Piezoelectric tuning microphone sensor and manufacturing method

Abstract

According to the piezoelectric tuning microphone sensor and the manufacturing method provided by the invention, optimal sensitivity regulation and control are realized by adopting piezoelectric driving, the piezoelectric tuning microphone sensor has the advantages of low noise, high sensitivity, high integration level, large working bandwidth and the like, and failure caused by an attraction effect caused by electrostatic regulation and control can be avoided; the signal-to-noise ratio and the working bandwidth are further improved; besides, integrated preparation of the grating structure and the vibrating diaphragm structure is completed by adopting a surface process, bonding is not needed, the precision alignment problem and the thermal stress problem caused by the bonding process are avoided, the process complexity is reduced, later assembly is not needed, and the advantage of batch consistency production is achieved.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology and relates to a piezoelectrically tuned microphone sensor and its manufacturing method. Background Technology

[0002] MEMS microphones are classified into condenser microphones and optical microphones based on their sensing methods. Condenser microphones introduce more electronic noise due to electrical measurements, and their size and sensitivity are limited by the pull-in voltage. MEMS optical microphones, on the other hand, have the advantages of low noise, high sensitivity, and high integration, and have the potential for wide application in fields such as smart electronic devices, medical and health care, and urban building noise monitoring.

[0003] In electrostatically driven MEMS optical microphones, the electrostatic softening effect during the electrostatic driving process can cause grating bending and deformation, affecting the test accuracy. Electrostatic driving also has a pull-in effect, and continuously increasing the adjustment voltage may cause the device to fail to pull in momentarily, resulting in limited signal-to-noise ratio and bandwidth testing. In addition, the manufacturing process of electrostatically driven MEMS optical microphones is complex, and the consistency of mass production is poor.

[0004] Therefore, how to provide a piezoelectrically tuned microphone sensor and its manufacturing method to improve sensitivity and signal-to-noise ratio while reducing process complexity has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a piezoelectrically tuned microphone sensor and its manufacturing method, which solves the problems of low testing accuracy and complex manufacturing process of electrostatically driven MEMS optical microphones in the prior art.

[0006] To achieve the above and other related objectives, the present invention provides a method for manufacturing a piezoelectrically tuned microphone sensor, comprising the following steps:

[0007] A substrate is provided, on which an etching barrier layer, a diaphragm material layer, a sacrificial layer, a grating material layer, a first electrode material layer, a piezoelectric material layer, and a second electrode material layer are formed from bottom to top.

[0008] The first electrode material layer, the piezoelectric material layer and the second electrode material layer are etched to form a piezoelectric driving structure, wherein the piezoelectric driving structure includes a first electrode layer, a piezoelectric layer and a second electrode layer stacked from bottom to top;

[0009] The grating material layer is etched to form a grating structure and a cantilever beam structure, wherein, in a planar layout, the grating structure is connected to the cantilever beam structure and the piezoelectric drive structure;

[0010] The substrate is etched to form a cavity in the substrate, and the cavity exposes the etching barrier layer at a predetermined location;

[0011] The sacrificial layer beneath the grating structure and the cantilever beam structure is removed to create gaps between the grating structure and the diaphragm material layer, and between the cantilever beam structure and the diaphragm material layer. The exposed etching barrier layer is then removed to expose the diaphragm material layer, which constitutes the diaphragm structure.

[0012] The piezoelectric drive structure can drive the position of the cantilever beam structure to change, thereby controlling the distance between the grating structure and the diaphragm structure.

[0013] Optionally, before etching the grating material layer, the following step is further included:

[0014] An insulating layer covering the piezoelectric drive structure is formed on the grating material layer;

[0015] A first electrode lead-out layer and a second electrode lead-out layer are formed. The first electrode lead-out layer penetrates the insulating layer and is electrically connected to the first electrode layer. The second electrode lead-out layer penetrates the insulating layer and is electrically connected to the second electrode layer.

[0016] Optionally, in a planar layout, the body of the piezoelectric drive structure is arranged around the periphery of the grating structure.

[0017] Optionally, after forming the gap and the diaphragm structure, the method further includes forming a reflective layer on the side of the grating structure away from the diaphragm structure.

[0018] Optionally, after forming the gap and the diaphragm structure, the following steps are further included:

[0019] A cover plate is provided and fixed above the grating material layer. The side portion of the cover plate is located around the piezoelectric drive structure. A laser and a photodetector are provided on the top surface of the cover plate facing the grating structure. A plurality of cover plate pads are provided on the top surface of the cover plate away from the grating structure. Some of the cover plate pads are electrically connected to the laser through through-silicon vias, and some of the cover plate pads are electrically connected to the photodetector through through-silicon vias.

[0020] Optionally, after fixing the cover plate above the grating material layer, the method further includes the following steps:

[0021] A package housing and a package substrate are provided, and the substrate is fixed to the package housing or the package substrate. The piezoelectric drive structure is electrically connected to the package housing or the package substrate via bonding wires, and the cover plate pad is electrically connected to the package housing or the package substrate via bonding wires.

