Ultrasonic Sensor and Method for Manufacturing the Same

Abstract

The present invention relates to an ultrasonic sensor and a manufacturing method thereof. The manufacturing method of the ultrasonic sensor includes: providing a substrate, including: a first substrate, a bonding layer disposed above the first substrate, a cavity provided in the bonding layer, a piezoelectric vibrator located above the bonding layer, including a vibrating portion, the vibrating portion being located above the cavity, the vibrating portion including a second electrode, a piezoelectric film, and a first electrode stacked in sequence from bottom to top; providing a back plate; forming a bonding layer on the back plate or on the piezoelectric vibrator; bonding the back plate and the substrate through the bonding layer; etching the back plate and the bonding layer to form a groove, the groove exposing the piezoelectric vibrator, and the groove and the projection of the vibrating portion in the direction of the first substrate have an overlapping part. In a longitudinal cross-section perpendicular to the plane where the first substrate is located, in a direction away from the substrate, the top size of the groove is larger than the bottom size of the groove.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor device manufacturing, and particularly to an ultrasonic sensor and a manufacturing method thereof. Background Art

[0002] Ultrasonic time-of-flight (ToF) sensors are generally considered to be the best distance sensors suitable for automotive, industrial, and unmanned aerial vehicle and robot applications. Compared with optical sensors or infrared sensors, it has many advantages. It can provide the most accurate distance measurement, is not affected by the size or color of the target object, is not interfered by environmental noise, and can be used in an environment with direct sunlight. These advantages, as well as the characteristics of being rugged, accurate, and reliable, make ultrasonic sensors widely used in industrial and automotive applications.

[0003] An ultrasonic sensor is a sensor that converts ultrasonic signals into other energy signals (usually electrical signals). Its basic principle: using a micro ultrasonic transducer (PMUT) to emit ultrasonic pulses, and then receiving the echo reflected by the target object in the sensor's field of view. By calculating the ultrasonic time of flight, the sensor can determine the position of an object relative to the device, and at the same time trigger a programmed behavior. Ultrasonic sensors can provide accurate and low-latency distance measurement results, with a measurement speed of up to 100 samples per second, a position noise of less than 1 mm, and also have advantages such as low power consumption, wide viewing angle, and strong target detection ability.

[0004] In the process of manufacturing and packaging ultrasonic sensors, it is usually to combine a metal shell and a chip to complete the packaging, and it is necessary to directly etch the substrate to form a groove. The etching process is likely to have an adverse effect on the chip, resulting in problems such as low packaging efficiency, low reliability, and low yield; in addition, there is a cavity on one side of the vibration part of the ultrasonic sensor, and the other side is used to receive or emit ultrasonic waves. During the manufacturing process, the part with the cavity is usually set on the outer periphery of the vibration part. The cavity is always a sealed cavity, and the impedance of the air in the cavity to ultrasonic waves cannot cancel out the impedance of the outside to ultrasonic waves, which is not conducive to the reception and recognition of ultrasonic signals. At the same time, the pressures on the upper and lower surfaces of the vibration part are inconsistent, causing the vibration part to be deformed or broken under pressure, affecting the quality and yield of the ultrasonic sensor.

[0005] Therefore, how to improve the manufacturing method of ultrasonic sensors, and improve the quality, reliability, yield, and packaging efficiency of ultrasonic sensors is the problem faced at present. Summary of the Invention

[0006] The purpose of the present invention is to provide an ultrasonic sensor and a manufacturing method thereof, which can solve the problems of low quality, low reliability, low yield, and low packaging efficiency of ultrasonic sensors.

[0007] To achieve the above object, the present invention provides a manufacturing method of an ultrasonic sensor, including:

[0008] Providing a substrate, the substrate includes:

[0009] A first substrate,

[0010] A bonding layer, the bonding layer is disposed above the first substrate, and a cavity is provided in the bonding layer,

[0011] A piezoelectric vibrator located above the bonding layer, the piezoelectric vibrator includes a vibrating portion, the vibrating portion is located above the cavity, and the vibrating portion includes a second electrode, a piezoelectric film, and a first electrode stacked in sequence from bottom to top;

[0012] Providing a backplane;

[0013] Forming a bonding layer on the backplane or on the piezoelectric vibrator;

[0014] Bonding the backplane and the substrate through the bonding layer;

[0015] Etching the backplane and the bonding layer to form a groove, the groove exposes the piezoelectric vibrator, and a part of the groove overlaps with the projection of the vibrating portion in the direction of the first substrate. In a longitudinal section perpendicular to the plane where the first substrate is located, the top size of the groove is larger than the bottom size of the groove in the direction away from the substrate. The backplane and the bonding layer constitute a second substrate.

[0016] The present invention also provides an ultrasonic sensor, including:

[0017] A first substrate and a bonding layer located above the first substrate, a cavity is provided in the bonding layer;

[0018] A piezoelectric vibrator located above the bonding layer, the piezoelectric vibrator includes a vibrating portion, the vibrating portion is located above the cavity, and the vibrating portion includes a second electrode, a piezoelectric film, and a first electrode stacked in sequence from bottom to top;

[0019] A second substrate, disposed on the piezoelectric vibrator, the second substrate includes a bonding layer and a backplane stacked in sequence from bottom to top, a groove is provided in the second substrate, the groove exposes the piezoelectric vibrator, and a part of the groove overlaps with the projection of the vibrating portion in the direction of the first substrate. In a longitudinal section perpendicular to the plane where the first substrate is located, the top size of the groove is larger than the bottom size of the groove in the direction away from the substrate.

[0020] The beneficial effect of the present invention is that:

[0021] The present invention provides a method for forming a groove, a bonding backplane and a substrate. By completing the formation process of the bonding layer on the backplane or the substrate, the substrate and the backplane are bonded through a bonding process. And when the bonding layer is formed on the backplane and the groove is etched, it is possible to avoid the possible damage to the matching layer during the process of forming the groove by the etching process.

