Breakdown Mechanism of Capacitively Coupled RF Discharges

Measured breakdown characteristics of capacitively coupled RF discharges are compared with numerical simulations performed under different boundary conditions at the electrode. When a pair of glass-covered aluminum disks are used in the breakdown measurement of N2 and Ar gases at the RF frequency 13.56 MHz, the peculiar bend in the left branch of the minimum of V-shaped breakdown curves is not observed, suggesting the absence of secondary electron emission. For the treated boundary condition of the electron density n, the simulation with its zero gradient gives satisfactory agreement with the experimental V-shaped curves, while the simulation with n=0 is shown to be effective in the region of small electric fields. The development of RF breakdown is explained based on the simulation for spatiotemporal profiles of n.