Parasitic plasma in He feedthrough
MaterialOxide Processes VIA etch
Supplier AMAT Chamber Principle MERIE
Topic FDC Chamber Hardware MxP+
Reference A.Steinbach, Infineon Technologies Dresden, et al.: 'Application of the Plasma Monitoring System Hercules for real time Plasma Etch Control', SEMATECH AEC/APC Symposium XI, Vail, USA, 1999.  
   
Problem Very instable process on product wafer despite the etch rate on blanket oxide wafers is in spec.
Effect He-gas pollution decreased the electric break through voltage of the He feedthrough. This results in electrical breakthrough and a parasitic plasma.

Effect on wafer / process:
Particle number out of spec.

Hardware related effect:
Destruction of chamber parts, especially He feedthrough.

Effect on plasma parameters:
Heavy peaks in the electron collision rate.
Measure Exchange of defective gas lines and burned He feedthrough.
Benefit Early fault detection (FDC) prevents further destruction of chamber parts and ensures a stable process.