Patent Publication Number: US-2015082884-A1

Title: Piezoelectric actuator module, method of manufacturing the same, and mems sensor having the same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2013-0113979, filed on Sep. 25, 2013, entitled “Piezoelectric Actuator Module, Method Of Manufacturing The Same, And MEMS Sensor Having The Same”, which is hereby incorporated by reference in its entirety into this application. 
     BACKGROUND 
     1. Technical Field 
     Embodiments of the present invention generally relate to a piezoelectric actuator module, a method of manufacturing the same, and a micro electro mechanical systems (MEMS) sensor having the same. 
     2. Description of the Related Art 
     Unless otherwise indicated herein, the materials described in this section are not prior art to the claims herein and are not admitted to be prior art by inclusion in this section. 
     MEMS is a technology of manufacturing an ultra micro mechanical structure, such as a very large scale integrated circuit, an inertial sensor, a pressure sensor, and an oscillator, by processing silicon, crystal, glass, or the like. The MEMS component needs precision of a micrometer ( 1/1,000,000 meter) or less and may be mass-produced as a micro product at a low cost by applying a semiconductor micro process technology of repeating processes, such as a deposition process and an etching process. 
     Among the MEMS components, the piezoelectric actuator applies an electric field to a piezoelectric body to be contracted and expanded. Generally, a diaphragm coupled with the piezoelectric body may be deformed by the contraction and expansion of the piezoelectric body. 
     In order to improve displacement or to increase a vibration force, the piezoelectric actuator may be implemented as a multilayered piezoelectric actuator in which a plurality of piezoelectric bodies are stacked. 
     PATENT DOCUMENT 
     (Patent Document 1) U.S. Pat. No. 6,232,701 
     SUMMARY 
     Some embodiments of the present invention may provide a multilayered piezoelectric actuator module, a method of manufacturing a piezoelectric actuator module, and an MEMS sensor having the piezoelectric actuator module. The multilayered piezoelectric actuator module may include a multilayered piezoelectric part polled in the same direction and comprise one piezoelectric body and another piezoelectric body, both being adjacent to each other in the multilayered piezoelectric body, to be expanded and contracted to be opposite to each other. These piezoelectric bodies may serve as a variable diaphragm for each other, for example, but not limited to, to obtain large displacement and improve driving performance. 
     According to a preferred embodiment of the present invention, there is provided a piezoelectric actuator module, including: a multi-layer part including a multilayered piezoelectric part having a plurality of piezoelectric bodies and an electrode part connected to the multilayered piezoelectric part; and a support part displaceably supporting the multi-layer part. The multilayered piezoelectric part may be polled in the same direction, and one of the piezoelectric bodies may be expanded or contracted in an opposite direction to the other piezoelectric body. 
     The multilayered piezoelectric part of the multi-layer part may include a first piezoelectric body, and a second piezoelectric body expanding or contracting in an opposite direction to the first piezoelectric body. The first piezoelectric body may be stacked on the second piezoelectric body. The electrode part may be connected to the first piezoelectric body and the second piezoelectric body. 
     The electrode part of the multi-layer part may include a first electrode connected to the first piezoelectric body, a second electrode connected to the second piezoelectric body, and a third electrode disposed between the first piezoelectric body and the second piezoelectric body. 
     With respect to a stack direction of the multi-layer part, the second electrode may be disposed at a lower end of the multi-layer part with a portion contacting the support part. The second piezoelectric body may be disposed on an upper portion of the second electrode. The third electrode may be disposed between the second piezoelectric body and the first piezoelectric body. The first piezoelectric body may be disposed on an upper portion of the third electrode. The first electrode may be disposed on an upper portion of the first piezoelectric body. 
     A portion of the second electrode which does not contact the support part may be exposed to the outside of the piezoelectric actuator module. 
     An end of the first electrode may be connected to an end of the second electrode. 
     A predetermined first voltage may be applied to the first and second electrodes, and a predetermined second voltage may be applied to the third electrode. The first voltage may be different from the second voltage. 
     An electrode in which the first electrode and the second electrode are connected to each other may be a ground electrode. 
     The multilayered piezoelectric part of the multi-layer part may include an upper piezoelectric part and a lower piezoelectric part. The upper piezoelectric part may include a first upper piezoelectric body and a second upper piezoelectric body. The first upper piezoelectric body may be stacked on the second upper piezoelectric body. The lower piezoelectric part may include a first lower piezoelectric body and a second lower piezoelectric body. The first lower piezoelectric body may be stacked on the second lower piezoelectric body. 
     The electrode part connected to the multilayered piezoelectric part may include a first electrode, a second electrode, a third electrode, a fourth electrode, and a fifth electrode. With respect to the stack direction in which the multi-layer part is coupled with the support part, the first electrode may be disposed on an upper portion of the first upper piezoelectric body, the second electrode may be disposed between the first upper piezoelectric body and the second upper piezoelectric body, the third electrode may be disposed between the second upper piezoelectric body and the first lower piezoelectric body, the fourth electrode may be disposed between the first lower piezoelectric body and the second lower piezoelectric body, and the fifth electrode may be disposed on a lower portion of the second lower piezoelectric body. 
     The second electrode and the fourth electrode may be used as a ground electrode. 
     According to another preferred embodiment of the present invention, there is provided a method of manufacturing the piezoelectric actuator module as described above, including forming a wafer to be formed as a support part supporting the multi-layer part, depositing a lower electrode on one surface of the wafer, depositing a second piezoelectric body on one surface of the lower electrode and depositing an intermediate electrode on one surface of the second piezoelectric body, patterning the intermediate electrode deposited on the second piezoelectric body to have a predetermined pattern, depositing a first piezoelectric body on one surface of the second piezoelectric body and the intermediate electrode, and depositing an upper electrode on one surface of the first piezoelectric body. 
     The method of manufacturing a piezoelectric actuator module may further include patterning the upper electrode and forming a via hole to expose the lower electrode. 
     The method of manufacturing a piezoelectric actuator module may further include patterning a photoresist for depositing input and output electrodes on the upper electrode and the first piezoelectric body. 
     The method of manufacturing a piezoelectric actuator module may further include depositing the input and output electrode by the photoresist for depositing an input and output electrode and removing the photoresist for depositing the input and output electrode. 
     The method of manufacturing a piezoelectric actuator module may further include performing wire bonding to connect a wire for applying an external voltage to the piezoelectric actuator to the input and output electrode. 
     According to another preferred embodiment of the present invention, there is provided an angular velocity sensor, including a flexible substrate including a vibration member and a sensing member, a mass body connected to the flexible substrate, and a post supporting the flexible substrate. The vibration member may include a multi-layer part which includes a multilayered piezoelectric part comprising a plurality of piezoelectric bodies and an electrode part connected to the multilayered piezoelectric part. The multi-layer part may be displaceably supported on the post. The multilayered piezoelectric part may be polled in the same direction throughout such that one of the piezoelectric bodies may be expanded or contracted in an opposite direction to the other piezoelectric body. 
     The multilayered piezoelectric part of the multi-layer part may include a first piezoelectric body and a second piezoelectric body. The first piezoelectric body may be stacked on the second piezoelectric body. The second piezoelectric body may be expanded or contracted in an opposite direction to the first piezoelectric body. 
     The electrode part may be connected to a first piezoelectric body and a second piezoelectric body. The electrode part of the multi-layer part may include a first electrode connected to the first piezoelectric body, a second electrode connected to the second piezoelectric body, and a third electrode disposed between the first piezoelectric body and the second piezoelectric body. 
     A portion of the second electrode which does not contact a post may be exposed to the outside of the angular velocity sensor. 
     An end of the first electrode may be connected to an end of the second electrode. A predetermined first voltage may be applied to the first and second electrodes, and a predetermined second voltage may be applied to the third electrode. The first voltage may be different from the second voltage. 
     In some embodiments, a piezoelectric actuator may comprise multi-layer piezoelectric bodies, one or more electrode parts connected to the multilayer piezoelectric bodies, and a support part coupled to the multi-layer piezoelectric bodies. One of the multilayer piezoelectric bodies may expand or contract in an opposite direction to another of the multilayer piezoelectric bodies. 
     The one of the multilayer piezoelectric bodies may be disposed on the another of the multilayer piezoelectric bodies. 
     The multi-layer piezoelectric bodies may further comprise at least one of the multi-layer piezoelectric bodies expanding or contracting in the same direction as the one of the multilayer piezoelectric bodies, and at least one of the multi-layer piezoelectric bodies expanding or contracting in the same direction as the another of the multilayer piezoelectric bodies. 
