Patent Publication Number: US-10785577-B2

Title: MEMS microphone and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Korean Patent Application No. 10-2018-0068679, filed on Jun. 15, 2018, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which are incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to a Micro Electro Mechanical Systems (MEMS) microphone capable of converting an acoustic wave into an electrical signal and a method of manufacturing the same. More particularly, the present disclosure relates to a capacitive MEMS microphone being capable of transforming the acoustic wave into the electric signal using a displacement of a diaphragm which occurs due to an acoustic pressure, and a method of manufacturing such a MEMS microphone. 
     BACKGROUND 
     Generally, a capacitive microphone utilizes a capacitance measured between a pair of electrodes which are facing each other to detect an acoustic wave to output an electrical signal. The capacitive microphone may be manufactured through semiconductor MEMS processes to achieve a MEMS microphone having an ultra-small size. 
     The capacitive microphone includes a diaphragm being configured to be bendable and a back plate facing the diaphragm such that an air gap is defined between the diaphragm and the back plate. The diaphragm may have a membrane structure to perceive an acoustic pressure to generate a displacement. In particular, when the acoustic pressure is applied to the diaphragm, the diaphragm may be bent toward the back plate due to the acoustic pressure. The displacement of the diaphragm may be perceived through a value change of capacitance defined between the diaphragm and the back plate. As a result, an acoustic wave may be converted into an electrical signal such that the electrical signal may be outputted. 
     The MEMS microphone has various characteristics such as a frequency resonance, a pull-in voltage, a Total Harmonic Distortion (hereinafter, referred as “THD”), a sensitivity, etc. 
     In particular, when the MEMS microphone is applied to a high-end mobile device, it may be required for the MEMS microphone to have improved acoustic resistance. In order to improve the acoustic resistance, it may be required to increase the acoustic resistance of air when discharged from the air gap. 
     SUMMARY 
     The example embodiments of the present invention provide a MEMS microphone capable of having an improved acoustic resistance. 
     The example embodiments of the present invention provide a method of manufacturing a MEMS microphone capable of having an improved acoustic resistance. 
     According to some example embodiments of the present invention, a MEMS microphone includes a substrate having a cavity, a back plate disposed over the substrate and having a plurality of acoustic holes, a diaphragm disposed between the substrate and the back plate, the diaphragm being spaced apart from the substrate, being apart form the back plate to form an air gap between the diaphragm and the back plate, and covering the cavity, the diaphragm being configured to sense an acoustic pressure to generate a displacement, a first supporting member surrounding the diaphragm, the first supporting member including first dam portions arranged along a circumference of the diaphragm, and first slit portions between the first dam portion adjacent to each other to be configured to support the diaphragm from a lower face of the substrate, and a second supporting member surrounding the first supporting member, the second supporting member including second dam portions arranged along a circumference of the first dam portions, and second slit portions between the second dam portion adjacent to each other to be configured to further support the diaphragm from the lower face of the substrate. 
     In an example embodiment, the first and the second supporting members may be concentrically arranged. 
     In an example embodiment, the first and the second slit portions may be alternatively arranged in a plan view. 
     In an example embodiment, each of the first slit portions has a length smaller than that of each of the first portions. 
     In an example embodiment, each of the second slit portions has a length smaller than that of each of second dam portions. 
     In an example embodiment, each of the first dam portions has an arc shape in a plane view. 
     In an example embodiment, each of the second dam portions has an arc shape in a plane view. 
     In an example embodiment, each of the first dam portions has a “U” sectional shape. 
     In an example embodiment, each of the second dam portions has a “U” sectional shape. 
     In an example embodiment, the first and the second supporting members may be integrally formed with the diaphragm. 
     In an example embodiment, the MEMS microphone may further comprises an upper insulation layer disposed over the diaphragm and spaced apart from the diaphragm, the upper insulation layer being configured to hold the back plate, and a chamber portion positioned outside from the second supporting member, the chamber portion being connected to the upper insulation layer and making contact with the lower face of the substrate to support the upper insulation layer. 
