Patent ID: 7084054

Claim:
A method for making an opening for electrical contact, the method comprising: performing a first etch through a first dielectric layer to form a first via and a second dielectric layer; filling the first via with a BARC material to form a first BARC layer; performing a second etch on the first BARC layer to form a second BARC layer, the second etch having a first etch rate in a first peripheral region of the second BARC layer and a second etch rate in a first central region of the second BARC layer, the first peripheral region located around a sidewall of the first via, the first central region located around a center of the first via, the first etch rate being larger than the second etch rate, the first peripheral region located lower than the first central region, a first top surface of the second BARC layer having substantially a first convex shape, wherein the second etch includes a dry etch, the dry etch using a plurality of ions, the plurality of ions having a plurality of velocities respectively, the plurality of velocities having a plurality of angles with respect to a direction vertical to a top surface of the dielectric layer respectively, an average magnitude of the plurality of angles being smaller than 10 degrees; performing a third etch through a second dielectric layer to form a trench and a third BARC layer, the trench having a trench bottom surface, the trench bottom surface being substantially free from any spike around a side surface of the third BARC layer, a second top surface of the third BARC layer having substantially a second convex shape; and removing the third BARC layer to form a second via, and wherein the second etch uses a plasma having an electron temperature, the electron temperature being higher than 4 eV and lower than 10 eV, and wherein the plasma has a gas pressure, the gas pressure being lower than 40 mTorr.