Method of fabricating quartz resonators

• US 8,176,607 B1
• Filed: 10/08/2009
• Issued: 05/15/2012
• Est. Priority Date: 10/08/2009
• Status: Active Grant

• Current Assignee: HRL Laboratories LLC (The Boeing Co.)
• Original Assignee: HRL Laboratories LLC (The Boeing Co.)
• Inventors: Kubena, Randall L., Hsu, Tsung-Yuan
• Primary Examiner(s): Tugbang, A. Dexter
• Application Number:
  US12/575,634
• Time in Patent Office: 950 Days
• Field of Search: 298/901, 295/94, 29/253.5, 298/46, 298/52, 310/324, 310/365, 310/366, 347/70, 347/71
• US Class Current: 29/25.35
• CPC Class Codes: H04R 17/00 Piezoelectric transducers; Electrostrictive transducers piezoelectric or electrostrictive elements in general H10N30/00; details of piezoelectric or electrostrictive motors, generators or positioners H10N30/00
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/49165 by forming conductive walled aperture in base
• CPC Class Codes: Y10T 29/49401 Fluid pattern dispersing device making, e.g., ink jet

Abstract

A method for fabricating VHF and/or UHF quartz resonators (for higher sensitivity) in a cartridges design with the quartz resonators requiring much smaller sample volumes than required by conventional resonators, and also enjoying smaller size and more reliable assembly. MEMS fabrication approaches are used to fabricate with quartz resonators in quartz cavities with electrical interconnects on a top side of a substrate for electrical connection to the electronics preferably through pressure pins in a plastic module. An analyte is exposed to grounded electrodes on a single side of the quartz resonators, thereby preventing electrical coupling of the detector signals through the analyte. The resonators can be mounted on the plastic cartridge or on arrays of plastic cartridges with the use of inert bonding material, die bonding or wafer bonding techniques. This allows the overall size, cost, and required biological sample volume to be reduced while increasing the sensitivity for detecting small mass changes.

Claims

1. A method of fabricating quartz resonators comprising:

forming electrodes, pads, and interconnects on a first side of a piezoelectric quartz wafer;

bonding the piezoelectric quartz wafer to one or more handle wafers;

etching vias in the piezoelectric quartz wafer;

forming electrodes and interconnects on a second side of the piezoelectric quartz wafer;

forming metal plugs in said vias to connect the electrodes on said second side of said piezoelectric quartz wafer to the pads on said first side of said piezoelectric quartz wafer;

dicing the piezoelectric quartz wafer along dicing lines formed therein to thereby define a plurality of dies, each die having at least one metal electrode formed on the first side of the piezoelectric quartz wafer thereof and at least one opposing metal electrode formed on the second side of the piezoelectric quartz wafer thereof;

adhering the dies to a substrate with fluid ports therein, the fluid ports being associated with the metal electrodes formed on the first side of the die, thereby forming at least one fluid flow cell in each die with the at least one metal electrode formed on the first side of the piezoelectric quartz wafer in said at least one fluid flow cell and at least one opposing metal electrode formed on the second side of the piezoelectric quartz wafer of said at least one die opposite said at least one fluid flow cell; and

removing the one or more handle wafers, thereby exposing the pads on the first side of the dies, said pads on the first side of the dies, in use, providing circuit connection points for allowing electrical excitation of the metal electrodes on the first side of the dies and the opposing metal electrodes on the second side of the dies.

2. The method of fabricating quartz resonators according to claim 1 further comprising etching inverted mesas in the first side of the piezoelectric quartz wafer wherein the electrodes formed on said first side are disposed within one or more of said inverted mesas.

3. The method of fabricating quartz resonators according to claim 2 further comprising etching inverted mesas in the second side of the piezoelectric quartz wafer wherein the electrodes formed on said second side of the piezoelectric quartz wafer are disposed within one or more of said inverted mesas formed on said second side of the piezoelectric quartz wafer.

4. The method of fabricating quartz resonators according to claim 3 in which the inverted mesas are etched with a plasma etch.

5. The method of fabricating quartz resonators according to claim 1 further comprising etching inverted mesas in the second side of the piezoelectric quartz wafer wherein the electrodes formed on said second side of the piezoelectric quartz wafer are disposed within one or more of said inverted mesas formed on said second side of the piezoelectric quartz wafer.

6. The method of fabricating quartz resonators according to claim 5 in which the inverted mesas are etched with a plasma etch.

7. The method of fabricating quartz resonators according to claim 1 further comprising thinning the piezoelectric quartz wafer to 2-50 microns in an active resonator region between the electrodes formed on said first and second sides of the piezoelectric quartz wafer.

8. The method of fabricating quartz resonators according to claim 1 wherein the dies are adhered to said substrate with the fluid ports therein using an inert polyimide-based tape or an epoxy adhesive.

9. The method of fabricating quartz resonators according to claim 1 wherein the one or more handle wafers is removed with a fluorine-based plasma etch and/or XeF₂.

10. A method of analyzing an analyte using a quartz resonator made in accordance with claim 1 wherein the electrode on the second side of the piezoelectric quartz wafer is grounded and the analyte is exposed to the grounded electrode on the second side of the piezoelectric quartz wafer, thereby preventing electrical coupling of detector signals, obtained from the electrode on the first side of the piezoelectric quartz wafer, to the analyte.

11. The method of fabricating quartz resonators comprising according to claim 1 wherein electrodes formed on the second side of the piezoelectric quartz wafer directly oppose electrodes formed on the first side of the piezoelectric quartz wafer.

12. A method of fabricating a quartz resonator comprising:

forming electrode, pads, and interconnects on a first side of a piezoelectric quartz wafer;

bonding the piezoelectric quartz wafer to a handle wafer;

forming at least one via in the piezoelectric quartz wafer;

forming an electrode on a second side of the piezoelectric quartz wafer;

forming at least one metal plug in said at least one via and connecting the electrode on said second side of said piezoelectric quartz wafer to one of the pads on said first side of said piezoelectric quartz wafer;

adhering said piezoelectric quartz wafer to a substrate with fluid ports therein, the fluid ports being aligned to the electrode on the second side of the piezoelectric quartz wafer, thereby forming a flow cell in the quartz resonator with the electrode formed on the second side of the piezoelectric quartz wafer being disposed in said flow cell and the electrode formed on the first side of the piezoelectric quartz wafer being disposed opposite said flow cell; and

removing the handle wafer, thereby exposing the pads on the first side of the piezoelectric quartz wafer, said pads on the first side of the piezoelectric quartz wafer, in use, providing circuit connection points for allowing electrical excitation of the electrodes on the first and second sides of the piezoelectric quartz wafer.

13. The method of fabricating a quartz resonator according to claim 12 further comprising etching one or more inverted mesas in the first side of the piezoelectric quartz wafer wherein the metal electrode formed on said first side is disposed within one of said one or more inverted mesas.

14. The method of fabricating a quartz resonator according to claim 13 further comprising etching one or more inverted mesas in the second side of the piezoelectric quartz wafer wherein the metal electrode formed on said second side of the piezoelectric quartz wafer is disposed within one of said one or more inverted mesas formed on said second side of the piezoelectric quartz wafer.

15. The method of fabricating a quartz resonator according to claim 14 wherein a plurality of electrodes are formed in a plurality of inverted mesas formed in the first side of the piezoelectric quartz wafer and a plurality of electrodes are formed in a plurality of inverted mesas formed in the second side of the piezoelectric quartz wafer, the inverted mesas in the first side of the piezoelectric quartz wafer opposing corresponding inverted mesas in the second side of the piezoelectric quartz wafer and the electrodes formed in inverted mesas in the first side of the piezoelectric quartz wafer opposing the corresponding electrodes formed in inverted mesas in the second side of the piezoelectric quartz wafer.

16. The method of fabricating a quartz resonator according to claim 12 further comprising etching one or more inverted mesas in the second side of the piezoelectric quartz wafer wherein the metal plug formed on said second side of the piezoelectric quartz wafer is disposed within one of said one or more inverted mesas formed on said second side of the piezoelectric quartz wafer.

17. The method of fabricating a quartz resonator according to claim 16 in which the inverted mesas are etched with a plasma etch.

18. The method of fabricating quartz resonators according to claim 12 further comprising thinning the piezoelectric quartz wafer to 2-50 microns in an active resonator region between opposing electrodes formed on said first and second sides of the piezoelectric quartz wafer.

19. The method of fabricating quartz resonators according to claim 12 wherein the piezoelectric quartz wafer is adhered to said substrate with the fluid ports therein using an inert polyimide-based tape or an epoxy adhesive.

20. The method of fabricating quartz resonators according to claim 12 wherein the one or more handle wafers is removed with a fluorine-based plasma etch and/or XeF₂.

21. A method of analyzing an analyte using a quartz resonator made in according with claim 12 wherein the electrode on the second side of the piezoelectric quartz wafer is grounded and the analyte is exposed to the grounded electrodes on the second side of the piezoelectric quartz wafer, thereby preventing electrical coupling of detector signals, obtained from the electrode on the first side of the piezoelectric quartz wafer, to the analyte.

22. The method of fabricating quartz resonators according to claim 12 wherein the electrode on the second side of the piezoelectric quartz wafer directly opposes the electrode on the first side of the piezoelectric quartz wafer.