     According to some example embodiments of the present invention, a lower insulation layer is formed on a substrate defining a vibration area, a supporting area surrounding the vibration area, and a peripheral area surrounding the supporting area, a diaphragm and first and second dam portions of supporting the diaphragm are formed on the lower insulation layer, a sacrificial layer is formed on the lower insulation layer to cover the diaphragm, a back plate is formed on the sacrificial layer and in the vibration area to face the diaphragm, the back plate is patterned to form a plurality of acoustic holes penetrating through the back plate, the substrate is patterned to form a cavity to partially expose the lower insulation layer in the vibration region, and an etch process is performed using the cavity and the acoustic holes to remove portions of the lower insulation layer and the sacrificial layer in the vibration area and the supporting area, wherein performing the etch process using the cavity and the acoustic holes includes forming first slit portions between the first dam portions adjacent to each other to form a first supporting member including the first dam portions and the first slit portions and forming the second slit portions between the second dam portions adjacent to each other to form a second supporting member including the second dam portions and the second slit portions. 
     In an example embodiment, forming the diaphragm and the first and second dam portions may include patterning the lower insulation layer to form a plurality of first dam holes spaced apart from each other and a plurality of second dam holes surrounding the first dam holes and being spaced from each other for forming the first and second dam portions, forming a silicon layer on the lower insulation layer to cover the first and second dam holes, and patterning the silicon layer to form the diaphragm and the first and second dam portions. 
     In an example embodiment, prior to forming the acoustic holes, the sacrificial layer and the lower insulation layer may be patterned to form a chamber hole in the supporting area, an insulation layer for holding the back plate may be formed on the sacrificial layer to cover the back plate and the chamber hole, and the insulation layer may be formed to form the upper insulation layer for holding the back plate, and a chamber portion in the chamber hole, wherein forming the acoustic holes may include patterning the back plate and the upper insulation layer to form the acoustic holes penetrating through the back plate and the upper insulation layer in the vibration region. 
     In an example embodiment, wherein the first and the second supporting members may be concentrically arranged. 
     In an example embodiment, the first and the second slit portions may be alternatively arranged in a plan view. 
     In an example embodiment, each of the first slit portions may have a length smaller than that of each of the first portions. 
     In an example embodiment, each of the second slit portions may have a length smaller than that of each of second dam portions. 
     According to example embodiments of the present invention as described above, the MEMS microphone includes the first supporting member and the second supporting member extending along the circumference of the diaphragm. Further the areas of the first slit portions and the second slit portions included in the first and second support members may be adjusted. In particular, since the first and second slit portions serve as a pathway through which the acoustic pressure flows, the MEMS microphone may reduce the area of the effective pathway where the acoustic pressure flows. As a result, the MEMS microphone may have increased acoustic resistance. Therefore, the MEMS microphone has a low pass filter effect to weaken the noise component at high frequencies. As a result, the MEMS microphone may have improved SNR characteristics. 
     The above summary is not intended to describe each illustrated embodiment or every implementation of the subject matter hereof. The figures and the detailed description that follow more particularly exemplify various embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments can be understood in more detail from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a plan view illustrating a MEMS microphone in accordance with an embodiment of the present invention; 
         FIG. 2  is a cross sectional view taken along a line I-I′ in  FIG. 1 ; 
         FIG. 3  is a plan view illustrating the substrate in  FIG. 1 ; 
         FIG. 4  is a cross sectional view taken along a line II-II′ in  FIG. 1 ; 
         FIG. 5  is a flow chart illustrating a method of manufacturing a MEMS microphone in accordance with an embodiment of the present invention; 
         FIG. 6  is a plan view illustrating the lower insulation layer having the first and the second dam holes; and 
         FIGS. 7 to 17  are cross sectional views illustrating a method of manufacturing a MEMS microphone in accordance with an embodiment of the present invention. 
     
    
    
     While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Hereinafter, specific embodiments will be described in more detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. 
     As an explicit definition used in this application, when a layer, a film, a region or a plate is referred to as being ‘on’ another one, it can be directly on the other one, or one or more intervening layers, films, regions or plates may also be present. Unlike this, it will also be understood that when a layer, a film, a region or a plate is referred to as being ‘directly on’ another one, it is directly on the other one, and one or more intervening layers, films, regions or plates do not exist. Also, though terms like a first, a second, and a third are used to describe various components, compositions, regions and layers in various embodiments of the present invention are not limited to these terms. 
