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CN-122007005-A - Non-constant diameter cavity membrane structure back cavity emission type piezoelectric miniature ultrasonic transducer and manufacturing method thereof

CN122007005ACN 122007005 ACN122007005 ACN 122007005ACN-122007005-A

Abstract

The invention discloses a back cavity emission type piezoelectric miniature ultrasonic transducer with a non-constant diameter cavity membrane structure and a manufacturing method thereof, belonging to the field of miniature ultrasonic transducers, comprising a substrate, a back cavity and a vibrating membrane with a single end shielding the back cavity are arranged on the substrate, an air cavity is arranged between the substrate and the vibrating diaphragm, the air cavity is communicated with the back cavity, the radial contour of the air cavity is larger than that of the back cavity, and the back cavity is in the axial projection range of the air cavity. The invention can obtain better comprehensive balance between sensitivity and sound pressure, inhibit edge displacement of high-order modes, improve stability of vibration boundary, improve acoustic energy coupling efficiency of main modes, improve unimodal characteristic of emission waveform and signal purity, flexibly adjust effective acoustic radiation area and air spring stiffness of back cavity, improve far-field sound pressure, enhance ultrasonic radiation capability of transducer, expand achievable working bandwidth, improve process tolerance, make device insensitive to back erosion diameter deviation, thereby improving consistency and reliability of device.

Inventors

  • LI GUOQIANG
  • YI XINYAN
  • Qian Yingda

Assignees

  • 广州市艾佛光通科技有限公司

Dates

Publication Date
20260512
Application Date
20260416

Claims (10)

  1. 1. The utility model provides a miniature ultrasonic transducer of non-constant diameter chamber membrane structure back of body chamber emission formula piezoelectricity, includes substrate (100), be provided with back of body chamber (103) and single end on substrate (100) shelter from vibrating diaphragm (101) of back of body chamber (103), a serial communication port, substrate (100) with be provided with air chamber (102) between vibrating diaphragm (101), air chamber (102) intercommunication back of body chamber (103), the radial profile of air chamber (102) is greater than the radial profile of back of body chamber (103), back of body chamber (103) are in the axial projection scope of air chamber (102).
  2. 2. The non-constant diameter cavity membrane structure back cavity emission type piezoelectric miniature ultrasonic transducer according to claim 1, wherein the diaphragm (101) is provided with a piezoelectric oscillation stack on one surface facing away from the back cavity (103), and the area of the piezoelectric oscillation stack is smaller than that of the diaphragm (101).
  3. 3. The non-constant diameter cavity membrane structure back cavity emission type piezoelectric miniature ultrasonic transducer according to claim 2, wherein a central hole (109) communicated with the back cavity (103) is arranged on the vibrating membrane (101), and the central hole (109) penetrates through the vibrating membrane (101) and the piezoelectric vibration stack.
  4. 4. The non-constant diameter cavity membrane structure back cavity emission type piezoelectric miniature ultrasonic transducer according to claim 2, wherein the piezoelectric oscillation stack sequentially comprises a bottom electrode (300), a piezoelectric thin film layer (400) and a top electrode (500) from the direction close to the back cavity (103) to the direction far away from the back cavity (103), and a joint overlapping position of the bottom electrode (300), the piezoelectric thin film layer (400) and the top electrode (500) is located in an axial projection range of the back cavity (103).
  5. 5. The non-constant diameter cavity film structure back cavity emission type piezoelectric miniature ultrasonic transducer according to claim 4, characterized in that the substrate (100) is provided with a pad area on one side close to the piezoelectric oscillation stack, the pad area is outside the axial projection of the air cavity (102), the piezoelectric oscillation stack is provided with an extension section (107) connected to the pad area, the pad area is provided with a first pad (108) and a second pad (106) which are not overlapped with each other, the piezoelectric thin film layer (400) and the top electrode (500) are connected to the first pad (108) through the extension section (107), and the bottom electrode (300) is connected to the second pad (106) through the extension section (107).
  6. 6. The non-equal-diameter cavity film structure back cavity emission type piezoelectric miniature ultrasonic transducer according to claim 2, wherein a first protection layer (600) is arranged on one surface of the piezoelectric oscillation stack far away from the back cavity (103), a second protection layer (601) is arranged on one surface of the substrate (100) close to the piezoelectric oscillation stack, and materials of the first protection layer (600) and the second protection layer (601) are respectively and independently selected from one of aluminum nitride, silicon oxide, silicon carbide and silicon nitride.
  7. 7. The non-equal diameter cavity membrane structured back cavity transmitting piezoelectric miniature ultrasonic transducer according to claim 1, wherein the radial cross section of the back cavity (103) is circular, and the radial cross section of the air cavity (102) is circular or rectangular.
  8. 8. The non-constant diameter cavity membrane structure back cavity emission type piezoelectric miniature ultrasonic transducer according to claim 1, wherein the radial cross section of the back cavity (103) is increased from small to large except for the area on the same plane with the air cavity (102) in the direction of approaching the diaphragm (101) to be away from the diaphragm (101).
  9. 9. The non-equal-diameter cavity membrane structured back cavity emission type piezoelectric miniature ultrasonic transducer according to claim 1, wherein the thickness of the air cavity (102) is 0.2 μm to 1.5 μm.
  10. 10. The manufacturing method of the back cavity emission type piezoelectric miniature ultrasonic transducer with the non-constant diameter cavity membrane structure is characterized by comprising the following steps of: Constructing a sacrificial layer (110) on the surface of the substrate (100); etching a ring groove (111) on the sacrificial layer (110); depositing a diaphragm (101) on the sacrificial layer (110), while the ring groove (111) is deposited as an annular stop grid (112); etching the substrate (100) from the side without the vibrating diaphragm (101) to the sacrificial layer (110), wherein the etching range is within the axial projection range of the stop grid (112) to obtain a back cavity (103); And removing the sacrificial layer (110) in the surrounding range of the stop grid (112) through the back cavity (103) to obtain an air cavity (102).

Description

Non-constant diameter cavity membrane structure back cavity emission type piezoelectric miniature ultrasonic transducer and manufacturing method thereof Technical Field The invention relates to a back cavity emission type piezoelectric miniature ultrasonic transducer with a non-constant diameter cavity membrane structure and a manufacturing method thereof, belonging to the field of miniature ultrasonic transducers. Background The ultrasonic transducer is one of core devices in the fields of ultrasonic sensing and detection, is widely applied to the fields of smart phones, intelligent houses, automobile auxiliary driving, unmanned aerial vehicles, industrial detection and the like, and plays an important role in distance measurement, obstacle detection, space modeling and acoustic imaging. With the rapid development of intelligent terminals and automation equipment, people put higher demands on ultrasonic sensors, namely, realizing a longer detection distance and higher measurement accuracy under the conditions of smaller volume and lower power consumption. The traditional ultrasonic transducer mostly adopts a film forward (forward) transmitting structure, and sound waves mainly propagate from the front surface of the diaphragm. In order to obtain higher sound pressure output under the same driving condition, sound waves are mainly transmitted along the opening direction of the cavity to improve directivity, the size of the module is reduced, and a novel back cavity emission design can be adopted. The structure of such back cavity emission designs is typically composed of a "diaphragm + back cavity". At present, the design also has the problems of limited acoustic coupling efficiency, over high quality factor, narrow bandwidth, weak process deviation resistance, limited sound pressure and the like, and the structural design of the design is needed to be optimized. Disclosure of Invention In order to overcome the defects of the prior art, the invention provides a back cavity emission type piezoelectric miniature ultrasonic transducer with a non-equal-diameter cavity membrane structure and a manufacturing method thereof, so as to solve the problems of narrow bandwidth, insufficient sound pressure, sensitivity to process deviation, serious high-order modal interference and the like in the prior art. The technical scheme adopted for solving the technical problems is as follows: In a first aspect, the application provides a back cavity emission type piezoelectric miniature ultrasonic transducer with a non-equal-diameter cavity membrane structure, which comprises a substrate, wherein a back cavity and a membrane with a single end shielding the back cavity are arranged on the substrate, an air cavity is arranged between the substrate and the membrane, the air cavity is communicated with the back cavity, the radial contour of the air cavity is larger than that of the back cavity, and the back cavity is in the axial projection range of the air cavity. According to the back cavity emission type piezoelectric miniature ultrasonic transducer with the non-equal-diameter cavity membrane structure, the suspension area of the vibrating membrane is larger than the radial sectional area of the back cavity, and a solid supporting area (the direct connection position of the substrate and the vibrating membrane) is arranged at the edge of the vibrating membrane, so that a differential coupling area is formed between the back cavity and the vibrating membrane, and the acoustic energy distribution and the air spring effect are effectively regulated and controlled, so that the broadband characteristic is realized, the emission sound pressure is improved, and the high-order mode is restrained. Meanwhile, the size of the vibrating diaphragm and the size of the back cavity can be set according to different performance requirements, so that the mechanical vibration characteristic of the transducer and the acoustic response of the back cavity can be regulated and controlled respectively without limitation, and the overall acoustic performance and the design freedom degree are effectively improved. The method is suitable for various scenes such as distance measurement, robot perception, gesture recognition, gas detection and the like. Further, the vibrating diaphragm is provided with a piezoelectric oscillation stack on one surface deviating from the back cavity, and the area of the piezoelectric oscillation stack is smaller than that of the vibrating diaphragm. Further, a central hole communicated with the back cavity is formed in the vibrating diaphragm, and the central hole penetrates through the vibrating diaphragm and the piezoelectric vibrating pile. Further, the piezoelectric oscillation stack sequentially comprises a bottom electrode, a piezoelectric film layer and a top electrode from a direction close to the back cavity to a direction far away from the back cavity, and the joint overlapping position of the bottom electrode, the