Device and method for modifying actuation voltage thresholds of a deformable membrane in an interferometric modulator

• US 20060077528A1
• Filed: 08/05/2005
• Published: 04/13/2006
• Est. Priority Date: 09/27/2004
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: IDC, LLC
• Inventors: Floyd, Philip D.
• Granted Patent: US 7,369,296 B2
• Time in Patent Office: Days
• US Class Current: 359/291
• 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

By varying the spacing between a partially-reflective, partially-transmissive surface and a highly reflective surface positioned behind the partially-reflective, partially-transmissive surface, an interferometric modulator selectively creates constructive and/or destructive interference between light waves reflecting off the two surfaces. The spacing can be varied by applying a voltage to create electrostatic attraction between the two surfaces, which causes one or both surfaces to deform and move closer together. In the absence of such attraction, the surfaces are in a relaxed position, where they are farther apart from one another. A actuation voltage is needed to create sufficient electrostatic attraction to cause a surface to deform. The actuation voltage can be modified by implanting ions in a dielectric layer attached to one or both surfaces. Upon the application of a voltage, the ions create a baseline level of repulsion or attraction between the two surfaces, which thus require more or less voltage, respectively, to cause a surface to deform. The degree of ion implantation can be chosen to set the actuation voltage as desired, or the surfaces can be made to deform at a given voltage by appropriately selecting the degree of ion implantation.

Claims

1. A microelectromechanical system, comprising:

a conductor layer;

a mechanical layer separated by a cavity from the conductor layer and configured to move relative to the conductor layer; and

a charged layer comprising an incorporated charged species, the charged layer disposed between the conductor layer and the mechanical layer.

2. The microelectromechanical system of claim 1, wherein the charged layer is connected in fixed relation to one of the conductor layer and the mechanical layer.

3. The microelectromechanical system of claim 2, wherein the charged layer is immovable and directly overlies the conductor layer.

4. The microelectromechanical system of claim 1, wherein the incorporated charged species are ions.

5. The microelectromechanical system of claim 4, wherein the charged layer is an ion implanted dielectric layer.

6. The microelectromechanical system of claim 4, wherein the incorporated charged species are as-deposited ions in the dielectric layer.

7. The microelectromechanical system of claim 4, wherein the incorporated charged species is potassium or phosphorous.

8. The microelectromechanical system of claim 4, wherein the incorporated charged species is a positively-charged ion chosen from the group consisting of sodium ions and lithium ions.

9. The microelectromechanical system of claim 1, wherein the conductor layer is partially transparent to light of optical wavelengths.

10. The microelectromechanical system of claim 1, wherein the mechanical layer is a mirror.

11. The microelectromechanical system of claim 1, wherein the mechanical layer is attached to and disposed in fixed relation to a mirror spaced from the mechanical layer, wherein the mechanical layer is configured to move the mirror relative to the charged layer.

12. The microelectromechanical system of claim 1, wherein the microelectromechanical system is an interferometric light modulating device configured to create constructive and/or destructive interference of light impinging on the mechanical and charged layers.

13. The microelectromechanical system of claim 1, further comprising:

a display;

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

a memory device in electrical communication with the processor.

14. The microelectromechanical system of claim 13, further comprising:

a driver circuit configured to send at least one signal to the display.

15. The microelectromechanical system of claim 14, further comprising:

a controller configured to send at least a portion of the image data to the driver circuit.

16. The microelectromechanical system of claim 13, further comprising:

an image source module configured to send the image data to the processor.

17. The microelectromechanical system of claim 16, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

18. The microelectromechanical system of claim 13, further comprising:

an input device configured to receive input data and to communicate the input data to the processor.

19. The microelectromechanical system of claim 13, further comprising a plurality of interferometric light modulating devices, wherein some of the interferometric light modulating devices comprise the charged layer and other of the interferometric light modulating devices lack the charged layer.