     Furthermore, and solely for convenience of description, elements may be referred to as “above” or “below” one another. It will be understood that such description refers to the orientation shown in the Figure being described, and that in various uses and alternative embodiments these elements could be rotated or transposed in alternative arrangements and configurations. 
     In the following description, the technical terms are used only for explaining specific embodiments while not limiting the scope of the present invention. Unless otherwise defined herein, all the terms used herein, which include technical or scientific terms, may have the same meaning that is generally understood by those skilled in the art. 
     The depicted embodiments are described with reference to schematic diagrams of some embodiments of the present invention. Accordingly, changes in the shapes of the diagrams, for example, changes in manufacturing techniques and/or allowable errors, are sufficiently expected. Accordingly, embodiments of the present invention are not described as being limited to specific shapes of areas described with diagrams and include deviations in the shapes and also the areas described with drawings are entirely schematic and their shapes do not represent accurate shapes and also do not limit the scope of the present invention. 
       FIG. 1  is a plan view illustrating a MEMS microphone in accordance with an embodiment of the present invention.  FIG. 2  is a cross sectional view taken along a line I-I′ in  FIG. 1 .  FIG. 3  is a plan view illustrating the substrate in  FIG. 1 .  FIG. 4  is a cross sectional view taken along a line II-II′ in  FIG. 1 . 
     Referring to  FIGS. 1 to 4 , a MEMS microphone  101  in accordance with an example embodiment of the present invention includes a substrate  110 , a diaphragm  120 , a back plate  140 , a first supporting member  130  and a second supporting member  135 . 
     As shown in  FIG. 3 , the substrate  110  is divided into a vibration area VA, a supporting area SA surrounding the vibration area VA, and a peripheral area PA surrounding the supporting area SA. In the vibration area VA, a cavity  112  is formed. The cavity  112  may penetrate through the substrate  110  in a vertical direction. 
     The cavity  112  may provide a space in order for the diaphragm  120  to be downwardly bendable (i.e., bendable into the cavity  112 ) when an acoustic pressure is applied. Further, the cavity  112  may serve as a moving path of the applied acoustic pressure wave. 
     In an example embodiment, the cavity  112  may have a cylindrical column shape. The cavity  112  may have a planar size corresponding to that of the vibration area VA. 
     The diaphragm  120  may be positioned over the substrate  110 . The diaphragm  120  may have a membrane structure. The diaphragm  120  detects the acoustic pressure to generate a displacement. 
     The diaphragm  120  is disposed to cover the cavity  112 . Further, the diaphragm  120  is positioned to correspond to the vibration area VA. The diaphragm  120  may have a lower face exposed through the cavity  112 . The diaphragm  120  is spaced apart from the substrate  110  to be configured to be downwardly bendable with responding to the acoustic pressure. 
     As shown in  FIG. 2 , the diaphragm  120  may have an ion implantation region into which impurities such III element or V elements are doped. The ion implantation region may face the back plate  140 . 
     In an example embodiment, the diaphragm  120  may have a shape of a disc plate, as shown in  FIG. 1 . 
     The back plate  140  may be disposed over the diaphragm  120 . The back plate  140  may be positioned in the vibration area VA. The back plate  140  is spaced apart from the diaphragm  120  and is provided to face the diaphragm  120 . Like the diaphragm  120 , the back plate  140  may have a disc shape. The back plate  140  may be doped with impurities by implanting the impurities through an ion-implanting process. 
     The first supporting member  130  is disposed in the supporting area SA. The first supporting member  130  is adjacent to a peripheral portion of the diaphragm  120  to be arranged along the peripheral portion of the diaphragm  120 . The first supporting member  130  includes a plurality of first dam portions  131  arranged along the peripheral portion and connected to the diaphragm  120 , and a plurality of first slit portions  133  defined by the first dam portions  131  adjacent to each other. The first dam portions  131  are arranged along the peripheral portion of the diaphragm  120  and are apart from one another. The first dam portions  131  are also arranged to surround the cavity  112 . 
     Each of the first dam portions  131  has a dam shape, that is, a “U” cross-sectional shape as best shown in  FIG. 2 . The first dam portions  131  make contact with the lower face of the substrate  110 . Thus, the first supporting member  130  may support the diaphragm  120  with respect to the substrate  110  from which the diaphragm  120  is spaced apart. 
