[ summary of the invention ]
The present invention is directed to overcome the above problems and to provide a piezoelectric performance testing method and a piezoelectric performance testing structure which are simple in structure and easy to test.
In order to achieve the above object, the present invention provides a piezoelectric performance testing method, which is applied to a piezoelectric performance test of a sample to be tested, wherein the sample to be tested includes a piezoelectric film, and the method includes the following steps:
step S1, inputting an alternating current signal to a signal input end of the sample to be detected;
s2, enabling the sample to be detected to generate deformation through inverse piezoelectric effect through the input alternating current signal, and converting the deformation into an electric signal and outputting the electric signal by the sample to be detected;
step S3, acquiring an output electric signal of a signal output end of the sample to be detected, wherein the output electric signal is generated by the piezoelectric film through a positive piezoelectric effect;
and step S4, performing signal amplification or signal processing on the output electric signal to obtain the piezoelectric coefficient of the piezoelectric film.
Preferably, the sample to be tested is tested in a vacuum state.
Preferably, the sample to be tested further includes a back-end circuit, and in step S4, the signal amplification or signal processing is implemented by the back-end circuit.
The invention also provides a piezoelectric performance testing structure, which comprises a substrate with a cavity, a piezoelectric layer, an upper electrode and a lower electrode, wherein the upper electrode and the lower electrode are attached to two opposite sides of the piezoelectric layer; the piezoelectric layer, the upper electrode and the lower electrode form an integrated structure, and the integrated structure is connected with the substrate through the lower electrode and is suspended above the cavity; the substrate, the piezoelectric layer, the upper electrode, and the lower electrode collectively form a resonator circuit; the upper electrode comprises a first upper electrode and a second upper electrode which are positioned at two opposite ends of the piezoelectric layer, the lower electrode comprises a first lower electrode and a second lower electrode which are positioned at two opposite ends of the piezoelectric layer, the first upper electrode is arranged corresponding to the first lower electrode, and the second upper electrode is arranged corresponding to the second lower electrode; the first upper electrode is used as a signal input end, the second upper electrode is used as a signal output end, the first lower electrode and the second lower electrode are grounded, or the first upper electrode and the second lower electrode are grounded, the first lower electrode is used as a signal input end, and the second lower electrode is used as a signal output end.
Preferably, the first upper electrode includes a plurality of electrodes, and the first lower electrode includes a plurality of electrodes; the second upper electrode includes a plurality of electrodes, and the second lower electrode includes a plurality of electrodes.
The invention also provides a piezoelectric performance test structure, which comprises a substrate with a cavity, a piezoelectric layer and a plurality of electrode layers attached to two opposite sides of the piezoelectric layer at intervals, wherein the electrode layers are three layers and comprise an upper electrode layer, a middle electrode layer and a lower electrode layer which are sequentially stacked, the piezoelectric layer, the upper electrode layer and the lower electrode layer form an integrated structure, one end of the integrated structure is connected with the substrate through the lower electrode layer, and the other end of the integrated structure is suspended above the cavity to form a cantilever beam; the substrate, the piezoelectric layer, and the electrode layer collectively form a resonator circuit; the cantilever beam is of a 5-layer stacked structure, and the piezoelectric layers are two layers and comprise a first piezoelectric layer and a second piezoelectric layer; the upper electrode layer comprises a first section of upper electrode, a second section of upper electrode and a third section of upper electrode which are mutually spaced; the middle electrode layer comprises a first section of middle electrode, a second section of middle electrode and a third section of middle electrode which are mutually spaced; the lower electrode layer comprises a first section of lower electrode, a second section of lower electrode and a third section of lower electrode which are mutually spaced; the first section middle electrode is a signal input end, and the first section upper electrode, the first section lower electrode and the second section middle electrode are all electrically connected to the ground; the second section upper electrode, the second section lower electrode and the third section middle electrode are all electrically connected and in a suspension state, and the third section upper electrode is electrically connected to the third section lower electrode and serves as the signal output end.
Preferably, the first segment upper electrode, the first segment middle electrode and the first segment lower electrode have overlapping portions in projection along the thickness direction when being arranged on the surfaces of the two opposite sides of the piezoelectric layer; the second section of upper electrode, the second section of middle electrode and the second section of lower electrode are arranged on the surfaces of two opposite sides of the piezoelectric layer, and the projections along the thickness direction of the second section of upper electrode, the second section of middle electrode and the second section of lower electrode are overlapped.
