Abstract:
A microphone, that increases sensitivity without a separate circuit is provided. The microphone includes an audio detection module having a vibration film that outputs capacitance signals by vibrating audio introduced from the exterior and a piezoresistive element that outputs a piezoresistive signal by a sound pressure of the audio. A semiconductor chip includes an amplifier electrically connected to the audio detection module to receive a capacitance signal and a piezoresistive signal from the audio detection module and amplifies the capacitance signal and piezoresistive signal to an electrical signal. The amplifier includes an input terminal that receives an input of the capacitance signal; a first resistor connected to the input terminal and the piezoresistive element; an output terminal that amplifies and outputs the capacitance signal and piezoresistive signal to an electrical signal; and a second resistor connected to the input terminal and the output terminal and connected to the piezoresistive element.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2014-0160336 filed in the Korean Intellectual Property Office on Nov. 17, 2014, the entire contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    (a) Field of the Invention 
         [0003]    The present invention relates to a microphone and more particularly, to a microphone that improves sensitivity without adding a separate circuit. 
         [0004]    (b) Description of the Related Art 
         [0005]    In general, a microphone is a device that converts audio to an electrical signal. A microphone should improve electromagnetic and audio performance, reliability, and operability. Additionally, a microphone is gradually formed to have a reduced size. Accordingly, a microphone using Micro Electro Mechanical System (MEMS) technology has been developed. 
         [0006]    The MEMS microphone has a tolerance against moisture and heat, compared with a conventional Electret Condenser Microphone (ECM), and can be reduced in size and be integrated into a signal processing circuit. In general, a MEMS microphone may be classified into a piezoelectric MEMS microphone and a capacitive MEMS microphone. 
         [0007]    The piezoelectric MEMS microphone is formed with a vibration film, and when the vibration film is changed by external audio, an electrical signal occurs due to a piezoelectric effect and thus a sound pressure is measured. The capacitive MEMS microphone includes a fixed electrode and a vibration film, and when audio is applied from the exterior to the vibration film, while a gap between the fixed electrode and the vibration film is changed, a capacitance value is changed. A sound pressure is measured based on an electrical signal occurring during the process. 
         [0008]    However, because a vibration displacement of a film is limited, the method of increased sensitivity is limited. Accordingly, a method of increasing strength by simultaneously outputting and adding a signal of another form is introduced. For example, in conventional methods, a signal processing circuit is required for each of two output signals, when an additional circuit that adds signals is required. Accordingly, a semiconductor chip area increases resulting in price increases and a power consumption increase. 
         [0009]    The above information disclosed in this section is merely for enhancement of understanding of the background of the invention 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 
       [0010]    The present invention provides a microphone having improved sensitivity and may reflect a change of resistance to an amplifying rate by connecting a piezoresistive element of an audio detection module to a semiconductor chip. 
         [0011]    An exemplary embodiment of the present invention provides a microphone that may include: an audio detection module having a vibration film that may output a capacitance signal by vibrating by audio introduced from the exterior and a piezoresistive element that may output a piezoresistive signal by a sound pressure of the audio; and a semiconductor chip having an amplifier electrically connected to the audio detection module to receive a capacitance signal and a piezoresistive signal from the audio detection module and configured to amplify the capacitance signal and piezoresistive signal to an electrical signal. The amplifier may include: an input terminal configured to receive an input of the capacitance signal; a first resistor connected to the input terminal and connected to the piezoresistive element; an output terminal configured to amplify and output the capacitance signal and piezoresistive signal to an electrical signal; and a second resistor connected to the input terminal and the output terminal and connected to the piezoresistive element. 
