MKS Instruments, Inc.
Method for ion mass separation and ion energy control in process plasmas

Abstract:

Plasma ion energy distribution for ions having different masses is controlled by controlling the relationship between a base RF frequency and a harmonic RF frequency. By the controlling the RF power frequencies, characteristics of the plasma process may be changed based on ion mass. The ions that dominate etching may be selectively based upon whether an ion is lighter or heavier than other ions. Similarly, atomic layer etch processes may be controlled such that the process may be switched between a layer modification step and a layer etch step though adjustment of the RF frequencies. Such switching is capable of being performed within the same gas phase of the plasma process. The control of the RF power includes controlling the phase difference and/or amplitude ratios between a base RF frequency and a harmonic frequency based upon the detection of one or more electrical characteristics within the plasma apparatus.