Method of manufacturing a mechanical resonating structure

• US 9,762,202 B2
• Filed: 02/11/2014
• Issued: 09/12/2017
• Est. Priority Date: 12/17/2008
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Thalmayr, Florian, Kuypers, Jan H., Schoepf, Klaus Juergen
• Primary Examiner(s): Kim, Paul D
• Application Number:
  US14/177,571
• Publication Number:
  US 20140306580A1
• Time in Patent Office: 1,309 Days
• Field of Search: 29 2535, 295921, 29594, 296091, 310313 A, 310313 B, 310313 C, 310313 D, 310340, 310344, 310345
• CPC Class Codes: G01P 15/0922 of the bending or flexing mode type
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: H01F 3/04 made from strips or ribbons
• CPC Class Codes: H03H 2009/241 Bulk-mode MEMS resonators
• CPC Class Codes: H03H 9/02102 of temperature influence cutting angles H03H9/02015
• 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 9/02244 of microelectro-mechanical resonators
• CPC Class Codes: H03H 9/02275 Comb electrodes
• CPC Class Codes: H03H 9/02448 of temperature influence
• CPC Class Codes: H03H 9/02535 of surface acoustic wave devices
• CPC Class Codes: H03H 9/02574 of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate
• CPC Class Codes: H03H 9/02834 of temperature influence cut angles H03H9/02543
• CPC Class Codes: H03H 9/02984 Protection measures against damaging
• CPC Class Codes: H03H 9/02992 Details of bus bars, contact pads or other electrical connections for finger electrodes
• CPC Class Codes: H03H 9/2405 of microelectro-mechanical resonators
• CPC Class Codes: H04R 2201/003 Mems transducers or their use of the electrostatic type H04R19/005
• CPC Class Codes: H04R 2217/00 Details of magnetostrictive, piezoelectric, or electrostrictive transducers covered by H04R15/00 or H04R17/00 but not provided for in any of their subgroups
• CPC Class Codes: H04R 31/00 Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor manufacture of microstructural arrangements of deformable or non-deformable structures in general B81C1/00182
• CPC Class Codes: H10N 30/04 Treatments to modify a piezoelectric or electrostrictive property, e.g. polarisation characteristics, vibration characteristics or mode tuning
• CPC Class Codes: H10N 30/05 Manufacture of multilayered piezoelectric or electrostrictive devices, or parts thereof, e.g. by stacking piezoelectric bodies and electrodes
• CPC Class Codes: H10N 30/80 : Constructional details
• CPC Class Codes: Y10T 29/42 : Piezoelectric device making
• CPC Class Codes: Y10T 29/49005 : Acoustic transducer
• CPC Class Codes: Y10T 29/4908 : Acoustic transducer

Abstract

Methods are described for constructing a mechanical resonating structure by applying an active layer on a surface of a compensating structure. The compensating structure comprises one or more materials having an adaptive resistance to deform that reduces a variance in a resonating frequency of the mechanical resonating structure, wherein at least the active layer and the compensating structure form a mechanical resonating structure having a plurality of layers of materials A thickness of each of the plurality of layers of materials results in a plurality of thickness ratios therebetween.

Claims

1. A method of fabricating a mechanical resonating structure characterized by a resonance frequency (f0) and a zero temperature coefficient of frequency (T0), the method comprising:

applying an active layer on a compensating structure, wherein the compensating structure comprises one or more materials having an adaptive stiffness that reduces variation of the resonance frequency (f0);

applying a sacrificial layer on a surface of the active layer such that a portion of the active layer and a portion of the sacrificial layer are exposed, the sacrificial layer being a material different than the active layer; and

subsequent to applying the sacrificial layer, adjusting a thickness of the portion of the sacrificial layer to tune a value of f0 and a value of T0.

2. The method of claim 1, wherein the sacrificial layer is a conductor, wherein a configuration of the conductor causes a resonance mode of operation of the mechanical resonating structure to be influenced more by a lateral displacement than by a thickness displacement.

3. The method of claim 1, further comprising adjusting a thickness of the active layer.

4. The method of claim 3, wherein the compensating structure comprises first, second and third layers, wherein the second layer is formed between the first and third layers, wherein the first and third layers are formed of silicon dioxide, and wherein the second layer is formed of silicon.

5. The method of claim 1, further comprising forming a conductor on a surface of the compensating structure prior to applying the active layer.

6. The method of claim 1, wherein applying the sacrificial layer comprises applying the sacrificial layer in a configuration such that the portion of the active layer and the portion of the sacrificial layer are in a side-by-side configuration.

7. A method of fabricating a mechanical resonating structure characterized by a resonance frequency (f0) and a zero temperature coefficient of frequency (T0), the method comprising:

obtaining a mechanical resonating structure comprising an active layer and a compensating structure, wherein the compensating structure comprises one or more materials having an adaptive stiffness that reduces variation of the resonance frequency (f0);

patterning a trimming layer on the active layer; and

adjusting a thickness of the trimming layer to selectively tune a value of f0 and a value of T0.

8. The method of claim 7, wherein the trimming layer is a conductor, wherein a configuration of the conductor causes a resonance mode of operation of the mechanical resonating structure to be influenced more by a lateral displacement than by a thickness displacement.

9. The method of claim 7, further comprising adjusting a thickness of an exposed portion of the active layer.

10. The method of claim 9, wherein the compensating structure comprises first, second and third layers, wherein the second layer is formed between the first and third layers, wherein the first and third layers comprise silicon dioxide and the second layer comprises silicon.

11. The method of claim 7, wherein patterning the trimming layer comprises patterning the trimming layer to be side-by-side with an exposed portion of the active layer.

12. The method of claim 7, wherein patterning the trimming layer comprises patterning the trimming layer to have a greater surface area than an exposed portion of the active layer.

13. The method of claim 7, wherein the trimming layer is an electrode layer, and wherein patterning the trimming layer comprises patterning the trimming layer to form an interdigital transducer.