Patent ID: 8673111
Filing Date: 2014-03-18
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 configured to mount the wafer in the process chamber with the central device area within a device border centered on a wafer axis and with a wafer edge exclusion area extending radially away from both the axis and the border; a second electrode configured with a field ring mount section extending radially relative to the border and away from the axis and being adjacent to the border; a field ring arrangement configured to establish a field capable of exerting force on the charged particles to repel the particles from moving to the central device area, the field ring arrangement being mounted in the field ring mount section and being configured so that the field has a field strength gradient configured with a peak value adjacent to the border, the field strength gradient defining increasing field strength inversely proportional to increased radial distance away from the axis and away from the border, the gradient and the peak value of the field strength repelling the charged particles from moving radially past the border toward the axis; and a first electrically grounded ring extending in an annular path radially outward of the edge exclusion area and of the field ring mount section and electrically isolated from the second electrode, wherein the first electrode is further configured with a second electrically grounded ring extending in an annular path radially outward of the edge exclusion area and electrically isolated from the mounted wafer, and the field ring arrangement is further configured with a DC bias ring mounted in the field ring mount section so that the grounded rings and the DC bias rings cooperate to establish the field as an electric field with the configured field strength gradient.