Fabrication techniques and structures for gettering materials in ultrasonic transducer cavities
A method of forming an ultrasound transducer device includes bonding a membrane to a substrate so as to form a sealed cavity between the membrane and the substrate. An exposed surface located within the sealed cavity includes a getter material that is electrically isolated from a bottom electrode of the cavity.
1. A method of forming an ultrasound transducer device, the method comprising:
forming one or more insulating layers over a bottom electrode and over a getter material;
removing the one or more insulating layers from the getter material;
bonding a membrane to a substrate so as to form a sealed cavity therebetween, wherein a surface located within and exposed to the sealed cavity comprises the getter material.
2. The method of claim 1 , wherein the surface exposed to the sealed cavity comprises a top surface of the substrate.
3. The method of claim 1 , wherein the getter material comprises a same material as the bottom electrode.
4. The method of claim 1 , wherein the getter material comprises one or more of: titanium, zirconium, vanadium, cobalt, nickel, and alloys thereof.
5. The method of claim 1 , wherein the getter material is electrically isolated from the bottom electrode.
6. The method of claim 4 , wherein the getter material is disposed at an outer perimeter of the cavity.
7. The method of claim 4 , wherein the cavity is circular shaped and the getter material is disposed at an outer radius of the cavity.
8. The method of claim 1 , wherein the getter material is configured to remove one or more of oxygen, nitrogen, argon, or water vapor from the cavity.
9. An ultrasound transducer device, comprising:
a membrane bonded to a substrate with a sealed cavity therebetween wherein a surface located within and exposed to the sealed cavity comprises a getter material;
one or more insulating layers formed over a bottom electrode of the cavity but not present over the getter material.
10. The device of claim 9 , wherein the surface exposed to the sealed cavity comprises a top surface of the substrate.
11. The device of claim 9 , wherein the getter material comprises one or more of: titanium, zirconium, vanadium, cobalt, nickel, and alloys thereof.
12. The device of claim 9 , wherein the getter material is electrically isolated from the bottom electrode of the cavity.
13. The device of claim 11 , wherein the getter material is disposed at an outer perimeter of the cavity.
14. The device of claim 11 , wherein the cavity is circular shaped and the getter material is disposed at an outer radius of the cavity.
15. The device of claim 9 , wherein the getter material is selected to remove one or more gases including one or more of oxygen, nitrogen, argon, or water vapor.
16. The device of claim 9 , wherein the getter material comprises a same material as the bottom electrode of the cavity.