CN217470278U - Acoustic piezoelectric thin film device structure - Google Patents
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- CN217470278U CN217470278U CN202122394144.8U CN202122394144U CN217470278U CN 217470278 U CN217470278 U CN 217470278U CN 202122394144 U CN202122394144 U CN 202122394144U CN 217470278 U CN217470278 U CN 217470278U
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Abstract
The utility model provides an acoustics piezoelectric film device structure, include: a support body; the piezoelectric film structure covers the area surrounded by the support body, the periphery of the piezoelectric film structure is fixedly connected to the support body, the piezoelectric film structure comprises a piezoelectric layer and electrode layers covering the upper surface and the lower surface of the piezoelectric layer, the piezoelectric film structure comprises an inner area and an outer area surrounding the inner area, an electrode partition area is arranged between the inner area and the outer area, and the electrode partition area divides the electrode layers into a central electrode layer and a peripheral electrode layer. The utility model discloses an acoustics piezoelectricity rete structure can reduce piezoelectricity rete structure's angularity and the increase of the slit region sound-transmitting channel width that the control warpage arouses, and the utility model discloses an electrode layer covers piezoelectricity rete surface comprehensively and can realize the electromechanical conversion of piezoelectricity rete total area through vertical many piezoelectricity layer and horizontal many electrode layers between novel cutting apart with series connection or parallelly connected electricity connected mode, improvement electromechanical conversion efficiency.
Description
Technical Field
The invention belongs to the field of acoustic sensing, and particularly relates to an acoustic piezoelectric thin film device structure.
Background
In recent years, MEMS acoustic devices manufactured by using MEMS (micro electro mechanical systems) technology have been widely used in devices such as smart phones. Meanwhile, electronic devices such as smart phones, wearable products, motion cameras, digital cameras, and the like, which have a function of recognizing surrounding conditions by sound or a sound production function, have made higher demands for further miniaturization and signal-to-noise ratio characteristics of MEMS acoustic devices. MEMS acoustic devices are receiving attention due to their advantages such as high sensitivity, low power consumption, and flat frequency response, and are becoming the mainstream of the micro acoustic device market today.
MEMS piezoelectric transducers on the market at present have different working frequency bands and working modes according to application requirements, such as human ear audible frequency band (20Hz-20KHz) and ultrasonic frequency band (>20KHz), the transducers also distribute transmitter (Tx) and receiver (Rx), and the transducers also can work in a resonant state or a non-resonant state according to the application requirements. However, the main structure and basic operation principle of the piezoelectric unit are similar, and a general MEMS piezoelectric transducer includes a substrate, a support and a piezoelectric diaphragm structure. The diaphragm structure is mostly composed of relatively independent diaphragms in fan shape, triangle shape or other symmetrical structures, one end of the diaphragm is fixed on the supporting member, and the other end or the central area has relative freedom degree, and can be a cantilever beam or a diaphragm structure.
On one hand, when the traditional cantilever beam structure design has residual stress after process manufacturing, the initial warping of the free end of the structure is large, for example, a low-frequency (20Hz-20KHz) receiver (Rx) is applied, and the initial warping greatly changes the size of a sound-transmitting slit structure of a transducer, and further, in a working state, the structure vibrates along with the influence of incident sound waves and also changes the size of the sound-transmitting slit structure along with the vibration amplitude, so that the frequency response of a lower frequency band of the receiver is influenced (for example, under the condition that the working frequency is less than 5 KHz). Meanwhile, the cantilever beam structure has certain reliability problem when dealing with large sound pressure level impact or large voltage sounding.
On the other hand, whether it is a transmitter (Tx) or a receiver (Rx) (e.g. piezoelectric ultrasonic transducer — pMUT), the effective piezoelectric area does not completely cover the whole mechanical structure area (typically only occupies about 50% of the effective area). Resulting in a large amount of mechanical energy not being efficiently converted into electrical energy in the receiving state, and vice versa in the transmitting mode.
SUMMERY OF THE UTILITY MODEL
In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide an acoustic piezoelectric thin film device structure for solving the problems of low reliability and low effective piezoelectric area of the conventional cantilever beam structure in the prior art.
To achieve the above and other related objects, the present invention provides an acoustic piezoelectric thin film device structure, including: a support body; piezoelectric film layer structure, piezoelectric film layer structure covers the region that the supporter surrounds, piezoelectric film layer structure's periphery fixed connection in on the supporter, piezoelectric film layer structure include the piezoelectric layer and cover in the electrode layer of all surfaces about the piezoelectric layer, piezoelectric film layer structure include the interior region and encircle in the exterior region of interior region, have the electrode partition district between interior region and the exterior region, the electrode partition district will central electrode layer and peripheral electrode layer are cut apart into to the electrode layer.
Optionally, the piezoelectric film layer structure has a plurality of slit regions, the slit regions penetrate through the piezoelectric film layer structure in the longitudinal direction to divide the piezoelectric film layer structure into a plurality of piezoelectric unit regions, the slit regions extend from the periphery of the piezoelectric film layer structure in the lateral direction toward the central point of the piezoelectric film layer structure and have a distance from the central point, so as to leave a central connection portion mechanically connecting the piezoelectric unit regions in the center of the piezoelectric film layer structure, and a physical division region of the piezoelectric layer caused by the slit regions may be the same as or different from a physical region of the piezoelectric effective electrical unit caused by electrode division, depending on specific requirements.
Optionally, the ratio of the area of the central connection portion to the total area of the piezoelectric film structure is between 5% and 95%.
