Patent ID: 7428915

Claim:
A valve assembly for controlling one of gas conductance from a plasma reactor chamber to a vacuum pump or chamber pressure, said valve assembly comprising: a valve housing having first and second opposing surfaces; a high conductance valve comprising: a large area opening in said first and second opposing surfaces and extending through said valve housing, said opening defining a side wall extending between said first and second surfaces having an arcuate cross-section, a large area rotatable flap in said large area opening having a smooth continuous peripheral edge with an arcuate cross-section generally matching that of said side wall and defining a small gap between said peripheral edge and said side wall in a closed flap position; a fine control valve comprising: a small area opening in said first and second opposing surfaces and extending through said valve housing, said opening defining a side wall extending between said first and second surfaces having a smooth continuous arcuate cross-section; and a small area rotatable flap in said small area opening having a smooth continuous peripheral edge with an arcuate cross-section generally matching that of said side wall and defining a small gap between said peripheral edge and said side wall in a closed flap position; first plural axial slots in said side wall of said large area opening comprising round holes of truncated circular cross-section extending from one face of said valve housing and having a radial depth that is maximum at said one face and tapers to a minimum depth at a predetermined distance below said one face, said sidewall of said large area opening having a smooth continuous surface between said axial slots.