Bottom electrode via structures for micromachined ultrasonic transducer devices
A ultrasonic transducer device includes a transducer bottom electrode layer disposed over a substrate, and a plurality of vias that electrically connect the bottom electrode layer with the substrate, wherein substantially an entirety of the plurality of vias are disposed directly below a footprint of a transducer cavity. Alternatively, the transducer bottom electrode layer includes a first metal layer in contact with the plurality of vias and a second metal layer formed on the first metal layer, the first metal layer including a same material as the plurality of vias.
1. An ultrasonic transducer device, comprising:
a transducer structure, comprising:
a transducer membrane; and
a membrane support layer;
a transducer bottom electrode layer that is disposed over a substrate; and
vias that electrically connect the transducer bottom electrode layer to the substrate, wherein
the transducer bottom electrode layer comprises a first metal layer, that contacts to the vias and comprises a same material that completely fills the vias, and a second metal layer that overlies the first metal layer in a same pattern as the first metal layer.
2. The device of claim 1 , wherein the first metal layer comprises tungsten (W).
3. The device of claim 2 , wherein the second metal layer comprises titanium (Ti).
4. The device of claim 1 , wherein the first metal layer has a thickness of about 10-50 nanometers (nm).
5. The device of claim 1 , wherein
the membrane support layer supports the transducer membrane and is patterned such that a transducer cavity is disposed between the transducer membrane and the transducer bottom electrode layer, and
substantially all of the vias are disposed beneath the transducer cavity.
6. The device of claim 1 , wherein the ultrasonic transducer device comprises an array of transducer structures.
7. An ultrasonic transducer device, comprising: a transducer bottom electrode layerthat is disposed over a substrate; a transducer structure, comprising: a transducer membrane; and a membrane support layer that supports the transducer membrane and is patterned such that a transducer cavity is disposed between the transducer membrane and the transducer bottom electrode layer; and vias that electrically connect the transducer bottom electrode layerto the substrate, wherein substantially all of the vias are disposed beneath the transducer cavity, wherein the transducer bottom electrode layer comprises a first metal layer, that contacts the vias and comprises a same material as the vias, and a second metal layer that overlies the first metal layer in a same pattern as the first metal layer, and wherein the vias are completely filled with the same material as the first metal layer.
8. The device of claim 7 , wherein the ultrasonic transducer device comprises an array of transducer structures.