We present a novel surface micromachining process, where the top electrodes of the cMUTs (capacitive Micromachined Ultrasonic Transducer) are made-up of a combination of silicon nitride and porous polysilicon. This construction gives many advantages over the fabrication processes reported in the past. Our fabrication process contains an original method for HF etching of the sacrificial oxide layer through porous silicon, which technique seems to make the sealing process easier and improve the process quality. Also presented is a complete examination of the LPCVD low tensile silicon nitride deposition process, as the silicon nitride is used as part of the cMUT top layer. We have considered the mechanical stress, deposition rate, refractive index, etch rate and chemical composition of the LPCVD silicon nitride membranes as a function of the deposition parameters. The effects of the properties of the top membrane LPCVD silicon nitride to the cMUT characteristics are presented.
|Publication status||Published - 2003|
|MoE publication type||Not Eligible|
|Event||3rd International Workshop on Micromachined Ultrasonic Transducers - Lausanne, Switzerland|
Duration: 26 Jun 2003 → 27 Jun 2003
|Conference||3rd International Workshop on Micromachined Ultrasonic Transducers|
|Period||26/06/03 → 27/06/03|
- cMUT, Capacitive Micromachined Ultrasonic Transducers