Acoustically decoupled MEMS devices

Patent metadata

Field	Value
Publication number	US-12407322-B2
Application number	US-202318451675-A
Country	US
Kind code	B2
Filing date	Aug 17, 2023
Priority date	Mar 5, 2018
Publication date	Sep 2, 2025
Grant date	Sep 2, 2025

Abstract

A resonator element of the monocrystalline 4H or 6H polytype of silicon carbide. A MEMS device including the resonator element and a substrate, wherein the resonator element and the substrate are not coplanar, and acoustic decoupling of the resonator element and the substrate is at least partially dependent upon a degree to which the resonator element and the substrate are not coplanar. A MEMS gyroscope including the resonator element, a substrate, one or more electrodes disposed proximate the resonator element, and a capacitive gap disposed between each electrode and the resonator element. A MEMS device including the resonator element having has a Q greater than 1,000,000, a phononic crystal substrate, and a gap disposed between a perimeter edge of the resonator element and the phononic crystal substrate, wherein acoustic decoupling of the resonator element and the phononic crystal substrate is at least partially dependent upon a size of the gap.

First claim

What is claimed is:

1. A MEMS device comprising:
a resonator element having a frequency and comprising a transversely isotropic monocrystalline material; and
a quarter-wavelength matched phononic crystal substrate;
wherein:
the resonator element is anchored to the quarter-wavelength matched phononic crystal substrate;
the resonator element and the quarter-wavelength matched phononic crystal substrate are not coplanar;
the resonator element and the quarter-wavelength matched phononic crystal substrate are configured to preserve resonant mode symmetry to minimize frequency split between resonant modes; and
acoustic decoupling of the resonator element and the quarter-wavelength matched phononic crystal substrate is at least partially dependent upon the frequency of the resonator element.

2. The MEMS device of claim 1 , wherein the resonator element has a quality factor (Q) greater than 5,000,000.

3. The MEMS device of claim 1 , wherein the resonator element comprises the monocrystalline 4H or 6H polytype of silicon carbide (SIC).

4. The MEMS device of claim 1 , wherein the resonator element is fabricated using lithography-based batch fabrication processing at wafer level.

5. The MEMS device of claim 1 , wherein the resonator element is a bulk acoustic wave (BAW) resonator element.

6. The MEMS device of claim 1 further comprising:
a pedestal having an aspect-ratio and being disposed between the resonator element and the quarter-wavelength matched phononic crystal substrate;
wherein:
the MEMS device is gyroscope;
the acoustic decoupling is further at least partially dependent by the aspect-ratio of the pedestal; and
the resonator element operates in gyroscopic modes with frequency above 1 MHz.

7. The MEMS device of claim 6 , wherein the resonator element is a BAW resonator element having gyroscopic modes.

8. The MEMS device of claim 7 further comprising:
transducers disposed proximate the BAW resonator element;
wherein the BAW resonator element and transducers are integrated with the quarter-wavelength matched phononic crystal substrate.

9. The MEMS device of claim 8 , wherein each of the transducers is selected from the group consisting of a drive transducer, a sense transducer, and a control transducer.

10. The MEMS device of claim 9 , wherein each of the transducers have the same size.

11. The MEMS device of claim 1 further comprising:
one or more electrodes disposed proximate a surface of the resonator element; and
a capacitive gap disposed between each electrode and the surface of the resonator element.

12. The MEMS device of claim 11 further comprising:
an Si wafer;
wherein:
the resonator element comprises a 4H-SiC wafer having a Si-face on one side and a C-face on the other side; and
the Si wafer is fusion bonded on the C-face of the 4H-SiC wafer.

13. The MEMS device of claim 11 , wherein:
each electrode is disposed proximate a perimeter edge of the resonator element;
each capacitive gap is disposed between the electrode and the perimeter edge of the resonator element; and
each electrode is selected from the group consisting of a capacitively-coupled drive electrode, a sense electrode, and a control electrode.

14. The MEMS device of claim 13 , wherein the resonator element has a quality factor (Q) greater than 5,000,000.

15. The MEMS device of claim 13 , wherein the resonator element has gyroscopic modes.

16. The MEMS device of claim 13 , wherein the resonator element is fabricated using lithography-based batch fabrication processing at wafer level.

17. The MEMS device of claim 13 , wherein the resonator element is a bulk acoustic wave (BAW) resonator element.

18. The MEMS device of claim 13 comprising two or more electrodes;
wherein each of the electrodes share at least one common characteristic.

19. The MEMS device of claim 18 , wherein one common characteristic is selected from the group consisting of a size and a shape.

20. A MEMS device comprising:
a resonator element having a frequency and comprising a transversely isotropic monocrystalline material with a perimeter edge and having has a quality factor (Q) greater than 5,000,000;
a quarter wavelength-matched phononic crystal substrate; and
a gap disposed between the perimeter edge of the resonator element and the quarter wavelength-matched phononic crystal substrate;
wherein:
a native frequency split and a quality factor mismatch are minimized by preserving resonant mode symmetry; and
acoustic decoupling of the resonator element and the quarter-wavelength matched phononic crystal substrate is at least partially dependent upon;
a size of the gap; and
the frequency of the resonator element.

21. The MEMS device of claim 20 further comprising:
a pedestal having an aspect-ratio and being disposed between the resonator element and the quarter-wavelength matched phononic crystal substrate;
wherein acoustic decoupling of the resonator element and the quarter-wavelength matched phononic crystal substrate is further at least partially dependent by the aspect-ratio of the pedestal.

Assignees

• Georgia Tech Res Inst

Inventors

• Ayazi Farrokh
• Hamelin Benoit
• Yang Jeremy

Classifications

• H03H2009/0244

  Anchor loss · CPC title

• H03H9/2436 Primary

  Disk resonators · CPC title

• H03H9/02338

  Suspension means · CPC title

• G01C19/5698

  using acoustic waves, e.g. surface acoustic wave gyros · CPC title

• G01C19/5769

  Manufacturing; Mounting; Housings · CPC title