Capacitive Ultrasonic Transducer and Endo Cavity Ultrasonic Diagnosis System Using the Same

Abstract

A capacitive ultrasonic transducer (c-MUT) comprising a silicon substrate and a transducer element which comprises transducer cells, each of which is constituted by a first electrode equipped on the top surface of the silicon substrate, a second electrode placed opposite to the first electrode with a predetermined gap therefrom and a membrane for supporting the second electrode, wherein a trench is equipped between the adjacent transducers and a conductive film is formed in the trench.

1 . A capacitive ultrasonic transducer (c-MUT) comprising a silicon substrate and a transducer element which comprises transducer cells, each of which is constituted by a first electrode equipped on the top surface of the silicon substrate, a second electrode placed opposite to the first electrode with a predetermined gap therefrom and a membrane for supporting the second electrode, wherein 
 a trench is equipped between the adjacent transducer elements, a conductive film is formed in the trench, and the c-MUT further comprises a flexible printed circuit board joined to the back surface of the silicon substrate by way of electrode pads placed on the back surface of the silicon substrate respectively for the individual transducer elements.    
     
     
         2 . (canceled)  
     
     
         3 . The c-MUT according to  claim 1 , wherein 
 a bottom of the trench equipped between transducer units constituted by the transducer elements, a plurality of which is one-dimensionally arrayed, reaches at a surface of the flexible printed circuit by penetrating the silicon substrate and electrode pad.    
     
     
         4 . The c-MUT according to  claim 1 , wherein 
 the conductive film is formed on a trench interior wall and bottom of the trench and the conductive film formed on the bottom is joined to an Ohmic contact zone which is featured on the silicon substrate surface.    
     
     
         5 . The c-MUT according to  claim 1 , wherein 
 the trench is filled with an ultrasonic attenuation material.    
     
     
         6 . The c-MUT according to  claim 5 , wherein 
 the ultrasonic attenuation material is a composite resin mixing a fine tungsten powder with a resin of which the main component is at least either one of epoxy resin, silicone resin, or urethane resin.    
     
     
         7 . The c-MUT according to  claim 1 , wherein 
 a cross-sectional form of the trench is a taper form in which a trench width is decreased with the depth of the trench.    
     
     
         8 . The c-MUT according to  claim 1 , wherein 
 the inside wall of the trench is featured with a surface irregularity of no less than an order of a sub-micrometer.    
     
     
         9 . The c-MUT according to  claim 3 , wherein 
 the penetrating trench surface is covered with the conductive film and is connected to a ground wire equipped on the flexible printed circuit by way of a conductive adhesive, ball bump or anisotropic dielectrics film.    
     
     
         10 . The c-MUT according to  claim 1 , wherein 
 the trench has a curve form or saw-tooth form, at least other than a straight line form when viewing the transducer element from the above.    
     
     
         11 . A production method for a capacitive ultrasonic transducer (c-MUT) comprising a silicon substrate and a transducer element which comprises transducer cells, each of which is constituted by a first electrode equipped on the top surface of the silicon substrate, a second electrode placed opposite to the first electrode with a predetermined gap therefrom and a membrane for supporting the second electrode, comprising: 
 a trench forming process for equipping in between the adjacent transducer elements with a trench; and    a conductivity forming process for forming a third electrode on a bottom of the trench by making it conductive.    
     
     
         12 . The production method for a c-MUT according to  claim 11 , wherein 
 the conductivity forming process applies an ion implantation or chemical vapor deposition method, followed by applying an expansion process, thereby forming the third electrode.    
     
     
         13 . The production method for a c-MUT according to  claim 11 , wherein 
 the conductivity forming process forms the third electrode by a physical vapor deposition.    
     
     
         14 . The production method for a c-MUT according to  claim 11 , further comprising 
 an ultrasonic attenuation material filling process for filling the trench, in which the third electrode is formed, with an ultrasonic attenuation material.    
     
     
         15 . The production method for a c-MUT according to  claim 14 , further comprising 
 a first cutting process for cutting the trench filled with the ultrasonic attenuation material.    
     
     
         16 . The production method for a c-MUT according to  claim 11 , comprising 
 a second cutting process for cutting the trench by cutting through the silicon substrate and electrode pad and reaching at a surface of the flexible printed circuit.    
     
     
         17 . The production method for a c-MUT according to  claim 15 , wherein 
 the first cutting process cuts by using a laser beam.    
     
     
         18 . The production method for a c-MUT according to  claim 16 , wherein 
 the second cutting process cuts by using a laser beam.    
     
     
         19 . An ultrasonic endoscope comprising the c-MUT according to  claim 1 .  
     
     
         20 . An endo cavity ultrasonic endoscopic diagnosis system, comprising: 
 an ultrasonic endoscopic scope equipped with a capacitive ultrasonic transducer (c-MUT) for transmitting and receiving an ultrasound;    a transducer state discernment unit for discerning a state of the c-MUT; and    an image construction unit for constructing an ultrasonic diagnosis image from sensed information sensed by the c-MUT according to the state discerned by the transducer state discernment unit.    
     
