System and method for micro-electromechanical operation of an interferometric modulator

• US 8,115,988 B2
• Filed: 09/30/2008
• Issued: 02/14/2012
• Est. Priority Date: 07/29/2004
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Chui, Clarence, Gally, Brian J, Tung, Ming-Hau, Cummings, William J
• Primary Examiner(s): Mack, Ricky
• Assistant Examiner(s): Tra, Tuyen
• Application Number:
  US12/241,600
• Publication Number:
  US 20090022884A1
• Time in Patent Office: 1,232 Days
• Field of Search: 359/291, 359/292, 359/295, 359/220, 359/223, 359/224, 359/320, 359/324, 438/381, 438/396, 438/397, 438/652
• US Class Current: 359/291
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured surface
• 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

An interferometric modulator is formed by a stationary layer and a mirror facing the stationary layer. The mirror is movable between the undriven and driven positions. Landing pads, bumps or spring clips are formed on at least one of the stationary layer and the mirror. The landing pads, bumps or spring clips can prevent the stationary layer and the mirror from contacting each other when the mirror is in the driven position. The spring clips exert force on the mirror toward the undriven position when the mirror is in the driven position and in contact with the spring clips.

Claims

1. A method of making a microelectromechanical system (MEMS) device, comprising:

forming a first electrode;

depositing a dielectric material over at least a portion of the first electrode;

removing a portion of the dielectric material from over the first electrode, thereby forming a variable thickness dielectric layer having a thickness variation that varies across the first electrode, wherein the thickness variation is manifested as peaks and valleys with the distance between the top of the peak and the bottom of the valley being in the range of 100 Å

to 3,000 Å

; and

forming a second electrode over at least a portion of the variable thickness dielectric layer.

2. The method of claim 1, further comprising depositing a sacrificial layer over at least a portion of the dielectric material.

3. The method of claim 2 in which the MEMS device comprises an interferometric modulator.

4. The method of claim 2 in which the second electrode comprises a surface facing the variable thickness dielectric layer, the surface of the second electrode facing the variable thickness dielectric layer having an average peak-to-valley surface profile variation that is less than an average peak-to-valley surface profile variation of the variable thickness dielectric layer.

5. The method of claim 1 in which the dielectric material comprises at least a first layer and a second layer.

6. The method of claim 5 in which the first layer has a first thickness that is greater than a second thickness of the second layer.

7. The method of claim 6 in which the first thickness is in the range of about 200 Å

to about 3000 Å

.

8. The method of claim 6 in which the second thickness is in the range of about 50 Å

to about 500 Å

.

9. The method of claim 5, further comprising patterning the dielectric material to define stops.

10. The method of claim 9 in which removing a portion of the dielectric material comprises removing a portion of the second layer of the dielectric material such that the stops remain.

11. The method of claim 10, further comprising depositing a sacrificial layer over at least a portion of the dielectric material.

12. The method of claim 11, further comprising removing the sacrificial layer and at least a portion of the first layer of the dielectric material.

13. The method of claim 12 in which removing the sacrificial layer and the at least a portion of the first layer of the dielectric material further comprises etching with an etchant.

14. The method of claim 13 in which etching further comprises removing the first layer of the dielectric material at a first etch rate that is higher than a second etch rate for removing the second layer.

15. The method of claim 1 in which the dielectric material is compositionally graded.

16. The method of claim 15 in which the dielectric material is a graded dielectric material selected from the group consisting of graded silicon oxide and graded silicon nitride.

17. The method of claim 16 in which the graded dielectric material at an interface with the first electrode is enriched in Si relative to the overall composition of the graded dielectric material.

18. The method of claim 1, further comprising depositing an intermediate layer over the at least a portion of the first electrode.

19. The method of claim 18 in which the intermediate layer comprises at least one of an optical layer, a barrier layer or a non-conductive layer.

20. The method of claim 18, comprising depositing the dielectric material over the intermediate layer.

21. A method of making an interferometric modulator, comprising:

forming a first electrode;

depositing a dielectric layer over at least a portion of the first electrode;

removing a portion of the dielectric layer to form a variable thickness dielectric layer having a thickness variation that varies across the first electrode, wherein the thickness variation is manifested as peaks and valleys with the distance between the top of the peak and the bottom of the valley being in the range of 100 Å

to 3,000 Å

;

depositing a sacrificial layer over the variable thickness dielectric layer;

planarizing the sacrificial layer; and

forming a second electrode over the sacrificial layer.

22. The method of claim 21 further comprising forming a planarization layer over the sacrificial layer.

23. The method of claim 21 further comprising removing the sacrificial layer.

24. The method of claim 21 in which the variable thickness dielectric layer comprises at least one stop.

25. The method of claim 21 in which the second electrode comprises a lower surface at an interface with the sacrificial layer, the lower surface of the second electrode having an average peak-to-valley surface profile variation that is less than an average peak-to-valley surface profile variation of the variable thickness dielectric layer.

26. A method of making an interferometric modulator, comprising:

forming a first electrode;

depositing a dielectric layer over at least a portion of the first electrode;

removing a portion of the dielectric layer to form a variable thickness dielectric layer having a thickness variation that varies across the first electrode, wherein the thickness variation is manifested as peaks and valleys with the distance between the top of the peak and the bottom of the valley being in the range of 100 Å

to 3,000 Å

;

depositing a sacrificial layer over the a variable thickness dielectric layer;

depositing a planarization layer over the sacrificial layer; and

forming a second electrode over the planarization layer.

27. The method of claim 26 further comprising removing the sacrificial layer.

28. The method of claim 26 further comprising planarizing the sacrificial layer.

29. The method of claim 26 in which the variable thickness dielectric layer comprises at least one stop.

30. The method of claim 26 in which the second electrode comprises a lower surface at an interface with the planarization layer, the lower surface of the second electrode having an average peak-to-valley surface profile variation that is less than an average peak-to-valley surface profile variation of the variable thickness dielectric layer.