     The first slit portions  133  are defined by two first dam portions  131  adjacent to each other. Thus, air may flow through the first slit portions  133 . 
     The first slit portions  133  may serve as a fluid pathway through which a wave of the acoustic pressure flows. As shown in  FIG. 1 , each of the first slit portions  133  may have a length smaller than that of each of the first dam portions  131 . Thus, each of the first dam portions  131  may have a planar area larger than that of each of the first slit portions  133 . In particular, a total area of the first slit portions  133  disposed between the first dam portions  131  adjacent to each other may depend on a number of the first slit portions  133 . Thus, the smaller the number of the first slit portions  133 , the smaller the total area of the first slit portions  133 . 
     The second supporting member  135  is disposed in the supporting area SA. The second supporting member  135  surrounds the first supporting member  130 . The second supporting member  135  includes a plurality of second dam portions  136  arranged along the first dam portions  131  and a plurality of second slit portions  138  defined by the second dam portions  136  adjacent to each other. 
     Each of the second dam portions  136  has a dam shape, that is, a “U” sectional shape. The second dam portions  136  make contact with the lower face of the substrate  110 . Thus, the second supporting member  135  may further support the diaphragm  120  together with the first supporting member  130  with respect to the substrate  110  from which the diaphragm  120  is spaced apart. 
     The second slit portions  138  are defined by two second dam portions  136  adjacent to each other. Thus, air may flow through the second slit portions  138 . 
     The second slit portions  138  may serve as a pathway through with the acoustic pressure flows. As shown in  FIG. 1 , each of the second slit portions  138  may have a length smaller than that of each of the dam portions  136 . Thus, each of the second dam portions  136  may have a planar area larger than that of each of the second slit portions  138 . In particular, a total area of the second slit portions  138  disposed between the second dam portions  136  adjacent to each other may depend on a number of the second slit portions  138 . Thus, the smaller the number of the second slit portions  138 , the smaller the total area of the second slit portions  138 . 
     Since the second supporting member  135  including the second dam portions  136  and the second slit portions  138  is further disposed on the substrate  110 , a pathway through which a wave of acoustic pressure flows may be elongated. Thus, an acoustic resistance of the acoustic pressure which flows through the first and second supporting members  130  and  135  may be increased. 
     Accordingly, the MEMS microphone  101  has a low pass filter effect, which may weakens a noise component in a high frequency range. As a result, the MEMS microphone  101  may have an excellent Signal-to-Noise Ratio (SNR). 
     In some example embodiments, the MEMS microphone  101  may further include an upper insulation layer  160  and a chamber portion  162 . 
     The upper insulation layer  160  may be disposed over the substrate  110 . The upper insulation layer  160  may cover a top surface of the back plate  140 . The upper insulation layer  160  may hold the back plate  140  and may be connected with the chamber portion  162  to space the back plate  140  apart from the diaphragm  120 . 
     As show in  FIG. 2 , the upper insulation layer  160  is spaced apart from the diaphragm  120  to form the air gap AG between the diaphragm  120  and the back plate  140 . 
     The back plate  140  and the upper insulation layer  160  may be provided to be freely bendable with response to the acoustic pressure. 
     A plurality of acoustic holes  142  is formed through the back plate  140  such that acoustic pressure passes through the acoustic holes  142 . The acoustic holes  142  penetrate through the back plate  140  and the upper insulation layer  160  to communicate with the air gap AG. 
     In an embodiment, the back plate  140  may have a plurality of dimple holes  144 , and the upper insulation layer  160  may have a plurality of dimples  164  positioned to correspond to those of the dimple holes  144 . The dimple holes  144  penetrate through the back plate  140 , and the dimples  164  are provided at positions where the dimple holes  144  are formed. 
     The dimples  164  may prevent the diaphragm  120  from being coupled to a lower face of the back plate  140 . That is, when the sound reaches to the diaphragm  120 , the diaphragm  120  can be bent in a semicircular shape toward the back plate  140 , and then can return to its initial position. A bending degree of the diaphragm  120  may vary depending on the sound pressure and may be increased to such an extent that an upper face of the diaphragm  120  makes contact with the lower face of the back plate  140 . When the diaphragm  120  is bent so much as to contact the back plate  140 , the diaphragm  120  may attach to the back plate  140  and may not return to the initial position. In order to prevent the diaphragm  120  from permanently attaching to the back plate  140 , the dimple  164  may protrude from a lower face of the back plate  140  toward the diaphragm  120 . When the diaphragm  120  is bent so much as to contact the back plate  140 , the dimples  164  make contact with the diaphragm  120  and prevent the diaphragm  120  from sticking along its entire surface, so that the diaphragm  120  can to return to the initial position. 
