MEMS resonator including main and sub movable beams, and exciting electrodes excited by alternating-current signal

• US 7,990,233 B2
• Filed: 11/05/2008
• Issued: 08/02/2011
• Est. Priority Date: 05/01/2008
• Status: Expired due to Fees

• Current Assignee: The Ritsumeikan Trust (Ritsumei-Kan University Educational Association)
• Original Assignee: Semiconductor Technology Academic Research Center
• Inventors: Suzuki, Kenichiro
• Primary Examiner(s): Summons; Barbara
• Application Number:
  US12/265,141
• Publication Number:
  US 20100327992A1
• Time in Patent Office: 1,000 Days
• Field of Search: 333/186, 333/188, 310/309, 331/154, 331/156, 331/177.R
• US Class Current: 333/186
• CPC Class Codes: H03H 2009/02299 Comb-like, i.e. the beam comprising a plurality of fingers or protrusions along its length
• CPC Class Codes: H03H 2009/02496 Horizontal, i.e. parallel to the substrate plane
• CPC Class Codes: H03H 3/0072 of microelectro-mechanical resonators or networks micromembranes or microbeams B81B2203/01; manufacture of microstructural devices in general B81C
• CPC Class Codes: H03H 9/02259 Driving or detection means
• CPC Class Codes: H03H 9/2463 Clamped-clamped beam resonators

Abstract

A MEMS resonator includes a main movable beam, at least one sub movable beam, and at least one exciting electrode. The main movable beam is electrically insulated from a substrate and fixed to at least one fixed end, the sub movable beam is formed to extend from the main movable beam, and the exciting electrode is provided to be close to the sub movable beam. The sub movable beam is excited by an electrostatic force to oscillate by exciting the exciting electrode using an alternating-current signal, such that the MEMS resonator resonates with at least one of a fundamental resonant frequency and harmonic frequencies thereof. The resonant frequency is changed by changing at least one of number of the at least one exciting electrode and a position of the exciting electrode relative to the sub movable beam.

Claims

1. A Micro-Electro-Mechanical System (MEMS) resonator, comprising:

a main movable beam having first and second ends, the main movable beam being electrically insulated from a substrate and fixed to at least one end of the first and second ends;

a plurality of sub movable beams including first, second, third and fourth sub movable beams, the sub movable beams being formed at respective predetermined intervals in a direction substantially perpendicular to a longitudinal direction of the main movable beam, to extend from the main movable beam and to project from both of first and second side surfaces of the main movable beam;

a first exciting electrode provided at a position of the first side surface of the main movable beam to be close to the first and second sub movable beams which are located at a center of the longitudinal direction of the main movable beam;

a second exciting electrode provided at a position of the first side surface of the main movable beam to be close to the second sub movable beam and the third sub movable beam which is located to be adjacent at a side of the first end to the second sub movable beam; and

a third exciting electrode provided at a position of the second side surface of the main movable beam to be close to the first sub movable beam and the fourth sub movable beam which is located to be adjacent at a side of the second end to the first sub moveable beam,

wherein the first and second sub movable beams are excited by an electrostatic force to oscillate in an oscillation direction substantially perpendicular to the longitudinal direction of the main movable beam and parallel to a surface of the substrate by exciting the first exciting electrode using an alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a first-order mode thereof, and

the first to fourth sub movable beams are excited by an electrostatic force to oscillate in the oscillation direction by exciting the second and third exciting electrodes using the alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a second-order mode thereof.

2. The MEMS resonator of claim 1, wherein the first exciting electrode is connected via a first switch with an exciting signal generator for generating the alternating current signal,

the second and third exciting electrodes are connected via a second switch with the exciting signal generator, and

the MEMS resonator resonates with one of the resonant frequency of the first-order mode and the resonant frequency of the second-order mode by turning on one of the first and second switches, respectively.

3. The MEMS resonator of claim 2, wherein the plurality of sub movable beams further includes fifth and sixth sub movable beams, and

the MEMS resonator further comprises:

a fourth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the third sub movable beam and the fifth sub movable beam which is located to be adjacent at the side of the first end to the third sub movable beam; and

a fifth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the fourth sub movable beam and the six sub movable beam which is located to be adjacent at the side of the second end to the fourth sub movable beam, and

wherein the third to sixth sub movable beams are excited by an electrostatic force to oscillate in the oscillation direction by exciting the fourth and fifth exciting electrodes using the alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a third-order mode thereof.

4. The MEMS resonator of claim 3, wherein the fourth and fifth exciting electrodes are connected via a third switch with the exciting signal generator, and the MEMS resonator resonates with one of the resonant frequency of the third-order mode by turning on the third switch.

5. The MEMs resonator of claim 1, wherein the plurality of sub movable beams further includes fifth and sixth sub movable beams, and

the MEMS resonator further comprises:

a fourth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the third sub movable beam and the fifth sub movable beam which is located to be adjacent at the side of the first end to the third sub movable beam; and

a fifth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the fourth sub movable beam and the sixth sub movable beam which is located to be adjacent at the side of the second end to the fourth sub movable beam, and

wherein the third to sixth sub movable beams are excited by an electrostatic force to oscillate in the oscillation direction by exciting the fourth and fifth exciting electrodes using the alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a third-order mode thereof.

6. The MEMS resonator of claim 5, wherein the fourth and fifth exciting electrodes are connected via a third switch with the exciting signal generator, and the MEMS resonator resonates with the resonate frequency of a third-order mode by turning on the third switch.

7. The MEMS resonator of claim 5, wherein the main movable beam is fixed at the first and second ends thereof.

8. The MEMS resonator of claim 5, wherein the substrate is one of a dielectric substrate and a semiconductor substrate, and each of the main movable beam and the sub movable beams is made of one of an electric conductive material and a semiconductor material.

9. The MEMS resonator of claim 1, wherein the main movable beam is fixed at the first and second ends thereof.

10. The MEMS resonator of claim 1, wherein the substrate is one of a dielectric substrate and a semiconductor substrate, and each of the main movable beam and the sub movable beams is made of one of an electric conductive material and a semiconductor material.

11. A Micro-Electro-Mechanical System (MEMS) resonator, comprising:

a main movable beam having first and second ends, the main movable beam being electrically insulated from a substrate and fixed to at least one end of the first and second ends;

a plurality of sub movable beams including first, second, third, fourth, fifth and sixth sub movable beams, the sub movable beams being formed at respective predetermined intervals in a direction substantially perpendicular to a longitudinal direction of the main movable beam, to extend from the main movable beam and to project from both of first and second side surfaces of the main movable beam;

a first exciting electrode provided at a position of the first side surface of the main movable beam to be close to the first and second sub movable beams which are located at a center of the longitudinal direction of the main movable beam;

a fourth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the third sub movable beam which is located to be adjacent at a side of the first end to the second sub movable beam, and to be close to the fifth sub movable beam which is located to be adjacent at the side of the first end to the third sub movable beam; and

a fifth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the fourth sub movable mean which is located to be adjacent at a side of the second end to the first sub movable beam, and to be close to the sixth sub movable beam which is located to be adjacent at the side of the second end to the fourth sub movable beam,

wherein the first and second sub movable beams are excited by an electrostatic force to oscillate in an oscillation direction substantially perpendicular to the longitudinal direction of the main movable beam and parallel to a surface of the substrate by exciting the first exciting electrode using an alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a first-order mode thereof, and

the third to sixth sub movable beams are excited by an electrostatic force to oscillate in the oscillation direction by exciting the fourth and fifth exciting electrodes using the alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a third-order mode thereof.

13. The MEMS resonator of claim 11, wherein the main movable beam is fixed at the first and second ends thereof.

14. The MEMS resonator of claim 11, wherein the substrate is one of a dielectric substrate and a semiconductor substrate, and each of the main movable beam and the sub movable beams is made of one of an electric conductive material and a semiconductor material.

