Method for producing and testing a corrosion-resistant channel in a silicon device

• US 20040096992A1
• Filed: 11/18/2002
• Published: 05/20/2004
• Est. Priority Date: 11/18/2002
• Status: Active Grant

• Current Assignee: SMC Kabushiki Kaisha
• Original Assignee: Redwood Microsystems, Inc.
• Inventors: Harris, James M., Patel, Sapna
• Granted Patent: US 6,869,818 B2
• Time in Patent Office: Days
• US Class Current: 438/11
• CPC Class Codes: B81B 2201/054 Microvalves
• CPC Class Codes: B81B 2201/058 Microfluidics not provided for in B81B2201/051 - B81B2201/054
• CPC Class Codes: B81B 7/0012 Protection against reverse engineering, unauthorised use, use in unintended manner, wrong insertion or pin assignment
• CPC Class Codes: B81C 2203/038 Bonding techniques not provided for in B81C2203/031 - B81C2203/037
• CPC Class Codes: B81C 99/0045 End test of the packaged device
• CPC Class Codes: F16K 2099/0074 using photolithography, e.g. etching
• CPC Class Codes: F16K 99/0001 Microvalves microdevices B81B1/00; manufacture or treatment of devices or systems in or on a substrate B81C1/00; microfluidic structures B01L3/5027; micropumps F04B19/006
• CPC Class Codes: F16K 99/0015 Diaphragm or membrane valves
• CPC Class Codes: F16K 99/0034 Operating means specially adapted for microvalves
• CPC Class Codes: F16K 99/0036 operated by temperature variations
• CPC Class Codes: F16K 99/0059 actuated by a pilot fluid
• CPC Class Codes: H01L 21/02071 the processing being a delineation, e.g. RIE, of conductive layers
• CPC Class Codes: H01L 22/20 Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps
• CPC Class Codes: H01L 22/24 Optical enhancement of defects or not directly visible states, e.g. selective electrolytic deposition, bubbles in liquids, light emission, colour change voltage contrast G01R31/311
• CPC Class Codes: H01L 22/34 Circuits for electrically characterising or monitoring manufacturing processes, e. g. whole test die, wafers filled with test structures, on-board-devices incorporated on each die, process control monitors or pad structures thereof, devices in scribe line switching, multiplexing, gating devices G01R19/25; process control with lithography, e.g. dose control, G03F7/20; structures for alignment control by optical means G03F7/70633

Abstract

A method for producing a corrosion-resistant channel in a wetted path of a silicon device enables such device to be used with corrosive compounds, such as fluorine. A wetted path of a MEMS device is coated with either (1) an organic compound resistant to attack by atomic fluorine or (2) a material capable of being passivated by atomic fluorine. The device is then exposed to a gas that decomposes into active fluorine compounds when activated by a plasma discharge. One example of such a gas is CF₄, an inert gas that is easier and safer to work with than volatile gases like ClF₃. The gas will passivate the material (if applicable) and corrode any exposed silicon. The device is tested in such a manner that any unacceptable corrosion of the wetted path will cause the device to fail. If the device operates properly, the wetted path is deemed to be resistant to corrosion by fluorine or other corrosive compounds, as applicable.

Claims

1. A method for protecting a wetted path of a silicon device from corrosion by fluorine atoms and for testing the adequacy of the protection, the method comprising:

coating the wetted path with a material that can be passivated by fluorine atoms;

exposing the wetted path to a gas environment, which includes fluorine atoms, that will passivate the material and corrode any exposed silicon in the wetted path;

testing the silicon device in a manner where corrosion in the wetted path is likely to cause failure of the silicon device; and

in response to the silicon device operating satisfactorily during such testing, determining that the wetted path is protected from corrosion by fluorine atoms.

2. The method of claim 1 wherein the material is one that can form a eutectic bond with silicon.

3. The method of claim 1 wherein the material is aluminum.

4. The method of claim 1 wherein the material is nickel.

5. The method of claim 1 wherein the silicon device is comprised of at least a portion of two wafers, at least one of which is silicon, bonded together and wherein regions of the wafers corresponding to the wetted path are coated with the material prior to bonding the wafers.

6. The method of claim 5 wherein the material is one that can form a eutectic bond with silicon.

7. The method of claim 6 wherein a bonding region of one of the wafers also is coated with the material and the two wafers are bonded together through a eutectic bond.

8. The method of claim 7 wherein the material is aluminum.

9. The method of claim 7 wherein the material is nickel.

10. The method of claim 1, wherein the gas environment includes a fluorinated hydrocarbon with an effective fluorine-to-carbon ratio >

2.

11. The method of claim 1 wherein the gas environment is CF₄ activated by a plasma discharge.

12. The method of claim 1, wherein, after the material has been passivated, the wetted path is exposed to a fluorinated hydrocarbon gas with an effective fluorine-to-carbon ratio ≦

2 to further protect the wetted path from corrosion by the fluid.

13. The method of claim 12, wherein the fluorinated hydrocarbon gas is C₄F₈.

14. A method for protecting a wetted path of a silicon device from corrosion by a fluid and for testing the adequacy of the protection, the method comprising:

coating the wetted path with an organic compound that protects silicon from corrosion by the fluid and that is non-reactive or slowly reactive to fluorine;

exposing the wetted path to a gas environment, which includes fluorine atoms, that will corrode any exposed silicon in the wetted path;

testing the silicon device in a manner where corrosion of the wetted path is likely to cause failure of the silicon device; and

in response to the silicon device operating satisfactorily during such testing, determining that the wetted path is protected from corrosion by fluorine atoms.

15. The method of claim 14 wherein the organic compound is benzocyclobutene.

16. The method of claim 14 wherein the silicon device is comprised of at least two silicon wafers and the two wafers are bonded together with the organic compound.

17. The method of claim 16 wherein the organic compound is benzocyclobutene.

18. The method of claim 14 wherein the gas environment is CF₄ activated by a plasma discharge.

19. The method of claim 14, wherein, after the wetted path is coated with the organic compound, the wetted path is exposed to a fluorinated hydrocarbon gas with an effective fluorine-to-carbon ratio ≦

2 to further protect the wetted path from corrosion by the fluid.

20. The method of claim 19, wherein the fluorinated hydrocarbon gas is C₄F₈.

21. The method of claim 14, wherein the gas environment includes a fluorinated hydrocarbon with an effective fluorine-to-carbon ratio >

2.