Segmented getter openings for micromachined ultrasound transducer devices
An ultrasonic transducer device includes a bottom electrode layer of a transducer cavity disposed over a substrate, and a plurality of vias that electrically connect the bottom electrode layer with the substrate. A bottom cavity layer is disposed over the bottom electrode layer, and one or more openings are formed in the bottom cavity layer so as to expose a region of the bottom electrode layer, wherein locations of the one or more openings are segments that are disposed proximate an outer perimeter of the transducer cavity and substantially correspond to locations where the plurality of vias are not disposed directly beneath.
1 . An ultrasonic transducer device, comprising:
a substrate;
a transducer cavity disposed over the substrate, wherein a bottom electrode layer of the transducer cavity is disposed over the substrate;
a plurality of vias that electrically connect the bottom electrode layer with the substrate;
a bottom cavity layer disposed over the bottom electrode layer; and
one or more openings formed in the bottom cavity layer so as to expose a region of the bottom electrode layer to the transducer cavity,
wherein a first portion of the bottom electrode layer comprises a transducer bottom electrode and a second portion of the bottom electrode layer comprises a bypass metal structure that is electrically isolated from the transducer bottom electrode,
a first portion of the plurality of vias connect to the bypass metal structure and are disposed in locations directly beneath a footprint of the transducer cavity in a plan view, and
a a second portion of the plurality of vias which has a larger number of vias than the first portion of the plurality of vias are not disposed directly beneath locations of the one or more openings in the plan view.
2 . The ultrasonic transducer device of claim 1 , further comprising a transducer membrane that seals the transducer cavity,
wherein the exposed region of the bottom electrode layer serves as a getter material to consume one or more gaseous materials present in the transducer cavity during bonding of the transducer membrane.
3 . The ultrasonic transducer device of claim 2 , wherein the bottom electrode layer comprises tungsten (W).
4 . The ultrasonic transducer device of claim 3 ,
wherein the bottom cavity layer comprises an electrically insulating layer.
5 . The ultrasonic transducer device of claim 3 ,
wherein the bottom cavity layer comprises a silicon oxide (SiO2) and an aluminum oxide (Al2O3) layer.
6 . The ultrasonic transducer device of claim 1 ,
wherein the one or more openings formed in the bottom cavity layer comprise segments that are disposed proximate an outer perimeter of the transducer cavity,
wherein the segments are configure to expose portions of the bypass metal structure.
7 . The ultrasonic transducer device of claim 6 ,
wherein the segments are spaced apart from one another about the outer perimeter of the transducer cavity.
8 . An ultrasonic transducer device, comprising:
a substrate;
a transducer cavity disposed over the substrate, wherein a bottom electrode layer of the transducer cavity is disposed over the substrate;
a plurality of vias that electrically connect the bottom electrode layer with the substrate;
a bottom cavity layer disposed over the bottom electrode layer; and
one or more openings formed in the bottom cavity layer so as to expose a region of the bottom electrode layer to the transducer cavity;
wherein the plurality of vias are disposed in locations beneath a footprint of the transducer cavity in a plan view, the locations also being offset from directly beneath a footprint of the one or more opening in the plan view.
9 . An ultrasonic transducer device, comprising:
a substrate;
a transducer cavity disposed over the substrate, wherein a bottom electrode layer of the transducer cavity is disposed over the substrate, and
wherein the bottom electrode layer comprises:
a first portion that serves as a bypass metal structure that is electrionally isolated from the transducer bottom electrode;
a bottom cavity layer disposed over the bottom electrode layer;
a plurality of openings formed in the bottom cavity layer so as to expose regions of the bypass metal structure, the plurality of openings comprising segments disposed proximate an outer perimeter of the transducer cavity, and the segments being spaced apart from one another about the outer perimeter of the transducer cavity; and
a transducer membrane that seals the transducer cavity,
wherein the exposed regions of the bypass metal structure serve as a getter material to consume one or more gaseous materials present in the transducer cavity during bonding of the transducer membrane.