Microelectromechanical device with thermal expansion balancing layer or stiffening layer

• US 8,164,821 B2
• Filed: 02/22/2008
• Issued: 04/24/2012
• Est. Priority Date: 02/22/2008
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Gudlavalleti, Sauri, Chui, Clarence
• Primary Examiner(s): Mack, Ricky
• Assistant Examiner(s): TRA, TUYEN Q
• Application Number:
  US12/072,090
• Publication Number:
  US 20090231666A1
• Time in Patent Office: 1,523 Days
• Field of Search: 359/292, 359/291, 359/293, 359/295, 359/260, 359/237, 359/220, 359/223, 359/224
• US Class Current: 359/292
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• 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 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

An interferometric modulating device is provided with a thermal expansion balancing layer on a side of the movable flexible layer opposite the movable reflector such that when temperature changes the distance between the movable reflector and the optical stack does not change significantly, thereby leading to stable color. Additionally, an interferometric modulating device is provided with a stiffening layer between the movable flexible layer and the movable reflector and at least one hollow void exists on the surface where the movable reflector and the stiffening layer contact each other so that the movable reflector is more rigid to bending, thereby reducing the temperature sensitivity of the movable reflector.

Claims

1. A device comprising:

an electrode;

a fixed reflector which is at least partially reflective;

a movable flexible layer;

a movable reflector which is at least partially reflective, the movable reflector coupled to the movable flexible layer, wherein an interferometric modulating cavity is defined by the movable reflector and the fixed reflector, the movable reflector being movable between at least a first position and a second position; and

a thermal expansion balancing layer on a side of the movable flexible layer opposite the movable reflector, wherein the thermal expansion balancing layer has a coefficient of thermal expansion greater than or equal to that of the movable flexible layer if a coefficient of thermal expansion of the movable reflector is greater than that of the movable flexible layer, or a coefficient of thermal expansion less than or equal to that of the movable flexible layer if the coefficient of thermal expansion of the movable reflector is less than that of the movable flexible layer.

2. The device of claim 1, wherein the thermal expansion balancing layer contacts the movable flexible layer on an opposite side of the movable flexible layer only from about where the movable reflector is coupled to the movable flexible layer.

3. The device of claim 1, wherein the thermal expansion balancing layer and the movable reflector have a substantially the same coefficient of thermal expansion.

4. The device of claim 3, wherein the thermal expansion balancing layer is substantially the same thickness as the movable reflector.

5. The device of claim 1, further comprising:

a display;

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

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

6. The device of claim 5, further comprising a driver circuit configured to send at least one signal to the display.

7. The device of claim 6, further comprising a controller configured to send at least a portion of the image data to the driver circuit.

8. The device of claim 5, further comprising an image source module configured to send the image data to the processor.

9. The device of claim 8, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

10. The device of claim 5, further comprising an input device configured to receive input data and to communicate the input data to the processor.

11. A device comprising:

first means for reflecting light;

second means for reflecting light, wherein an interferometric modulating cavity is defined by the second reflecting means and the first reflecting means, the second reflecting means being movable between at least a first position and a second position;

means for moving the second reflecting means, the second reflecting means being coupled to the means for moving; and

means for balancing thermal expansion, provided on a side of the means for moving opposite the second reflecting means, wherein the means for balancing thermal expansion has a coefficient of thermal expansion greater than or equal to that of the means for moving if a coefficient of thermal expansion of the second reflecting means is greater than that of the means for moving, or a coefficient of thermal expansion less than or equal to that of the means for moving if the coefficient of thermal expansion of the second reflecting means is less than that of the means for moving.

12. The device of claim 11, wherein the means for balancing thermal expansion contacts the means for moving on an opposite side of the means for moving only from about where the second reflecting means is coupled to the means for moving.

13. The device of claim 11, wherein the means for balancing thermal expansion and the second reflecting means have a substantially the same coefficient of thermal expansion.

14. The device of claim 13, wherein the means for balancing thermal expansion is substantially the same thickness as the second reflecting means.

15. A method of making a device for modulating light, the method comprising:

forming a fixed reflector which is at least partially reflective;

forming a movable flexible layer;

forming a movable reflector which is at least partially reflective, the movable reflector coupled to the movable flexible layer, wherein an interferometric modulating cavity is defined by the movable reflector and the fixed reflector, the movable reflector being movable between at least a first position and a second position; and

forming a thermal expansion balancing layer on a side of the movable flexible layer opposite the movable reflector, wherein the thermal expansion balancing layer has a coefficient of thermal expansion greater than or equal to that of the movable flexible layer if a coefficient of thermal expansion of the movable reflector is greater than that of the movable flexible layer, or a coefficient of thermal expansion less than or equal to that of the movable flexible layer if the coefficient of thermal expansion of the movable reflector is less than that of the movable flexible layer.

16. The method of claim 15, wherein the thermal expansion balancing layer contacts the movable flexible layer on an opposite side of the movable flexible layer only from about where the movable reflector is coupled to the movable flexible layer.

17. The device of claim 15, wherein the thermal expansion balancing layer and the movable reflector have a substantially the same coefficient of thermal expansion.

18. The device of claim 17, wherein the thermal expansion balancing layer is substantially the same thickness as the movable reflector.