Optical emission interferometry for PECVD using a gas injection hole
View Patent ↗The present invention provides a method and apparatus for improving optical sensing of a plasma process through the use of a fiber optic sensor placed within a standard showerhead hole of a standard gas showerhead positioned in an upper electrode of a plasma system during the plasma processing of a substrate. A film property can be calculated based on the measured plasma emission from the surface of the substrate. The film property can be film deposition rate, refractive index, film thickness, etc. Based on the measured film property, the plasma processing of the substrate can be adjusted and/or terminated. In addition, a window is provided that is positioned in the upper electrode assembly for viewing the plasma emission through the standard showerhead hole.
1. A plasma apparatus for processing a substrate comprising:
a vacuum chamber;
at least one power supply for generating the plasma in said vacuum chamber;
a substrate pedestal for supporting the substrate;
an upper electrode assembly having a viewport and a gas distribution system having a showerhead having a plurality of standard showerhead holes;
a detector in optical communication with optical components, said optical components being positioned within said viewport above said showerhead, said optical components only exposed to non-reacted process gas, said optical components in optical communication with at least one of said standard showerhead holes, said optical components collecting plasma emission transmitted through said standard showerhead holes, said detector monitoring the collected plasma emission transmitted through said standard showerhead holes; and
a control system in electrical communication with said detector and said power supply.
2. The apparatus according to claim 1 wherein said optical components further comprising an optical fiber.
3. The apparatus according to claim 1 wherein said window is located to transmit plasma emission reflected normally from the substrate.
4. The apparatus according to claim 1 further comprising a lens positioned in a baffle plate.
5. The apparatus according to claim 1 wherein said upper electrode is RF grounded.
6. The apparatus according to claim 1 wherein said upper electrode is RF powered.
7. The apparatus according to claim 1 wherein said substrate pedestal is RF grounded.
8. The apparatus according to claim 1 wherein said substrate pedestal is RF powered.