[0022] Furthermore, when a photolithographic material such as a dry film is used to form the bonding layer, the groove in the bonding layer is formed through a photolithography process, which avoids the possible damage to the matching layer during the process of forming the groove by the etching process, ensures the requirement of the thickness accuracy of the matching layer, reduces the influence on the bonding strength of the bonding layer, and at the same time avoids the adverse effect of the etching process on the substrate, ensures the bonding strength between the layers, and is beneficial to improving the reliability and yield of the ultrasonic sensor.

[0023] Furthermore, by forming a bonding layer with a cavity above the piezoelectric vibrator, forming a first substrate on the bonding layer to cover the cavity, and forming a vent hole communicating the cavity and the outside on the periphery of the vibrating part, the pressures on the upper and lower surfaces of the vibrating part are made consistent, preventing the vibrating part from deforming or cracking due to atmospheric pressure, and also enabling the pressure in the cavity to be controllable during the subsequent process of forming the bonding layer and the backplane, improving the structural strength of the ultrasonic sensor, and improving the reliability and yield.

[0024] Furthermore, when the material of the bonding layer is a dry film, the dry film can be formed on the piezoelectric film and the second electrode through a film laminating process, improving the fitting degree and bonding strength of the contact surface and improving the reliability.

[0025] Furthermore, the cavity is formed by photolithographing the bonding layer. The photolithography process reduces the influence on the bonding strength of the bonding layer, simplifies the process flow at the same time, and improves the packaging efficiency. Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figures 1 to 17 The structural schematic diagrams corresponding to different steps in the manufacturing method of the ultrasonic sensor according to an embodiment of the present invention are shown.

[0028] Figure 16 The structural schematic diagram of an ultrasonic sensor according to an embodiment of the present invention is shown.

[0029] Description of the Reference Numerals:

[0030] 10 - Carrier substrate; 11 - Matching layer; 12 - Isolation layer; 21 - First electrode; 210 - First electrode lead-out part; 22 - Piezoelectric film; 23 - Second electrode; 230 - Second electrode lead-out part; 24 - Bonding layer; 25 - Cavity; 30 - First substrate; 211 - First electrical connection structure; 231 - Second electrical connection structure; 301 - Vent hole; 40 - Second substrate; 401 - Backplane; 402 - Bonding layer; 41 - Groove; 411 - First groove; 412 - Second groove. Detailed implementation manner

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. According to the following description and drawings, the advantages and features of the present invention will be clearer. However, it should be noted that the concept of the technical solution of the present invention can be implemented in many different forms and is not limited to the specific embodiments described herein. The accompanying drawings are all in a very simplified form and use non-precise scales, only for the purpose of facilitating and clearly assisting in explaining the purpose of the embodiments of the present invention.

[0032] The terms "first", "second", etc. in the description and claims are used to distinguish between similar elements and are not necessarily used to describe a specific order or time sequence. It should be understood that, under appropriate circumstances, these terms can be replaced, for example, so that the embodiments of the present invention described herein can be operated in an order different from that described or shown herein. Similarly, if the method described herein includes a series of steps, and the order of these steps presented herein is not necessarily the only order in which these steps can be executed, and some of the described steps can be omitted and / or some other steps not described herein can be added to the method. If the components in a certain drawing are the same as those in other drawings, although these components can be easily recognized in all drawings, for the sake of clearer description of the drawings, this specification will not label the reference numerals of all the same components in each drawing.

[0033] Example 1

[0034] This embodiment provides a manufacturing method of an ultrasonic sensor. The manufacturing method of the ultrasonic sensor includes:

[0035] S01: Provide a substrate, the substrate includes: a first substrate, a bonding layer, the bonding layer is disposed above the first substrate, a cavity is provided in the bonding layer, a piezoelectric vibrator located above the bonding layer, the piezoelectric vibrator includes a vibrating part, the vibrating part is located above the cavity, and the vibrating part includes a second electrode, a piezoelectric film, and a first electrode stacked in sequence from bottom to top;

[0036] S02: Provide a backplane;

[0037] S03: Form a bonding layer on the backplane or on the piezoelectric vibrator;

[0038] S04: Etch the backplane and the bonding layer to form a groove. The groove exposes the piezoelectric vibrator. There is an overlapping part between the projection of the groove and the vibrating part in the first substrate direction. In the longitudinal cross-section perpendicular to the plane of the first substrate, the size of the top of the groove is larger than the size of the bottom of the groove in the direction away from the substrate. The backplane and the bonding layer constitute the second substrate.

[0039] It should be noted that the above steps S0N do not represent the order of sequence.

[0040] Next, please refer to Figures 1 to 17 to describe the manufacturing method of the ultrasonic sensor. Figures 1 to 17 This is a schematic structural diagram corresponding to different steps in an embodiment of the manufacturing method of the ultrasonic sensor of the present invention.

[0041] Refer to Figure 1 , provide a substrate, the substrate includes: a first substrate 30; a bonding layer 24, the bonding layer 24 is disposed above the first substrate 30, and a cavity 25 is provided in the bonding layer 24; a piezoelectric vibrator located above the bonding layer 24, the piezoelectric vibrator includes a vibrating part, the vibrating part is located above the cavity 25, and the vibrating part includes a second electrode 23, a piezoelectric film 22, and a first electrode 21 stacked in sequence from bottom to top.

[0042] Next, please refer to Figures 2 to 10 to describe the manufacturing method of the substrate.

[0043] Refer to Figures 2 to 5 , provide a carrier substrate 10, and form a piezoelectric vibrator on the carrier substrate 10. The piezoelectric vibrator includes a vibrating part.

[0044] Refer to Figure 2 , provide a carrier substrate 10, the material of the carrier substrate 10 includes semiconductor materials such as silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbide (SiC), silicon germanium carbide (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), or other III / V compound semiconductors. It can also be a double-sided polished silicon wafer (DSP), or a ceramic substrate such as alumina, a quartz or glass substrate, etc.

