Breakdown of the high-voltage sheath in metal plasma immersion ion implantation

It is suggested that breakdown of a space-charge sheath obeys similar breakdown laws as known for vacuum breakdown. When metal plasmas of vacuum arcs are used, the sheath between a biased substrate and plasma is very thin and the electric-field strength is very high. Field enhancement (e.g., at sharp edges of the substrate) leads to thermal instability of electron emission centers, followed by dense plasma formation which, in turn, electrically short circuits the sheath (breakdown). Theoretical and experimental evidence for this mechanism is presented.