Compared with the prior art, the piezoelectric performance test method and the piezoelectric performance test structure provided by the invention comprise the following steps: step S1, inputting an alternating current signal to a signal input end of the sample to be detected; s2, enabling the sample to be detected to generate deformation through inverse piezoelectric effect through the input alternating current signal, and converting the deformation into an electric signal and outputting the electric signal by the sample to be detected; step S3, acquiring an output electric signal of a signal output end of the sample to be detected, wherein the output electric signal is generated by the piezoelectric film through a positive piezoelectric effect; and step S4, performing signal amplification or signal processing on the output electric signal to obtain the piezoelectric coefficient of the piezoelectric film. The method adopts the coupling of positive piezoelectric effect and inverse piezoelectric effect to realize the evaluation and test of the piezoelectric coefficient of the piezoelectric film, is applied to the direct electric drive and electric detection of the piezoelectric performance test method and the piezoelectric performance test structure of the piezoelectric film, has convenient operation, can be used for the wafer level test of the piezoelectric coefficient, and particularly can obtain the piezoelectric coefficient of an ultra-micro film structure; and the whole test system adopts electrical test, and the test system has simple structure and is easy to operate and test. Particularly, under the resonance state of the device, larger output voltage can be obtained, the detection of signals is facilitated, and the power frequency interference is reduced, so that the reliability of the piezoelectric coefficient obtained by the piezoelectric performance test method and the piezoelectric performance test structure of the film layer piezoelectric material is higher.
[ detailed description ] embodiments
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, the present invention provides a method for testing piezoelectric performance.
The piezoelectric performance test method is applied to the piezoelectric performance test of a sample to be tested. Wherein, the sample to be measured comprises a piezoelectric film.
The piezoelectric performance testing method comprises the following steps:
and step S1, inputting an alternating current signal to a signal input end of the sample to be detected.
And step S2, enabling the sample to be detected to generate deformation through inverse piezoelectric effect through the input alternating current signal, and converting the deformation into an electric signal and outputting the electric signal by the sample to be detected.
The inverse piezoelectric effect means that when an electric field is applied in the polarization direction of the dielectrics of the piezoelectric thin films, the dielectrics of the piezoelectric thin films generate mechanical deformation or mechanical pressure in a certain direction, and when the applied electric field is removed, the deformation or stress disappears. The positive piezoelectric effect is a phenomenon in which electric polarization occurs by deformation. When physical pressure is applied to the piezoelectric material, the electric dipole moment in the material body is shortened due to compression, and the piezoelectric material resists the change, so that equal positive and negative charges are generated on the opposite surfaces of the material to keep the material in an original shape. This phenomenon of electric polarization by deformation is called "positive piezoelectric effect".
And S3, acquiring an output electric signal of a signal output end of the sample to be detected, wherein the output electric signal is generated by the piezoelectric film through a positive piezoelectric effect.
Step S4, amplifying or processing the output electric signal to obtain the piezoelectric filmPiezoelectric coefficient d31。
In this embodiment, the sample to be tested further includes a back-end circuit. In step S4, the signal amplification or signal processing is implemented by the back-end circuit. It should be noted that the back-end circuit is a circuit commonly used in the art, and a designer selects a specific circuit structure and a specific circuit performance index according to actual product requirements, which are not described in detail herein.
To better realize the piezoelectric coefficient d31And measuring, namely reducing the influence of the external environment on the measurement, wherein in the embodiment, the sample to be measured is tested in a vacuum state.
The present invention provides a piezoelectric performance test structure 100. The piezoelectric performance test structure 100 is used for realizing the coupling of positive piezoelectric effect and inverse piezoelectric effect; and by reasonably optimizing the electrodes, the electrical parameters of the piezoelectric material can be obtained on the premise of not influencing the mechanical property.
(embodiment one)
The present embodiment is a first embodiment, and referring to fig. 2 to 3, the first embodiment provides a piezoelectric performance testing structure 100. The piezoelectric performance test structure 100 applies the piezoelectric performance test method.
Specifically, the piezoelectric performance testing structure 100 includes a substrate 4 having a cavity 40, a piezoelectric layer 1, and an upper electrode 2 and a lower electrode 3 attached to two opposite sides of the piezoelectric layer 1. Wherein, the piezoelectric layer 1 is a piezoelectric film.
The piezoelectric layer 1, the upper electrode 2 and the lower electrode 3 form an integrated structure, which is connected to the substrate 4 through the lower electrode 3 and suspended above the cavity 40. That is, the integrated structure is located at one side of the cavity 40 in the thickness direction of the piezoelectric performance test structure 100.
In this embodiment, the upper electrode 2 and the lower electrode 3 are respectively located at opposite ends of the long axis of the piezoelectric layer 1.
The substrate 4, the piezoelectric layer 1, the upper electrode 2 and the lower electrode 3 together form a resonator circuit, wherein one of the upper electrode 2 or the lower electrode 3 serves as a signal input terminal, and the other of the upper electrode 2 or the lower electrode 3 serves as a signal output terminal.
Specifically, the upper electrode 2 includes a first upper electrode 21 and a second upper electrode 22 attached to the same side of the piezoelectric layer 1, the first upper electrode 21 serves as the signal input terminal, and the second upper electrode 22 serves as the signal output terminal.
The lower electrode 3 includes a first lower electrode 31 and a second lower electrode 32 attached to the other side of the piezoelectric layer 1, and both the first lower electrode 31 and the second lower electrode 32 are electrically connected to ground.
In this embodiment, the piezoelectric layer 1 has a rectangular shape. The first upper electrode 21 and the first lower electrode 31 are arranged oppositely; the second upper electrode 22 and the second lower electrode 32 are arranged oppositely; the first upper electrode 21 and the second upper electrode 22 are respectively disposed at two opposite ends of a long axis of the piezoelectric layer 1. The structure is beneficial to the conversion of the positive piezoelectric effect and the inverse piezoelectric effect of the alternating current signal in the piezoelectric performance test structure 100, so that the piezoelectric coefficient d of the piezoelectric performance test structure 10031The evaluation and the test are easier and the accuracy is high.
In the present embodiment, the first upper electrode 21 includes a plurality of electrodes; the first lower electrode 31 includes a plurality; the first upper electrodes 21 and the first lower electrodes 31 correspond to each other one to one. The second upper electrode 22 includes a plurality. This structure makes the alternating current signal applied to the first upper electrode 21 and the first lower electrode 31 more uniform, thereby making the inverse piezoelectric effect of the piezoelectric layer 1 more likely to occur.
In the present embodiment, the second lower electrode 32 includes a plurality of electrodes; the second upper electrodes 22 correspond to the second lower electrodes 32 one to one. The structure makes the output electric signal generated by the deformation of the piezoelectric layer 1 easier to obtain, thereby leading the piezoelectric coefficient d of the piezoelectric layer 1 to be more easily obtained31The evaluation and the test are easier and the accuracy is high.
Referring to fig. 4, fig. 4 shows the piezoelectric coefficients d of the piezoelectric layers 1 according to the present invention31Voltage and time of output electric signal under the conditionA graph of the relationship (c). W1, W2, W3 and W4 are the piezoelectric coefficients d of the piezoelectric layer 1 (i.e., piezoelectric film)31Voltage-time curve of (d). Wherein, the relationships of W1, W2, W3 and W4 are as follows: w1 is 2.0 times d31W2 is 1.5 times d31W3 is 1.0 times d31W4 is 0.5 times d31As can be understood from the graphs of W1, W2, W3, and W4, the piezoelectric performance test method and the piezoelectric performance test structure 100 of the present invention can be applied to the piezoelectric coefficient d31The wafer level test can especially obtain the piezoelectric coefficient d of an ultra-micro film layer structure31。
In summary, the piezoelectric performance testing method and the piezoelectric performance testing structure 100 of the present invention adopt the positive piezoelectric effect and the inverse piezoelectric effect to couple, so as to realize the piezoelectric coefficient d of the piezoelectric layer 131And (4) evaluating and testing. Preferably, the piezoelectric performance testing method and the piezoelectric performance testing structure 100 are directly electrically driven and electrically tested, are convenient to operate, and can be used for the piezoelectric coefficient d31The wafer level test can especially obtain the piezoelectric coefficient d of an ultra-micro film layer structure31(ii) a And the whole test system adopts electrical test, and the test system has simple structure and is easy to operate and test. Especially, in the state of device resonance, a larger output voltage can be obtained, which is beneficial to signal detection and reduces power frequency interference, and the piezoelectric performance test method and the piezoelectric performance test structure 100 obtain the piezoelectric coefficient d31The reliability of (2) is higher.
(second embodiment)
Referring to fig. 5 to 6, the present invention also provides another piezoelectric performance testing structure 200, and both the piezoelectric performance testing structure 200 and the piezoelectric performance testing structure 100 apply the piezoelectric performance testing method.
The piezoelectric performance test structure 200 is different from the piezoelectric performance test structure 100 in that: the electrodes in the piezoelectric performance test structure 200 are at the same axial end of the piezoelectric film.
Specifically, the piezoelectric performance testing structure 200 includes a substrate 4a having a cavity 40a, a piezoelectric layer b, and a plurality of electrode layers c attached to two opposite sides of the piezoelectric layer b at intervals. Wherein the electrode layer c is two-layered and includes an upper electrode layer 1c, a middle electrode layer 2c and a lower electrode layer 3 c.
The piezoelectric layer b, the upper electrode layer 1c and the lower electrode layer 3c form an integrated structure, one end of the integrated structure is connected with the substrate 4a through the lower electrode layer 3c, and the other end of the integrated structure is suspended above the cavity 40a to form a cantilever beam.
The substrate 4a, the piezoelectric layer b and the electrode layers c together form a resonator circuit, wherein one or more of the electrode layers c serve as signal input terminals, wherein one or more of the electrode layers c serve as signal output terminals, and wherein one or more of the electrode layers c are suspended.
In this embodiment, the cantilever beam has a 5-layer stacked structure. The piezoelectric layer b is two-layered and includes a first piezoelectric layer b1 and a second piezoelectric layer b 2.
Specifically, the upper electrode layer 1c includes a first segment upper electrode 1c11, a second segment upper electrode 1c22, and a third segment upper electrode 1c33 spaced apart from each other. The intermediate electrode layer 2c includes a first segment intermediate electrode 2c11, a second segment intermediate electrode 2c22, and a third segment intermediate electrode 2c33 spaced apart from each other. The lower electrode layer 3c includes a first segment lower electrode 3c11, a second segment lower electrode 3c22 and a third segment lower electrode 3c33 spaced apart from each other.
Wherein, the circuit connection relation of each part is as follows:
the first segment middle electrode 2c11 is a signal input terminal, and the first segment upper electrode 1c11, the first segment lower electrode 3c11 and the second segment middle electrode 2c22 are all electrically connected to ground. The second segment upper electrode 1c22, the second segment lower electrode 3c22 and the third segment middle electrode 2c33 are all electrically connected and in a floating state. The third segment upper electrode 1c33 is electrically connected to the third segment lower electrode 3c33 and serves as the signal output terminal.
In this embodiment, the first segment upper electrode 1c11, the first segment middle electrode 2c11, and the first segment lower electrode 3c11 have overlapping portions in the projection in the thickness direction when disposed on the surfaces of the opposite sides of the piezoelectric layer b. When the second segment upper electrode 1c22, the second segment middle electrode 2c22, and the second segment lower electrode 3c22 are disposed on the surfaces of the opposite sides of the piezoelectric layer b, there is an overlapping portion in the projection in the thickness direction. When the third segment upper electrode 1c33, the third segment middle electrode 2c33 and the third segment lower electrode 3c33 are distributed on the surfaces of the two opposite sides of the piezoelectric layer b, the projections along the thickness direction have overlapping parts, so that an electric field can be generated inside the piezoelectric layer b when an electric signal is applied.
Through the structure and circuit connection relation of the piezoelectric performance test structure 200, the device adopting the multi-stage resonator is directly electrically driven and electrically detected, the operation is convenient, and the piezoelectric performance test structure can be used for the piezoelectric coefficient d31The wafer level test can especially obtain the piezoelectric coefficient d of an ultra-micro film layer structure31. And the whole test system adopts electrical test, and the test system has simple structure and is easy to operate and test. Especially, in the state of device resonance, a larger output voltage can be obtained, which is beneficial to signal detection and reduces power frequency interference, and the piezoelectric performance test structure 200 obtains the piezoelectric coefficient d31The reliability of (2) is higher.
Compared with the prior art, the piezoelectric performance test method and the piezoelectric performance test structure provided by the invention comprise the following steps: step S1, inputting an alternating current signal to a signal input end of the sample to be detected; s2, enabling the sample to be detected to generate deformation through inverse piezoelectric effect through the input alternating current signal, and converting the deformation into an electric signal and outputting the electric signal by the sample to be detected; step S3, acquiring an output electric signal of a signal output end of the sample to be detected, wherein the output electric signal is generated by the piezoelectric film through a positive piezoelectric effect; and step S4, performing signal amplification or signal processing on the output electric signal to obtain the piezoelectric coefficient of the piezoelectric film. The method adopts the coupling of positive piezoelectric effect and inverse piezoelectric effect to realize the evaluation and test of the piezoelectric coefficient of the piezoelectric film, is applied to the direct electric drive and electric detection of the piezoelectric performance test method and the piezoelectric performance test structure of the piezoelectric film, has convenient operation, can be used for the wafer level test of the piezoelectric coefficient, and particularly can obtain the piezoelectric coefficient of an ultra-micro film structure; and the whole test system adopts electrical test, and the test system has simple structure and is easy to operate and test. Particularly, under the resonance state of the device, larger output voltage can be obtained, the detection of signals is facilitated, and the power frequency interference is reduced, so that the reliability of the piezoelectric coefficient obtained by the piezoelectric performance test method and the piezoelectric performance test structure of the film layer piezoelectric material is higher.
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.