Method of improving the performance of microstructures

• US 7,034,982 B2
• Filed: 04/13/2004
• Issued: 04/25/2006
• Est. Priority Date: 04/13/2004
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Reflectivity, Inc. (Texas Instruments, Inc.)
• Inventors: Doan, Jonathan
• Primary Examiner(s): Ben, Loha
• Application Number:
  US10/823,823
• Publication Number:
  US 20050225832A1
• Time in Patent Office: 742 Days
• Field of Search: 359/290, 359/291, 359/298, 359292-295, 438/24, 438/48, 438/50, 438/51, 438/52, 438/53, 438/733, 216/2, 216/11, 216/13, 216/24, 257/80, 257/82, 257/415, 257/678, 356/218, 356/445
• US Class Current: 359/290
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B

Abstract

A plastically deformable element of a microelectromechanical device is strained so as to improve the lifetime of the microelectromechanical device. The element of the device can be strained by deforming the element into a deformed state and holding the element at the deformed state for a particular time period so as to acquire an amount of plastic deformation. The operation states of the device are calibrated according to the states before straining and the acquired plastic deformation. After then, the device is operated in the calibrated states.

Claims

1. A method for improving the performance of a device having a movable microstructure that comprises a deformable element that plastically deforms and operates in a first deformed state and a second state, the method comprising:

repeatedly actuating the element to the first deformed state;

or holding the element at the first deformed state for a particular time period so as to cause the element to acquire an amount of plastic deformation that is at least 1.5% of a predetermined maximum plastic deformation that can be developed during the operation of the element; and

delivering the device to a customer.

2. The method of claim 1, wherein the predetermined maximum plastic deformation is an amount of plastic deformation developed after at least 10,000 hours of operation of the element.

3. The method of claim 2, wherein the customer is a projection system manufacture.

4. The method of claim 1, wherein the predetermined maximum plastic deformation is equivalent to a droop angle for the element of 0.8°

or more.

5. The method of claim 1, wherein the step of repeatedly actuating the element further comprises:

repeatedly actuating the element to the first deformed state in response to a series of signals each corresponding to an ON state so as to achieve a maximized brightness.

6. The method of claim 1, wherein the customer is a retail customer and the microstructure is a micromirror within a spatial light modulator of a projection system.

7. The method of claim 6, further comprising:

heating the microstructure to a temperature of from 20°

C. to 120°

C. during the step of repeatedly actuating the element or holding the element at the first deformed state.

8. The method of claim 6, further comprising:

heating the microstructure to a temperature of from 120°

C. to 200°

C. during the step of repeatedly actuating the element or holding the element at the first deformed state.

9. The method of claim 6, further comprising:

heating the microstructure to a temperature of from 200°

C. to 500°

C.

10. The method of claim 1, wherein the element comprises an early transition metal nitride.

11. The method of claim 1, wherein the step of repeatedly actuating the element further comprising:

repeatedly actuating the element that is a hinge of a micromirror device, the hinge having a mirror plate attached thereto such that the mirror plate is operable to rotate.

12. The method of claim 1, wherein the step of holding the element at the deformed state for the particular time period further comprises:

holding the element at the deformed state for a particular time period of from 5 minutes to 500 hours.

13. The method of claim 1, wherein the step of holding the element at the deformed state for the particular time period further comprises:

holding the element at the deformed state for a particular time period of from 20 minutes to 24 hours.

14. The method of claim 1, further comprising:

obtaining a development of plastic deformation in the element over time; and

determining the particular time period according to the obtained development of the plastic deformation.

15. The method of claim 14, wherein the step of determining the particular time period further comprises:

determining an initial amount of the plastic deformation that is developed during a first time period and is at least 1% of the maximum plastic deformation that can be developed by the deformable element; and

determining the particular time period for holding the element at the deformed state according to the first time period such that after holding the element for the particular time period, the acquired deformation encompasses the initial amount of the plastic deformation.

16. The method of claim 1, wherein the initial amount of the plastic deformation is at least 3% or more of the maximum plastic deformation.

17. The method of claim 1, wherein the initial amount of the plastic deformation is at least 5% or more of the maximum plastic deformation.

18. The method of claim 1, wherein the initial amount of the plastic deformation is at least 60% or more of the maximum plastic deformation.

19. The method of claim 1, further comprising:

packaging the microstructure before performing the steps of deforming the element.

20. The method of claim 1, further comprising:

packaging the microstructure after the steps of defining the new non-deformed state.

21. The method of claim 1, wherein the step of deforming the element to the deformed state further comprises:

rotating a mirror plate that is attached to the deformable element to an ON state angle on a substrate, wherein the ON state angle is from 10°

to 18°

between the mirror plate and the substrate.

22. The method of claim 1, wherein the deformable element comprises a material that is an elemental metal, metalloid, metallic compound or ceramic.

23. The method of claim 1, wherein the deformable element comprises a material that is polycrystalline, amorphous or nanocrystalline.

24. A method for improving the performance of a device having a movable microstructure that comprises a deformable element that plastically deforms and operates in a first deformed state and a second state, the method comprising:

predetermining an amount of desired plastic deformation of the element at a non-actuated state;

repeatedly actuating the element to a first deformed state;

or holding the element at the first deformed state for a particular time period so as to cause the element to acquire the desired amount of plastic deformation at the non-actuated state; and

delivering the device to a customer.

25. The method of claim 24, wherein the step of repeatedly actuating the element further comprises:

repeatedly actuating the element to the first deformed state in response to a series of signals each corresponding to an ON state so as to achieve a maximized brightness.

26. The method of claim 24, wherein the customer is a retail customer.

27. The method of claim 24, wherein the step of repeatedly actuating the element further comprising:

repeatedly actuating the element that is a hinge of a micromirror device, the hinge having a mirror plate attached thereto such that the mirror plate is operable to rotate.

28. The method of claim 24, wherein the step of holding the element at the deformed state for the particular time period further comprises:

holding the element at the deformed state for a particular time period of from 5 minutes to 500 hours.

29. The method of claim 28, further comprising:

heating the microstructure to a temperature of from 20°

C. to 120°

C. during the step of repeatedly actuating the element or holding the element at the first deformed state.

30. The method of claim 29, wherein the step of determining the particular time period further comprises:

determining an initial amount of the plastic deformation that is developed during a first time period and is at least 1% of the maximum plastic deformation that can be developed by the deformable element; and

determining the particular time period for holding the element at the deformed state according to the first time period such that after holding the element for the particular time period, the acquired deformation encompasses the initial amount of the plastic deformation.

31. The method of claim 28, further comprising:

heating the microstructure to a temperature of from 120°

C. to 200°

C. during the step of repeatedly actuating the element or holding the element at the first deformed state.

32. The method of claim 31, wherein the initial amount of the plastic deformation is at least 3% or more of the maximum plastic deformation.

33. The method of claim 31, wherein the initial amount of the plastic deformation is at least 5% or more of the maximum plastic deformation.

34. The method of claim 31, wherein an initial amount of the plastic deformation is at least 60% or more of the maximum plastic deformation.

35. The method of claim 28, further comprising:

heating the microstructure to a temperature of from 200°

C. to 500°

C. during the step of repeatedly actuating the element or holding the element at the first deformed state.

36. The method of claim 24, wherein the step of holding the element at the deformed state for the particular time period further comprises:

holding the element at the deformed state for a particular time period of from 20 minutes to 24 hours.

37. The method of claim 24, further comprising:

obtaining a development of plastic deformation in the element over time; and

determining the particular time period according to the obtained development of the plastic deformation.

38. The method of claim 29, wherein the step of determining the pattern further comprises:

determining an initial amount of the plastic deformation that is developed during a first time period and is at least 1.5% or more of the maximum plastic deformation.

39. The method of claim 24, further comprising:

packaging the microstructure before performing the steps of deforming the element.

40. The method of claim 24, further comprising:

packaging the microstructure after the steps of defining the new non-deformed state.

41. The method of claim 24, wherein the step of deforming the element to the deformed state further comprises:

rotating a mirror plate that is attached to the deformable element to an ON state angle on a substrate, wherein the ON state angle is from 10°

to 18°

between the mirror plate and the substrate.

42. The method of claim 24, wherein the deformable element comprises a material that is an elemental metal, metalloid, metallic compound, or ceramic.

43. The method of claim 42, wherein the particular time period is from 1 to 24 hours.

44. The method of claim 24, wherein the deformable element comprises a material that is polycrystalline, amorphous or nanocrystalline.

45. The method of claim 44, further comprising:

raising the temperature of the microstructure to a value of from 20°

to 120°

C. during the step of repeatedly actuating the element or holding the element at the first deformed state.

46. The method of claim 44, further comprising:

raising the temperature of the microstructure to a value of from 120°

to 200°

C. during the step of repeatedly actuating the element or holding the element at the first deformed state.

47. The method of claim 44, further comprising:

raising the temperature of the microstructure to a value of from 200°

to 500°

C. during the step of repeatedly actuating the element or holding the element at the first deformed state.

48. A method for improving the performance of a device having a movable microstructure that comprises an element that plastically deforms and operates in a first deformed state and a second state, the method comprising:

acquiring an amount of plastic deformation, comprising;

repeatedly actuating the element to the first deformed state;

or holding the element at the

first deformed state for a time period of 1 hour or more so as to cause the element to acquire an amount of plastic deformation; and

shipping the device to a customer.

49. The method of claim 48, wherein the step of acquiring the amount of plastic deformation further comprises:

holding the element at the first deformed state for a time period of 10 hours or more.

50. The method of claim 49, wherein the step of deforming the element to the deformed state further comprises:

rotating a mirror plate that is attached to the deformable element to an ON state angle on a substrate, wherein the ON state angle is from 10°

to 18°

between the mirror plate and the substrate.

51. The method of claim 49, wherein the particular time period is from 5 minutes to 800 hours.

52. The method of claim 48, wherein the step of acquiring the amount of plastic deformation further comprises:

holding the element at the first deformed state for a time period of 50 hours or more.

