Options
2013
Presentation
Titel
New applications for ultrasound technology through CMUTs
Titel Supplements
Presentation held at EPoSS General Assembly & Annual Forum 2013, 25.-26. September, 2013, Cork, Ireland
Abstract
Ultrasonic transducers are present in everyday life in the form of level sensors, speed sensors and medical imaging systems among others. Current ultrasonic transducers are generally built using piezoelectric materials and they have proven to do a great job, however, there are applications for which it is very difficult to build piezoelectric ultrasonic transducers, and here is where the Capacitive Micro machined Ultrasonic Transducers (CMUT) come into play. Some examples for these applications are: Intra-venous Ultrasound (IVUS) [1], neural stimulation [2], harsh environment sensors [3], chemical sensors [4], gesture monitoring [5], etc. CMUTs are MEMS based devices that can generate and sense acoustic signals in the ultrasonic range. They can be built using standard CMOS compatible materials; therefore they can be easily integrated with CMOS ASICs. In addition, the use of undesired materials (Pb) can be avoided. The CMUT is essentially comprised of two electrodes facing each other, one of which is fixed and the other is movable. The two electrodes are separated by an insulating layer and an air gap. CMUTs can operate on transmit and receive mode, by converting electrical energy into acoustic energy or vice-versa through the displacement of the movable electrode. Over the last two decades, many research groups have demonstrated the capabilities of the CMUTs, and have developed the technology required for the CMUTs to work (MEMS, beam forming, drivers, read-out, etc.). However, there is still no product available neither in the European nor in the US market using this technology. Some of the issues to overcome for CMUTs are the technological capabilities required to fabricate large arrays within tight tolerances and to integrate them with CMOS back-ends. Fraunhofer IPMS can address this by making use of the in-house wafer fabrication facility where the Spatial Light Modulator (SLM) product range is being produced with similar requirements for element count and homogeneity. Furthermore, an in house developed CMOS process as well as experience on integrating MEMS on CMOS are available at IPMS. Fraunhofer IPMS started developing CMUTs in the last quarter of 2012 and managed to fabricate the first generation of CMUTs arrays which are currently being characterized. Mechanical and electrical characterization results are very promising, and we are now progressing towards obtaining the first acoustic measurements. This presentation will highlight possible applications of CMUTs and the challenges to fabricate them with high uniformity and repeatability. It will also give the current status of the activities at Fraunhofer IPMS. The institute is looking into the requirements for different applications where CMUTs can provide a definite advantage over current ultrasonic transducers. In fact, the aim is to work developing applications for customers that could benefit from this new technology.