METHODS FOR MEASUREMENT AND CHARACTERIZATION OF INTERFEROMETRIC MODULATORS

• US 20090204350A1
• Filed: 02/06/2009
• Published: 08/13/2009
• Est. Priority Date: 02/11/2008
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Khazeni, Kasra, Mignard, Marc, Govil, Alok
• Granted Patent: US 8,386,201 B2
• Time in Patent Office: Days
• US Class Current: 702/65
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81C 99/0045 End test of the packaged device
• CPC Class Codes: G01D 5/2417 by varying separation
• CPC Class Codes: G01R 31/2829 Testing of circuits in sensor or actuator systems testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844
• CPC Class Codes: G01R 31/2837 Characterising or performance testing, e.g. of frequency response transient response G01R27/28

Abstract

Various methods are described to characterize interferometric modulators or similar devices. Measured voltages across interferometric modulators may be used to characterize transition voltages of the interferometric modulators. Measured currents may be analyzed by integration of measured current to provide an indication of a dynamic response of the interferometric modulator. Frequency analysis may be used to provide an indication of a hysteresis window of the interferometric modulator or mechanical properties of the interferometric modulator. Capacitance may be determined through signal correlation, and spread-spectrum analysis may be used to minimize the effect of noise or interference on measurements of various interferometric modulator parameters.

Claims

1. A method of characterizing the behavior of a microelectromechanical system (MEMS) device, the method comprising:

applying a driving voltage signal to the MEMS device, wherein the MEMS device comprises a movable layer;

measuring a current through the MEMS device as a function of time;

integrating the current over a period of time; and

determining an operational characteristic of the MEMS device based upon the integrated current.

2. The method of claim 1, wherein integrating the current through the MEMS device provides a measure of the charge accumulated on the MEMS device as a function of time.

3. The method of claim 1, wherein the MEMS device comprises an interferometric modulator device, additionally comprising determining a measure of a capacitance of the interferometric modulator device as a function of time by dividing a charge accumulated on the interferometric modulator by the driving voltage signal.

4. The method of claim 2, wherein the MEMS device comprises a movable layer and a fixed layer that together form a capacitor, additionally comprising determining a measure of the position of the movable layer relative the fixed layer based at least in part on a measure of the capacitance as a function of time.

5. The method of claim 4, additionally comprising determining a measure of a damping force acting on the movable layer based at least in part upon the measure of the position of the movable layer.

6. The method of claim 4, additionally comprising determining a measure of a response time of the MEMS device based at least in part upon the measure of the position of the movable layer as a function of time.

7. The method of claim 1, wherein the MEMS device comprises an interferometric modulator.

8. A method of characterizing the dynamic behavior of a microelectromechanical system (MEMS) device, the method comprising:

applying a driving voltage to an MEMS device for a first period of time, the MEMS device comprising a movable electrode and a fixed electrode;

measuring a current through the MEMS device as a function of time over a second period of time, the second period of time comprising at least a portion of the first period of time; and

determining the dynamic behavior of the MEMS device based on an integration of the current.

9. The method of claim 8, determining the dynamic behavior of the MEMS device comprises determining a charge accumulated on the MEMS device as a function of time.

10. The method of claim 8, wherein determining the dynamic behavior of the MEMS device comprises determining a position of a movable electrode of the MEMS device as a function of time.

11. The method of claim 8, wherein determining the dynamic behavior of the MEMS device comprises determining a damping force acting on a movable layer of the MEMS device.

12. The method of claim 8, wherein determining the dynamic behavior of the MEMS device comprises determining an actuation time of the MEMS device.

13. The method of claim 8, additionally comprising determining the second period of time using the measured current.

14. The method of claim 11, wherein determining the second period of time using the measured current comprises determining a beginning of a movement of the movable layer.

15. The method of claim 14, wherein the second period of time extends from a beginning of the first period of time to the beginning of the movement of the movable layer, and wherein providing an indication of the dynamic behavior of the MEMS device comprises determining an initial state of the MEMS device.

16. A method of determining a damping force exerted on a movable layer of a microelectromechanical system (MEMS) device, the method comprising:

applying a driving voltage signal to the MEMS device, wherein the MEMS device comprises a movable layer, and wherein the driving voltage causes the movable layer to move;

measuring a current through the MEMS device as a function of time;

integrating the current over a period of time; and

determining the damping force exerted on the movable layer based on the integrated current.

17. The method of claim 16, wherein determining the damping force exerted on the movable layer as a function of time comprises determining a charge accumulated on the MEMS device as a function of time.

18. The method of claim 16, wherein determining the damping force comprises determining a position of the movable layer as a function of time.

19. The method of claim 16, wherein the MEMS device comprises an interferometric modulator.

20. A device comprising:

a microelectromechanical system (MEMS) device comprising a movable layer; and

circuitry configured to apply a driving voltage signal to the MEMS device to induce movement of the movable layer, measure a current through the MEMS device as a function of time, integrate the current over a period of time, and determine a behavioral characteristic of the MEMS device based on the integrated current.

21. The MEMS device of claim 20, wherein the circuitry is further configured to determine a position of the movable layer.

22. The MEMS device of claim 20, wherein the circuitry is further configured to determine a damping force acting on the movable layer.

23. A device, comprising:

means for inducing movement of a movable layer of a MEMS device;

means for measuring a current through the MEMS device;

means for integrating the current over a period of time; and

means for characterizing a behavior of the MEMS device based upon the integrated current.

24. The device of claim 23, wherein the means for inducing movement comprises circuitry configured to apply a driving voltage to the movable layer of the MEMS device.

25. The device of claim 23, wherein the means for characterizing the behavior of the MEMS device comprises circuitry configured to determine a position of the movable layer.

26. The device of claim 23, wherein the means for characterizing the behavior of the MEMS device comprises circuitry configured to determine a damping force acting on the movable layer.