THREE-DIMENSIONAL WAFER-SCALE BATCH-MICROMACHINED SENSOR AND METHOD OF FABRICATION FOR THE SAME

• US 20110239763A1
• Filed: 09/29/2010
• Published: 10/06/2011
• Est. Priority Date: 10/12/2009
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Prikhodko, Igor P., Zotov, Sergei A., Trusov, Alexander A., Shkel, Andrei M.
• Granted Patent: US 8,567,247 B2
• Time in Patent Office: Days
• US Class Current: 73/504.13
• CPC Class Codes: B29C 44/02 for articles of definite length, i.e. discrete articles
• CPC Class Codes: B29C 44/022 Foaming unrestricted by cavity walls, e.g. without using moulds or using only internal cores
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01C 19/5691 of essentially three-dimensional vibrators, e.g. wine glass-type vibrators

Abstract

A vibratory sensor is fabricated as a three-dimensional batch-micromachined shell adapted to vibrate and support elastic wave propagation and wave precession in the shell or membrane and at least one driving electrode and preferably a plurality of driving electrodes directly or indirectly coupled to the shell to excite and sustain the elastic waves in the shell. The pattern of elastic waves is determined by the configuration of the driving electrode(s). At least one sensing electrode and preferably a plurality of sensing electrodes are provided to detect the precession of the elastic wave pattern in the shell. The rotation of the shell induces precession of the elastic wave pattern in the shell which is usable to measure the rotation angle or rate of the vibratory sensor.

Claims

16. A method for batch fabrication of three-dimensional shells used as vibrational membranes for a vibratory sensor comprising:

defining a plurality of cavities of a predetermined volume into a substrate prior to glassblowing;

disposing a planar thermoplastically deformable layer over the substrate and trapping a gas in the cavities of a predetermined volume; and

self-inflating the shells through the thermoplastically deformable layer by heating the thermoplastically deformable layer to a plastic state and gas in the plurality of cavities.

1. A vibratory sensor comprising:

a three-dimensional batch-micromachined shell adapted to vibrate and support elastic wave propagation and precession in the shell;

at least one driving electrode to excite and sustain elastic waves in the shell, the pattern of elastic wave being determined by configuration of the at least one driving electrode; and

at least one sensing electrode to detect a vibratory characteristic in the shell induced by interaction of the shell with a force or field which is sensed or measured thereby.

2. The vibratory sensor of claim 1 where the at least one sensing electrode detects precession of the elastic wave pattern in the shell;

and

where rotation of the shell induces precession of the elastic wave pattern in the shell usable to measure the rotation angle or rate.

3. The vibratory sensor of claim 1 further comprising a plurality of driving electrodes to excite and sustain elastic waves in the shell, the pattern of elastic wave being determined by configuration of the plurality of driving electrodes.

4. The vibratory sensor of claim 1 further comprising a plurality of sensing electrodes to detect precession of the elastic wave pattern in the shell.

5. The vibratory sensor of claim 1 where the at least one driving electrode comprises a three-dimensional transducer.

6. The vibratory sensor of claim 1 where the at least one sensing electrode comprises a three-dimensional support structure.

7. The vibratory sensor of claim 1 where the three-dimensional batch-micromachined shell comprises an at least partially spherical shell.

8. The vibratory sensor of claim 1 where the three-dimensional batch-micromachined shell comprises an at least partially hemispherical shell.

9. The vibratory sensor of claim 1 where the sensing or driving electrodes are disposed on or in an at least partially formed torus circumscribing the shell.

10. The vibratory sensor of claim 1 further comprising a base and where the three-dimensional batch-micromachined shell comprises an at least partially hemispherical shell with a stem coupled to the base.

11. The vibratory sensor of claim 1 where the at least one driving electrode comprises a three dimensional capacitive transducer comprised in turn of a stack of an inner and outer conductive film with an interlying dielectric layer therebetween, the stack being disposed on the shell, configuration of the stack defining an elastic wave pattern in the shell when driven by the stack.

12. The vibratory sensor of claim 11 where the at least one driving electrode comprises a three dimensional capacitive transducer comprised in turn of a plurality of stacks, each having an inner and outer conductive film with an interlying dielectric layer therebetween, the plurality of stacks being disposed on the shell, configuration of the plurality of stacks defining an elastic wave pattern in the shell when driven by the plurality of stacks.

13. The vibratory sensor of claim 1 where the at least one driving electrode comprises a piezoelectric layer disposed on the shell.

14. The vibratory sensor of claim 1 further comprising a first and second wafer and where the shell is mounted on the first wafer and where the at least one driving and sensing electrodes are defined on separate dies comprising the second wafer, where the shell is provided with a conductive layer to enable capacitive detection and actuation by the driving and sensing electrodes, the second wafer being self-aligned with the shell during self-inflation of the shell inside a pre-etched opening defined through the second wafer, where during basic glassblowing the shell expands and fills the cylindrical opening thus providing alignment and bonding to the second wafer.

15. The vibratory sensor of claim 12 where the stack comprises a pair of submicron-gap capacitive electrodes disposed on the shell.

17. The method of claim 16 where self-inflating the shells through the thermoplastically deformable layer self-inflates the shells into free space thereby forming spherical shells and further comprising etching away or physically removing an upper portion of the spherical shells to form hemispherical shells.

18. The method of claim 17 where etching away or physically removing an upper portion of spherical shells to form hemispherical shells comprises disposing a masking material on the spherical shells and selective etching the shells, or encapsulating the shells with a sacrificial material and polishing or lapping down the encapsulated shells to form hemispherical shells.

19. The method of claim 16 further comprising forming a stem on each of the shells by disposing a stencil layer to the planar thermoplastically deformable layer prior to self-inflating the shells, the stencil layer having stem holes defined therethrough to define the shape of the stems, and self-inflating the shells through the stem holes of the stencil layer.

20. The method of claim 19 further comprising etching away or physically removing an upper portion of spherical shells to form shells with a wine-glass shape.

21. The method of claim 16 where defining a plurality of cavities of a predetermined volume into a substrate prior to glassblowing comprises defining a plurality of continuous ring cavities into the substrate prior to glassblowing to provide toroidal shells.

22. The method of claim 16 comprising:

selectively disposing conductive patterning on the planar thermoplastically deformable substrate prior to glassblowing; and

forming a predetermined three-dimensional metal pattern on the surface of the shell during self-inflating where the metal pattern plastically deforms along with the self-inflation of the thermoplastically deformable substrate.

23. The method of claim 16 further comprising:

disposing a selected layer of material on or in the formed shells; and

dissolving the formed thermoplastically deformable shell leaving a shell composed of the selected layer of material.

24. The method of claim 16 comprising:

selectively disposing conductive patterning on the planar thermoplastically deformable substrate prior to glassblowing;

selectively disposing a sacrificial layer of material on the patterning on the planar thermoplastically deformable substrate prior to glassblowing;

forming a predetermined three-dimensional conductive pattern on the surface of the shell during self-inflating where the conductive pattern covered with the sacrificial material plastically deforms along with the self-inflation of the thermoplastically deformable substrate;

fusing two or more shells covered with the sacrificially coated conductive pattern; and

removing the sacrificial layer to form three-dimensional submicron-gap capacitive electrodes on the surface of the shells.

26. The method of claim 16 further comprising chemically treating the shells to decrease roughness and improve performance of the MSRG formed therefrom by polishing of an inner and outer surface of the shells by means of wet or vapor phase of processing.

27. The method of claim 16 where disposing a planar thermoplastically deformable layer over the substrate and trapping a gas in the cavities of a predetermined volume comprises thermoplastically deformable-to-thermoplastically deformable bonding of the planar thermoplastically deformable layer to the substrate where the substrate is comprised of a quartz wafer using a thin film as an intermediate layer for bonding.

28. The method of claim 19 further comprising defining significantly narrower stem holes in the stencil wafer in comparison with the cavity size defined in the substrate to fabricate a variably sized shell.

29. The method of claim 16 further comprising independently controlling the volume of the gas trapped in the cavities to fabricate a variably sized shell.

30. The method of claim 16 further comprising providing a substrate selected from the materials consisting of the group of silicon, titania silicate, fused quartz, graphite, and silicon carbide.

24-1. The method of claim 16 further comprising:

disposing a selected layer of material on or in the formed shells or disposing a selected layer of material on the planar layer prior to glassblowing and plastically deforming the selected layer with the self-inflation of the thermoplastically deformable substrate; and

employing the selected layer on the formed shell as a dielectric layer of an internal dielectric transducer or piezoelectric layers for electromechanical transduction, or providing additional layers on the formed shells using micromachining, including combinations of patterning and doping of deposited materials.