Thin-film micromachine resonator, thin-film micromachine resonator gyroscope, navigation system using the thin-film micromachine resonator gyroscope, and automobile

• US 20040095046A1
• Filed: 12/11/2003
• Published: 05/20/2004
• Est. Priority Date: 11/27/2001
• Status: Active Grant

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Ouchi, Satoshi, Nomura, Koji, Nozoe, Toshiyuki, Tajika, Hirofumi
• Granted Patent: US 7,002,284 B2
• Time in Patent Office: Days
• US Class Current: 310/370
• CPC Class Codes: G01C 19/5607 using vibrating tuning forks double-ended tuning forks using planar vibrating masses suspended at opposite ends G01C19/5719
• CPC Class Codes: H03H 2003/0492 during the manufacture of a tuning-fork
• CPC Class Codes: H03H 9/21 Crystal tuning forks
• CPC Class Codes: H03H 9/2484 with two fork tines, e.g. Y-beam cantilever

Abstract

A thin film micromechanical resonator (resonator) having improved drive efficiency, a resonator gyro having improved sensitivity in detecting an angular velocity, and a navigation system and an automobile using the resonator gyro. The resonator includes a tuning fork structure made of a non-piezoelectric material, and a first electrode and a second electrode disposed respectively at the inner side and the outer side of the tuning fork arm. On the first and second electrodes, a first piezo film and a second piezo film are provided respectively, and a third electrode and a fourth are respectively provided electrode thereon. When an alternating voltage is applied to the third and fourth electrodes at the opposite phases each other, the tuning fork resonates in the direction perpendicular to the center line. The resonator gyro detects, at the sensing section which is formed of another electrodes and another piezo film, the Coriolis force generated in proportion to angular velocity given to the resonator.

Claims

1. A thin film micromechanical resonator comprising

(a) a tuning fork having at least two arms and at least one stem connecting said arms, formed of a non-piezoelectric material,

(b) a first electrode provided on at least one main surface of at least one of said arms, in a place inner than a center line of said at least one main surface,

(c) a second electrode provided on said at least one main surface, in a place outer than said center line with a separation from said first electrode,

(d) a first piezoelectric thin film provided on said first electrode,

(e) a second piezoelectric thin film provided on said second electrode,

(f) a third electrode provided on said first piezoelectric thin film, and

(g) a fourth electrode provided on said second piezoelectric thin film;

wherein

said tuning fork resonates in the direction perpendicular to said center line (X direction), when an alternating voltage is applied to said third and fourth electrodes at opposite phases each other.

2. The thin film micromechanical resonator of claim 1, wherein

said first electrode and said second electrode, said third electrode and said fourth electrode, and said first piezoelectric thin film and said second piezoelectric thin film are disposed substantially symmetrical to each other to said center line.

3. The thin film micromechanical resonator of claim 1, wherein

said first, second, third, fourth electrodes and said first and second piezoelectric thin films are disposed on said at least one main surface, in a place from substantially a middle to a vicinity of said stem.

4. The thin film micromechanical resonator of claim 1, wherein

said first and second electrodes and said first and second piezoelectric thin films are provided with an insulating layer covering a circumference portion.

5. The thin film micromechanical resonator of claim 1, wherein

said tuning fork is formed of silicon (Si).

6. The thin film micromechanical resonator of claim 5, wherein

the (1-11) crystal plane or the (−

111) crystal plane of said Si (110) crystal plane wafer is disposed perpendicular to said resonance direction.

7. The thin film micromechanical resonator of claim 5, wherein

the (011) crystal plane or the (001) crystal plane of said Si (100) crystal plane wafer is disposed perpendicular to said resonance direction.

8. The thin film micromechanical resonator of claim 5, wherein

said first and second electrodes provided on said at least one main surface of said tuning fork include a Ti layer disposed beneath each of said first and second electrodes and a Pt—

Ti layer disposed over said each of said first and second electrodes.

9. The thin film micromechanical resonator of claim 8, wherein

a layer of lead titanate added with lanthanum and magnesium (PLMT) is further provided between said Pt—

Ti layer and said piezoelectric thin film.

10. The thin film micromechanical resonator of claim 1, wherein

said piezoelectric thin film is formed of lead zirconate titanate (PZT), or a lead zirconate titanate (PZT) system added with at least one item among a group of Mg, Nb and Mn.

11. The thin film micromechanical resonator of claim 10, wherein

said piezoelectric thin film has a rhombohedral crystalline structure with a (001) crystal plane thereof in parallel with said at least one main surface, or a tetragonal crystalline structure with a (111) crystal plane thereof in parallel with said at least one main surface.

