surface of the second piezoelectric layer P200 located around each through hole, thereby achieving electrical connection and extraction of the first bottom electrode B100, the first top electrode T100, and the second bottom electrode B200, as shown in FIG. Figure 23 shown.

[0102] The present invention forms a slit near the center area on the right edge of the second sandwich structure through patterning and etching processes.

[0103] Step 113: forming a protective layer E100 on the upper surface of the second sandwich structure and the slit by deposition and grinding processes, such as Figure 24 As shown; Step 114: Figure 24 The structure shown is turned over, and a through-type opening D100 is formed on the back side of the substrate S100 by patterning and deep etching processes, so that the boundary of the through-type opening D100 is located inside the boundary of the lower surface of the cavity, as shown in FIG. Figure 25 shown.

[0104] Step 115: Remove the protective layer E100 and the sacrificial layer F100 through etching and releasing process. Figure 25the structure is flipped, as shown in Figure 26 to form a double-sided driven piezoelectric micro-electro-mechanical system loudspeaker, as shown in Figure 2 、 Figure 3 、 Figure 4 .

[0105] The second preferred embodiment of the method for manufacturing the MEMS ultrasonic transducer of the double piezoelectric material of the present application takes the first sandwich structure including the AlN layer and the second sandwich structure including the PZT layer as an example, that is, takes the case where the first sandwich structure including the AlN layer is located below the second sandwich structure including the PZT layer as an example, and can include the following steps: Step 201, processing a concave cavity in the substrate S100, wherein the material of the substrate S100 can be selected but is not limited to single crystal silicon and the like, as shown in Figure 27 .

[0106] Step 202, covering the surface of the substrate S100 and the concave cavity with the sacrificial layer F100, and filling the sacrificial layer F100 only in the cavity and making the upper surface of the sacrificial layer F100 substantially flush with the surface of S100 located at the periphery of the concave cavity by grinding and other processes, as shown in Figure 28 .

[0107] Step 203, forming the first bottom electrode B100 of the first sandwich structure on the surface of the substrate S100 and the sacrificial layer F100 by deposition and patterning processes, so that the left edge of the first bottom electrode B100 is recessed to the right relative to the left edge of the substrate S100, and the right edge of the first bottom electrode B100 is recessed to the left relative to the right edge of the sacrificial layer F100, as shown in Figure 29 . The first bottom electrode B100 is composed of multiple material layers, and the materials are arranged in the order from bottom to top as aluminum nitride, molybdenum, wherein the aluminum nitride serves as a seed layer.

[0108] Step 204, covering the first piezoelectric layer P100 on the surface and side surface of the first bottom electrode B100 and the surface of the substrate S100 and the sacrificial layer F100 exposed to both sides of the first bottom electrode B100 by deposition process, wherein the first piezoelectric layer P100 is an aluminum nitride piezoelectric film, as shown in Figure 30 .

[0109] Step 205, a first top electrode T100 of a first sandwich structure is formed on the surface of the first piezoelectric layer P10 by deposition and patterning process. The metal material of the first top electrode T100 includes molybdenum, platinum, magnesium, aluminum, ruthenium, titanium, iridium, osmium, silver, gold, titanium, tungsten, copper, chromium, etc. and alloys or composite layers of the metals. The left side boundary of the first top electrode T100 is indented to the right relative to the left side boundary of the first bottom electrode B100, and the right side boundary of the first top electrode T100 is substantially aligned with the right side boundary of the first bottom electrode B100, or is slightly indented to the left relative to the right side boundary of the first bottom electrode B100, as shown in Figure 31 .

[0110] Step 206, a filling layer F200 is formed on the upper surface and side surface of the first top electrode T100 and the surface of the first piezoelectric layer P100 exposed outside the two side edges of the first bottom electrode B100 by deposition process. That is, the filling layer F200 covers the continuous upper surface of the first piezoelectric layer P100 and the first top electrode T100. The upper surface of the filling layer F200 is planarized by polishing or other planarization process, as shown in Figure 32 .

