Low-temperature micromachined cMUTs with fully-integrated analogue front-end electronics

The powerful combination of silicon micromachining and integrated-circuit (IC) technology will lead to the realisation of fully-integrated Capacitive Micromachined Ultrasonic Transducer (cMUT) arrays plus signal conditioning electronics on the same substrate. For imaging applications, this functionality permits low-parasitic connectivity to individual elements within dense 2D arrays. This is vital for cMUT devices, in terms of maximising signal-to-noise ratio (SNR), sensitivity and bandwidth, but critically for arrays in achieving high yield and manufacturability, and ultimately low cost. This paper presents the successful demonstration of this level of integration using "post-processing" microfabrication techniques, which allow the independent optimisation of both cMUT and electronics performance. The approach to optimisation of the design and fabrication, of both cMUT and electronics, will be presented including measured and simulated results for fully integrated cMUT devices with their associated analogue front-end amplifiers.