     The chamber portion  162  may be positioned at a boundary region between the supporting area SA and the peripheral region PA. The chamber portion  162  may support the upper insulation layer  160  to maintain the upper insulation layer  160  and the back plate  140  to be apart from the diaphragm  120 . As shown  FIG. 1 , the chamber portion  162  may have a ring shape to surround the diaphragm  120 . The chamber portion  162  may be positioned to be apart from the diaphragm  120  and the second supporting member  135  in a plan view. 
     The chamber portion  162  may extend from an edge portion of the upper insulation layer  160  toward the substrate  110 . The chamber portion  162  has a lower face making contact with the lower face of the substrate  110 . 
     In an embodiment, the chamber portion  162  may have a cross-section of a “U” shape, as shown in  FIG. 2 . The chamber portion  162  may be integrally formed with the upper insulation layer  160 . 
     As shown in  FIG. 2 , the chamber portion  162  may be spaced apart from the diaphragm  120  and may be positioned outside from the second supporting member  135 . As shown in  FIG. 1 , the chamber portion  162  may have a ring shape. 
     In an example embodiment, the MEM microphone  101  may further include a lower insulation layer  150 , a sacrificial layer  170 , a diaphragm pad  182 , a back plate pad  184 , a first pad electrode  192  and a second pad electrode  194 . 
     In particular, the lower insulation layer  150  may be disposed on the upper surface of the substrate  110  and under the upper insulation layer  160   
     The diaphragm pad  182  may be disposed on the upper face of the lower insulation layer  150  and in the peripheral area PA. The diaphragm pad  182  may be electrically connected to the diaphragm  120 . The diaphragm pad  182  may be doped with impurities by an ion-implanting process. Even though not shown in detail, a connection porting of connecting the diaphragm  120  with the diaphragm pad  182  may be doped with impurities as well. 
     The sacrificial layer  170  may be disposed on the lower insulation layer  150  to cover the diaphragm pad  182 . Further, the sacrificial layer  170  is disposed beneath the upper insulation layer  160 . As shown in  FIG. 2 , the lower insulation layer  150  and the sacrificial layer  170  are located in the peripheral area PA. Here, the lower insulation layer  150  and the sacrificial layer  170  may be located outside from the chamber portion  162  in a plan view. Further, the lower insulation layer  150  and the sacrificial layer  170  may be formed using materials different from each other. 
     The back plate pad  184  may be formed on an upper face of the sacrificial layer  170  and in the peripheral area PA. The back plate pad  184  is electrically connected to the back plate  140  and may be formed with impurities by an ion implanting process. Even though not shown in detail, a connection porting of connecting the back plate  140  with the back plate pad  184  may be doped with impurities as well. 
     The first and second pad electrodes  192  and  194  may be formed on the upper insulation layer  160  and in the peripheral area PA. The first pad electrode  192  is located in a first contact hole CH 1  to make contact with the diaphragm pad  182 . On the other hand, the second pad electrode  194  is located in a second contact hole CH 2  and makes contact with the back plate pad  184 . Here, the first and second pad electrodes  192  and  194  may be transparent electrodes. As shown in  FIG. 2 , the diaphragm pad  182  is exposed through the first contact hole CH 1  formed by partially removing the second insulation layer  160  and the insulating interlayer  170 . The back plate pad  184  is exposed through the second contact hole CH 2  formed by partially removing the second insulation layer  160 . 
     According to some example embodiment, the MEMS microphone  101  includes the first supporting member  130  and the second supporting member  135  which surround the diaphragm  120 , and the first and the second supporting members  130  and  135  include the first and the second slit portions  133  and  138  having variable area, respectively. In particular, since the first and the second slit portions  133  and  138  may serve as pathways through which acoustic pressure may flow, the MEMS microphone  101  has less outlet area for the acoustic pressure to escape the cavity  112 , such that the MEMS microphone  101  has an increased acoustic resistance. Thus, since the MEMS microphone  101  has a low pass filter effect, the noise component may be weakened while the acoustic pressure having a relatively high frequency is applied. As a result, the MEMS microphone  101  may have improved SNR characteristics 
     In an example embodiment of the present invention, the first and second supporting members  130  and  135  are concentrically arranged. That is, the first and second supporting members  130  and  135  may be arranged along an arc with respect to a center of the cavity  112 , respectively. 
