CAPACITIVE ACCELEROMETER DEVICES AND WAFER LEVEL VACUUM ENCAPSULATION METHODS
First Claim
1. A device comprising:
- a substrate;
a microelectromechanical system (MEMS) comprising a plurality of integer N frames disposed within each other with the inner N−
1 frames being suspended with respect to the substrate, the outermost frame attached to the substrate, and the innermost frame providing a proof mass;
a plurality of N−
1 sets of springs, each set of springs being of a predetermined design and attached from a first predetermined frame of the plurality of N frames to a second predetermined frame of the plurality of N frames;
a plurality of M comb drive pairs, each comb drive pair comprising first and second comb drives attached at opposite sides of a third predetermined frame of the plurality of N frames to a fourth predetermined frame of the plurality of N frames.
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Accused Products
Abstract
Silicon-based capacitive accelerometers are relatively simple to fabricate and offer low cost, small size, low power, low noise and provide high sensitivity, good DC response, low drift, and low temperature sensitivity. However, tri-axial accelerometers, as opposed to using multiple discrete accelerometers, require very low cross-axis sensitivity and close sensitivities across the three directions. It would be beneficial to provide a design methodology for such tri-axial accelerometers which is compatible with commercial MEMS manufacturing processes in order to remove requirements for device specific processing, non-standard processing, etc. Accordingly, tri-axial accelerometers with low cross axis sensitivity have been established exploiting decoupled frames in conjunction with axis specific spring designs. Further, exploitation of differential capacitive transduction using an asymmetric configuration for in-plane measurements along X- and Y-axis and an absolute measurement along Z-axis allows the manufacturing upon a commercial MEMS foundry process.
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Citations
17 Claims
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1. A device comprising:
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a substrate; a microelectromechanical system (MEMS) comprising a plurality of integer N frames disposed within each other with the inner N−
1 frames being suspended with respect to the substrate, the outermost frame attached to the substrate, and the innermost frame providing a proof mass;a plurality of N−
1 sets of springs, each set of springs being of a predetermined design and attached from a first predetermined frame of the plurality of N frames to a second predetermined frame of the plurality of N frames;a plurality of M comb drive pairs, each comb drive pair comprising first and second comb drives attached at opposite sides of a third predetermined frame of the plurality of N frames to a fourth predetermined frame of the plurality of N frames. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A device comprising:
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a fixed frame; a first frame disposed within an opening within the fixed frame connected to the fixed frame by a plurality of first springs; a second frame disposed within an opening within the first frame connected to the first frame by a plurality of second springs; a proof mass disposed within an opening within the second frame connected to the second frame by a plurality of third springs;
whereineach of the first and second frames have a first axis of the respective frame longer than a second axis of the respective frame and the first axes of the first and second frames are orthogonal to each other. - View Dependent Claims (10, 11, 12, 13)
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14. A method comprising:
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linking a proof mass to a first frame by a plurality of first springs that support motion of the proof mass out of the plane within which the proof mass and the plurality of first springs are manufactured; linking the first frame to an outer frame by a plurality of second springs that support motion of the first frame in the plane within which the first frame and the plurality of second springs are manufactured;
anproviding a pair of drive combs attached to the outer frame. - View Dependent Claims (15, 16, 17)
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Specification