Ultrasonic Flight Sensor and Its Manufacturing Method

Abstract

The present invention provides an ultrasonic flight sensor and a manufacturing method thereof, including a cavity disposed in a semiconductor substrate, an excitation layer disposed above the cavity and having a patterned design, and an elastic film covering the cavity and wrapping the patterned excitation layer. Among them, the excitation layer includes a first electrode layer, a second electrode layer, and a piezoelectric layer disposed between the first electrode layer and the second electrode layer. The present invention realizes the miniaturization of the ultrasonic flight sensor, so that the produced ultrasonic flight sensor can achieve the expected performance. Further, the present invention opens holes in the edge region of the elastic film corresponding to the cavity, which is beneficial to reducing the influence of the elastic film stress on the frequency of the ultrasonic flight sensor.

Description

Technical Field

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

[0002] Ultrasonic sensors are widely used in fields such as consumer electronics, robots, drones, and medical instruments. For example, they can measure distance, track position, detect people, avoid obstacles for robots, and perform medical imaging. As a device for converting electrical energy and mechanical energy into each other, an ultrasonic transducer is an important component of an ultrasonic sensor. Traditional ultrasonic transducers are usually made based on mechanical processing, thus having disadvantages such as a relatively large volume, low processing accuracy, high processing cost, and difficulty in forming an array structure.

[0003] A piezoelectric micromachined ultrasonic transducer (PMUT) is composed of an elastic membrane, a piezoelectric layer, and upper and lower metal electrodes. It uses the bending vibration mode of the elastic membrane to transmit and receive ultrasonic waves, and has advantages such as a low driving voltage, a low output impedance, and a balanced transmitting and receiving efficiency. The piezoelectric micromachined ultrasonic transducer can be fabricated using semiconductor processes to realize the miniaturization of the piezoelectric conversion micromachined ultrasonic transducer. Therefore, it is beneficial to the miniaturization of an ultrasonic flight sensor using the piezoelectric micromachined ultrasonic transducer.

[0004] An ultrasonic flight sensor can be used for distance measurement, position tracking, contactless identification, and contactless detection and imaging of 3D images and topography. Compared with optical sensors or infrared sensors, it has many advantages. It is not easily affected by the external environment, such as the influence of ambient light. These advantages all make the application prospect of the ultrasonic flight sensor bright.

[0005] Currently, the production of ultrasonic flight sensors using semiconductor processes is still under research, and there are no actual mass-produced product cases. How to produce and fabricate an ultrasonic flight sensor that can achieve the expected functions and performance and mass-produce it will be the ultimate goal of the research on ultrasonic flight sensors. Summary of the Invention

[0006] The purpose of the present invention is to provide an ultrasonic flight sensor and a manufacturing method thereof, on the premise of realizing the miniaturization of the ultrasonic flight sensor, so that the produced ultrasonic flight sensor can achieve the expected performance.

[0007] To achieve the above purpose, the present invention provides an ultrasonic flight sensor fabricated using semiconductor processes, including:

[0008] A cavity, the cavity being disposed in a semiconductor substrate;

[0009] An excitation layer is disposed above the cavity. The excitation layer includes a first electrode layer, a second electrode layer, and a piezoelectric layer disposed between the first electrode layer and the second electrode layer. The excitation layer is patterned.

[0010] An elastic membrane covers the cavity and wraps the patterned excitation layer.

[0011] Optionally, the elastic membrane is provided with an opening, and the opening penetrates the elastic membrane and communicates with the cavity.

[0012] Optionally, the opening is disposed in the central region of the elastic membrane corresponding to the cavity.

[0013] Optionally, the opening is symmetrically disposed in the edge region of the elastic membrane corresponding to the cavity.

[0014] Optionally, the patterned shapes of the first electrode layer, the second electrode layer, and the piezoelectric layer are the same or similar.

[0015] Optionally, the main part of the patterned excitation layer is disposed around the central region of the cavity.

[0016] Optionally, the excitation layer further includes at least two ribs, the ribs are symmetrically disposed around the main part of the excitation layer, and the ribs extend from the main part to the peripheral part of the cavity.

[0017] Optionally, at least one of the ribs is connected to the main part of the excitation layer and extends to the peripheral part of the cavity to lead out the first electrode layer and the second electrode layer.

[0018] Optionally, it further includes a first electrical contact hole and a second electrical contact hole disposed outside the cavity; the first electrical contact hole and the second electrical contact hole are respectively electrically connected to the first electrode layer and the second electrode layer in the ribs.

[0019] Optionally, the first electrical contact hole and the second electrical contact hole are filled with a conductive material and are respectively electrically connected to the first electrode layer and the second electrode layer in the nearby excitation layer.

[0020] Optionally, the excitation layer further includes ribs symmetrically disposed with the main part of the excitation layer, and the symmetrically disposed ribs are insulated from the first electrode layer and the second electrode layer of the main part of the excitation layer.

[0021] The present invention provides an ultrasonic flight sensor, which is fabricated using semiconductor processes and the ultrasonic flight sensor includes:

[0022] A cavity, the cavity is disposed in a semiconductor substrate;

[0023] A patterned excitation layer, the projected area of the excitation layer located above the cavity on the cavity is smaller than the cavity;

[0024] An elastic membrane, the elastic membrane above the cavity is attached to the surface of the patterned excitation layer, and the elastic membrane outside the cavity is in contact with the semiconductor substrate.

[0025] Optionally, the excitation layer located above the cavity includes a main part and a branch part, and the main part of the excitation layer is distributed in the middle of the cavity.

[0026] Optionally, the branch part of the excitation layer is distributed in the part of the cavity close to the edge.

[0027] Optionally, the branch part of the excitation layer is symmetrically distributed around the main part of the excitation layer.

[0028] Correspondingly, the present invention also provides a manufacturing method of an ultrasonic flight sensor, using a wafer and semiconductor processes to manufacture the ultrasonic flight sensor, and the manufacturing method includes:

[0029] Form a first part of the elastic membrane on the surface of the wafer, and a patterned sacrificial layer is formed in the middle of the first part of the elastic membrane;

[0030] Form an excitation layer on the surface of the first part of the elastic membrane and pattern the excitation layer;

[0031] Form a second part of the elastic membrane on the surface of the excitation layer; and

[0032] Form the cavity of the ultrasonic flight sensor by etching through the wafer, a part of the first part of the elastic membrane close to the wafer surface, and the sacrificial layer from the back of the wafer.