     The electrode parts may be disposed between the multi-layer piezoelectric bodies or at the uppermost or lowermost ends of the multi-layer piezoelectric bodies. 
     The multi-layer piezoelectric bodies may be configured to be polled in the same direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIGS. 1A and 1B  are diagrams schematically illustrating exemplary embodiments of a piezoelectric actuator, in which  FIG. 1A  is a diagrammatic view of the piezoelectric actuator module according to one embodiment of the present invention, and  FIG. 1B  is a diagrammatic view of a piezoelectric actuator module according to another embodiment; 
         FIG. 2  is a schematic illustration of a piezoelectric actuator module according to a first preferred embodiment of the present invention; 
         FIGS. 3A and 3B  are diagrammatic views schematically illustrating driving of the piezoelectric actuator module illustrated in  FIG. 2 ; 
         FIGS. 4A to 4K  are cross-sectional views schematically illustrating a method of manufacturing a piezoelectric actuator module illustrated in  FIG. 2  according to the preferred embodiment of the present invention; 
         FIG. 5  is a schematic illustration of a piezoelectric actuator module according to a second preferred embodiment of the present invention; 
         FIGS. 6A and 6B  are diagrammatic views schematically illustrating driving of the piezoelectric actuator module illustrated in  FIG. 5 ; and 
         FIG. 7  is a cross-sectional view schematically illustrating an angular velocity sensor including the piezoelectric actuator module according to the preferred embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be more clearly understood from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant descriptions thereof are omitted. Further, in the following description, the terms “first”, “second”, “one side”, “the other side” and the like are used to differentiate a certain component from other components, but the configuration of such components should not be construed to be limited by the terms. As used in this description and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Further, in the description of embodiments of the present invention, when the detailed description of the related art would obscure the gist of the present invention, the description thereof is omitted. 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. 
       FIGS. 1A and 1B  are diagrams schematically illustrating exemplary embodiments of a piezoelectric actuator according to a preferred embodiment of the present invention.  FIG. 1A  is a configuration diagram and a usage diagram of one embodiment of the present invention, and  FIG. 1B  is a configuration diagram and a usage diagram of another embodiment of the present application. 
     In the embodiment illustrated in  FIG. 1B , A piezoelectric actuator  2  may include a piezoelectric body  2   a  and a diaphragm  2   b . The piezoelectric body  2   a  may be fixedly coupled with the diaphragm  2   b . When the piezoelectric body  2   a  is expanded by having a voltage applied, the diaphragm  2   b  supports the piezoelectric body  2   a  by a protruding displacement as illustrated by D 2  in  FIG. 1B , and when the piezoelectric body  2   a  is contracted, the diaphragm  2   b  interacts with the contraction of the piezoelectric body  2   a  such that the protruding displacement occurs as illustrated by D 2  in  FIG. 1B . 
     However, as illustrated in  FIG. 1A , a piezoelectric actuator  1  according to the one embodiment of the present invention may include a first piezoelectric body  1   a  and a second piezoelectric body  1   b  without the diaphragm  2   b  shown in  FIG. 1B . 
     The first piezoelectric body  1   a  and the second piezoelectric body  1   b  are polled in the same direction. When being applied with a voltage, the first piezoelectric body  1   a  and the second piezoelectric body  1   b  may be expanded and contracted in a direction opposite to each other. For example, when the first piezoelectric body  1   a  is expanded, the second piezoelectric body  1   b  is contracted, and when the first piezoelectric body  1   a  is contracted, the second piezoelectric body  1   b  is expanded. 
     Therefore, the first piezoelectric body  1   a  and the second piezoelectric body  1   b  may serve as a vibration support plate for each other and serve as an active diaphragm which varies in an opposite direction. 
     When the first piezoelectric body  1   a  is expanded, contraction of the second piezoelectric body  1   b  may make the first piezoelectric body  1   a  more expand, such that a protruding displacement occurs as illustrated by D 1  in  FIG. 1A . When the second piezoelectric body  1   b  is expanded, contraction of the first piezoelectric body  1   a  makes the second piezoelectric body  1   b  further expand, such that a protruding displacement occurs as illustrated by D 1  in  FIG. 1A . 
     Consequently, in the piezoelectric actuator according to the one embodiment of the present invention, a plurality of piezoelectric bodies may serve as vibration support plates to each other. Each of the plurality of piezoelectric bodies may serve as the active diaphragm which varies in an opposite direction to the other piezoelectric body, such that the displacement (confirmed by comparison of D 1  and D 2 ) may occur largely over the driving by the simple support plate, thereby improving the vibration force. 
