Keywords: DPN, drain leakage, gate–last, gate leakage, high–k, interface state, kink effect, metal gate, field–effect transistors, decoupled plasma nitridation, annealing temperatures, nMOSFETs
Kink effect for 28 nm n–channel field–effect transistors after decoupled plasma nitridation treatment with annealing temperatures
The kink effect of drain leakage based on gated diode measurement metrology for the tested nMOSFETs with 28 nm HK/MG, gate–last and PDA or DPN nitridation processes was observed at VG around −0.6 V when the gate voltage was swept from −Vcc to 0.2 volt as VD = 0.1 V. Nevertheless, this interesting phenomenon was not evident as the gate voltage was reversely swept from 0.2 volt to -Vcc. The chief mechanism in speculation can be illustrated by the electrons coming from drain inducing capture–and–emission behaviour by the channel interface traps near the drain junction. While VG changes from −Vcc towards +0.2 V, interface states near valence band become lower than Fermi–level of silicon substrate. Electrons flow from drain to fill these interface states so that drive current (ID) increases. On the contrary, as VG changes from +0.2 V to −Vcc, the trapped electrons are recombined with holes from substrate so that ID is not affected. This kink effect for all of tested devices is not very distinct far and near. When the Poole–Frenkel (P–F) tunnelling electrons coming from gate to drain are evident in leakage, especially at the long–channel device, this effect will be probably counteracted, exhibited at the electrical characteristics of PDA group.