[0111] Step 207, a second bottom electrode B200, a second piezoelectric layer P200 and a second top electrode T200 are sequentially deposited on the surface of the filling layer F200 to form a second sandwich structure. The second bottom electrode B200 has a composite material layer structure, and the material layers from bottom to top are zirconium oxide, platinum, SRO or titanium, platinum, a buffer layer, in which zirconium oxide or titanium acts as a seed layer. The material of the second piezoelectric layer P200 is PZT, which includes lead zirconate titanate or doped lead zirconate titanate, etc. The metal material of the second top electrode T200 includes molybdenum, platinum, magnesium, aluminum, ruthenium, titanium, iridium, osmium, silver, gold, titanium, tungsten, copper, chromium, etc. and alloys or composite layers of the metals, as shown in Figure 33 .

[0112] Step 208, the left edge of the second sandwich structure is indented to the right relative to the left edge of the filling layer F200, and the right edge of the second sandwich structure is indented to the left relative to the right edge of the filling layer F200 and forms a slit by patterning and etching process. The left edge of the second sandwich structure is indented to the right relative to the left edge of the first top electrode T100, and the right edge of the second sandwich structure is substantially aligned with the right edges of the first bottom electrode B100 and the first top electrode T100, as shown in Figure 34 .

[0113] Step 209, the left edge of the second top electrode T200 of the second sandwich structure is further indented to the right relative to the left edge of the second piezoelectric layer P200 below it by patterning and etching process, but it is still ensured that the edge is still located on the left side of the upper edge of the cavity in the substrate S100 after indentation, as shown inFigure 35 As shown.

[0114] Step 210, a third through-hole C220 is made in the second piezoelectric layer P200 exposed to the left edge of the second top electrode T200 by a patterning and etching process, ensuring that part of the upper surface of the second bottom electrode B200 is exposed to the bottom of the third through-hole, as shown. Figure 36

[0115] Step 211, a first through-hole C200 and a second through-hole C210 are made in the filling layer F200 by a patterning and etching process, the first through-hole C200 and the second through-hole C210 are located on the left side of the second bottom electrode B200, the first through-hole C200 is located above the first bottom electrode B100, the second through-hole C210 is located above the first top electrode T100, part of the surface of the first top electrode T100 is exposed to the bottom of the second through-hole C210; the slit R200 is a structure formed by the process together with the through-hole, as shown. Figure 37

[0116] Step 212, continue to make through-holes in the first piezoelectric layer P100 by a patterning and etching process, further form a second deep through-hole C201 based on the second through-hole C200, so that part of the surface of the first bottom electrode B100 is exposed to the bottom of the first through-hole C201 respectively; at the same time, further etch the part of the first piezoelectric layer P100 located on the right side by this step process to form a slit R201, as shown. Figure 38

[0117] Step 213, a first metal layer M100, a second metal layer M110 and a third metal layer M120 are made by a deposition, patterning and etching process. The first metal layer M100 covers at least part of the surface of the first bottom electrode B100 exposed to the bottom of the corresponding through-hole, the first metal layer M100 covers the sidewall of the corresponding through-hole, and the upper surface of the part of the filling layer F200 located on the left side of the second top electrode T200; the second metal layer M110 covers at least part of the surface of the first top electrode T100 exposed to the bottom of the corresponding through-hole, the second metal layer M110 covers the sidewall of the corresponding through-hole, and the upper surface of the part of the filling layer F200 located on the left side of the second top electrode T200; the third metal layer M120 covers at least part of the surface of the second bottom electrode B200 exposed to the bottom of the corresponding through-hole, the third metal layer M120 covers the sidewall of the corresponding through-hole, and the upper surface of the part of the second piezoelectric layer P200 located on the left side of the second top electrode T200.