[0045] In this embodiment, after the carrier substrate 10 is formed and before the piezoelectric vibrator is formed, a matching layer 11 is formed on the carrier substrate 10. The material of the matching layer 11 includes one or more combinations of silicon dioxide, silicon nitride, polysilicon, or silicon. In this embodiment, the thickness of the matching layer 11 is an odd multiple of 1 / 4 of the ultrasonic wavelength, and the purpose is to reduce the characteristic impedance, improve the penetration ability of ultrasonic waves in different media, enhance the energy of the emitted ultrasonic waves, and improve the device performance. The matching layer 11 can be formed by chemical vapor deposition, physical vapor deposition, atomic layer deposition, laser ablation deposition, or molecular beam deposition.

[0046] In other embodiments, before the matching layer 11 is formed, an isolation layer (not shown in the figure) is formed on the carrier substrate 10. The material of the isolation layer includes silicon nitride or silicon oxide, and the isolation layer serves as a stop layer for the subsequent thinning process. The isolation layer can be formed by chemical vapor deposition, physical vapor deposition, or atomic layer deposition.

[0047] The method for forming the piezoelectric vibrator includes: forming a first electrode layer on the matching layer 11, patterning the first electrode layer to form the first electrode 21; forming a piezoelectric film 22 to cover the first electrode 21; forming a second electrode layer to cover the piezoelectric film 22, and patterning the second electrode layer to form the second electrode 23.

[0048] In this embodiment, during the process of patterning the first electrode layer to form the first electrode 21, it further includes: forming a first electrode lead-out portion 210 connected to the first electrode 21, and the piezoelectric film 22 also covers the first electrode lead-out portion 210; during the process of patterning the second electrode layer to form the second electrode 23, it further includes: forming a second electrode lead-out portion 230 connected to the second electrode 23.

[0049] Specifically, refer to Figure 3, deposit a first electrode layer on the matching layer 11. The first electrode layer can be a metal material or a semiconductor material with conductive properties. For example, it can be made of one of the metals such as molybdenum (Mo), aluminum (Al), copper (Cu), tungsten (W), tantalum (Ta), platinum (Pt), ruthenium (Ru), rhodium (Rh), iridium (Ir), chromium (Cr), titanium (Ti), gold (Au), osmium (Os), rhenium (Re), palladium (Pd), etc., or a laminate formed by the above metals. The semiconductor material is, for example, Si, Ge, SiGe, SiC, SiGeC, etc. The first electrode layer can be formed by physical vapor deposition such as magnetron sputtering and evaporation, or chemical vapor deposition. After forming the first electrode layer, pattern the first electrode layer to form the first electrode 21 and the first electrode lead-out portion 210. The first electrode lead-out portion 210 is connected to the first electrode 21 and is used to electrically lead out the first electrode 21 and supply power to the first electrode 21. The shape of the first electrode 21 can be any shape, such as circular, rectangular or polygonal, and the shape of the first electrode is based on the criteria of receiving more acoustic waves and not increasing the process difficulty. In this embodiment, the first electrode lead-out portion 210 is strip-shaped and is connected to a part of the edge of the first electrode 21.

[0050] Reference Figure 4 , form a piezoelectric film 22 to cover the first electrode 21, the first electrode lead-out portion 210, and the matching layer 11. The material of the piezoelectric film 22 includes piezoelectric materials with a wurtzite crystal structure such as aluminum nitride (AlN), zinc oxide (ZnO), lead zirconate titanate (PZT), lithium niobate (LiNbO3), quartz (Quartz), potassium niobate (KNbO3), or lithium tantalate (LiTaO3), and their combinations. When the piezoelectric film 22 includes aluminum nitride (AlN), the piezoelectric film 22 may further include rare earth metals, such as at least one of scandium (Sc), erbium (Er), yttrium (Y), and lanthanum (La). In addition, when the piezoelectric film 22 includes aluminum nitride (AlN), the piezoelectric film 22 may further include transition metals, such as at least one of zirconium (Zr), titanium (Ti), manganese (Mn), and hafnium (Hf). The piezoelectric film 22 can be formed by chemical vapor deposition, physical vapor deposition, or atomic layer deposition.

[0051] In other embodiments, in order to improve the quality of the piezoelectric film 22, form a dielectric layer on the matching layer 11. The top of the dielectric layer is flush with the first electrode 21, and the dielectric layer and the first electrode 21 form a flat surface, which is beneficial for the subsequent formation of the piezoelectric film 22 on the flat surface, thereby improving the quality of the piezoelectric film 22, the reliability, and the yield of the sensor.

[0052] Reference Figure 5, a second electrode layer is formed on the piezoelectric film 22. The material and formation method of the second electrode layer refer to the material and formation method of the first electrode layer described above. After the second electrode layer is formed, the second electrode layer is patterned to form a second electrode 23 and a second electrode lead-out portion 230. The second electrode lead-out portion 230 is connected to the second electrode 23 and is used to lead out the electric property of the second electrode 23 and supply power to the second electrode 23. The shape of the second electrode 21 can be any shape, which can be the same as or different from the shape of the first electrode 21. In this embodiment, the second electrode lead-out portion 230 is strip-shaped and is connected to a part of the edge of the second electrode 23. The overlapping area of the first electrode 21, the second electrode 23, and the piezoelectric film 22 in the direction perpendicular to the surface of the carrier substrate 10 is the vibration part (effective working area) of the ultrasonic sensor. In this embodiment, in order to receive more sound waves and without increasing the process difficulty, the first electrode 21 and the second electrode 23 of the vibration part have the same shape and are symmetrically arranged. In this embodiment, the overlapping area of the projections of the first electrode 21, the second electrode 23, and the piezoelectric film 22 in the direction of the surface of the first substrate 30 is within the projection range of the cavity 25 in the direction of the first substrate 30.

[0053] Reference Figures 6 to 7 , a bonding layer 24 is formed to cover the piezoelectric vibrator, and a cavity 25 penetrating the bonding layer 24 is formed above the vibration part.

