Adaptive cavity thickness control for micromachined ultrasonic transducer devices

An ultrasound imaging device wherein:

• the ultrasound imaging device includes a plurality of micromachined ultrasonic transducers (MUTs) arranged into an array pattern and wherein at least one of the MUTs comprises:
• a patterned film stack disposed on first regions of a substrate, the patterned film stack includes a metal electrode layer and a bottom cavity layer formed on the metal electrode layer;
• a planarized insulation layer disposed on second regions of the substrate layer;
• A cavity formed in a membrane support layer and a chemical mechanical polishing (CMP) stop layer, the CMP stop layer comprising a top layer of the patterned film stack and the membrane support layer formed over the patterned fil stack and the planarized insulation layer;
• and
• a membrane bonded to the membrane support layer but not the cavity.