         [0012]    The audio detection module may further include: first and second pads connected to the piezoresistive element; and an output pad configured to output the capacitance signal to the semiconductor chip. Additionally, the first pad may be connected to the first resistor, and the second pad may be connected to the second resistor. Furthermore, the piezoresistive element may be changed based on the sound pressure and may be connected to the first and second resistors via the first and second pads, respectively. 
         [0013]    The input terminal may include: a non-inverting input terminal connected to the output pad that may output the capacitance signal; and an inverting input terminal connected to the first and second resistors and the piezoresistive element. The input terminal may include: a non-inverting input terminal connected to the ground; and an inverting input terminal connected to an output pad that may output the capacitance signal, the first and second resistors, and the piezoresistive element. The amplifier may be an inverting amplifier or a non-inverting amplifier. 
         [0014]    Another exemplary embodiment of the present invention provides a microphone which may include: an audio detection module configured to output a capacitance signal which may change by a vibration film that vibrates by audio introduced from the exterior and a fixed electrode and a piezoresistive signal occurring when a sound pressure is applied to a piezoresistive element by the audio. The microphone may further include a semiconductor chip having an amplifier configured to receive the capacitance signal and the piezoresistive signal and amplify the capacitance signal and the piezoresistive signal to an electrical signal. The amplifier may include: a non-inverting input terminal configured to receive an input of the capacitance signal; an inverting input terminal configured to receive an input of the piezoresistive signal connected to the first and second resistors. The amplifier may further include an output terminal configured to amplify and output the capacitance signal and the piezoresistive signal to an electrical signal. 
         [0015]    In another exemplary embodiment a microphone may include: an audio detection module having a vibration film that may output a capacitance signal by vibrating by audio introduced from the exterior and a piezoresistive element that may output a piezoresistive signal by the audio. The microphone may further include a semiconductor chip including an amplifier electrically connected to the audio detection module to receive a capacitance signal and a piezoresistive signal from the audio detection module configured to amplify the capacitance signal and the piezoresistive signal to an electrical signal. The amplifier may further include: a non-inverting input terminal connected to the ground; an inverting input terminal configured to receive an input of the capacitance signal; a first resistor connected to the inverting input terminal and connected to the piezoresistive element; a second resistor connected to the inverting input terminal and connected to the piezoresistive element; and an output terminal connected to the second resistor and configured to amplify and output the capacitance signal to an electrical signal based on the piezoresistive element, the first resistor, and the second resistor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    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. 
           [0017]      FIG. 1  is an exemplary diagram illustrating a microphone according to an exemplary embodiment of the present invention; 
           [0018]      FIG. 2  is an exemplary cross-sectional view illustrating an audio detection module and a circuit diagram illustrating a semiconductor chip according to an exemplary embodiment of the present invention; 
           [0019]      FIG. 3  is an exemplary diagram illustrating a situation in which audio is introduced into a microphone according to an exemplary embodiment of the present invention; 
           [0020]      FIG. 4  is an exemplary cross-sectional view illustrating an audio detection module and a circuit diagram illustrating a semiconductor chip according to another exemplary embodiment of the present invention; and 
           [0021]      FIG. 5  is an exemplary diagram illustrating a situation in which audio is introduced into a microphone according to another exemplary embodiment of the present invention. 
       
