Title :
A Miniature Capacitive Ultrasonic Imager Array
Author :
Cheng, Xiaoyang ; Chen, Jingkuang ; Li, Chuan ; Liu, Jian-Hung ; Shen, I-Ming ; Li, Pai-Chi
Author_Institution :
Dept. of Electr. & Comput. Eng., Univ. of New Mexico, Albuquerque, NM
fDate :
5/1/2009 12:00:00 AM
Abstract :
This paper describes the development of a miniature capacitive micromachined ultrasonic transducer (CMUT) array suitable for minimally invasive medical imaging and diagnosis. In contrast to conventional laboratory-scale CMUT platforms, which are generally integrated on a silicon substrate thicker than 550 mum, this imager array is integrated on a probe shaped silicon substrate with a typical shank dimension of 60 mum(width) times 40 mum(thickness) times 4-10 mm(length) for 1-D arrays, and 0.4-2.3 mm(width) times 100 mum(thickness) times 6-12 mm(length) for 2-D arrays. Such miniature CMUT arrays are suitable for implantation into tissue through a fine incision or by being placed inside an organ for close-range imaging. In a close-range diagnosis made possible by using such miniature CMUT arrays, ultrasound of a higher frequency can be used and the conflict associated with the penetration depth and image resolution can be resolved. This imager array was fabricated using a two-layer polysilicon surface micromachining process followed by a double-sided deep silicon etching for substrate shaping. The total mask count was eight. The central frequency of ultrasound transmitted by a circular 46 mum-diameter transducer was 3.8 MHz, while its fractional bandwidth was 116% in water. A simple transducer-fluid model was used to predict the acoustic characteristics of this device in water. Preliminary B-mode imaging using a 21-element 1-D array was demonstrated.
Keywords :
biological tissues; biomedical transducers; biomedical ultrasonics; capacitive sensors; etching; image resolution; image sensors; micromachining; microsensors; ultrasonic transducer arrays; 21-element 1-D array; CMUT array; Si; capacitive micromachined ultrasonic transducer; double-sided deep silicon etching; frequency 3.8 MHz; image resolution; miniature capacitive ultrasonic imager array; silicon substrate; size 46 mum; tissue implantation; transducer-fluid model; two-layer polysilicon surface micromachining process; ultrasonic B-mode imaging; Biomedical imaging; Frequency; Image resolution; Laboratories; Minimally invasive surgery; Probes; Silicon; Ultrasonic imaging; Ultrasonic transducer arrays; Ultrasonic transducers; Capacitive micromachined ultrasonic transducer (CMUT); medical imaging; microelectromechanical systems (MEMS); ultrasonic transducer;
Journal_Title :
Sensors Journal, IEEE
DOI :
10.1109/JSEN.2009.2013502