53. The method of claim 52, wherein the step of determining the particular time period further comprises:

determining an initial amount of the plastic deformation that is developed during a first time period and is at least 1% of the maximum plastic deformation that can be developed by the deformable element; and

determining the particular time period for holding the element at the deformed state according to the first time period such that after holding the element for the particular time period, the acquired deformation encompasses the initial amount of the plastic deformation.

54. The method of claim 48, wherein the step of acquiring the amount of plastic deformation further comprises:

holding the element at the first deformed state for a time period of 100 hours or more.

55. The method of claim 54, wherein an initial amount of the plastic deformation is at least 3% or more of the maximum plastic deformation.

56. The method of claim 54, wherein an initial amount of the plastic deformation is at least 5% or more of the maximum plastic deformation.

57. The method of claim 54, wherein an initial amount of the plastic deformation is at least 60% or more of the maximum plastic deformation.

58. The method of claim 48, wherein the step of repeatedly actuating the element further comprises:

repeatedly actuating the element to the first deformed state in response to a series of signals each corresponding to an ON state so as to achieve a maximized brightness.

59. The method of claim 48, further comprising:

obtaining a development of plastic deformation in the element over time; and

determining the particular time period according to the obtained development of the plastic deformation.

60. The method of claim 48, wherein the deformable element comprises a material that is an elemental metal, metalloid, metallic compound or ceramic.

61. The method of claim 48, wherein the deformable element comprises a material that is polycrystalline, amorphous or nanocrystalline.

62. The method of claim 48, further comprising:

packaging the microstructure before performing the steps of acquiring the amount of plastic deformation.

63. The method of claim 48, further comprising:

packaging the microstructure after the steps of acquiring the amount of plastic deformation.

64. A method of improving the lifetime of a spatial light modulator having an array of micromirrors, wherein each micromirror comprises a reflective mirror plate attached to a deformable hinge such that the mirror plate can rotate between an ON and OFF state, the method comprising:

acquiring an amount of plastic deformation for the deformable hinge of one of the micromirrors of the array;

defining a new OFF state according to the original OFF state and the acquired plastic deformation; and

operating said one of the micromirrors of the array at the new OFF state and the ON state.

65. The method of claim 64, wherein the step of acquiring the amount of plastic deformation further comprises:

setting the mirror plates to a deformed state; and

holding the mirror plates at the deformed state for a particular time period.

66. The method of claim 65, wherein the step of holding the mirror plates at the deformed state for the particular time period further comprises:

holding the mirror plates at the deformed state for a particular time period of from 5 minutes to 500 hours.

67. The method of claim 65, wherein the step of holding the mirror plates at the deformed state for the particular time period further comprises:

holding the mirror plates at the deformed state for a particular time period of from 20 minutes to 24 hours.

68. The method of claim 65, further comprising;

heating the micromirrors to a temperature of from 20°

C. to 120°

C. during repeatedly actuating or holding the mirror plates at the deformed state.

69. The method of claim 65, further comprises:

heating the micromirrors to a temperature of from 120°

C. to 200°

C. during repeatedly actuating or holding the mirror plates at the deformed state.

70. The method of claim 65, further comprising:

heating the micromirrors to a temperature of from 200°

C. to 500°

C. during repeatedly actuating or holding the mirror plates at the deformed state.

71. The method of claim 65, wherein the step of setting the mirror plates to the deformed state further comprises:

rotating a mirror plate that is attached to the deformable hinge to an ON state angle on a substrate, wherein the ON state angle is from 10°

to 18°

between the mirror plate and the substrate.

72. The method of claim 64, further comprising:

calibrating the micromirror based on the new OFF state such that the micromirror can be operated in the ON state and the new OFF state.

73. The method of claim 64, further comprising:

obtaining a development of plastic deformation in the deformable hinge over time; and

determining a particular time period according to the obtained development of the plastic deformation.

74. The method of claim 73, wherein the step of determining the particular time period further comprises:

determining an initial amount of the plastic deformation that is developed during a first time period and is at least 1% of the developed maximum plastic deformation; and

determining the particular time period for holding the mirror plate at the deformed state according to the first time period such that after holding the mirror plate for the particular time period, the acquired deformation encompasses the initial amount of the plastic deformation.

75. The method of claim 74, wherein the initial amount of the plastic deformation is at least 1.5% or more of the maximum plastic deformation.

76. The method of claim 75, wherein the initial amount of the plastic deformation is at least 3% or more of the maximum plastic deformation.

77. The method of claim 76, wherein the initial amount of the plastic deformation is at least 5% or more of the maximum plastic deformation.

78. The method of claim 77, wherein the initial amount of the plastic deformation is at least 60% or more of the maximum plastic deformation.

79. The method of claim 64, further comprising:

packaging the micromirror before performing the steps of acquiring the amount of plastic deformation.

80. The method of claim 64, further comprising:

packaging the micromirror after the steps of acquiring the amount of plastic deformation.

81. The method of claim 64, wherein the deformable hinge comprises a material that is an elemental metal, metalloid, metallic compound or ceramic.

82. The method of claim 64, wherein the deformable hinge comprises a material that is polycrystalline, amorphous or nanocrystalline.