12. The thin film micromechanical resonator of claim 1, wherein

each of said third and fourth electrodes include a Ti layer disposed beneath said each of said third and fourth electrodes and an Au layer disposed over said each of said third and fourth electrodes.

13. The thin film micromechanical resonator of claim 1, wherein

an alternating voltage is applied to said first and fourth electrodes at the same phase, to said second and third electrodes at the same phase, while to said first and second electrodes at the opposite phases each other.

14. A thin film micromechanical resonator gyro comprising

(1) a tuning fork having at least two arms and at least one stem connecting said arms, formed of a non-piezoelectric material;

(2) a drive section including

(a) a first electrode provided on at least one main surface of at least one of said arms in a place inner than a center line of the main surface,

(b) a second electrode provided on said at least one main surface in a place outer than the center line with a separation from said first electrode,

(c) a first piezoelectric thin film provided on said first electrode,

(d) a second piezoelectric thin film provided on said second electrode,

(e) a third electrode provided on said first piezoelectric thin film, and

(f) a fourth electrode provided on said second piezoelectric thin film; and

(3) a sensing section provided on said at least one main surface of said at least one of arms, wherein

said tuning fork resonates in the direction perpendicular to said center line (X direction) when an alternating voltage is applied to said third and fourth electrodes at opposite phases each other, and

said sensing section detects flexion of said arm due to an angular velocity given thereto, caused in the direction perpendicular to said main surface (Z direction) in proportion to the Coriolis force, as an electrical or optical output.

15. The thin film micromechanical resonator gyro of claim 14, wherein

said first electrode and said second electrode, said third electrode and said fourth electrode, and said first piezoelectric thin film and said second piezoelectric thin film are disposed substantially symmetric, respectively, to each other to said center line.

16. The thin film micromechanical resonator gyro of claim 14, wherein

said drive section is disposed on said at least one main surface of said at least one arm, in a place from substantially a middle portion of said at least one main surface to a vicinity of the stem.

17. The thin film micromechanical resonator gyro of claim 14, wherein

said sensing section is disposed on said at least one of main surfaces of said at least one arm, in a place from a substantially middle of said at least one main surface to a vicinity of the stem.

18. The thin film micromechanical resonator gyro of claim 14, wherein

said sensing section includes a fifth electrode disposed on said at least one main surface with a separation from said first and second electrodes, a third piezoelectric thin film provided on said fifth electrode, and a sixth electrode provided on said third piezoelectric thin film.

19. The thin film micromechanical resonator gyro of claim 14, wherein

an insulating layer is formed covering circumference portions of said first and second electrodes and said first and second piezoelectric thin films.

20. The thin film micromechanical resonator gyro of claim 18, wherein

said fifth electrode is disposed in a place further to an end of said arm than said first and second electrodes,

a first lead out electrode is provided between said first and second electrodes with a separation from the electrodes,

said fifth electrode is connected with said first lead out electrode,

at least circumference portions of said first and second electrodes and said first and second piezoelectric thin films, and said first lead out electrode are covered with an insulating layer,

a second lead out electrode is provided between said third and fourth electrodes on said insulating layer with a separation from said third and fourth electrodes,

said sixth electrode is connected with said second lead out electrode, and

said first and second electrodes, said third and fourth electrodes, said fifth and sixth electrodes, said first and second lead out electrodes, said first and second piezoelectric thin films, and said third piezoelectric thin film are disposed substantially symmetric to said center line.

21. The thin film micromechanical resonator gyro of claim 14, wherein

said tuning fork is formed of Si (silicon).

22. The thin film micromechanical resonator gyro of claim 21, wherein

a (1-11) crystal plane or a (−

111) crystal plane of a (110) crystal plane wafer of the Si is disposed perpendicular to said resonance direction (X direction).

23. The thin film micromechanical resonator gyro of claim 21, wherein

a (010) crystal plane, a (011) crystal plane or a (001) crystal plane of a (100) crystal plane wafer of the Si is disposed perpendicular to said resonance direction (X direction).

24. The thin film micromechanical resonator gyro of claim 21, wherein

each of said first, second and fifth electrodes includes a Ti layer disposed at a lower part thereof and a Pt—

Ti layer disposed at an upper part thereof.

25. The thin film micromechanical resonator gyro of claim 24, wherein

a layer of lead titanate added with lanthanum and magnesium (PLMT) is further provided between said Pt—

Ti layer and said piezoelectric thin film.

26. The thin film micromechanical resonator gyro recited in claim 14 or 18, wherein

said first, second and third piezoelectric thin films are formed of lead zirconate titanate (PZT), or a lead zirconate titanate (PZT) system added with at least one item among the group of Mg, Nb and Mn.