     Hereinafter, the piezoelectric actuator module according to embodiments of the present invention will be described in detail. 
       FIG. 2  is a configuration diagram schematically illustrating a piezoelectric actuator module according to a first preferred embodiment of the present invention. As illustrated in  FIG. 2 , the piezoelectric actuator module  100  may include a multi-layer part  110  and a support part  120 . 
     When an electric field is applied to the multi-layer part  110  from the outside of the piezoelectric actuator module  100 , the multi-layer part  110  contracts and expands to generate a vibration force. The multi-layer part  110  may include a multilayered piezoelectric part  111  and an electrode part  112 . The support part  120  may support the multi-layer part  110  to facilitate displacement. 
     The multilayered piezoelectric part  111  is polled in the same direction. One of the piezoelectric bodies of the multilayered piezoelectric part  111  contacting each other is expanded or contracted in an opposite direction to the other piezoelectric body of the multilayered piezoelectric part  111 . 
     For example, the multilayered piezoelectric part  111  may include a first piezoelectric body  111   a  and a second piezoelectric body  111   b . The first piezoelectric body  111   a  may be stacked on the second piezoelectric body  111   b.    
     The first piezoelectric body  111   a  and the second piezoelectric body  111   b  are polled in the same direction as illustrated in  FIG. 2 , and are expanded or contracted in an opposite direction to each other. 
     The first piezoelectric body  111   a  and the second piezoelectric body  111   b  are not coupled with a support plate, but the ends of the first piezoelectric body  111   a  and the second piezoelectric body  111   b  are supported to the support part  120 . Accordingly, the first piezoelectric body  111   a  and the second piezoelectric body  111   b  can be expanded or contracted in an opposite direction to each other without having a separate support plate or diaphragm. 
     The first piezoelectric body  111   a  and the second piezoelectric body  111   b  may serve as the vibration support plate for each other and serve as the active diaphragm which varies in an opposite direction. 
     Exemplary embodiments will be described in  FIGS. 3A and 3B . 
     The electrode part  112  may include a first electrode  112   a , a second electrode  112   b , and a third electrode  112   c  which are connected to the multilayered piezoelectric part  111 . 
     For instance, the first electrode  112   a  is connected to the first piezoelectric body  111   a , the second electrode  112   b  is connected to the second piezoelectric body  111   b , and the third electrode  112   c  is disposed between the first piezoelectric body  111   a  and the second piezoelectric body  111   b.    
     The first electrode  112   a  and the second electrode  112   b  which are connected to each other may be used as a ground electrode. 
     With respect to a stack direction of the multi-layer part  110  coupled with the support part  120 , the second electrode  112   b  may be disposed at a lower end of the multi-layer part  110  and a portion coupled with the support part  120 , the second piezoelectric body  111   b  may be disposed on an upper portion of the second electrode  112   b , the third electrode  112   c  may be disposed between the second piezoelectric body  111   b  and the first piezoelectric body  111   a , the first piezoelectric body  111   a  may be disposed on an upper portion of the third electrode  112   c , and the first electrode  112   a  may be disposed on an upper portion of the first piezoelectric body  111   a.    
     In the multi-layer part  110 , the first electrode  112   a  may be formed as an upper electrode, the second electrode  112   b  may be formed as a lower electrode, and the third electrode  112   c  may be formed as an intermediate electrode. The first electrode  112   a  may be disposed at the uppermost layer of the multi-layer part  110 , and the second electrode  112   b  is disposed at the lowermost layer of the multi-layer part  110 . 
     The support part  120  may be coupled with one or both ends of the multi-layer part  110  to support the multi-layer part  110  for displacement. Therefore, a portion of the second electrode  112   b  which does not contact the support part  120  may be exposed to the outside of the piezoelectric actuator module  100 . 
     Hereinafter, a driving principle and an operation state of the piezoelectric actuator module according to the first preferred embodiment of the present invention illustrated in  FIG. 2  will be described in more detail with reference to  FIGS. 3A and 3B . 