[0022] The present invention also provides a piezoelectrically tuned microphone sensor, comprising:

[0023] A substrate, wherein an etching barrier layer is disposed on the substrate, and a diaphragm material layer is disposed on the etching barrier layer;

[0024] A cavity, penetrating the substrate and the etch barrier layer to expose the diaphragm material layer at a predetermined position, wherein the exposed diaphragm material layer constitutes a diaphragm structure;

[0025] The sacrificial layer is located above the diaphragm material layer;

[0026] A grating material layer, a cantilever beam structure, and a grating structure are arranged on the same layer and located above the sacrificial layer. One end of the cantilever beam structure is connected to the grating material layer, and the other end of the cantilever beam structure is connected to the grating structure. There are gaps between the grating structure and the diaphragm material layer, as well as between the cantilever beam structure and the diaphragm material layer.

[0027] A piezoelectric driving structure is located above the grating material layer and extends above the cantilever beam structure. The piezoelectric driving structure includes a first electrode layer, a piezoelectric layer, and a second electrode layer stacked from bottom to top.

[0028] The piezoelectric drive structure can drive the position of the cantilever beam structure to change, thereby controlling the distance between the grating structure and the diaphragm structure.

[0029] Optionally, it also includes:

[0030] An insulating layer is located above the grating material layer, covering the piezoelectric drive structure;

[0031] The first electrode lead-out layer penetrates the insulating layer and is electrically connected to the first electrode layer;

[0032] The second electrode lead-out layer penetrates the insulating layer and is electrically connected to the second electrode layer.

[0033] Optionally, in a planar layout, the body of the piezoelectric drive structure is arranged around the periphery of the grating structure.

[0034] Optionally, the grating structure has a reflective layer on the side away from the diaphragm structure.

[0035] Optionally, the system further includes a cover plate fixed above the grating material layer. The side portion of the cover plate is located around the piezoelectric drive structure. A laser and a photodetector are provided on the top surface of the cover plate facing the grating structure. A plurality of cover plate pads are provided on the top surface of the cover plate away from the grating structure. Some of the cover plate pads are electrically connected to the laser through through-silicon vias, and some of the cover plate pads are electrically connected to the photodetector through through-silicon vias.

[0036] Optionally, it further includes a package housing and a package substrate, the package housing and the package substrate forming a package space, the substrate being fixed to the package housing or the package substrate, wherein the piezoelectric drive structure is electrically connected to the package housing or the package substrate via bonding leads, and the cover plate pad is electrically connected to the package housing or the package substrate via bonding leads.

[0037] As described above, in the piezoelectrically tuned microphone sensor and manufacturing method of the present invention, piezoelectric driving is used to achieve optimal sensitivity control, which not only has the advantages of low noise, high sensitivity, high integration and large operating bandwidth, but also avoids the failure caused by the attraction effect due to electrostatic control, and has the advantage of further improving the signal-to-noise ratio and operating bandwidth. In addition, the grating structure and diaphragm structure are integrated by surface processing, which eliminates the need for bonding, avoids the accuracy alignment problem and thermal stress problem caused by bonding process, reduces process complexity, eliminates the need for post-assembly, and has the advantage of mass production consistency. Attached Figure Description

[0038] Figure 1 The diagram shown is a flowchart of the fabrication method of the piezoelectrically tuned microphone sensor in an embodiment of the present invention.

[0039] Figure 2 The diagram shown is a schematic diagram of a substrate provided in an embodiment of the present invention, on which an etching barrier layer, a diaphragm material layer, a sacrificial layer, a grating material layer, a first electrode material layer, a piezoelectric material layer, and a second electrode material layer are formed.

[0040] Figure 3 The diagram shown is a schematic diagram of the piezoelectric drive structure formed in an embodiment of the present invention.

[0041] Figure 4 The diagram shown is a schematic diagram of the formation of an insulating layer, a first electrode lead-out layer, and a second electrode lead-out layer in an embodiment of the present invention.

[0042] Figure 5 The diagram shown illustrates the formation of the grating structure and the cantilever beam structure in an embodiment of the present invention.

[0043] Figure 6 The diagram shown illustrates the formation of a cavity in an embodiment of the present invention.

[0044] Figure 7 The diagram shown is a schematic representation of the gap and diaphragm structure formed in an embodiment of the present invention.

[0045] Figure 8 The image shown is a top view of the diaphragm structure formed in an embodiment of the present invention.

[0046] Figure 9 The image shown is a bottom view of the diaphragm structure formed in an embodiment of the present invention.

[0047] Figure 10 The diagram shown is a schematic diagram of the formation of the reflective layer in an embodiment of the present invention.

[0048] Figure 11 The diagram shows a cover plate provided in an embodiment of the present invention, which is fixed to the grating material layer.

[0049] Figure 12 The diagram shows a packaged casing and a packaged substrate for packaging in an embodiment of the present invention.

[0050] Figure 13 The graph shown is a time-domain response curve in an embodiment of the present invention.

[0051] Figure 14 The graph shown is a response curve of sensitivity as a function of frequency in an embodiment of the present invention.