     In an example embodiment of the present invention, the first and second slit portions  133  and  138  may be alternately arranged in a plan view. That is, the first and second slit portions  133  and  138  may not be aligned along radial lines extending outwardly from the center of the device  101 . Therefore, as the resistance of the air discharged from the air gap AG increases, the acoustic pressure resistance of the MEMS microphone  101  may be increased. 
     Hereinafter, a method of manufacturing a MEMS microphone  101  will be described in detail with reference to the drawings. 
       FIG. 5  is a flow chart illustrating a method of manufacturing a MEMS microphone in accordance with an example embodiment of the present invention.  FIG. 6  is a plan view illustrating the lower insulation layer  150  having the first and the second dam holes ( 151  and  156 , respectively).  FIGS. 7 to 17  are cross sectional views illustrating a method of manufacturing a MEMS microphone in accordance with an example embodiment of the present invention. 
     Referring to  FIGS. 5 to 9  according to an example embodiment of a method for manufacturing a MEMS microphone, a lower insulation layer  150  is formed on a substrate  110  (S 110 ). 
     Next, first dam portions  131  and second dam portions  136  are formed on the lower insulation layer  150  (S 120 ). 
     Forming the first and the second dam portions  131  and  136  will be explained in detail as below. 
     As shown in  FIGS. 6 and 7 , the lower insulation layer  150  is patterned to form first dam holes  151  and second dam holes  156  in a supporting area SA for forming the first and the second supporting members  130  and  135 . The substrate  110  may be partially exposed through the first and the second dam holes  151  and  156 . As shown in  FIG. 7 , the first dam holes  151  are arranged to surround a vibration area VA. The first dam holes  151  are arranged along a peripheral edge of the vibration area VA. Further, the second dam holes  156  may be arranged to surround the first dam holes  151  (see  FIG. 6 ). The first and the second dam holes  151  and  156  are disposed in the supporting area SA. 
     Next, as shown in  FIG. 8 , a first silicon layer  10  is formed on the lower insulation layer  150  to cover the first and the second dam holes  151  and  156 . The first silicon layer  10  may be formed using polysilicon by a chemical vapor deposition process. Further, impurities may be doped into the vibration area VA of the first silicon layer  10  through an ion implanting process for forming a diaphragm  120  having a relatively low resistance in the vibration area VA and a diaphragm pad  182  in the peripheral area PA in a subsequent patterning process. 
     Next, as shown in  FIG. 9 , the first silicon layer  10  is patterned to form a diaphragm  120  in the vibration area VA, the first and the second dam portions  131  and  136  (see  FIGS. 1 and 9 ) in the supporting area SA, and the diaphragm pad  182  in the peripheral area PA. 
     Referring to  FIGS. 5 and 10 , a sacrificial layer  170  is formed on the lower insulation layer  150  to cover the diaphragm  120  and the diaphragm pad  182  (S 130 ). 
     Next, a back plate  140  is formed on the sacrificial layer  170  (S 140 ). 
     At S 140 , the back plate  140  is formed on the sacrificial layer  170 , as will be explained in detail below. 
     Referring to  FIG. 10 , a second silicon layer  20  is formed on the sacrificial layer  170  and then, the second silicon layer  20  is doped with impurities by an ion implanting process. Here, the second silicon layer  20  may be formed using polysilicon. 
     Then, as shown in  FIG. 11 , the second silicon layer  20  is patterned to form a back plate  140  having dimple holes  144  in the vibration area VA. Further, a portion of the sacrificial layer  170 , which correspond to the dimple holes  144 , may be further etched such that the dimples  164  protrude from a lower face of the back plate  140  in a subsequent process. 
     Referring to  FIGS. 5, 12 and 13 , an upper insulation layer  160  and a chamber portion  162  are formed on the sacrificial layer to cover the back plate  140  (S 150 ). 
