Micro-machined resonator

• US 5,198,716 A
• Filed: 12/09/1991
• Issued: 03/30/1993
• Est. Priority Date: 12/09/1991
• Status: Expired due to Fees

• Current Assignee: Sandia Corporation (Martin Marietta Corporation)
• Original Assignee: United States Department of Energy (Government of the United States of America)
• Inventors: Godshall, Ned A., Liang, Alan Y., Smith, Bradley K., Koehler, Dale R.
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US07/803,815
• Time in Patent Office: 477 Days
• Field of Search: 310/328, 310/361, 310/346, 310/349, 310/353, 310/344, 310/343, 310/348, 310/320
• US Class Current: 310/349
• CPC Class Codes: H03H 9/1035 the enclosure being defined by two sealing substrates sandwiching the piezoelectric layer of the BAW device

Abstract

A micro-machined resonator, typically quartz, with upper and lower micro-machinable support members, or covers, having etched wells which may be lined with conductive electrode material, between the support members is a quartz resonator having an energy trapping quartz mesa capacitively coupled to the electrode through a diaphragm; the quartz resonator is supported by either micro-machined cantilever springs or by thin layers extending over the surfaces of the support. If the diaphragm is rigid, clock applications are available, and if the diaphragm is resilient, then transducer applications can be achieved. Either the thin support layers or the conductive electrode material can be integral with the diaphragm. In any event, the covers are bonded to form a hermetic seal and the interior volume may be filled with a gas or may be evacuated. In addition, one or both of the covers may include oscillator and interface circuitry for the resonator.

Claims

1. A micro-machined resonator, comprising:

(a) an upper micro-machinable support member having an upper well connected to an upper electrode means;

(b) a lower micro-machinable support member having a lower well connected to a lower electrode means, said lower support member opposing said upper support member;

(c) a resonator capacitively coupled to said electrodes, said resonator having a centrally located energy trapping quartz mesa and supported between said upper well of said upper support member and said lower well of said lower support member;

(d) an upper diaphragm interposed between said upper well and said resonator;

(e) a lower diaphragm interposed between said lower well and said resonator;

(f) spacer means for defining a volume between said micro-machinable support members and said resonator; and

(g) support means for supporting said resonator in said volume.

2. The resonator of claim 1, wherein said micro-machinable support members are fabricated from a group including silicon, glass, quartz, and gallium arsenide.

3. The resonator of claim 1, wherein said upper micro-machinable support member and said lower micro-machinable support member are bonded together to create a hermetic seal.

4. The resonator of claim 3, wherein said support members are coated with a material to facilitate electric field assisted bonding.

5. The resonator of claim 3, wherein said volume between said micro-machinable support members and said resonator is filled with a gas.

6. The resonator of claim 3, wherein said volume between said micro-machinable support members and said resonator is a vacuum.

7. The resonator of claim 2, wherein said upper and lower diaphragms are resilient.

8. The resonator of claim 2, wherein said upper and lower diaphragms are rigid.

9. The resonator of claim 2, wherein said electrodes further comprise an upper conductive layer in contact with said upper well and a lower conductive layer in contact with said lower well.

10. The resonator of claim 9, wherein said electrodes and said diaphragms are integral.

11. The resonator of claim 2, wherein said spacer means is a spacer ring circumscribing said resonator placed between said upper and lower micro-machinable support members.

12. The resonator of claim 11, wherein said spacer means and said resonator are integral and fabricated from quartz.

13. The resonator of claim 2, wherein at least one of said micro-machinable support members comprises circuit means integrated into said micro-machinable support member for controlling and receiving electrical signals generated by said resonator sent through said electrodes.

14. The resonator of claim 13, wherein said circuit means further comprises oscillator and interface circuitry.

15. The resonator of claim 2, wherein said support means are cantilever spring means attached to said upper and lower micro-machinable support members.

16. The resonator of claim 15, wherein said cantilever springs means are fabricated from silicon dioxide.

17. The resonator of claim 15, wherein said cantilever springs means are fabricated from silicon nitride.

18. The resonator of claim 2, wherein said support means are membrane layers on said support members toward said resonator, said membrane layers support said mesa of said resonator, and said membrane layers are fabricated from one of the group consisting of silicon, silicon dioxide, or silicon nitride.

19. A micro-machined quartz resonator comprising:

(a) an upper micro-machinable support member having an upper coated etched portion and an upper outer portion circumscribing said upper coated etched portion;

(b) a lower micro-machinable support member having a lower coated etched portion and a lower outer portion circumscribing said lower coated etched portion;

(c) a quartz resonator having a centrally located energy trapping quartz mesa, said resonator being located between said upper and lower micro-machinable support members in a volume defined by said upper and lower etched portions;

(d) cantilever spring means for supporting said resonator in said volume between said micro-machinable support members for supporting said quartz resonator wherein said cantilever spring means are located on said outer portions of said upper and lower micro-machinable support members and extending over said etched portions of said upper and lower micro-machinable support members and wherein said cantilever spring means are not physically bonded or otherwise rigidly attached to said resonator; and

(e) spacer means, located adjacent to said quartz resonator and between said upper and lower micro-machinable support members and having a coating for forming a hermetic seal between said upper micro-machinable support and said lower micro-machinable support member.

20. A micro-machined quartz resonator comprising:

(a) an upper micro-machinable support member having an upper coated etched portion and an upper outer portion circumscribing said upper coated etched portion;

(b) a lower micro-machinable support member having a lower coated etched portion and a lower outer portion circumscribing said lower coated etched portion;

(c) a quartz resonator having a centrally located energy trapping quartz mesa, said resonator being located between said upper and lower micro-machinable support members in a volume defined by said upper and lower etched portions;

(d) cantilever spring means for supporting said resonator in said volume between said micro-machinable support members for supporting said quartz resonator wherein said cantilever spring means are located on said outer portions of said upper and lower micro-machinable support members and extending over said etched portions of said upper and lower micro-machinable support members, said cantilever springs means are fabricated from one of the group consisting of silicon dioxide, silicon nitride, and single crystal silicon; and

(e) spacer means, located adjacent to said quartz resonator and between said upper and lower micro-machinable support members and having a coating for forming a hermetic seal between said upper micro-machinable support and said lower micro-machinable support member.

21. The resonator of claim 20, wherein said bond layer on said upper support member extends across said upper etched portion, and said bond layer on said lower support member extends across said lower support member, and said bond layer and said diaphragm are integral.

22. The resonator of claim 20, wherein said bond layer on said upper support member extends to said upper etched portion, and said bond layer on said lower support member extends to said lower etched portion, and said conductive layer and said diaphragm are integral.

23. The resonator of claim 20, wherein said diaphragms are rigid.

24. The resonator of claim 20, wherein said diaphragms are resilient.

25. A micro-machined resonator comprising:

(a) an upper micro-machinable support member having an upper etched portion and an upper outer portion, said upper etched portion lined with a conductive layer to form an upper electrode;

(b) a lower micro-machinable support member having a lower coated etched portion and a lower outer portion, said lower etched portion lined with a conductive layer to form a lower electrode;

(c) a support bond layer deposited on said upper outer portion and said lower outer portion for forming a hermetic seal between said upper micro-machinable support member and said lower micro-machinable support member;

(d) a resonator capacitively coupled to said electrodes, said resonator having a centrally located energy trapping quartz mesa, and situated between said upper and lower micro-machinable support members in a volume defined by said upper and lower etched portions, said resonator supported by said support bond layer;

(e) spacer means, circumscribing said quartz resonator and situated between said upper and lower micro-machinable support members to suspend said resonator in said volume; and

(f) an upper diaphragm between said upper electrode and said resonator;

(g) a lower diaphragm between said lower electrode and said resonator; and

(h) circuit means integrated into at least one of said micro-machinable support members for controlling and receiving electrical signals generated by said resonator sent through said electrodes.

26. A micro-machined quartz resonator comprising:

(a) an upper micro-machinable support member having an upper coated etched portion and an upper outer portion circumscribing said upper coated etched portion wherein said upper coated etched portion is coated with a layer fabricated from one of the group consisting of silicon dioxide or silicon nitride;

(b) a lower micro-machinable support member having a lower coated etched portion and a lower outer portion circumscribing said lower coated etched portion wherein said lower coated etched portion is coated with a layer fabricated from one of the group consisting of silicon dioxide or silicon nitride;

(c) a quartz resonator having a centrally located energy trapping quartz mesa, said resonator being located between said upper and lower micro-machinable support members in a volume defined by said upper and lower etched portions;

(d) support means for supporting said resonator in said volume between said micro-machinable support members for supporting said quartz resonator; and

(e) spacer means, located adjacent to said quartz resonator and between said upper and lower micro-machinable support members and having a coating for forming a hermetic seal between said upper micro-machinable support and said lower micro-machinable support member.