Patent ID: 8480913

Claim:
A method of forming a rounded corner of a trench of a workpiece in a vacuum plasma chamber, comprising: converting a gas species that is supplied to the chamber into an etchant plasma that is continuously applied to the workpiece while the rounded corner is being formed; gradually changing a first power applied to the etchant plasma through a plasma excitation unit and a second power applied to a conductive layer supporting the workpiece while the rounded corner is being formed, the gradual change being such that each of the first and second powers does not remain constant for durations in excess of one second while the rounded corner is being formed, wherein the first and second powers are gradually changed in a decreasing manner so that the formed rounded corner connects a wall of the trench to a substantially flat base of the trench; and while the rounded corner is being formed, maintaining constant: (a) the flow rate of the gas species into the chamber and (b) the species flowing into the chamber.