[0118] ​​​The first bottom electrode B100 of the first sandwich structure is electrically led out through the metal layer M100 in the through hole of the filling layer F200; the first top electrode T100 of the first sandwich structure is electrically led out through the metal layer M110 in the through hole of the filling layer F200; the second bottom electrode B200 of the second sandwich piezoelectric unit is electrically led out through the metal layer M120 in the through hole of the second piezoelectric layer P200. Figure 39

[0119] Step 214: a protective layer E100 is formed on the continuous surface composed of the first piezoelectric layer, the left side end of the second sandwich structure, the upper surface of the second sandwich structure, and the right side end of the second sandwich structure through deposition and grinding processes, as shown in Figure 40

[0120] Step 215: the above MEMS ultrasonic transducer structure of the double piezoelectric material is flipped, a through opening D100 is made on the back of the substrate S100 through a patterning and deep etching process, and the boundary of the through opening D100 is located inside the boundary of the lower surface of the cavity, as shown in Figure 41

[0121] Step 216: the protective layer E100 and the sacrificial layer F100 are removed through an etching and releasing process, the flipped structure of the ultrasonic transducer structure is flipped, and a double-sided driven piezoelectric micro-electro-mechanical system loudspeaker of the application is formed, as shown in Figure 42

[0122] The application also includes an electronic device comprising the technical features in any of the above embodiments of the MEMS ultrasonic transducer of the double piezoelectric material, as shown in Figure 43 The electronic device can include a processor 1002, a communications interface 1004, a memory 1006, and a communications bus 1008.

[0123] The processor 1002, the communications interface 1004, and the memory 1006 can communicate with each other through the communications bus 1008.

[0124] The communications interface 1004 is used to communicate with network elements of other devices such as clients or other servers.

[0125] The processor 1002 is used to execute the program 1010, and specifically, the program 1010 can include program code including computer operation instructions.

[0126] ​​​​The processor 1002 can be a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to perform the operations of an embodiment of the application. The terminal can include one or more processors of the same type, such as one or more CPUs; or different types, such as one or more CPUs and one or more ASICs.

[0127] The memory 1006 stores the program 1010. The memory 1006 can include a high-speed RAM memory, and can also include a non-volatile memory, such as at least one disk memory.

[0128] The piezoelectric microelectromechanical system (MEMS) of the bimorph piezoelectric material is the preferred embodiment of the piezoelectric microelectromechanical system (MEMS) ultrasonic transducer of any bimorph piezoelectric material in the embodiments of the present specification.

[0129] The above is a description of the preferred embodiments of the present application, which can help those skilled in the art to more fully understand the technical solutions of the present application. However, these embodiments are only illustrative and cannot be construed as limiting the specific embodiments of the present application to these illustrative embodiments. For those skilled in the art to which the present application belongs, without departing from the concept of the present application, a number of simple deductions and transformations can be made, which should be regarded as falling within the scope of protection of the present application.

Claims

1. MEMS ultrasonic transducer of bimorph piezoelectric material, comprising a substrate with a concave cavity and a diaphragm, characterized in that, The diaphragm comprises: a first sandwich structure with a first piezoelectric layer arranged on the substrate, a filling layer arranged on the first sandwich structure, and a second sandwich structure with a second piezoelectric layer arranged on the filling layer. The first piezoelectric layer of the first sandwich structure is an AlN layer, and the second piezoelectric layer of the second sandwich structure is a PZT layer; or the first piezoelectric layer of the first sandwich structure is a PZT layer, and the second piezoelectric layer of the second sandwich structure is an AlN layer.

2. The dual piezoelectric material MEMS ultrasonic transducer of claim 1, wherein, A thickness ratio T1 is defined as a value of a PZT layer thickness ratio to an AlN layer thickness, a thickness ratio T2 is defined as a value of a filling layer thickness ratio to a PZT layer thickness, and a normalized sensitivity product is obtained by extracting a product of the transmitting sensitivity and the receiving sensitivity and performing a normalization operation.

3. The dual piezoelectric material MEMS ultrasonic transducer of claim 2, wherein, When the thickness ratio T2 is constant, the thickness ratio T1 ranges from not less than 50% of a maximum sensitivity product at the thickness ratio T2.

