Method and forming a micromirror array device with a small pitch size

• US 7,422,920 B2
• Filed: 03/23/2006
• Issued: 09/09/2008
• Est. Priority Date: 07/03/2003
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Patel, Satyadev R., Huibers, Andrew G.
• Primary Examiner(s): Smoot; Stephen W
• Application Number:
  US11/388,116
• Publication Number:
  US 20060177957A1
• Time in Patent Office: 901 Days
• Field of Search: 438/52
• US Class Current: 438/52
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: H04N 5/7458 the modulator being an array of deformable mirrors, e.g. digital micromirror device [DMD]

Abstract

A spatial light modulator is disclosed, along with a method for making such a modulator that comprises an array of micromirror devices. The center-to-center distance and the gap between adjacent micromirror devices are determined corresponding to the light source being used so as to optimize optical efficiency and performance quality. The micromirror device comprises a hinge support formed on a substrate and a hinge that is held by the hinge support. A mirror plate is connected to the hinge via a contact, and the distance between the mirror plate and the hinge is determined according to desired maximum rotation angle of the mirror plate, the optimum gap and pitch between the adjacent micromirrors. In a method of fabricating such spatial light modulator, one sacrificial layer is deposited on a substrate followed by forming the mirror plates, and another sacrificial layer is deposited on the mirror plates followed by forming the hinge supports. The two sacrificial layers are removed via the small gap between adjacent mirror devices with spontaneous vapor phase chemical etchant.

Claims

1. A method, comprising:

depositing first and second sacrificial layers on a substrate, and forming a hinge layer on one of the first and second sacrificial layers, and forming a mirror plate layer on the other one of the first and second sacrificial layers;

wherein the one of the first and second sacrificial layers that is disposed between the hinge layer and the mirror plate layer has a thickness of from about 0.15 to about 1.5 micron;

wherein the mirror plate layer is patterned to form an array of individual mirror plates having a gap between adjacent mirror plates of about 0.1 to about 0.5 micrometers; and

removing the first and second sacrificial layers to form movable mirror plates.

2. The method of claim 1, wherein the adjacent mirror plates in the array have a gap from about 0.15 micron to 0.5 micron.

3. The method of claim 1, wherein the adjacent mirror plates in the array have a gap from about 0.15 micron to about 0.25 micron.

4. The method of claim 1, wherein the adjacent mirror plates in the array have a center-to-center distance from about 4.38 to about 10.16 microns.

5. The method of claim 1, wherein each individual mirror plate is attached to the hinge layer at an attachment point that is substantially at the geometric center of the individual mirror plate such that the individual mirror plate is capable of rotating symmetrically after the sacrificial layers are removed.

6. The method of claim 1, wherein the substrate is a semiconductor substrate having formed thereon an array of electrodes and circuitry.

7. The method of claim 6, wherein each individual mirror plate is associated with two or more electrodes for electrostatically rotating the individual mirror plate after removal of the sacrificial layers.

8. The method of claim 1, wherein the first sacrificial layer and second sacrificial layer comprise poly-silicon.

9. The method of claim 1, wherein the one of the first and second sacrificial layers that is disposed between the hinge layer and the mirror plate layer has a thickness of 0.15 to about 0.45 micron.

10. The method of claim 1, wherein the one of the first and second sacrificial layers that is disposed between the hinge layer and the mirror plate layer has a thickness of about 0.5 to about 1.5 micron.

11. The method of claim 1, wherein the first sacrificial layer is deposited on the substrate;

wherein the hinge layer is deposited and patterned on the first sacrificial layer;

wherein the second sacrificial layer is deposited on the patterned hinge layer; and

wherein the mirror plate layer is deposited and patterned on the second sacrificial layer.

12. The method of claim 1, wherein the first sacrificial layer is deposited on the substrate;

wherein the mirror plate layer is deposited and patterned on the first sacrificial layer;

wherein the second sacrificial layer is deposited on the patterned mirror plate; and

wherein the hinge layer is deposited and patterned on the second sacrificial layer such that the individual mirror plates are connected to the hinge layer.

13. A method, comprising:

depositing a first sacrificial layer and a second sacrificial layer on a substrate, and forming a hinge layer on one of the first sacrificial layer and the second sacrificial layer, and forming a mirror plate layer on the other one of the first sacrificial layer and the second sacrificial layer;

wherein the one of the first sacrificial layer and the second sacrificial layer that is disposed between the hinge layer and the mirror plate layer has a thickness between about 0.15 to about 1.5 micron;

wherein the mirror plate layer is patterned to form individual mirror plates having a center to center distance between adjacent mirror plates of about 4.38 to about 10.16 micrometers; and

removing the first and second sacrificial layers to form movable mirror plates.

