Metal-insulator-metal (MIM) capacitor and fabrication method for making the same
A metal-insulator-metal (MIM) capacitor includes a first metal plate; a first capacitor dielectric layer disposed on the first metal plate and a second metal plate stacked on the first capacitor dielectric layer. The first metal plate, the first capacitor dielectric layer, and the second metal plate constitute a lower capacitor. A second capacitor dielectric layer is disposed on the second metal plate. A third metal plate is stacked on the second capacitor dielectric layer. The second metal plate, the second capacitor dielectric layer, and the third metal plate constitute an upper capacitor. The first metal plate and the third metal plate are electrically connected to a first terminal of the MIM capacitor, while the second metal plate is electrically connected to a second terminal of the MIM capacitor.
1. A method for fabricating a metal-insulator-metal (MIM) capacitor, comprising the steps of:
providing a substrate;
forming, in the order of, a first metal layer, a first dielectric layer, a second metal layer, a second dielectric layer, a third metal layer, and a cap layer over the substrate;
etching the cap layer, the third metal layer, the second dielectric layer, the second metal layer, and the first dielectric layer to form an upper capacitor structure consisting of a second metal plate, a second capacitor dielectric layer, and third metal plate;
partially covering the upper capacitor structure with a photo mask that defines a first metal plate to formed in the underlying first metal layer;
simultaneously etching the first metal layer, a portion of the cap layer atop the second metal plate and the second metal plate of the upper capacitor structure that are not covered by the photo mask; and
stripping the photo mask.
2. The method according to claim 1 wherein the second metal plate has a thickness that is thinner than that of the first metal plate.
3. The method according to claim 2 wherein the second metal plate has a thickness of about 1000 angstroms, and the first metal plate has a thickness of about 5000 angstroms.
4. The method according to claim 1 wherein the first and second capacitor dielectric layer are both made of PECVD dielectric.