Plasma etch chamber and method of plasma etching

A plasma PVD treatment chamber comprising:

• a vacuum recipient (1), said vacuum recipient (1) comprising therein:
• a treatment compartment (3) with a central axis (B), said treatment compartment (3) comprising a surrounding wall (5) enclosing an inner space (IE) of said treatment compartment (3) and said treatment compartment (3) comprising plasma treatment equipment (6) of the plasma treatment chamber;
• a pumping compartment (13) with a metal surrounding wall (15), wherein a feed through opening (21) is formed in said metal surrounding wall (15);
• a metal partition wall (23) traverse to said central axis (B) and separating said treatment compartment (3) from said pumping compartment (13);
• at least one pumping slit (35) in or along said metal partition wall (23) disposed around said central axis (B) and defining a pumping flow communication between said inner space (IE) of said treatment compartment (3) and an inner space (IP) of said pumping compartment (13);
• a pumping port (17) in said metal surrounding wall (15) of said pumping compartment (13);
• a workpiece support (39) centered about said central axis (B), adapted to support a workpiece exposed to said inner space (IE) of said treatment compartment (3), said workpiece support (39) being mounted in said vacuum recipient (1) in an electrically isolated manner (42), said workpiece support (39) being drivingly movable (F) up to a treatment position and down away from said treatment position along said central axis (B);
• a metal tubular arrangement (19) through said feed through opening (21), said metal tubular arrangement (19) extending towards said workpiece support (39) and comprising a first part (19a) mechanically coupled to said workpiece support (39) and a second part (19b) mechanically coupled to said metal surrounding wall (15) of said pumping compartment (13), said first part (19a) and said second part (19b) being movable (F) relative to one another in a direction parallel to said central axis (B), an electrically conductive joint (22) connecting said second part (19b) along an edge of said feed through opening (21) to said metal surrounding wall (15);
• an Rf feed line (41) extending through and along said metal tubular arrangement (19) and connected to said workpiece support (39);
• a system ground connector (45) for said plasma treatment chamber (1) disposed at an end of said second part (19b) of said metal tubular arrangement (19) outside said metal surrounding wall (15) of said pumping compartment (13), or disposed at said metal surrounding wall (15) opposite said metal partition wall (23);
• a multitude of distributed metal connectors (49) establishing electric and mechanical contact from said metal surrounding wall (15) of said pumping compartment (13), across said at least one pumping slit (35), via said metal partition wall (23) to said first part (19a) of said metal tubular arrangement (19) at least when said workpiece support (39) is in said treatment position;
• and
• a metal screen (80) in said treatment compartment (3) looping around said central axis (B) and masking at least a predominant surface area of an inner surface of said surrounding wall (5) of said treatment compartment (3), said screen (80) comprising a bottom rim and a top rim, said bottom rim being releasably electrically connected to said system ground connector (G) via a multitude of metal screen-connectors (85), said metal screen (80) being a maintenance exchange part,
• wherein said first part (19a) of said metal tubular arrangement (19) is in electric contact with said second part (19b) and when said workpiece support (39) is in said etching position said first part (19a) is directly electrically connected to said system ground connector (45) of the plasma PVD treatment chamber, such that two parallel RF current return paths from said metal screen (80) to said system ground connector (45) are established simultaneously, namely:
• a first RF current return path along said metal surrounding wall (15);
• and additionally
• a second RF current return path from said metal surrounding wall (15) and across said at least one pumping slit (35).