Patent ID: 8313611

Claim:
A gas switching section for a gas distribution system for supplying process gas to a plasma processing chamber, the gas switching section including: a first gas passage adapted to be in fluid communication with a first gas line and the plasma processing chamber; a second gas passage adapted to be in fluid communication with the first gas line and a by-pass line; a first fast switching valve along the first gas passage operable to open and close the first gas passage, the first fast switching valve having a first flow coefficient; and a second fast switching valve along the second gas passage operable to open and close the second gas passage, the second fast switching valve having a second flow coefficient different than the first flow coefficient such that an inlet pressure of the first fast switching valve is substantially equal to an inlet pressure of the second fast switching valve when gas flow is switched from the first gas passage to the second gas passage by closing the first fast switching valve and opening the second fast switching valve, or from the second gas passage to the first gas passage by closing the second fast switching valve and opening the first fast switching valve; wherein the first and second fast switching valves are adapted to be actuated (a) to open the first fast switching valve and close the second fast switching valve to supply a process gas to the plasma processing chamber, and (b) close the first fast switching valve and open the second fast switching valve to divert the process gas to the by-pass line.