[0033] Optionally, the manufacturing of the excitation layer includes:

[0034] Manufacture a first electrode layer;

[0035] Manufacture a piezoelectric layer on the manufactured first electrode layer;

[0036] Manufacture a second electrode layer on the manufactured piezoelectric layer.

[0037] Optionally, patterning the excitation layer includes:

[0038] The shapes of the patterned first electrode layer, the piezoelectric layer, and the second electrode layer are the same or similar.

[0039] Optionally, forming the first part of the elastic membrane includes:

[0040] Form a protective layer closely attached to the surface of the wafer;

[0041] Form the sacrificial layer on the surface of the protective layer;

[0042] Pattern the sacrificial layer;

[0043] Form a passivation layer on the surface of the patterned sacrificial layer.

[0044] Optionally, the first part of the elastic film is the protective layer formed closely on the surface of the wafer, and the passivation layer is closely attached to the excitation layer.

[0045] Optionally, the size of the patterned sacrificial layer is larger than the size of the cavity formed subsequently in the wafer.

[0046] Optionally, before manufacturing the excitation layer, a sacrificial layer is further manufactured on the surface of the semiconductor substrate.

[0047] Optionally, after manufacturing the cavity, it further includes: removing the sacrificial layer.

[0048] Optionally, it further includes making an opening in the part of the elastic film covering the cavity.

[0049] Optionally, it further includes making a first electrical contact hole and a second electrical contact hole on the elastic film and the excitation layer in the peripheral part of the cavity.

[0050] Optionally, it further includes filling the first electrical contact hole and the second electrical contact hole with a conductive material, so that the first electrical contact hole is electrically connected to the first electrode layer of the excitation layer, and the second electrical contact hole is electrically connected to the second electrode layer of the excitation layer.

[0051] In summary, the present invention provides an ultrasonic flight sensor and its manufacturing method, including a cavity arranged on a semiconductor substrate, an excitation layer arranged above the cavity and designed in a patterned manner, and an elastic film covering the cavity and wrapping the excitation layer. Among them, the excitation layer includes a first electrode layer, a second electrode layer, and a piezoelectric layer arranged between the first electrode layer and the second electrode layer. On the premise of miniaturizing the ultrasonic flight sensor, the present invention enables the produced ultrasonic flight sensor to achieve the expected performance.

[0052] Furthermore, the present invention opens an opening in the edge area of the elastic film corresponding to the cavity, which is beneficial to reducing the influence of the elastic film stress on the frequency of the ultrasonic flight sensor. Description of the Drawings

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the accompanying 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 accompanying drawings can be obtained based on these drawings.

[0054] Figure 1 The top view of the partial structure of the ultrasonic flight sensor provided in Embodiment 1 of the present invention;

[0055] Figure 2a For Figure 1 The schematic cross-sectional view of the structure in along the AA' and BB' directions; Figure 2b For Figure 1 The schematic cross-sectional structure view along the CC' direction;

[0056] Figure 3 The flowchart of the manufacturing method of the ultrasonic flight sensor provided in the embodiment of the present invention;

[0057] Figures 4a to 4k The schematic structural view of the corresponding steps of the manufacturing method of the ultrasonic flight sensor provided in Embodiment 1 of the present invention, where 4a to Figure 4k For the corresponding steps Figure 1 The schematic cross-sectional view of the structure in along the AA' and BB' directions;

[0058] Figure 5 The top view of the partial structure of the ultrasonic flight sensor provided in Embodiment 2 of the invention;

[0059] Figure 6 For Figure 5 The schematic cross-sectional view of the structure in along the AA' and BB' directions;

[0060] Figure 7 The top view of the partial structure of the ultrasonic flight sensor provided in Embodiment 3 of the invention;

[0061] Figure 8 For Figure 7 The schematic cross-sectional view of the structure in along the AA' and BB' directions;

[0062] Wherein, the reference numerals are:

[0063] 100 - Semiconductor substrate (wafer); 100a, 100b - Protective layer; 101 - Sacrificial layer; 102 - Passivation layer; 103 - Seed layer; 104 - First electrode layer; 105 - Piezoelectric layer; 106 - Second electrode layer; 107 - Second part of elastic film; 108a′ - Groove; 108a - First electrical contact hole; 108b - Second electrical contact hole; 109 - Conductive material; 110 - Excitation layer; 110a - Main body part; 110b - Rib; 120 - Opening; 130 - Cavity; 131 - Opening;

[0064] 200 - Semiconductor substrate; 200a - Protective layer; 201 - Sacrificial layer; 203 - Seed layer; 204 - First electrode layer; 205 - Piezoelectric layer; 206 - Second electrode layer; 207 - Second part of elastic film; 208a - First electrical contact hole; 208b - Second electrical contact hole; 209 - Conductive material; 210 - Excitation layer; 210a - Main body part; 210b - Rib; 220 - Opening; 230 - Cavity; 231 - Opening;

[0065] 300 - Semiconductor substrate; 300a - Protective layer; 301 - Sacrificial layer; 30 - Seed layer; 304 - First electrode layer; 305 - Piezoelectric layer; 306 - Second electrode layer; 307 - Second part of elastic film; 308a - First electrical contact hole; 308b - Second electrical contact hole; 309 - Conductive material; 310 - Excitation layer; 310a - Main body part; 310b - Rib; 320 - Opening; 330 - Cavity; 331 - Opening. Detailed implementation manners

[0066] The ultrasonic flight sensor of the present invention and its manufacturing method will be further described in detail below in conjunction with 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 conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention.

[0067] In the specification, terms such as "first" and "second" are used to distinguish between similar elements and are not necessarily used to describe a specific order or chronological order. It is to be understood that, where appropriate, these terms so used may be interchanged, for example, such 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 methods described herein include 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 may be omitted and / or some other steps not described herein may be added to the method. If a component in a drawing is the same as a component in other drawings, although these components can be easily recognized in all drawings, for the sake of clarity of the description of the drawings, the present specification will not label the reference numerals of all identical components in each drawing.

[0068] Embodiment 1

[0069] Figure 1 is a top view of a partial structure of the ultrasonic flight sensor provided in this embodiment, Figure 2a is Figure 1 a schematic cross-sectional view of the structure in Figure 2b is Figure 1 a schematic cross-sectional structure view along the CC' direction.

[0070] Referring to Figure 1 , Figure 2a and Figure 2b as shown, the ultrasonic flight sensor provided in this embodiment is fabricated using semiconductor processes. The ultrasonic flight sensor includes: a cavity 130, an excitation layer 110, and an elastic membrane. The cavity 130 is disposed in a semiconductor substrate 100. The excitation layer 110 is disposed above the cavity 130. The excitation layer 110 includes a first electrode layer 104, a second electrode layer 106, and a piezoelectric layer 105 disposed between the first electrode layer 104 and the second electrode layer 106. The excitation layer 110 is in a patterned design. The elastic membrane covers the cavity 130 and wraps the patterned excitation layer.

[0071] The elastic film includes a first part of the elastic film and a second part of the elastic film 107. The first part of the elastic film is disposed between the semiconductor substrate 100 and the excitation layer 110. The first part of the elastic film includes a protective layer 100a, a sacrificial layer 101, and a passivation layer 102 that are sequentially disposed on the semiconductor substrate 100. The main purpose of the protective layer 100a is to protect the semiconductor substrate 100 when the sacrificial layer is removed to form an opening. The material of the protective layer 100a can be selected according to the material of the sacrificial layer and the manufacturing process of the opening. The thickness of the protective layer 100a can also be selected according to the manufacturing process of the opening. The sacrificial layer 101 will be removed during the process of manufacturing the final ultrasonic flying sensor. The thickness of the sacrificial layer 101 is determined by the height of the opening in the cavity. The thickness of the passivation layer 102 in the first part of the elastic film mainly protects the first electrode layer 104 in the excitation layer 110, avoiding the direct exposure of the first electrode layer in the excitation layer 110 to the cavity. The thickness of the passivation layer 102 is generally set between 100 nm and 500 nm. The second part of the elastic film 107 covers the excitation layer 110. Since after the excitation layer 110 is patterned, the second part of the elastic film 107 will contact the first part of the elastic film at the position where the excitation layer is removed. The thickness of the second part of the elastic film 107 is greater than the thickness of the passivation layer 102 in the first part of the elastic film, which can make the neutral layer of the thickness of the entire vibration diaphragm deviate from the physical center of the vibration diaphragm. In this way, it is more convenient for the ultrasonic transducer to achieve the expected intensity and generate the desired higher sound pressure when vibrating at the preset frequency.

[0072] In this embodiment, the material of the protective layer 100a is, for example, silicon oxide, which can be used to protect the semiconductor substrate 100. The passivation layer 102 is disposed between the sacrificial layer 101 and the excitation layer 110. The material of the passivation layer 102 may be the same as that of the second part of the elastic film 107. The material of the sacrificial layer 101 is amorphous silicon (α-Si). Among them, the sacrificial layer 101 only exists during the fabrication process of the ultrasonic flight sensor, and in the structure of the finally formed ultrasonic flight sensor, only the cavity part where the sacrificial layer existed during the fabrication process can be shown. In the embodiment of the fabrication process, the sacrificial layer 101 is patterned and will cover the cavity positions formed subsequently in the semiconductor substrate 100. Therefore, the size of the sacrificial layer 101 is larger than the size of the cavity 130. The position where the sacrificial layer is located after patterning, that is, the position of the opening 131 formed subsequently. The opening 131 can be formed by releasing or removing the sacrificial material in the sacrificial layer 101. Since the sacrificial layer 101 is patterned, the opening 131 formed by the method exemplified above is located at the edge position of the cavity 130 formed in the semiconductor substrate 100 and has a relatively regular shape. By forming a regularly shaped opening 131 above the semiconductor substrate and communicating with the cavity in the semiconductor substrate, the shape of the edge position where the cavity of the finally formed ultrasonic flight sensor contacts the elastic film wrapping the excitation layer is regular. According to the test or simulation results of multiple ultrasonic flight sensors, the shape of the position where the cavity edge of the ultrasonic flight sensor contacts the elastic film will affect its sound generation or reception performance. In this way, it is beneficial to improve the consistency of the performance of ultrasonic flight sensors fabricated on the same wafer.

[0073] The excitation layer 110 is patterned. In the exemplified patterned excitation layer 110, it includes a main body part 110a and at least two ribs 110b. The patterned main body part 110a of the excitation layer 110 is disposed around the central region of the cavity 130. The patterned shapes of the patterned first electrode layer 104, the second electrode layer 106, and the piezoelectric layer 105 are the same or similar. For example, the first electrode layer 104, the second electrode layer 106, and the piezoelectric layer 105 are distributed in a ring shape around the central region of the cavity 130. When the excitation layer 110 and the elastic film receive an excitation signal, they generate vibrations at a preset frequency to generate ultrasonic waves. The relationship between the preset frequency and the cavity radius is generally characterized by the following formula (1):

[0074]

[0075] where f0 is the vibration frequency, a is the radius of the opening 131; D is the flexural rigidity of the vibration diaphragm formed by the excitation layer and the elastic film on the cavity, and ρ is the density of the vibration diaphragm.

[0076] As can be seen from the above formula (1), the operating frequency of the vibrating diaphragm is inversely related to the radius of the opening, that is, the lower the operating frequency of the vibrating diaphragm, the larger the required radius of the opening. The ultrasonic signals generated by the ultrasonic flight sensor need to propagate into the air. Since the attenuation of sound waves in the air increases with the increase of their frequency, in order to ensure that the ultrasonic waves generated by the ultrasonic flight sensor can be emitted within the expected range, its operating frequency is generally within 10 kHz - 300 kHz. Corresponding to this operating frequency range, the radius of the opening is approximately between 5 μm and 1 mm.

[0077] The thickness range of the first electrode layer 104 in the excitation layer 110 is 50 nm - 1 μm. Since after the production of the first electrode layer 104 is completed, a piezoelectric layer 105 needs to be formed on the surface of the first electrode layer, considering the comprehensive experimental and test results of the thickness of the first electrode layer, a more appropriate thickness is controlled within 100 nm - 300 nm. The thickness range of the second electrode layer 106 is 50 nm - 1 μm. Considering the resistance value of the second electrode layer 106 and the manufacturing process, the thickness of the second electrode layer 106 is more appropriately controlled within 100 nm - 300 nm. In the vibrating diaphragm, the second elastic membrane 107 covers the excitation layer 110, and the excitation layer 110 is covered by the second elastic membrane 107. In this embodiment, the thickness of the second elastic membrane 107 is greater than the thickness of the excitation layer 110. For example, the thickness range of the second elastic membrane 107 is 500 nm - 10 μm. Based on considerations of the operating frequency of the vibrating diaphragm, the size of the cavity, and the sensitivity of the ultrasonic flight sensor, a thickness of 3 μm - 5 μm for the second elastic membrane 107 is a more appropriate thickness.

