Unintended gas breakdowns in narrow gaps of advanced plasma sources for semiconductor fabrication industry*

Mitigating unintended gas breakdown in narrow gaps is crucial to developing more reliable and advanced plasma sources for the semiconductor fabrication industry. We performed experimental and theoretical study of unintended breakdowns in narrow gaps in advanced plasma sources. and report a significant drop in the breakdown voltage when a background plasma is present in the surrounding volume. Much higher initial current caused by charged particles leaking from the plasma into the gap is identified as the main factor behind this effect. The current amplifies local space charge, resulting in an enhanced electric field that increases the ionization rate thus reducing the breakdown voltage. Furthermore, we observed lowering the breakdown voltage after many breakdowns most probable due to the surface erosion caused by the breakdown. The surface damaged by breakdown exhibits increases secondary emission and therefore provides positive feedback on, leading to more frequent unintended breakdowns, which becomes a critical issue for plasma processing equipment.