12. The MEMS resonator of claimed 11, wherein the first exciting electrode is connected via a first switch with an exciting signal generator for generating the alternating-current signal,

the fourth and fifth exciting electrodes are connected via a third switch with the exciting signal generator, and

the MEMS resonator resonates with one of the resonant frequency of the first-order mode and the resonant frequency of the third-order mode by turning on one of the first and third switches, respectively.

15. A Micro-Electro-Mechanical System (MEMS) oscillation circuit including a MEMS resonator,

wherein the MEMS resonator comprises:

a main movable beam having first and second ends, the main movable beam electrically insulated from a substrate and fixed to at least one end of the first and second ends;

a plurality of sub movable beams including first, second, third and fourth sub movable beams, the sub movable beams formed at respective predetermined intervals in a direction substantially perpendicular to a longitudinal direction of the main movable beam, to extend from the main movable beam and to project from both of first and second side surfaces of the main movable beam;

a first exciting electrode provided at a position of the first side surface of the main movable beam to be close to the first and second sub movable beams which are located at a center of the longitudinal direction of the main movable beam;

a second exciting electrode provided at a position of the first side surface of the main movable beam to be close to the second sub movable beam and the third sub movable beam which is located to be adjacent at a side of the first end to the second sub movable beam; and

a third exciting electrode provided at a position of the second side surface of the main movable beam to be close to the first sub movable beam and the fourth sub movable beam which is located to be adjacent at a side of the second end to the first sub movable beam,

wherein the first and second sub movable beams are excited by an electrostatic force to oscillate in an oscillation direction substantially perpendicular to the longitudinal direction of the main movable beam and parallel to a surface of the substrate by exciting the first exciting electrode using an alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a second-order mode thereof,

the first to fourth sub movable beams are excited by an electrostatic force to oscillate in the oscillation direction by exciting the second and third exciting electrodes using the alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a second-order mode thereof, and

the MEMS oscillation circuit oscillates with an identical frequency to the resonant frequency of the MEMS resonator.

16. The MEMS oscillation circuit of claim 15,

wherein the plurality of sub movable beams further includes fifth and sixth sub movable beams, and

the MEMS resonator further comprises:

a fourth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the third sub movable beam and the fifth sub movable beam which is located to be adjacent at the side of the first end to the third sub movable beam; and

a fifth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the fourth sub movable beam and the sixth sub movable beam which is located to be adjacent at the side of the second end to the fourth sub movable beam, and

wherein the third to sixth sub movable beams are excited by an electrostatic force to oscillate in the oscillation direction by exciting the fourth and fifth exciting electrodes using the alternating current signal, such that the MEMS resonator resonates with a resonant frequency of a third-order mode thereof.

17. A Micro-Electro-Mechanical System (MEMS) oscillation circuit including a MEMS resonator,

wherein the MEMS resonator comprises:

a main movable beam having first and second ends, the main movable beam being electrically insulated from a substrate and fixed to at least one end of the first and second ends;

a plurality of sub movable beams including first, second, third, fourth, fifth and sixth sub movable beams, the sub movable beams being formed at respective predetermined intervals in a direction substantially perpendicular to a longitudinal direction of the main movable beam, to extend from the main movable beam and to project from both first and second side surfaces of the main movable beam;

a first exciting electrode provided at a position of the first side surface of the main movable beam to be close to the first and second sub movable beams which are located at a center of the longitudinal direction of the main movable beams;

a fourth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the third sub movable beam which is located to be adjacent at a side of the first end to the second sub movable beam, and to be close to the fifth sub movable beam which is located to be adjacent at the side of the first end to the third sub movable beam; and

a fifth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the fourth sub movable beam which is located to be adjacent at a side of the second end to the first sub movable beam, and to be close to the sixth sub movable beam which is located to be adjacent at the side of the second end to the fourth sub movable beam,

wherein the first and second sub movable beams are excited by an electrostatic force to oscillate in an oscillation direction substantially perpendicular to the longitudinal direction of the main movable beam and parallel to a surface of the substrate by exciting the first exciting electrode using an alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a first-order mode thereof,

the third to sixth sub movable beams are excited by an electrostatic force to oscillate in the oscillation direction by exciting the fourth and fifth exciting electrodes using the alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a third-order mode thereof, and

the MEMS oscillation circuit oscillates with an identical frequency to the resonant frequency of the MEMS resonator.

