Particle-in-cell modeling and experimental diagnosis of dual-frequency capacitively-coupled oxygen discharge

Low-pressure capacitively coupled plasmas (CCP) have been used extensively in the semiconductor industry for various processing applications. The ability of CCP in generating highly energetic ions with moderate dissociation and ionization makes it a key technology for the etching of dielectric materials. As the feature sizes become smaller and the cost of experiments increases, it becomes crucial to characterize processing characteristics using numerical modeling. This work focuses on ion energy distribution functions (IEDF) in a dual-frequency O₂ CCP. The influence of processing conditions on IEDF is examined using both particle-in-cell (PIC) modeling and IEDF measurement using a retarding field ion energy analyzer.  PIC modeling is also used to understand the critical underlying physical processes that influence the IEDF. The 1D PIC simulations and the corresponding experimental measurements were done at different pressures, RF voltages, and the frequency of the low-frequency source. The elastic and charge exchange ion-neutral reactions are found vital to capture the low energy ion population in the IEDF at higher pressures. Improvements in the model that allowed better agreement with experiments are discussed.