Micro-fabricated devices having a suspended membrane or plate structure

• US 20080121611A1
• Filed: 11/27/2006
• Published: 05/29/2008
• Est. Priority Date: 11/27/2006
• Status: Active Grant

• Current Assignee: ProterixBio, Inc.
• Original Assignee: BioScale, Inc.
• Inventors: Miller, Michael, Masters, Brett P.
• Granted Patent: US 7,999,440 B2
• Time in Patent Office: Days
• US Class Current: 216/13
• CPC Class Codes: B81B 2201/0214 Biosensors; Chemical sensors
• CPC Class Codes: B81C 1/00158 Diaphragms, membranes manufacture process for semi-permeable inorganic membranes B01D67/0039
• CPC Class Codes: G01N 2291/014 Resonance or resonant frequency
• CPC Class Codes: G01N 2291/0427 Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever
• CPC Class Codes: G01N 29/022 Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices microdevices per se B81B
• CPC Class Codes: G01N 29/222 Constructional or flow details for analysing fluids optoacoustic fluid cells G01N29/2425
• CPC Class Codes: G01N 29/24 Probes transducers for acoustic waves B06B, G10K; for measuring G01H
• CPC Class Codes: Y10T 428/13 Hollow or container type article [e.g., tube, vase, etc.]

Abstract

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.

Claims

1. A micro-fabricated 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 controlled according to a parameter of the device; and

a 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. A method for making a micro-fabricated device, the method comprising:

forming a cavity to define a first opening through a substrate material with a first removal process;

forming a second opening adjacent the first opening in a first layer disposed on the substrate material with a second process, wherein 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.

22. The method of claim 21, further comprising disposing a membrane material on the first layer.

23. The method of claim 22, wherein disposing the membrane material on the first layer further comprises disposing a portion of the membrane material on the substrate material.

24. The method of claim 23, wherein the membrane material comprises silicon nitride, polysilicon, or both.

25. The method of claim 21, wherein forming the second opening in the first layer comprises removing substantially all of the first layer from the substrate material.

26. The method of claim 21, wherein the first removal process comprises etching.

27. The method of claim 21, wherein the second process comprises etching a portion of a sacrificial layer disposed between the substrate material and the first layer.

28. The method of claim 21, wherein the second process further comprises:

depositing a sacrificial material on the substrate to approximately define the second opening;

depositing the first layer on both the sacrificial material and the substrate material; and

removing the sacrificial material with a removal process.

29. The method of claim 21, wherein forming the second opening comprises isotropically etching the first layer.

30. The method of claim 29, wherein the duration of isotropic etching is based on the desired size of the second opening and an etch rate of the isotropic etching process.

31. A method for making a micro-fabricated device, the method comprising:

forming a cavity to define a first opening through a substrate with a first removal process;

forming a second opening relative to a membrane material with a second process; and

disposing the second opening over the first opening, wherein 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.

32. The method of claim 31, wherein the second opening is formed in the membrane material by a second removal process.

33. The method of claim 32, wherein the second removal process comprises anisotropic etching of the membrane material.

34. The method of claim 32, wherein disposing the second opening over the first opening comprises bonding a surface of the membrane material to a corresponding surface of the substrate material.

35. The method of claim 34, wherein bonding a surface of the membrane material comprises anodic or fusion bonding.

36. The method of claim 31, wherein the second opening is formed by depositing a gap material on the membrane material.

37. The method of claim 36, wherein depositing a gap material comprises chemical vapor deposition, physical vapor deposition, molecular beam epitaxy, or any combination thereof.

38. The method of claim 36, wherein disposing the second opening over the first opening comprises bonding a portion of the gap material to the substrate material.

39. A micro-fabricated device comprising:

a substrate defining a cavity passing through the substrate, the cavity defining a first opening;

an intermediate portion defining a second opening adjacent the first opening;

a means for controlling the dimensions of the second opening according to a parameter associated with performance of the device; and

a membrane disposed adjacent the second opening.