This paper demonstrates the use of conductivity sensors to monitor and control the concentration of RCA cleaning and hydrofluoric acid (HF) etching Solutions. Commercially available electrodeless con- Ductivity sensors were used to monitor and control the Concentration of these process solutions. A linear rela- Tionship between the conductivity of the solution and The chemical concentration was obtained within the Range studied. A chemical injection scheme was devel- Oped to maintain the chemical concentration within Specified limits.
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