14. The method of claim 13, wherein adjacent mirror plates have a gap of about 0.5 micron or less.

15. The method of claim 14, wherein the adjacent mirror plates have a gap of about 0.1 micron to about 0.5 micron.

16. The method of claim 13, wherein the hinge layer is formed on the second sacrificial layer and adjacent mirror plates have a gap from about 0.15 micron to about 0.5 micron.

17. The method of claim 13, wherein the one of the first sacrificial layer and the second sacrificial layer that is disposed between the hinge layer and the mirror plate layer has a thickness between about 0.15 to about 0.45 micron.

18. The method of claim 13, wherein the one of the first and second sacrificial layers that is disposed between the hinge layer and the mirror plate layer has a thickness between about 0.5 to about 1.5 micron.

19. The method of claim 13, wherein each mirror plate is attached to the hinge layer at an attachment point that is substantially at the geometric center of the mirror plate such that the mirror plate is capable of rotating symmetrically after the first sacrificial layer and second sacrificial layer are removed.

20. The method of claim 13, wherein the substrate is a semiconductor substrate having formed thereon an array of electrodes and circuitry.

21. The method of claim 20, wherein each mirror plate of the array is associated with two or more electrodes for electrostatically rotating the mirror plate after removal of the sacrificial layers.

22. The method of claim 13, wherein the first sacrificial layer and second sacrificial layer comprise poly-silicon.

23. The method of claim 13, wherein the first sacrificial layer is deposited on the substrate;

wherein the hinge layer is deposited and patterned on the first sacrificial layer so as to form the hinge;

wherein the second sacrificial layer is deposited on the patterned hinge layer; and

wherein the mirror plate layer is deposited and patterned on the second sacrificial layer so as to form the mirror plate that is connected to the hinge-layer.

24. The method of claim 13, wherein the first sacrificial layer is deposited on the substrate;

wherein the mirror plate layer is deposited and patterned on the first sacrificial layer so as to form the mirror plate;

wherein the second sacrificial layer is deposited on the patterned mirror plate; and

wherein the hinge layer is deposited and patterned on the second sacrificial layer such that the mirror plate is connected to the hinge layer.

25. A method, comprising:

depositing first and second sacrificial layers on a substrate, and forming a hinge layer on one of the first and second sacrificial layers, and forming a mirror plate layer on the other one of the first and second sacrificial layers;

wherein the one of the first and second sacrificial layers that is disposed between the hinge layer and the mirror plate layer has a thickness of from about 0.15 to about 1.5 micron;

patterning the mirror plate layer to form individual mirror plates having a center to center distance between adjacent mirror plates of about 4.38 to about 10.16 micrometers and having a gap between adjacent mirror plates of about 0.1 to about 0.5 micrometers; and

removing the first and second sacrificial layers to allow the mirror plates to move.

26. The method of claim 25, wherein the adjacent mirror plates in the array have a gap of about 0.15 micron to about 0.5 micron.

27. The method of claim 25, wherein each mirror plate is attached to the hinge layer at an attachment point that is substantially at the geometric center of the mirror plate such that the mirror plate is capable of rotating symmetrically after the sacrificial layers are removed.

28. The method of claim 25, wherein the substrate is a semiconductor substrate having formed thereon an array of electrodes and circuitry.

29. The method of claim 28, wherein each mirror plate is associated with two or more electrodes for electrostatically rotating the said mirror plate after removal of the sacrificial layers.

30. The method of claim 25, wherein the sacrificial layers comprise poly-silicon.

31. The method of claim 25, wherein the one of the first and second sacrificial layers that is disposed between the hinge layer and the mirror plate layer has a thickness between about 0.15 to about 0.45 micron.

32. The method of claim 25, wherein the one of the first and second sacrificial layers that is disposed between the hinge layer and the mirror plate layer has a thickness between about 0.5 to about 1.5 micron.

33. The method of claim 25, wherein the first sacrificial layer is deposited on the substrate;

wherein the hinge layer is deposited and patterned on the first sacrificial layer;

wherein the second sacrificial layer is deposited on the patterned hinge layer; and

wherein the mirror plate layer is deposited and patterned on the second sacrificial layer.

34. The method of claim 25, wherein the first sacrificial layer is deposited on the substrate;

wherein the mirror plate layer is deposited and patterned on the first sacrificial layer;

wherein the second sacrificial layer is deposited on the patterned mirror plate; and

wherein the hinge layer is deposited and patterned on the second sacrificial layer.