     At S 150 , forming the upper insulation layer  160  and the chamber portion  162  is performed, as will be explained in detail below. 
     As shown in  FIG. 12 , the sacrificial layer  170  and the lower insulation layer  150  are patterned to form a chamber hole  30  in the supporting area SA for forming a chamber portion  162 . The substrate  110  may be partially exposed through the chamber hole  30 . The chamber hole  30  may have a ring shape and may surround the second dam portions  138 . 
     After forming an insulation layer  40  on the sacrificial layer  170  to cover a sidewall and a bottom of the chamber hole  30 , the insulation layer  40  is patterned to form the upper insulation layer  160  and the chamber portion  162 . Further, the dimples  164  may be further formed in the dimple holes  144 , and a second contact hole CH 2  is formed in the peripheral area PA to expose the back plate pad  184 . Furthermore, portions of the insulation layer  140  and the sacrificial layer  170 , which are positioned over the diaphragm pad  182 , are etched to form a first contact hole CH 1  in the peripheral area PA. 
     In an embodiment of the present invention, the insulation layer  40  may be formed of a material different from that of the lower insulation layer  150  and the sacrificial layer  170 . For example, the insulation layer  40  is formed of silicon nitride, whereas the lower insulation layer  150  and the sacrificial layer  170  may be formed of silicon oxide. 
     Referring to  FIGS. 5, 14 and 15 , after the first and second contact holes CH 1  and CH 2  are formed, first and second pad electrodes  192  and  194  are formed in the peripheral region PA (S 160 ). 
     As shown in  FIG. 14 , a thin film  50  is formed on the upper insulation layer  160  on which the first and second contact holes CH 1  and CH 2  are formed. Here, the thin film  50  may be made of a conductive metal. 
     Next, as shown in  FIG. 15 , the thin film  50  is patterned to form the first and second pad electrodes  192  and  194 . 
     Referring to  FIGS. 5 and 16 , the upper insulation layer  160  and the back plate  140  are patterned to form acoustic holes  142  in the vibration region VA (S 170 ). 
     Referring to  FIGS. 5 and 17 , after forming the acoustic holes  142 , the substrate  110  is patterned to form a cavity  112  in the vibration area VA (S 180 ). The lower insulation layer  150  is partially exposed through the cavity  112 . 
     The sacrificial layer  170  and the lower insulation layer  150  are partially etched through an etch process using the cavity  112  and the acoustic holes  142  (S 190 ). As a result, the diaphragm  120  is exposed through the cavity  112 , and an air gap AG between the diaphragm  120  and the back plate  140  is formed. Further, a portion of the lower insulation layer  150 , located between the first and second dam portions  131  and  136 , is removed to form a first slit portion  133  and a second slit portion  138  (see  FIG. 1 ). Accordingly, as shown in  FIGS. 1 and 2 , the MEMS microphone  101  is manufactured. Here, the cavity  112  and the acoustic holes  142  may be provided as a pathway for the etchant for removing portions of the lower insulation layer  150  and the sacrificial layer  170 . 
     Particularly, at S 190 , removing the sacrificial layer  170  and the lower insulation layer  150  from the vibration area VA and the supporting area SA, the first and second dam portions  131  and  136  and the chamber portion  162  may limit the movement of the etchant. Thus, an etch amount of the sacrificial layer  170  and the lower insulation layer  150  may be easily adjusted and a portion of the lower insulation layer  150 , positioned inside the first and second dam portions  131  and  136 , may be protected from remaining. 
     In an example embodiment of the present invention, HF vapor may be used as an etchant for removing the sacrificial layer  170  and the lower insulation layer  150 . 
     As described above, the method of manufacturing the MEMS microphone may include forming the first dam portions  131  and the second dam portions  136  to extend along the circumference of the diaphragm  120  without any additional process. 
     Although the MEM microphone and the method of manufacturing the MEMS microphone have been described with reference to the specific embodiments, they are not limited thereto. Therefore, it will be readily understood by those skilled in the art that various modifications and changes can be made thereto without departing from the spirit and scope of the appended claims. 
     Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions. 
     Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted. 
     Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended. 
     Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein. 
     For purposes of interpreting the claims, it is expressly intended that the provisions of 35 U.S.C. § 112(f) are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim.