Ground shield capacitor
First Claim
Patent Images
1. An integrated circuit comprising:
- a passive device; and
a ground shield capacitor arranged under the passive device, wherein the ground shield capacitor comprises;
a first metal layer coupled to a supply voltage;
a second metal layer coupled to a ground potential; and
a plurality of fingers arranged radially, wherein the plurality of fingers includes (i) a plurality of fingers of a first type, (ii) a plurality of fingers of a second type, and (iii) a plurality of fingers of a third type,wherein a first finger of the third type couples the plurality of fingers of the first type to the first metal layer,wherein a second finger of the third type couples the plurality of fingers of the second type to the second metal layer,wherein each finger of the first type is respectively alternately positioned next to a corresponding finger of the second type,wherein capacitances form between (i) the plurality of fingers of the first type connected to the supply voltage via the first metal layer and (ii) the plurality of fingers of the second type connected to the ground potential via the second metal layer,wherein gaps between the capacitances create a high impedance for eddy currents,wherein the capacitances create a low impedance AC coupling from the supply voltage to the ground potential,wherein the plurality of fingers of the first type is further coupled to a third metal layer through vias that connect the first metal layer to the third metal layer,wherein the plurality of fingers of the second type is further coupled to a fourth metal layer through vias that connect the second metal layer to the fourth metal layer,wherein the plurality of fingers extend beyond a periphery of the passive device, andwherein the passive device is tuned to resonate at a predetermined frequency using the capacitances of the ground shield capacitor.
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Abstract
In one embodiment, an apparatus includes a first reference voltage coupled to a first metal layer and a second reference voltage coupled to a second metal layer. A first finger type in the plurality of fingers is coupled to the first metal layer at a first area and coupled to the first metal layer and the second metal layer at a second area. A second finger type in the plurality of fingers is coupled to the second metal layer at the first area and coupled to the first metal layer and the second metal layer at the second area. Also, the first finger type and the second finger type alternately positioned next to each other.
66 Citations
10 Claims
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1. An integrated circuit comprising:
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a passive device; and a ground shield capacitor arranged under the passive device, wherein the ground shield capacitor comprises; a first metal layer coupled to a supply voltage; a second metal layer coupled to a ground potential; and a plurality of fingers arranged radially, wherein the plurality of fingers includes (i) a plurality of fingers of a first type, (ii) a plurality of fingers of a second type, and (iii) a plurality of fingers of a third type, wherein a first finger of the third type couples the plurality of fingers of the first type to the first metal layer, wherein a second finger of the third type couples the plurality of fingers of the second type to the second metal layer, wherein each finger of the first type is respectively alternately positioned next to a corresponding finger of the second type, wherein capacitances form between (i) the plurality of fingers of the first type connected to the supply voltage via the first metal layer and (ii) the plurality of fingers of the second type connected to the ground potential via the second metal layer, wherein gaps between the capacitances create a high impedance for eddy currents, wherein the capacitances create a low impedance AC coupling from the supply voltage to the ground potential, wherein the plurality of fingers of the first type is further coupled to a third metal layer through vias that connect the first metal layer to the third metal layer, wherein the plurality of fingers of the second type is further coupled to a fourth metal layer through vias that connect the second metal layer to the fourth metal layer, wherein the plurality of fingers extend beyond a periphery of the passive device, and wherein the passive device is tuned to resonate at a predetermined frequency using the capacitances of the ground shield capacitor. - View Dependent Claims (2, 3, 4, 5)
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6. A method comprising:
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coupling a first metal layer to a supply voltage; coupling a second metal layer to a ground potential; arranging, radially, a plurality of fingers including (i) a plurality of fingers of a first type, (ii) a plurality of fingers of a second type, and (iii) a plurality of fingers of a third type by coupling the plurality of fingers of the first type to the first metal layer using a first finger of the third type, coupling the plurality of fingers of the second type to the second metal layer using a second finger of the third type, and positioning each finger of the first type respectively alternately next to a corresponding finger of the second type, wherein capacitances form between (i) the plurality of fingers of the first type connected to the supply voltage via the first metal layer and (ii) the plurality of fingers of the second type connected to the ground potential via the second metal layer, wherein gaps between the capacitances create a high impedance for eddy currents, and wherein the capacitances create a low impedance AC coupling from the supply voltage to the ground potential; coupling the plurality of fingers of the first type to a third metal layer through vias that connect the first metal layer to the third metal layer; coupling the plurality of fingers of the second type to a fourth metal layer through vias that connect the second metal layer to the fourth metal layer; arranging, under a passive device in an integrated circuit, a ground shield capacitance including the capacitances formed by (i) the plurality of fingers, and (ii) the first through fourth metal layers; extending the plurality of fingers beyond a periphery of the passive device; and tuning the passive device to resonate at a predetermined frequency using the capacitances of the ground shield capacitor. - View Dependent Claims (7, 8, 9, 10)
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Specification