[0078] The second elastic membrane 107 can act as a passivation layer for the excitation layer 110. The second elastic membrane 107 is disposed on the excitation layer 110 and can be configured with the first elastic membrane as a sealing layer of the resonant cavity. The material of the second elastic membrane can be the same as some of the materials in the first elastic membrane, or completely different from the materials used in the production of the first elastic membrane. The material of the second elastic membrane can be selected according to the manufacturing process of the ultrasonic flight sensor. By selecting the material properties, thickness, and internal stress of the second elastic membrane 107, the parameters of the ultrasonic flight sensor can be improved. For example, the resonant frequency, static and dynamic deflections, sound pressure output, and the generation of residual stress in the excitation layer 110 can be adjusted by appropriately configuring the second elastic membrane 107.

[0079] In this embodiment, the cross-section of the first electrode layer 104, the piezoelectric layer 105, and the second electrode layer 106 in the excitation layer 110 is in a trapezoidal shape, that is, the area of ​​the first electrode layer 104 is slightly larger than the area of ​​the piezoelectric layer 105, and the area of ​​the piezoelectric layer 105 is slightly larger than the area of ​​the second electrode layer 106. This is because when all the layer structures of the excitation layer are patterned using a semiconductor process, it is easy to make the actual cross-section of the patterned excitation layer present a trapezoidal shape.

[0080] In this embodiment, the cavity 130 is formed by etching the semiconductor substrate 100, and together with the opening 131 formed by etching the sacrificial layer 101, it constitutes the resonant cavity of the ultrasonic flight sensor. The cavity 130 and the opening 131 are formed after the excitation layer 110 is completed. The slightly thicker piezoelectric layer 105 in the excitation layer 110, when not patterned, will produce a large difference in stress in the same wafer for making the ultrasonic flight sensor, which can easily lead to the difference in performance between the ultrasonic flight sensors made from the same wafer, resulting in the deviation of their operating frequency exceeding the preset tolerance. Therefore, in order to reduce the drift of the ultrasonic flight sensor performance caused by the different stresses at different positions of the piezoelectric layer, the excitation layer 110 can be patterned. The main purpose of patterning the excitation layer is to reduce the area covered by the piezoelectric layer 105 in the excitation layer, and to reduce the influence of different stresses at different positions of the piezoelectric layer 105 on the performance of the ultrasonic flight sensor. In this embodiment, the excitation layer 110 is patterned and designed, and part of the piezoelectric layer is removed accordingly, or part of the electrode layer is removed at the same time, thereby reducing the influence of different stresses in different positions of the piezoelectric layer on the performance of the ultrasonic flight sensor.

[0081] In other embodiments, the excitation layer may be patterned, and only the electrode layer in the excitation layer may be patterned, without patterning the piezoelectric layer. Alternatively, the piezoelectric layer and the electrode layer in the excitation layer may be patterned with different patterns, respectively, and the piezoelectric layer and the electrode layer may be patterned with the same or similar patterns as in the above-described embodiments. The specific design patterns required for each layer of the final excitation layer may be determined by testing or simulating ultrasonic flight sensors with excitation layers of different patterns. The pattern of the excitation layer described herein is for description only and is not intended to be limiting.

[0082] In this embodiment, the ribs 110b are symmetrically arranged around the main body 110a of the excitation layer 110. The ribs 110b extend from the main body 110a to the peripheral portion of the cavity 130, and at least one of the ribs 110b is connected to the main body 110a and extends to the peripheral portion of the cavity 130 to lead out the first electrode layer 104 and the second electrode layer 106. In some embodiments, such as Figure 1As shown, the number of the support ribs 110b can be, for example, four. Two of the support ribs 110b extend to the peripheral part of the cavity 130 to lead out the first electrode layer 104 and the second electrode layer 106 respectively, and the remaining support ribs 110b can be electrically isolated from the main body part 110a of the excitation layer 110. Of course, in some other embodiments, only one support rib 110b is needed as the lead-out end of the excitation layer electrode layer. In other embodiments of the present invention, the specific number of support ribs 110b for leading out the electrodes can be determined according to the specific design, and the present invention does not make any limitation herein.

[0083] However, in the embodiments shown here or other embodiments, among the multiple support ribs 110b, some support ribs that are not used as the lead-out terminals of the excitation layer are not connected to the electrode layers in the excitation layer. For example, the excitation layer 110 further includes support ribs 110b symmetrically arranged with the main body part 110a of the excitation layer. The symmetrically arranged support ribs 110b are insulated from the first electrode layer 104 and the second electrode layer 106 of the main body part 110a of the excitation layer 110. The symmetric support rib structure is mainly to reduce the influence of the residual stress of the piezoelectric layer on the stiffness of the entire elastic diaphragm while maintaining the bending stiffness of the vibration diaphragm composed of the entire excitation layer and the elastic membrane.

[0084] The elastic membrane is provided with an opening 120. The size of the opening 120 is much smaller than that of the cavity 130. Of course, the position of the opening 120 can be selected at the position of the patterned opening of the elastic membrane located at the excitation layer 110, so as to avoid the need for this opening to penetrate the excitation layer 110. This opening 120 communicates with the cavity 130 through an opening 131. The purpose of this opening 120 is mainly to balance the pressures on both sides of the elastic diaphragm. In other embodiments, the opening 120 does not need to be located at the center of the cavity 130, and it can be opened at other positions where the stress of the elastic diaphragm is smaller.

[0085] Please refer to Figure 2a As shown, the ultrasonic flight sensor provided in this embodiment further includes a first electrical contact hole 108a and a second electrical contact hole 108b arranged outside the cavity 130. The first electrical contact hole 108a and the second electrical contact hole 108b are respectively electrically connected to the first electrode layer 104 and the second electrode layer 106 in the support rib 110b. For example, the first electrical contact hole 108a and the second electrical contact hole 108b are filled with a conductive material 109 to achieve electrical connection with the first electrode layer 104 and the second electrode layer 106 in the support rib 110b. In this way, an excitation signal is applied to the ultrasonic flight sensor through the first electrical contact hole 108a and the second electrical contact hole 108b, or the electrical signal converted after receiving the ultrasonic signal received by the ultrasonic flight sensor is received. As Figure 1As shown, the rib 110b extending to the peripheral portion of the cavity 130 leads out the first electrode layer 104 and the second electrode layer 106 in the excitation layer 110, and is electrically connected to the outside through the conductive material 109 filled in the first electrical contact hole 108a and the second electrical contact hole 108b.

[0086] The above briefly and clearly shows the main structure of the ultrasonic flying sensor, but does not clearly or specifically show the structures of other layers included in its actual structure. The ultrasonic flying sensor provided in this embodiment may actually further include: a seed layer 103 disposed between the passivation layer 102 and the excitation layer 110 to facilitate the growth of the excitation layer 110. The above are only examples of possible other layer structures and are not limited thereto.

[0087] It should be noted that for the convenience of describing the structure of the ultrasonic flying sensor in this embodiment, Figure 1 the corresponding top view is simplified accordingly. For example, the first electrode is represented by a dashed line, and the elastic membrane, sacrificial layer, passivation layer, etc. are not shown.

[0088] In the ultrasonic flying sensor provided in this embodiment, the elastic membrane wraps the excitation layer, protecting the excitation layer while being configured as the sealing layer of the resonant cavity. The ultrasonic flying sensor with such a structure can adapt to the manufacturing processes of most current semiconductor product manufacturers, can improve the parameters of the ultrasonic flying sensor, and enhance the performance of the ultrasonic flying sensor. In addition, manufacturing the ultrasonic flying sensor using semiconductor processes helps to miniaturize the ultrasonic flying sensor, reduces the volume of the ultrasonic flying sensor, and improves the compatibility of the ultrasonic flying sensor with other highly integrated electronic products.

[0089] Correspondingly, this embodiment provides a manufacturing method for an ultrasonic flying sensor. Figure 3 FIG. is a flowchart of the manufacturing method for the ultrasonic flying sensor provided in this embodiment. As Figure 3 shown, the manufacturing method for the ultrasonic flying sensor provided in this embodiment uses a wafer and semiconductor processes to manufacture the ultrasonic flying sensor. The manufacturing method includes:

[0090] S01: Form a first part of the elastic membrane on the wafer surface, and a patterned sacrificial layer is formed in the middle of the first part of the elastic membrane;

[0091] S02: Form an excitation layer on the surface of the first part of the elastic membrane and pattern the excitation layer;

[0092] S03: Form a second part of the elastic membrane on the surface of the excitation layer; and

[0093] S04: Form a cavity of the ultrasonic flight sensor by etching through the wafer from the back side of the wafer, a part of the first elastic film close to the wafer surface, and the sacrificial layer.

[0094] Figures 4a to 4k FIG. 4a to FIG. 4b are schematic structural diagrams of corresponding steps of a manufacturing method of an ultrasonic flight sensor provided by an embodiment of the present invention. Among them, FIG. 4a to FIG. 4b Figure 4k are the structural diagrams in the corresponding steps Figure 1 along the AA' and BB' directions; the following will further describe in detail the manufacturing method of the ultrasonic flight sensor provided by this embodiment with reference to Figure 3 and Figures 4a to 4k FIG. 4a to FIG. 4b.

[0095] Referring to Figure 4a FIG. 4a Figure 4b and FIG. 4b, perform step S01 to form a first elastic film on the surface of the wafer 100 (semiconductor substrate), and a patterned sacrificial layer 101 is formed in the middle of the first elastic film. Specifically, first, provide a wafer 100, and the wafer 100 may be at least one of the following materials: Si, Ge, SiGe, SiC, SiGeC, InAs, GAA's, InP, or other III / V compounds. The wafer 100 may also include a multi-layer structure composed of these materials, or be silicon-on-insulator (SOI), stacked silicon-on-insulator (SSOI), stacked silicon-germanium-on-insulator (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI), and germanium-on-insulator (GeO), etc.

[0096] Then, form a first elastic film on the surface of the wafer 100. Specifically, first, form a protective layer 100a and a sacrificial layer 101 on the surface of the wafer 100 in sequence. For the convenience of technical operation and protection of the wafer 100, a protective layer 100b is also formed on the back side of the wafer. Then, pattern the sacrificial layer 101, and the patterned sacrificial layer 101 corresponds to the position of the cavity to be fabricated later, as shown in Figure 4a FIG. 4a. Then, form the passivation layer 102 on the patterned sacrificial layer 101. Optionally, after forming the passivation layer 102, chemical mechanical polishing (CMP) can be performed, as shown in Figure 4bAs shown. The material of the sacrificial layer 101 is amorphous silicon (α-Si), and the thickness ranges from 0.1 - 2 μm, preferably 0.1 - 0.5 μm, such as 0.1 μm, 0.2 μm or 0.3 μm. The materials of the protective layer and the passivation layer 102 can both be, for example, silicon dioxide (SiO2), and the thickness ranges of both are 0.1 - 0.5 μm. In this embodiment, the first part of the elastic film includes a protective layer, a sacrificial layer, and a passivation layer; the sacrificial layer is disposed between the protective layer and the passivation layer. In the finally fabricated ultrasonic flight sensor, since the sacrificial layer will be removed, the sacrificial layer will be difficult to trace in the structure of the ultrasonic flight sensor. As described in the above content, the sacrificial layer will form an opening part in the corresponding cavity after being removed. To sum up, with different manufacturing processes, the material components included in the first part of the elastic film will be different in different embodiments. The general structure of the first part of the elastic film will include a protective layer on the wafer surface and a patterned sacrificial layer on the protective layer. The passivation layer may not be required in different embodiments. In the embodiment of this manufacturing method, the sacrificial layer is mainly fabricated to form the edge of the cavity of the ultrasonic flight sensor. The specific reasons have been described in the above embodiments of the structure and will not be elaborated here.

[0097] Reference Figures 4b to 4f As shown, perform step S02 to form an excitation layer 110 on the surface of the first part of the elastic film and pattern the excitation layer 110. The excitation layer 110 includes a first electrode layer 104, a piezoelectric layer 105, and a second electrode layer 106 formed in sequence on the surface of the first part of the elastic film.

[0098] The following is a specific manufacturing method as an example to further describe and explain this manufacturing method.

[0099] Specifically, please refer to Figures 4b to 4f A schematic diagram of the fabrication, which does not cover all the processes in the actual manufacturing process. First, as in Figure 4b and Figure 4c In the shown embodiment, a seed layer 103 is formed on the surface of the passivation layer 102. A first electrode layer 104 is formed on the surface of the seed layer 103. In an embodiment of the manufacturing method, after the first electrode layer is formed, the first electrode layer 104 can be patterned to etch the first electrode layer 104 into a preset shape. Then, a piezoelectric layer 105 and a second electrode layer 106 are sequentially deposited on the first electrode layer 104; then, the second electrode layer 106 and the piezoelectric layer 105 are etched in sequence to pattern the excitation layer 110.