Optionally, the piezoelectric film structure includes a first piezoelectric layer and a second piezoelectric layer in a longitudinal direction, an upper surface of the first piezoelectric layer is covered with a first electrode, a lower surface of the second piezoelectric layer is covered with a second electrode, a third electrode is covered between the first piezoelectric layer and the second piezoelectric layer, the piezoelectric film structure includes an inner area and an outer area surrounding the inner area in a transverse direction, an electrode partition area is provided between the inner area and the outer area, and divides the first electrode into a first central electrode and a first peripheral electrode, and divides the second electrode into a second central electrode and a second peripheral electrode, and divides the third electrode into a third central electrode and a third peripheral electrode.
Optionally, the piezoelectric film layer structure has a plurality of slit regions, the slit regions penetrate through the first electrode, the first piezoelectric layer, the third electrode, the second piezoelectric layer and the second electrode in the longitudinal direction, the slit regions physically divide the piezoelectric film layer structure into a plurality of piezoelectric unit regions, the electrical division of the piezoelectric layers is determined by the electrode structure, the electrode division may be the same as or different from the division of the slit regions, the slit regions extend from the periphery of the piezoelectric film layer structure in the lateral direction toward the central point of the piezoelectric film layer structure and have a distance from the central point, so as to leave a central connection portion mechanically connecting the piezoelectric unit regions in the center of the piezoelectric film layer structure, and the ratio of the area of the central connection portion to the total area of the piezoelectric film layer structure is between 5% and 95%.
Optionally, a plurality of said piezoelectric units operate at the same vibration phase and vibration frequency.
Optionally, the surface of the central connection has an electrode or insulation.
Optionally, the shape of the plurality of piezoelectric units divided by the slit region is symmetrical and the area of the plurality of piezoelectric units is the same.
Optionally, the width of the slit region is less than or equal to 10 microns.
Optionally, the first central electrode, the first piezoelectric layer, and the third central electrode in the same piezoelectric unit region form a first central capacitor, the third central electrode, the second piezoelectric layer, and the second central electrode form a second central capacitor, the first peripheral electrode, the first piezoelectric layer, and the third peripheral electrode form a first peripheral capacitor, the third peripheral electrode, the second piezoelectric layer, and the second peripheral electrode form a second peripheral capacitor, and the first central capacitor, the second central capacitor, the first peripheral capacitor, and the second peripheral capacitor are insulated, connected in parallel, connected in series, or connected in series-parallel.
Optionally, the first central capacitor, the second central capacitor, the first peripheral capacitor and the second peripheral capacitor of the plurality of piezoelectric unit regions are mutually insulated, connected in parallel, connected in series or connected in series-parallel.
Alternatively, power is supplied only through two ports (e.g., high voltage source-V) through the interconnection between the piezoelectric layer and the electrodes dd And ground-GND, or positive and negative power (V + and V-) supply, by applying electrical signals in opposite directions (e.g., V) to the outer and inner regions when the transducer structure is transmitting signals dd And GND, or positive and negative power supplies V + and V-), so that the mechanical amplitude of the piezoelectric film layer structure is increased, and when the transducer structure receives signals, the signals at a receiving end are maximized by superposing two paths of electric signals of an external area and an internal area.
Optionally, the support is a polygonal ring, the piezoelectric film structure covers an area surrounded by the support in a polygonal surface shape, the polygonal ring includes one of a regular trilateral ring, a regular quadrilateral ring, a regular pentagonal ring, a regular hexagonal ring and a regular octagonal ring, and the shape of the support and the shape of the piezoelectric film structure may be correlated or uncorrelated.
Optionally, the slit region extends from a corner end of the polygonal ring towards a midpoint of the polygonal ring.
Optionally, the support is a circular ring or an elliptical ring, the piezoelectric film structure is covered on the area surrounded by the support in a circular surface shape, and the shape of the support and the shape of the piezoelectric film structure may be related or unrelated
Optionally, the slit region extends from the circumferential edge of the circular ring shape towards the center of the circular ring shape.
Optionally, the piezoelectric layer material comprises AlN, AlN material doped based on different ratios, PZT,PMN-PT, ZnO, PVDF and LiNbO 3 One kind of (1).
Optionally, the acoustic piezoelectric thin film device structure is a transmitter or a receiver, and the acoustic piezoelectric thin film device structure operates in a resonant mode or a non-resonant frequency.
As described above, the utility model discloses an acoustics piezoelectric thin film device structure has following beneficial effect:
the utility model provides an acoustic piezoelectric diaphragm structure, the outer ring of which is fixed on a support body, a slit area (namely an acoustic transmission channel) and the size of which are added or adjusted on the diaphragm structure by a semiconductor process, and the acoustic piezoelectric diaphragm structure has advantages in controlling the initial warping caused by prestress; under the same prestress, the initial warping of the acoustic piezoelectric diaphragm structure is about one tenth of that of a cantilever beam structure, and the mechanical stability of the transducer is ensured.
The utility model provides an acoustics piezoelectricity rete structure is when being used as the transducer, because the uniformity of middle slit district width just does not change along with the warpage, the low frequency response of transducer can not reduce because of the diminishing of slit district acoustic resistance, has promoted acoustics receiver low frequency dynamic sensitivity. Meanwhile, on the premise of releasing equal areas of the structures, the operable bandwidth of a high-frequency flat band of the transducer (such as a receiver) is expanded.
The utility model provides an electric potential distribution opposite direction in acoustics piezoelectricity rete structure outer lane and inner circle region, the absolute value size is close, utilizes double-deck piezoelectricity rete structure and only two electric port (if, V + and V-), can realize: 1) the receiver can respectively connect the electrodes in the outer ring area and the inner ring area to output signals, and the sensitivity of the receiving end is enhanced in a series-parallel combination mode; 2) the emitter can also load signals through a double-layer structure to enhance the intensity of the acoustic signals at the emitting end. Compare general cantilever beam or single piezoelectric layer transducer, the utility model discloses a mechanical energy and signal of telecommunication utilization rate increase the one time, have improved the receiving and dispatching end performance of transducer.
