Top hat structure for isolation capacitors
An isolation capacitor structure reduces the likelihood of breakdown in the passivation layers by physically re-shaping or dividing the top plate of the isolation capacitor into two segments. In that way, the electric field is driven down and away from the passivation surfaces. One embodiment utilizes a series capacitor formed by the top metal plate of the capacitor and an additional “top hat” plate above the top metal plate that redirects the fields into the main isolation capacitor. Vias may be included between the top hat plate and the top metal plate. Another approach reshapes the top plate to have an integrated top hat structure and achieves similar results of directing charge down and away from the passivation layer surface breakdown paths.
1. An integrated circuit with an isolation capacitor comprising:
a first conductive plate above a substrate;
a second conductive plate above the first conductive plate;
a first dielectric region between the first conductive plate and the second conductive plate;
a third conductive plate above the second conductive plate, the first conductive plate, the second conductive plate, and the third conductive plate being conductive plates of the isolation capacitor on the integrated circuit with no conductive metal path formed between the first conductive plate and the second conductive plate, the third conductive plate having a first perimeter being recessed from a second perimeter of the second conductive plate, a first thickness of the second conductive plate differing from a second thickness of the third conductive plate;
a second dielectric region between the second conductive plate and the third conductive plate, the third conductive plate being separated from the second conductive plate by a thickness of the second dielectric region, and a thickness of the first dielectric region differing from a thickness of the second dielectric region, the third conductive plate being off center from the second conductive plate in a first lateral direction, the first conductive plate being off center from the second conductive plate in a second lateral direction opposite the first lateral direction, and the first conductive plate being at least partially outside a perimeter of the third conductive plate; and
a plurality of conductive vias formed in the second dielectric region to electrically couple the second conductive plate and the third conductive plate.
2. The integrated circuit as recited in claim 1 wherein the thickness of the first dielectric region ranges between 5 microns and 25 microns.
3. The integrated circuit as recited in claim 1 further comprising a bond wire electrically coupled to the third conductive plate.
4. The integrated circuit as recited in claim 1 wherein the thickness of the second dielectric region between the second conductive plate and the third conductive plate ranges between approximately 0.5 microns and 2.0 microns.
5. The integrated circuit as recited in claim 1 wherein the second dielectric region is formed of SiO2, SiN, silicon rich oxide, or SiON.
6. The integrated circuit as recited in claim 1 wherein the third conductive plate is smaller than the second conductive plate.
7. The integrated circuit as recited in claim 1 wherein the first conductive plate is outside the perimeter of the third conductive plate.
8. The integrated circuit as recited in claim 1 wherein the first dielectric region is formed of a first dielectric material and the second dielectric region is formed of a second dielectric material different than the first dielectric material.
9. A method of making an isolation capacitor comprising:
forming a first conductive plate of an isolation capacitor above a substrate;
forming a first dielectric region above the first conductive plate;
forming a second conductive plate of the isolation capacitor above the first dielectric region with no conductive metal path formed between the first and second conductive plates of the isolation capacitor;
forming a second dielectric region above the second conductive plate; and
forming a third conductive plate of the isolation capacitor above the second dielectric region, a first thickness of the second conductive plate differing from a second thickness of the third conductive plate, and a thickness of the first dielectric region differing from a thickness of the second dielectric region;
forming the third conductive plate such that a first perimeter of the third conductive plate is recessed from a second perimeter of the second conductive plate, the third conductive plate being off center from the second conductive plate in a first lateral direction, the first conductive plate being off center of the second conductive plate in a second lateral direction opposite the first lateral direction, and the first conductive plate being at least partially outside a perimeter of the third conductive plate; and
forming conductive vias in the second dielectric region connecting the second conductive plate and the third conductive plate.
10. The method as recited in claim 9 further comprising forming the first dielectric region with the thickness of between 5 microns and 25 microns.
11. The method as recited in claim 9 further comprising electrically coupling a bond wire to the third conductive plate.
12. The method as recited in claim 9 further comprising forming the second dielectric region between the second conductive plate and the third conductive plate with the thickness of between approximately 0.5 microns and 2.0 microns.
13. The method as recited in claim 9 further comprising forming the second dielectric region of SiO2, SiN, silicon rich oxide, or SiON.
14. An isolation capacitor formed by the method of claim 9 .
15. An isolation capacitor comprising:
a first conductive plate above a substrate, a second conductive plate above the first conductive plate, and a third conductive plate above the second conductive plate, the third conductive plate having a first perimeter being recessed from a second perimeter of the second conductive plate, a first thickness of the second conductive plate differing from a second thickness of the third conductive plate, the third conductive plate being off center from the second conductive plate in a first lateral direction, the first conductive plate being off center from the second conductive plate in a second lateral direction opposite the first lateral direction, and the first conductive plate being at least partially outside the first perimeter of the third conductive plate;
a first dielectric region between the first conductive plate and the second conductive plate with no conductive metal path formed between the first conductive plate and the second conductive plate, and a second dielectric region between the second conductive plate and the third conductive plate, the third conductive plate being separated from the second conductive plate by a thickness of the second dielectric region, a top surface of the third conductive plate exposed by an opening in one or more passivation layers positioned above the second dielectric region, and a thickness of the first dielectric region differing from a thickness of the second dielectric region; and
a plurality of conductive vias formed in the second dielectric region to electrically couple the second conductive plate and the third conductive plate.
16. The isolation capacitor as recited in claim 15 wherein the first dielectric region is formed of a first dielectric material and the second dielectric region is formed of a second dielectric material different than the first dielectric material.