Fluid paths in etchable materials

• US 20080121042A1
• Filed: 11/27/2006
• Published: 05/29/2008
• Est. Priority Date: 11/27/2006
• Status: Abandoned Application

• Current Assignee: ProterixBio, Inc.
• Original Assignee: BioScale, Inc.
• Inventors: Miller, Michael, Schmidt, Martin, Masters, Brett P.
• Application Number:
  US11/604,652
• Publication Number:
  US 20080121042A1
• Time in Patent Office: Days
• US Class Current: 73/649
• CPC Class Codes: B81B 2201/0257 Microphones or microspeakers
• CPC Class Codes: B81B 2203/0127 Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function
• CPC Class Codes: B81B 3/0078 Constitution or structural means for improving mechanical properties not provided for in B81B3/007 - B81B3/0075
• CPC Class Codes: G01H 3/04 Frequency
• CPC Class Codes: H01L 21/30608 Anisotropic liquid etching H01L21/3063 takes precedence
• CPC Class Codes: H01L 21/30655 comprising alternated and repeated etching and passivation steps, e.g. Bosch process
• CPC Class Codes: Y10T 428/8305 Miscellaneous [e.g., treated surfaces, etc.]

Abstract

The invention relates to fluid paths in etchable materials. Fluid paths are formed by forming a cavity through a substrate material with a first dry removal process to produce a first surface of the cavity. The first surface of the cavity is associated with a first roughness. The first surface of the cavity is etched with a second wet removal process to reduce the first roughness and produce a second roughness associated with the first surface of the cavity. A coating is applied to the first surface of the cavity to produce a second surface to improve wettability of the first or second surface of the cavity, reduce in size or number gas nucleation sites in the first or second surface of the cavity, reduce the amount of debris associated with the first roughness carried by the fluid flow, and/or improve hydrophilicity of the first or second surface.

Claims

1. A method of forming a portion of a fluid path in an etchable material, the method comprising:

forming a cavity with a first dry removal process in a substrate material to produce a first surface of the cavity, the first surface associated with a first roughness;

etching the first surface of the cavity with a second wet removal process to produce a second roughness associated with the first surface of the cavity; and

applying a coating to the first surface of the cavity to produce a second surface of the cavity.

2. The method of claim 1, wherein the second roughness is produced according to a desired parameter associated with the performance of a micro-fabricated device.

3. The method of claim 1, wherein the first dry removal process, the second wet removal process, or both comprise an anisotropic etching process.

4. The method of claim 1, wherein forming the cavity comprises an alternating sequence of passivation and etching.

5. The method of claim 1, wherein the fluid path forms a portion of a fluid chamber or a fluid channel.

6. The method of claim 1, wherein forming the cavity comprises forming one or more sidewalls having an angle of between about 85°

and about 95°

relative to a vertical axis defined by the cavity.

7. The method of claim 1, wherein the etchable material comprises silicon and forming the cavity comprises deep reactive ion etching.

8. The method of claim 1, wherein the second wet removal process comprises a silicon etchant.

9. The method of claim 8, wherein the silicon etchant comprises an isotropic etchant, the isotropic etchant including a mixture of water and at least one of hydrofluoric acid, nitric acid, acetic acid, or any combination thereof, or a mixture of water and at least one of nitric acid, ammonium fluoride, or any combination thereof.

10. The method of claim 8, wherein the silicon etchant comprises an anisotropic etchant, including potassium hydroxide, sodium hydroxide, ammonia hydroxide, tetramethylammonia hydroxide, hydrazine, or any combination thereof.

11. The method of claim 1, wherein a duration of etching the first surface of the cavity is between about 2 minutes and about 60 minutes.

12. The method of claim 1, wherein the cavity defines a first opening adjacent an intermediate layer disposed over the substrate material, further comprising:

etching through the intermediate layer with a third removal process to define a second opening adjacent the substrate, wherein the second opening is larger in size than the first opening.

13. The method of claim 12, wherein the third removal process comprises an isotropic etchant.

14. The method of claim 12, wherein the third layer comprises silicon oxide and the third removal process comprises a hydrofluoric acid, a buffered hydrofluoric acid, a buffered oxide etchant, or any combination thereof.

