Method for manufacturing capacitive micromachined ultrasonic transducer and apparatus configured to obtain subject information using the capacitive micromachined ultrasonic transducer

Abstract

There is provided a method for manufacturing a capacitive micromachined ultrasonic transducer. In this method, a first insulating layer and a vibrating membrane are bonded by heat treatment and a second insulating layer is formed by thermal oxidation in a single heating step, with a cavity provided in the transducer communicating with the outside of the transducer through a communication portion.

What is claimed is: 
     
         1 . A method for manufacturing a capacitive micromachined ultrasonic transducer having a vibrating membrane, a substrate, and a vibrating-membrane-supporting member configured to support the vibrating membrane to form a cavity between the substrate and the vibrating membrane, comprising steps of:
 forming a first insulating layer on either side of the substrate, the first insulating layer patterned to serve as the vibrating-membrane-supporting member;   overlaying the vibrating membrane on the patterned first insulating layer;   bonding the first insulating layer and the vibrating membrane by heat treatment after overlaying the vibrating membrane on the patterned first insulating layer; and   forming a second insulating layer on a surface of the substrate or the vibrating membrane exposed to the cavity by introducing a gas into the cavity through a communication portion that allows the cavity to communicate with an outside of the capacitive micromachined ultrasonic transducer and subsequent thermal oxidation in an atmosphere containing the gas, after overlaying the vibrating membrane on the patterned first insulating layer, wherein   with the cavity communicating with the outside of the capacitive micromachined ultrasonic transducer through the communication portion, the first insulating layer and the vibrating membrane are bonded by heat treatment and the second insulating layer is formed by thermal oxidation in a single heating step.   
     
     
         2 . The method for manufacturing a capacitive micromachined ultrasonic transducer according to  claim 1 , wherein
 the patterned first insulating layer is formed together with a communication passage and configured to serve as a component of the communication portion.   
     
     
         3 . The method for manufacturing a capacitive micromachined ultrasonic transducer according to  claim 2 , wherein
 the communication portion consists only of the communication passage.   
     
     
         4 . The method for manufacturing a capacitive micromachined ultrasonic transducer according to  claim 1 , further comprising a step of:
 providing the substrate or the vibrating membrane with a communication hole configured to function as a component of the communication portion.   
     
     
         5 . The method for manufacturing a capacitive micromachined ultrasonic transducer according to  claim 1 , further comprising a step of:
 forming a blocking layer configured to prevent the cavity from communicating with the outside of the capacitive micromachined ultrasonic transducer after forming the second insulating layer.   
     
     
         6 . The method for manufacturing a capacitive micromachined ultrasonic transducer according to  claim 1 , wherein
 the substrate is a silicon-containing substrate, and the second insulating layer contains a silicon-oxide-containing layer formed by thermal oxidation of the silicon-containing substrate.   
     
     
         7 . The method for manufacturing a capacitive micromachined ultrasonic transducer according to  claim 1 , wherein
 the vibrating membrane is a silicon-containing film, and the second insulating layer contains a silicon-oxide-containing layer formed by thermal oxidation of the silicon-containing film.   
     
     
         8 . The method for manufacturing a capacitive micromachined ultrasonic transducer according to  claim 1 , wherein
 the patterned first insulating layer is formed by forming the first insulating layer on either side of the substrate by thermal oxidation in an atmosphere containing oxygen and subsequent etching on the first insulating layer.   
     
     
         9 . An apparatus configured to obtain subject information, comprising:
 a capacitive micromachined ultrasonic transducer produced by the method for manufacturing a capacitive micromachined ultrasonic transducer according to  claim 1 , and   a processing unit configured to obtain subject information using an electric signal output from the capacitive micromachined ultrasonic transducer, wherein   the capacitive micromachined ultrasonic transducer receives an acoustic wave from the subject and transduces the acoustic wave into the electric signal.