[0100] After patterning the excitation layer 110, the shapes of the first electrode layer 104, the piezoelectric layer 105, and the second electrode layer 106 are the same or similar. In other embodiments of the present invention, the excitation layer 110 may also be formed by sequentially forming the first electrode layer 104, the piezoelectric layer 105, and the second electrode layer 106, and then patterning the second electrode layer 104, the piezoelectric layer 105, and the first electrode layer 106 in sequence. Compared with the embodiments exemplified by the above method of manufacturing the excitation layer, the use of one photomask can be saved, the manufacturing process can be simplified, and the manufacturing cost can be reduced. In the semiconductor manufacturing process exemplified herein, the patterning of the excitation layer 110 is mainly achieved by etching process.

[0101] In this embodiment, the material of the first electrode layer 104 may be molybdenum (Mo), platinum (Pt), aluminum (Al), gold (Au), etc. The second electrode layer 106 and the first electrode layer 104 may be prepared with the same material or different materials. The thickness of each layer has been described in the above content and will not be elaborated herein.

[0102] The material of the piezoelectric layer 105 may be aluminum nitride (AlN), aluminum nitride doped with scandium (Sc x Al 1-x Al), zinc oxide (ZnO), lead zirconate titanate piezoelectric ceramics (PZT), lead zirconate titanate piezoelectric ceramics doped with other elements (such as PLZT, PNZT), lead magnesium niobate-lead titanate (PMN-PT), KNN-based ceramics, or organic piezoelectric material polyvinylidene fluoride (PVDF), etc. In this embodiment, the first electrode layer 104 and the second electrode layer 106 are molybdenum (Mo), and the material of the piezoelectric layer 105 is aluminum nitride (AlN).

[0103] As described in the embodiments with the above structure, for the patterning of the excitation layer, it is not necessary to pattern all the material layers of the excitation layer, or the patterns of the materials of each layer of the excitation layer after patterning do not have to be exactly the same. As described above, the specific pattern of the excitation layer after patterning can be adjusted according to the test results obtained from the actual manufacturing of the ultrasonic sensor. Therefore, when the preset pattern of the excitation layer is different, the actual manufacturing process of the excitation layer will also be adjusted. Therefore, the embodiments of manufacturing the excitation layer described above are only described corresponding to the embodiments with the above-exemplified structure and are not limited thereto.

[0104] Reference Figure 4gAs shown, step S03 is performed to fabricate a second partial elastic film 107 on the surface of the excitation layer 110. The thickness of the second partial elastic film 107 is greater than that of the excitation layer 110, and a part of the second partial elastic film 107 penetrates through the excitation layer and is located on the sacrificial layer 101. The material of the second partial elastic film 107 can be silicon (Si), silicon dioxide (SiO2), or silicon nitride (Si3N4), and the thickness range of the second partial elastic film 107 is 500 nm - 10 μm. Preferably, the thickness is 3 μm - 5 μm.

[0105] Next, referring to Figures 4h to 4k As shown, step S04 is performed to form a cavity 130 of the ultrasonic flight sensor by etching through the wafer, a part of the first partial elastic film adjacent to the wafer surface, and the sacrificial layer from the back side of the wafer.

[0106] Specifically, first, the protective layer 100b on the side of the wafer different from the sacrificial layer 101 is removed, and the back side of the wafer 100 is thinned. Then, the wafer 100 can be etched using deep reactive ion etching (DRIE) to form the cavity 130.

[0107] Next, a part of the first partial elastic film adjacent to the wafer surface is etched away, that is, a part of the protective layer 100a is etched away, so that the cavity 130 in the wafer 100 extends to the sacrificial layer 101.

[0108] Then, in this embodiment, the sacrificial layer 101 is etched wet. For example, xenon difluoride (XeF2) gas-phase etching can be used to remove the sacrificial layer 101. The etching rate of XeF2 for the sacrificial layer (amorphous silicon) 101 is greater than that for the semiconductor substrate (silicon substrate) 100. Therefore, the influence on the wafer 200 during the process of etching the sacrificial layer 101 to form the opening 131 is small. In other embodiments of the manufacturing method, other materials can also be selected for the sacrificial layer 101, and corresponding release agents can be used for removal. Since the sacrificial layer 101 is patterned in step S02, in this step, only wet etching is required to release the sacrificial layer 101 corresponding to the cavity 130, so that the formed opening 131 has a regular edge structure, and then is connected to the cavity 130 formed in the semiconductor substrate 100, ensuring that the edges of the cavities of the ultrasonic flight sensors formed in the entire semiconductor substrate are all regular and highly consistent in shape. This enables the performance parameter differences between the ultrasonic flight sensors in the same semiconductor substrate to be within a preset tolerance range.

[0109] From the embodiments of the manufacturing method of the cavity of the above ultrasonic flight sensor, it can be seen that after the cavity 130 communicates with the opening 131, there are still a passivation layer 102 and a seed layer 103 between the first electrode layer 104 in the excitation layer and the opening 131. Since the cavity 130 communicates with the outside air during the use of the ultrasonic flight sensor. To avoid the influence of the environment in the air on the first electrode layer, such as oxidation, the passivation layer 102 and the seed layer 103 play a certain protective role for the first electrode layer 104. Of course, when the seed layer 103 can also play the expected protective role for the first electrode layer 104, the production of the passivation layer 102 can be omitted for the first part of the elastic film.

[0110] Continuing to refer to Figures 4h to 4k As shown, the manufacturing method of the ultrasonic flight sensor provided in this embodiment further includes the following steps: making a first electrical contact hole 108a and a second electrical contact hole 108b on the second part of the elastic film 107 and the excitation layer 110 in the peripheral part of the cavity 130 and filling the first electrical contact hole 108a and the second electrical contact hole 108b with a conductive material 109.

[0111] Continuing to refer to Figures 4h to 4k As shown, the manufacturing method of the ultrasonic flight sensor provided in this embodiment further includes making an opening 120 in the part of the second part of the elastic film 107 covering the cavity 130. The opening 120 penetrates through the second part of the elastic film 107 and the first part of the elastic film and communicates with the cavity 130 through the opening 131, so that the air pressures in the cavity 130 and the outside air are the same. The opening 120 can be made after the first electrical contact hole 108a and the second electrical contact hole 108b are made. In this way, it is avoided that impurities or contaminants enter the cavity 130 through this opening 120. Of course, in other manufacturing methods, when the above-described problems do not occur, it can also be completed in the same step as the first electrical contact hole 108a and the second electrical contact hole 108b, and the present invention does not limit this.

[0112] It should be noted that, for the sake of more concise and clear illustration of the structure and manufacturing method of this case, some other structural layers are omitted in the manufacturing method or structure of the ultrasonic flight sensor provided by the present invention to simplify the description of the structure and manufacturing method.

[0113] Embodiment 2

[0114] This embodiment provides an ultrasonic flight sensor. Figure 5 It is a top view of a partial structure of the ultrasonic flight sensor provided in this embodiment, Figure 6 is Figure 5 a schematic cross-sectional view of the structure in

[0115] Refer to Figure 5and Figure 6 As shown in Figure 6 , the ultrasonic flight sensor provided in this embodiment is fabricated using semiconductor processes. The ultrasonic flight sensor includes: a cavity 230, an excitation layer 210, and an elastic film. The cavity 230 is disposed in a semiconductor substrate 200. The excitation layer 210 is disposed above the cavity 230. The excitation layer 210 is patterned and includes a first electrode layer 204, a second electrode layer 206, and a piezoelectric layer 205 disposed between the first electrode layer 204 and the second electrode layer 206. The elastic film covers the cavity 230 and wraps the patterned excitation layer 210.

[0116] The elastic film includes a first partial elastic film and a second partial elastic film 207. The first partial elastic film is disposed between the semiconductor substrate 200 and the excitation layer 210. The first partial elastic film includes a protective layer 200a, a sacrificial layer 201, and a passivation layer 202 sequentially disposed on the semiconductor substrate 200. The second partial elastic film 207 covers the excitation layer 200. Since the excitation layer 210 is patterned, the second partial elastic film 207 will contact the first partial elastic film at the positions where the excitation layer is removed. Among them, the sacrificial layer only exists during the fabrication process of the ultrasonic flight sensor, and only the cavity part where the sacrificial layer existed during the fabrication process can be shown in the structure of the finally formed ultrasonic flight sensor. In an embodiment of the fabrication process, the sacrificial layer 201 is patterned and will cover the position of the cavity to be formed in the semiconductor substrate 200 subsequently. Therefore, the size of the sacrificial layer is larger than the size of the cavity 230. The position where the sacrificial layer is located after patterning, that is, the position of the subsequent formed opening 231. The opening 231 can be formed by releasing or removing the sacrificial material in the sacrificial layer 201. Since the sacrificial layer 201 is patterned, the opening 231 formed by the method exemplified above is located at the edge position of the cavity 230 formed in the semiconductor substrate 200 and has a relatively regular shape.

[0117] The excitation layer 210 is patterned. The patterned excitation layer 210 exemplified herein includes a main body part 210a and at least two ribs 210b. The main body part 210a of the patterned excitation layer 210 is disposed around the central region of the cavity 230. The patterned shapes of the first electrode layer 204, the second electrode layer 206, and the piezoelectric layer 205 are the same or similar. For example, the first electrode layer 204, the second electrode layer 206, and the piezoelectric layer 205 are distributed in a ring shape around the central region of the cavity 130. Compared with the first embodiment, the main body part 210a of the excitation layer 210 in this embodiment is in a ring shape and is located at some relatively edge positions above the cavity 230.

[0118] The vertical cross-sectional shape of the cavity 230 can be, for example, square or trapezoidal. As described in Embodiment 1, the size of the cavity 230 is determined according to the operating frequency of the ultrasonic flight sensor, and its cross-section is circular. The second part of the elastic film 207 is provided with an opening 220 that penetrates the elastic film 207 and communicates with the cavity 230 through an opening 231. The structure of the ultrasonic flight sensor exemplified in Embodiment 2 introduced herein is generally the same as the content introduced in Embodiment 1. The main difference is that in Embodiment 2, a plurality of the openings 220 are provided, and the openings 220 are symmetrically arranged in the area of the elastic film (the passivation layer 202 and the second part of the elastic film 207) corresponding to the edge of the cavity 230. As Figure 5 and Figure 6 shown, an opening 220 is formed in the elastic film wrapping the main body portion 210a of the excitation layer 210, and the opening 220 communicates with the opening 231. In this embodiment, forming the opening 220 in the area of the elastic film corresponding to the edge of the cavity 230 is beneficial to reducing the influence of the elastic film stress on the device frequency. The patterned excitation layer is annular, and compared with Embodiment 1, the shape of the patterned excitation layer will be different. In Embodiment 1, the excitation layer is relatively distributed in the middle area of the elastic film corresponding to the cavity, while in this embodiment, the patterned excitation layer is distributed at a position relatively close to the edge of the elastic film corresponding to the cavity.

[0119] In this embodiment, the number of the openings 220 is 4 and they are symmetrically arranged with respect to the cavity 230. In other embodiments of the present invention, the number of the openings 220 can be one, two, three, or more than four, and openings 220 can also be formed simultaneously in the central area and the edge area of the elastic film corresponding to the cavity. The specific number and position of the formed openings 220 can be determined according to specific designs, and the present invention does not make any limitation herein.

[0120] As Figure 5 and Figure 6 shown, the ultrasonic flight sensor provided in this embodiment further includes a first electrical contact hole 208a and a second electrical contact hole 208b disposed outside the cavity 230, and the first electrical contact hole 208a and the second electrical contact hole 208b are respectively electrically connected to the first electrode layer 204 and the second electrode layer 206 in the rib 210b. For example, the first electrical contact hole 208a and the second electrical contact hole 208b are filled with a conductive material 209 to achieve electrical connection with the first electrode layer 204 and the second electrode layer 206 in the rib 210b.

[0121] Embodiment 3

[0122] This embodiment provides an ultrasonic flight sensor. Figure 7 is a top view of a partial structure of the ultrasonic flight sensor provided in this embodiment,Figure 8 is Figure 7 A schematic cross-sectional view of the structure in

[0123] Referring to Figure 7 and Figure 8 As shown, the ultrasonic flight sensor provided in this embodiment is fabricated using semiconductor processes. The ultrasonic flight sensor includes: a cavity 330, an excitation layer 310, and an elastic membrane. The cavity 330 is disposed in a semiconductor substrate 300. The excitation layer 310 is disposed above the cavity 330. The elastic membrane covers the cavity 330 and encapsulates the patterned excitation layer 310. Among them, the excitation layer 310 is in a patterned design and includes a first electrode layer 304, a second electrode layer 306, and a piezoelectric layer 305 disposed between the first electrode layer 304 and the second electrode layer 306.

[0124] The elastic membrane is provided with an opening 320 that penetrates the elastic membrane (the passivation layer 302 in the first part of the elastic membrane and the second part of the elastic membrane 307) and communicates with the cavity 330 through an opening 331. The structure of the ultrasonic flight sensor exemplified in the third embodiment of the opening 320 is generally the same as the content introduced in the second embodiment. The main difference is that in the third embodiment, the main part 310a of the patterned excitation layer 310 is distributed in the middle region of the elastic membrane corresponding to the cavity, and several openings 320 are similar to the openings in the second embodiment, and the openings 320 are provided at the edge position of the elastic membrane covering the cavity. In this way, the patterning process of the excitation layer 310 is correspondingly simplified, and the generation time is saved.

[0125] In summary, the above examples illustrate the patterned excitation layers with different patterns and the positions of the openings in the cavity, but are not limited thereto.

[0126] The present invention provides an ultrasonic flight sensor and a manufacturing method thereof, including a cavity disposed in a semiconductor substrate, an excitation layer disposed above the cavity and in a patterned design, and an elastic membrane covering the cavity and encapsulating the patterned excitation layer, wherein the excitation layer includes a first electrode layer, a second electrode layer, and a piezoelectric layer disposed between the first electrode layer and the second electrode layer. On the premise of miniaturizing the ultrasonic flight sensor, the present invention utilizes existing semiconductor product manufacturing processes so that the produced ultrasonic flight sensor can achieve the expected performance.

[0127] Furthermore, the present invention opens an opening in the edge region of the elastic membrane corresponding to the cavity, which is beneficial to reducing the influence of the elastic membrane stress on the frequency of the ultrasonic flight sensor.

[0128] 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, and 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 for the relevant parts, reference can be made to the partial description of the method embodiments.

[0129] 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. An ultrasonic flight sensor, characterized in that, Fabricated using semiconductor processes, and the ultrasonic flying sensor includes: A cavity disposed in a semiconductor substrate; An excitation layer disposed above the cavity, the excitation layer including a first electrode layer, a second electrode layer, and a piezoelectric layer disposed between the first electrode layer and the second electrode layer, the excitation layer being patterned; An elastic membrane covering the cavity and wrapping the patterned excitation layer, the elastic membrane having an opening that penetrates the elastic membrane and communicates with the cavity.

2. The ultrasonic flight sensor according to claim 1, characterized in that The opening is disposed in a central region of the elastic membrane corresponding to the cavity.

3. The ultrasonic flight sensor according to claim 1, wherein The opening is symmetrically disposed in an edge region of the elastic membrane corresponding to the cavity.

4. The ultrasonic flight sensor according to claim 2 or 3, characterized in that, The first electrode layer, the second electrode layer, and the piezoelectric layer are patterned to have the same or similar shapes.

5. The ultrasonic flight sensor according to claim 4, characterized in that, The main body portion of the patterned excitation layer is disposed around the central region of the cavity.

6. The ultrasonic flight sensor according to claim 5, wherein, The excitation layer further includes at least two ribs symmetrically disposed around the main body portion of the excitation layer, the ribs extending from the main body portion towards the peripheral portion of the cavity.

7. The ultrasonic flight sensor according to claim 6, characterized in that, At least one of the ribs is connected to the main body portion of the excitation layer and extends to the peripheral portion of the cavity to lead out the first electrode layer and the second electrode layer.

8. The ultrasonic flight sensor according to claim 7, characterized in that, Further includes a first electrical contact hole and a second electrical contact hole disposed outside the cavity; the first electrical contact hole and the second electrical contact hole are electrically connected to the first electrode layer and the second electrode layer in the ribs respectively.

9. The ultrasonic flight sensor according to claim 8, wherein, The first electrical contact hole and the second electrical contact hole are filled with a conductive material and are electrically connected to the first electrode layer and the second electrode layer in the nearby excitation layer respectively.

10. The ultrasonic flight sensor according to claim 6, characterized in that, The excitation layer further includes ribs symmetrically disposed with respect to the main body portion of the excitation layer, and the symmetrically disposed ribs are insulated from the first electrode layer and the second electrode layer of the main body portion of the excitation layer.

11. A manufacturing method of an ultrasonic flight sensor, which uses a wafer and semiconductor processes to manufacture the ultrasonic flight sensor, characterized in that, The manufacturing method includes: Forming a first partial elastic membrane on the surface of a wafer, and a patterned sacrificial layer is formed in the middle of the first partial elastic membrane; Forming an excitation layer on the surface of the first partial elastic membrane and patterning the excitation layer; Forming a second partial elastic membrane on the surface of the excitation layer; and Etching through the wafer, a portion of the first partial elastic membrane adjacent to the wafer surface, and the sacrificial layer from the back surface of the wafer to form the cavity of the ultrasonic flying sensor; Wherein, an opening is made in the portion of the second partial elastic membrane covering the cavity, and the opening penetrates the second partial elastic membrane and the first partial elastic membrane and communicates with the cavity.

12. The manufacturing method of the ultrasonic flight sensor according to claim 11, characterized in that, The manufacturing of the excitation layer includes: Manufacturing the first electrode layer; Manufacturing the piezoelectric layer on the manufactured first electrode layer; Manufacturing the second electrode layer on the manufactured piezoelectric layer.

13. The manufacturing method of the ultrasonic flight sensor according to claim 12, characterized in that, Patterning the excitation layer includes: The first electrode layer, the piezoelectric layer, and the second electrode layer after patterning have the same or similar shapes.

14. The manufacturing method of the ultrasonic flight sensor according to claim 11, characterized in that, Forming the first partial elastic membrane includes: Forming a protective layer adjacent to the surface of the wafer; Forming the sacrificial layer on the surface of the protective layer; Patterning the sacrificial layer; Forming a passivation layer on the surface of the patterned sacrificial layer.

15. The manufacturing method of the ultrasonic flight sensor according to claim 14, characterized in that, The partial first partial elastic membrane is the protective layer adjacent to the wafer surface, and the passivation layer is adjacent to the excitation layer.

16. The manufacturing method of the ultrasonic flight sensor according to claim 11, characterized in that, The size of the patterned sacrificial layer is larger than the size of the subsequently formed cavity in the wafer.

17. The manufacturing method of the ultrasonic flight sensor according to claim 11, characterized in that, It further includes fabricating a first electrical contact hole and a second electrical contact hole in the peripheral portion of the cavity.

18. The manufacturing method of the ultrasonic flight sensor according to claim 17, characterized in that, It further includes filling the first electrical contact hole and the second electrical contact hole with a conductive material, such that the first electrical contact hole is electrically connected to a first electrode layer of the driving layer, and the second electrical contact hole is electrically connected to a second electrode layer of the driving layer.

Images