OPTIMIZATION OF DESICCANT USAGE IN A MEMS PACKAGE

• US 20110012219A1
• Filed: 09/28/2007
• Published: 01/20/2011
• Est. Priority Date: 09/28/2007
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Palmateer, Lauren, Heald, David, He, Rihui, Wu, Lingling, Lin, Yen Hua
• Granted Patent: US 8,435,838 B2
• Time in Patent Office: Days
• US Class Current: 257/433
• CPC Class Codes: B81C 1/00285 using materials for controlling the level of pressure, contaminants or moisture inside of the package, e.g. getters
• CPC Class Codes: B81C 1/00674 Treatments for improving wear resistance

Abstract

A MEMS device may be package with a desiccant to provide a moisture-free environment. In order to avoid undesirable effects on the MEMS device, the desiccant may be selected or treated so as to be compatible with a particular MEMS device. This treatment may include baking of the desiccant to as to cause outgassing of moisture or other undesirable material. The structure of the MEMS device may also be altered to improve compatibility with particular desiccants.

Claims

1. A method of encapsulating a MEMS device, the method comprising:

providing a MEMS package, said MEMS package comprising

a substrate supporting a MEMS device;

a backplate sealed to said substrate to form the MEMS package; and

a desiccant within the MEMS package, the desiccant comprising

calcium oxide and a polymer binding; and

heating the MEMS package to cause moisture within the package to be chemically absorbed by the calcium oxide.

2. The method of claim 1, wherein heating the MEMS package is performed prior to operation of the MEMS device.

3. The method of claim 1, wherein heating the MEMS package causes moisture to be driven from the polymer.

4. The method of claim 1, wherein the MEMS package is heated at a temperature higher than about 70°

C.

5. The method of claim 4, wherein the MEMS package is heated at a temperature higher than about 120°

C.

6. The method of claim 1, wherein the polymer comprises phenol.

7. A method of encapsulating a MEMS device, the method comprising:

providing a substrate supporting a MEMS device;

providing a backplate;

providing a desiccant, said desiccant comprising calcium oxide and polytetrafluoroethylene;

baking said desiccant under conditions sufficient to cause outgassing of organics retained therein; and

sealing said backplate to said substrate to form a MEMS package encapsulating the MEMS device and the desiccant.

8. The method of claim 7, wherein baking said desiccant comprises baking said desiccant at a temperature higher than about 105°

C.

9. The method of claim 8, wherein baking said desiccant comprises baking said desiccant at a temperature higher than about 120°

C.

10. A method of encapsulating a MEMS device, the method comprising:

providing a substrate supporting a MEMS device;

providing a backplate;

providing a desiccant, said desiccant comprising calcium oxide and a polymer binding;

baking said desiccant under conditions sufficient to cause outgassing of solvents retained therein; and

sealing said backplate to said substrate to form a MEMS package encapsulating the MEMS device and the desiccant.

11. The method of claim 10, wherein providing a desiccant comprises providing a desiccant in paste form, and wherein baking said desiccant comprising baking said desiccant at a temperature higher than that required to solidify the desiccant.

12. The method of claim 10, wherein providing a desiccant comprises providing a desiccant in paste form, and wherein baking said desiccant comprising baking said desiccant for a duration longer than that required to solidify the desiccant.

13. The method of claim 10, wherein baking said desiccant comprises baking said desiccant at a temperature higher than about 220°

C.

14. The method of claim 13 wherein baking said desiccant comprises baking said desiccant at a temperature higher than about 280°

C.

15. A method of encapsulating a MEMS device, comprising:

providing a substrate supporting a MEMS device, the MEMS device comprising a movable layer, wherein said movable layer comprises aluminum and neodymium;

providing a backplate;

providing a desiccant; and

sealing the backplate to the substrate to form a MEMS package encapsulating the MEMS device and the desiccant.

16. A MEMS package, said MEMS package comprising:

a substrate supporting a MEMS device comprising a movable layer, wherein said movable layer comprises aluminum and neodymium;

a backplate sealed to said substrate to form a MEMS package encapsulating said MEMS device; and

a desiccant sealed within said MEMS package.

17. The MEMS package of claim 16, wherein said movable layer comprises a first sublayer and a second sublayer, said first sublayer comprising nickel, and said second sublayer comprising aluminum and neodymium, wherein said second sublayer is located between said first sublayer and said substrate.

18. The MEMS package of claim 16, wherein said desiccant comprises calcium oxide and a polymer binding.

19. The MEMS package of claim 18, wherein said polymer comprise phenol.

20. The apparatus of claim 16, further comprising:

a processor that is configured to communicate with said MEMS device, said processor being configured to process image data; and

a memory device that is configured to communicate with said processor.

21. The apparatus of claim 20, further comprising a driver circuit configured to send at least one signal to the MEMS device.

22. The apparatus of claim 21, further comprising a controller configured to send at least a portion of the image data to the driver circuit.

23. The apparatus of claim 20, further comprising an image source module configured to send said image data to said processor.

25. The apparatus of claim 20, further comprising an input device configured to receive input data and to communicate said input data to said processor.

24. The apparatus of claim 24, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

26. An MEMS device package, comprising:

means for absorbing moisture;

first means for supporting said absorbing means;

second means for supporting a MEMS structure, wherein the MEMS structure comprises means for inhibiting the formation of protrusions on a surface of the MEMS structure; and

means for sealing said second supporting means to said first supporting means.

27. The MEMS device package of claim 26, wherein the means for absorbing moisture comprises a desiccant.

28. The MEMS device package of claim 26, wherein the first means for supporting said absorbing means comprises a backplate, the second means for supporting a MEMS structure comprises a substrate, and the means for sealing comprises a seal.

29. The MEMS device package of claim 26, wherein the means for inhibiting the formation of protrusions on a surface of the MEMS structure comprises a layer comprising neodymium.