15. The method of claim 1, wherein etching the first surface of the cavity improves the wettability of the first surface of the cavity.

16. The method of claim 1, wherein etching the first surface of the cavity reduces in number or in size one or more gas nucleation sites in the first surface of the cavity.

17. The method of claim 1, wherein etching the first surface of the cavity further comprises hindering debris associated with the first roughness from engaging a membrane or a plate structure that cooperates with the cavity to form the fluid path.

18. The method of claim 1, wherein etching the first surface of the cavity further comprises improving hydrophilicity of the first surface of the cavity.

19. The method of claim 1, wherein the second surface of the cavity is more hydrophilic than the first surface of the cavity.

20. The method of claim 1, wherein the second surface of the cavity is more wettable than the first surface of the cavity.

21. The method of claim 1, wherein the second surface of the cavity includes fewer or smaller gas nucleation sites than the first surface of the cavity.

22. The method of claim 1, wherein applying the coating to produce the second surface of the cavity facilitates attachment of biological molecules to the second surface.

23. The method of claim 1, wherein applying the coating to produce the second surface of the cavity further comprises improving the biofunctionalization of the device.

24. The method of claim 1, wherein forming the cavity comprises forming at least two parallel walls.

25. A micro-fabricated device comprising:

a substrate defining a cavity passing through the substrate, the cavity defining a surface to form a portion of a fluid path;

a coating applied to the surface of the cavity; and

a membrane defining a first surface and a second surface, the second surface cooperating with the cavity to form a portion of the fluid path, wherein the surface of the cavity is produced by a first dry removal process and is associated with a first roughness, and the first roughness is reduced by a second wet removal process to define a second roughness.

26. The device of claim 25, wherein the second roughness includes an average size variation in a direction normal to the surface of the cavity of less than about 3 micrometers.

27. The device of claim 25, wherein the membrane is associated with a wave defining an oscillation having a spatial wavelength and the second roughness includes an average size variation in a direction normal to the surface of the cavity of about 3 to about 10 percent of the spatial wavelength.

28. The device of claim 25, wherein the cavity includes a length dimension between about 10 micrometers and about 10,000 micrometers.

29. The device of claim 25, wherein the cavity includes a depth dimension between about 100 micrometers and about 1,000 micrometers.

30. The device of claim 25, wherein the membrane includes a thickness dimension between about 0.1 micrometers and about 20 micrometers.

31. The device of claim 25, further comprising:

an intermediate layer disposed between the substrate and the membrane, wherein the intermediate layer comprises an etch stop material to hinder the first or second removal processes, or both from affecting the second surface of the membrane.

32. The device of claim 31, wherein the intermediate layer includes a thickness dimension of between about 0.1 micrometers and about 10 micrometers.

33. The device of claim 31, wherein a first thickness dimension of the intermediate layer is determined at least in part on a second thickness dimension of a layer of an interaction between a fluid and the membrane, the second thickness measured in a direction normal to the first or second surface of the membrane.

34. The device of claim 25, wherein the micro-fabricated device comprises at least one of an acoustic sensor, a viscosity sensor, a density sensor, a mass sensor, or any combination thereof.

35. The device of claim 34, wherein the wet removal process or the coating reduce in number or in size one or more gas nucleation sites in at least one of the surface of the cavity, the coating, or both.

36. The device of claim 34, wherein at least one of the wet removal process, the coating, or both hinder debris associated with the first roughness from engaging the membrane.

37. The device of claim 34, wherein the substrate comprises silicon and the first dry removal process comprises deep reactive ion etching.

38. The device of claim 34, wherein the wet removal process or the coating reduce contamination of a fluid in the fluid path.

39. The device of claim 25, wherein the micro-fabricated device comprises a flexural plate wave device.

40. A micro-fabricated device comprising:

a first means for forming a cavity in a substrate material to define a surface, the surface associated with a first roughness;

a second means for reducing the first roughness to define a second roughness associated with the surface; and

a membrane cooperating with the cavity to form a portion of a fluid path.