       FIGS. 3A and 3B  schematically illustrate the driving of the piezoelectric actuator module  100  illustrated in  FIG. 2 . As illustrated in  FIG. 3A , an electric field is applied to the electrode connected to the first electrode  112   a  and the second electrode  112   b  of the multi-layer part  110  of the piezoelectric actuator module  100 , which are connected to each other, and the third electrode  112   c , respectively. For example, when as represented in  FIG. 3A  by + and −, a negative voltage is applied to the first electrode  112   a  and the second electrode  112   b  which are connected to each other and a positive voltage is applied to the third electrode  112   c , the first piezoelectric body  111   a  is expanded and at the same time, the second piezoelectric body  111   b  is contracted as represented by an arrow. 
     Therefore, a central portion of the multi-layer part  110  is displaced upwardly as represented in  FIG. 3A  by an arrow, ends of the multi-layer part  110  being supported by the support parts  120 . 
     Next, as illustrated in  FIG. 3B , an electric field opposite to that of  FIG. 3A  is applied to the electrode in which the first electrode  111   a  and the second electrode  112   b  of the multi-layer part  110  of the piezoelectric actuator module  100  are connected to each other and the third electrode  112   c , respectively. For instance, when a positive voltage is applied to the electrode in which the first electrode  112   a  and the second electrode  112   b  are connected to each other and a negative voltage is applied to the third electrode  112   c , as represented in  FIG. 3B  by an arrow, the first piezoelectric body  111   a  is contracted and at the same time, the second piezoelectric body  111   b  is expanded. 
     Therefore, the central portion of the multi-layer part  110  is displaced downwardly as represented in  FIG. 3B  by an arrow, The ends of the multi-layer part  110  are supported by the support parts  120 . 
     By the above configuration, the first piezoelectric body  111   a  and the second piezoelectric body  111   b  are contracted and expanded opposite to each other, such that a large displacement may occur, thereby which may improve the driving performance. 
       FIGS. 4A to 4K  are cross-sectional views schematically illustrating a method for manufacturing a piezoelectric actuator module according to a preferred embodiment of the present invention to which he first preferred embodiment of a piezoelectric actuator module illustrated in  FIG. 2  may be applied. 
       FIG. 4A  illustrates an exemplary embodiment of forming a wafer. As illustrated in  FIG. 4A , the wafer  10  is prepared. Further, an outer circumferential surface of the wafer  10  may be provided with an oxide layer (not illustrated). 
     Next,  FIG. 4B  illustrates an exemplary embodiment of depositing the lower electrode. For example, as illustrated in  FIG. 4B , a lower electrode  21  is deposited on one surface of the wafer  10 . 
     Next,  FIG. 4C  illustrates an exemplary embodiment of depositing the second piezoelectric body and the intermediate electrode. For instance, as illustrated in  FIG. 4C , a second piezoelectric body  22  is deposited on one surface of the lower electrode  21  which is deposited on the wafer  10 . An intermediate electrode  23  is deposited on one surface of the second piezoelectric body  22 . With respect to the stack direction, the second piezoelectric body  22  is deposited on an upper portion of the lower electrode  21  which is deposited on the wafer  10 , and the intermediate electrode  23  is deposited on the upper portion of the second piezoelectric body  22 , or vice versa. 
     Next,  FIG. 4D  illustrates an exemplary embodiment of patterning the intermediate electrode. As illustrated in  FIG. 4D , the intermediate electrode  23  may be deposited on the upper portion of the second piezoelectric body  22  and patterned to have a predetermined pattern shape. 
     Next,  FIG. 4E  illustrates an exemplary embodiment of depositing the first piezoelectric body. As illustrated in  FIG. 4E , a first piezoelectric body  24  may be deposited on upper portions of the second piezoelectric body  22  and the intermediate electrode  23 . 
     Next,  FIG. 4F  illustrates an exemplary embodiment of depositing an upper electrode. As illustrated in  FIG. 4F , an upper electrode  25  is deposited on the upper portion of the first piezoelectric body  24 . 
     Next,  FIG. 4G  illustrates an exemplary embodiment of patterning the upper electrode and forming a via hole. As illustrated in  FIG. 4G , the upper electrode  25  illustrated in  FIG. 4F  is patterned to have a predetermined pattern shape, and a via V is formed by using, for example, but not limited to, a method for etching the upper electrode  25 , the first piezoelectric body  24 , and the second piezoelectric body  22 , and the like to expose the lower electrode  21 . 
