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  Capacitive ultrasonic transducer and endo cavity ultrasonic diagnosis system using the sameUSPTO Application #: 20070299345Title: 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. (end of abstract) Agent: Scully Scott Murphy & Presser, PC - Garden City, NY, US Inventors: Hideo Adachi, Katsuhiro Wakabayashi, Akiko Mizunuma, Atsushi Osawa, Tatsuo Kaimai, Shinji Yasunaga, Kiyoshi Nemoto, Miyuki Murakami, Kousei Tamiya, Yu Kondo USPTO Applicaton #: 20070299345 - Class: 600459000 (USPTO) Related Patent Categories: Surgery, Diagnostic Testing, Detecting Nuclear, Electromagnetic, Or Ultrasonic Radiation, Ultrasonic, Structure Of Transducer Or Probe Assembly The Patent Description & Claims data below is from USPTO Patent Application 20070299345. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates to a capacitive micromachined ultrasonic transducer (c-MUT) produced using silicon process and an endoscopic ultrasonic diagnostic system including c-MUT. BACKGROUND ART [0002] An ultrasonic diagnosis method for transmitting an ultrasound to an endo cavity wall and diagnosing by imaging the body tissue using an echo signal from body tissue targets has become widely used. One of the equipment used for the ultrasonic diagnosis method is an ultrasonic endoscope. The ultrasonic endoscope is equipped with an ultrasonic transducer at the head part of an insertion tube which is for inserting into an endo cavity. The transducer is configured to transmit an ultrasound into an endo cavity by converting an electric signal into an ultrasound, receive an ultrasound which is reflected from the body tissue and convert it into an electric signal. [0003] A conventional ultrasonic transducer has been using a ceramic lead zirconate titanate (PZT) as a piezoelectric element for converting an electric signal into an ultrasound. However, attention is recently focused on a capacitive micromachined ultrasonic transducer (abbreviated as "c-MUT" hereinafter) produced by processing a silicon semiconductor substrate by means of a silicon micromachining technique. This is one of devices generally called a micromachine (i.e., Micro Electro-Mechanical System: MEMS). [0004] A MEMS device is formed on a silicon substrate or glass substrate as a miniature structure which is an electrically and mechanically combined component sometimes accompanied with driving integral circuit, such as a transducer for outputting a mechanical force, a driving mechanism for driving the transducer and a semiconductor integrated circuit for controlling the driving mechanism. The basic characteristic of the MEMS device lies in integrating the transducer, which is configured as a mechanical structure, of a part of the device, and driving the transducer electrically by applying a Coulomb attraction between electrodes. [0005] Meanwhile, a non-patent document 1 has disclosed a c-MUT as shown in FIG. 1. FIG. 1(a) shows the top face of two sets of a single-dimensional c-MUT array consisting of 64 pieces of elements; FIG. 1(b) shows a singularized one piece of c-MUT element equipped with dummy neighbors; and FIG. 1(c) shows an enlarged diagram of a c-MUT element structured by parallelly connected by 8.times.160 pieces of cells. [0006] The c-MUT element 150 comprises a plurality of cells 151, upper electrodes 152 equipped on the upper parts of individual cells, ground electrodes 153, dummy neighbors 155 and trenches 156. The upper electrodes 152 are connected to one another and they are connected to the electrodes 153 on the ends. The dummy neighbors 155 are for preventing a crosstalk with the adjacent elements. A trench 156 is equipped between the electrode 153 and dummy neighbor 155. [0007] The upper electrodes are supported by a membrane. Bottom electrodes (not shown herein) are equipped at a position opposite to the upper electrodes 152 within the cells, and there is a cavity between the bottom electrode and the membrane. [0008] As a voltage is applied to the upper and bottom electrodes of the element, each cell is simultaneously driven to vibrate concurrently in the same phase, thereby transmitting an ultrasound. [0009] The non-patent document 1 documents a finding that a Lamb wave (i.e., A0 mode) and a Stoneley wave (i.e., a boundary wave) transmitting between the solid phase and fluid phase give a great influence on a crosstalk between the elements. [0010] FIG. 2 shows a vibrational wave occurring in a membrane 160 in the case of generating an ultrasound by using the c-MUT shown in FIG. 1. FIG. 2 is a cross-sectional diagram of the element shown in FIG. 1. If there are distinctive end parts 161 by equipping the trenches 156 on both ends, as in the element 150, a standing wave 162 is generated with the end parts 161 as nodes. [0011] That is, a standing wave is generated between a pair of walls existing apart from each other by a frequency which is determined by the distance between the walls and by the transverse sonic velocity of a material (i.e., silicon in the configuration of FIG. 2) filling therebetween. Considering a pair of adjacent trenches, an vibrational wave excited on a membrane is first transmitted along the surface of the membrane as a Lamb wave or Stoneley wave. Then an ultrasound, that is the vibrational wave, is multiply reflected by the right side wall on the left side trench and left side wall of the right side trench, becoming possibly a transverse standing wave. The transverse standing wave becomes an vibrational wave with a base having a frequency component of which a distance L is 1/2.lamda. overlapped with a high-order standing wave of the base. Therefore, the existence of such a pair of walls generates a standing wave. The standing wave 162 is possible to become a noise component in an transducing of an ultrasound. [0012] Non-patent document 1: Xuecheng Jin, et al (3), "Characterization of One-Dimensional Capacitive Micromachined Ultrasonic Immersion Transducer Arrays", in "IEEE Transactions on Ultrasonic, Ferroelectrics and Frequency Control", Vol. 48, NO. 3, P 750-760, May 2001 [0013] Non-patent document 2: A. G. Bashford, et al (2), "Micromachined Ultrasonic Capacitance Transducers for Immersion Applications", in "IEEE Transactions on Ultrasonic, Ferroelectrics and Frequency Control", Vol. 45, No. 2, March (1998), P. 367-375 DISCLOSURE OF INVENTION [0014] A capacitive ultrasonic transducer (c-MUT) according to the present invention is one 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 and a conductive film is formed in the trench. [0015] A production method for a 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 according to the present invention comprises: 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. [0016] An endo cavity ultrasonic endoscopic diagnosis system according to the present invention comprises: an ultrasonic endoscopic scope equipped with a c-MUT for transmitting and receiving an ultrasound; a transducer state discernment unit for discerning such a wrong state of the c-MUT as an electrical short; 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. [0017] An endo cavity ultrasonic endoscopic diagnosis system according to the present invention comprises: an ultrasonic endoscope equipped with a 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 information sensed by the c-MUT; a storage control unit for having the storage unit, which corresponds to a discernment result, store the 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 information among the 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. [0018] A noise elimination apparatus for eliminating a noise component from information sensed by a 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 according to the present invention comprises: a first storage unit for storing the first 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 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 information and first information. BRIEF DESCRIPTION OF DRAWINGS [0019] FIG. 1 is a diagram showing a conventional c-MUT; [0020] FIG. 2 is a diagram showing a situation of generating a standing wave in a membrane in the case of using the c-MUT shown in FIG. 1; Continue reading... Full patent description for Capacitive ultrasonic transducer and endo cavity ultrasonic diagnosis system using the same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Capacitive ultrasonic transducer and endo cavity ultrasonic diagnosis system using the same patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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