Patent ID: 8268116
Filing Date: 2012-09-18
Classification: H01J,H01L

Abstract:
1. Apparatus for protecting a central device area of a wafer from charged particles in a process chamber, the apparatus comprising: a first electrode having a mounting surface for receiving the wafer in the process chamber, the first electrode having a first radius for the mounting surface and a second radius for a step down surface, the second radius being greater than the first radius and the step down surface being spaced apart from the mounting surface, wherein the first electrode, including the step down surface, is defined from a conductive material; a second electrode disposed over the first electrode, the second electrode having a second electrode radius that is larger than the second radius of the first electrode, the second electrode including a field ring mount section disposed between the second electrode radius and the second radius of the first electrode, such that an inner radius of the field ring mount section locates away from the second radius of the first electrode; and a field ring arrangement disposed in the field ring mount section of the second electrode, the field ring arrangement having a magnetic polarity that is configured to establish a field capable of exerting force on the charged particles to repel the particles from moving toward the mounting surface of the first electrode; wherein the first electrode, second electrodes and the field ring arrangement are located within the process chamber.