The utility model discloses an acoustics piezoelectricity rete structure can reduce the increase of the slit district sound transmission channel width that piezoelectricity rete structure's angularity and control warpage arouse, and the utility model discloses an electrode layer covers piezoelectricity rete surface comprehensively and can be through vertical many piezoelectric layers and horizontal many electrode layers between the novelty cut apart with series connection or parallelly connected electricity connected mode, realize the electromechanical conversion of piezoelectricity rete total area, improve the electromechanical transformation efficiency of piezoelectric film device.
Drawings
Fig. 1 is a schematic perspective view of the structure of the acoustic piezoelectric thin-film device according to this embodiment, fig. 2 is a schematic sectional view of the structure of the acoustic piezoelectric thin-film device according to this embodiment, and fig. 3 is a schematic back-side view of the structure of the acoustic piezoelectric thin-film device according to this embodiment.
Fig. 4 to fig. 10 are schematic diagrams showing several structures of the structure of the acoustic piezoelectric thin film device of the present invention.
Fig. 11 and fig. 12 respectively show the flexibility diagrams of a plurality of cantilever beam structures and the structure of the acoustic piezoelectric thin film device of the present invention.
Fig. 13 and 14 are deformation diagrams of a plurality of cantilever beam structures and the warped acoustic piezoelectric thin film device structure according to the present invention, respectively.
Fig. 15 shows an equivalent model diagram of the middle slit region in the acoustic theory.
Fig. 16 shows an equivalent circuit model of a receiving sensor.
Fig. 17 shows a graph of normalized displacement frequency response for a plurality of cantilever beam structures and the acoustic piezoelectric thin film device structure of the present invention.
Fig. 18 and fig. 19 show potential distribution diagrams of a plurality of cantilever beam structures and the structure of the acoustic piezoelectric thin film device of the present invention, respectively.
Fig. 20 and 21 show potential distribution diagrams of the double-layer piezoelectric film structure of the acoustic piezoelectric thin film device structure of the present invention.
Fig. 22 is a schematic electrode division diagram of a double-layer piezoelectric film structure of the acoustic piezoelectric thin film device structure according to the present invention.
Fig. 23 and 24 show equivalent circuit diagrams of electrode connections of the double-layer piezoelectric film structure of the acoustic piezoelectric thin film device structure according to the present invention.
Description of the element reference
10 support body
20 piezoelectric film layer structure
201 outer region
202 inner region
203 center connection part
204 first piezoelectric layer
205 second piezoelectric layer
206 first electrode
207 second electrode
208 third electrode
209 first center electrode
210 first peripheral electrode
211 second central electrode
212 second peripheral electrode
213 third center electrode
214 third peripheral electrode
215 electrode division area
30 slit area
40 back cavity structure
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The present invention can also be implemented or applied through other different specific embodiments, and various details in the present specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
As in the detailed description of the embodiments of the present invention, the cross-sectional views illustrating the device structure are not enlarged partially in general scale for the convenience of illustration, and the schematic views are only examples, which should not limit the scope of the present invention. In addition, the three-dimensional dimensions of length, width and depth should be included in the actual fabrication.
For convenience in description, spatial relational terms such as "below," "beneath," "below," "under," "over," "upper," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that these terms of spatial relationship are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the figures. Further, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.
In the context of this application, a structure described as a first feature being "on" a second feature may include embodiments where the first and second features are formed in direct contact, and may also include embodiments where additional features are formed in between the first and second features, such that the first and second features may not be in direct contact.
It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and only the components related to the present invention are shown in the drawings rather than being drawn according to the number, shape and size of the components in actual implementation, and the form, amount and ratio of the components in actual implementation may be changed at will, and the layout of the components may be more complicated.
As shown in fig. 1 to fig. 3, fig. 1 is a schematic perspective structural view of the structure of the acoustic piezoelectric thin film device of this embodiment, fig. 2 is a schematic sectional structural view of the structure of the acoustic piezoelectric thin film device of this embodiment, and fig. 3 is a schematic back structural view of the structure of the acoustic piezoelectric thin film device of this embodiment. The present embodiment provides an acoustic piezoelectric thin film device structure including: the piezoelectric film structure 20 comprises a support 10 and a piezoelectric film structure 20, the piezoelectric film structure 20 covers an area surrounded by the support, a periphery of the piezoelectric film structure 20 is fixedly connected to the support, unlike a cantilever beam structure, the piezoelectric film structure 20 does not have an independent suspension end, the piezoelectric film structure 20 comprises a piezoelectric layer and electrode layers covering the upper and lower surfaces of the piezoelectric layer, the piezoelectric film structure 20 comprises an inner area and an outer area surrounding the inner area, an electrode dividing area 215 is arranged between the inner area and the outer area, the electrode dividing area 215 divides the electrode layers into a central electrode layer and a peripheral electrode layer, in one embodiment, an area ratio of the central electrode layer to the peripheral electrode layer may be 4: 1-1: 4, for example, 2: 1-1: 2, preferably 1: 1. The piezoelectric film layer structure 20 covers the area surrounded by the support body 10 to form a back cavity structure 40 at the back of the piezoelectric film layer structure 20. In one embodiment, the support body 10 is a closed loop type support body.
