Varactor design using area to perimeter ratio for improved tuning range
First Claim
1. A parallel plate tunable varactor, the varactor comprising:
- a first electrode;
a second electrode;
a thin film dielectric layer between the first electrode and the second electrode, wherein the first electrode, the second electrode, and the dielectric layer are integrated on a substrate, and a permittivity of the dielectric layer varies according to a DC bias applied between the first electrode and the second electrode; and
an active region defined by an overlap of the first electrode, the second electrode, and the dielectric layer, the active region having a lateral shape, wherein a perimeter of the lateral shape is less than a perimeter of an equivalent square having a same area as the lateral shape, and a ratio of an area of the lateral shape to the perimeter of the lateral shape is not less than four micrometers.
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Abstract
Parallel plate tunable varactors having a bulk capacitance contribution to a total capacitance increased compared to a fringing capacitance contribution are disclosed. The contribution of the bulk capacitance to the total capacitance of an exemplary BST varactor is increased by increasing the area/perimeter ratio of the active region, thereby improving the tunability and other properties of the varactor. In an exemplary embodiment, an active region of the varactor has a lateral shape with a perimeter that is less than a perimeter of an equivalent area square. In various exemplary embodiments, the shape of the active region may be substantially circular or substantially octagonal. Methods for fabricating and designing such varactors are also disclosed.
42 Citations
15 Claims
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1. A parallel plate tunable varactor, the varactor comprising:
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a first electrode; a second electrode; a thin film dielectric layer between the first electrode and the second electrode, wherein the first electrode, the second electrode, and the dielectric layer are integrated on a substrate, and a permittivity of the dielectric layer varies according to a DC bias applied between the first electrode and the second electrode; and an active region defined by an overlap of the first electrode, the second electrode, and the dielectric layer, the active region having a lateral shape, wherein a perimeter of the lateral shape is less than a perimeter of an equivalent square having a same area as the lateral shape, and a ratio of an area of the lateral shape to the perimeter of the lateral shape is not less than four micrometers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification