Abstract: A ring or collar surrounding a semiconductor workpiece in a plasma chamber. According to one aspect, the ring has an elevated collar portion having an inner surface oriented at an obtuse angle to the plane of the workpiece, this angle preferably being 135°. This angular orientation causes ions bombarding the inner surface of the elevated collar to scatter in a direction more parallel to the plane of the workpiece, thereby reducing erosion of any dielectric shield at the perimeter of the workpiece, and ameliorating spatial non-uniformity in the plasma process due to any excess ion density near such perimeter. In a second aspect, the workpiece is surrounded by a dielectric shield, and the shield is covered by a non-dielectric ring which protects the dielectric shield from reaction with, or erosion by, the process gases.

Abstract: The invention is embodied in a plasma reactor for processing a semiconductor wafer, the reactor having a gas distribution plate including a front plate in the chamber and a back plate on an external side of the front plate, the gas distribution plate comprising a gas manifold adjacent the back plate, the back and front plates bonded together and forming an assembly. The assembly includes an array of holes through the front plate and communicating with the chamber, at least one gas flow-controlling orifice through the back plate and communicating between the manifold and at least one of the holes, the orifice having a diameter that determines gas flow rate to the at least one hole. In addition, an array of pucks is at least generally congruent with the array of holes and disposed within respective ones of the holes to define annular gas passages for gas flow through the front plate into the chamber, each of the annular gas passages being non-aligned with the orifice.