Electrical latching of microelectromechanical devices

• US 6,813,060 B1
• Filed: 12/09/2002
• Issued: 11/02/2004
• Est. Priority Date: 12/09/2002
• Status: Expired due to Fees

• Current Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Garcia, Ernest J., Sleefe, Gerard E.
• Primary Examiner(s): Dang, Hung Xuan
• Assistant Examiner(s): MARTINEZ, JOSEPH P
• Application Number:
  US10/316,172
• Time in Patent Office: 694 Days
• Field of Search: 359/291, 359/196, 359/237, 359/239
• US Class Current: 359/291
• CPC Class Codes: G09G 3/346 based on modulation of the reflection angle, e.g. micromirrors micromirrors devices per se G02B26/0833

Abstract

Methods are disclosed for row and column addressing of an array of microelectromechanical (MEM) devices. The methods of the present invention are applicable to MEM micromirrors or memory elements and allow the MEM array to be programmed and maintained latched in a programmed state with a voltage that is generally lower than the voltage required for electrostatically switching the MEM devices.

Claims

1. A method for electrically addressing an array of two-state microelectromechanical (MEM) devices, comprising steps for:

(a) switching all of the MEM devices in a column of the array from a first state to a second state;

(b) selecting a set of the MEM devices located at an intersection of at least one row of the array and the column, with the set of MEM devices being in the second state;

(c) switching all the MEM devices in the column of the array, except for the set of the MEM devices, from the second state to the first state; and

(d) repeating steps (a)-(c) for each column of the array.

2. The method of claim 1 wherein the step for switching all of the MEM devices in the column of the array from the first state to the second state comprises applying an actuation voltage to all of the MEM devices in the column of the array for electrostatically switching the MEM devices from the first state to the second state.

3. The method of claim 2 wherein the step for selecting the set of the MEM devices comprises applying a holding voltage to all of the MEM devices in the row of the array, with the holding voltage being of insufficient magnitude to switch any of the MEM devices in the row from the first state to the second state, but being of sufficient magnitude to maintain the set of MEM devices in the second state after removal of the actuation voltage.

4. The method of claim 3 wherein the step for switching all the MEM devices in the column of the array, except for the set of the MEM devices, from the second state to the first state comprises:

(a) removing the actuation voltage from all the MEM devices in the column of the array;

(b) applying a maintaining voltage to all the MEM devices in the column of the array; and

(c) removing the holding voltage from all the MEM devices in the row of the array.

5. The method of claim 3 wherein applying the actuation voltage to all of the MEM devices in the column of the array comprises applying the actuation voltage to a first electrode underlying a moveable member of each MEM device in the column of the array.

6. The method of claim 5 wherein applying the holding voltage to all of the MEM devices in the row of the array comprises applying the holding voltage to a second electrode underlying the moveable member of each MEM device in the row of the array.

7. The method of claim 1 further comprising a step for sensing whether one of the MEM devices in the array is in the first state or in the second state at an instant in time.

8. The method of claim 7 wherein the step for sensing comprises capacitively sensing whether the MEM device is in the first state or in the second state.

9. The method of claim 7 wherein the step for sensing comprises optically sensing whether the MEM device is in the first state or in the second state.

10. The method of claim 1 wherein each MEM device in the array comprises a micromirror or a memory element or both.

11. A method for electrically addressing an array of two-state microelectromechanical (MEM) devices, comprising steps for:

(a) applying an actuation voltage to all of the MEM devices in a column of the array, thereby electrostatically actuating all of the MEM devices in the column;

(b) applying a holding voltage to all of the MEM devices in at least one row of the array, thereby selecting the MEM devices located at an intersection of the row and the column, with the holding voltage being of insufficient magnitude to electrostatically actuate any of the MEM devices in the row, but being of sufficient magnitude to maintain the actuation of the MEM devices located at the intersection of the row and the column when the actuation voltage to the column is removed;

(c) removing the actuation voltage from the column, and applying a maintaining voltage to the column;

(d) removing the holding voltage from the row; and

(e) repeating steps (a)-(d) for each column in the array.

12. The method of claim 11 wherein the step for applying the actuation voltage to all of the MEM devices in the column of the array comprises applying the actuation voltage to a first electrode underlying a moveable member of each MEM device in the column of the array thereby electrostatically changing a position of the moveable member from a first state to a second state.

13. The method of claim 12 wherein the step for applying the holding voltage to all of the MEM devices in the row of the array comprises applying the holding voltage to a second electrode underlying the moveable member of each MEM device in the row of the array.

14. The method of claim 12 wherein the first state is defined by the moveable member being coplanar with a substrate whereon the array is formed.

15. The method of claim 14 wherein the second state is defined by the moveable member being tilted at an angle to the substrate.

16. The method of claim 12 wherein the first state is defined by the moveable member being located in an as-formed position.

17. The method of claim 16 wherein the second state is defined by the moveable member being displaced downward from the as-formed position.

18. The method of claim 12 wherein the first state is defined by the moveable member being oriented at an angle to a substrate whereon the array is formed.

19. The method of claim 18 wherein the second state is defined by the moveable member being oriented at a different angle with respect to the substrate.

20. The method of claim 11 wherein the step for removing the actuation voltage from the column and applying the maintaining voltage to the column comprises removing the actuation voltage from the first electrode and applying the maintaining voltage to the first electrode.

21. The method of claim 11 wherein the step for removing the actuation voltage from the column and applying the maintaining voltage to the column comprises applying the maintaining voltage to another electrode underlying the moveable member of each MEM device in the column of the array.

22. The method of claim 11 further including a step for sensing the position of the moveable member of at least one MEM device in the array for determining a state of the MEM device.

23. The method of claim 22 wherein the step for sensing the position of the moveable member comprises capacitively sensing the position of the moveable member.

24. The method of claim 22 wherein the step for sensing the position of the moveable member comprises optically sensing the position of the moveable member.

25. The method of claim 11 wherein each MEM device in the array comprises a micromirror or a memory element or both.

26. A method for electrically addressing an array of two-state microelectromechanical (MEM) devices formed on a substrate, comprising steps for:

(a) applying an actuation voltage to all of the MEM devices in a column of the array, thereby electrostatically actuating all of the MEM devices in the column to change the position of a moveable member of each MEM device from a first state to a second state;

(b) selecting a set of the MEM devices in the column that will remain in the second state when a maintaining voltage having a magnitude less than the actuation voltage will be later substituted for the actuation voltage by;

(i) applying a holding voltage to at least one row of the array while the actuation voltage is applied to the column, thereby selecting the MEM devices having both the actuation voltage and the holding voltage applied thereto for the set of MEM devices, with the holding voltage being of insufficient magnitude to electrostatically actuate any of the MEM devices in the column, but being of sufficient magnitude to maintain any MEM device in the column to which the holding voltage is applied in the second state when the actuation voltage is no longer present;

(ii) substituting the maintaining voltage for the actuation voltage while retaining the holding voltage in place;

(iii) removing the holding voltage; and

(c) repeating steps (a) and (b) in turn for each additional column in the array.

27. The method of claim 26 wherein each MEM device in the array of MEM devices comprises a micromirror or a memory element or both.