Etch process with rotatable shower head

The present disclosure describes an exemplary etch process in a reactor that includes a shower head and an electrostatic chuck configured to receive a radio frequency (RF) power. The shower head includes a top plate and a bottom plate with one or more gas channels that receive incoming gases. The method can include (i) rotating the top plate or the bottom plate of the shower head to a first position to allow a gas to flow through the shower head; (ii) performing a surface modification cycle that includes: applying a negative direct current (DC) bias voltage to the shower head, applying an RF power signal to the wafer chuck; and (iii) performing an etching cycle that includes: removing the negative DC bias voltage from the shower head and lowering the RF power signal applied to the wafer chuck.