MEMS vibrating structure using a single-crystal piezoelectric thin-film layer having domain inversions

• US 8,035,280 B2
• Filed: 03/01/2011
• Issued: 10/11/2011
• Est. Priority Date: 11/01/2007
• Status: Active Grant

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: RF Micro Devices Incorporated (Qorvo, Inc.)
• Inventors: Lee, Seungbae, Li, Sheng-Shian, Bhattacharjee, Kushal
• Primary Examiner(s): SAN MARTIN, JAYDI A
• Application Number:
  US13/037,584
• Publication Number:
  US 20110148252A1
• Time in Patent Office: 224 Days
• Field of Search: 310/328, 310/351, 257/414
• US Class Current: 310/351
• CPC Class Codes: H03H 2009/241 Bulk-mode MEMS resonators
• CPC Class Codes: H03H 9/02228 Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer
• CPC Class Codes: H03H 9/02275 Comb electrodes
• CPC Class Codes: H03H 9/2405 of microelectro-mechanical resonators

Abstract

The present invention relates to a micro-electro-mechanical systems (MEMS) vibrating structure supported by a MEMS anchor system, and includes a single-crystal piezoelectric thin-film layer having domain inversions, which determine certain vibrational characteristics of the MEMS vibrating structure. The MEMS vibrating structure may have dominant lateral vibrations or dominant thickness vibrations. The single-crystal piezoelectric thin-film layer may include Lithium Tantalate or Lithium Niobate, and may provide MEMS vibrating structures with precise sizes and shapes, which may provide high accuracy and enable fabrication of multiple resonators having different resonant frequencies on a single substrate.

Claims

1. A vibrating micro-electro-mechanical circuit comprising:

a substrate having a substrate surface;

at least one anchor on the substrate surface; and

a micro-electro-mechanical systems (MEMS) vibrating structure comprising;

a body suspended from the at least one anchor and comprising a single-crystal piezoelectric thin-film having a plurality of domains comprising a nominal domain adjacent to an inverted domain, such that the nominal domain has a first plurality of dipoles substantially oriented in a nominal orientation and the inverted domain has a second plurality of dipoles substantially oriented in an inverted orientation, wherein the inverted orientation is translated about 180 degrees from the nominal orientation;

a first conducting section residing on a first surface of the body that is about parallel to the substrate surface and comprising a first plurality of conducting fingers extending at least partially across an outer width of the MEMS vibrating structure; and

a second conducting section residing on the first surface of the body, comprising at least one conducting finger each extending both at least partially across the outer width of the MEMS vibrating structure and generally between two of the first plurality of conducting fingers;

such that the MEMS vibrating structure has dominant vibrations when a first electrical signal is applied to the first conducting section and a second electrical signal is applied to the second conducting section.

2. The vibrating micro-electro-mechanical circuit of claim 1 wherein the MEMS vibrating structure further comprises a conducting layer in contact with a second surface of the body that is about parallel to the substrate surface.

3. The vibrating micro-electro-mechanical circuit of claim 2 wherein the first electrical signal is applied to the first conducting section and the conducting layer and the second electrical signal is applied to the second conducting section and the conducting layer.

4. The vibrating micro-electro-mechanical circuit of claim 3 wherein both of the first electrical signal and the second electrical signal are AC signals.

5. The vibrating micro-electro-mechanical circuit of claim 4 wherein the first electrical signal is phase shifted approximately 180 degrees from the second electrical signal.

6. The vibrating micro-electro-mechanical circuit of claim 1 wherein the dominant vibrations are dominant lateral vibrations that are about parallel to the substrate surface.

7. The vibrating micro-electro-mechanical circuit of claim 1 wherein the single-crystal piezoelectric thin-film provides the dominant vibrations.

8. The vibrating micro-electro-mechanical circuit of claim 6 wherein the dominant vibrations are based on a direction of a cut of growth of the single-crystal piezoelectric thin-film.

