Fabrication of Micromachined Piezoelectric Diaphragm Pumps Actuated by Interdigitated Transducer Electrodes
- PDF / 512,504 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 15 Downloads / 176 Views
J5.7.1
Fabrication of Micromachined Piezoelectric Diaphragm Pumps Actuated by Interdigitated Transducer Electrodes Eunki Hong1, S.V. Krishnaswamy2, T.T. Braggins2, C.B. Freidhoff2, and S. Trolier-McKinstry1 1 Materials Research Institute and Materials Science and Engineering Dept., Pennsylvania State University, University Park, PA 2 Northrop Grumman Corporation Electronics System Sector, Baltimore MD ABSTRACT Micromachined pump structures were fabricated using surface micromachining. The structures consisted of three or five connected chambers. Sequential actuation of the diaphragms on these chambers will yield peristaltic pumping. As the actuation material, lead zirconate titanate (PZT [53/47]) thin films were employed and actuated by interdigitated transducer (IDT) electrodes. First, chambers and channels on the 4" (100) silicon wafers were defined by reactive ion etching (RIE) and thermally oxidized. The etched structures were then filled with amorphous silicon. Low temperature (silicon) oxide (LTO) and PZT films were then deposited. The LTO and PZT layers act as passive and active layers in a piezoelectric unimorph, respectively. A ZrO2 layer was employed to prevent reaction between SiO2 and PZT layers. A Cr/Au electrode was evaporated on top of the PZT layer and patterned into ring-shaped IDT electrodes. Finally, a porthole at each end of the pump structures was defined by ion milling and the whole micropump structure was released by removing the sacrificial amorphous silicon using XeF2. Completely released 500 µm diameter pump structures were fabricated. The remanent polarizations of the PZT films on released diaphragms were ~20 µC/cm2 and their coercive fields were ~50 kV/cm. 500 µm diameter diaphragms were deflected as much as 2 µm with 120 V applied. The shape and behavior of the diaphragm deflection can be explained by considering both d31 and d33 piezoelectric coefficients of the PZT films. INTRODUCTION Microelectromechanical systems (MEMS) are micromachined devices that have sensors or actuators together with signal processors. These devices are usually fabricated using integrated circuit techniques, offering the possibility of order of magnitude decreases in the sizes and costs. This is a strong driving force to miniaturize many macroscopic devices using micromachining. Mass spectrometers are universal gaseous chemical detectors. Conventional mass spectrometers are large, heavy, and expensive. In addition, a trained technical person is required to operate them [1]. Recently, several groups have successfully miniaturized chemical analysis systems for mass spectrometers [1], [2]. In order to miniaturize an entire mass spectrometer, a
J5.7.2
micromachined device to create a certain level of vacuum (~10 mTorr) in a detector chamber is an essential part [3]. In this study, peristaltic piezoelectric diaphragm pump structures were fabricated using surface micromachining. These pump structures consist of three or five connected chambers. Sequential actuations of the piezoelectric diaphragms on these chambe
Data Loading...
