Methods and apparatuses for effectively reducing gas residence time in a plasma processing chamber

A method for processing a substrate in a plasma system having at least one plasma processing chamber, said chamber including at least a lower electrode for supporting said substrate, a chamber ceiling disposed above said lower electrode such that a plasma processing region exists between an upper surface of said substrate and said chamber ceiling during said processing, and a plasma generation power source for providing energy to generate a plasma in said plasma processing region from supplied reactant gas, said method comprising;

• providing a light emitting apparatus for emitting first light into said plasma processing region;
• providing a light receiving apparatus for receiving second light, said second light representing an altered version of said first light after said first light passes through said plasma processing region;
• logic for analyzing said second light to ascertain whether a parameter of said second light exceeds a first threshold or fall below a second threshold;
• if said parameter of said second light equals or exceeds said first threshold, reducing an amount of plasma generation energy provided by said plasma generation power source;
• and
• if said parameter of said second light equals or falls below said second threshold, increasing said amount of plasma generation energy provided by said plasma generation power source.

A plasma processing system having at least one plasma processing chamber for processing a substrate, comprising:

• a lower electrode for supporting said substrate;
• a plasma generation power source for providing energy to generate a plasma from supplied reactant gas, said plasma is generated in a plasma processing region above said substrate;
• means for emitting first light into said plasma processing region;
• means for receiving second light, said second light representing an altered version of said first light after said first light passes through said plasma processing region;
• and
• means for analyzing said second light to ascertain whether a parameter of said second light equals or exceeds a first threshold or equals or falls below a second threshold, wherein said means for analyzing sends a first signal to reduce an amount of plasma generation energy provided by said plasma generation power source if said parameter of said second light equals or exceeds said first threshold, reducing, said means for analyzing sends a second signal for increasing said amount of plasma generation energy provided by said plasma generation power source if said parameter of said second light equals or falls below said second threshold.