Broadband ultrasound transducers and related methods

A method to manufacture an ultrasonic transducer, the method comprising:

• providing a first substrate;
• patterning a first membrane on the first substrate, the first membrane having a first resonant frequency;
• patterning a second membrane on the first substrate, the second membrane having a second resonant frequency different from the first resonant frequency;
• and
• patterning a third membrane on the first substrate opposite the second membrane relative to the first membrane and along an axis passing through the first membrane, having a same shape and same dimensions as the second membrane, and having the second resonant frequency;
• providing a second substrate having electrical bond pads, wherein the second substrate is bonded to the first substrate, and the electrical bond pads are coupled to electrodes of the first, second and third membranes to provide electrical connections between the ultrasonic transducer and other circuitry coupled to the second substrate;
• wherein, the first, second and third membranes include:
• a top electrode;
• a piezoelectric layer having opposite first and second surfaces, in which the first surface of the piezoelectric layer is disposed on the top electrode;
• a bottom electrode having opposite first and second surfaces, in which the first surface of the bottom electrode is disposed on the second surface of the piezoelectric layer, the second surface of the bottom electrode is disposed on the first substrate, and the bottom electrode is patterned from a film including titanium and platinum, and is a ground electrode for the top electrode;
• and
• an insulator having opposite first and second surfaces, in which the first surface of the insulator is disposed on the second surface of the bottom electrode, and the second surface of the insulator is disposed on the first substrate.

A method for transmitting ultrasonic waves, the method comprising:

• electrically stimulating a first membrane of an ultrasonic transducer, causing the first membrane to transmit a first wave at a first frequency;
• and
• electrically stimulating a second membrane of the ultrasonic transducer, causing the second membrane to transmit a second wave at a second frequency, wherein the second frequency is different from the first frequency;
• electrically stimulating a third membrane of the ultrasonic transducer, causing the third membrane to transmit a third wave at the second frequency, wherein the third membrane is patterned opposite the second membrane relative to the first membrane and along an axis passing through the first membrane, and the third membrane has a same shape and same dimensions as the second membrane;
• wherein, the ultrasonic transducer includes a first substrate, and the first, second and third membranes are patterned on the first substrate and include:
• a top electrode;
• a piezoelectric layer having opposite first and second surfaces, in which the first surface of the piezoelectric layer is disposed on the top electrode;
• a bottom electrode having opposite first and second surfaces, in which the first surface of the bottom electrode is disposed on the second surface of the piezoelectric layer, the second surface of the bottom electrode is disposed on the first substrate, and the bottom electrode is patterned from a film including titanium and platinum, and is a ground electrode for the top electrode;
• and
• an insulator having opposite first and second surfaces, in which the first surface of the insulator is disposed on the second surface of the bottom electrode, and the second surface of the insulator is disposed on the first substrate;
• and
• wherein the ultrasonic transducer includes a second substrate having electrical bond pads, wherein the second substrate is bonded to the first substrate, and the electrical bond pads are coupled to electrodes of the first, second and third membranes to provide electrical connections between the ultrasonic transducer and other circuitry coupled to the second substrate.