Methods and apparatus for preventing plasma un-confinement events in a plasma processing chamber

A plasma processing system having a plasma processing chamber configured for processing substrates, the plasma processing system comprising:

• a ground bucket, said ground bucket having a sharp component structure disposed along a RF current path during said processing;
• a first dielectric shielding structure configured to shield at least a portion of said sharp component structure from surrounding gas spaces in said plasma processing chamber during said processing, said first dielectric shielding structure including a lip feature that extends vertically and drapes over said sharp component structure;
• a second dielectric shielding structure disposed perpendicular to said first dielectric shielding structure, said second dielectric structure covering a vertical side of said ground bucket, at least a portion of said second dielectric shielding structure overlapping said lip feature;
• an upper chamber structure;
• a middle mounting plate having a first surface and a second surface opposite said first surface, said first surface mated with a bottom surface of said upper chamber structure such that there exists a first gap between said mounting plate and said bottom surface of said upper chamber structure, said first gap being disposed along a RF current path during said processing, said mounting plate further having a recess in a first side, thereby forming a shoulder below said first surface, said shoulder and said bottom surface of said upper chamber structure forming a capturing structure;
• an outer electrode disposed below said middle mounting plate, said outer electrode mated with said second surface of said mounting plate;
• a third dielectric shielding structure, wherein said third dielectric shielding structure is a single continuous dielectric sleeve having an outer surface, an inner surface, and a shelf feature, said shelf protrusion being captured in said capturing structure formed by said shoulder and said bottom surface of said upper chamber structure, said shelf protrusion being disposed under said bottom surface of said upper chamber structure, said shelf protrusion being disposed on said inner surface between an upper end of said third dielectric shielding structure and a lower end of said third dielectric shielding structure such that an upward projecting portion of said third dielectric shielding structure above said shelf protrusion surrounds at least a first portion of said upper chamber structure, and such that a downward projecting portion of said third dielectric shielding structure below said shelf protrusion covers both at least a first portion of said middle mounting plate and a first portion of said outer electrode, said outer surface of said third dielectric shielding structure being continuous across at least a second portion of said upper chamber structure, said middle mounting plate, and at least a second portion of said outer electrode so as to reduce contamination, wherein at least one of said shelf and said upward projecting portion of said dielectric sleeve covers said first gap.