MEMS structures, methods of fabricating MEMS components on separate substrates and assembly of same

• US 7,719,752 B2
• Filed: 09/27/2007
• Issued: 05/18/2010
• Est. Priority Date: 05/11/2007
• Status: Expired due to Fees

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Sampsell, Jeffrey Brian, Gally, Brian James, Floyd, Philip Don
• Primary Examiner(s): Choi; William C
• Application Number:
  US11/863,079
• Publication Number:
  US 20080279498A1
• Time in Patent Office: 964 Days
• Field of Search: 359/198, 359/237, 359/247, 359/290, 359/291, 359/315, 438/29
• US Class Current: 359/290
• CPC Class Codes: B81B 2201/042 Micromirrors, not used as optical switches
• CPC Class Codes: B81B 2207/07 Interconnects
• CPC Class Codes: B81B 2207/092 Buried interconnects in the substrate or in the lid
• CPC Class Codes: B81B 3/007 For controlling stiffness, e.g. ribs
• 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
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 5/284 of etalon type comprising a resonant cavity other than a thin solid film, e.g. gas, air, solid plates etalons for fibre optic multiplexing G02B6/29358; etalons for spectral measurement G01J3/26
• CPC Class Codes: H01L 31/04 adapted as photovoltaic [PV] conversion devices testing thereof during manufacture H01L22/00; testing thereof after manufacture H02S50/10
• CPC Class Codes: Y10T 29/49126 Assembling bases

Abstract

Methods of fabricating a microelectromechanical systems (MEMS) device with reduced masking and MEMS devices formed by the same are disclosed. In one embodiment, a MEMS device is fabricated by laminating a front substrate and a carrier, each of which has components preformed thereon. The front substrate is provided with stationary electrodes formed thereover. A carrier including movable electrodes formed thereover is attached to the front substrate. The carrier of some embodiments is released after transferring the movable electrodes to the front substrate. In other embodiments, the carrier stays over the front substrate, and serves as a backplate for the MEMS device. Features are formed by deposition and patterning, by embossing, or by patterning and etching. In some embodiments in which the MEMS device serves as an interferometric modulator, the front substrate is also provided with black masks to prevent or mitigate bright areas in the actuated state of the MEMS device. Static interferometric modulators can also be formed by shaping or preformation and lamination. The methods not only reduce the manufacturing costs, but also provide a higher yield. The resulting MEMS devices can trap smaller volumes between laminated substrates and are less susceptible to pressure variations and moisture leakage.

Claims

1. A method of making a MEMS device, the method comprising:

providing a transparent electrode assembly comprising a transparent substrate and an at least partially transparent electrode formed over the transparent substrate;

providing a carrier with a reflective electrode formed thereover; and

attaching the transparent electrode assembly to the carrier after providing the carrier with the reflective electrode such that the reflective electrode faces the at least partially transparent electrode to form a cavity therebetween, wherein attaching the transparent electrode assembly comprises pressing portions of the reflective electrode against the transparent electrode assembly.

2. The method of claim 1, wherein the MEMS device is an interferometric modulator, and wherein the cavity is configured to interferometrically modulate light.

3. The method of claim 1, wherein the at least partially transparent electrode and the reflective electrode are configured to be capable of relative movement to define a cavity of variable size.

4. The method of claim 1, wherein the reflective electrode is deflectable into the cavity.

5. The method of claim 1, wherein providing the transparent electrode assembly comprises providing supports defining the cavity on the transparent substrate, and forming the at least partially transparent electrode in the cavity.

6. The method of claim 5, wherein attaching the transparent electrode assembly to the carrier comprises attaching the transparent substrate to the carrier such that the supports separate the reflective electrode from the at least partially transparent electrode.

7. The method of claim 5, wherein attaching the transparent electrode assembly to the carrier comprises pressing the carrier against the transparent electrode assembly such that the reflective electrode is supported by the supports, and such that the reflective electrode includes first portions overlying the supports, the first portions having a first thickness;

and second portions neighboring the first portions, the second portions not overlying the supports, the second portions having a second thickness, wherein the second thickness is greater than the first thickness.