     Next,  FIG. 4H  illustrates an exemplary embodiment of patterning a photoresist for depositing input and output electrodes. In  FIG. 4H , a photoresist  26  for depositing input and output electrodes is patterned on the upper electrode  25  and the first piezoelectric body  24  illustrated in  FIG. 3G . 
     Next,  FIG. 4I  illustrates an exemplary embodiment of depositing input and output electrodes and removing the photoresist. In  FIG. 4I , the input and output electrodes  27  are deposited by the photoresist  26  for depositing input and output electrodes illustrated in  FIG. 4H , and then the photoresist  26  for creating input and output electrodes is removed. The input and output electrodes  27  may be made of AU. 
     Next,  FIG. 4J  illustrates an exemplary embodiment of forming the support part. As illustrated in  FIG. 4J , the support part  11  is formed by etching the wafer  10 . A portion of the lower electrode  21  may be exposed to the outside of the piezoelectric actuator by the support part  11 . 
     Next,  FIG. 4K  illustrates an exemplary embodiment of performing wire bonding. The step of performing of wire bonding is to electrically connect a piezoelectric actuator to an external device by coupling a wire  30  to the input and output electrodes  27 . 
     A voltage is applied to the first piezoelectric body  24  and the second piezoelectric body  22  so as to be polled in the same direction, thereby obtaining the piezoelectric actuator module according to the preferred embodiment of the present invention. 
     As the piezoelectric actuator module is configured without including a separate diaphragm coupled with the lower electrode  21  or the upper electrode  25 , when an electric field is applied through the wire  30  from the outside of the piezoelectric actuator module  100 , the piezoelectric actuator module  100  can be displaced upwardly or downwardly as illustrated in  FIGS. 3A and 3B . 
       FIG. 5  is a configuration diagram schematically illustrating a piezoelectric actuator module according to a second preferred embodiment of the present invention. As illustrated in the first preferred embodiment shown in  FIG. 2 , the piezoelectric actuator module  100  has a two-layered piezoelectric part. However, in the second preferred embodiment shown in  FIG. 5  a piezoelectric actuator module  200  has a four-layered piezoelectric part. 
     The piezoelectric actuator module  200  may include a multi-layer part  210  and a support part  220 . 
     The multi-layer part  210  may include a multilayered piezoelectric part  211  and an electrode part  212 . The support part  220  displaceably supports the multi-layer part  210 . 
     The multilayered piezoelectric part  211  may include an upper piezoelectric part  211   a  and a lower piezoelectric part  211   b , and be polled in the same direction so as to allow the upper piezoelectric part  211   a  and the lower piezoelectric part  211   b  to be expanded or contracted in an opposite direction to each other. 
     The upper piezoelectric part  211   a  may include a first upper piezoelectric body  211   a ′ and a second upper piezoelectric body  211   a ″. The first upper piezoelectric body  211   a ′ may be stacked on the second upper piezoelectric body  211   a″.    
     The lower piezoelectric part  211   b  may include a first lower piezoelectric body  211   b ′ and a second lower piezoelectric body  211   b ″. The first lower piezoelectric body  211   b ′ may be stacked on the second lower piezoelectric body  211   b″   
     The upper piezoelectric part  211   a  may be stacked on the lower piezoelectric part  211   b , and the upper and lower piezoelectric parts  211   a  and  211   b  are polled in the same direction as represented by an arrow in  FIG. 5 . 
     The electrode parts  212  may be each connected to the multilayered piezoelectric parts  211  or may include a first electrode  212   a , a second electrode  212   b , a third electrode  212   c , a fourth electrode  212   d , and a fifth electrode  212   e  which are implemented as ground electrodes. 
     For example, with respect to a stack direction of the multi-layer part  210  which is coupled with the support part  220 , the first electrode  212   a  is disposed on an upper portion of the first upper piezoelectric body  211   a ′, the second electrode  212   b  is disposed between the first upper piezoelectric body  211   a ′ and the second upper piezoelectric body  211   a ″, the third electrode  212   c  is disposed between the second upper piezoelectric body  211   a ″ and the first lower piezoelectric body  211   b ′, the fourth electrode  212   d  is disposed between the first lower piezoelectric body  211   b ′ and the second lower piezoelectric body  211   b ″, and the fifth electrode  212   e  is disposed on a lower portion of the second lower piezoelectric body  211   b ″, that is, a lower end of the multi-layer part  210 . 
     The second electrode  212   b  and/or the fourth electrode  212   d  may be used as the ground electrode. 