[0052] Figure 15 The graph shown is a logarithmic spectrum curve measured at 1 kHz in an embodiment of the present invention.

[0053] Component designation explanation

[0054] 1. Base

[0055] 100 cavity

[0056] 2. Etching barrier layer

[0057] 3. Diaphragm material layer

[0058] 300 diaphragm structure

[0059] 4. Sacrificial Layer

[0060] 400 gap

[0061] 5. Grating material layer

[0062] 500 grating structure

[0063] 501 Cantilever Beam Structure

[0064] 6 First electrode material layer

[0065] 600 First electrode layer

[0066] 7. Piezoelectric material layer

[0067] 700 piezoelectric layer

[0068] 8 Second electrode material layer

[0069] 800 Second electrode layer

[0070] 9. Piezoelectric drive structure

[0071] 10 Insulation layer

[0072] 11. Reflective layer

[0073] 12 Cover plates

[0074] 1200 laser

[0075] 1201 photodetector

[0076] 1202 Cover plate pad

[0077] 13. Packaged casing

[0078] 14 Packaging substrate

[0079] 15 bonded leads

[0080] Steps S1 to S5 Detailed Implementation

[0081] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0082] Please see Figures 1 to 15 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0083] This embodiment provides a method for fabricating a piezoelectrically tuned microphone sensor. Please refer to [link / reference]. Figure 1 The method for manufacturing the piezoelectrically tuned microphone sensor includes the following steps:

[0084] S1: Provide a substrate, and form an etch barrier layer, a diaphragm material layer, a sacrificial layer, a grating material layer, a first electrode material layer, a piezoelectric material layer and a second electrode material layer disposed from bottom to top on the substrate;

[0085] S2: Etch the first electrode material layer, the piezoelectric material layer and the second electrode material layer to form a piezoelectric driving structure, wherein the piezoelectric driving structure includes a first electrode layer, a piezoelectric layer and a second electrode layer stacked from bottom to top;

[0086] S3: Etch the grating material layer to form a grating structure and a cantilever beam structure, wherein, in a planar layout, the grating structure is connected to the cantilever beam structure and the piezoelectric drive structure;

[0087] S4: Etch the substrate to form a cavity in the substrate, the cavity exposing the etching barrier layer at a predetermined position;

[0088] S5: Remove the sacrificial layer below the grating structure and the cantilever beam structure to form gaps between the grating structure and the diaphragm material layer and between the cantilever beam structure and the diaphragm material layer, and remove the exposed etching barrier layer to expose the diaphragm material layer, which constitutes the diaphragm structure.

[0089] The fabrication method of the piezoelectrically tuned microphone sensor in this embodiment will be described in detail below with reference to the specific accompanying drawings.

[0090] First, please refer to Figure 2 Step S1: Provide a substrate 1, and form an etching barrier layer 2, a diaphragm material layer 3, a sacrificial layer 4, a grating material layer 5, a first electrode material layer 6, a piezoelectric material layer 7, and a second electrode material layer 8 on the substrate 1 from bottom to top.

[0091] As an example, in this embodiment, the substrate 1 is made of silicon, the etch barrier layer 2 is made of silicon oxide, the diaphragm material layer 3 is made of polycrystalline silicon, the sacrificial layer 4 is made of silicon oxide, the grating material layer 5 is made of polycrystalline silicon, the first electrode material layer 6 is made of molybdenum, the piezoelectric material layer 7 is made of aluminum scandium nitride (AlScN), and the second electrode material layer 8 is made of molybdenum. In other examples, the substrate 1, the etch barrier layer 2, the diaphragm material layer 3, the sacrificial layer 4, the grating material layer 5, the first electrode material layer 6, the piezoelectric material layer 7, and the second electrode material layer 8 may also be made of other suitable materials, and are not limited to this embodiment.

[0092] As an example, the etching barrier layer 2, the diaphragm material layer 3, the sacrificial layer 4, the grating material layer 5, the first electrode material layer 6, the piezoelectric material layer 7, and the second electrode material layer 8 are formed on the substrate 1 using physical vapor deposition, chemical vapor deposition, magnetron sputtering, electroplating, or any other suitable method.

[0093] Next, please refer to Figure 3 Step S2: Etch the first electrode material layer 6, the piezoelectric material layer 7 and the second electrode material layer 8 to form a piezoelectric driving structure 9, wherein the piezoelectric driving structure 9 includes a first electrode layer 600, a piezoelectric layer 700 and a second electrode layer 800 stacked from bottom to top.

[0094] As an example, the first electrode material layer 6, the piezoelectric material layer 7, and the second electrode material layer 8 are patterned by dry etching to form the piezoelectric driving structure 9, wherein the first electrode layer 600 is formed based on the first electrode material layer 6, the piezoelectric layer 700 is formed based on the piezoelectric material layer 7, and the second electrode layer 800 is formed based on the second electrode material layer 8.

