Thin-film bulk acoustic resonators having perforated bodies that provide reduced susceptibility to process-induced lateral dimension variations

• US 7,939,990 B2
• Filed: 02/26/2009
• Issued: 05/10/2011
• Est. Priority Date: 01/30/2009
• Status: Active Grant

• Current Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Original Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Inventors: Wang, Ye, Bhugra, Harmeet
• Primary Examiner(s): Dougherty, Thomas M
• Application Number:
  US12/393,566
• Publication Number:
  US 20100194241A1
• Time in Patent Office: 803 Days
• Field of Search: 310/320, 310/324, 310/328, 310/367, 310/368
• US Class Current: 310/320
• CPC Class Codes: H03H 2009/0233 comprising perforations
• CPC Class Codes: H03H 2009/241 Bulk-mode MEMS resonators
• CPC Class Codes: H03H 9/172 Means for mounting on a substrate, i.e. means constituting the material interface confining the waves to a volume
• CPC Class Codes: H03H 9/2452 Free-free beam resonators

Abstract

Micro-electromechanical acoustic resonators include a resonator body suspended over a substrate. The resonator body may have a single perforation therein, which may extend substantially or completely therethrough. The resonator body may also be configured to have a center-of-mass within an interior of the perforation and/or a nodal line that overlaps the perforation. A perimeter and depth of the single perforation can be configured to reduce a susceptibility of the acoustic resonator to process-induced variations in resonant frequency relative to an otherwise equivalent resonator that omits the single perforation. In other embodiments, the resonator body may have multiple perforations therein that extend along a nodal line of the resonator.

Claims

1. A micro-electromechanical acoustic resonator, comprising:

a resonator body suspended over a substrate, said resonator body having a single perforation therein extending at least substantially therethrough at a location that overlaps with a nodal line of said resonator body when said resonator body is operating at resonant frequency, said resonator body having a sidewall that is separated from an opposing sidewall of the substrate by a distance equivalent to a width of the single perforation.

2. The resonator of claim 1, wherein a perimeter and depth of the single perforation is configured to reduce a susceptibility of the resonator to process-induced variations in resonant frequency relative to an otherwise equivalent resonator that omits the single perforation.

3. The resonator of claim 1, wherein said resonator body is anchored on opposite sides to the substrate.

4. The resonator of claim 3, wherein said resonator body is suspended opposite a recess in the substrate.

5. The resonator of claim 1, wherein a length (L_s) and the width (W_s) of the single perforation is related to a length (L_rb) and a width (W_rb) of said resonator body by the following relationship:

(0.4)L_rb(W_s/2(L_rb−

W_rb+W_s))^1/2≦

L_s≦

(0.6)L_rb(W_s/2(L_rb−

W_rb+W_s))^1/2,

where the length (L_rb) is greater than the width (W_rb), and the length (L_s) is greater than the width (W_s).

6. The resonator of claim 5, wherein said resonator body and the single perforation are rectangular shaped.

7. The resonator of claim 1, wherein said resonator body and the single perforation are rectangular shaped.

8. A micro-electromechanical acoustic resonator, comprising:

a resonator body suspended over a substrate, said resonator body having a single perforation therein extending at least substantially therethrough at a location that overlaps with a nodal line of said resonator body when said resonator body is operating at resonant frequency, said single perforation having a length (L_s) and a width (W_s) that is related to a length (L_rb) and a width (W_rb) of said resonator body by the following relationship;

(0.4)L_rb(W_s/2(L_rb−

W_rb+W_s))^1/2≦

L_s≦

(0.6)L_rb(W_s/2(L_rb−

W_rb+W_s))^1/2,

where the length (L_rb) is greater than the width (W_rb), and the length (L_s) is greater than the width (W_s).

9. The resonator of claim 8, wherein said resonator body and the single perforation are rectangular shaped.

10. A micro-electromechanical acoustic resonator, comprising:

a resonator body anchored on opposite sides to a substrate having a recess therein extending underneath said resonator body, said resonator body having at least one perforation therein extending at least substantially therethrough, said at least one perforation having a length (L_s) and a width (W_s) that are related to a length (L_rb) and a width (W_rb) of said resonator body by the following relationship;

(0.4)L_rb(W_s/2(L_rb−

W_rb+W_s))^1/2≦

L_s≦

(0.6)L_rb(W_s/2(L_rb−

W_rb+W_s))^1/2,

where the length (L_rb) is greater than the width (W_rb), and the length (L_s) is greater than the width (W_s).

11. The resonator of claim 10, wherein the at least one perforation is aligned with a nodal line of said resonator body.

12. The resonator of claim 10, wherein the at least one perforation extends entirely through said resonator body.

13. The resonator of claim 10, wherein said resonator body and the at least one perforation are rectangular shaped.

14. A micro-electromechanical acoustic resonator, comprising:

a resonator body anchored on opposite sides to a substrate having a recess therein extending underneath said resonator body, said resonator body having N perforations therein extending at least substantially therethrough, with at least one of the N perforations having a length (L_s) and width (W_s) that are related to a length (L_rb) and a width (W_rb) of said resonator body by the following relationship;

(0.4)L_rb(W_s/2(L_rb−

(W_rb/N)+W_s))^1/2≦

L_s≦

(0.6)L_rb(W_s/2(L_rb−

(W_rb/N)+W_s))^1/2,

where the length (L_rb) is less than the width (W_rb) and “

N”

is an integer greater than one.

15. The resonator of claim 14, wherein the N perforations are arranged along a nodal line of said resonator body.

16. The resonator of claim 15, wherein a center-to-center pitch between the N perforations is equivalent to λ

/4, where λ

is a wavelength associated with a resonant frequency of the resonator.

17. The resonator of claim 14, wherein said resonator body is configured to have a center-of-mass within an interior of one of the N perforations.

18. The resonator of claim 17, wherein the N perforations are arranged along a nodal line of said resonator body.

19. The resonator of claim 14, wherein said resonator body is configured to have a projected point of maximum stress within an interior of one of the N perforations when said resonator body is operating at a resonant frequency.

20. The resonator of claim 14, wherein said resonator body and the N perforations are rectangular shaped.