Comb drive micromechanical tuning fork gyro fabrication method
First Claim
1. A method for fabricating a comb drive tuning fork structure adapted for inertial rate sensitivity comprising the steps of:
- providing a silicon substrate;
forming in a surface of said substrate a plurality of sense electrodes electrically isolated from each other and electrically contactable through a surface portion of said substrate;
supporting, over the surface of said substrate having said plurality of sense electrodes, by flexures for rotation about an axis through said flexures, an assembly of first and second vibratable elements supported at opposite ends by first and second support electrodes such that said vibratable elements extend either side of said axis of rotation and have, extending away therefrom, first and second sets of driven electrodes on one side and first and second respective masses on the other side;
forming on said substrate first and second drive electrodes which mesh with said first and second driven electrodes of said vibratable elements and electrical contacts for said first and second flexures.
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Abstract
A microfabricated, tuning fork rate sensitive structure and drive electronics in which vibrational forces are communicated through a set of meshing drive and driven finger electrodes associated with each of two vibrating elements. The vibrating elements are supported in a rotatable assembly between first and second support electrodes which are in turn suspended by flexures for rotation about an axis passing through the flexures and through a point midway between the vibrating elements. Additional masses are formed onto the vibrating elements to improve overall sensor sensitivity. Sense electrodes for detecting capacitive changes between the support electrodes and the sense electrodes are positioned at each end of the support electrodes. Drive electronics are connected between the driven fingers of the vibrating elements and the drive electrode fingers which mesh with them to cause vibration. Excitation is provided between the support electrodes and the sense electrodes. Any change in signal resulting from rotation of the assembly and the resulting variation in capacitance between the support electrodes and the sense electrodes is sensed as a measure of inertial rate. A torque loop may be additionally formed using the sense electrodes in order to re-torque the assembly to a neutral position in a torque-to-balance loop.
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Citations
14 Claims
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1. A method for fabricating a comb drive tuning fork structure adapted for inertial rate sensitivity comprising the steps of:
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providing a silicon substrate; forming in a surface of said substrate a plurality of sense electrodes electrically isolated from each other and electrically contactable through a surface portion of said substrate; supporting, over the surface of said substrate having said plurality of sense electrodes, by flexures for rotation about an axis through said flexures, an assembly of first and second vibratable elements supported at opposite ends by first and second support electrodes such that said vibratable elements extend either side of said axis of rotation and have, extending away therefrom, first and second sets of driven electrodes on one side and first and second respective masses on the other side; forming on said substrate first and second drive electrodes which mesh with said first and second driven electrodes of said vibratable elements and electrical contacts for said first and second flexures. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 11, 14)
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10. A process for forming a comb driven tuning fork structure for use in rate sensor applications comprising the steps of:
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providing a silicon substrate having a planar surface; forming in said planar surface a plurality of sense electrodes through an insulating layer aperture; providing a second silicon substrate having a planar surface into which is diffused an etch resistant diffusant; bonding said first and second silicon substrates planar surface to planar surface; forming in said diffusion layer an assembly comprising flexures extending to regions of said insulating layer of said first substrate and having vibratable elements supported by electrode elements spaced parallel to each other about a rotation axis passing through said flexures with said vibratable elements having on one respective sides thereof a mass and on opposite respective sides thereof a plurality of driven electrodes in first and second sets forming separated fingers; forming in said diffusion layer and physically separated from said assembly a plurality of drive electrodes comprising fingers fitting between the fingers of said driven electrodes. - View Dependent Claims (12, 13)
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Specification