MEMS ultrasonic transducer

Abstract

The MEMS ultrasonic transducer comprises a substrate, a vibrating diaphragm, a bottom electrode layer, a piezoelectric layer and a top electrode layer, the substrate comprises a through hole and a supporting area; the vertical projection of the vibrating diaphragm on the substrate covers the through hole and part of the supporting area; the bottom electrode layer comprises an inner-ring bottom electrode and an outer-ring bottom electrode, the piezoelectric layer comprises an inner-ring piezoelectric layer and an outer-ring piezoelectric layer, all the layers are stacked in sequence, and the bottom electrode layer and the outer-ring part of the piezoelectric layer surround the inner-ring part and cover part of the through hole and the supporting area of the substrate. The top electrode layer comprises an inner-ring top electrode and an outer-ring top electrode, and a gap is formed between the inner-ring top electrode and the outer-ring top electrode; the outer-ring top electrode surrounds the inner-ring top electrode, the vertical projection of the inner-ring top electrode on the piezoelectric layer is located in the inner-ring piezoelectric layer, and the vertical projection of the outer-ring top electrode on the piezoelectric layer is located in the outer-ring piezoelectric layer; the outer ring top electrode is electrically connected with the inner ring bottom electrode, and the outer ring bottom electrode is electrically connected with the inner ring top electrode. The process difficulty and the production cost can be reduced, and the performance of the transducer is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to micro -electromechanical system technical field especially, a kind of MEMS ultrasonic transducer. BACKGROUND

[0002] Piezoelectric Micromachined Ultrasonic Transducer (pMUT) based on Micro-Electro-Mechanical System (MEMS) technology is an important device, which can be applied in robot obstacle avoidance, ultrasonic gesture recognition, ultrasonic under-screen fingerprint recognition, ultrasonic imaging and other application fields.

[0003] In order to expand the application range, pMUT device needs better performance, that is, it can have greater transmitting / receiving sensitivity when the same signal. At present, optimization can be carried out by optimizing the upper electrode coverage area (usually about 60% of the total size of the diaphragm, which can be optimized by simulation), etching Lead Zirconate Titanate (PZT) to release stress, using differential electrode and other ways, and optimization can also be carried out by combining various ways, but it will increase the process flow and the complexity of the back-end application system. Therefore, a pMUT device with the same application difficulty as the current device, controllable process difficulty and cost, and better performance needs to be developed. SUMMARY

[0004] The utility model provides a kind of MEMS ultrasonic transducer, can improve the performance of transducer while guaranteeing that transducer has lower manufacturing process difficulty and production cost.

[0005] According to an aspect of the utility model, a kind of MEMS ultrasonic transducer is provided, comprising:

[0006] Base, and diaphragm, bottom electrode layer, piezoelectric layer and top electrode layer sequentially laminated and set on one side of base;Diaphragm is set on the side of bottom electrode layer adjacent to base;

[0007] Base includes through hole and support area around through hole;

[0008] Diaphragm covers through hole and at least part of support area in the vertical projection of base;

[0009] Bottom electrode layer includes inner ring bottom electrode and outer ring bottom electrode, and there is gap between inner ring bottom electrode and outer ring bottom electrode, and outer ring bottom electrode surrounds inner ring bottom electrode;Inner ring bottom electrode is located in through hole in the vertical projection of base, and outer ring bottom electrode covers part of through hole and at least part of support area in the vertical projection of base;

[0010] The piezoelectric layer comprises an inner piezoelectric layer and an outer piezoelectric layer, and a gap is formed between the inner piezoelectric layer and the outer piezoelectric layer, and the outer piezoelectric layer surrounds the inner piezoelectric layer; a vertical projection of the inner piezoelectric layer on the bottom electrode layer is located in the inner bottom electrode, and a vertical projection of the outer piezoelectric layer on the substrate covers part of the through hole and at least part of the support area;

[0011] The top electrode layer comprises an inner top electrode and an outer top electrode, and a gap is formed between the inner top electrode and the outer top electrode; the outer top electrode surrounds the inner top electrode, a vertical projection of the inner top electrode on the piezoelectric layer is located in the inner piezoelectric layer, and a vertical projection of the outer top electrode on the piezoelectric layer is located in the outer piezoelectric layer;

[0012] The outer top electrode and the inner bottom electrode are electrically connected, and the outer bottom electrode and the inner top electrode are electrically connected.

[0013] Optionally, the MEMS ultrasonic transducer further comprises:

[0014] An insulating layer, the insulating layer covering at least part of the gap between the inner bottom electrode and the outer bottom electrode, and at least part of the gap between the inner piezoelectric layer and the outer piezoelectric layer.

[0015] Optionally, the outer top electrode further has an opening, the opening penetrating the outer top electrode in a direction in which the outer top electrode points to the inner top electrode, and the insulating layer further covers the piezoelectric layer at the opening;

[0016] The insulating layer at the opening is provided with a first signal line and a second signal line away from the surface of the substrate; a first end of the first signal line is electrically connected with the inner bottom electrode through a first through hole in the insulating layer at the gap, or the insulating layer at the gap exposes part of the inner bottom electrode between a first edge of the inner piezoelectric layer and the inner piezoelectric layer, and a first end of the first signal line is in contact with the exposed inner bottom electrode across the first edge; a second end of the first signal line is electrically connected with the outer top electrode;

[0017] A first end of the second signal line is electrically connected with the inner top electrode, and a second end of the second signal line is located on a side of the outer top electrode away from the inner top electrode, and the second end of the second signal line is electrically connected with the outer bottom electrode through a second through hole in the piezoelectric layer.

[0018] Optionally, the MEMS ultrasonic transducer further comprises:

[0019] A first external pin and a second external pin;

[0020] The first external pin and the second external pin are located on a side of the piezoelectric layer away from the substrate, and on a side of the outer top electrode away from the inner top electrode;

[0021] The first signal line is electrically connected with the first external pin, and the second signal line is electrically connected with the second external pin.

[0022] Optionally, the first signal line, the second signal line, the first external pin and the second external pin are located in the top electrode layer and are made of the same material as the top electrode layer.

[0023] Optionally, the substrate comprises a silicon substrate layer and a silicon dioxide layer, and the silicon dioxide layer is arranged on a side of the silicon substrate layer adjacent to the diaphragm.

[0024] The MEMS ultrasonic transducer provided by the embodiment of the utility model, through setting the through hole and the support area surrounding the through hole on the substrate, and ensuring that the vertical projection of the diaphragm on the substrate covers the through hole and at least part of the support area, a stable support structure is provided for the diaphragm. Prevent the diaphragm from collapsing or deforming during vibration, improve the structural stability and service life of the transducer. The bottom electrode layer, the piezoelectric layer and the top electrode layer are all divided into inner and outer rings, and the outer ring part surrounds the inner ring part. The outer ring top electrode and the inner ring bottom electrode are electrically connected, and the outer ring bottom electrode and the inner ring top electrode are electrically connected, so that when an alternating current signal is input, there is always a reverse electric field with a phase difference of 180 degrees in the piezoelectric layer of the inner and outer rings. Therefore, the driving of the differential pMUT can be realized without increasing the number of electrode pads and the complexity of the driving circuit, thereby meeting the requirements of higher performance, controllable cost, application complexity and the same as the existing devices.

[0025] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the utility model, nor is it used to limit the scope of the utility model. Other features of the utility model will become easy to understand through the following description. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical scheme in the embodiments of the utility model, the drawings needed to be used in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the utility model, and other drawings can be obtained by those skilled in the art without creating labor.

[0027] Figure 1 It is a top view of a MEMS ultrasonic transducer provided by the embodiment of the utility model.

[0028] Figure 2 It is Figure 1 It is a sectional view of the MEMS ultrasonic transducer along the AA' section line in the utility model.

[0029] Figure 3 It is a traditional non-differential single-electrode pMUT diagram.

[0030] Figure 4is Figure 3 The corresponding vibration simulation diagram.

[0031] Figure 5 is an inner-outer difference double-electrode pMUT diagram.

[0032] Figure 6 is Figure 5 The corresponding vibration simulation diagram.

[0033] Figure 7 is a MEMS ultrasonic transducer internal-external upper and lower electrode reverse interconnection, driving signal and internal electric field situation distribution diagram provided by the embodiment of the utility model.

[0034] Figure 8 is a flow chart of the manufacturing method of the MEMS ultrasonic transducer provided by the embodiment of the utility model.

[0035] Figure 9 is the transducer structure diagram after the base material layer is manufactured provided by the embodiment of the utility model.

[0036] Figure 10 is the transducer structure diagram after the bottom electrode material layer is manufactured provided by the embodiment of the utility model.

[0037] Figure 11 is the transducer structure diagram after the piezoelectric material layer is manufactured provided by the embodiment of the utility model.

[0038] Figure 12 is the transducer structure diagram after the piezoelectric layer is manufactured provided by the embodiment of the utility model.

[0039] Figure 13 is the piezoelectric layer etched away schematic diagram provided by the embodiment of the utility model.

[0040] Figure 14 is the transducer structure diagram after the bottom electrode layer is manufactured provided by the embodiment of the utility model.

[0041] Figure 15 is the bottom electrode etched away schematic diagram provided by the embodiment of the utility model.

[0042] Figure 16 is the transducer structure diagram after the insulating layer is manufactured provided by the embodiment of the utility model.

[0043] Figure 17 is the insulating layer schematic diagram provided by the embodiment of the utility model.

[0044] Figure 18 is the transducer structure diagram after the top electrode material layer is manufactured provided by the embodiment of the utility model.

[0045] Figure 19The utility model embodiment provides a transducer structure diagram after the top electrode layer is made.

[0046] Figure 20 The utility model embodiment provides a transducer structure diagram after the thinning layer.

[0047] Figure 21 The utility model embodiment provides a schematic diagram of the first silicon layer and the silicon dioxide layer being etched. DETAILED DESCRIPTION

[0048] In order to make the personnel in the technical field better understand the utility model scheme, below will combine the drawings in the utility model embodiment, and the technical scheme in the utility model embodiment is clearly and completely described, obviously, the described embodiment is only a part of the embodiment of the utility model, and is not all the embodiment. Based on the embodiment in the utility model, all other embodiments obtained by the ordinary skill in the art without making creative labor should belong to the protection scope of the utility model.

[0049] It should be noted that the terms "first", "second" and the like in the description and claims of the utility model and the above-mentioned drawings are used to distinguish similar objects, and do not have to be used to describe a particular order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the utility model described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to the clearly listed steps or units, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0050] The utility model embodiment provides a MEMS ultrasonic transducer, Figure 1 The utility model embodiment provides a MEMS ultrasonic transducer's plan view. Figure 2 It is Figure 1 The section view of MEMS ultrasonic transducer along AA' section line in the utility model embodiment. Figures 1-2 The utility model embodiment provides a MEMS ultrasonic transducer,

[0051] The base 10 and the diaphragm 20, bottom electrode layer 30, piezoelectric layer 40 and top electrode layer 50 that are sequentially laminated and arranged on one side of the base 10, the diaphragm 20 is arranged on the side of the bottom electrode layer 30 adjacent to the base 10;

[0052] The base 10 includes a through hole 11 and a support area 12 around the through hole 11;

[0053] The vertical projection of the diaphragm 20 on the substrate 10 covers the through hole 11 and at least part of the support area 12;

[0054] The bottom electrode layer 30 comprises an inner bottom electrode 31 and an outer bottom electrode 32, and the inner bottom electrode 31 and the outer bottom electrode 32 have a gap therebetween, and the outer bottom electrode 32 surrounds the inner bottom electrode 31; the vertical projection of the inner bottom electrode 31 on the substrate 10 is located in the through hole 11, and the vertical projection of the outer bottom electrode 32 on the substrate 10 covers part of the through hole 11 and at least part of the support area 12;

[0055] The piezoelectric layer 40 comprises an inner piezoelectric layer 41 and an outer piezoelectric layer 42, and the inner piezoelectric layer 41 and the outer piezoelectric layer 42 have a gap therebetween, and the outer piezoelectric layer 42 surrounds the inner piezoelectric layer 41; the vertical projection of the inner piezoelectric layer 41 on the bottom electrode layer 30 is located in the inner bottom electrode 31, and the vertical projection of the outer piezoelectric layer 42 on the substrate 10 covers part of the through hole 11 and at least part of the support area 12;

[0056] The top electrode layer 50 comprises an inner top electrode 51 and an outer top electrode 52, and the inner top electrode 51 and the outer top electrode 52 have a gap therebetween; the outer top electrode 52 surrounds the inner top electrode 51, the vertical projection of the inner top electrode 51 on the piezoelectric layer 40 is located in the inner piezoelectric layer 41, and the vertical projection of the outer top electrode 52 on the piezoelectric layer 40 is located in the outer piezoelectric layer 42;

[0057] The outer top electrode 52 and the inner bottom electrode 31 are electrically connected, and the outer bottom electrode 32 and the inner top electrode 51 are electrically connected.

[0058] The working principle of the pMUT device is related to the piezoelectric effect of the piezoelectric film layer. When the positive piezoelectric effect occurs, that is, the diaphragm receives the sound wave, the ultrasonic wave causes the diaphragm to vibrate, continuously producing up and down reciprocating deformation, periodically stretching / compressing the piezoelectric layer, so that the piezoelectric layer generates electric charge, and the electric charge is connected to the outside through the upper and lower electrodes, and the external circuit can receive the changing electric charge signal; when the inverse piezoelectric effect occurs, the external circuit inputs a high-frequency alternating voltage (such as a sine wave) to the upper and lower electrodes, and the upper and lower electrodes generate an alternating electric field in the piezoelectric layer, and the electric field causes the piezoelectric layer to produce stretching / compression deformation, thereby driving the diaphragm to vibrate to produce sound waves.

[0059] Figure 3 is a traditional non-differential single-electrode pMUT diagram. Figure 4 is Figure 3 is the corresponding vibration simulation diagram. Figure 5 is an inner-outer differential double-electrode pMUT diagram. Figure 6 is Figure 5 is the corresponding vibration simulation diagram. Reference Figures 3-6, realize differential voltage drive, then need two groups of reverse drive signal input, namely the electric field of inner ring electrode and outer ring electrode are opposite, thus need two pairs of electrode pad and two kinds of drive signal, input to inner and outer piezoelectric layer respectively.pMUT adopts differential electrode, namely inner and outer respectively apply opposite electric field, through piezoelectric principle and simulation can know that, compared with common single electrode structure, differential structure can realize nearly doubled sensitivity under the same driving voltage.

[0060] Figure 7 It is a kind of MEMS ultrasonic transducer internal and external electrode reverse interconnection, driving signal and internal electric field condition distribution map provided by the embodiment of the utility model. Figure 7 By etching bottom electrode layer, separate inner ring bottom electrode and outer ring bottom electrode, and by constructing insulation layer, connect inner ring top electrode with outer ring bottom electrode, outer ring top electrode with inner ring bottom electrode, so that there is always opposite electric field with phase difference of 180 degrees in inner ring piezoelectric layer and outer ring piezoelectric layer when AC signal is input, therefore, the drive of differential pMUT can be realized without increasing the logarithm of electrode pad and the complexity of driving circuit, so as to meet the requirement of keeping the same with existing device in higher performance, cost controllable, application complexity.

[0061] Specifically, by setting through hole and support area surrounding through hole on substrate 10, enough support can be provided for diaphragm, and meanwhile, the hindrance of substrate 10 to diaphragm vibration is reduced.The vertical projection of diaphragm on substrate 10 covers through hole and at least part of support area, which helps to increase the effective vibration area of diaphragm, thereby enhancing the emission and reception performance of ultrasonic waves.Bottom electrode layer 30 includes inner ring bottom electrode 31 and outer ring bottom electrode 32, piezoelectric layer 40 includes inner ring piezoelectric layer 41 and outer ring piezoelectric layer 42, and top electrode layer 50 includes inner ring top electrode 51 and outer ring top electrode 52, all of which are designed as inner and outer ring structure, inner ring bottom electrode 31 and outer ring bottom electrode 32 adopt same material in the same layer, inner ring piezoelectric layer 41 and outer ring piezoelectric layer 42 adopt same material in the same layer, and inner ring top electrode 51 and outer ring top electrode 52 adopt same material in the same layer, which all reduce production cost, inner ring bottom electrode 31 and outer ring bottom electrode 32 are made in the same process flow, inner ring piezoelectric layer 41 and outer ring piezoelectric layer 42 are made in the same process flow, and inner ring top electrode 51 and outer ring top electrode 52 are made in the same process flow, thereby simplifying process flow.

[0062] The MEMS ultrasonic transducer provided by the embodiment of the utility model, through setting through hole 11 and support area 12 surrounding through hole 11 on base 10, and ensuring that the vertical projection of diaphragm 20 on base 10 covers through hole 11 and at least part of support area 12, a stable support structure is provided for diaphragm 20. The diaphragm 20 is prevented from collapsing or deforming during vibration, and the structural stability and service life of the transducer are improved. The bottom electrode layer 30, the piezoelectric layer 40 and the top electrode layer 50 are all divided into inner and outer rings, and the outer ring part surrounds the inner ring part. The outer ring top electrode 52 and the inner ring bottom electrode 31 are electrically connected, and the outer ring bottom electrode 32 and the inner ring top electrode 51 are electrically connected, so that when an alternating current signal is input, there is always a reverse electric field with a phase difference of 180 degrees in the piezoelectric layer of the inner and outer rings. Therefore, the driving of the differential pMUT can be realized without increasing the number of electrode pad pairs and the complexity of the driving circuit, thereby meeting the requirements of higher performance, controllable cost, application complexity and the same as the existing device.

[0063] With reference to Figure 1 And Figure 2 , the MEMS ultrasonic transducer further comprises:

[0064] An insulating layer 60 covers at least part of the gap between the inner ring bottom electrode 31 and the outer ring bottom electrode 32, and the gap between the inner ring piezoelectric layer 41 and the outer ring piezoelectric layer 42.

[0065] Specifically, the insulating layer 60 can effectively isolate the inner ring bottom electrode 31 and the outer ring bottom electrode 32, and the inner ring piezoelectric layer 41 and the outer ring piezoelectric layer 42, prevent current from flowing in areas where it should not flow, and improve the electrical isolation performance of the entire ultrasonic transducer. The insulating layer 60 not only plays an electrical isolation role, but also can be used as a structural support layer to enhance the overall structural stability of the ultrasonic transducer. It helps to prevent unnecessary displacement or deformation between the inner ring bottom electrode 31 and the outer ring bottom electrode 32 under the action of vibration or external force, thereby prolonging the service life of the ultrasonic transducer, achieving more efficient sound wave emission and reception, and improving the sensitivity and resolution of the ultrasonic transducer.

[0066] Optionally, the outer ring top electrode 52 also has an opening, the opening penetrates the outer ring top electrode 52 in a direction in which the outer ring top electrode 52 points to the inner ring top electrode 51, and the insulating layer 60 also covers the piezoelectric layer 40 at the opening;

[0067] The insulating layer 60 at the opening is provided with a first signal line 61 and a second signal line 62 away from the surface of the substrate 10; the first end of the first signal line 61 is electrically connected with the inner ring bottom electrode 31 through a first through hole in the insulating layer 60 at the gap, or the insulating layer 60 at the gap is adjacent to the first edge of the inner ring piezoelectric layer 41, and a part of the inner ring bottom electrode 31 is exposed between the insulating layer 60 at the gap and the inner ring piezoelectric layer 41, and the first end of the first signal line 61 is in contact with the exposed inner ring bottom electrode 31 through the first edge (as shown in FIG. 6) ; the second end of the first signal line 61 is electrically connected with the outer ring top electrode 52. Figure 1 The second end of the second signal line 62 is electrically connected with the outer ring bottom electrode 32 through a second through hole 80 in the piezoelectric layer 40.

[0068] The first end of the second signal line 62 is electrically connected with the inner ring top electrode 51, and the second end of the second signal line 62 is located on the side of the outer ring top electrode 52 away from the inner ring top electrode 51 and is electrically connected with the outer ring bottom electrode 32 through a second through hole 80 in the piezoelectric layer 40.

[0069] Specifically, the first end of the first signal line 61 is electrically connected with the inner ring bottom electrode 31 through a first through hole in the insulating layer 60 at the gap, and the signal on the first signal line 61 can be directly transmitted to the inner ring bottom electrode 31. The second end of the first signal line 61 is electrically connected with the outer ring top electrode 52, forming a signal path from the inner ring bottom electrode 31 to the outer ring top electrode 52. The first end of the second signal line 62 is electrically connected with the inner ring top electrode 51, and the second end of the second signal line 62 is electrically connected with the outer ring bottom electrode 32 through a second through hole 80 in the piezoelectric layer 40. Another signal path from the inner ring top electrode 51 to the outer ring bottom electrode 32 is formed. When the signals are transmitted through the two paths, they will generate a changing electric field in the piezoelectric layer 40. Due to the piezoelectric effect, the changing electric field will cause the mechanical deformation of the piezoelectric layer 40, thereby generating ultrasonic waves. In this way, the MEMS ultrasonic transducer can convert the input electrical signal into ultrasonic waves and radiate outward through its structure.

[0070] Optionally, the MEMS ultrasonic transducer further comprises:

[0071] a first external pin 71 and a second external pin 72;

[0072] The first external pin 71 and the second external pin 72 are located on the side of the piezoelectric layer 40 away from the substrate 10 and on the side of the outer ring top electrode 52 away from the inner ring top electrode 51.

[0073] The first signal line 61 is electrically connected with the first external pin 71, and the second signal line 62 is electrically connected with the second external pin 72.

[0074] Specifically, the first external pin 71 and the second external pin 72 are located on the side of the piezoelectric layer 40 away from the substrate 10 and on the side of the outer ring top electrode 52 away from the inner ring top electrode 51.

[0075] Optionally, the first signal line 61, the second signal line 62, the first external pin 71 and the second external pin 72 are located on the top electrode layer 50 and are made of the same material as the top electrode layer 50.

[0076] Specifically, the first signal line 61, the second signal line 62, the first external pin 71 and the second external pin 72 are located on the top electrode layer 50, which can enhance the overall structural stability of the transducer, optimize the spatial layout of the transducer, and improve the integration. The first signal line 61, the second signal line 62, the first external pin 71 and the second external pin 72 are made of the same material as the top electrode layer 50 and are manufactured in the same process flow, which can simplify the manufacturing process of the transducer, reduce the manufacturing cost, and improve the production efficiency.

[0077] With reference to Figure 2 , the substrate 10 includes a silicon substrate layer 111 and a silicon dioxide layer 103, and the silicon dioxide layer 103 is arranged on the side of the silicon substrate layer 111 adjacent to the diaphragm 20.

[0078] Specifically, the silicon dioxide layer 103 as an insulating layer can isolate the electrical signal interference between the silicon substrate layer 111 and the diaphragm 20, reduce the parasitic capacitance formed between the silicon substrate layer 111 and the diaphragm 20, reduce the noise level and power consumption of the transducer, and improve the overall structural stability of the transducer. The silicon dioxide layer 103 also has a certain mechanical strength, which can support the stability of the diaphragm under high-frequency vibration and prolong the service life of the transducer.

[0079] The embodiment of the utility model further provides a flow chart of the manufacturing method of the MEMS ultrasonic transducer. Figure 8 The embodiment of the utility model provides a flow chart of the manufacturing method of the MEMS ultrasonic transducer, and with reference to Figure 8 The manufacturing method of the MEMS ultrasonic transducer comprises the following steps:

[0080] S310, providing a substrate material layer;

[0081] Among them, Figure 9 The embodiment of the utility model provides a transducer structure diagram after the substrate material layer is manufactured. With reference to Figure 9 , the substrate material layer 100 includes a first silicon layer 101 and a second silicon layer 102, wherein the first silicon layer 101 and the second silicon layer 102 are provided with a silicon dioxide layer 103 therebetween. The substrate material layer 100 can be an SOI substrate, and the thickness of the substrate material layer 100 is 725 um.

[0082] S320, a bottom electrode layer, a piezoelectric layer and a top electrode layer are arranged on the surface of the substrate material layer; wherein the bottom electrode layer, the piezoelectric layer and the top electrode layer are sequentially stacked and arranged, and the piezoelectric layer is arranged on the side of the bottom electrode layer away from the substrate material layer;

[0083] S330, the surface of the base material layer away from the bottom electrode layer is patterned to form a base with a through hole and a support area and a diaphragm;

[0084] The support area surrounds the through hole, and the diaphragm is arranged on the side of the base adjacent to the bottom electrode layer; the vertical projection of the diaphragm on the base covers the through hole and at least part of the support area;

[0085] The bottom electrode layer includes an inner ring bottom electrode and an outer ring bottom electrode, and the inner ring bottom electrode and the outer ring bottom electrode have a gap therebetween, and the outer ring bottom electrode surrounds the inner ring bottom electrode; the vertical projection of the inner ring bottom electrode on the base is located in the inner ring bottom electrode, and the vertical projection of the outer ring bottom electrode on the base covers part of the through hole and at least part of the support area;

[0086] The piezoelectric layer includes an inner ring piezoelectric layer and an outer ring piezoelectric layer, and the inner ring piezoelectric layer and the outer ring piezoelectric layer have a gap therebetween, and the outer ring piezoelectric layer surrounds the inner ring piezoelectric layer; the vertical projection of the inner ring piezoelectric layer on the bottom electrode layer is located in the inner ring piezoelectric layer, and the vertical projection of the outer ring piezoelectric layer on the base covers part of the through hole and at least part of the support area;

[0087] The top electrode layer includes an inner ring top electrode and an outer ring top electrode, and the inner ring top electrode and the outer ring top electrode have a gap therebetween; the outer ring top electrode surrounds the inner ring top electrode, the vertical projection of the inner ring top electrode on the piezoelectric layer is located in the inner ring piezoelectric layer, and the vertical projection of the outer ring top electrode on the piezoelectric layer is located in the outer ring piezoelectric layer;

[0088] The outer ring top electrode and the inner ring bottom electrode are electrically connected, and the outer ring bottom electrode and the inner ring top electrode are electrically connected.

[0089] The MEMS ultrasonic transducer provided by the embodiment of the utility model, through setting the through hole and the support area surrounding the through hole on the base, and ensuring that the vertical projection of the diaphragm on the base covers the through hole and at least part of the support area, a stable support structure is provided for the diaphragm. Prevent the diaphragm from collapsing or deforming during vibration, improve the structural stability and service life of the transducer. The bottom electrode layer, the piezoelectric layer and the top electrode layer are all divided into inner ring and outer ring, and the outer ring part surrounds the inner ring part. The outer ring top electrode and the inner ring bottom electrode are electrically connected, and the outer ring bottom electrode and the inner ring top electrode are electrically connected, so that when the alternating current signal is input, there is always a reverse electric field with a phase difference of 180 degrees in the piezoelectric layer of the inner and outer rings. Therefore, the driving of the differential pMUT can be realized without increasing the number of electrode pads and the complexity of the driving circuit, thereby meeting the requirements of higher performance, controllable cost, application complexity and the same as the existing devices.

[0090] Figure 10 It is the transducer structure diagram after the bottom electrode material layer is made provided by the embodiment of the utility model. Reference Figure 10Optionally, a bottom electrode layer, a piezoelectric layer and a top electrode layer are arranged on the surface of the substrate material layer, comprising:

[0091] A bottom electrode material layer 200 is arranged on the surface of the substrate material layer 100;

[0092] A piezoelectric material layer 300 is arranged on the surface of the bottom electrode material layer 200;

[0093] The piezoelectric material layer 300 is patterned to form a piezoelectric layer 40;

[0094] The bottom electrode material layer 200 is patterned to form a bottom electrode layer 30;

[0095] An insulating layer 60 is arranged; wherein the insulating layer 60 covers at least part of the gap between the inner circle bottom electrode 31 and the outer circle bottom electrode 32, and the gap between the inner circle piezoelectric layer 41 and the outer circle piezoelectric layer 42;

[0096] A top electrode material layer 400 is arranged on the surface of the piezoelectric layer 40;

[0097] The top electrode material layer 400 is patterned to form a top electrode layer 50.

[0098] The material of the bottom electrode material layer 200 is Pt, the thickness of the bottom electrode material layer 200 is 200nm, and the bottom electrode material layer 200 can be grown on the surface of the substrate material layer 100 by magnetron radio frequency sputtering. Figure 11 is a transducer structure diagram provided by an embodiment of the present application after the piezoelectric material layer is made. Figure 11 The piezoelectric material layer 300 is a PZT piezoelectric film, the thickness of the piezoelectric material layer 300 is 2um, and the piezoelectric material layer 300 can be grown on the surface of the bottom electrode material layer 200 by magnetron radio frequency sputtering. Figure 12 is a transducer structure diagram provided by an embodiment of the present application after the piezoelectric layer is made. Figure 13 is a piezoelectric layer etched away schematic diagram provided by an embodiment of the present application. Reference Figures 11-13 The piezoelectric material layer 300 can be patterned to form the piezoelectric layer 40 by photoetching, developing and etching processes. Figure 14 is a transducer structure diagram provided by an embodiment of the present application after the bottom electrode layer is made. Figure 15 is a bottom electrode etched away schematic diagram provided by an embodiment of the present application. Reference Figure 10 , Figure 14 and Figure 15 The bottom electrode material layer 200 can be patterned to form the bottom electrode layer 30 by photoetching, developing and etching processes. Figure 16 is a transducer structure diagram provided by an embodiment of the present application after the insulating layer is made. Figure 17Is the insulating layer schematic diagram provided by the utility model embodiment. Reference Figure 16 And Figure 17 The insulating layer 60 is grown and patterned to cover the short-circuit-prone part. Figure 18 Is the transducer structure diagram after the top electrode material layer is made provided by the utility model embodiment. Reference Figure 18 The material of the top electrode material layer 400 is Au, the thickness of the top electrode material layer 400 is 200 um, and the top electrode material layer 400 can be grown on the surface of the piezoelectric layer 40 by magnetron radio frequency sputtering.

[0099] Specifically, a layer of conductive material is deposited on the surface of the base material layer 100 to form a bottom electrode material layer 200. The bottom electrode material layer 200 will serve as the lower electrode of the piezoelectric material for applying an electric field. A layer of piezoelectric material (such as lead zirconate titanate, aluminum nitride, etc.) is deposited on the surface of the bottom electrode material layer 200 to form a piezoelectric material layer 300. The piezoelectric material will deform under the action of an electric field, thereby generating ultrasonic waves. Through processes such as photolithography and etching, the piezoelectric material layer 300 is patterned into the desired shape and size to form a piezoelectric layer 40, improving the performance of the transducer. Then, the bottom electrode material layer 200 is patterned to match the shape and size of the piezoelectric layer, forming a bottom electrode layer 30. A layer of insulating material (such as silicon dioxide, silicon nitride, etc.) is deposited at the periphery of the bottom electrode layer 30 and the piezoelectric layer 40, as well as any gaps between the bottom electrode layer 30 and the piezoelectric layer 40, to form an insulating layer 60. The insulating layer 60 is used to prevent short circuits between different electrodes and protect the internal electronic structure, improving the electrical stability and reliability of the transducer. A layer of conductive material is deposited on the surface of the piezoelectric layer 40 to form a top electrode material layer 400. The top electrode material layer 400 will serve as the upper electrode of the piezoelectric material, together with the bottom electrode layer 30, to form an electric field. The top electrode material layer 400 is patterned to form a top electrode layer 50. The shape and size of the top electrode layer 50 should match the piezoelectric layer to ensure that the electric field is uniformly applied to the piezoelectric layer 40.

[0100] Continuing to refer to Figure 1 Patterning the top electrode material layer to form the top electrode layer includes:

[0101] Etching the top electrode material layer to form the inner ring top electrode 51, the outer ring top electrode 52, the first signal line 61, the second signal line 62, the first external pin 71, and the second external pin 72;

[0102] The outer ring top electrode 52 has an opening that penetrates the outer ring top electrode 52 in a direction pointing from the outer ring top electrode 52 to the inner ring top electrode 51, and the insulating layer also covers the piezoelectric layer at the opening;

[0103] The first signal line 61 and the second signal line 62 are arranged on the surface of the insulating layer away from the substrate at the opening, the first end of the first signal line 61 is electrically connected with the inner ring bottom electrode 31 through the first through hole in the insulating layer at the gap, or the insulating layer 60 at the gap is adjacent to the first edge of the inner ring piezoelectric layer 41 and exposes the part of the inner ring bottom electrode 31 between the inner ring piezoelectric layer 41, the first end of the first signal line 61 is in contact with the exposed inner ring bottom electrode 31 through the first edge (as shown in the figure) ; the second end of the first signal line 61 is electrically connected with the outer ring top electrode 52; Figure 1

[0104] The first end of the second signal line 62 is electrically connected with the inner ring top electrode 51, and the second end of the second signal line 62 is located on the side of the outer ring top electrode 52 away from the inner ring top electrode 51, and the second end of the second signal line 62 is electrically connected with the outer ring bottom electrode 32 through the second through hole 80 in the piezoelectric layer;

[0105] The first external pin 71 and the second external pin 72 are located on the side of the piezoelectric layer away from the substrate and on the side of the outer ring top electrode 52 away from the inner ring top electrode 51; the first signal line 61 is electrically connected with the first external pin 71, and the second signal line 62 is electrically connected with the second external pin 72.

[0106] Wherein, Figure 19 is the transducer structure diagram after the top electrode layer is made provided by the embodiment of the utility model. Referring to Figure 19 , the top electrode material layer is patterned through the photoetching, developing and etching process, the inner ring top electrode 51 and the outer ring top electrode 52 are formed, and the outer ring top electrode 52 and the inner ring bottom electrode 31 are electrically connected, and the outer ring bottom electrode 32 and the inner ring top electrode 51 are electrically connected.

[0107] ​Specifically, when the external signal is input through the first external pin 71 and the second external pin 72, the external signal will be transmitted along the first signal line 61 and the second signal line 62 respectively. The first signal line 61 transmits the external signal from the first external pin 71 to the outer ring top electrode 52, and since the first end of the first signal line 61 is electrically connected to the inner ring bottom electrode 31 through the through hole in the insulating layer, the external signal can also be transmitted through the inner ring bottom electrode 31. The second signal line 62 transmits the signal from the inner ring top electrode 51 to the outer ring bottom electrode 32, and the second end thereof is electrically connected to the outer ring bottom electrode 32 through the through hole in the piezoelectric layer, realizing the cross-layer transmission of the signal and improving the utilization rate and transmission efficiency of the signal. When the external signal acts on the piezoelectric layer, the piezoelectric layer will generate corresponding vibration due to the piezoelectric effect. The vibration will be jointly affected by the inner ring top electrode 51, the outer ring top electrode 52 and the bottom electrode layer, forming a complex vibration mode, which can enhance the emission effect of the ultrasonic wave or improve the receiving sensitivity. Through the vibration of the piezoelectric layer, the MEMS ultrasonic transducer can emit ultrasonic waves. When the external ultrasonic wave acts on the transducer, it will also cause the vibration of the piezoelectric layer, and then the vibration signal is converted into an electric signal through the electrode layer and the signal line for receiving and processing.

[0108] Optionally, the base material layer comprises a first silicon layer, a silicon dioxide layer and a second silicon layer arranged in a stack, and the second silicon layer is arranged on a side of the silicon dioxide layer adjacent to the bottom electrode layer.

[0109] The surface of the base material layer away from the bottom electrode layer is patterned to form a base and a diaphragm having a through hole and a support area.

[0110] The first silicon layer is thinned.

[0111] The first silicon layer and the silicon dioxide layer are etched respectively to form a base and a diaphragm having a through hole and a support area; wherein the base comprises a first silicon layer having a through hole and a silicon dioxide layer having a through hole.

[0112] Wherein, Figure 20 is a transducer structure diagram after thinning provided by an embodiment of the utility model. Referring to Figure 20 , the base material layer 100 can be an SOI substrate, and thinning the reverse surface of the base material layer 100 can improve the etching process precision subsequently, thereby improving the process consistency of the device.

[0113] Figure 21 is a schematic view of the first silicon layer and the silicon dioxide layer etched away provided by an embodiment of the utility model. Referring to Figure 2 , Figure 20 and Figure 21The first silicon layer 101 is etched by Deep Reactive Ion Etching (Deep-RIE), and the silicon dioxide layer 103 is etched by Inductively Coupled Plasma Etcher (ICP), so as to release the device diaphragm 20.

[0114] Specifically, the first silicon layer 101, the silicon dioxide layer 103 and the second silicon layer 102 are laminated as the base material layer 100. The second silicon layer 102 is arranged on the side of the silicon dioxide layer 103 adjacent to the bottom electrode layer 30. The first silicon layer 101 is thinned to reduce the overall thickness of the base while retaining sufficient mechanical strength to support subsequent etching and diaphragm 20 forming processes. The first silicon layer 101 and the silicon dioxide layer 103 are etched respectively. Through precise etching process, the through hole 11 and the support area 12 are formed in the first silicon layer 101 and the silicon dioxide layer 103. The through hole 11 is used for subsequent electrode connection and signal transmission, while the support area 12 is used to support the diaphragm 20 and prevent it from collapsing, thereby improving the overall stability of the structure. The diaphragm 20 is a key component of the MEMS ultrasonic transducer, which is used to generate vibration and emit ultrasonic waves under the action of an electric field.

[0115] It should be understood that the various forms of flow shown above can be used to reorder, add or delete steps. For example, the steps described in the present application can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions of the present application can be achieved, which are not limited herein.

[0116] The above specific embodiments do not constitute a limitation on the protection scope of the present application. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A MEMS ultrasonic transducer, characterized by, The MEMS ultrasonic transducer comprises: a substrate, and a diaphragm, a bottom electrode layer, a piezoelectric layer and a top electrode layer which are sequentially arranged on one side of the substrate; the diaphragm is arranged on the side of the bottom electrode layer adjacent to the substrate; the substrate comprises a through hole and a support area surrounding the through hole; the vertical projection of the diaphragm on the substrate covers the through hole and at least part of the support area; the bottom electrode layer comprises an inner ring bottom electrode and an outer ring bottom electrode, and a gap is formed between the inner ring bottom electrode and the outer ring bottom electrode, and the outer ring bottom electrode surrounds the inner ring bottom electrode; the vertical projection of the inner ring bottom electrode on the substrate is located in the through hole, and the vertical projection of the outer ring bottom electrode on the substrate covers part of the through hole and at least part of the support area; the piezoelectric layer comprises an inner ring piezoelectric layer and an outer ring piezoelectric layer, and a gap is formed between the inner ring piezoelectric layer and the outer ring piezoelectric layer, and the outer ring piezoelectric layer surrounds the inner ring piezoelectric layer; the vertical projection of the inner ring piezoelectric layer on the bottom electrode layer is located in the inner ring bottom electrode, and the vertical projection of the outer ring piezoelectric layer on the substrate covers part of the through hole and at least part of the support area; the top electrode layer comprises an inner ring top electrode and an outer ring top electrode, and a gap is formed between the inner ring top electrode and the outer ring top electrode; the outer ring top electrode surrounds the inner ring top electrode, the vertical projection of the inner ring top electrode on the piezoelectric layer is located in the inner ring piezoelectric layer, and the vertical projection of the outer ring top electrode on the piezoelectric layer is located in the outer ring piezoelectric layer; the outer ring top electrode and the inner ring bottom electrode are electrically connected, and the outer ring bottom electrode and the inner ring top electrode are electrically connected.

2. The MEMS ultrasonic transducer of claim 1, wherein, Further comprising: an insulating layer covering at least part of the gap between the inner ring bottom electrode and the outer ring bottom electrode, and the gap between the inner ring piezoelectric layer and the outer ring piezoelectric layer.

3. The MEMS ultrasonic transducer according to claim 2, wherein: the outer ring top electrode further has an opening penetrating the outer ring top electrode in a direction of the outer ring top electrode pointing to the inner ring top electrode, and the insulating layer further covers the piezoelectric layer at the opening; a first signal line and a second signal line are arranged on the surface of the insulating layer away from the substrate at the opening; a first end of the first signal line is electrically connected to the inner ring bottom electrode through a first through hole in the insulating layer at the gap, or part of the inner ring bottom electrode is exposed between the first edge of the inner ring piezoelectric layer adjacent to the insulating layer at the gap and the inner ring piezoelectric layer, and a first end of the first signal line is in contact with the exposed inner ring bottom electrode across the first edge; a second end of the first signal line is electrically connected to the outer ring top electrode; a first end of the second signal line is electrically connected to the inner ring top electrode, and a second end of the second signal line is located on a side of the outer ring top electrode away from the inner ring top electrode, and the second end of the second signal line is electrically connected to the outer ring bottom electrode through a second through hole in the piezoelectric layer.

4. The MEMS ultrasonic transducer of claim 3, wherein, Further comprising: a first external pin and a second external pin; The first and second external pins are located on a side of the piezoelectric layer away from the substrate and on a side of the outer top electrode away from the inner top electrode. The first signal line is electrically connected to the first external pin, and the second signal line is electrically connected to the second external pin. 5.The MEMS ultrasonic transducer of claim 4, wherein: The first and second signal lines, the first and second external pins are all located on the top electrode layer and are made of the same material as the top electrode layer. 6.The MEMS ultrasonic transducer of claim 1, wherein: The substrate includes a silicon substrate layer and a silicon dioxide layer, and the silicon dioxide layer is disposed on a side of the silicon substrate layer adjacent to the diaphragm.

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