    
    
     DESCRIPTION OF SYMBOLS 
       [0022]      50 : microphone 
         [0023]      100 : audio detection module 
         [0024]      110 : substrate 
         [0025]      130 : vibration film 
         [0026]      140 : piezoresistive element 
         [0027]      151 ,  155 : pad 
         [0028]      153 : output pad 
         [0029]      160 : support layer 
         [0030]      170 : fixed electrode 
         [0031]      200 : semiconductor chip 
         [0032]      210 : non-inverting amplifier 
         [0033]      220 ,  420 : input terminal 
         [0034]      240 ,  250 ,  440 ,  450 : resistor 
         [0035]      260 ,  470 : output terminal 
         [0036]      410 : non-inverting amplifier 
       DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0037]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. 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 invention 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. 
         [0038]    An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings. 
         [0039]      FIG. 1  is an exemplary diagram illustrating a microphone according to an exemplary embodiment of the present invention, and  FIG. 2  is an exemplary cross-sectional view illustrating an audio detection module and a circuit diagram illustrating a semiconductor chip according to an exemplary embodiment of the present invention. 
         [0040]    Referring to  FIGS. 1 and 2 , a microphone  50  may include an audio detection module  100  and a semiconductor chip  200 . The audio detection module  100  may include a substrate  110 , a vibration film  130 , a piezoresistive element  140 , and a fixed electrode  170 . The substrate  110  may be formed with silicon, and a penetration aperture  115  may be formed in the substrate  110 . An oxide film  120  may be disposed on the substrate  110 . In other words, the oxide film  120  may be disposed between the substrate  110  and the vibration film  130 . The vibration film  130  may be disposed on the oxide film  120  to cover the penetration aperture  115  that may be formed in the substrate  110 . A portion of the vibration film  130  may be exposed by the penetration aperture  115 , and the portion of the vibration film  130  exposed by the penetration aperture  115  may vibrate based on audio introduced from the exterior. The vibration film  130  may have substantially a circular shape and may include a plurality of slots  135 . The slots  135  may be located on the penetration aperture  115 . 
         [0041]    The piezoresistive element  140  may be disposed on the oxide film  120 . The piezoresistive element  140  may be connected to a first pad  151  and a second pad  155 . As shown in  FIG. 3 , when a sound pressure is applied by audio  300  introduced from the exterior, the piezoresistive element  140  may be configured to generate a piezoresistive signal. The piezoresistive signal may be output to the semiconductor chip  200  through the first pad  151  and the second pad  155  connected to the piezoresistive element  140 . In particular, a piezoresistive signal may be a resistance value. 
         [0042]    The first pad  151  and the second pad  155  may be connected to the semiconductor chip  200 . The first pad  151  and second pad  155  may be disposed on the piezoresistive element  140 . An output pad  153  may be disposed on the vibration film  130  and may be connected to the semiconductor chip  200 . A support layer  160  may be disposed at an edge portion of the vibration film  130  and may support the fixed electrode  170 . The fixed electrode  170  may be separately disposed from the vibration film  130 . Additionally, the fixed electrode  170  may include a plurality of air inlets  175  and may be disposed and fixed on the support layer  160 . The fixed electrode  170  may be made of polysilicon or a metal. 
         [0043]    An air layer  165  may be formed between the fixed electrode  170  and the vibration film  130 . The fixed electrode  170  and the vibration film  130  may be separately disposed with a predetermined gap therebetween. As shown in  FIG. 3 , the audio  300  from the exterior may be introduced through the air inlet  175  formed in the fixed electrode  170  to stimulate vibration of the vibration film  130  . . . For example, a gap between the fixed electrode  170  and the vibration film  130  may change and a capacitance signal between the vibration film  130  and the fixed electrode  170  may change. The capacitance signal may be output to the semiconductor chip  200  through the output pad  153  connected to the vibration film  130 . 
         [0044]    The semiconductor chip  200  may be electrically connected to the audio detection module  100 , and may be configured to receive, amplify and output a signal from the audio detection module  100  and detect audio from the exterior. Accordingly, the semiconductor chip  200  may include an amplifier. The amplifier may be a non-inverting amplifier or an inverting amplifier. The non-inverting amplifier may be described with reference to  FIGS. 1 to 3 , and the inverting amplifier may be described with reference to  FIGS. 4 and 5 . 
         [0045]    The semiconductor chip  200  may be an application specific integrated circuit (ASIC). A non-inverting amplifier  210  may include an input terminal  220 , a capacitor  230 , a first resistor  240 , a second resistor  250 , and an output terminal  260 . The input terminal  220  may be configured to receive a piezoresistive signal and a capacitance signal from the audio detection module  100 . Additionally, the input terminal  220  may include a non-inverting input terminal  223  and an inverting input terminal  225 . 
         [0046]    The non-inverting input terminal  223  may be connected to the output pad  153  of the audio detection module  100  and may be configured to receive a capacitance signal through the output pad  153 . The non-inverting input terminal  223  may be connected to the capacitor  230 . One side (e.g., a first side) of the capacitor  230  may be connected to the output pad  153 , and the other side of the capacitor  230  may be connected to the non-inverting input terminal  223 . The inverting input terminal  225  may be connected to the first resistor  240 . One side (e.g., a first side) of the first resistor  240  may be connected to ground, and the other side of the first resistor  240  may be connected to the first pad  151  that may be connected to the piezoresistive element  140 . 
         [0047]    The second resistor  250  may be connected to the inverting input terminal  225  and the output terminal  260 . Additionally, one side (e.g., a first side) of the second resistor  250  may be connected to the second pad  155  that may be connected to the piezoresistive element  140  and may be connected to the inverting input terminal  225  through the second pad  155 . The other side (e.g., a second side) of the second resistor  250  may be connected to the output terminal  260 . 
         [0048]    As shown in  FIG. 3 , when the audio  300  is introduced from the exterior, the piezoresistive element  140  may be configured to perform a function of a variable resistor  270 . In other words, since the piezoresistive element  140  may be connected to the first resistor  240  and the second resistor  250  through the first pad  151  and the second pad  155 , the piezoresistive element  140  may exhibit an effect as if it is inserted between the first resistor  240  and the second resistor  250 . Accordingly, when the audio  300  is introduced from the exterior, a piezoresistive signal may change to reflect an amplifying rate of the non-inverting amplifier  210 . In other words, an amplifying rate may be determined by the first resistor  240 , the second resistor  250 , and the piezoresistive element  140 . For example, an amplifying rate may be determined by Equation 1. 
         [0000]    
       
