Comparative Study of Plasma-Charging Damage in High-$k$ Dielectric and p--n Junction and Their Effects on Off-State Leakage Current of Metal--Oxide--Semiconductor Field-Effect Transistors

Plasma-induced charging damage (PCD) to a metal–oxide–semiconductor field-effect transistor (MOSFET) with a high-k dielectric was studied in detail using a capacitively coupled plasma reactor for various exposure times. From the drain current versus gate voltage characteristics, we observed the threshold voltage shift (ΔVth) and the increase in reverse-leakage current (Ij) at the n+/p junction in plasma-exposed n-channel MOSFETs. The observed ΔVth in the negative direction was due to positive trap-site creation in the high-k dielectric. The combined effect by PCD increased off-state leakage current (Ioff) in n-channel MOSFETs, however, the Ij increase was found to be dominant in the Ioff increase. By employing a capacitance-measurement technique, we clarified that the Ij considerably was increased at the junction by PCD, whereas the maximum capacitance at the junction in accumulation decreased. We also identified that the generated defect site density (nd) at the junction induces the observed Ij increase as a trap-assist tunneling site.

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