18. A Micro-Electro-Mechanical System (MEMS) device including a MEMS resonator,

wherein the MEMS resonator comprises:

a main movable beam having first and second ends, the main movable being beam electrically insulated from a substrate and fixed to at least one end of the first and second ends;

a plurality of sub movable beams including first, second, third and fourth sub movable beams, the sub movable beams being formed at respective predetermined intervals in a direction substantially perpendicular to a longitudinal direction of the main movable beam, to extend from the main movable beam and to project from both first and second side surfaces of the main movable beam;

a first exciting electrode provided at a position of the first side surface of the main movable beam to be close to the first and second sub movable beams which are located at a center of the longitudinal direction of the main movable beams;

a second exciting electrode provided at a position of the first side surface of the main movable beam to be close to the second sub movable beam and the third sub movable beam which is located to be adjacent at a side of the first end to the second sub movable beam; and

a third exciting electrode provided at a position of the second side surface of the main movable beam to be close to the first sub movable beam and the fourth sub movable beam which is located to be adjacent at a side of the second end to the first sub movable beam,

wherein the first and second sub movable beams are excited by an electrostatic force to oscillate in an oscillation direction substantially perpendicular to the longitudinal direction of the main movable beam and parallel to the surface of the substrate by exciting the first exciting electrode using an alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a first-order mode thereof,

the first to fourth sub movable beams are excited by an electrostatic force to oscillate in the oscillation direction by exciting the second and third exciting electrodes using the alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a second-order mode thereof, and

the MEMS oscillation circuit oscillates with an identical frequency to the resonant frequency of the MEMS resonator.

19. The MEMS device of claim 18,

wherein the plurality of sub movable beams further includes fifth and sixth sub movable beams, and

the MEMS resonate further comprises:

a fourth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the third sub movable beam and the fifth sub movable beam which is located to be adjacent at the side of the first end to the third sub movable beam; and

a fifth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the fourth sub movable beam and the sixth sub movable beam which is located to adjacent at the side of the second end to the fourth sub movable beam, and

wherein the third to sixth sub movable beams are excited by an electrostatic force to oscillate in the oscillation direction by exciting the fourth and fifth exiting electrodes using the alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a third-order mode thereof.

20. A Micro-Electro-Mechanical System (MEMS) device including a MEMS resonator,

wherein the MEMS resonator comprises:

a main movable beam having first and second ends, the main movable beam being electrically insulated from a substrate and fixed to at least one end of the first and second ends;

a plurality of sub movable beams including first, second, third, fourth, fifth and sixth sub movable beams, the sub movable beams being formed at respective predetermined intervals in a direction substantially perpendicular to a longitudinal direction of the main movable beam, to extend from the main movable beam and to project from both first and second side surfaces of the main movable beam;

a first exciting electrode provided at a position of the first side surface of the main movable beam to be close to the first and second sub movable beams which are located at a center of the longitudinal direction of the main movable beams;

a fourth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the third sub movable beam which is located to be adjacent at a side of the first end to the second sub movable beam, and to be close to the fifth sub movable beam which is located to be adjacent at the side of the first end to the third sub movable beam; and

a fifth exciting electrode provided at a position of the second side surface of the main movable beam to be close to the fourth sub movable beam which is located to be adjacent at a side of the second end to the first sub movable beam, and to be close to the sixth sub movable beam which is located to be adjacent at the side of the second end to the fourth sub moveable beam,

wherein the first and second sub movable beams are excited by an electrostatic force to oscillate in an oscillation direction substantially perpendicular to the longitudinal direction of the main movable beam and parallel to the surface of the substrate by exciting the first exciting electrode using an alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a first-order mode thereof,

the third to sixth sub movable beams are excited by an electrostatic force to oscillate in the oscillation direction by exciting the fourth and fifth exiting electrodes using the alternating-current signal, such that the MEMS resonator resonates with a resonant frequency of a third-order mode thereof, and

the MEMS device utilizes a resonant state of the MEMS resonator.