Patent ID: 9536711
Date: 2017-01-03
CPC Classifications: H01J

Claim:
1. A method for processing a substrate in a plasma processing chamber, the method comprising: providing an upper electrode, a lower electrode, an edge ring concentrically surrounding at least a portion of said lower electrode, and a conductive coupling ring formed of a direct current (DC) conductive material and disposed in the lower electrode below said edge ring; configuring at least one radio frequency (RF) power source to ignite plasma between said upper electrode and said lower electrode to process said substrate when said substrate is disposed above said lower electrode; using said conductive coupling ring to provide a conductive path that is coupled to at least said plasma, wherein said edge ring substantially covers and protects said conductive coupling ring from said plasma; electrically coupling a DC control module via the lower electrode to the conductive coupling ring; and switching, while the plasma is ignited in the plasma processing chamber, the electrical coupling from being open to a DC ground through an RF filter and a variable resistor, said conductive coupling ring causing setting of a DC bias voltage of the substrate, the switching causing a decrease in mean ion energy of said plasma at said substrate and, while the plasma is ignited, further decreasing the mean ion energy of said plasma at said substrate by increasing said DC bias voltage by adjusting the variable resistor, wherein the conductive coupling ring disposed in the lower electrode below the edge ring enables current to traverse from the upper electrode, through the plasma when present, through the conductive coupling ring and to the DC control module that is connected to the lower electrode.