Electric breakdown inside a gas hole in contact with plasma

In semiconductor manufacturing processes, electric breakdown within narrow gaps such as gas holes must be mitigated because it reduces the power efficiency of process plasma and introduces contaminants that destabilize plasma control. We investigated the breakdown phenomena inside a gas hole under conditions replicating a semiconductor process chamber, specifically with one end of the hole in direct contact with the background process plasma. Our experimental results reveal that biasing the electrode above the plasma potential—so the plasma acts as the cathode—triggers breakdown at voltages far below those previously reported. We find that gas hole breakdown in this configuration is better explained by anode spot plasma formation rather than the conventional Townsend breakdown mechanism. In this paper, we present the mechanism of breakdown inside a gas hole in contact with plasma based on experimental results.