     
         21 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 20 , wherein 
 the transducer state discernment unit comprises a state detection unit for detecting a state of the c-MUT either of being on the outside of a body and moving within an endo cavity until reaching an inside wall of the endo cavity, or that of reaching a target diagnosis region, and    a detection information discernment unit for discerning the state based on detection information obtained from the state detection unit.    
     
     
         22 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 20 , further comprising: 
 a storage unit for storing the sensed information, and    a storage control unit for having the storage unit, which corresponds to a discernment result, store the sensed information based on the discernment result by the transducer state discernment unit.    
     
     
         23 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 21 , wherein 
 the state detection unit is an optical sensor equipped approximately in the neighborhood of the c-MUT, and    the detection information discernment unit discerns a state of the c-MUT either of being on the outside of a body, reaching an endo cavity and yet not touching an inside wall thereof, or contacting therewith based on an output of the optical sensor.    
     
     
         24 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 21 , wherein 
 the state detection unit is a pressure sensor equipped approximately in the neighborhood of the c-MUT, and    the detection information discernment unit discerns a state of the c-MUT either of being on the outside of a body, reaching an endo cavity and yet not touching an inside wall thereof, or contacting therewith based on an output of the pressure sensor.    
     
     
         25 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 21 , wherein 
 the state detection unit generates the detection information corresponding to an electric signal expressing the sensed information, and    detection information discernment unit discerns a state of the c-MUT either of being on the outside of a body, reaching an endo cavity and yet not touching an inside wall thereof, or contacting therewith based on the state detection information.    
     
     
         26 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 25 , wherein 
 a state detection unit is a filter circuit letting the electric signal pass if a frequency thereof is equal to or less than a predefined threshold value.    
     
     
         27 . An endo cavity ultrasonic endoscopic diagnosis system, comprising: 
 an ultrasonic endoscope equipped with a capacitive ultrasonic transducer (c-MUT) for transmitting and receiving an ultrasound;    a transducer state discernment unit for discerning a state of the c-MUT;    a storage unit for storing sensed information sensed by the c-MUT;    a storage control unit for having the storage unit, which corresponds to a discernment result, store the sensed information based on the discernment result by the transducer state discernment unit;    an arithmetic operation unit for performing an arithmetic operation process based on at least one piece of the sensed information among the sensed information stored in the storage unit; and    an image construction unit for constructing an ultrasonic diagnosis image from an arithmetic operation result of the operation process performed by the arithmetic operation unit.    
     
     
         28 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 27 , wherein 
 the c-MUT is a one-dimensional or two-dimensional array type C-MUT which is constituted by a plurality of c-MUT elements and which arrays the plurality thereof on an outer circumference of a cylinder.    
     
     
         29 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 28 , wherein 
 a trench is featured in between the adjacent transducer elements.    
     
     
         30 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 29 , wherein 
 a conductive film is formed in the trench.    
     
     
         31 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 28 , further comprising 
 a radial scan control unit for making a compound ultrasonic beam, which is transmitted from the c-MUT, perform a radial scan along a circumferential direction of the cylinder.    
     
     
         32 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 31 , wherein 
 the radial scan control unit makes the compound ultrasonic beam perform a sector scan in the longitudinal axis direction of the cylinder.    
     
     
         33 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 27 , wherein 
 the arithmetic operation unit performs an arithmetic operation for calculating a sum, difference or correlation of at least two pieces of the sensed information among the sensed information stored in the storage unit.    
     
     
         34 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 27 , wherein 
 the arithmetic operation unit performs an arithmetic operation for calculating an autocorrelation from one piece of the sensed information.    
     
     
         35 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 27 , wherein 
 the transducer state discernment unit comprises a state detection unit for detecting a state of the c-MUT either of being on the outside of a body and moving within an endo cavity until reaching an inside wall of the endo cavity, or that of reaching a target diagnosis region, and    a detection information discernment unit for discerning the state based on detection information obtained from the state detection unit.    
     
     
         36 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 35 , wherein 
 the state detection unit is an optical sensor equipped approximately in the neighborhood of the c-MUT, and    the detection information discernment unit discerns a state of the c-MUT either of being on the outside of a body, reaching an endo cavity and yet not touching an inside wall thereof, or contacting therewith based on an output of the optical sensor.    
     
     
         37 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 35 , wherein 
 the state detection unit is a pressure sensor equipped approximately in the neighborhood of the c-MUT, and    the detection information discernment unit discerns a state of the c-MUT either of being on the outside of a body, reaching an endo cavity and yet not touching an inside wall thereof, or contacting therewith based on an output of the pressure sensor.    
     
     
         38 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 35 , wherein 
 the state detection unit generates the detection information corresponding to an electric signal expressing the sensed information, and    detection information discernment unit discerns a state of the c-MUT either of being on the outside of a body, reaching an endo cavity and yet not touching an inside wall thereof, or contacting therewith based on the state detection information.    
     
     
         39 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 38 , wherein 
 a state detection unit is a filter circuit letting the electric signal pass if a frequency thereof is equal to or less than a predefined threshold value.    
     
