Rf metrology system for a substrate processing apparatus incorporating rf sensors with corresponding lock-in amplifiers

Abstract

A RF control circuit is provided and includes a controller, a divider, and a RF sensor. The controller selects a RF, which is a frequency of a reference LO signal. The divider receives a first RF signal detected in a substrate processing chamber and outputs a second RF signal. The first RF signal is generated by a RF generator and supplied to the substrate processing chamber. The RF sensor includes a lock-in amplifier, which includes: a RF path that receives the second RF signal; a LO path that receives the reference LO signal; a first mixer that generates an IF signal based on the second RF signal and the reference LO signal; and a filter that filters the IF signal. The controller generates a control signal based on the filtered IF signal and transmits the control signal to the RF generator to adjust the first RF signal.