Micro-fabricated devices having a suspended membrane or plate structure
The invention relates to micro-fabricated devices having a suspended membrane or plate structure and micro-fabrication techniques for making such devices. A substrate defines a cavity passing through the substrate, and the cavity defines a first opening. An intermediate portion is disposed over the substrate and defines a second opening. The second opening is larger in size than the first opening, and the dimensions of the second opening are controlled according to a parameter associated with performance of the device. A membrane is positioned adjacent the second opening.
1. A micro-fabricated fluidic sensing device comprising:
a substrate defining a first cavity passing through the substrate, the cavity defining a first opening;
an intermediate portion disposed over the substrate defining a second opening that is larger in size than the first opening, wherein the dimensions of the second opening are determined according to a performance parameter of the sensing device; and
a membrane sensitive to properties of a fluid interacting with the membrane positioned adjacent the second opening.
2. The device of claim 1 , wherein the dimensions of the second opening comprise at least one of a length dimension, a width dimension, a height dimension, or any combination thereof.
3. The device of claim 1 , wherein the intermediate portion is formed of an intermediate layer disposed on the substrate material.
4. The device of claim 3 , wherein the intermediate layer comprises an oxide material.
5. The device of claim 1 , wherein the membrane comprises the intermediate portion.
6. The device of claim 1 , wherein the membrane comprises at least one of silicon, polysilicon, silicon nitride, aluminum nitride, zinc oxide, aluminum, molybdenum, copper, gold, titanium, parylene, PMMA, SU-8, or any combination thereof.
7. The device of claim 1 , wherein the membrane comprises two or more layers comprising one or more membrane materials.
8. The device of claim 1 , wherein the size of the second opening is greater than the size of the first opening by an amount greater than about a thickness of the intermediate portion.
9. The device of claim 1 , wherein the second opening is larger in size than the first opening by an amount greater than about two times a thickness of the intermediate portion.
10. The device of claim 1 , wherein the second opening is larger than the first opening by an amount between about 5 and about 10 micrometers.
11. The device of claim 1 , wherein the second opening is larger than the first opening by an amount between about 10 micrometers and about 30 micrometers.
12. The device of claim 1 , wherein the intermediate portion has a thickness of about 1 micrometer.
13. The device of claim 1 , wherein the size of the membrane is determined based at least in part on the size of the second opening.
14. The device of claim 1 , wherein the membrane cooperates with the second opening to form a boundary associated with a boundary condition and the size of the membrane is determined based at least in part on the boundary condition.
15. The device of claim 1 , wherein the membrane comprises a plate structure.
16. The device of claim 1 , further comprising:
an electroactive layer disposed on a surface of the membrane; and
a set of electrodes disposed on a surface of the electroactive layer.
17. The device of claim 16 , wherein the electroactive layer comprises a piezoelectric material.
18. The device of claim 1 , wherein the cavity cooperates with the membrane to form a fluid path.
19. The device of claim 1 , wherein the parameter of the device comprises at least one of sensitivity, accuracy, operational lifetime, or any combination thereof.
20. The device of claim 1 , wherein the parameter of the device comprises frequency response.
21. The device of claim 15 , wherein the sensing device is a flexural plate wave device.
22. A micro-fabricated fluidic resonant sensing device comprising:
a substrate defining a first cavity passing through the substrate, the cavity defining a first opening;
an intermediate layer disposed over the substrate defining a second opening that is larger in size than the first opening, wherein a thickness of the intermediate layer determines a height of the second opening; and
a membrane sensitive to properties of a fluid interacting with the membrane positioned adjacent the second opening.