ELECTROMECHANICAL DEVICE CONFIGURED TO MINIMIZE STRESS-RELATED DEFORMATION AND METHODS FOR FABRICATING SAME

• US 20100265563A1
• Filed: 06/28/2010
• Published: 10/21/2010
• Est. Priority Date: 08/19/2005
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Kogut, Lior, Zhong, Fan
• Granted Patent: US 8,229,253 B2
• Time in Patent Office: Days
• US Class Current: 359/290
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81B 2203/0163 Spring holders
• CPC Class Codes: B81B 2203/019 characterized by their profile
• CPC Class Codes: B81B 2203/0307 Anchors
• CPC Class Codes: B81B 2203/053 Translation according to an axis perpendicular to the substrate
• CPC Class Codes: B81B 3/0072 For controlling internal stress or strain in moving or flexible elements, e.g. stress compensating layers
• CPC Class Codes: B81C 1/00142 Bridges deformable micromirrors G02B26/0841
• CPC Class Codes: B81C 1/00666 Treatments for controlling internal stress or strain in MEMS structures
• CPC Class Codes: B81C 2201/0167 by adding further layers of materials having complementary strains, i.e. compressive or tensile strain
• 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: Y10S 359/90 Methods

Abstract

Embodiments of MEMS devices include a movable layer supported by overlying support structures, and may also include underlying support structures. In one embodiment, the residual stresses within the overlying support structures and the movable layer are substantially equal. In another embodiment, the residual stresses within the overlying support structures and the underlying support structures are substantially equal. In certain embodiments, substantially equal residual stresses are be obtained through the use of layers made from the same materials having the same thicknesses. In further embodiments, substantially equal residual stresses are obtained through the use of support structures and/or movable layers which are mirror images of one another.

Claims

1. An electromechanical device, comprising:

a substrate;

an electrode layer located over the substrate; and

a movable layer located over the electrode layer, wherein the movable layer is generally spaced apart from the electrode layer by an air gap, wherein the movable layer comprises;

a reflective sublayer on the side of the movable layer facing the electrode layer, the reflective sublayer having a residual internal stress;

a mechanical sublayer; and

an upper sublayer on the opposite side of the mechanical sublayer from the reflective sublayer, the upper sublayer having a residual internal stress;

wherein the residual internal stress of the reflective sublayer is balanced by the residual internal stress of the upper sublayer.

2. The electromechanical device of claim 1, wherein the reflective sublayer and the upper sublayer comprise substantially the same material.

3. The electromechanical device of claim 2, wherein the reflective sublayer and the upper sublayer have substantially the same thickness.

4. The electromechanical device of claim 1, wherein the coefficient of thermal expansion of the reflective sublayer is substantially equal to the coefficient of thermal expansion of the upper sublayer.

5. The electromechanical device of claim 1, further comprising at least one underlying support structure underlying the movable layer.

6. The electromechanical device of claim 5, further comprising at least one overlying support structure overlying the movable layer, wherein the overlying support structure substantially overlies the underlying support structure, and wherein a residual stress in the overlying support structure is substantially balanced by a residual stress in the underlying support structure.

7. The electromechanical device of claim 6, wherein the overlying support structure and the underlying support structure comprise substantially the same material

8. The electromechanical device of claim 1, further comprising a partially reflective layer located on the same side of the air gap as the electrode layer.

9. The electromechanical device of claim 1, wherein the MEMS device comprises an interferometric modulator.

10. The electromechanical device of claim 1, additionally comprising:

a processor that is configured to communicate with at least one of said electrode layer and said movable layer, said processor being configured to process image data; and

a memory device that is configured to communicate with said processor.

11. The electromechanical device of claim 10, further comprising a driver circuit configured to send at least one signal to at least one of said electrode layer and said movable layer.

12. The electromechanical device of claim 11, further comprising a controller configured to send at least a portion of the image data to the driver circuit

13. The electromechanical device of claim 10, further comprising an image source module configured to send said image data to said processor.

14. The electromechanical device of claim 13, wherein the image source module comprises at least one of a receiver, transceiver, and transmitter.

15. The electromechanical device of claim 10, further comprising an input device configured to receive input data and to communicate said input data to said processor.

16. A method of fabricating an electromechanical device, comprising:

providing a substrate;

depositing an electrode layer over the substrate;

depositing a sacrificial layer over the electrode layer;

patterning the sacrificial layer to form apertures; and

depositing a movable layer over the patterned sacrificial layer, wherein depositing a movable layer comprises;

depositing a reflective sublayer, wherein the reflective sublayer comprises a material having an internal residual stress;

depositing a mechanical sublayer over the reflective sublayer; and

depositing an upper sublayer over the mechanical sublayer, wherein the upper sublayer comprises a material having an internal residual stress, and wherein the residual internal stress of the reflective sublayer is balanced by the residual internal stress of the upper sublayer.

17. The method of claim 16, additionally comprising etching the sacrificial layer to remove the sacrificial layer, thereby forming a cavity between the movable layer and the electrode layer.

18. The method of claim 16, wherein the reflective sublayer and the upper sublayer comprise substantially the same material.

19. The method of claim 18, wherein the reflective sublayer and the upper sublayer have substantially the same thickness.

20. The method of claim 16, additionally comprising forming a layer of partially reflective material over the substrate prior to forming the sacrificial layer.