Method of making a support post for a micromechanical device

• US 5,784,212 A
• Filed: 07/25/1996
• Issued: 07/21/1998
• Est. Priority Date: 11/02/1994
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Hornbeck, Larry J.
• Primary Examiner(s): Dzierzynski, Paul M.
• Assistant Examiner(s): SIKDER, MOHAMMAD YUNUS
• Application Number:
  US08/686,222
• Time in Patent Office: 726 Days
• Field of Search: 359/871, 359/872, 359/883, 359/295, 359/224, 359/291, 359/214, 359/292, 359/293
• US Class Current: 359/871
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 2203/0361 Tips, pillars
• CPC Class Codes: B81B 3/0072 For controlling internal stress or strain in moving or flexible elements, e.g. stress compensating layers
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G06K 15/1252 using an array of light modulators, e.g. a linear array
• CPC Class Codes: Y10S 359/904 Micromirror

Abstract

A support pillar 426 for use with a micromechanical device, particularly a digital micromirror device, comprising a pillar material 422 supported by a substrate 400 and covered with a metal layer 406. The support pillar 426 is fabricated by depositing a layer of pillar material on a substrate 400, patterning the pillar layer to define a support pillar 426, and depositing a metal layer 406 over the support pillar 426 enclosing the support pillar. A planar surface even with the top of the pillar may be created by applying a spacer layer 432 over the pillars 426. After applying the spacer layer 432, holes 434 are patterned into the spacer layer to remove any spacer material that is covering the pillars. The spacer layer is then reflowed to fill the holes and lower the surface of the spacer layer such that the surface is coplanar with the tops of the support pillars 426.

Claims

1. A method of fabricating a metalized support pillar comprising steps of:

depositing a pillar material on a substrate;

patterning said pillar material to define a support pillar;

depositing a metal layer over said support pillar wherein said support pillar is enclosed by said metal layer to form a metalized support pillar;

depositing a spacer layer around said metalized support pillar;

removing a portion of said spacer layer around and on top of said metalized support pillar;

said removing step forming holes between said spacer layer and said metalized support pillar; and

reflowing remaining portion of said spacer layer to fill said holes between said second spacer layer and said metalized support pillar.

2. The method of claim 1 wherein said pillar material is an organic photoresist.

3. The method of claim 1 wherein said pillar material is a photoresist, said method further comprising the step of deep UV hardening said pillar material.

4. The method of claim 1 wherein said spacer layer is an organic photoresist.

5. The method of claim 1 wherein said depositing a pillar material step comprises spinning on a layer of an organic photoresist.

6. The method of claim 1 wherein said depositing a spacer layer step comprises spinning on a layer of an organic photoresist.

7. The method of claim 1 wherein said patterning step comprises partially removing said pillar material to leave said support pillar.

8. The method of claim 1 wherein said depositing a metal layer step comprises sputtering a metal layer over said support pillar.

9. The method of claim 1 wherein said depositing a metal layer step comprises sputtering an aluminum alloy over said support pillar.

10. The method of claim 1 wherein said reflowing step comprises heating said spacer layer.

11. A method of fabricating a micromirror device comprising steps of:

depositing a pillar material on a substrate;

patterning said pillar material to define at least one first support pillar;

depositing a first metal layer on said first support pillar to a form a first metalized support pillar;

depositing a first spacer layer on said substrate;

depositing a second metal layer over said first spacer layer and said first support pillar, said second metal layer forming at least one hinge;

depositing a second pillar material on said second metal layer;

patterning said second pillar material to define at least one second support pillar attached to said hinge;

depositing a third metal layer over said second support pillar to form a second metalized support pillar;

depositing a second spacer layer over said first spacer layer;

removing a portion of said second spacer layer from around and on top of said second metalized support pillar;

said removing step forming holes between said second spacer layer and said second metalized support pillar;

reflowing remaining position of said second spacer layer to fill said holes between said second spacer layer and said second metalized support pillar;

depositing a fourth metal layer over said second spacer layer, said fourth metal layer forming as least one mirror attached to said second support pillar; and

removing said first spacer and said second spacer layer to form an air gap beneath said hinge and said mirror.

12. The method of claim 11 further comprising the steps of:

removing a portion of said first spacer layer from around and on top of said first metalized support pillar; and

reflowing said first spacer layer to fill any gap between said first spacer layer and said first metalized support pillar.

13. The method of claim 11 wherein at least one pillar material is a photoresist.

14. The method of claim 13 further comprising the step of deep UV hardening said photoresist pillar material.

15. The method of claim 11 wherein at least one spacer is a photoresist.

16. The method of claim 11 wherein said at least one spacer layer is deposited by spinning on a layer of an organic photoresist.

17. The method of claim 11 wherein at least one step of depositing a metal layer comprises the step of sputtering a metal layer.

18. The method of claim 11 wherein said at least one metal layer is an aluminum alloy layer.

19. A method of fabricating a micromirror device comprising steps of:

depositing and patterning a pillar material on a substrate to define at least one support pillar;

depositing a first metal layer on said support pillar to a form a metalized support pillar;

depositing a spacer layer on said substrate;

removing a portion of said spacer layer from on top of and around said metalized support pillar;

said removing step forming holes between said spacer layer and said metalized support pillar

reflowing remaining portion of said spacer layer to fill said holes between said second-spacer and said metalized support pillar;

depositing at least one additional metal layer over said spacer layer and said metalized support pillar, said at least one additional metal layer forming at least one hinge and at least one mirror suspended by said hinge from said support pillar;

removing portions of said spacer layer to form an air gap beneath said hinge and said mirror.

20. The method of claim 19 wherein said pillar material is a photoresist.

21. The method of claim 20 further comprising the step of deep UV hardening said photoresist pillar material.

22. The method of claim 19 wherein said spacer layer is a photoresist.

23. The method of claim 19 wherein said step of depositing a first metal layer comprises the step of sputtering a metal layer on said support pillar.

24. The method of claim 19 wherein said step of depositing a first metal layer comprises the step of sputtering an aluminum alloy on said support pillar.