The piezoelectric film layer structure 20 may be a single layer piezoelectric layer, a double layer piezoelectric layer or a multi-layer piezoelectric layer. As shown in fig. 4, 6, 8 and 10, the piezoelectric film layer structure 20 covers an area surrounded by the supporting body 10, a peripheral edge of the piezoelectric film layer structure 20 is fixedly connected to the supporting body 10, the piezoelectric film layer structure 20 includes a first piezoelectric layer 204 and a second piezoelectric layer 205 in a longitudinal direction, an upper surface of the first piezoelectric layer 204 is fully covered with a first electrode 206, a lower surface of the second piezoelectric layer 205 is fully covered with a second electrode 207, a third electrode 208 is fully covered between the first piezoelectric layer 204 and the second piezoelectric layer 205, the piezoelectric film layer structure 20 includes an inner area 202 and an outer area 201 surrounding the inner area 202 in a transverse direction, an electrode dividing area 215 is provided between the inner area 202 and the outer area 201, and the electrode dividing area 215 divides the first electrode 206 into a first central electrode and a first peripheral electrode, and the second electrode 207 is divided into a second central electrode and a second peripheral electrode, and the third electrode 208 is divided into a third central electrode and a third peripheral electrode. In one embodiment, the material of the first piezoelectric layer 204 and the second piezoelectric layer 205 comprises AlN, doped based on different ratiosAlN Material, PZT, PMN-PT, ZnO, PVDF and LiNbO 3 One kind of (1).
In one embodiment, as shown in fig. 5, 7, 9 and 10, wherein fig. 10 is a schematic cross-sectional structure view at a-a' in fig. 5, the piezoelectric film layer structure 20 has a plurality of slit regions 30, the slit regions 30 longitudinally penetrate through the first electrode 206, the first piezoelectric layer 204, the third electrode 208, the second piezoelectric layer 205 and the second electrode 207 to physically divide the piezoelectric film layer structure 20 into a plurality of piezoelectric unit regions, the slit regions 30 laterally extend from a periphery of the piezoelectric film layer structure 20 toward a central point of the piezoelectric film layer structure 20 and have a distance from the central point so as to leave a central connection portion 203 mechanically connecting the piezoelectric unit regions in the center of the piezoelectric film layer structure 20, a starting point of the slit region 30 may not be at the periphery of the piezoelectric film layer structure 20, but may be inside the outer region 201, even the starting point may be inside the inner region 202, and the ending point of the slit region 30 may be inside the outer region 201 and inside the inner region 202, preferably, the starting point of the slit region 30 is the periphery of the piezoelectric film layer structure 20, and the ending point is inside the inner region 202. The physical dividing area of the piezoelectric layer caused by the slit area may be the same as or different from the physical area of the piezoelectric effective electrical unit caused by the electrode division, depending on the specific requirements. The ratio of the area of the central connection portion 203 to the total area of the piezoelectric film layer structure 20 is between 5% and 95%, for example, in an embodiment, the ratio of the area of the central connection portion 203 to the total area of the piezoelectric film layer structure 20 is 10%, and of course, the radial dimension of the central connection portion 203 may be actually larger than the radial dimension of the inner region 202, in this case, the slit region 30 is only disposed in the outer region 201, the central connection portion 203 includes the inner region 202 and crosses over the electrode dividing region 215 to reach the outer region 201, but the central connection portion 203 does not change the original arrangement of the outer region 201, the inner region 202 and the electrode dividing region 215. In this embodiment, a slit area 30 may be formed in the first piezoelectric layer 204 and the second piezoelectric layer 205 by using a semiconductor processing technology, and the working frequency of the transducer structure is effectively adjusted by adjusting the size of the slit area 30 (and the size of the sound transmission channel), the size of the back cavity structure 40, and the thickness of the first piezoelectric layer 204 and the second piezoelectric layer 205, and through the semiconductor processing technology, the width of the slit area 30 may be set to be less than or equal to 10 micrometers, preferably, the width of the slit area 30 may be set to be 1-3 micrometers, so as to avoid the increase of the acoustic resistance, so that the piezoelectric film structure 20 of the present invention is suitable for acoustic transducers in various application scenarios and working modes, such as a transmitter or a receiver, and at the same time, the transmitter or the receiver may work in a resonant mode or a non-resonant frequency.
In one embodiment, a plurality of the piezoelectric units work at the same vibration phase and vibration frequency, so that signals of the plurality of piezoelectric units are mutually enhanced during work, and the sensitivity of the acoustic piezoelectric thin film device structure is improved.
In one embodiment, the center connection portion 203 physically connects the plurality of piezoelectric unit regions, the surface of the center connection portion 203 has an electrode or insulation, when the surface of the center connection portion 203 has an electrode, the inner regions 202 of the plurality of piezoelectric unit regions can be electrically connected together, and when the surface of the center connection portion 203 is insulated, the inner regions 202 of the plurality of piezoelectric unit regions can be electrically isolated.
In one embodiment, the slit region 30 divides a plurality of the piezoelectric units into symmetrical shapes and equal areas, so as to facilitate the adjustment and control of each piezoelectric unit.
In one embodiment, the first central electrode, the first piezoelectric layer and the third central electrode in the same piezoelectric unit area form a first central capacitor, the third central electrode, the second piezoelectric layer and the second central electrode form a second central capacitor, the first peripheral electrode, the first piezoelectric layer and the third peripheral electrode form a first peripheral capacitor, the third peripheral electrode, the second piezoelectric layer and the second peripheral electrode form a second peripheral capacitor, and the first central capacitor, the second central capacitor, the first peripheral capacitor and the second peripheral capacitor are insulated, connected in parallel, connected in series or connected in series-parallel. In one embodiment, the first central capacitor, the second central capacitor, the first peripheral capacitor and the second peripheral capacitor of a plurality of the piezoelectric unit areas are mutually insulated, connected in parallel, connected in series or connected in series-parallel. Utility model's an electrode layer covers piezoelectric layer surface and electrode layer comprehensively has novel segmentation and connected mode, can realize the piezoelectric transformation of full area, improves piezoelectric material utilization ratio.
In one embodiment, power is supplied only through two ports (e.g., high voltage source-V) through the interconnection between the piezoelectric layer and the electrodes dd And ground line-GND, or positive and negative power supply (V +)&V-) and the like) by applying opposing electrical signals (e.g., V) to the outer region 201 and the inner region 202 when the transducer structure is transmitting signals dd And GND, or positive and negative power supplies V + and V-), to increase the mechanical amplitude of the piezoelectric film structure, and to maximize the signal at the receiving end by superimposing the electrical signals of the outer region 201 and the inner region 202 in two ways when the transducer structure receives the signal.
As shown in fig. 6 and 8, the support 10 is a polygonal ring, and the piezoelectric film structure 20 covers a region surrounded by the support 10 in a polygonal surface shape. For example, the polygonal ring includes one of a regular trilateral ring, a regular quadrilateral ring, a regular pentagonal ring, a regular hexagonal ring and a regular octagonal ring, and the shape of the support 10 and the shape of the piezoelectric film layer structure 20 may be related or unrelated.
In one embodiment, as shown in fig. 6, the polygonal ring comprises a regular hexagonal ring, and the piezoelectric film structure 20 is covered in a polygonal surface shape in the area surrounded by the supporting body 10.
In one embodiment, as shown in fig. 8, the polygonal ring comprises a regular quadrilateral ring, and the piezoelectric film structure 20 is covered in a polygonal surface shape in the area surrounded by the supporting body 10.
As shown in fig. 7 and 9, the support 10 is a polygonal ring, and the piezoelectric film structure 20 is covered on the region surrounded by the support 10 in a polygonal surface shape. For example, the polygonal rings include one of regular trilateral rings, regular quadrilateral rings, regular pentagonal rings, regular hexagonal rings, and regular octagonal rings. The piezoelectric film layer structure 20 has a plurality of slit regions 30, the slit regions 30 longitudinally penetrate the first electrode 206, the first piezoelectric layer 204, the third electrode 208, the second piezoelectric layer 205 and the second electrode 207 to divide the piezoelectric film layer structure 20 into a plurality of piezoelectric cell regions, and the slit regions 30 extend from the corner ends of the polygonal ring toward the middle point of the polygonal ring.
In one embodiment, as shown in fig. 4, the support body 10 is a circular ring or an elliptical ring, the piezoelectric film structure 20 is covered on the area surrounded by the support body 10 in a circular surface shape, and the shape of the support body 10 and the shape of the piezoelectric film structure 20 may be correlated or uncorrelated.
In one embodiment, as shown in fig. 5, the supporting body 10 is a circular ring or an elliptical ring, and the piezoelectric film structure 20 is covered on the area surrounded by the supporting body 10 in a circular surface shape. The piezoelectric film layer structure 20 has a plurality of slit regions 30, the slit regions 30 longitudinally penetrate through the first electrode 206, the first piezoelectric layer 204, the third electrode 208, the second piezoelectric layer 205 and the second electrode 207 to divide the piezoelectric film layer structure 20 into a plurality of piezoelectric unit regions, and the slit regions 30 extend from the circumferential edge of the circular ring shape toward the center of the circular ring shape.
As shown in fig. 11 and fig. 12, compared with a plurality of cantilever beam structures (fig. 11) of a general piezoelectric device, the acoustic piezoelectric thin film device structure (fig. 12) of the present invention has a smaller degree of flexure (pre-strain) due to the connection of the central region, and the degree of flexure of the acoustic piezoelectric thin film device structure of the present invention is about one tenth of that of the general cantilever beam structure under the pre-stress of 100MPa through the preliminary simulation calculation; because the MEMS piezoelectric device can generate residual stress in the manufacturing process, the residual stress can cause the device to deflect; under different deflections, the performance of a piezoelectric transducer (mostly a receiver) can be changed, and in order to ensure the consistency of the product performance, the consistency of the deflection degree of a device needs to be controlled; the general low-frequency (less than or equal to 20KHz) piezoelectric receiver has a structure with a plurality of cantilever beams, and the deflection degrees of the cantilever beams are inconsistent due to the process manufacturing reason; the diaphragm structure adopted by the acoustic piezoelectric film device structure of the utility model has better flexibility consistency in each area due to the connection of the central area; and because the utility model discloses an acoustics piezoelectricity film device structure is the diaphragm structure, even under the initial inflection of the same structure, the size change can not take place because of the change of stress or incident sound wave yet for the sound-transparent seam of diaphragm structure to optimize the frequency response of low-frequency channel (generally being less than or equal to 5 KHz). Further, the reliability of MEMS piezoelectric device also can be influenced to piezoelectric device's angularity, the utility model discloses a control warpage that acoustics piezoelectric film device structure can be better, consequently has better reliability.
As shown in fig. 13 and 14, where fig. 13 is a deformation diagram of the warped cantilever beam structure, it can be found that the closer to the free end side of the cantilever beam, the wider the hollow risk (and the sound-transmitting slit) area between the cantilever beam structures becomes; fig. 14 is a deformation diagram of the structure of the acoustic piezoelectric thin film device according to the present invention after warping, in which the size of the slit region remains substantially unchanged due to the connection of the middle region; due to the warping of the cantilever beam structure, the gap between the cantilever beams is enlarged, and through preliminary calculation, under the prestress of 100MPa, the gap in the tip area of the cantilever beam is increased by 3 times compared with the design value, so that the sensitivity of low-frequency response is greatly reduced. The specific theoretical model is as follows:
as shown in fig. 15, in the acoustic theory, when the thickness of the slit region satisfies the following condition, the acoustic impedance can be equivalent:
as shown in the above equation, t is the slit width, l is the length of the piezoelectric layer, d is the width of the piezoelectric layer, f is the operating frequency, η is the air viscosity coefficient, ρ is the air density, R slita Is an acoustic resistance, M slita For this purpose, the acoustic resistance R of the slit in the middle slit region 30 is slita Inversely proportional to the third power of the slit width t, the acoustic resistance R increases with the slit width t of the middle slit region 30 slita Decrease rapidly; acoustic resistance R slita The small size causes low-frequency signal leakage, and influences the low frequency of the piezoelectric acoustic device.
As shown in fig. 16, the low frequency sensitivity of the receiving sensor is affected by the size of the sound-transmitting hole and the back cavity, in addition to being related to the characteristics of the piezoelectric film layer structure 20; FIG. 16 shows an equivalent circuit model of a simple receiving sensor, which can find the equivalent acoustic resistance R of the middle slit region 30 Leak Equivalent acoustic capacitance C of rear chamber BackVolume Forming an RC high-pass filter circuit with a cut-off frequency of
Below the cut-off frequency, the sensitivity decreases by 20dB for every 10 times the frequency.
In order to ensure the sensitivity of low frequency, the low frequency cut-off frequency should be as low as possible, which requires that the acoustic resistance of the middle slit region 30 region is large, i.e. the width of the middle slit region should be as small as possible; compare in general cantilever beam formula receiving transducer, the utility model discloses an acoustics piezoelectric film device structure is because the connection of middle zone, and the degree of flexure is unanimous basically between each region, can not produce the sound leakage that arouses because misplace from top to bottom.
According to the analysis, the utility model discloses an acoustics piezoelectric thin film device structure has the advantage in the aspect of the slit district width in the middle of the control, can reduce RC circuit's cut-off frequency, improves low frequency sensitivity.
As shown in fig. 17, fig. 17 is a cantilever beam structure and the normalized displacement frequency response of the acoustic piezoelectric thin film device structure of the present invention, and the areas of the vibrating diaphragms of the two piezoelectric device structures to be compared are close to each other. The MEMS receiving sensor with the cantilever beam structure receives normalized displacement responses corresponding to the widths of the slit areas of 1um and 3um, and the low-frequency cut-off frequency is higher and the low-frequency displacement response is lower along with the increase of the width of the slit area; additionally, by the utility model discloses an acoustics piezoelectricity thin film device structure slit area 30 width is known for 1 um's normalized displacement response curve, the utility model discloses an acoustics piezoelectricity thin film device structure low frequency response can not descend because initial warpage.
As shown in fig. 17, be located the application frequency band for the cantilever beam structure between the black vertical short dotted line of the left and right sides, be located between the vertical long dotted line of the left and right sides the utility model discloses an audio frequency band of acoustics piezoelectric film device structure, the utility model discloses compare cantilever beam structure's audio frequency flat-frequency work bandwidth and increase about 2 k.
The prestress of a general cantilever beam type piezoelectric device enables the tail end of a cantilever beam to warp, the width of a middle slit area is increased after the warp, or due to the fact that the warp degrees of the cantilever beams are different, the cantilever beams are staggered up and down, the sound transmission area is also increased, and the factors can cause the acoustic resistance of a slit area 30 to be reduced; whether for the receiving sensor or the implementing sensor, the reduction in the mid-slit region acoustic resistance affects the low frequency response; the low-frequency signal leakage (sound leakage) caused by the reduction of the acoustic resistance of the middle slit area is reduced, and the low-frequency response of the piezoelectric device is reduced; compare in general cantilever beam formula piezoelectric transducer, the utility model discloses the structure does because the utility model discloses a be that diaphragm structure and not one end such as cantilever beam full degree of freedom structure on the incident sound wave direction has following advantage: 1) the most central area is sound-proof, the increase of the deflection degree has no influence on the central area, the mechanical stability and the yield are enhanced, 2) the deflection degrees among the areas are basically consistent, sound leakage caused by up-down dislocation can not be generated, and the dynamic response sensitivity of low frequency bands (less than or equal to 5KHz) is improved; 3) under the same prerequisite of structure release area, the utility model discloses a cantilever beam structure is crossed to the resonant frequency height of diaphragm structure, so the low frequency flat band bandwidth enlarges, has further optimized the dynamic frequency response scope as the low frequency receiver.
As shown in fig. 18 and fig. 19, wherein fig. 18 shows a potential distribution diagram of the cantilever structure, as can be seen from the figure, the potential direction is basically unchanged from the edge to the central region, and fig. 19 shows a potential distribution diagram of the acoustic piezoelectric thin film device structure of the present invention, the potential direction is changed from the edge to the central region, and the absolute values are the same but the directions are opposite. In the actual design, the electrode layers at the center and the edge of the piezoelectric device can be physically separated through the electrode partition region 215 and then connected in an electrical series or parallel connection mode, so that the utilization efficiency of the piezoelectric material is increased, and the whole area of the release structure is fully utilized.
As shown in fig. 20-21, the utility model relates to a Bimorph double-layer piezoelectric film structure 20, under the action of an external force in a uniform direction, it can be seen that the directions of the electric potentials of the upper layer and the lower layer are just opposite, the electric potentials of the outer ring and the inner ring of the same layer are opposite, and the absolute values are basically equal; compare in cantilever beam structure generally only utilizes the regional electrode of outer lane, the utility model discloses utilize the regional signal of telecommunication of outer lane and inner circle with same layer piezoelectric material to draw forth or the loading respectively, piezoelectric material's the area increase of utilizing is nearly one time (the area is close whole diaphragm release region), and the conversion efficiency of its mechanical energy and electric energy also increases one time to improve transducer reception and transmitting capacity.
As shown in fig. 22 to 24, the Bimorph double-layer piezoelectric film structure 20 is shown as a sectional view from the edge to the center of the piezoelectric film structure 20, which is only a half of the entire sectional view, and therefore only includes one fixed supporting structure; the electrode is divided by the electrode dividing region 215, and a signal is respectively led out or loaded, so that the utilization efficiency of the piezoelectric material can be improved. As shown in fig. 22 to 24, the double-layer piezoelectric film structure 20 of the present invention can be equivalent to four capacitors C1, C2, C3, and C4 as shown in the figure due to the division of the electrodes; the electrodes may be labeled as outer ring electrodes T1, M1, and B1, and the inner ring electrodes may be labeled as T2, M2, and B2.
As shown in fig. 23 and fig. 24, the structure of the acoustic piezoelectric thin film device of the present invention can be equivalent to a capacitor in a piezoelectric layer disposed between two electrode layers, and since the same layer of piezoelectric material is divided into two parts by different electrodes, the same layer of piezoelectric material can be equivalent to two capacitors, i.e. C1 and C3 on the same layer, or C2 and C4 on the same layer; in an embodiment, the Bimorph double-layer piezoelectric material of the present invention can be equivalent to four capacitors C1, C2, C3, C4 due to the double-layer structure, and the distribution of the control electrodes reaches C1 ═ C2 ═ C3 ═ C4, and the connection mode of the present invention can include the following:
1) by connecting the upper and lower capacitors in parallel (i.e., C1 and C2 are connected in parallel, and C3 and C4 are connected in parallel), the outer ring electrode and the inner ring electrode are connected in series (i.e., C1 and C2 are connected in parallel and then connected in series with C3 and C4), as shown in fig. 23.
2) After the upper capacitor and the lower capacitor are connected in parallel (namely, the C1 and the C2 are connected in parallel; c3 and C4 are connected in parallel), and the outer ring electrode and the inner ring electrode are connected in parallel (i.e., C1 and C2 are connected in parallel and then connected in parallel with C3 and C4), as shown in fig. 24.
The above electrical connections are only examples, and the same type of electrical connection may be established by series-parallel connection between different capacitors. In addition, this connection is applicable to any bimorph electrical signal connection combination of dual electrical ports (e.g., V + and V-), and is not limited to the examples listed herein.
As described above, the utility model discloses an acoustics piezoelectricity thin film device structure has following beneficial effect:
the utility model provides an acoustic piezoelectric diaphragm structure, the outer ring of which is fixed on a support body, a slit area (namely an acoustic transmission channel) and the size of which are added or adjusted on the diaphragm structure by a semiconductor process, and the acoustic piezoelectric diaphragm structure has advantages in controlling the initial warping caused by prestress; under the same prestress, the initial warping of the acoustic piezoelectric diaphragm structure is about one tenth of that of a cantilever beam structure, and the mechanical stability of the transducer is ensured.
The utility model provides an acoustics piezoelectricity rete structure is when being used as the transducer, because the uniformity of middle slit district width just does not change along with the warpage, the low frequency response of transducer can not reduce because of the diminishing of slit district acoustic resistance, has promoted acoustics receiver low frequency dynamic sensitivity. Meanwhile, on the premise that the release structures have equal areas, the operable bandwidth of the high-frequency flat band of the transducer (such as a receiver) is expanded.
The utility model provides an electric potential distribution opposite direction in acoustics piezoelectricity rete structure outer lane and inner circle region, the absolute value size is close, utilizes double-deck piezoelectricity rete structure and only two electric port (if, V + and V-), can realize: 1) the receiver can respectively connect the electrodes in the outer ring area and the inner ring area to output signals, and the sensitivity of the receiving end is enhanced in a series-parallel combination mode; 2) the emitter can also load signals through a double-layer structure, and the intensity of the acoustic signals at the emitting end is enhanced. Compare general cantilever beam or single piezoelectric layer transducer, the utility model discloses a mechanical energy and signal of telecommunication utilization rate increase one time, have improved the receiving and dispatching end performance of transducer.
The utility model discloses an acoustics piezoelectricity rete structure can reduce the increase of the slit district sound transmission channel width that piezoelectricity rete structure's angularity and control warpage arouse, and the utility model discloses an electrode layer covers piezoelectricity rete surface comprehensively and can be through vertical many piezoelectric layers and horizontal many electrode layers between the novelty cut apart with series connection or parallelly connected electricity connected mode, realize the electromechanical conversion of piezoelectricity rete total area, improve the electromechanical transformation efficiency of piezoelectric film device.
Therefore, the utility model effectively overcomes various defects in the prior art and has high industrial utilization value.
The above embodiments are merely illustrative of the principles and effects of the present invention, and are not to be construed as limiting the invention. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which may be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (18)
1. An acoustic piezoelectric thin film device structure, comprising:
a support body;
piezoelectric film layer structure, piezoelectric film layer structure covers the region that the supporter surrounds, piezoelectric film layer structure's periphery fixed connection in on the supporter, piezoelectric film layer structure include the piezoelectric layer and cover in the electrode layer of piezoelectric layer upper and lower surface, piezoelectric film layer structure include the interior region and encircle in the exterior region of interior region, have the electrode partition district between interior region and the exterior region, the electrode partition district will the electrode layer is cut apart into central electrode layer and peripheral electrode layer.
2. An acoustic piezoelectric thin film device structure according to claim 1, wherein: the piezoelectric film layer structure is provided with a plurality of slit areas, the slit areas penetrate through the piezoelectric film layer structure in the longitudinal direction so as to divide the piezoelectric film layer structure into a plurality of piezoelectric unit areas, the slit areas extend from the periphery of the piezoelectric film layer structure in the transverse direction towards the direction of the central point of the piezoelectric film layer structure and have a distance with the central point, and a central connecting portion mechanically connecting the piezoelectric unit areas is reserved in the center of the piezoelectric film layer structure.
3. An acoustic piezoelectric thin film device structure according to claim 2, wherein: the proportion of the area of the central connecting part to the total area of the piezoelectric film layer structure is 5-95%.
4. An acoustic piezoelectric thin film device structure according to claim 1, wherein: the piezoelectric film structure comprises a first piezoelectric layer and a second piezoelectric layer in the longitudinal direction, the upper surface of the first piezoelectric layer is completely covered with a first electrode, the lower surface of the second piezoelectric layer is completely covered with a second electrode, a third electrode is completely covered between the first piezoelectric layer and the second piezoelectric layer, the piezoelectric film structure transversely comprises an inner area and an outer area surrounding the inner area, an electrode partition area is arranged between the inner area and the outer area, and the electrode partition area divides the first electrode into a first central electrode and a first peripheral electrode and divides the second electrode into a second central electrode and a second peripheral electrode and divides the third electrode into a third central electrode and a third peripheral electrode.
5. An acoustic piezoelectric thin film device structure according to claim 4, wherein: the piezoelectric film layer structure is provided with a plurality of slit areas, the slit areas penetrate through the first electrode, the first piezoelectric layer, the third electrode, the second piezoelectric layer and the second electrode in the longitudinal direction, the slit areas physically divide the piezoelectric film layer structure into a plurality of piezoelectric unit areas, the slit areas extend from the periphery of the piezoelectric film layer structure in the direction of the central point of the piezoelectric film layer structure in the transverse direction and have a distance with the central point, a central connecting part mechanically connecting the piezoelectric unit areas is reserved in the center of the piezoelectric film layer structure, and the proportion of the area of the central connecting part to the total area of the piezoelectric film layer structure is 5% -95%.
6. An acoustic piezoelectric thin film device structure according to claim 2 or 5, wherein: the piezoelectric units work at the same vibration phase and vibration frequency.
7. An acoustic piezoelectric thin film device structure according to claim 2 or 5, wherein: the surface of the central connecting part is provided with an electrode or insulation.
8. An acoustic piezoelectric thin film device structure according to claim 2 or 5, wherein: the shape of the plurality of piezoelectric units divided by the slit area is symmetrical and the area of the plurality of piezoelectric units is the same.
9. An acoustic piezoelectric thin film device structure according to claim 2 or 5, wherein: the width of the slit region is less than or equal to 10 microns.
10. An acoustic piezoelectric thin film device structure according to claim 5, wherein: the first central electrode, the first piezoelectric layer and the third central electrode in the same piezoelectric unit area form a first central capacitor, the third central electrode, the second piezoelectric layer and the second central electrode form a second central capacitor, the first peripheral electrode, the first piezoelectric layer and the third peripheral electrode form a first peripheral capacitor, the third peripheral electrode, the second piezoelectric layer and the second peripheral electrode form a second peripheral capacitor, and the first central capacitor, the second central capacitor, the first peripheral capacitor and the second peripheral capacitor are mutually insulated, connected in parallel, connected in series or connected in series and parallel.
11. An acoustic piezoelectric thin film device structure according to claim 10, wherein: the first central capacitor, the second central capacitor, the first peripheral capacitor and the second peripheral capacitor of the piezoelectric unit areas are mutually insulated, connected in parallel, connected in series or connected in series-parallel.
12. An acoustic piezoelectric thin film device structure according to claim 10, wherein: through the interconnection between piezoelectric layer and the electrode, only through the dual-port power supply, through applying reverse electric signal in outside region and inside region when transducer structure transmission signal, and make the mechanical amplitude increase of piezoelectric film layer structure, through the electric signal double-circuit stack with outside region and inside region when transducer structure received signal, make receiving end signal maximize.
13. An acoustic piezoelectric thin film device structure according to claim 2, wherein: the support body is a polygonal ring, the piezoelectric film layer structure is covered in an area surrounded by the support body in a polygonal surface shape, and the polygonal ring comprises one of a regular trilateral ring, a regular quadrilateral ring, a regular pentagonal ring, a regular hexagonal ring and a regular octagonal ring.
14. An acoustic piezoelectric thin film device structure according to claim 13, wherein: the slit region extends from a corner end of the polygonal ring toward a midpoint of the polygonal ring.
15. An acoustic piezoelectric thin film device structure according to claim 2, wherein: the support body is a circular ring or an elliptical ring, and the piezoelectric film layer structure is in a circular surface shape and covers the area surrounded by the support body.
16. An acoustic piezoelectric thin film device structure according to claim 15, wherein: the slit region extends from the circumferential edge of the circular or elliptical ring towards the center of the circular or elliptical ring.
17. An acoustic piezoelectric thin film device structure according to claim 1, wherein: the piezoelectric layer material comprises AlN, AlN materials doped based on different proportions, PZT, PMN-PT, ZnO, PVDF and LiNbO 3 One kind of (1).
18. An acoustic piezoelectric thin film device structure according to claim 1, wherein: the acoustic piezoelectric thin film device structure is a transmitter or a receiver, and works in a resonant mode or a non-resonant frequency.
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