Interdigitated capacitors
View Patent ↗The specification describes matched capacitor pairs that employ interconnect metal in an interdigitated form, and are made with an area efficient configuration. In addition, structural variations between capacitors in the capacitor pair are minimized to provide optimum matching. According to the invention, the capacitor pairs are interdigitated in a manner that ensures that the plates of each pair occupy common area on the substrate. Structural anomalies due to process conditions are compensated in that a given anomaly affects both capacitors in the same way. Two of the capacitor plates, one in each pair, are formed of comb structures, with the fingers of the combs interdigitated. The other plates are formed using one or more plates interleaved between the interdigitated plates.
1. A capacitor pair device including a first capacitor and a second capacitor, comprising:
a. a substrate,
b. a first conductive comb structure on the substrate forming another plate of the first capacitor of the capacitor pair,
c. a second conductive comb structure on the substrate forming a plate of the second capacitor of the capacitor pair, the second conductive comb structure interdigitated with the first conductive comb structure, and
d. a continuous conductive runner on the substrate interleaved between the first conductive comb structure and the second conductive comb structure, the continuous conductive runner forming the first capacitor with the first conductive comb structure and the second capacitor with the second conductive comb structure, thus forming the capacitor pair.
2. The device of claim 1 wherein the capacitor pair is a first level capacitor pair, and the device includes an insulating layer on the capacitor pair, and further includes a second level capacitor pair formed on the insulating layer.
3. The device of claim 2 wherein the first level capacitor pair is interconnected with the second level capacitor pair.
4. The device of claim 1 wherein the capacitor pair device comprises an integrated circuit.
5. A capacitor pair device including a first capacitor and a second capacitor comprising:
a. a substrate,
b. a first conductive comb structure on the substrate forming a plate of the first capacitor of the capacitor pair,
c. a second conductive comb structure on the substrate forming another plate of the second capacitor of the capacitor pair, the second conductive comb structure interdigitated with the first conductive comb structure,
d. a first continuous conductive runner on the substrate interleaved between the first conductive comb structure and the second conductive comb structure, the first continuous conductive runner forming the first capacitor with the first comb structure,
e. a second continuous conductive runner on the substrate parallel to the first continuous conductive runner, and interleaved between the first continuous conductive runner and the second conductive comb structure, the second continuous conductive runner forming the second capacitor with the second conductive comb structure, thus forming the capacitor pair.
6. The device of claim 5 wherein the capacitor pair is a first level capacitor pair, and the device includes an insulating layer on the capacitor pair, and further includes a second level capacitor pair formed on the insulating layer.
7. The device of claim 6 further including a ground plane on the substrate between the first continuous runner and the second continuous runner.
8. The device of claim 7 wherein the capacitor pair is a first level capacitor pair, and the device includes an insulating layer on the capacitor pair, and further includes a second level capacitor pair formed on the insulating layer.
9. The device of claim 8 wherein the first level capacitor pair is interconnected with the second level capacitor pair.
10. The device of claim 7 wherein the first continuous conductive runner, the second continuous conductive runner and the ground plane, each follow a parallel meandering path.
11. The device of claim 10 wherein the meandering path turns at least 180°.
12. The device of claim 11 wherein the meandering path includes at least two 90° turns.
13. The device of claim 7 wherein the fingers of the first and second conductive comb structures, the first and second continuous runners, and the ground plane, all have essentially the same thickness.
14. The device of claim 13 wherein the fingers of the first and second conductive comb structures, the first and second continuous runners, and the ground plane, all have essentially the same width.