Patent Publication Number: US-10313797-B2

Title: Microphone, manufacturing method and control method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2016-0116718 filed in the Korean Intellectual Property Office on Sep. 9, 2016, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     (a) Field of the Disclosure 
     The present disclosure relates to a microphone and more particularly, to a method of manufacturing the microphone and a control method thereof. 
     (b) Description of the Related Art 
     Generally, a microphone is a device that converts a voice into an electric signal and is applicable to mobile communication devices that include a terminal and various communication devices (e.g., an earphone or a hearing aid). Recently, the size of the microphone has been reduced and a micro electro mechanical system (MEMS) microphone using the MEMS technology has been developed. The MEMS microphone is manufactured using a semiconductor process and has improved resistance to moisture and thermal exposure than an electret condenser microphone (ECM) in the related art. For example, the microphone may be advantageously reduced in size and integrated with a signal processing circuit. The MEMS microphone has a structure with an acoustic overload point (AOP), sensitivity, and a signal to noise ratio (SNR) among the required specifications. 
     Accordingly, in a case of high sensitivity, the MEMS microphone according to the related art has a reduced AOP that limits detection of a loud sound and in a case of low sensitivity, the MEMS microphone has a high AOP. In other words, the MEMS microphone detects a loud sound, but has poor performance in detection of a low sound. Accordingly, it is necessary to research and develop the MEMS microphone having a wide acoustic pressure measurement range. 
     The above information disclosed in this section is merely for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     The present disclosure provides a microphone that improves an acoustic pressure measurement range and a method of manufacturing the microphone and a control method thereof. 
     An exemplary embodiment of the present disclosure provides a microphone that may include an insulating layer bonded to a surface of a substrate, in which a sound inlet is formed and having a plurality of sound apertures; a diaphragm formed at a position that corresponds to the sound inlet of the substrate on an upper surface of the insulating layer; a displacement adjusting layer disposed in a circumference of the diaphragm on the upper surface of the insulating layer and configured to adjust a hardness of the diaphragm based on an input sound and a fixing layer disposed on the diaphragm and the displacement adjusting layer while being spaced apart from the diaphragm and the displacement adjusting layer. 
     The displacement adjusting layer may include a first adjusting layer formed adjacent to a circumference of the diaphragm, a second adjusting layer formed along a circumference of the first adjusting layer spaced apart from the first adjusting layer and a first pad coupled to the first adjusting layer and a second pad coupled to the second adjusting layer. 
     A plurality of displacement adjusting units may be formed between the first adjusting layer and the second adjusting layer. In the displacement adjusting unit, a plurality of first protruding steps extending from the first adjusting layer to an external side may be alternately disposed with a plurality of second protruding steps extending from the second adjusting layer to an internal side. The displacement adjusting units may be formed at portions that correspond to the sound apertures of the insulating layer. 
     The fixing layer may be fixed by a sacrificial layer formed along a border of the upper surface of the insulating layer. The fixing layer may include a plurality of apertures. According to the exemplary embodiments of the present disclosure, an acceptable acoustic pressure measurement range may be improved by adjusting hardness of the diaphragm by applying a voltage to the displacement adjusting layer formed adjacent to the diaphragm based on an input acoustic signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present disclosure will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is an exemplary top plan view of a microphone according to an exemplary embodiment of the present disclosure; 
         FIG. 2  is an exemplary cross-sectional view taken along line A-A′ of  FIG. 1  according to an exemplary embodiment of the present disclosure; 
         FIGS. 3 to 8  are exemplary process diagrams sequentially illustrating a manufacturing method of the microphone according to an exemplary embodiment of the present disclosure; and 
         FIG. 9  is an exemplary flowchart illustrating a control method of the microphone according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an exemplary embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. However, the accompanying drawings and detailed descriptions are related to one exemplary embodiment among various exemplary embodiments for effectively describing the characteristic of the present disclosure. Accordingly, the present disclosure is not limited to the drawings and descriptions below. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. For example, in order to make the description of the present disclosure clear, unrelated parts are not shown and, the thicknesses of layers and regions are exaggerated for clarity. Further, when it is stated that a layer is “on” another layer or substrate, the layer may be directly on another layer or substrate or a third layer may be disposed therebetween. 
