Sensor with separate actuator and sense fingers
First Claim
1. A micromachined device comprising:
- a member;
a suspension connected to the member and to a substrate, so that the member is movable relative to the substrate in response to a force applied to the device along a predetermined axis;
a sense differential capacitor having a first sense electrode connected to the substrate, a second sense electrode connected to the substrate, and a third sense electrode connected to the member, the sense differential capacitor including a first sense capacitor and a second sense capacitor, wherein the first sense capacitor includes the first sense electrode and the third sense electrode and the second sense capacitor includes the second sense electrode and the third sense electrode, and wherein the capacitances of the first sense capacitor and the second sense capacitor are oppositely variable in response to the force; and
an actuator differential capacitor having a first actuator electrode connected to the substrate, a second actuator electrode connected to the substrate, and a third actuator electrode connected to the member, the actuator differential capacitor including a first actuator capacitor and a second actuator capacitor, wherein the first actuator capacitor includes the first actuator electrode and the third actuator electrode and the second actuator capacitor includes the second actuator electrode and the third actuator electrode, and wherein the capacitances of the first actuator capacitor and the second actuator capacitor are oppositely variable in response to the force;
wherein the first sense electrode forms a separate electric node from the first actuator electrode, a separate electric node from the second actuator electrode, and a separate electric node from the third actuator electrode.
1 Assignment
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Accused Products
Abstract
A micromachined force sensor containing separate sensing and actuator structures. A member is suspended above the substrate so that it is movable along an axis in response to a force. The member includes a set of parallel sense fingers and a separate set of parallel force fingers. The sense fingers are positioned between fingers of two sense plates, to form a first differential capacitor, whose capacitance changes when the member moves in response to a force along the axis. The change in capacitance induces a sense signal on the member, which permits the measurement of the magnitude and duration of the force. The force fingers are positioned between fingers of two actuator plates, to form a second differential capacitor. The sense signal can be used to provide feedback to the second differential capacitor to generate different electrostatic forces between the force fingers and the two actuator plates, to offset the force applied along the preferred axis. Limit stops limit the movement of the member to less than the distance between the electrodes of the differential capacitors, to prevent contact between the electrodes. Additional fingers be positioned around the differential capacitors to minimize parasitic capacitances.
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Citations
32 Claims
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1. A micromachined device comprising:
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a member; a suspension connected to the member and to a substrate, so that the member is movable relative to the substrate in response to a force applied to the device along a predetermined axis; a sense differential capacitor having a first sense electrode connected to the substrate, a second sense electrode connected to the substrate, and a third sense electrode connected to the member, the sense differential capacitor including a first sense capacitor and a second sense capacitor, wherein the first sense capacitor includes the first sense electrode and the third sense electrode and the second sense capacitor includes the second sense electrode and the third sense electrode, and wherein the capacitances of the first sense capacitor and the second sense capacitor are oppositely variable in response to the force; and an actuator differential capacitor having a first actuator electrode connected to the substrate, a second actuator electrode connected to the substrate, and a third actuator electrode connected to the member, the actuator differential capacitor including a first actuator capacitor and a second actuator capacitor, wherein the first actuator capacitor includes the first actuator electrode and the third actuator electrode and the second actuator capacitor includes the second actuator electrode and the third actuator electrode, and wherein the capacitances of the first actuator capacitor and the second actuator capacitor are oppositely variable in response to the force; wherein the first sense electrode forms a separate electric node from the first actuator electrode, a separate electric node from the second actuator electrode, and a separate electric node from the third actuator electrode. - View Dependent Claims (4, 5, 6, 7, 8, 29)
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2. A micromachined device comprising:
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a plurality of anchors connected to a substrate; a member suspended above the substrate; a plurality of suspension arms suspended above the substrate, with each of the plurality of suspension arms having a first end connected to the member and a second end connected to one of the plurality of anchors, such that the member is movable along an axis parallel to the substrate; at least one sense capacitor cell, with each sense capacitor cell including a sense finger connected to the member, a first sense plate adjacent to a first side of the sense finger, and a second sense plate adjacent to a second side of the sense finger; and at least one actuator capacitor cell, with each actuator capacitor cell including an actuator finger connected to the member, a first actuator plate adjacent to the first side of the actuator finger and a second actuator plate adjacent to the second side of the actuator finger, wherein the at least one sense capacitor cell comprises a first differential capacitor and the at least one actuator capacitor cell comprises a second differential capacitor; and wherein the first sense plate of each sense capacitor cell forms a separate electric node from the actuator finger of each actuator capacitor cell, a separate electric node from the first actuator plate of each actuator capacitor cell, and a separate electric node from the second actuator plate of each actuator capacitor cell. - View Dependent Claims (20, 21, 22, 23, 24)
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3. A micromachined device comprising:
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a plurality of anchors connected to a substrate; a member suspended above the substrate having at least one member finger extending from the member, the member finger having a left side and a right side; a plurality of suspension arms suspended above the substrate, with each of the plurality of suspension arms having a first end connected to the member and a second end connected to one of the plurality of anchors so that the member is movable along a preferred axis parallel to the substrate; at least one left finger parallel to the at least one member finger, with one of the at least one left lingers being adjacent to the left side of each member finger, and the at least one left finger forming a first capacitor with the at least one member finger; at least one right finger parallel to the at least one member finger, with one of the at least one right fingers being adjacent to the right side of each member finger, at the at least one right finger forming a second capacitor with the at least one member finger; a polysilicon guard ring suspended above the substrate and encircling the member, the plurality of suspension arms, the at least one left finger, and the at least one right finger; a guard diffusion area diffused into the substrate under a portion of the guard ring; and a polysilicon guard anchor mechanically and electrically connecting the guard ring to the guard diffusion area.
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9. A micromachined device comprising:
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a plurality of anchors connected to a substrate; a member suspended above the substrate having at least one sense finger extending from the member, and at least one force finger extending from the member, parallel to the at least one sense finger; a plurality of suspension arms suspended above the substrate, with each of the plurality of suspension arms having a first end connected to the member and a second end connected to one of the plurality of anchors, so that the member is movable along a preferred axis parallel to the substrate; at least one first sense plate parallel to the at least one sense finger, with one of the at least one first sense plates being adjacent to a first side of each sense finger, and the at least one first sense plate forming a first sense capacitor with the at least one sense finger; at least one second sense plate parallel to the at least one sense finger with one of the at least one second sense plates being adjacent to a second side of each sense finger, and the at least one second sense plate forming a second sense capacitor with the at least one sense finger; at least one first actuator plate parallel to the at least one force finger, with one of the at least one first actuator plates being adjacent to the first side of each force finger, and the at least one first actuator plate forming a first actuator capacitor with the at least one force finger; and at least one second actuator plate parallel to the at least one force finger, with one of the at least one second actuator plates being adjacent to the second side of each force linger, and the at least one second actuator plate forming a second actuator capacitor with the at least one force finger; wherein the at least one first sense plate forms a separate electric node from the at least one force finger, a separate electric node from the at least one first actuator plate, and a separate electric node from the at least one second actuator plate. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 25, 26, 27, 28, 30, 31, 32)
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Specification