27. The thin film micromechanical resonator gyro of claim 26, wherein

said first, second and third piezoelectric thin films have a rhombohedral crystalline structure with a (001) crystal plane thereof in parallel with said at least one main surface, or a tetragonal crystalline structure with a (111) crystal plane thereof in parallel with said at least one main surface.

28. The thin film micromechanical resonator gyro of claim 18, wherein

each of said third, fourth and sixth electrodes includes a Ti layer disposed as the lower part and an Au layer disposed as the upper part.

29. The thin film micromechanical resonator gyro of claim 14, wherein

an alternating voltage is applied to said first and fourth electrodes at the same phase, to said second and third electrodes at the same phase, while to said first and second electrodes at opposite phases o each other.

30. A navigation system using the thin film micromechanical resonator gyro recited in claim 14, 18 or 20.

31. An automobile using the thin film micromechanical resonator gyro recited in claim 14, 18 or 20 as a sensor for detecting one of a yaw rate, a rolling and a pitching.

32. The thin film micromechanical resonator gyro of claim 14, said sensing section including

i) a fifth electrode provided on said at least one main surface in a place further to an end portion of said arm than said first and second electrodes, with a separation from said first and second electrodes,

ii) a third piezoelectric thin film provided on said fifth electrode, and

iii) a sixth electrode provided on said third piezoelectric thin film;

further comprising a lead section which includes

i) a first lead out electrode provided between said first and second electrodes with a separation from the electrodes, the first lead out electrode being connected with said fifth electrode,

ii) a fourth piezoelectric thin film provided on said first lead out electrode, and

iii) a second lead out electrode provided on said fourth piezoelectric thin film and connected with said sixth electrode, wherein

said sixth electrode detects an electric charge caused by vibration due to flexion of said arm.

33. The thin film micromechanical resonator gyro of claim 32, wherein

said tuning fork structure is formed of Si (silicon).

34. The thin film micromechanical resonator gyro of claim 33, wherein

a (1-11) crystal plane or a (−

111) crystal plane of a (110) crystal plane wafer of the Si is disposed perpendicular to said resonance direction (X direction).

35. The thin film micromechanical resonator gyro of claim 33, wherein

a (010) crystal plane, a (011) crystal plane or a (001) crystal plane of a (100) crystal plane wafer of the Si is disposed perpendicular to said resonance direction (X direction).

36. The thin film micromechanical resonator gyro of claim 33, wherein

each of said first, second and fifth electrodes and said first lead out electrode disposed on said at least one main surface includes a Ti layer disposed at a lower part thereof and a Pt—

Ti layer disposed at an upper part thereof.

37. The thin film micromechanical resonator gyro of claim 36, wherein

a layer of lead titanate added with lanthanum and magnesium (PLMT) is further provided between said Pt—

Ti layer and said piezoelectric thin film.

38. The thin film micromechanical resonator gyro of claim 32, wherein

said piezoelectric thin film is formed of lead zirconate titanate (PZT), or a lead zirconate titanate (PZT) system added with at least one item among a group of Mg, Nb and Mn.

39. The thin film micromechanical resonator gyro of claim 38, wherein

said piezoelectric thin film has a rhombohedral crystalline structure wherein the (001) crystal plane is in parallel with said at least one main surface, or a tetragonal crystalline structure wherein the (111) crystal plane is in parallel with said at least one main surface.

40. The thin film micromechanical resonator gyro of claim 32, wherein

said drive section is disposed on said at least one main surface of said at least one of said arms in a place from a substantially middle of said at least one main surface to a vicinity of the stem.

41. The thin film micromechanical resonator gyro of claim 32, wherein

each of said third, fourth and sixth electrodes and said second lead out electrode includes a Ti layer disposed at a lower part thereof and an Au layer disposed at an upper part thereof.

42. The thin film micromechanical resonator gyro of claim 32, wherein

said first, second, third, fourth, fifth and sixth electrodes, said first and second lead out electrodes, and said first, second, third and fourth piezoelectric thin films are disposed substantially symmetric to said center line.

43. The thin film micromechanical resonator gyro of claim 32, wherein

an alternating voltage is applied to said first and fourth electrodes at the same phase, to said second and third electrodes at the same phase, while to said first and second electrodes at opposite phases each other.

44. A navigation system which includes the thin film micromechanical resonator gyro recited in claim 32.

45. An automobile which includes the thin film micromechanical resonator gyro recited in claim 32, used as a sensor for detecting one of a yaw rate, a rolling and a pitching.