20. The microelectromechanical system of claim 19, wherein the some of the interferometric light modulating devices have conductor layers and mechanical layers configured for producing constructive interference predominately at one frequency and wherein the other of the interferometric light modulating devices have conductor layers and mechanical layers configured for producing constructive interference predominately at one or more other frequencies, wherein the some of the interferometric light modulating devices and the other of the interferometric light modulating devices are grouped to form pixels in the display.

21. A method for modulating electromagnetic radiation, comprising:

providing a plurality of micromechanical devices, each device comprising;

a conductor layer;

a reflective layer parallel to and spaced a distance from the conductor layer while in a relaxed state, the reflective layer configured to move relative to the conductor layer upon being switched to an actuated state; and

a charged layer between the conductor layer and the reflective layer, the charged layer having an incorporated charged species,

wherein the distance for some of the plurality of micromechanical devices is different from other of the plurality of micromechanical devices; and

applying a voltage to the conductor layers and the reflective layers of the micromechanical devices to actuate the micromechanical devices.

22. The method of claim 21, wherein applying the voltage to the conductor layers and the reflective layers of the micromechanical devices to actuate the micromechanical devices comprises:

applying the voltage to the conductor layers and the reflective layers of the some of the micromechanical devices to actuate the some of the micromechanical devices; and

applying the same voltage to the conductor layers and the reflective layers of the other of the micromechanical devices to actuate the other of the micromechanical devices.

23. The method of claim 21, wherein applying the voltage and applying the same voltage alters an interference behavior of electromagnetic waves impinging on the conductor layers and the reflective layers.

24. The method of claim 21, wherein applying the voltage and applying the same voltage produces constructive interference centered at one or more desired light frequencies.

25. A method for fabricating a micromechanical device, comprising:

forming a first conductive layer;

forming a dielectric layer over the first conductive layer;

adding a charged species to the dielectric layer; and

forming a second conductive layer over the dielectric layer.

26. The method of claim 25, wherein adding the charged species comprises performing an ion implantation after forming the dielectric layer.

27. The method of claim 26, further comprising annealing the dielectric layer after adding the charged species.

28. The method of claim 25, wherein adding charge comprises directing ions to the dielectric as the dielectric is formed.

29. The method of claim 28, wherein adding the charged species comprises simultaneously sputtering an ion precursor and one or more dielectric precursors.

30. The method of claim 25, wherein adding the charged species comprises doping the dielectric layer.

32. The method of claim 25, wherein the charge is provided by implanting ions chosen from the group consisting of potassium and phosphorous ions.

33. The method of claim 25, wherein the charge is provided by implanting ions chosen from the group consisting of sodium ions and lithium ions.

34. The method of claim 25, wherein forming the first conductive layer comprises depositing a layer of chromium and/or indium-tin-oxide.

35. The method of claim 34, wherein forming the dielectric layer comprises depositing an oxide.

36. The method of claim 35, wherein the oxide is chosen from the group consisting of aluminum oxide and/or silicon oxide.

37. The method of claim 35, further comprising depositing a layer of a sacrificial material over the dielectric layer and subsequently forming the second conductive layer.

38. The method of claim 37, wherein forming the second conductive layer comprises depositing a metallic layer over the sacrificial material.

39. The method of claim 38, further comprising preferentially removing the sacrificial material.

40. The method of claim 25, wherein the micromechanical device is an interferometric modulator.

41. A micromechanical device formed by the method of claim 25.

31. The method of claim 31, wherein doping the dielectric layer comprises diffusing dopants into the dielectrtic layer.

42. An interferometric modulator, comprising:

a conductor layer;

a movable layer; and

a means for modifying a voltage actuation threshold of the movable layer with a charged species.

43. The interferometric modulator of claim 42, wherein the means comprises ions incorporated into a dielectric disposed between and immediately adjacent one of the conductor and the movable layers.

44. The interferometric modulator of claim 42, wherein the charged species comprise ions.