     The support part  220  may be coupled with one or both ends of the multi-layer part  210  to displaceably support the multi-layer part  210 . Therefore, a portion of the fifth electrode  212   e  which does not contact the support part is exposed to the outside of the piezoelectric actuator module  200 . 
     In another embodiment of the multilayered piezoelectric part, the upper piezoelectric body may consist of a first upper piezoelectric body, a second upper piezoelectric body, and a third upper piezoelectric body, and the lower piezoelectric body may consist of a first lower piezoelectric body. 
     In another embodiment of the multilayered piezoelectric part, the upper piezoelectric body may consist of the first upper piezoelectric body and the lower piezoelectric body may consist of a first lower piezoelectric body, a second lower piezoelectric body, and a third lower piezoelectric body. 
     Hereinafter, the driving principle and the operation of the piezoelectric actuator module according to the second preferred embodiment of the present invention illustrated in  FIG. 5  will be described in more detail with reference to  FIGS. 6A and 6B . 
       FIGS. 6A and 6B  are diagrams schematically illustrating the driving of the piezoelectric actuator module illustrated in  FIG. 5 . 
     As illustrated in  FIG. 6A , in the piezoelectric actuator module  200 , when an electric field is applied to the electrode parts  212  of the multi-layer part  210 , respectively, the multilayered piezoelectric part  211  is expanded or contracted. 
     For example, as represented by + and −, when a negative voltage is applied to the first electrode  212   a  and the fifth electrode  212   e , respectively, and a positive voltage is applied to the third electrode  212   c , as represented by an arrow, the first upper piezoelectric body  211   a ′ and the second upper piezoelectric body  211   a ″ which are the upper piezoelectric body  211   a  are expanded, and at the same time, the first lower piezoelectric body  211   b ′ and the second lower piezoelectric body  211   b ″ which are the lower piezoelectric part  211   b  are contracted. Therefore, a central portion of the multi-layer part  210  is displaced upwardly as represented in  FIG. 6A  by an arrow in the state in which an end of the multi-layer part  210  is supported to the support part  220 . 
       FIG. 6B  shows an example when an electric field opposite to that illustrated in  FIG. 6A  is applied to the electrode parts  212  of the multi-layer part  210  of the piezoelectric actuator module  200 . In  FIG. 6B , when a positive voltage is applied to the first electrode  212   a  and the fifth electrode  212   e , respectively, and a negative voltage is applied to the third electrode  212   c , as represented by an arrow, the first upper piezoelectric body  211   a ′ and the second upper piezoelectric body  211   a ″ which are the upper piezoelectric body  211   a  are contracted, and the first lower piezoelectric body  211   b ′ and the second lower piezoelectric body  211   b ″ which are the lower piezoelectric part  211   b  are expanded. Therefore, the central portion of the multi-layer part  210  is displaced down as represented in  FIG. 6B  by an arrow in the state in which the end of the multi-layer part  210  is displaceably supported by the support part  220 . 
     By the above configuration, the upper piezoelectric part  211   a  and the lower piezoelectric part  211   b  are contracted and expanded opposite of each other to cause a large overall displacement. The upper piezoelectric part  211   a  and the lower piezoelectric part  211   b  are each configured of multilayers to obtain a larger force than in the occurrence of displacement with less layers. 
     In the piezoelectric actuator module  200  according to the second preferred embodiment of the present invention, the electrode parts may be variously implemented as another pattern to which the concept of the present invention is applied. 
       FIG. 7  is a cross-sectional view schematically illustrating an angular velocity sensor including a piezoelectric actuator module according to the preferred embodiment of the present invention. The angular velocity sensor  1000  may include a flexible substrate part  1100 , a mass body  1200 , and a post  1300 . 
     The mass body  1200  may be displaced by an inertial force, a Coriolis force, an external force, a driving force, and the like. The mass body  1200  is coupled with the flexible substrate part  1100 . 
     The flexible substrate part  1100  is provided with a sensing member  1110  and a vibration member  1120 . As the flexible substrate part  1100  is coupled with the post  1300 , the mass body  1200  is displaceably supported by the post  1300  by the flexible substrate part  1100 . 
     The vibration member  1120  of the flexible substrate part  1100  may be configured as the piezoelectric actuator module  100  illustrated in  FIG. 2 . The vibration member  1120  may include a multi-layer part  1121 . 
     The sensing member  1110  may be formed in, for example, a piezoelectric type, a piezoresistive type, a capacitive type, an optical scheme, and the like, but is not particularly limited thereto. 
     When an electric field is applied to the multi-layer part  1121 , the multi-layer part  1121  is contracted and expanded to generate a vibration force. The multi-layer part  1121  may include a multilayered piezoelectric part  1121   a  and an electrode part  1121   b . The post  1300  displaceably supports the multi-layer part  1121 . 
     The multilayered piezoelectric part  1121   a  is polled in the same direction such that one of the piezoelectric bodies of the multilayered piezoelectric part  1121   a  contacting each other expands or contracts in opposite directions each other. 
     The multilayered piezoelectric part  1121   a  may include a first piezoelectric body  1121   a ′ and a second piezoelectric body  1121   a ″. The first piezoelectric body  1121   a ′ may be stacked on the second piezoelectric body  1121   a″.    
     The first piezoelectric body  1121   a ′ and the second piezoelectric body  1121   a ″ may be polled in the same direction to expand or contract in opposite to each other. 
     The first piezoelectric body  1121   a ′ and the second piezoelectric body  1121   a ″ are not coupled with a separate support plate, but the ends of the first piezoelectric body  1121   a ′ and the second piezoelectric body  1121   a ″ are supported by the post  1300 , and the first piezoelectric body  1121   a ′ and the second piezoelectric body  1121   a ″ are expanded or contracted in an opposite to each other. 
     The electrode part  1121   b  may include a first electrode  1121   b ′, a second electrode  1121   b ″, and a third electrode  1121   b ′″ which are each connected to the multilayered piezoelectric part  1121   a.    
     For example, the first electrode  1121   b ′ is connected to the first piezoelectric body  1121   a ′, the second electrode  1121   b ″ is connected to the second piezoelectric body  1121   a ″, and the third electrode  1121   b ′″ is disposed between the first piezoelectric body  1121   a ′ and the second piezoelectric body  1121   a″.    
     The first electrode  1121   b ′ and the second electrode  1121   b ″ may have ends connected to each other and may be used as a ground electrode. 
     With respect to the stack direction of the multi-layer part  1121  which is coupled with the post  1300 , the second electrode  1121   b ″ may be disposed at a lower end of the multi-layer part  1121  and a portion contacting the post  1300 , the second piezoelectric body  1121   a ″ may be disposed on an upper portion of the second electrode  1121   b ″, the third electrode  1121   b ′″ may be disposed between the second piezoelectric body  1121   a ″ and the first piezoelectric body  1121   a ′, the first piezoelectric body  1121   a ′ may be disposed on an upper portion of the third electrode  1121   b ′″, and the first electrode  1121   b ′ may be disposed on an upper portion of the first piezoelectric body  1121   a′.    
     For example, in the multi-layer part  1121 , the first electrode  1121   b ′ is formed as an upper electrode, the second electrode  1121   b ″ is formed as a lower electrode, and the third electrode  1121   b ′″ is formed as an intermediate electrode. The first electrode  1121   b ′ is disposed at the uppermost layer of the multi-layer part  1121 , and the second electrode  1121   b ″ is disposed at the lowermost layer of the multi-layer part  1121 . 
     The angular velocity sensor including the piezoelectric actuator module according to the preferred embodiment of the present invention may vibrate the vibration member  1120  to sense an angular velocity. The vibration member  120  may be vibrated at high efficiency by the piezoelectric part  1121   a  of a double layer, such that the angular velocity sensor may be implemented to more accurately perform the sensing. 
     According to the preferred embodiments of the present invention, it is possible to obtain the multilayered piezoelectric actuator module, the method of manufacturing a piezoelectric actuator module, and the MEMS sensor having the piezoelectric actuator module, in which as the multilayered piezoelectric actuator module includes the multilayered piezoelectric part polled in the same direction and have one piezoelectric body and the other piezoelectric body, which are adjacent to each other in the multilayered piezoelectric body, to expand and contract in opposite to each other. These piezoelectric bodies may serve as a variable diaphragm for each other, thereby obtaining a large displacement and improving the driving performance. 
     Although the embodiments of the present invention have been disclosed for illustrative purposes, it will be appreciated that the present invention is not limited thereto, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention. 
     Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the invention, and the detailed scope of the invention will be disclosed by the accompanying claims. Additionally, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed.