Fabrication of Vacuum-Sealed Capacitive Micromachined Ultrasonic Transducer Arrays Using Glass Reflow Process

Nguyen Van Toan; Shim Hahng; Yunheub Song; Takahito Ono

doi:10.3390/mi7050076

Fabrication of Vacuum-Sealed Capacitive Micromachined Ultrasonic Transducer Arrays Using Glass Reflow Process

Micromachines (Basel). 2016 Apr 25;7(5):76. doi: 10.3390/mi7050076.

Authors

Nguyen Van Toan¹, Shim Hahng^{2

3}, Yunheub Song⁴, Takahito Ono⁵

Affiliations

¹ Microsystem Integration Center (μSIC), Tohoku University, Sendai 980-8579, Japan. nvtoan@nme.mech.tohoku.ac.jp.
² Department of Electronic Engineering, Hanyang University, Seoul 04763, Korea. yhsong2008@hanyang.ac.kr.
³ Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan. yhsong2008@hanyang.ac.kr.
⁴ Department of Electronic Engineering, Hanyang University, Seoul 04763, Korea.
⁵ Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan. hahng.shim@nme.mech.tohoku.ac.jp.

Abstract

This paper presents a process for the fabrication of vacuum-sealed capacitive micromachined ultrasonic transducer (CMUT) arrays using glass reflow and anodic bonding techniques. Silicon through-wafer interconnects have been investigated by the glass reflow process. Then, the patterned silicon-glass reflow wafer is anodically bonded to an SOI (silicon-on-insulator) wafer for the fabrication of CMUT devices. The CMUT 5 × 5 array has been successfully fabricated. The resonant frequency of the CMUT array with a one-cell radius of 100 µm and sensing gap of 3.2 µm (distance between top and bottom electrodes) is observed at 2.84 MHz. The Q factor is approximately 1300 at pressure of 0.01 Pa.

Keywords: anodic bonding; capacitive micromachined ultrasonic transducer; chemical sensing; glass reflow process; medical imaging; non-destructive measurement.