         
           
             
               
                 
                   Gain 
                   = 
                   
                     1 
                     + 
                     
                       
                         
                           R 
                            
                           
                               
                           
                            
                           2 
                         
                         + 
                         
                           Δ 
                            
                           
                               
                           
                            
                           R 
                         
                       
                       
                         R 
                          
                         
                             
                         
                          
                         1 
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   1 
                 
               
             
           
         
       
     
         [0049]    wherein, Gain is an amplifying rate, R1 represents a first resistance value, R2 represents a second resistance value, and ΔR represent a piezoresistive signal. The output terminal  260  may be configured to output an amplified electrical signal. 
         [0050]      FIG. 4  is an exemplary cross-sectional view illustrating an audio detection module  100  and a circuit diagram illustrating a semiconductor chip  200  according to another exemplary embodiment. Referring to  FIG. 4 , a microphone  50  may include an audio detection module  100  and a semiconductor chip  200 . The audio detection module  100  may include a substrate  110 , an oxide film  120 , a vibration film  130 , a piezoresistive element  140 , a support layer  160 , and a fixed electrode  170 . A penetration aperture  115  may be formed in the substrate  110 . The oxide film  120  may be disposed on the substrate  110 . In other words, the oxide film  120  may be disposed at an edge portion of the audio detection module  100 . The vibration film  130  may be disposed on the substrate  110  to cover the penetration aperture  115  formed in the substrate  110 . 
         [0051]    The piezoresistive element  140  may be disposed on the oxide film  120  and may connect to a first pad  151  and a second pad  155 . A piezoresistive signal may be changed in the piezoresistive element  140  by a sound pressure of audio introduced from the exterior. The first pad  151  and the second pad  155  may be disposed on the piezoresistive element  140  and may be connected to the semiconductor chip  200 . In other words, the first pad  151  may be connected to an inverting input terminal of the semiconductor chip  200 , and the second pad  155  may be connected to a second resistor of the semiconductor chip  200 . 
         [0052]    An output pad  153  may be disposed on the vibration film  130  and may be connected to the semiconductor chip  200 . For example, the output pad  153  may be connected to an inverting input terminal of the semiconductor chip  200 . The support layer  160  may be disposed on the vibration film  130 . In particular, the support layer  160  may support the fixed electrode  170  and may be disposed at an edge portion of the vibration film  130 . The fixed electrode  170  may be formed on the support layer  160  and may be separately disposed from the vibration film  130 . The fixed electrode  170  may include a plurality of air inlets  175 . 
         [0053]    An air layer  165  may be formed between the vibration film  130  and the fixed electrode  170 . Audio introduced from the exterior stimulates the vibration film  130  thereby vibrating the vibration film  130  and a capacitance signal between the vibration film  130  and the fixed electrode  170  may be changed. The semiconductor chip  200  may be electrically connected to the audio detection module  100  and may be configured to receive an input of a signal from the audio detection module  100 . The semiconductor chip  200  may be configured to amplify and output the signal received from the audio detection module  100 . The semiconductor chip  200  may include an inverting amplifier. The inverting amplifier  410  may include an input terminal  420 , a first resistor  440 , a second resistor  450 , and an output terminal  460 . 
         [0054]    The input terminal  420  may include a non-inverting input terminal  423  and an inverting input terminal  425 . The non-inverting input terminal  423  may be connected to ground. The inverting input terminal  425  may be connected to the audio detection module  100  to receive an input of a capacitance signal from the audio detection module  100 . Specifically, the inverting input terminal  425  may be connected to the output pad  153  of the audio detection module  100  and may be configured to receive a capacitance signal through the output pad  153 . 
         [0055]    The inverting input terminal  425  may be connected to the first resistor  440 . One side of the first resistor  440  may be connected to the output pad  153  of the audio detection module  100 , and the other side of the first resistor  440  may be connected to the piezoresistive element  140  through the first pad  151 . The other side of the first resistor  440  may be connected to the inverting input terminal  425 . The second resistor  450  may be connected to the inverting input terminal  425  and the output terminal  460 . One side of the second resistor  450  may be connected to the piezoresistive element  140  through the second pad  155 , and the other side of the second resistor  450  may be connected to the output terminal  460 . The output terminal  460  may be connected to the second resistor  450 , and may be configured to amplify and output a capacitance signal and a piezoresistive signal input to the inverting amplifier  410  to an electrical signal. 
         [0056]      FIG. 5  is an exemplary diagram illustrating a situation in which audio is introduced into a microphone  50  according to another exemplary embodiment of the present invention. Referring to  FIG. 5 , the audio detection module  100  may be configured to inject audio  300  generated at the exterior, and the vibration film  130  may be configured to vibrate by the audio  300 . Accordingly, a gap between the fixed electrode  170  and the vibration film  130  may be changed and a capacitance signal between the vibration film  130  and the fixed electrode  170  may be changed. The capacitance signal may be input to the non-inverting input terminal  423  of the inverting amplifier  410  through the output pad  153 . 
         [0057]    When a sound pressure is applied by the audio  300  introduced from the exterior, the piezoresistive element  140  of the audio detection module  100  may be configured to generate a piezoresistive signal. The piezoresistive element  140  may be connected to the first resistor  440  through the first pad  151  and may be connected to the second resistor  450  through the second pad  155 , thereby exhibiting an effect that it is inserted between the first resistor  440  and the second resistor  450 . Further, since a piezoresistive signal may be changed by a sound pressure from the exterior, the piezoresistive element  140  may perform a function of a variable resistor  470 . 
         [0058]    When using the inverting amplifier  410 , an amplifying rate may be determined by the first resistor  440 , the second resistor  450 , and the piezoresistive element  140 . In other words, an amplifying rate may be determined by Equation 2. 
         [0000]    
       
         
           
             
               
                 
                   Gain 
                   = 
                   
                     - 
                     
                       
                         
                           R 
                            
                           
                               
                           
                            
                           2 
                         
                         + 
                         
                           Δ 
                            
                           
                               
                           
                            
                           R 
                         
                       
                       
                         R 
                          
                         
                             
                         
                          
                         1 
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   2 
                 
               
             
           
         
       
     
         [0059]    wherein, Gain is an amplifying rate, R1 represents a first resistance value, R2 represents a second resistance value, and ΔR represent a piezoresistive signal. 
         [0060]    According to an exemplary embodiment of the present invention, while maintaining a hybrid form that may combine a capacitance method and a piezoelectric method for an input sound pressure, sensitivity may be improved. Since the microphone  50  may process a capacitance signal and a piezoresistive signal without an additional circuit, increase of an additional area and power consumption according to an increase in size of the semiconductor chip  200  may be prevented. 
         [0061]    While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention 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.