RF current measurement in semiconductor processing tool

A method of plasma-assisted semiconductor processing in multiple stations in a process chamber is provided. The method comprises: a) providing substrates at each of the multiple stations; b) distributing RF power to multiple stations to thereby generate a plasma in the station, wherein the RF power is distributed according to a RF power parameter that is adjusted to reduce station to station variations; c) tuning a frequency of the RF power, wherein tuning the frequency includes: i) measuring a current of the plasma; ii) determining, according to the current measured in (i), a change to the frequency of the RF power, and iii) adjusting the frequency of the RF power; and d) performing a semiconductor processing operation on the substrate at each station.