     It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Furthermore, control logic of the present disclosure may be embodied as non-transitory computer readable media on a computer readable medium containing executable program instructions executed by a processor, controller/control unit or the like. Examples of the computer readable mediums include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards and optical data storage devices. The computer readable recording medium can also be distributed in network coupled computer systems so that the computer readable media is stored and executed in a distributed fashion, e.g., by a telematics server or a Controller Area Network (CAN). 
     It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles. 
       FIG. 1  is an exemplary top plan view of a microphone according to an exemplary embodiment of the present disclosure.  FIG. 2  is an exemplary cross-sectional view taken along line A-A′ of  FIG. 1 . A microphone  1  according to an exemplary embodiment of the present disclosure may have a wide acoustic pressure measurement range and may be configured to measure an acoustic signal regardless of a register of the input acoustic signal. Further, the microphone  1  according to the exemplary embodiment of the present disclosure may be manufactured based on a micro electro mechanical system (MEMS) technology. 
     A general structure of the microphone  1  will be briefly described with reference to  FIG. 1 . A diaphragm  20  and a displacement adjusting layer  30  may be formed on an upper surface of a substrate  10 , in which a sound inlet  11  may be formed at a center thereof, through an insulating layer  13 . A fixing layer  40  may be formed on the diaphragm  20  and the displacement adjusting layer  30  while being separated apart from the diaphragm  20  and the displacement adjusting layer  30  by a predetermined interval. In particular, for convenience of the description, an illustration of a aperture of the fixing layer  40  is omitted. 
     The microphone  1  may have a structure that adjusts a displacement, (e.g., hardness) of the diaphragm  20  by adjusting a voltage applied to the displacement adjusting layer  30  based on an acoustic pressure of the input sound. Herein, the displacement of the diaphragm  20  refers to a change in a distance between the diaphragm  20  and the fixing layer  40 . In other words, the microphone  1  adjusts hardness of the diaphragm  20  based on the acoustic pressure of the input sound and adjusts a capacitance value between the diaphragm  20  and the fixing layer  40 . 
     The microphone  1  will be described in more detail. The substrate  10  may be formed of a poly silicon, and the sound inlet  11  may be formed at the center of the substrate  10 . Further, the insulating layer  13  may be bonded to the upper surface of the substrate  10 . In particular, the insulating layer  13  may include a plurality of acoustic apertures, and may be formed of a silicon nitride (SiN). 
     Referring to  FIG. 2 , the diaphragm  20  may be disposed on an upper surface of the insulating layer  13 . In particular, the diaphragm  20  may be formed of a conductive material and may vibrate in a state of being bonded to the insulating layer  13 . The diaphragm  20  may be formed in a circular shape and an electrode pad  21  may extend at one side of the diaphragm  20  to electrically connect the diaphragm  20  with an external signal processing circuit  60 . The present disclosure has been described based on when the diaphragm  20  is formed in a circular shape as an example, but is not limited thereto, and the shape of the diaphragm  20  may be changed and applied as necessary. 
     Further, the displacement adjusting layer  30  may be disposed on an upper surface of the insulating layer  13 . In other words, the displacement adjusting layer  30  may be formed of a conductive material similar to the diaphragm  20 . A portion of the displacement adjusting layer  30  that corresponds to a sound aperture  15  formed in the insulating layer  13  may be when bonded to the insulating layer  13 . 
     The displacement adjusting layer  30  may be disposed to enclose an exterior surface of the diaphragm  20  in a single layer with the diaphragm  20  and may be formed of a first adjusting layer  30   a , a second adjusting layer  30   b , a first pad  33   a , and a second pad  33   b . Particularly, the first adjusting layer  30   a  may be formed adjacent to a circumference of an exterior surface of the diaphragm  20  and may include a plurality of first protruding steps  35   a  that extend to the exterior. Further, the second adjusting layer  30  may be formed along a circumference of the first adjusting layer  30   a  when spaced apart from the first adjusting layer  30   a  by a predetermined interval. The second adjusting layer  30   b  may include a plurality of second protruding steps  35   b  that extend inwardly at the positions that correspond to the first protruding steps  35   a  of the first adjusting layer  30   a.    
     In other words, the first protruding step  35   a  and the second protruding step  35   b  may be alternately disposed and may form a shape (e.g., comb finger) to form a displacement adjusting unit  31 . In particular, the displacement adjusting unit  31  may be formed by the first protruding step  35   a  and the second protruding step  35   b . The plurality of displacement adjusting units  31  may be formed between the first adjusting layer  30   a  and the second adjusting layer  30   b  along a circumference. 