     
         40 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 27 , wherein 
 the storage control unit stores at least one piece of the sensed information among pieces thereof which is sensed in a state of the c-MUT either of being on the outside of a body, reaching an endo cavity and yet not touching an inside wall thereof, or contacting therewith.    
     
     
         41 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 27 , wherein 
 the sensed information stored in a first storage unit among the storage unit is first sensed information sensed by making the c-MUT transmit an ultrasound under a condition of the ultrasound not reflecting.    
     
     
         42 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 41 , wherein 
 the sensed information stored in a second storage unit among the storage unit is second sensed information sensed by the c-MUT transmitting and receiving an ultrasound in a state of being in an endo cavity and yet not touching an inside wall thereof, and    the arithmetic operation unit calculates a correlation or difference between the second sensed information and first sensed information.    
     
     
         43 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 41 , wherein 
 the sensed information stored in a third storage unit among the storage unit is third sensed information sensed by the c-MUT transmitting and receiving an ultrasound in a state of touching an inside wall of an endo cavity, and    the arithmetic operation unit calculates a correlation or difference between the third sensed information and first sensed information.    
     
     
         44 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 41 , wherein 
 the sensed information stored in a second storage unit among the storage unit is second sensed information sensed by the c-MUT transmitting and receiving an ultrasound in a state of being in an endo cavity and yet not touching an inside wall thereof,    the sensed information stored in a third storage unit among the storage unit is third sensed information sensed by the c-MUT transmitting and receiving an ultrasound in a state thereof touching an inside wall of an endo cavity, and    the arithmetic operation unit performs a first arithmetic operation for calculating a correlation or difference between the second sensed information and first sensed information; a second arithmetic operation for calculating a correlation or difference between the third sensed information and first sensed information; and adds the results of the first and second arithmetic operations.    
     
     
         45 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 42 , wherein 
 said ultrasonic diagnosis image is an image expressing a contour of an inside wall surface of an endo cavity.    
     
     
         46 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 43 , wherein 
 said ultrasonic diagnosis image is an image expressing a tomography of an organization of an endo cavity.    
     
     
         47 . The endo cavity ultrasonic endoscopic diagnosis system according to  claim 44 , wherein 
 said ultrasonic diagnosis image is an image expressing a contour of an inside wall surface of an endo cavity and one expressing a tomography of an organization thereof.    
     
     
         48 . A noise elimination apparatus for eliminating a noise component from sensed information sensed by a capacitive ultrasonic transducer (c-MUT) used for an endo cavity ultrasonic endoscopic diagnosis system comprising an ultrasonic endoscopic scope equipped with the c-MUT for transmitting and receiving an ultrasound, comprising: 
 a first storage unit for storing the first sensed information sensed by making the c-MUT transmit an ultrasound under a condition of the ultrasound not reflecting;    a second storage unit for storing the second sensed information sensed by the c-MUT transmitting and receiving an ultrasound under a condition thereof in a state of being in the inside of an endo cavity and yet not touching an inside wall thereof; and    an arithmetic operation unit for calculating a correlation or difference between the second sensed information and first sensed information.    
     
     
         49 . A noise elimination apparatus for eliminating a noise component from sensed information sensed by a capacitive ultrasonic transducer (c-MUT) used for an endo cavity ultrasonic endoscopic diagnosis system comprising an ultrasonic endoscopic scope equipped with the c-MUT for transmitting and receiving an ultrasound, comprising: 
 a first storage unit for storing the first sensed information sensed by making the c-MUT transmit an ultrasound under a condition of the ultrasound not reflecting;    a third storage unit for storing the third sensed information sensed by the c-MUT transmitting and receiving an ultrasound under a condition thereof touching an inside wall of an endo cavity; and    an arithmetic operation unit for calculating a correlation or difference between the third sensed information and first sensed information.    
     
     
         50 . A noise elimination method for eliminating a noise component from sensed information sensed by a capacitive ultrasonic transducer (c-MUT) used for an endo cavity ultrasonic endoscopic diagnosis system comprising an ultrasonic endoscopic scope equipped with the c-MUT for transmitting and receiving an ultrasound, comprising: 
 obtaining the first sensed information sensed by making the c-MUT transmit an ultrasound under a condition of the ultrasound not reflecting;    obtaining the second sensed information sensed by the c-MUT transmitting and receiving an ultrasound under a condition thereof in a state of being in the inside of an endo cavity and yet not touching an inside wall thereof; and    calculating a correlation or difference between the second sensed information and first sensed information.    
     
     
         51 . A noise elimination method for eliminating a noise component from sensed information sensed by a capacitive ultrasonic transducer (c-MUT) used for an endo cavity ultrasonic endoscopic diagnosis system comprising an ultrasonic endoscopic scope equipped with the c-MUT for transmitting and receiving an ultrasound, comprising: 
 obtaining the first sensed information sensed by making the c-MUT transmit an ultrasound under a condition of the ultrasound not reflecting;    obtaining the third sensed information sensed by the c-MUT transmitting and receiving an ultrasound under a condition thereof touching an inside wall of an endo cavity; and    calculating a correlation or difference between the third sensed information and first sensed information.