Re-coating MEMS devices using dissolved resins

• US 6,753,037 B2
• Filed: 06/21/2001
• Issued: 06/22/2004
• Est. Priority Date: 06/21/2000
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Lopes, Vincent C., Miller, Seth, Brenner, Michael F.
• Primary Examiner(s): Beck, Shrive P.
• Assistant Examiner(s): JOLLEY, KIRSTEN
• Application Number:
  US09/886,781
• Publication Number:
  US 20020012744A1
• Time in Patent Office: 1,097 Days
• Field of Search: 427/240, 427/425, 427/385.5, 427/407.1, 427/409, 427/388.1, 427/379, 118/52, 118/320
• US Class Current: 427/240
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 3/0005 Anti-stiction coatings
• CPC Class Codes: B81C 1/0096 For avoiding stiction when the device is in use, i.e. after manufacture has been completed
• CPC Class Codes: B81C 2201/112 Depositing an anti-stiction or passivation coating, e.g. on the elastic or moving parts
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means

Abstract

A method for coating free-standing micromechanical devices using spin-coating. A solution with high solids loading but low viscosity can penetrate the free areas of a micromachined structure. Spinning this solution off the wafer or die results in film formation over the devices without the expected damage from capillary action. If an organic polymer is used as the solid component, the structures may be re-released by a traditional ash process. This method may be used as a process in the manufacture of micromechanical devices to protect released and tested structures, and to overcome stiction-related deformation of micromechanical devices associated with wet release processes.

Claims

1. A method of coating free-standing micromechanical devices, the method comprising:

depositing an organic resin coating material on said micromechanical device in sufficient quantity to substantially encapsulate micromechanical device, said coating material comprised of at least 35% solids in a solvent, said coating material having a viscosity no greater than 120 centistokes; and

curing said coating material.

2. The method of claim 1, said depositing comprising depositing a coating material having a viscosity of 118 centistokes.

3. The method of claim 1, said depositing comprising depositing a coating material having a surfactant.

4. The method of claim 1, said depositing comprising depositing said coating material in a layer thick enough to cover structures on said micromechanical device after the removal of said solvent.

5. The method of claim 1, comprising:

rotating said micromechanical device to distribute said organic coating material.

6. The method of claim 1, comprising:

rotating said micromechanical device at 3000 rpm to distribute said organic coating material.

7. The method of claim 1, said curing comprising:

heating said micromechanical device.

8. The method of claim 1, said curing comprising:

heating said micromechanical device at 100°

C.

9. The method of claim 1, said curing comprising:

heating said micromechanical device to a first elevated temperature to remove a majority of said solvent, and then lowering said temperature to remove additional solvent.

10. A method of coating free-standing micromechanical devices, the method comprising:

depositing an organic resin coating material on said micromechanical device in sufficient quantity to substantially encapsulate said micromechanical device, said coating material comprised of at least 35% solids in a solvent said coating material having a viscosity no greater than 120 centistokes;

rotating said micromechanical device to distribute said organic coating material; and

curing said coating material.

11. The method of claim 10, said depositing comprising depositing a coating material having a viscosity of 118 centistokes.

12. The method of claim 10, said depositing comprising depositing a coating material having a surfactant.

13. The method of claim 10, said depositing comprising depositing said coating material in a layer thick enough to cover structures on said micromechanical device after the removal of said solvent.

14. The method of claim 10, comprising:

rotating said micromechanical device at 3000 rpm to distribute said organic coating material.

15. The method of claim 10, said curing comprising:

heating said micromechanical device.

16. The method of claim 10, said curing comprising:

heating said micromechanical device at 100°

C.

17. The method of claim 10, said curing comprising:

heating said micromechanical device to a first elevated temperature to remove a majority of said solvent, and then lowering said temperature to remove additional solvent.

18. A method of coating free-standing micromechanical devices, the method comprising:

depositing an organic resin coating material on said micromechanical device in sufficient quantity to substantially encapsulate said micromechanical device, said coating material comprised of at least 40% solids in a solvent, said coating material having a viscosity no greater than 120 centistokes; and

curing said coating material.

19. The method of claim 18, said depositing comprising depositing a coating material comprised of between 40 and 50% solids.

20. The method of claim 18, said depositing comprising depositing a coating material comprised of 49% solids.

21. The method of claim 18, said depositing comprising depositing a coating material having a viscosity of 118 centistokes.

22. The method of claim 18, said depositing comprising depositing a coating material having a surfactant.

23. The method of claim 18, said depositing comprising depositing said coating material in a layer thick enough to cover structures on said micromechanical device after the removal of said solvent.

24. The method of claim 18, comprising:

rotating said micromechanical device to distribute said organic coating material.

25. The method of claim 18, comprising:

rotating said micromechanical device at 3000 rpm to distribute said organic coating material.

26. The method of claim 18, said curing comprising:

heating said micromechanical device.

27. The method of claim 18, said curing comprising:

heating said micromechanical device at 100°

C.

28. The method of claim 18, said curing comprising:

heating said micromechanical device to a first elevated temperature to remove a majority of said solvent, and then lowering said temperature to remove additional solvent.

29. A method of coating free-standing micromechanical devices, the method comprising:

depositing a solvent layer on said micromechanical device having moveable structures wider than such structures are high;

depositing an organic resin coating material on said solvent layer in sufficient quantity to substantially encapsulate said moveable structures;

allowing said organic resin coating material to displace said solvent layer; and

curing said organic resin coating material.

30. The method of claim 29, said depositing an organic resin coating material comprising depositing an organic resin coating material having a viscosity no greater than 120 centistokes.

31. The method of claim 29, said depositing an organic resin coating material comprising depositing an organic resin coating material having a viscosity of 118 centistokes.

32. The method of claim 29, said depositing a solvent layer comprising depositing a layer of propylene glycol monomethyl ether.

33. The method of claim 29, said depositing an organic resin coating material comprising depositing an organic resin coating material comprised of at least 35% solids in a solvent.

34. The method of claim 29, said depositing a solvent layer comprising depositing a layer of solvent and dissolved organic resin.

35. The method of claim 29, said depositing a solvent layer comprising depositing a layer of propylene glycol monomethyl ether and dissolved organic resin.

36. The method of claim 29, comprising:

rotating said micromechanical device to distribute said solvent.

37. The method of claim 29, comprising:

rotating said micromechanical device to distribute said organic resin coating material.

38. The method of claim 29, comprising:

rotating said micromechanical device to remove excess solvent.

39. The method of claim 29, comprising:

rotating said micromechanical device to remove excess organic resin coating material.

40. The method of claim 29, said curing comprising:

heating said micromechanical device.

41. The method of claim 29, said curing comprising:

heating said micromechanical device at 100°

C.

42. The method of claim 29, said curing comprising:

heating said micromechanical device to a first elevated temperature to remove a majority of said solvent, and then lowering said temperature to remove additional solvent.