9. The vibrating micro-electro-mechanical circuit of claim 1 wherein the plurality of domains comprises nominal domains that alternate with inverted domains along a plane that is about parallel to the substrate surface.

10. The vibrating micro-electro-mechanical circuit of claim 9 wherein the nominal domains alternate with the inverted domains in only one direction.

11. The vibrating micro-electro-mechanical circuit of claim 9 wherein each of the nominal domains is associated with a single one of the first plurality of conducting fingers and the at least one conducting finger.

12. The vibrating micro-electro-mechanical circuit of claim 11 wherein each of the associated one of the first plurality of conducting fingers and the at least one conducting finger extends down a center of one of the plurality of domains.

13. The vibrating micro-electro-mechanical circuit of claim 9 wherein the nominal domains and the inverted domains are formed by poling.

14. The vibrating micro-electro-mechanical circuit of claim 13 wherein the poling uses an electric field.

15. The vibrating micro-electro-mechanical circuit of claim 14 wherein the electric field has a nominal poling orientation when poling the nominal domains and an inverted poling orientation when poling the inverted domains, wherein the inverted poling orientation is translated about 180 degrees from the nominal poling orientation.

16. The vibrating micro-electro-mechanical circuit of claim 15 wherein the nominal orientation is not parallel to the nominal poling orientation and the inverted orientation is not parallel to the inverted poling orientation.

17. The vibrating micro-electro-mechanical circuit of claim 9 wherein the nominal domains and the inverted domains are periodically-poled.

18. The vibrating micro-electro-mechanical circuit of claim 9 wherein the nominal domains and the inverted domains are non-periodically-poled.

19. The vibrating micro-electro-mechanical circuit of claim 9 wherein each of the nominal domains has a nominal domain length and a nominal domain width that is constant along the nominal domain length, and each of the inverted domains have an inverted domain length and an inverted domain width that is constant along the inverted domain length.

20. The vibrating micro-electro-mechanical circuit of claim 1 further comprising:

a first mechanical support member between one of the at least one anchor and the MEMS vibrating structure; and

a second mechanical support member between another of the at least one anchor and the MEMS vibrating structure.

21. The vibrating micro-electro-mechanical circuit of claim 1 wherein the single-crystal piezoelectric thin-film comprises Lithium Tantalate.

22. The vibrating micro-electro-mechanical circuit of claim 1 wherein the single-crystal piezoelectric thin-film comprises Lithium Niobate.

23. A method comprising:

providing a vibrating micro-electro-mechanical circuit comprising;

a substrate having a substrate surface;

at least one anchor on the substrate surface; and

a micro-electro-mechanical systems (MEMS) vibrating structure comprising;

a body suspended from the at least one anchor and comprising a single-crystal piezoelectric thin-film having a plurality of domains comprising a nominal domain adjacent to an inverted domain, such that the nominal domain has a first plurality of dipoles substantially oriented in a nominal orientation and the inverted domain has a second plurality of dipoles substantially oriented in an inverted orientation, wherein the inverted orientation is translated about 180 degrees from the nominal orientation;

a first conducting section residing on a first surface of the body that is about parallel to the substrate surface and comprising a first plurality of conducting fingers extending at least partially across an outer width of the MEMS vibrating structure; and

a second conducting section residing on the first surface of the body, comprising at least one conducting finger extending both at least partially across the outer width of the MEMS vibrating structure and generally between two of the first plurality of conducting fingers; and

applying a first electrical signal to the first conducting section and applying a second electrical signal to the second conducting section to produce dominant vibrations the MEMS vibrating structure.

24. The method of claim 23 wherein the MEMS vibrating structure further comprises a conducting layer in contact with a second surface of the body that is about parallel to the substrate surface.

25. The method of claim 24 wherein the first electrical signal is applied to the first conducting section and the conducting layer and the second electrical signal is applied to the second conducting section and the conducting layer.