4. The MEMS ultrasonic transducer of claim 3, wherein, when 0≤T2<0.2, the thickness ratio T1 ranges from not less than 1 to not more than 15; when 0.2≤T2<0.5, the thickness ratio T1 ranges from not less than 0.8 to not more than 15; when 0.5≤T2<0.7, the thickness ratio T1 ranges from not less than 0.6 to not more than 15.

5. The dual piezoelectric material MEMS ultrasonic transducer of claim 2, wherein, When the thickness ratio T2 is constant, the thickness ratio T1 ranges from not less than 80% of a maximum sensitivity product at the T2.

6. The MEMS ultrasonic transducer of claim 5, wherein, when 0≤T2<0.2, the thickness ratio T1 ranges from not less than 1.5 to not more than 5; when 0.2≤T2<0.5, the thickness ratio T1 ranges from not less than 1.25 to not more than 5; when 0.5≤T2<0.7, the thickness ratio T1 ranges from not less than 1 to not more than 5; when 0.7≤T2<1, the thickness ratio T1 ranges from not less than 0.8 to not more than 5.

7. The dual piezoelectric material MEMS ultrasonic transducer of claim 2, wherein, The thickness ratio T1 ranges from not less than 95% of a maximum sensitivity product, and the thickness ratio T1 ranges from not less than 2 to not more than 3.

8. The dual piezoelectric material MEMS ultrasonic transducer of claim 1, wherein, The first sandwich structure has a step-shaped structure, and the step-shaped structure has steps that are sequentially higher in a direction from the substrate upward.

9. The bimorph MEMS ultrasonic transducer of claim 8, wherein, The step-shaped structure comprises a first step and a second step from the substrate upward, the first step has a height lower than the second step, and the first step corresponds to an upper surface and a side surface of the first bottom electrode, and the second step corresponds to a side surface of the first piezoelectric layer and an upper surface and a side surface of the first top electrode.

10. The dual piezoelectric material MEMS ultrasonic transducer of claim 8, wherein, The filling layer covers a continuous surface of the step-shaped structure of the first sandwich structure and an upper surface of the substrate.

11. The dual piezoelectric material MEMS ultrasonic transducer of claim 1, wherein, An upper surface of the filling layer is flat, and the upper surface of the filling layer is covered with the second sandwich structure.

12. The dual piezoelectric material MEMS ultrasonic transducer of claim 1, wherein, A lower bottom of the concave cavity is provided with a through-type opening.

13. The dual piezoelectric material MEMS ultrasonic transducer of claim 1, wherein, The piezoelectric thin film material of the PZT layer is PZT, and the PZT is lead zirconate titanate or doped lead zirconate titanate; and the piezoelectric thin film material of the AlN layer is AlN, and the AlN is aluminum nitride or doped aluminum nitride.

14. The dual piezoelectric material MEMS ultrasonic transducer of claim 1, wherein, The first sandwich structure, from the substrate upwards, comprises a first bottom electrode, a first piezoelectric layer, and a first top electrode; the second sandwich structure, from the filling layer upwards, comprises a second bottom electrode, a second piezoelectric layer, and a second top electrode.

15. The bimorph MEMS ultrasonic transducer of claim 14, wherein, When the piezoelectric layer is a PZT layer, the first bottom electrode of the first sandwich structure or the second bottom electrode of the second sandwich structure is composed of multiple material layers, and the materials are arranged in the order from bottom to top as zirconium oxide, platinum, SRO or titanium, platinum, and a buffer layer, wherein the zirconium oxide or titanium serves as a seed layer.

16. The bimorph MEMS ultrasonic transducer of claim 14, wherein, When the piezoelectric layer is an AlN layer, the first bottom electrode of the first sandwich structure or the second bottom electrode of the second sandwich structure is composed of multiple material layers, and the material layers are arranged in the order from bottom to top as aluminum nitride and molybdenum, wherein the aluminum nitride serves as a seed layer.

17. The bimorph MEMS ultrasonic transducer of claim 14, wherein, The material of the first top electrode of the first sandwich structure or the second top electrode of the second sandwich structure comprises metal materials such as molybdenum, platinum, magnesium, aluminum, ruthenium, titanium, iridium, osmium, silver, gold, titanium, tungsten, copper, and chromium, and alloys or composite layers of the metals.

