Microfabricated ultrasonic transducers and related apparatus and methods

An ultrasound device, comprising:

• a membrane comprising a silicon layer;
• a complementary metal-oxide-semiconductor (CMOS) substrate including integrated circuitry;
• an electrode;
• and
• an ultrasonic transducer cavity;
• wherein:
• the ultrasonic transducer cavity is disposed between the membrane and the electrode;
• the electrode is disposed between the ultrasonic transducer cavity and the CMOS substrate;
• the electrode is electrically coupled to the integrated circuitry;
• and
• an opening extends from the ultrasonic transducer cavity and through the silicon layer.

A method of forming an ultrasound device, wherein:

• the ultrasound device comprises
• a membrane comprising a silicon layer;
• a complementary metal-oxide-semiconductor (CMOS) substrate including integrated circuitry;
• an electrode;
• and
• an ultrasonic transducer cavity;
• wherein:
• the ultrasonic transducer cavity is disposed between the membrane and the electrode;
• the electrode is disposed between the ultrasonic transducer cavity and the CMOS substrate;
• and
• the electrode is electrically coupled to the integrated circuitry;
• and
• the method comprises forming an opening extending from the ultrasonic transducer cavity and through the silicon layer.