Patent ID: 9299541
Filing Date: 2016-03-29
CPC Classification: H01J

Claim Text:
1. A plasma processing system having at least one plasma processing chamber for processing a substrate, comprising: 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; a plasma generation power source for providing energy to generate a plasma in said plasma processing region from supplied reactant gas; a light emitting apparatus for emitting a first light into said plasma processing region; a light receiving apparatus for receiving a second light, said second light representing an altered version of said first light after said first light passes through said plasma processing region; and a controller configured to analyze said second light to ascertain whether a parameter of said second light equals or exceeds a first threshold indicative of a first concentration of by-product gases resulting from a reaction of the plasma with an exposed surface of the substrate or equals or falls below a second threshold indicative of a second concentration of the by-product gases, wherein said controller controls an effective gas residence time of by-product gases on the upper surface of the substrate by adjusting the plasma generation energy level between a full mode of plasma generation and a reduced mode of plasma generation by sending a first signal for reducing an amount of plasma generation energy to a plasma generation energy level associated with the reduced mode of plasma generation provided by said plasma generation power source if said parameter of said second light equals or exceeds said first threshold, said controller sends a second signal for increasing said amount of plasma generation energy provided by said plasma generation power source to a plasma generation energy level associated with the full mode of plasma generation if said parameter of said second light equals or falls below said second threshold, wherein the plasma generation energy level associated with the reduced mode of plasma generation is sufficiently low as to minimize or stop the reaction of the plasma with exposed surfaces of the substrate such that the concentration of by-product gases reduces over time in the reduced mode of plasma generation, and wherein the plasma generation energy level associated with the full mode of plasma generation is sufficiently high as to increase the reaction of the plasma with exposed surfaces of the substrate to a full level in which the concentration of by-product gases increases over time in the full mode of plasma generation.