18. The dual piezoelectric material MEMS ultrasonic transducer of claim 14, wherein, The diaphragm is in the shape of a square in plan view, and the diaphragm is divided into four triangular diaphragms by a cross-shaped slit; or the diaphragm is in the shape of a circle in plan view, and the second top electrode and the first top electrode of the diaphragm are in the shape of a circle, and the area of the second top electrode is smaller than that of the first top electrode.

19. The bimorph MEMS ultrasonic transducer of claim 18, wherein, The left edge of the filling layer extends to align with the left edge of the substrate, and the right edge of the filling layer participates in forming the slit near the central axis.

20. The dual piezoelectric material MEMS ultrasonic transducer of claim 1, wherein, The material of the filling layer comprises silicon, polysilicon, polymer, amorphous silicon, silicon dioxide, silicon nitride, silicon carbide, and aluminum nitride.

21. The dual piezoelectric material MEMS ultrasonic transducer of claim 1, wherein, The filling layer completely covers the epitaxial end surface of the first sandwich structure of the diaphragm.

22. A method for manufacturing a MEMS ultrasonic transducer of double piezoelectric materials, comprising the following steps: Step one: processing a concave cavity on a substrate, covering the concave cavity of the substrate by a sacrificial layer; Step two: sequentially depositing a first sandwich structure on the surface of the substrate and the surface of the sacrificial layer; Step three: covering the surface of the substrate and the first sandwich structure with a filling layer material; Step four: forming a second sandwich structure on the surface of the filling layer; The first piezoelectric layer of the first sandwich structure is an AlN layer, and the second piezoelectric layer of the second sandwich structure is a PZT layer; or the first piezoelectric layer of the first sandwich structure is a PZT layer, and the second piezoelectric layer of the second sandwich structure is an AlN layer.

23. A method of manufacturing a dual piezoelectric material MEMS ultrasonic transducer according to claim 22, wherein, The first sandwich structure in step three comprises a first bottom electrode, a first piezoelectric layer, and a first top electrode deposited in sequence.

24. The method of fabricating a dual piezoelectric material MEMS ultrasonic transducer of claim 22, wherein, The step three further comprises the following steps: forming a slit near the central region by a patterning and etching process on the right edge of the first sandwich structure.

25. A method of manufacturing a dual piezoelectric material MEMS ultrasonic transducer according to claim 24, wherein, The step three further comprises the following steps: The left edge of the first piezoelectric layer and the first top electrode is recessed to the right relative to the left edge of the first bottom electrode to form a stepped structure by a patterning and etching process.

26. The method of fabricating a dual piezoelectric material MEMS ultrasonic transducer of claim 22, wherein, The fourth step includes forming a slit on the right edge of the second sandwich structure near the center region by a patterning and etching process; and forming a protective layer on the upper surface of the second sandwich structure and the slit by a deposition and grinding process.

27. The method of fabricating a dual piezoelectric material MEMS ultrasonic transducer of claim 22, wherein, The fourth step further includes, after the piezoelectric micro-electro-mechanical system ultrasonic transducer is flipped upside down, making a through-type opening on the back of the substrate by a patterning and deep etching process, so that the boundary of the through-type opening is located inside the lower surface boundary of the cavity.

28. A method of manufacturing a dual piezoelectric material MEMS ultrasonic transducer according to claim 27, wherein, The fourth step further includes removing the protective layer and the sacrificial layer by an etching and releasing process.

29. The method of fabricating a dual piezoelectric material MEMS ultrasonic transducer of claim 22, wherein, The fourth step further includes planarizing the upper surface of the filling layer.

30. An electronic device, comprising: A processor, a memory, a communication interface and a communication bus, the processor, the memory and the communication interface complete communication with each other through the communication bus, and the processor is connected with the dual piezoelectric material MEMS ultrasonic transducer in any one of claims 1-21.

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