ECHOGRAPHIC IMAGES IMPROVEMENTS WITH A CMUT PROBE

The validity of cMUT (capacitive Micromachined Ultrasonic Transducer) technology for medical imaging applications has been proved by many authors. The large bandwidth obtained with cMUT leads to improved image resolution compared to their piezoelectric counterpart. Recently, our laboratory (Aculab) has developed a flexible cMUT technology (the “Reverse” technology) able to fabricate 1D and 2D arrays for medical ultrasound imaging systems. The Reverse technology method is a new cMUT fabrication technique, based on a different approach to cavity formation that uses a combination of bulk and surface micromachining techniques. We will describe this recently developed cMUT process. The Reverse technology exhibits many advantages: interconnections pads on the rear of the die, acoustic backing directly coupled to the emitting/receiving membranes, absence of etching holes for emptying the cavities, in front of the transducer. We will discuss these advantages, together with possible process variations to further improve acoustical output and reliability. We will finally show, echographic images obtained using a probe fabricated using a Reverse cMUT technology.