     The displacement adjusting layer  30  may be electrically connected with the external signal processing circuit  60  via the first pad  33   a  connected with the first adjusting layer  30   a  and the second pad  33   b  connected with the second adjusting layer  30   b . Further, the fixing layer  40  may be disposed on the diaphragm  20  and the displacement adjusting layer  30 . The fixing layer  40  may be fixed by a sacrificial layer  50  formed along a border of the upper surface of the insulating layer  13 . In addition, the fixing layer  40  may be formed of a conductive material and may include a plurality of apertures  41 . 
     The fixing layer  40  may be formed in a single layer or may be formed in double layers. In particular, the fixing layer  40  may be formed in a single layer including an electrode layer formed of poly silicon or may be formed in double layers including an electrode layer formed of poly silicon and an insulating layer formed of a silicon nitride disposed on an upper surface of the electrode layer. The fixing layer  40  may be electrically connected with the signal processing circuit  60  at one side thereof. 
     Hereinafter, a manufacturing method of a microphone according to an exemplary embodiment of the present disclosure will be described.  FIGS. 3 to 8  are process diagrams sequentially illustrating a manufacturing method of the microphone according to an exemplary embodiment of the present disclosure. Referring to  FIG. 3 , a substrate  10  may be prepared, and then an insulating layer  13  may be formed on an upper surface of the substrate  10 . In other words, a plurality of sound apertures  15  may be formed on the insulating layer  13 . 
     Referring to  FIG. 4 , a diaphragm  20  may be formed on an upper surface of the insulating layer  13 . The diaphragm  20  may include an electrode pad  21  that extends at one side thereof and may be formed at a center of the upper portion of the insulating layer  13 . A displacement adjusting layer  30  may be formed to enclose an exterior surface of the diaphragm  20  on the upper surface of the insulating layer  13 . In particular, in the operation of forming the displacement adjusting layer  30 , a first adjusting layer  30   a , formed adjacent to a circumference of the exterior surface of the diaphragm  20  may be formed. 
     Further, a second adjusting layer  30   b , formed along a circumference of an exterior surface of the first adjusting layer  30   a , may be formed spaced apart from the first adjusting layer  30   a  by a predetermined interval. Additionally, a plurality of displacement adjusting units  31  formed between the first adjusting layer  30   a  and the second adjusting layer  30   b  may be positioned to correspond to the plurality of sound apertures  15  of the insulating layer  13 , respectively. In other words, a first protruding step  35   a  of the first adjusting layer  30   a  and a second protruding step  35   b  of the second adjusting layer  30   b  may be alternately disposed to form the displacement adjusting unit  31 . 
     Referring to  FIG. 5 , a sacrificial layer  50  may be formed on the upper surface of the insulating layer  13 . In other words, the sacrificial layer  50  may be formed to cover the diaphragm  20  and the displacement adjusting layer  30  and may be formed of silica (SiO 2 ). 
     Referring to  FIG. 6 , a fixing layer  40  may be formed on an upper surface of the sacrificial layer  50 . For example, the fixing layer  40  may be formed in a single layer and may alternatively be formed in double layers. In other words, the fixing layer  40  may be formed in a single layer including an electrode layer formed of poly silicon and may be formed in double layers including an electrode layer formed of poly silicon and an insulating layer formed of a silicon nitride on an upper surface of the electrode layer. Subsequently, a plurality of apertures  41  may be formed in the fixing layer  40 . Simultaneously, the electrode pad  21  may be exposed by etching the sacrificial layer  50  that corresponds to the electrode pad  21  of the diaphragm  20 . 
     Referring to  FIG. 7 , a sound inlet  11 , which passes through the substrate  10 , may be formed by etching a rear surface of the substrate  10 . The sound inlet  11  may be formed be at about a center of the substrate  10 . Referring to  FIG. 8 , a portion of the sacrificial layer  50  may be removed through the sound inlet  11  and the sound apertures  15 . In other words, the remaining portions, except for a border of the sacrificial layer  50  may be removed. 
     Hereinafter, a control method of the microphone according to an exemplary embodiment of the present disclosure will be described.  FIG. 9  is an exemplary flowchart illustrating a control method of the microphone according to an exemplary embodiment of the present disclosure. Referring to  FIG. 9 , the microphone  1  may be configured to receive a sound from the exterior. 
