Micromachined accelerometer with monolithic electrodes and method of making the same
First Claim
1. A micromachined sensor assembly, for use in a capacitive accelerometer, comprising:
- (a) a spring-mass-support structure, said spring-mass-support structure having a top side and a bottom side,(b) a top cap bonded on the top side of said spring-mass-support structure, and(c) a bottom cap bonded on the bottom side of said spring-mass-support structure,(d) a bonding means for bonding said top cap on the top side of said spring-mass-support structure and bonding said bottom cap on the bottom side of said spring-mass-support structure;
wherein said spring-mass-support structure comprises a frame, a pair of branched torsional beams, and a proof mass plate, said proof mass plate having a center of mass and a torsional axis;
wherein each one of said pair of branched torsional beams comprises a stem beam coupled to said frame and two branch beams coupled to said proof mass plate such that said proof mass plate is suspended by said pair of torsional beams, said torsional axis is offset from said center of mass in a direction perpendicular to said proof mass plate;
wherein said proof mass plate comprises cutout spaces to receive each one of said pair of torsional beams such that said torsional beams are substantially located within said cutout spaces of said proof mass plate.
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Abstract
A capacitive accelerometer having one or more micromachined acceleration sensor assembly is disclosed. The acceleration sensor assembly comprises a spring-mass-support structure, a top cap and a bottom cap. The proof mass plate of the spring-mass-support structure has cutout spaces and is supported by a pair of branched torsional beams which are substantially located in the cutout spaces. The torsional axis of the proof mass plate is offset from the mass center in direction perpendicular to the proof mass plate. The acceleration sensor assembly further comprises multiple coplanar electrodes for differential capacitive sensing and electrostatic forcing. The capacitive accelerometer according to the present invention may comprise one, two or six micromachined acceleration sensor assemblies with electronic signal detection, conditioning and control circuits in different configurations and applications to detect and measure linear and angular accelerations. Methods to fabricate the micromachined acceleration sensor assembly are disclosed.
54 Citations
19 Claims
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1. A micromachined sensor assembly, for use in a capacitive accelerometer, comprising:
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(a) a spring-mass-support structure, said spring-mass-support structure having a top side and a bottom side, (b) a top cap bonded on the top side of said spring-mass-support structure, and (c) a bottom cap bonded on the bottom side of said spring-mass-support structure, (d) a bonding means for bonding said top cap on the top side of said spring-mass-support structure and bonding said bottom cap on the bottom side of said spring-mass-support structure; wherein said spring-mass-support structure comprises a frame, a pair of branched torsional beams, and a proof mass plate, said proof mass plate having a center of mass and a torsional axis; wherein each one of said pair of branched torsional beams comprises a stem beam coupled to said frame and two branch beams coupled to said proof mass plate such that said proof mass plate is suspended by said pair of torsional beams, said torsional axis is offset from said center of mass in a direction perpendicular to said proof mass plate; wherein said proof mass plate comprises cutout spaces to receive each one of said pair of torsional beams such that said torsional beams are substantially located within said cutout spaces of said proof mass plate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An accelerometer comprising at least one micromachined sensor assembly and an electronic signal detection, conditioning and control circuit, said micromachined sensor assembly comprising:
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(a) a spring-mass-support structure, said spring-mass-support structure having a top side and a bottom side, (b) a top cap, (c) a bottom cap, (d) a bonding means for bonding said top cap on the top side of said spring-mass-support structure and bonding said bottom cap on the bottom side of said spring-mass-support structure; wherein said spring-mass-support structure comprises a frame, a pair of branched torsional beams, and a proof mass plate, said proof mass plate having a center of mass and a torsional axis; wherein each one of said pair of branched torsional beams comprises a stem beam coupled to said frame and two branch beams coupled to said proof mass plate such that said proof mass plate is suspended with said pair of torsional beams, said torsional axis is offset from said center of mass in a direction perpendicular to said proof mass plate; wherein said proof mass plate comprises cutout spaces to receive each one of said pair of torsional beams such that said torsional beams are substantially located within said cutout spaces of said proof mass plate. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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Specification