Resonant biaxial MEMS reflector with piezoelectric actuators, and projective MEMS system including the same

• US 10,225,530 B2
• Filed: 11/07/2017
• Issued: 03/05/2019
• Est. Priority Date: 11/30/2015
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Giusti, Domenico, Carminati, Roberto
• Primary Examiner(s): Cherry, Euncha P
• Application Number:
  US15/805,705
• Publication Number:
  US 20180063492A1
• Time in Patent Office: 483 Days
• Field of Search: 3592008
• CPC Class Codes: B81B 3/0045 Improve properties related to angular swinging, e.g. control resonance frequency
• CPC Class Codes: G02B 26/0858 the reflecting means being moved or deformed by piezoelectric means
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: G02B 26/105 with one or more pivoting mirrors or galvano-mirrors G02B26/101 takes precedence
• CPC Class Codes: G02B 7/1821 for rotating or oscillating mirrors
• CPC Class Codes: H04N 9/3135 Driving therefor
• CPC Class Codes: H04N 9/3173 wherein the projection device is specially adapted for enhanced portability

Abstract

A MEMS device includes a fixed structure and a mobile structure with a reflecting element coupled to the fixed structure through at least a first deformable structure and a second deformable structure. Each of the first and second deformable structures includes a respective number of main piezoelectric elements, with the main piezoelectric elements of the first and second deformable structures configured to be electrically controlled for causing oscillations of the mobile structure about a first axis and a second axis, respectively. The first deformable structure further includes a respective number of secondary piezoelectric elements configured to be controlled so as to vary a first resonance frequency of the mobile structure about the first axis.

Claims

1. A MEMS device, comprising:

a fixed structure made at least in part of semiconductor material;

a mobile structure including a reflecting element;

a first deformable structure coupled between the fixed structure and the mobile structure; and

a second deformable structure coupled between the fixed structure and the mobile structure;

wherein each of the first and second deformable structures comprises a respective bottom electrode region;

wherein each of the first and second deformable structures has a respective main body having an elongated shape along a respective direction of elongation;

wherein each of the first and second deformable structures comprises a plurality of main piezoelectric elements mechanically coupled to said respective main body and arranged in the direction of elongation of said respective main body;

the main piezoelectric elements of the first deformable structure extending on top of the bottom electrode region of the first deformable structure and being electrically controllable to cause a deformation of the first deformable structure along with an oscillation of the mobile structure about a first axis;

the main piezoelectric elements of the second deformable structure extending on top of the bottom electrode region of the second deformable structure and being electrically controlled to causing a deformation of the second deformable structure along with an oscillation of the mobile structure about a second axis; and

wherein the reflecting element is greater than each of the plurality of main piezoelectric elements in length and width.

8. The MEMS device of claim 1, wherein each of the first and second deformable structures further has a respective connection portion extending from the main body and coupled to the mobile structure.

9. The MEMS device of claim 8, wherein the connection portion extends perpendicular to the respective direction of elongation of the main body.

10. The MEMS device of claim 1, wherein each of the first and second deformable structures comprises a respective semiconductor region.

2. A MEMS device comprising:

a fixed structure;

a mobile structure including a reflecting element;

a first deformable structure coupled between the fixed structure and the mobile structure; and

a second deformable structure coupled between the fixed structure and the mobile structure;

wherein each of the first and second deformable structures has a respective main body having an elongated shape along a respective direction of elongation;

wherein each of the first and second deformable structures comprises a plurality of main piezoelectric elements mechanically coupled to said respective main body and arranged in the direction of elongation of said respective main body;

the main piezoelectric elements of the first deformable structure being electrically controllable to cause a deformation of the first deformable structure along with an oscillation of the mobile structure about a first axis;

the main piezoelectric elements of the second deformable structure being electrically controlled to causing a deformation of the second deformable structure along with an oscillation of the mobile structure about a second axis; and

wherein the first deformable structure further comprises secondary piezoelectric elements mechanically coupled to said respective main body, the secondary piezoelectric elements being electrically controlled to cause a further deformation of the first deformable structure which varies a first resonance frequency of the oscillation of the mobile structure about the first axis.

3. The MEMS device of claim 2, wherein the main piezoelectric elements and the secondary piezoelectric elements are interspersed with one another in said direction of elongation of said respective main body.

4. The MEMS device of claim 3, wherein the secondary piezoelectric elements each have an elongated shape extending in a direction transverse to the direction of elongation of said main body.

5. The MEMS device of claim 2, wherein the second deformable structure further comprises secondary piezoelectric elements mechanically coupled to said respective main body, the secondary piezoelectric elements being electrically controlled to cause a further deformation of the second deformable structure which varies a second resonance frequency of the oscillation of the mobile structure about the second axis.

6. The MEMS device of claim 5, wherein the main piezoelectric elements and the secondary piezoelectric elements are interspersed with one another in said direction of elongation of said respective main body.

7. The MEMS device of claim 6, wherein the secondary piezoelectric elements each have an elongated shape extending in a direction transverse to the direction of elongation of said main body.

16. The MEMS device of claim 2, wherein each of the first and second deformable structures further has a respective connection portion extending from the main body and coupled to the mobile structure.

17. The MEMS device of claim 16, wherein the connection portion extends perpendicular to the respective direction of elongation of the main body.

18. The MEMS device of claim 2,

wherein said fixed structure is made at least in part of semiconductor material;

and

wherein each of the first and second deformable structures comprises a respective bottom electrode region;

wherein the main piezoelectric elements of the first deformable structure extend on top of the bottom electrode region of the first deformable structure; and

wherein the main piezoelectric elements of the second deformable structure extend on top of the bottom electrode region of the second deformable structure.

19. The MEMS device of claim 18, wherein each of the first and second deformable structures comprises a respective semiconductor region.

11. A MEMS device, comprising:

a fixed structure;

a mobile structure with a reflecting element coupled to the fixed structure through at least a first deformable structure and a second deformable structure, wherein each of the first and second deformable structures includes a respective main body having an elongated shape along a respective direction of elongation;

a plurality of main piezoelectric elements mounted to the main body of each of the first and second deformable structures along said direction of elongation, said main piezoelectric elements configured to be electrically controlled for causing oscillations of the mobile structure about a first axis and a second axis, respectively; and

a plurality of secondary piezoelectric elements mounted to the main body of each of the first and second deformable structures, the main piezoelectric elements and the secondary piezoelectric elements being interspersed with one another in said direction of elongation, said secondary piezoelectric elements mounted to the first deformable structure configured to be controlled so as to vary a first resonance frequency of the mobile structure about the first axis;

wherein the reflecting element is greater than each of the plurality of main piezoelectric elements and each of the plurality of secondary piezoelectric elements in length and width.

12. The MEMS device of claim 11, said secondary piezoelectric elements mounted to the second deformable structure configured to be controlled so as to vary a second resonance frequency of the mobile structure about the second axis.

13. The MEMS device of claim 11, wherein the secondary piezoelectric elements each have an elongated shape extending in a direction transverse to the direction of elongation of said main body.

14. The MEMS device of claim 11, wherein each of the first and second deformable structures includes a connection portion extending from the main body and coupled to the mobile structure.

15. The MEMS device of claim 14, wherein the connection portion extends perpendicular to the respective direction of elongation of the main body.