[0095] For example, please refer to Figure 4 After forming the piezoelectric drive structure 9, the following steps are also included:

[0096] (i) An insulating layer 10 is formed on the grating material layer 5. The insulating layer 10 covers the piezoelectric drive structure 9 to provide insulation protection for the piezoelectric drive structure 9. The insulating layer 10 should be appropriately thick to prevent the piezoelectric drive structure 9 from short-circuiting. In this embodiment, the insulating layer 10 is made of silicon oxide.

[0097] (ii) A first contact hole and a second contact hole are formed in the insulating layer 10 using a dry etching method. The first contact hole penetrates the insulating layer 10 to expose the first electrode layer 600, and the second contact hole penetrates the insulating layer 10 to expose the second electrode layer 800. Then, a metal layer is deposited on the insulating layer 10 and the metal layer is filled into the first contact hole and the second contact hole. The metal layer is then etched using a plasma etching method to form a first electrode lead-out layer 900 and a second electrode lead-out layer 901. The first electrode lead-out layer 900 penetrates the insulating layer 10 and is electrically connected to the first electrode layer 600, and the second electrode lead-out layer 901 penetrates the insulating layer 10 and is electrically connected to the second electrode layer 800.

[0098] Next, please refer to Figure 5Step S3 is executed: the grating material layer 5 is etched to form a grating structure 500 and a cantilever beam structure 501, wherein, in a planar layout, the grating structure 500 is connected to the piezoelectric drive structure 9 through the cantilever beam structure 501.

[0099] As an example, the preset position of the grating material layer 5 is patterned to form the grating structure 500 and the cantilever beam structure 501. The piezoelectric driving structure 9 extends above the cantilever beam structure 501. When a voltage is applied to the piezoelectric driving structure 9 through the first electrode lead-out layer 900 and the second electrode lead-out layer 901, the piezoelectric driving structure 9 can drive the position of the cantilever beam structure 501 to change, thereby controlling the position of the grating structure 500.

[0100] As an example, the grating material layer 5 is etched using a dry etching method to form the grating structure 500 and the cantilever beam structure 501.

[0101] Next, please refer to Figure 6 Step S4: Etch the substrate 1 to form a cavity 100 in the substrate 1, and expose the etching barrier layer 2 at a preset position in the cavity 100.

[0102] As an example, the cavity 100 is formed by etching from the side of the substrate 1 away from the etch barrier layer 2 using a deep silicon etching process, wherein the etch barrier layer 2 serves as an etch barrier for the deep silicon etching process to avoid damage to the diaphragm material layer 3 during the formation of the cavity 100.

[0103] As an example, the projection of the cavity 100 onto the diaphragm material layer 3 overlaps the projection of the grating structure 500 onto the diaphragm material layer 3.

[0104] As an example, the substrate 1 is etched using a dry etching method to form the cavity 100.

[0105] Next, please refer to Figure 7 Step S5: Remove the sacrificial layer 4 below the grating structure 500 and the cantilever beam structure 501 to form a gap 400 between the grating structure 500 and the diaphragm material layer 3 and between the cantilever beam structure 501 and the diaphragm material layer 3, and remove the exposed etching barrier layer 2 to expose the diaphragm material layer 3. The exposed diaphragm material layer 3 constitutes the diaphragm structure 300.

[0106] As an example, the sacrificial layer 4 at a predetermined position is etched using a dry etching method to form the gap 400, wherein the sacrificial layer 4 is used to determine the distance between the grating structure 500 and the diaphragm structure 300.

[0107] As an example, the etch barrier layer 2 exposed in the cavity 100 region is removed by dry etching to expose the diaphragm material layer 3.

[0108] For example, please refer to Figure 8 and Figure 9 The figures show a top view and a bottom view of the diaphragm structure formed in this embodiment of the invention. In this embodiment, the piezoelectric drive structure 9 has a ring-shaped body, which is arranged around the periphery of the grating structure 500. A cantilever beam structure 501 is disposed between the piezoelectric drive structure 9 and the grating structure 500, wherein the piezoelectric drive structure 9 extends onto the cantilever beam structure 501. Specifically, in this embodiment, the piezoelectric drive structure 9 has a ring-shaped body, the grating structure 500 is located at the center of the ring formed by the piezoelectric drive structure 9, and multiple cantilever beam structures 501 are evenly arranged between the piezoelectric drive structure 9 and the grating structure 500 so that the piezoelectric drive structure 9 can provide a uniform driving force to the grating structure 500.

[0109] For example, please refer to Figure 10 After forming the gap 400 and the diaphragm structure 300, the method further includes forming a reflective layer 11 on the side of the grating structure 500 away from the diaphragm structure 300 to improve optical reflectivity and reduce loss. Specifically, in this embodiment, the reflective layer 11 is a metal reflective layer made of gold.

[0110] As an example, the microphone sensor works as follows: When the grating structure 500 is illuminated by a light source, first-order diffracted light is obtained according to the principle of grating diffraction. The diaphragm structure 300 vibrates under the excitation of external sound, causing a change in the distance between the grating structure 500 and the diaphragm structure 300. This change in the intensity of the first-order diffracted light is converted into a change in electrical signal for output. Please refer to [link to relevant documentation]. Figure 11 After forming the reflective layer 11, the following steps are also included:

[0111] A cover plate 12 is provided and fixed above the grating material layer 5. The side of the cover plate 5 is located around the piezoelectric drive structure 9. A laser 1200 and a photodetector 1201 are provided on the top surface of the cover plate 12 facing the grating structure 500. A plurality of cover plate pads 1202 are provided on the top surface of the cover plate 12 away from the grating structure 500. Some of the cover plate pads 1202 are electrically connected to the laser 1200 through through-silicon vias, and some of the cover plate pads 1202 are electrically connected to the photodetector 1201 through through-silicon vias.

[0112] As an example, the laser 1200 and the photodetector 1201 are mounted on the top surface of the cover plate 12 using a mounting technique, and the laser 1200 and the photodetector 1201 are electrically connected to the cover plate pads 1202 using through-silicon vias (TSVs). Specifically, in this embodiment, the cover plate 12 is a silicon cover plate, and the laser 1200 is a vertical-cavity surface-mount laser (VCSEL).

[0113] As an example, the cover plate 12 is fixed to the grating material layer 5 using a top-mount patch technique. In this embodiment, since the insulating layer 10 is formed on the grating material layer 5, the cover plate 12 is fixed to the insulating layer 10. The steps of fixing the cover plate 12 to the insulating layer 10 include:

[0114] (i) Apply conductive silver paste to a predetermined position of the insulating layer 10;

[0115] (ii) The cover plate 12 is attached to the insulating layer 10 at the position with conductive silver paste by a chip mounter;

[0116] (iii) Curing at 150°C for 1 hour, the conductive silver paste is cured to bond and fix the cover plate 12 and the insulating layer 10.

[0117] As an example, the cover plate 12 does not cover the first electrode lead-out layer 900 and the second electrode lead-out layer 901, which facilitates the electrical lead-out of the piezoelectric drive structure 9.

[0118] As an example, the laser 1200 emits a laser beam to illuminate the grating structure 500, causing diffraction. When there is no external sound, the initial distance between the grating structure 500 and the diaphragm structure 300 is H. When external sound excites the diaphragm structure 300 to vibrate, the distance between the grating structure 500 and the diaphragm structure 300 changes by an amount ΔX.

[0119] ΔX=C×P

[0120] Where C is the mechanical sensitivity of the diaphragm, and P is the excitation sound pressure.

[0121] When the diaphragm structure 300 is excited by external sound to vibrate, the intensity change of the first-order diffracted light is expressed by the following formula:

[0122]

[0123] Among them, I m I is the incident light intensity, λ is the incident light wavelength, and I ±1The intensity of the diffracted light is ±1st order. The photodetector 1201 detects the change in the intensity of the 1st order diffracted light and converts it into a change in electrical signal, ultimately realizing the physical quantity conversion of sound, light, and electricity, and completing the sound detection.

[0124] As an example, the cover plate 12 can provide protection for the laser 1200, the photodetector 1201, the piezoelectric drive structure 9, the cantilever beam structure 501, and the grating structure 500 on the one hand, and realize the integration among the laser 1200, the photodetector 1201, the piezoelectric drive structure 9, the cantilever beam structure 501, and the grating structure 500 on the other hand.

[0125] As an example, after fixing the cover plate 12 above the grating material layer 5, a step of encapsulation and protection is also included. See [link to relevant documentation]. Figure 12 The system provides a package housing 13 and a package substrate 14, which together form a package space. The substrate 1 is fixed to the package housing 13 or the package substrate 14. The piezoelectric drive structure 9 is electrically connected to the package housing 13 or the package substrate 14 via bonding wires 15, and the cover plate pad 1202 is electrically connected to the package housing 13 or the package substrate 14 via bonding wires 15.

[0126] Specifically, in this embodiment, the encapsulation shell 13 is provided with shell pads. First, the substrate 1 is fixed to the encapsulation shell 13. The first electrode lead-out layer 900 and the second electrode lead-out layer 901 are bonded to the shell pads through bonding wires 15. The cover plate pad 1202 is bonded to the shell pads through bonding wires 15. Then, the encapsulation shell 13 and the encapsulation substrate 14 are welded together through a welding process to achieve mechanical fixation and electrical connection between the encapsulation shell 13 and the encapsulation substrate 14.

[0127] As an example, both the encapsulation housing 13 and the encapsulation substrate 14 are provided with through holes to expose the cavity 100, that is, external sound waves can directly act on the diaphragm structure 300.

[0128] As an example, the packaging substrate 14 is a PCB board, and the signal measured by the photodetector 1201 is output through the transimpedance method circuit on the PCB board.

[0129] As an example, when the spacing H between the grating structure 500 and the diaphragm structure 300 satisfies the following relationship, the microphone sensor reaches its optimal linear operating point and its sensitivity reaches its maximum value.

[0130]

[0131] As an example, the current spacing between the grating structure 500 and the diaphragm structure 300 of the device is 2.07 μm, while the optimal linear operating point (the point of maximum sensitivity) has a spacing of 2.04 μm, which is 30 nm away from the optimal sensitivity point. By using the piezoelectric drive structure 9 to drive the grating structure 500, the distance between the grating structure 500 and the diaphragm structure 300 is adjusted to compensate for this 30 nm, so that the temporal response amplitude of the microphone sensor reaches its maximum, thereby further improving both sensitivity and signal-to-noise ratio. This has a significant advantage in controlling the optimal responsivity.

[0132] As an example, the grating structure 500 was illuminated with an 850nm near-infrared laser, and the time-domain response signal of the device was measured under an external sound source with a frequency of 1kHz and a sound pressure level of 1Pa. Please refer to [link to relevant documentation]. Figure 13 The graph is shown as a time-domain response curve in an embodiment of the present invention. Figure 13 As can be seen, the piezoelectrically tuned microphone sensor in this embodiment has a fast response speed and can quickly respond to external sound signals.

[0133] For example, please refer to Figure 14 The graph shown is a response curve illustrating the sensitivity as a function of frequency in an embodiment of the present invention. At a frequency of 1 kHz and a sound pressure level of 1 Pa, the device's sensitivity is 95.2 mV / Pa, indicating that the microphone sensor of this application has high sensitivity. From... Figure 14 As can be seen, unstable fluctuations occur after the frequency exceeds 4kHz. This may be due to factors such as bandwidth limitation caused by the test fixture and the test environment.

[0134] For example, please refer to Figure 15 The graph shown is a logarithmic spectrum plot measured at 1 kHz in an embodiment of the present invention. Figure 15 It can be seen that the signal value is -25.0dB, the average noise value is -91.2dB, and the signal-to-noise ratio is 66.2dB, indicating that the piezoelectrically tuned microphone sensor in this embodiment has a high signal-to-noise ratio.

[0135] As described above, in the piezoelectrically tuned microphone sensor fabrication method of this embodiment, piezoelectric driving is used to achieve optimal sensitivity control. This not only has advantages such as low noise, high sensitivity, high integration, and large operating bandwidth, but also avoids failure caused by the attraction effect due to electrostatic control, and has the advantage of further improving the signal-to-noise ratio and operating bandwidth. In addition, the grating structure and diaphragm structure are integrated and fabricated using surface treatment, eliminating the need for bonding. This avoids the accuracy alignment problem and thermal stress problem caused by bonding process, reduces process complexity, eliminates the need for post-assembly, and has the advantage of mass production consistency.

[0136] Thus, a piezoelectrically tunable microphone sensor has been fabricated. Please refer to [link / reference]. Figure 10The piezoelectrically tuned microphone sensor includes a substrate 1, a cavity 100, a sacrificial layer 4, a co-layered grating material layer 5, a cantilever beam structure 501, and a piezoelectric driving structure 9. An etching barrier layer 2 is disposed on the substrate 1, and a diaphragm material layer 3 is disposed on the etching barrier layer 2. The cavity 100 penetrates the substrate 1 and the etching barrier layer 2, exposing the diaphragm material layer 3 at a predetermined position. The exposed diaphragm material layer 3 constitutes the diaphragm structure 300. The sacrificial layer 4 is located above the diaphragm material layer 3. The co-layered grating material layer 5, cantilever beam structure 501, and grating structure 500 are located above the sacrificial layer 4. The cantilever beam structure 501... One end of the cantilever beam structure 501 is connected to the grating material layer 5, and the other end of the cantilever beam structure 501 is connected to the grating structure 500. A gap 400 is provided between the grating structure 500 and the diaphragm material layer 3, and between the cantilever beam structure 501 and the diaphragm material layer 3. The piezoelectric driving structure 9 is located above the grating material layer 5 and extends above the cantilever beam structure 501. The piezoelectric driving structure 9 includes a first electrode layer 600, a piezoelectric layer 700, and a second electrode layer 800 stacked from bottom to top. The piezoelectric driving structure 9 can drive the position of the cantilever beam structure 501 to change, thereby controlling the distance between the grating structure 500 and the diaphragm structure 300.

[0137] As an example, the substrate 1 is made of silicon, the etching barrier layer 2 is made of silicon oxide, the diaphragm material layer 3 is made of polycrystalline silicon, the sacrificial layer 4 is made of silicon oxide, the grating material layer 5, the cantilever beam structure 501 and the grating structure 500 are made of polycrystalline silicon, the first electrode layer 600 is made of molybdenum, the piezoelectric material 700 is made of aluminum scandium nitride (AlScN), and the second electrode layer 800 is made of molybdenum.

[0138] As an example, it also includes:

[0139] An insulating layer 10 is located above the grating material layer 5 and covers the piezoelectric drive structure 9;

[0140] The first electrode lead-out layer 900 penetrates the insulating layer 10 and is electrically connected to the first electrode layer 600;

[0141] The second electrode lead-out layer 901 penetrates the insulating layer 10 and is electrically connected to the second electrode layer 800.

[0142] As an example, the insulating layer 10 is used to provide insulation protection for the piezoelectric drive structure 9, and the insulating layer 10 is appropriately thick to prevent the piezoelectric drive structure 9 from short-circuiting.

[0143] As an example, the sacrificial layer 4 between the grating structure 500 and the diaphragm material layer 3 and between the cantilever beam structure 501 and the diaphragm material layer 3 are etched away to form the gap 400. The sacrificial layer 4 is used to determine the distance between the grating structure 500 and the diaphragm structure 300.

[0144] As an example, the grating structure 500 is provided with a reflective layer 11 away from the diaphragm structure 300 to improve optical reflectivity and reduce losses. Specifically, in this embodiment, the reflective layer 11 is a metal reflective layer made of gold.

[0145] For example, please refer to Figure 8 In this embodiment, the piezoelectric driving structure 9 has a ring-shaped body, which is arranged around the periphery of the grating structure 500. A cantilever beam structure 501 is disposed between the piezoelectric driving structure 9 and the grating structure 500, wherein the piezoelectric driving structure 9 extends onto the cantilever beam structure 501. Specifically, in this embodiment, the piezoelectric driving structure 9 has a ring-shaped body, the grating structure 500 is located at the center of the ring formed by the piezoelectric driving structure 9, and multiple cantilever beam structures 501 are evenly arranged between the piezoelectric driving structure 9 and the grating structure 500, so that the piezoelectric driving structure 9 can provide a uniform driving force to the grating structure 500.

[0146] For example, please refer to Figure 11 It also includes a cover plate 12, which is fixed above the grating material layer 5. The side of the cover plate 5 is located around the piezoelectric drive structure 9. A laser 1200 and a photodetector 1201 are provided on the top surface of the cover plate 12 facing the grating structure 500. A plurality of cover plate pads 1202 are provided on the top surface of the cover plate 12 away from the grating structure 500. Some of the cover plate pads 1202 are electrically connected to the laser 1200 through through silicon vias, and some of the cover plate pads 1202 are electrically connected to the photodetector 1201 through through silicon vias.

[0147] As an example, the laser 1200 and the photodetector 1201 are mounted on the top surface of the cover plate 12 using a mounting technique, and the laser 1200 and the photodetector 1201 are electrically connected to the cover plate pads 1202 using through-silicon vias (TSVs). Specifically, in this embodiment, the cover plate 12 is a silicon cover plate, and the laser 1200 is a vertical-cavity surface-mount laser (VCSEL).

[0148] As an example, the cover plate 12 does not cover the first electrode lead-out layer 900 and the second electrode lead-out layer 901, which facilitates the electrical lead-out of the piezoelectric drive structure 9.

[0149] For example, please refer to Figure 12 It also includes a package housing 13 and a package substrate 14, the package housing 13 and the package substrate 14 forming a package space, the substrate 1 being fixed to the package housing 13 or the package substrate 14, wherein the piezoelectric drive structure 9 is electrically connected to the package housing 13 or the package substrate 14 via bonding leads 15, and the cover plate pad 1202 is electrically connected to the package housing 13 or the package substrate 14 via bonding leads 15.

[0150] Specifically, in this embodiment, the encapsulation shell 13 is provided with shell pads, the substrate 1 is fixed to the encapsulation shell 13, the first electrode lead-out layer 900 and the second electrode lead-out layer 901 are bonded to the shell pads via bonding wires 15, and the cover plate pad 1202 is bonded to the shell pads via bonding wires 15; the encapsulation shell 13 and the encapsulation substrate 14 are welded together by a welding process to achieve mechanical fixation and electrical connection between the encapsulation shell 13 and the encapsulation substrate 14.

[0151] As an example, both the encapsulation housing 13 and the encapsulation substrate 14 are provided with through holes to expose the cavity 100, that is, external sound waves can directly act on the diaphragm structure 300.

[0152] In summary, the piezoelectrically tuned microphone sensor and its fabrication method of this invention utilize piezoelectric drive to achieve optimal sensitivity control. This not only offers advantages such as low noise, high sensitivity, high integration, and large operating bandwidth, but also avoids the failure caused by the attraction effect resulting from electrostatic control, further improving the signal-to-noise ratio and operating bandwidth. Furthermore, the integrated fabrication of the grating structure and diaphragm structure using surface treatment eliminates the need for bonding, avoiding the precision alignment and thermal stress problems associated with bonding processes, reducing process complexity, and eliminating the need for post-assembly, thus offering advantages for mass production with consistent results. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0153] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for manufacturing a piezoelectrically tuned microphone sensor, characterized in that, Includes the following steps: A substrate is provided, on which an etching barrier layer, a diaphragm material layer, a sacrificial layer, a grating material layer, a first electrode material layer, a piezoelectric material layer, and a second electrode material layer are formed from bottom to top. The first electrode material layer, the piezoelectric material layer and the second electrode material layer are etched to form a piezoelectric driving structure, wherein the piezoelectric driving structure includes a first electrode layer, a piezoelectric layer and a second electrode layer stacked from bottom to top; The grating material layer is etched to form a grating structure and a cantilever beam structure, wherein, in a planar layout, the grating structure is connected to the cantilever beam structure and the piezoelectric drive structure; The substrate is etched to form a cavity in the substrate, and the cavity exposes the etching barrier layer at a predetermined location; The sacrificial layer beneath the grating structure and the cantilever beam structure is removed to create gaps between the grating structure and the diaphragm material layer, and between the cantilever beam structure and the diaphragm material layer. The exposed etching barrier layer is then removed to expose the diaphragm material layer, which constitutes the diaphragm structure. The piezoelectric drive structure can drive the position of the cantilever beam structure to change, thereby controlling the distance between the grating structure and the diaphragm structure.

2. The method for manufacturing a piezoelectrically tuned microphone sensor according to claim 1, characterized in that, Before etching the grating material layer, the following steps are also included: An insulating layer covering the piezoelectric drive structure is formed on the grating material layer; A first electrode lead-out layer and a second electrode lead-out layer are formed. The first electrode lead-out layer penetrates the insulating layer and is electrically connected to the first electrode layer. The second electrode lead-out layer penetrates the insulating layer and is electrically connected to the second electrode layer.

3. The method for manufacturing a piezoelectrically tuned microphone sensor according to claim 1, characterized in that: In a planar layout, the body of the piezoelectric drive structure is arranged around the periphery of the grating structure.

4. The method for manufacturing a piezoelectrically tuned microphone sensor according to claim 1, characterized in that: After forming the gap and the diaphragm structure, the method further includes forming a reflective layer on the side of the grating structure away from the diaphragm structure.

5. The method for manufacturing a piezoelectrically tuned microphone sensor according to claim 1, characterized in that, After forming the gap and the diaphragm structure, the method further includes the following steps: A cover plate is provided and fixed above the grating material layer. The side portion of the cover plate is located around the piezoelectric drive structure. A laser and a photodetector are provided on the top surface of the cover plate facing the grating structure. A plurality of cover plate pads are provided on the top surface of the cover plate away from the grating structure. Some of the cover plate pads are electrically connected to the laser through through-silicon vias, and some of the cover plate pads are electrically connected to the photodetector through through-silicon vias.

6. The method for manufacturing a piezoelectrically tuned microphone sensor according to claim 5, characterized in that, After fixing the cover plate above the grating material layer, the following steps are also included: A package housing and a package substrate are provided, and the substrate is fixed to the package housing or the package substrate. The piezoelectric drive structure is electrically connected to the package housing or the package substrate via bonding wires, and the cover plate pad is electrically connected to the package housing or the package substrate via bonding wires.

7. A piezoelectrically tuned microphone sensor, characterized in that, include: A substrate, wherein an etching barrier layer is disposed on the substrate, and a diaphragm material layer is disposed on the etching barrier layer; A cavity, penetrating the substrate and the etch barrier layer to expose the diaphragm material layer at a predetermined position, wherein the exposed diaphragm material layer constitutes a diaphragm structure; The sacrificial layer is located above the diaphragm material layer; A grating material layer, a cantilever beam structure, and a grating structure are arranged on the same layer and located above the sacrificial layer. One end of the cantilever beam structure is connected to the grating material layer, and the other end of the cantilever beam structure is connected to the grating structure. There are gaps between the grating structure and the diaphragm material layer, as well as between the cantilever beam structure and the diaphragm material layer. A piezoelectric driving structure is located above the grating material layer and extends above the cantilever beam structure. The piezoelectric driving structure includes a first electrode layer, a piezoelectric layer, and a second electrode layer stacked from bottom to top. The piezoelectric drive structure can drive the position of the cantilever beam structure to change, thereby controlling the distance between the grating structure and the diaphragm structure.

8. The piezoelectrically tuned microphone sensor according to claim 7, characterized in that, Also includes: An insulating layer is located above the grating material layer, covering the piezoelectric drive structure; The first electrode lead-out layer penetrates the insulating layer and is electrically connected to the first electrode layer; The second electrode lead-out layer penetrates the insulating layer and is electrically connected to the second electrode layer.

9. The piezoelectrically tuned microphone sensor according to claim 7, characterized in that: In a planar layout, the body of the piezoelectric drive structure is arranged around the periphery of the grating structure.

10. The piezoelectrically tuned microphone sensor according to claim 7, characterized in that: The grating structure has a reflective layer on the side away from the diaphragm structure.

11. The piezoelectrically tuned microphone sensor according to claim 7, characterized in that: It also includes a cover plate, which is fixed above the grating material layer. The side of the cover plate is located around the piezoelectric drive structure. A laser and a photodetector are provided on the top surface of the cover plate facing the grating structure. A plurality of cover plate pads are provided on the top surface of the cover plate away from the grating structure. Some of the cover plate pads are electrically connected to the laser through through-silicon vias, and some of the cover plate pads are electrically connected to the photodetector through through-silicon vias.

12. The piezoelectrically tuned microphone sensor according to claim 11, characterized in that: It also includes a package shell and a package substrate, the package shell and the package substrate forming a package space, the substrate being fixed to the package shell or the package substrate, wherein the piezoelectric drive structure is electrically connected to the package shell or the package substrate via bonding wires, and the cover plate pad is electrically connected to the package shell or the package substrate via bonding wires.

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