8. The method of claim 7, wherein attaching the transparent electrode assembly to the carrier comprises bonding the first portions of the reflective electrode to the supports of the transparent electrode assembly.

9. The method of claim 5, wherein providing the transparent electrode assembly comprises forming the cavity so as to include a bottom surface, wherein attaching the transparent electrode assembly to the carrier comprises orienting the carrier to include a surface facing the cavity of the transparent electrode assembly, the surface being the facing surface most removed from the transparent electrode assembly, and wherein attaching the transparent electrode assembly to the carrier comprises attaching the transparent electrode assembly to the carrier such that a distance between the bottom surface of the cavity and the most removed facing surface of the carrier is between about 6,500 Å

and about 20 μ

m.

10. The method of claim 1, wherein attaching the transparent electrode assembly to the carrier comprises providing the at least partially transparent electrode to serve as a stationary electrode for the MEMS device.

11. A microelectromechanical system (MEMS) device comprising:

a front substrate comprising a plurality of supports defining cavities on a surface of the front substrate;

a second substrate opposing the front substrate; and

a plurality of movable electrodes supported on top of the supports, each of the movable electrodes comprising;

first portions of the movable electrodes overlying the supports, the first portions having a first thickness, wherein the first portions of the movable electrodes are interposed between, and contact both of, the second substrate and the supports of the front substrate; and

second portions of the movable electrodes neighboring the first portions and extending between the first portions, the second portions not overlying the supports, the second portions having a second thickness different from the first thickness.

12. The MEMS device of claim 11, wherein the supports are integrally formed with and of the same material as the front substrate.

13. The MEMS device of claim 11, wherein the supports are formed of a material different from that of the front substrate.

14. The MEMS device of claim 11, wherein the MEMS device comprises interferometric modulators, and wherein the front substrate is formed of a substantially transparent material.

15. The MEMS device of claim 14, further comprising a first plurality of optical stacks formed in the cavities;

and a second plurality of optical stacks interposed between the supports and the first portions of the movable electrodes.

16. The device of claim 15, wherein the first plurality of optical stacks have substantially the same thickness as that of the second plurality of optical stacks.

17. The MEMS device of claim 11, wherein the movable electrodes comprise conductive strips extending parallel to one another, each of the conductive strips being configured to serve as electrodes for multiple interferometric modulators.

18. The device of claim 11, wherein the plurality of supports comprise rails extending laterally in a direction substantially perpendicular to the movable electrodes.

19. The device of claim 11, wherein the second substrate comprises a plurality of rails, each of the rails of the second substrate having a surface facing the cavities of the front substrate, the rails of the second substrate extending substantially parallel to one another, wherein each of the plurality of movable electrodes is interposed between the front substrate and one of the rails of the second substrate.

20. The device of claim 11, wherein the first portions of each of the movable electrodes are bonded to the supports of the front substrate.

21. The MEMS device of claim 11, wherein the second thickness is greater than the first thickness.

22. An array of microelectromechanical systems (MEMS) devices, comprising:

a front substrate comprising a plurality of supports defining cavities on the front substrate, each of the cavities having a bottom surface;

a backplate substantially opposing and overlying the front substrate, the backplate having a surface facing the cavities of the front substrate, the surface being most removed from the front substrate; and

a plurality of mechanical strips interposed between the supports and the surface of the backplate, each of the mechanical strips serving as moving electrodes for multiple MEMS devices,

wherein a distance between the bottom surface of one of the cavities and the most removed surface of the backplate is between about 6,500 Å and

about 20 μ

m.

23. The array of claim 22, wherein the backplate is substantially planar.

24. The array of claim 22, wherein the backplate includes recesses formed into the backplate, the recesses including recess surfaces facing the cavities of the front substrate, the most removed surface being one of the recess surfaces, and wherein the backplate further includes a plurality of back supports extending from the backplate toward the front substrate, the back supports defining the recesses therebetween.

25. The array of claim 24, wherein the plurality of back supports comprise rails extending substantially parallel to one another, the rails defining a plurality of recesses, wherein the device further comprises an excess mechanical material within the plurality of recesses.

26. The array of claim 22, wherein the MEMS devices comprise interferometric modulators.