Gas switching section including valves having different flow coefficient's for gas distribution system

A method of processing a semiconductor substrate in a plasma processing apparatus, a gas switching section for a gas distribution system for supplying gas to a plasma processing chamber including a gas distribution member having center and edge zones which are flow insulated from each other, the gas switching section comprising:

• a first gas passage adapted to be in fluid communication with a first gas line and the edge zone of the gas distribution member of 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 third gas passage adapted to be in fluid communication with a second gas line and the center zone of the gas distribution member;
• a fourth gas passage adapted to be in fluid communication with the second gas line and the by-pass line;
• a fifth gas passage adapted to be in fluid communication with a third gas line and the center zone;
• a sixth gas passage adapted to be in fluid communication with the third gas line and the by-pass line;
• a seventh gas passage adapted to be in fluid communication with a fourth gas line and the edge zone;
• an eighth gas passage adapted to be in fluid communication with the fourth gas line and the by-pass line;
• first and second fast switching valves along the first and second gas passages respectively, the first fast switching valve operable to open and close the first gas passage and having a first flow coefficient, the second fast switching valve operable to open and close the second gas passage and 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;
• third and fourth fast switching valves along the third and fourth gas passages, respectively, the third fast switching valve operable to open and close the third gas passage and having a third flow coefficient, the fourth fast switching valve operable to open and close the fourth gas passage and having a fourth flow coefficient different than the third flow coefficient such that an inlet pressure of the third fast switching valve is substantially equal to an inlet pressure of the fourth fast switching valve when gas flow is switched from the third gas passage to the fourth gas passage by closing the third fast switching valve and opening the fourth fast switching valve, or from the fourth gas passage to the third gas passage by closing the fourth fast switching valve and opening the third fast switching valve;
• fifth and sixth fast switching valves along the fifth and sixth gas passages, respectively, the fifth fast switching valve operable to open and close the fifth gas passage and having a fifth flow coefficient, the sixth fast switching valve operable to open and close the sixth gas passage and having a sixth flow coefficient different than the fifth flow coefficient such that an inlet pressure of the fifth fast switching valve is substantially equal to an inlet pressure of the sixth fast switching valve when gas flow is switched from the fifth gas passage to the sixth gas passage by closing the fifth fast switching valve and opening the sixth fast switching valve, or from the sixth gas passage to the fifth gas passage by closing the sixth fast switching valve and opening the fifth fast switching valve;
• and
• seventh and eighth fast switching valve along the seventh and eighth gas passages respectively, the seventh fast switching valve operable to open and close the seventh gas passage and having a seventh flow coefficient, the eighth fast switching valve operable to open and close the eighth gas passage and having an eighth flow coefficient different than the seventh flow coefficient such that an inlet pressure of the eighth fast switching valve is substantially equal to an inlet pressure of the seventh fast switching valve when gas flow is switched from the seventh gas passage to the eighth gas passage by closing the seventh fast switching valve and opening the eighth fast switching valve, or from the eighth gas passage to the seventh gas passage by closing the eighth fast switching valve and opening the seventh fast switching valve;
• the first, third, sixth and eighth fast switching valves are adapted to be actuated to open and the second, fourth, fifth and seventh fast switching valves are adapted to be actuated to close so as to supply a first process gas to the center and edge zones and divert a second process gas to the by-pass line;
• and
• the second, fourth, fifth and seventh fast switching valves are adapted to be actuated to open and the first, third, sixth and eighth fast switching valves are adapted to be actuated to close so as to supply the second process gas to the center and edge zones and divert the first process gas to the by-pass line including a showerhead electrode assembly having center and edge zones which are flow insulated from each other, comprising:
• a) supplying the first process gas to the center and edge zones of the showerhead electrode assembly while diverting the second process gas to the by-pass-line, the plasma processing chamber containing a semiconductor substrate including at least one layer and a patterned resist mask overlying the layer;
• b) producing a first plasma from the first process gas and (i) etching at least one feature in the layer or (ii) forming a polymer deposit on the mask;
• c) switching the flows of the first and second process gases so that the second process gas is supplied to the center and edge zones of the showerhead electrode assembly while the first process gas is diverted to the by-pass line;
• d) producing a second plasma from the second process gas and (iii) etching the at least one feature in the layer or (iv) forming a polymer deposit on the layer and the mask;
• e) switching the flows of the first and second process gases so that the first process gas is supplied into the plasma processing chamber while the second process gas is diverted to the by-pass line;
• and
• f) repeating a)-e) a plurality of times with the substrate.