title: A 32 x 32 capacitive micromachined ultrasonic transducer array manufactured in standard CMOS.
abstract: As ultrasound imagers become increasingly portable and lower cost, breakthroughs in transducer technology will be needed to provide high-resolution, real-time 3-D imaging while maintaining the affordability needed for portable systems. This paper presents a 32 x 32 ultrasound array prototype, manufactured using a CMUT-in-CMOS approach whereby ultrasonic transducer elements and readout circuits are integrated on a single chip using a standard integrated circuit manufacturing process in a commercial CMOS foundry. Only blanket wet-etch and sealing steps are added to complete the MEMS devices after the CMOS process. This process typically yields better than 99% working elements per array, with less than ±1.5 dB variation in receive sensitivity among the 1024 individually addressable elements. The CMUT pulseecho frequency response is typically centered at 2.1 MHz with a -6 dB fractional bandwidth of 60%, and elements are arranged on a 250 μm hexagonal grid (less than half-wavelength pitch). Multiplexers and CMOS buffers within the array are used to make on-chip routing manageable, reduce the number of physical output leads, and drive the transducer cable. The array has been interfaced to a commercial imager as well as a set of custom transmit and receive electronics, and volumetric images of nylon fishing line targets have been produced.
authors: Sonetics Ultrasound Inc., Ann Arbor, MI, USA. dlemmerh@soneticsultrasound.com
authors: David F
authors: DF
authors: Lemmerhirt
authors: Xiaoyang
authors: X
authors: Cheng
authors: Robert
authors: R
authors: White
authors: Collin A
authors: CA
authors: Rich
authors: Man
authors: M
authors: Zhang
authors: J Brian
authors: JB
authors: Fowlkes
authors: Oliver D
authors: OD
authors: Kripfgans
mesh_terms: D017076:Computer-Aided Design; D025802:Electric Capacitance; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation*; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation*; D008904:Miniaturization; D019047:Phantoms, Imaging; D014159:Transducers; D014173:Transistors, Electronic; D014463:Ultrasonography / Q000295:instrumentation*