     The signal processing circuit  60  may be configured to measure a capacitance value, which may be adjusted by a sound input into the microphone  1 , between the diaphragm  20  and the fixing layer  40  and may be configured to calculate an input acoustic pressure (S 910 ). The signal processing circuit  60  may be configured to compare the input acoustic pressure and a predetermined acoustic pressure, and determine whether the input acoustic pressure exceeds the predetermined acoustic pressure (S 920 ). In particular, when the input acoustic pressure is greater than the predetermined acoustic pressure, the signal processing circuit  60  may be configured to apply a voltage to the displacement adjusting unit  31  and to improve hardness of the diaphragm  20  (S 930 ). In other words, according to the application of the voltage to the displacement adjusting unit  31 , hardness of the diaphragm  20  may be improved by gravitation generated between the first protruding step  35   a  and the second protruding step  35   b  of the displacement adjusting unit  31 . 
     The displacement adjusting unit  31  may be vibrated relatively less even though a sound having a high input acoustic pressure may be input. Accordingly the microphone  1  may be configured to measure the sound by decreasing sensitivity of the sound, and the hardness of the displacement adjusting unit  31  may be maintained until a displacement of a newly input voltage is generated. Further, when the input acoustic pressure is equal to or less than the predetermined acoustic pressure, the signal processing circuit  60  may be configured to output the sound and terminate the operation. 
     When a new sound is input when the hardness of the displacement adjusting unit  31  is improved, the signal processing circuit  60  may be configured to compare an input acoustic pressure of the newly input sound with the predetermined acoustic pressure and determine whether the input acoustic pressure is less than the predetermined acoustic pressure (S 940 ). In particular, when the input acoustic pressure is less than the predetermined acoustic pressure, the signal processing circuit  60  may be configured to decrease a voltage applied to the displacement adjusting unit  31  and decrease the improved hardness of the diaphragm  20  (S 950 ). Herein, the signal processing circuit  60  may be configured to decrease the hardness of the displacement adjusting unit  31  until the hardness of the displacement adjusting unit  31  is in an initial state. 
     Additionally, when the input acoustic pressure is equal to or greater than the predetermined acoustic pressure, the signal processing circuit  60  may be configured to determine whether the input acoustic pressure is equal to the predetermined acoustic pressure again (S 960 ). In particular, when the input acoustic pressure is equal to the predetermined acoustic pressure, the signal processing circuit  60  may be configured to output the sound and terminate the operation. 
     Further, when the input acoustic pressure is greater than the predetermined acoustic pressure, the signal processing circuit  60  may be configured to improve hardness of the displacement adjusting unit  31  by increasing a voltage applied to the displacement adjusting unit  31 . The signal processing circuit  60  may be configured to compare the input acoustic pressure with the predetermined acoustic pressure and increase an acoustic pressure measurement range by continuously repeating the aforementioned process. Accordingly, the microphone  1  according to the exemplary embodiment of the present disclosure may improve an acoustic pressure measurement range by adjusting a displacement of the diaphragm  20  according to an acoustic pressure of an acoustic signal. 
     In particular, even though an acoustic signal having a high acoustic pressure or an acoustic signal having a low acoustic pressure is input, the microphone  1  may improve an acoustic pressure measurement range by adjusting a size of a voltage applied to the displacement adjusting layer  30  and adjusting hardness of the diaphragm  20 . Accordingly, the microphone  1  may be configured to detect a wide acoustic pressure range and output an acoustic signal based on the detected acoustic pressure range. 
     While this disclosure has been described in connection with what is presently considered to be example embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
     DESCRIPTION OF SYMBOLS 
     
         
         
           
               1  . . . Microphone 
               10  . . . Substrate 
               11  . . . Sound aperture 
               20  . . . Diaphragm 
               21  . . . Sound inlet 
               30  . . . Displacement adjusting layer 
               30   a  . . . First adjusting layer 
               30   b  . . . Second adjusting layer 
               31  . . . Displacement adjusting unit 
               33   a  . . . First pad 
               33   b  . . . Second pad 
               35   a  . . . First protruding step 
               35   b  . . . Second protruding step 
               40  . . . Fixing layer 
               41  . . . Through-aperture 
               50  . . . Sacrificial layer 
               60  . . . Signal processing circuit