[0054] Reference Figure 6 , a bonding layer 24 is formed on the piezoelectric film 22, the second electrode 23, and the second electrode lead-out portion 230. The material of the bonding layer 24 includes dielectric materials such as silicon dioxide (SiO2), silicon nitride (Si3N4), and aluminum oxide (Al2O3), and can also be a photolithographic material such as a dry film. When the material of the bonding layer 24 is silicon dioxide (SiO2), silicon nitride (Si3N4), or aluminum oxide (Al2O3), it can be formed by a deposition process. In this embodiment, the material of the bonding layer 24 is a dry film, and it can be formed by a lamination process. The lamination process is carried out in a vacuum environment. By selecting the lamination process, the adhesion and bonding strength between the dry film and the piezoelectric film 22 and the second electrode 23 can be ensured. In other embodiments, the material selected for the bonding layer 24 can also be a liquid dry film. Here, the liquid dry film means that the components in the film-shaped dry film exist in a liquid form. Correspondingly, the bonding layer 24 can be formed by a spin coating process; after the bonding layer 24 is formed, a drying step is also included to cure it. The thickness of the bonding layer 24 is not limited.

[0055] Reference Figure 7, a cavity 25 is formed in the bonding layer 24. When the material of the bonding layer 24 is a non-lithographic material, the cavity 25 can be formed by an etching process (the etching process includes two processes: lithography and etching). In this embodiment, the material of the bonding layer 24 is a lithographic material, and the cavity 25 can be formed by a lithography process, eliminating the etching process after the lithography process, reducing the impact on the bonding strength of the bonding layer, saving process steps at the same time, and shortening the manufacturing cycle. The method of forming the cavity 25 by using the lithography process is as follows: providing a mask plate, and exposing and developing the bonding layer 24 through the mask plate to form the cavity 25 in the bonding layer 24. In this embodiment, the cavity 25 exposes the second electrode 23 and the piezoelectric film 22 outside the second electrode. In other embodiments, the edge of the cavity 25 can be located within the edge of the second electrode 23 without exposing the piezoelectric film 22, and the cavity 25 can also expose a part of the piezoelectric film 22. The shape of the cavity 25 is not limited.

[0056] Reference Figure 8 , a first substrate 30 is formed on the bonding layer 24 to cover the cavity 25. First, the first substrate 30 is provided, and the first substrate 30 is bonded to the bonding layer 24 through a bonding film. The materials of the bonding film include silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride, ethyl silicate or dry film. In this embodiment, the bonding layer 24 is a dry film and can be used as the bonding film, and the first substrate 30 is directly bonded to the piezoelectric vibrator through the bonding layer 24. The material selection of the first substrate 30 refers to the material of the carrier substrate 10, which will not be elaborated here. In subsequent processes, it is necessary to remove the carrier substrate 10, and the first substrate 30 is used to provide the necessary support strength when removing the carrier substrate 10. In this embodiment, the first substrate 30 seals the cavity 25.

[0057] Reference Figure 9 , the carrier substrate 10 is removed to expose the matching layer 11. In this embodiment, the carrier substrate 10 is removed by etching or mechanical grinding. In other embodiments, the isolation layer serves as a stop layer for the grinding process to prevent excessive grinding. In other examples, the carrier substrate 10 can be removed by etching the isolation layer, which helps to quickly peel off the carrier substrate 10 and improve the process production efficiency. In another example, the position of the isolation layer can be replaced with a thermal expansion tape, and the carrier substrate 10 is peeled off by heating to make the thermal expansion tape lose its adhesiveness.

[0058] In this embodiment, the piezoelectric vibrator further includes: a vent hole 301 located in the outer region of the vibrating part and on the side opposite to the first substrate 30, and the vent hole 301 communicates the cavity 25 with the atmosphere.

[0059] Specifically, reference Figure 10, the manufacturing method of the substrate further includes: after removing the carrier substrate 10, an air vent is formed above the cavity 25 on the side opposite to the first substrate 30 and outside the vibration part by using an etching process or a punching process. The air vent 301 can be formed by a dry etching process, and the number of the air vents 301 can be one or more. The shape can be circular or strip-shaped. The purpose of forming the air vent 301 is to make the cavity 25 communicate with the atmosphere, so that the ultrasonic impedance of the air in the cavity 25 is offset by the ultrasonic impedance outside, which is beneficial to making the reception and recognition of ultrasonic signals more accurate, improving the device performance. At the same time, the pressure in the cavity 25 is made consistent with the outside world, preventing the vibration part from deforming due to inconsistent pressures on the two surfaces of the vibration part, and also making the pressure in the cavity controllable in the subsequent process of forming the bonding layer and the backplane, improving the structural strength of the ultrasonic sensor, and improving the reliability and yield. In this embodiment, the first electrical connection structure 211 and the second electrical connection structure 231 are formed first, and then the air vent 301 is formed. In another embodiment, the air vent 301 can also be formed after removing the first substrate and before forming the first electrical connection structure 211 and the second electrical connection structure 231. Or, the air vent 301 can be formed during the process of forming the through hole.

[0060] In this embodiment, it further includes: forming a first electrical connection structure 211 to connect the first electrode lead-out part 210; forming a second electrical connection structure 231 to connect the second electrode lead-out part 230. In this embodiment, the first electrical connection structure 211 and the second electrical connection structure 231 are located outside the cavity 25, and the two are respectively connected to the first electrode lead-out part 210 and the second electrode lead-out part 230 located outside the cavity 25.

[0061] The method of forming the first electrical connection structure 211 includes: after removing the carrier substrate 10, a first through hole is formed on the outside of the cavity 25 and on the side opposite to the first substrate 30, the bottom of the first through hole extends to the first electrode lead-out part 210, and a first conductive material is formed in and around the first through hole. The first electrical connection structure 211 includes the first conductive material formed around the first through hole.

[0062] The method for forming the second electrical connection structure 231 includes: forming a second through hole on the outer side of the cavity 25 and on the side opposite to the first substrate 30, with the bottom of the second through hole extending to the second electrode lead-out portion 230, forming a second conductive material in the second through hole and on the outer periphery of the second through hole, and the second electrical connection structure 231 includes the second conductive material formed on the outer periphery of the second through hole. In this embodiment, the longitudinal cross-section of the first electrical connection structure 211 and the second electrical connection structure 231 is a T-shaped plug, which is formed through two-step processes. First, a part of the electrical material is formed in the through hole by electroplating or deposition processes, then the conductive material is continuously formed on the matching layer 11 by a deposition process, and then the conductive material above the matching layer 11 is patterned, the conductive material on the outer periphery of the through hole is retained, and the conductive material in other regions is removed to form a T-shaped plug.

[0063] In other embodiments, after forming the second substrate 40, the first electrical connection structure 211 and the second electrical connection structure 231 are formed, and the forming methods refer to the foregoing embodiments and will not be elaborated here.

[0064] The methods for forming the first through hole and the second through hole can be through dry etching processes, and the dry etching processes include but are not limited to reactive ion etching (RIE), ion beam etching, plasma etching, or laser cutting. The methods for forming the first conductive material in the first through hole and the second conductive material in the second through hole include deposition processes or electroplating processes. The first conductive material and the second conductive material can be made of one of metals such as aluminum (Al), copper (Cu), tungsten (W), tantalum (Ta), platinum (Pt), ruthenium (Ru), rhodium (Rh), iridium (Ir), chromium (Cr), titanium (Ti), gold (Au), osmium (Os), rhenium (Re), palladium (Pd), etc., or made of a stack layer formed by the above metals.

[0065] Refer to Figure 11 , perform step S02: Provide a backplane 401, and the material of the backplane 401 refers to the first substrate 30 and will not be elaborated here.

[0066] Refer to Figure 12 and Figure 13 , perform step S03: Form a bonding layer 402 on the backplane 401 or on the piezoelectric vibrator. The material of the bonding layer 402 includes dry film, silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride, or ethyl silicate. The bonding layer is used to connect the backplane 401 and the substrate. In this embodiment, the bonding layer 402 is a photolithographic material, such as dry film. By bonding the substrate and the backplane 401 through a bonding process, the combination process of the metal shell and the chip is omitted, improving the packaging efficiency.

[0067] In this embodiment, the bonding layer 402 is a film-shaped dry film, which makes the process of forming the bonding layer simpler. The film-shaped dry film is a sticky photoresist film used in semiconductor chip packaging or printed circuit board manufacturing. The film-shaped dry film is manufactured by coating a solvent-free photoresist on a polyester substrate and then covering it with a polyethylene film; when in use, the polyethylene film is removed, and the solvent-free photoresist is pressed onto the substrate, and after exposure and development, a pattern can be formed in the dry film.

[0068] In this embodiment, the bonding layer 402 is formed by a lamination process. The lamination process is carried out in a vacuum environment. By selecting the lamination process, the adhesion and bonding strength between the bonding layer 402 and the backplane 401 and the substrate are significantly improved.

[0069] Reference Figure 12 The bonding layer 402 can be formed on the backplane 401 or reference Figure 13 The bonding layer 402 is formed on the piezoelectric vibrator. Since a lithographic material is selected to form the bonding layer 402, the process of forming the bonding layer 402 is prevented from having an adverse effect on the substrate, which is beneficial to improving the reliability and yield of the ultrasonic sensor.

[0070] In other embodiments, the material selected for the bonding layer 402 can also be a liquid dry film. Among them, the liquid dry film means that the components in the film-shaped dry film exist in a liquid form. Correspondingly, the bonding layer 402 can be formed by a spin coating process; after the bonding layer 402 is formed, a drying step is also included to cure it. And the cured liquid dry film is also a photosensitive material, and patterning can be achieved through a lithography process.

[0071] In this embodiment, the bonding layer 402 covers the vent hole 301.

[0072] Since there is a vent hole 301 in the piezoelectric vibrator, during the process of forming the bonding layer 402, it is necessary to prevent the bonding layer 402 material from entering the cavity. Therefore, when using a liquid dry film, attention should be paid to the matching of the viscosity of the dry film and the size of the vent hole 301 to avoid contaminating the cavity with the liquid dry film material.

[0073] Reference Figures 14 - 16 , perform step S04: etch the backplane 401 and the bonding layer 402 to form a groove 41. The groove 41 exposes the piezoelectric vibrator. The projection of the groove 41 and the vibrating part in the direction of the first substrate 30 has an overlapping part. In the longitudinal section perpendicular to the plane of the first substrate 30, the top size of the groove 41 is larger than the bottom size of the groove 41 in the direction away from the substrate. The backplane 401 and the bonding layer 402 constitute a second substrate 40.

[0074] In this embodiment, the groove 41 exposes the vent hole 301.

[0075] The vent hole 301 communicates the cavity 25 with the atmosphere, so that the ultrasonic impedance of the air in the cavity 25 cancels out the ultrasonic impedance of the outside, which is beneficial to making the received and recognized ultrasonic signal more accurate, improving the device performance. At the same time, the pressure in the cavity 25 is made consistent with the outside world, preventing the vibration part from deforming due to inconsistent pressures on the two surfaces of the vibration part. It also enables the pressure in the cavity 25 to be controllable during the subsequent formation of the bonding layer 402 and the backplane 401, improving the structural strength of the ultrasonic sensor, and improving the reliability and yield.

[0076] In other embodiments, the groove 41 does not expose the vent hole 301.

[0077] Specifically, referring to Figure 14 , when forming the bonding layer 402 on the piezoelectric vibrator after forming the piezoelectric vibrator, the bonding layer 402 is patterned by photolithography to form the first groove 411. The first groove 411 penetrates the bonding layer 402. Forming the first groove 411 by photolithography of the bonding layer 402 avoids the possible damage to the matching layer 11 during the process of forming the first groove 411 by etching process, ensures the requirement of the matching layer 11 for thickness accuracy, reduces the influence on the bonding strength of the bonding layer 402, and at the same time avoids the adverse effects of the etching process on the substrate, ensuring the bonding strength between layers, which is beneficial to improving the reliability and yield of the ultrasonic sensor. In this embodiment, in the step of forming the first groove 411, the peripheral part of the first groove 411 in the bonding layer 402 is also lithographed to expose the first electrical connection structure 211 and the second electrical connection structure 231 for inputting or outputting electrical signals. In other embodiments, after patterning the bonding layer 402 to form the first groove 411 and lithographing the bonding layer 402 of the peripheral part of the first groove 411, the first electrical connection structure 211 and the second electrical connection structure 231 are formed. For details, refer to the foregoing embodiments and will not be elaborated here.

[0078] Referring to Figure 15 , the backplane 401 is bonded to the opposite side of the first substrate 30 through the bonding layer 402. Referring to Figure 16 , the backplane 401 is patterned by etching process to form the second groove 412. The second groove 412 penetrates the backplane 401. The first groove 411 and the second groove 412 constitute the groove 41, and the groove 41 is located above the vibration part. The backplane 401 and the bonding layer 402 constitute the second substrate 40. In this embodiment, the second substrate 40 exposes the first electrical connection structure 211 and the second electrical connection structure 231 for inputting or outputting electrical signals.

[0079] When forming the bonding layer 402 on the backplane 401, the first groove 411 is formed by a photolithography process. At this time, it is also not necessary to form the first groove 411 by an etching process, which ensures the thickness accuracy requirements of the bonding layer 402 and reduces the impact on the bonding strength of the bonding layer 402. Refer to Figure 15 , after forming the piezoelectric vibrator, bond the backplane 401 and the substrate, and then etch the backplane 401 to form the second groove 412, forming the groove 41 as shown in Figure 16 .

[0080] In another embodiment, refer to Figure 17 , on the basis of Figure 13 , form the backplane 401 on the bonding layer 402. Refer to Figure 16 , pattern the backplane 401 by an etching process to form the second groove 412, then pattern the bonding layer 402 by a photolithography process to form the first groove 411, and then perfect the shape and size of the groove by a trimming process to form the groove 41.

[0081] In other embodiments, the material of the bonding layer 402 includes silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride or ethyl silicate. When the material of the bonding layer 402 is an inorganic material such as silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride or ethyl silicate, the bonding layer 402 is formed by a deposition process. Specifically, in a vacuum or low-pressure gas atmosphere, the bonding layer 402 is deposited by an LPCVD or PECVD process.

[0082] At this time, the method for forming the groove 41 includes: providing the backplane 401, forming the bonding layer 402 on the surface of the backplane 401 or on the piezoelectric vibrator after forming the piezoelectric vibrator, bonding the backplane 401 to the substrate through the bonding layer 402, and forming the groove 41 as shown in Figure 16 by an etching process on the backplane 401 and the bonding layer 402. The groove 41 is located above the vibrating part and penetrates through the backplane 401 and the bonding layer 402. In other embodiments, after forming the bonding layer 402 on the backplane 401, before bonding the backplane 401 and the substrate, the etching process of the backplane 401 and the bonding layer 402 can be completed to etch out the groove 41, and then the backplane 401 is bonded to the substrate through the bonding layer 402.

[0083] The groove 41 can expose all or part of the vibrating portion of the piezoelectric vibrator. When the groove 41 exposes all of the vibrating portion of the piezoelectric vibrator, the bonding layer 402 will cover or partially cover the vent hole 301. At this time, the cavity 25 communicates with the outside, and there is no pressure difference inside and outside the vibrating portion, which can ensure the structural strength of the ultrasonic sensor and improve the yield. When the groove 41 exposes part of the vibrating portion of the piezoelectric vibrator, the bonding layer 402 will cover or partially cover the vent hole 301. When the vent hole 301 is covered, the cavity 25 is a sealed cavity, which can prevent the structures inside the cavity 25 from being contaminated by dust, moisture, and grease, and improve the quality of the sensor.

[0084] In this embodiment, the projection of the groove 41 in the direction of the first substrate 30 surrounds the projection of the vibrating portion in the direction of the first substrate 30, and the projection of the bottom surface of the groove 41 in the direction of the first substrate 30 is also located within the area surrounded by the cavity 25. The cross-sectional shape of the groove 41 is wider at the top and narrower at the bottom, and the shape is trumpet-shaped. The side wall of the groove is an inclined plane, an arc surface, or a stepped shape. In this embodiment, the cross-sectional shape of the groove 41 is trapezoidal, and the three-dimensional structure is a conical trumpet shape, which can concentrate the energy of transmitting and receiving ultrasonic waves. In this embodiment, the second substrate 40 exposes the first electrical connection structure 211 and the second electrical connection structure 231 to facilitate the input or output of electrical signals.

[0085] Example 2

[0086] Embodiment 2 of the present invention provides an ultrasonic sensor. Figure 16 The structural schematic diagram of the ultrasonic sensor of this embodiment is shown. Please refer to Figure 16 , the ultrasonic sensor includes:

[0087] A first substrate 30 and a bonding layer 24 located above the first substrate 30, and a cavity 25 is provided in the bonding layer 24;

[0088] A piezoelectric vibrator located above the bonding layer 24. The piezoelectric vibrator includes a vibrating portion, and the vibrating portion is located above the cavity 25. The vibrating portion includes a second electrode 23, a piezoelectric film 22, and a first electrode 21 stacked in sequence from bottom to top. In this embodiment, the projection of the vibrating portion in the direction of the first substrate 30 is located within the projection of the cavity 25 in the direction of the first substrate 30;

[0089] A second substrate 40 is disposed on the piezoelectric vibrator. The second substrate 40 includes a bonding layer 402 and a back plate 401 stacked in sequence from bottom to top. A groove 41 is provided in the second substrate 40. The groove 41 exposes the piezoelectric vibrator. The groove 41 and the projection of the vibrating portion in the direction of the first substrate 30 have an overlapping part. In the longitudinal cross-section perpendicular to the plane where the first substrate 30 is located, the top size of the groove 41 is larger than the bottom size of the groove 41 in the direction away from the substrate.

[0090] In this embodiment, the projection of the second substrate 40 in the direction of the first substrate 30 surrounds the projection of the vibrating part in the direction of the first substrate 30, and the projection of the bottom surface of the groove 41 in the direction of the first substrate 30 is also located within the area surrounded by the cavity 25. The cross-sectional shape of the groove 41 is wider at the top and narrower at the bottom, and is in the shape of a horn. The side wall of the groove 41 is an inclined plane, an arc surface or a stepped shape. In this embodiment, the cross-sectional shape of the groove 41 is trapezoidal, and the three-dimensional structure is a conical horn shape, which can concentrate the energy of transmitting and receiving ultrasonic waves.

[0091] In this embodiment, it further includes a vent hole 301, which is arranged on the side opposite to the first substrate 30. One end of the vent hole 301 communicates with the cavity 25, and the other end extends to the surface of the second substrate 40 close to the cavity 25, or the other end communicates with the atmosphere. The bonding layer 402 after forming the groove 41 can cover the vent hole 301 or expose the vent hole 301. When the vent hole 301 is covered, the cavity 25 is a sealed cavity, which can prevent the structures inside the cavity 25 from being polluted by dust, moisture and grease. When the vent hole 301 is not covered or partially covered, the cavity 25 communicates with the outside, and there is no pressure difference inside and outside the vibrating part, which can ensure the structural strength of the ultrasonic sensor and improve the yield.

[0092] In other embodiments, it further includes a matching layer 11, and the matching layer 11 is arranged between the piezoelectric vibrator and the second substrate 40.

[0093] Regarding the materials, structures and positional relationships of the first substrate 30, the second substrate 40, the matching layer 11, the first electrode 21, the second electrode 23, the piezoelectric film 22, the bonding layer 24, the first electrode lead-out part 210, the second electrode lead-out part 230, the first electrical connection structure 211 and the second electrical connection structure 231, refer to the corresponding parts in the foregoing method embodiment. Regarding the structures of the cavity 25, the vent hole 301 and the groove 41, also refer to the corresponding parts in the foregoing method embodiment, and will not be elaborated here.

[0094] The present invention provides a method for forming a groove, a bonding backplane and a substrate. By completing the formation process of the bonding layer on the backplane or the substrate, the substrate and the backplane are bonded through a bonding process, and when the bonding layer is formed on the backplane and the groove is etched, it is possible to avoid possible damage to the matching layer during the process of forming the groove by the etching process.

[0095] Furthermore, when using a photolithographic material such as a dry film to form the bonding layer, the groove in the bonding layer is formed through a photolithography process, which avoids possible damage to the matching layer during the process of forming the groove by the etching process, ensures the requirement of the matching layer for thickness accuracy, reduces the influence on the bonding strength of the bonding layer, and at the same time avoids adverse effects of the etching process on the substrate, ensures the bonding strength between layers, and is beneficial to improving the reliability and yield of the ultrasonic sensor.

[0096] Furthermore, by forming a bonding layer with a cavity above the piezoelectric vibrator, forming a first substrate on the bonding layer to cover the cavity, and forming air vents on the outer periphery of the vibrating portion to connect the cavity and the outside, the pressures on the upper and lower surfaces of the vibrating portion are made consistent, preventing the vibrating portion from deforming or cracking due to atmospheric pressure. Also, the pressure inside the cavity can be controlled during the subsequent formation of the bonding layer and the backplane, improving the structural strength of the ultrasonic sensor, as well as the reliability and yield rate.

[0097] Furthermore, when the material of the bonding layer is a dry film, the dry film can be formed on the piezoelectric film and the second electrode through a film laminating process, improving the adhesion and bonding strength of the contact surface and enhancing the reliability.

[0098] Furthermore, the cavity is formed by lithographing the bonding layer. The lithography process reduces the impact on the bonding strength of the bonding layer, simplifies the process flow, and improves the packaging efficiency.

[0099] It should be noted that each embodiment in this specification is described in a related manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the structural embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and reference can be made to the corresponding parts of the method embodiments for the relevant content.

[0100] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention in any way. Any changes and modifications made by those of ordinary skill in the art of the present invention based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A manufacturing method of an ultrasonic sensor, characterized in that, Comprising: Providing a substrate, the substrate comprising: A first substrate, A bonding layer disposed above the first substrate, and a cavity is provided in the bonding layer, A piezoelectric vibrator located above the bonding layer, the piezoelectric vibrator comprising a vibrating portion located above the cavity, and the vibrating portion includes a second electrode, a piezoelectric film, and a first electrode stacked in sequence from bottom to top; Providing a backplane; Forming a bonding layer on the backplane or on the piezoelectric vibrator; Bonding the backplane to the substrate through the bonding layer; Etching the backplane and the bonding layer to form a groove, the groove exposing the piezoelectric vibrator, and a part of the projection of the groove on the first substrate direction overlaps with the vibrating portion. In a longitudinal cross-section perpendicular to the plane of the first substrate, the top dimension of the groove is larger than the bottom dimension of the groove in the direction away from the substrate, and the backplane and the bonding layer constitute a second substrate.

2. The manufacturing method of the ultrasonic sensor according to claim 1, characterized in that, The material of the bonding layer includes: dry film, silicon oxide, silicon nitride, silicon oxynitride, silicon carbonitride, or ethyl silicate.

3. The manufacturing method of the ultrasonic sensor according to claim 1, characterized in that, The method for forming the groove includes: After forming the piezoelectric vibrator, providing the backplane, forming the bonding layer on the surface of the backplane or on the side opposite to the first substrate, and bonding the backplane to the opposite side of the first substrate through the bonding layer, Forming the groove on the backplane and the bonding layer through an etching process, and the groove is located above the vibrating portion and penetrates through the backplane and the bonding layer; Or, After forming the piezoelectric vibrator, providing the backplane, forming the bonding layer on the surface of the backplane or on the side opposite to the first substrate, the material of the bonding layer is a photolithographic material, and the photolithographic material includes a dry film. Pattern the bonding layer through a photolithography process to form a first groove, and the first groove penetrates through the bonding layer, Bonding the backplane to the opposite side of the first substrate through the bonding layer, Pattern the backplane through an etching process to form a second groove, and the second groove penetrates through the backplane. The first groove and the second groove constitute the groove, and the groove is located above the vibrating portion.

4. The manufacturing method of the ultrasonic sensor according to claim 1, characterized in that, The shape of the longitudinal cross-section of the groove is a horn shape, and the side wall of the groove is an inclined plane, an arc surface, or a stepped shape.

5. The manufacturing method of the ultrasonic sensor according to claim 1, characterized in that, The projection of the groove on the first substrate direction surrounds the projection of the vibrating portion on the first substrate direction.

6. The manufacturing method of the ultrasonic sensor according to claim 1, characterized in that, The piezoelectric vibrator further includes: a vent hole located in the outer region of the vibrating portion and on the side opposite to the first substrate, and the vent hole communicates the cavity with the atmosphere.

7. The manufacturing method of the ultrasonic sensor according to claim 6, characterized in that, The bonding layer covers the vent hole.

8. The manufacturing method of the ultrasonic sensor according to claim 1, characterized in that, Further comprising: Forming a matching layer on the surface of the piezoelectric vibrator before bonding the backplane to the substrate through the bonding layer.

9. The manufacturing method of the ultrasonic sensor according to claim 8, characterized in that, The material of the matching layer includes: one or more combinations of silicon oxide, silicon nitride, polysilicon, or silicon.

10. The manufacturing method of the ultrasonic sensor according to claim 1, characterized in that, The manufacturing method of the substrate includes: Providing a carrier substrate, and forming the piezoelectric vibrator on the carrier substrate, and the piezoelectric vibrator includes the vibrating portion; Form the bonding layer to cover the piezoelectric vibrator, and form the cavity penetrating the bonding layer above the vibrating portion; Form the first substrate on the bonding layer to cover the cavity; Remove the carrier substrate.

11. The manufacturing method of the ultrasonic sensor according to claim 10, characterized in that, The method for manufacturing the substrate further includes: after removing the carrier substrate, on the side opposite to the first substrate and outside the vibrating portion, form a vent hole above the cavity by using an etching process or a punching process.

12. The manufacturing method of the ultrasonic sensor according to claim 10, characterized in that, After forming the carrier substrate and before forming the piezoelectric vibrator, it further includes: forming a matching layer on the carrier substrate, and the method for forming the matching layer includes: chemical vapor deposition, physical vapor deposition, atomic layer deposition, laser ablation deposition, or molecular beam deposition.

13. The manufacturing method of the ultrasonic sensor according to claim 10, characterized in that, The material of the bonding layer is a photolithographic material, and the photolithographic material includes: dry film.

14. The manufacturing method of the ultrasonic sensor according to claim 13, characterized in that, The method for forming the cavity includes: Form the bonding layer on the piezoelectric vibrator by using a film laminating or spin coating process; Provide a mask plate, and expose and develop the bonding layer through the mask plate to form the cavity in the bonding layer, and the cavity penetrates the bonding layer.

15. The manufacturing method of the ultrasonic sensor according to claim 10, characterized in that, The piezoelectric vibrator further includes: A first electrode lead-out portion, connected to the first electrode and extending out of the cavity; A second electrode lead-out portion, connected to the second electrode and extending out of the cavity; The forming of the piezoelectric vibrator includes: Form a first electrode layer on the carrier substrate, pattern the first electrode layer to form the first electrode and the first electrode lead-out portion connected to the first electrode; Form a piezoelectric film to cover the first electrode and the first electrode lead-out portion; Form a second electrode layer to cover the piezoelectric film, pattern the second electrode layer to form the second electrode and the second electrode lead-out portion connected to the second electrode.

16. The manufacturing method of the ultrasonic sensor according to claim 15, characterized in that, The forming of the piezoelectric vibrator further includes: forming a first electrical connection structure to connect the first electrode lead-out portion; and / or, forming a second electrical connection structure to connect the second electrode lead-out portion; The forming of the first electrical connection structure includes: after removing the carrier substrate, form a first through hole on the outside of the cavity and on the side opposite to the first substrate, the bottom of the first through hole extends to the first electrode lead-out portion, and form a first conductive material in and around the first through hole, and the first electrical connection structure includes the first conductive material; The forming of the second electrical connection structure includes: after removing the carrier substrate, form a second through hole on the outside of the cavity and on the side opposite to the first substrate, the bottom of the second through hole extends to the second electrode lead-out portion, and form a second conductive material in and around the second through hole, and the second electrical connection structure includes the second conductive material.

17. An ultrasonic sensor, characterized in that, It includes: A first substrate and a bonding layer located above the first substrate, and a cavity is provided in the bonding layer; A piezoelectric vibrator located above the bonding layer, the piezoelectric vibrator includes a vibrating portion, the vibrating portion is located above the cavity, and the vibrating portion includes a second electrode, a piezoelectric film, and a first electrode stacked in sequence from bottom to top; The second substrate is disposed on the piezoelectric vibrator. The second substrate includes a bonding layer and a backplane stacked in sequence from bottom to top. A groove is provided in the second substrate, and the groove exposes the piezoelectric vibrator. A part of the projection of the groove and the vibrating portion in the direction of the first substrate overlaps. In a longitudinal cross-section perpendicular to the plane where the first substrate is located, the size of the top of the groove is larger than the size of the bottom of the groove in a direction away from the first substrate.

18. The ultrasonic sensor according to claim 17, characterized in that, The shape of the longitudinal cross-section of the groove is a horn shape, and the side wall of the groove is an inclined plane, an arc surface or a stepped shape.

19. The ultrasonic sensor according to claim 17, wherein The projection of the second substrate in the direction of the first substrate surrounds the projection of the vibrating portion in the direction of the first substrate.

20. The ultrasonic sensor according to claim 17, wherein An air vent hole is further included and is disposed on a side opposite to the first substrate. One end of the air vent hole communicates with the cavity, and the other end extends to the surface of the second substrate close to the cavity or communicates with the atmosphere at the other end.

Images