Suspended moving channels and channel actuators for microfluidic applications and method for making

• US 6,180,536 B1
• Filed: 06/04/1998
• Issued: 01/30/2001
• Est. Priority Date: 06/04/1998
• Status: Expired due to Fees

• Current Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Original Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Inventors: MacDonald, Noel C., Chong, John M.
• Primary Examiner(s): Utech, Benjamin L.
• Assistant Examiner(s): Vinh, Lan
• Application Number:
  US09/090,840
• Time in Patent Office: 971 Days
• Field of Search: 438/712, 438/706, 438/718, 438/719, 438/720, 438/725, 438/745, 216/2, 216/39, 257/734, 257/735
• US Class Current: 438/745
• CPC Class Codes: B81B 2201/051 Micromixers, microreactors
• CPC Class Codes: B81C 1/00587 Processes for avoiding or controlling over-etching not provided for in B81C1/00571 - B81C1/00579
• CPC Class Codes: Y10S 366/03 Micromixers: variable geometry from the pathway influences mixing/agitation of non-laminar fluid flow

Abstract

A microfabrication process for making enclosed, subsurface microfluidic tunnels, cavities, channels, and the like within suspended beams includes etching a single crystal silicon wafer to produce trenches defining a beam. The trench walls are oxidized, and the interior of the beam is etched through a channel via on the top of the beam to form a hollow beam with oxide sidewalls. The beam is released, and the via is then sealed to form an enclosed released channel beam,

Claims

1. A process for fabricating a released channel beam, comprising:

etching trenches having vertical sidewalls in a substrate, said sidewalls defining the sides of at least one beam to be released from the substrate;

providing mask layers on the sidewalls of said at least one beam;

isotropically etching said at least one beam to form a channel which extends between the mask layers on said beam sidewalls; and

further etching the trenches to undercut and release the beam from the substrate.

2. The process of claim 1, further including controlling the etching of the beam to regulate the depth of said channel.

3. The process of claim 1, wherein isotropically etching the beam and further etching the trenches are carried out simultaneously.

4. The process of claim 1, further including closing the channel in the beam to produce a subsurface closed channel.

5. The process of claim 1, wherein providing sidewall-mask layers includes oxidizing the beam.

6. The process of claim 1, wherein providing sidewall-mask layers includes depositing an oxide material on said trench sidewalls.

7. The process of claim 1 further including:

providing a top surface mask on the beam to be released; and

providing at least one via opening in said top surface mask;

and wherein isotropically etching the beam includes etching through said at least one via opening for a length of time sufficient to form said channel between said mask layers on the beam sidewalls; and

thereafter closing said at least one via opening to form a closed channel.

8. The process of claim 7 including further isotropically etching the trenches simultaneously with isotropically etching the beam through said at least one via opening to release said beam.

9. The process of claim 8, further including controlling the etching of said beam to provide a floor for said beam channel.

10. The process of claim 1, further including, prior to etching said trenches:

providing an oxide mask layer on a top surface of said substrate;

producing in said oxide mask layer a trench pattern forming the shape of a beam structure; and

thereafter vertically etching said trenches in said substrate through said trench pattern to define the sidewalls of said beam structure.

11. The process of claim 10, wherein said vertical etching of said substrate produces beam trenches having substantially vertical sidewalls.

12. The process of claim 10, further including:

producing in said oxide mask layer a pattern for at least one channel via between the sides of said beam structure.

13. The process of claim 12, wherein isotropically etching the beam includes etching the beam through said at least one channel via to produce a subsurface channel in said beam.

14. The process of claim 12, further including:

providing a protective layer over said at least one channel via;

thereafter etching said trenches to produce said vertical sidewalls to define the sides of a beam to be released and thereafter providing an oxide layer on the beam sidewalls;

removing said protective layer from said at least one channel via; and

thereafter etching the beam through said channel via.

15. The process of claim 14, wherein etching the beam includes vertically etching the beam to produce a pilot channel within said beam, the process further including;

isotropically etching said beam through said pilot channel.

16. The process of claim 14, further including closing said at least one channel via to provide a subsurface channel within said beam.

17. The process of claim 15, further including, after producing said pilot channel:

isotropically etching said beam structure through said channel via to produce a subsurface channel within said beam structure;

simultaneously isotropically etching said trenches to release said beam structure; and

thereafter sealing said channel via.

18. The process of claim 17, further including depositing metal on said released beam structure.

20. The process of claim 11, further including producing multiple channel vias on said beam structure, wherein etching said substrate includes etching multiple subsurface channels in said beam corresponding to said channel vias.

21. The process of claim 20, further including producing said multiple channel vias at an angle to a longitudinal axis of a beam structure.

22. The process of claim 12, wherein said channel vias are elongated, and further including varying the spacing of channels along the length of said beam structure by varying the number and spacing of said channel vias.

19. A process for fabricating a released channel beam, comprising:

providing an oxide mask layer on a top surface of a substrate;

producing in said oxide mask layer a pattern including a trench pattern defining the shape of at least one beam to be released from the substrate and including a via pattern defining the location and configuration of at least two closely-spaced channel vias on said beam;

vertically etching through said trench pattern to produce in said substrate trenches having vertical sidewalls, the sidewalls defining the sides of said at least one beam to be released from the substrate, and vertically etching through said via pattern to produce access ports in the beam;

providing mask layers on the sidewalls of said at least one beam;

etching the beam through said access ports to form a channel in the beam between the mask layers on the beam sidewalls; and

further etching the trenches to undercut and release the beam from the substrate.