Sacrificial spacer process and resultant structure for MEMS support structure

• US 7,545,552 B2
• Filed: 10/19/2006
• Issued: 06/09/2009
• Est. Priority Date: 10/19/2006
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: U'Ren, Gregory David
• Primary Examiner(s): Choi; William C
• Application Number:
  US11/583,575
• Publication Number:
  US 20080094686A1
• Time in Patent Office: 964 Days
• Field of Search: 359/198, 359/223, 359/224, 359/247, 359/290, 359/302
• US Class Current: 359/290
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 2203/0109 Bridges
• CPC Class Codes: B81B 2203/053 Translation according to an axis perpendicular to the substrate
• 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: B81C 2201/017 Methods for controlling internal stress of deposited layers not provided for in B81C2201/0164 - B81C2201/0169
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26

Abstract

Disclosed is a microelectromechanical systems (MEMS) device and method of manufacturing the same. MEMS such as an interferometric modulator include a sidewall spacer formed adjacent to a movable mirror. The sidewall spacer may be a sacrificial spacer that is removed during fabrication, or it may remain in the final product. Increased clearance is provided between the movable mirror and a support structure during actuation of the movable mirror, thereby avoiding contact during operation of the interferometric modulator. The deformable layer may be deposited in a more continuous fashion over the contour of a lower layer as determined by the contour of the sidewall spacer, resulting in a stronger and more resilient deformable layer.

Claims

1. An interferometric modulator, comprising:

a substrate;

an optical stack over the substrate;

a deformable layer;

a plurality of support structures arranged over the substrate and configured to support the deformable layer;

a cavity defined by the optical stack, the support structures, and the deformable layer; and

a movable mirror disposed within the cavity, wherein the movable mirror is secured to the deformable layer, wherein a cavity ceiling spaced above an edge of the mirror comprises a step transitioning toward the substrate and defining a lower corner at the bottom of the step;

wherein a distance from a sidewall of the movable mirror to the lower corner of the ceiling step is more than 25 percent greater than a distance from an upper surface of the movable mirror to the cavity ceiling above the edge of the mirror when the interferometric modulator is in a relaxed condition.

2. The interferometric modulator of claim 1, wherein the sidewall of the movable mirror comprises a downward edge angle in a range from about 85 degrees to about 95 degrees.

3. The interferometric modulator device of claim 1, wherein the plurality of support structures and the deformable layer are formed from the same material.

4. The interferometric modulator device of claim 1, wherein the plurality of support structures comprise posts supporting the deformable layer on a lower surface of the deformable layer facing the substrate.

5. The interferometric modulator device of claim 1, wherein the plurality of support structures comprise rivets overlying the deformable layer in depressions defined by the deformable layer.

6. The interferometric modulator device of claim 1, wherein the movable conductor comprises aluminum.

7. The interferometric modulator device of claim 1, further comprising a sidewall spacer attached to the sidewall of the movable mirror, wherein the sidewall spacer comprises a substantially convex top surface away from the substrate.

8. The interferometric modulator device of claim 7, wherein the deformable layer conforms to the upwardly convex surface of the sidewall spacer.

9. The interferometric modulator device of claim 1, wherein the distance from the sidewall of the movable mirror to the lower corner of the ceiling step is about 50 percent to about 200 percent greater than the distance from the upper surface of the movable mirror to the cavity ceiling above the edge of the mirror when the interferometric modulator is in the relaxed condition.

10. The interferometric modulator device of claim 1, wherein the distance from the sidewall of the movable mirror to the lower corner of the ceiling step is about 0.3 μ

m to about 0.8 μ

m.

11. An array of interferometric modulators, comprising the interferometric modulator of claim 1.

12. A display device comprising:

an array of interferometric modulators as claimed in claim 11,

a processor that is configured to communicate with the array, the processor being configured to process image data; and

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

13. The display device of claim 12, further comprising a driver circuit configured to send at least one signal to the array.

14. The apparatus as recited in claim 13, further comprising a controller configured to send at least a portion of the image data to the driver circuit.

15. The apparatus as recited in claim 12, further comprising an image source module configured to send the image data to the processor.

16. The apparatus as recited in claim 15, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

17. The apparatus as recited in claim 12, further comprising an input device configured to receive input data and to communicate the input data to the processor.

18. A microelectromechanical systems (MEMS) device, comprising:

a substrate;

a deformable layer;

a plurality of support structures arranged over the substrate and configured to support the deformable layer;

a cavity defined by the substrate, the support structures, and the deformable layer; and

a movable conductor disposed within the cavity, wherein the movable conductor is secured to the deformable layer, and wherein the movable conductor comprises a side wall with an inward reentrant region;

wherein the deformable layer comprises an upwardly convex surface proximal to the inward reentrant region of the sidewall of the movable conductor.

19. The MEMS device of claim 18, wherein the plurality of support structures and the deformable layer are formed from the same material.

20. The MEMS device of claim 18, wherein the movable conductor comprises aluminum.

21. The MEMS device of claim 18, further comprising a sidewall spacer attached to the sidewall of the movable conductor, wherein the sidewall spacer comprises a substantially convex top surface away from the substrate.

22. The MEMS device of claim 21, wherein the upwardly convex surface of the deformable layer is of substantially the same shape as the convex top surface of the sidewall spacer.

23. An interferometric modulator, comprising the MEMS device of claim 18.

24. The interferometric modulator of claim 23, wherein a cavity ceiling spaced above an edge of the movable conductor comprises a step transitioning toward the substrate and defining a lower corner at the bottom of the step, and wherein a distance from the sidewall of the movable conductor to the lower corner of the ceiling step is about 50% to about 200% greater than a distance from an upper surface of the movable conductor to the cavity ceiling above the edge of the conductor when the interferometric modulator is in a relaxed condition.

25. The interferometric modulator of claim 23, wherein a cavity ceiling spaced above an edge of the movable conductor comprises a step transitioning toward the substrate and defining a lower corner at the bottom of the step, and wherein a distance from the sidewall of the movable conductor to the lower corner of the ceiling step is about 0.3 μ

m to about 0.8 μ

m.

26. An interferometric modulator comprising:

means for transmitting light;

means for reflecting light;

means for movably supporting the reflecting means and for providing a restoring force in response to a movement of the reflecting means towards or away from the transmitting means;

a cavity defined by the reflecting means and the supporting means, wherein the reflecting means is disposed within the cavity; and

means for horizontally spacing an edge of the reflecting means from the supporting means more than a vertical distance between an upper surface of the reflecting means and a lower surface of the supporting means.

27. The interferometric modulator of claim 26, wherein the spacing means comprises a gap created by a removed sacrificial sidewall spacer on edges of the reflecting means.

28. The interferometric modulator of claim 26, wherein the spacing means comprises a sidewall spacer on edges of the reflecting means.

29. The interferometric modulator of claim 26, wherein the transmitting means comprises an optical stack.

30. The interferometric modulator of claim 26, wherein the reflecting means comprises a movable mirror.

31. The interferometric modulator of claim 26, wherein the supporting means comprises a deformable layer.