Comparative Study of Plasma Source-Dependent Charging Polarity in Metal–Oxide–Semiconductor Field Effect Transistors with High-k and SiO2 Gate Dielectrics

Abstract

The polarities of charging damage in n- and p-channel metal–oxide–semiconductor field effect transistors (MOSFETs) with Hf-based high-k gate stack (HfAlOx/SiO2) were studied for two different plasma sources (Ar- and Cl-based gas mixtures) and found to depend on plasma conditions, in contrast to those with conventional SiO2. It was also found that high-k devices were more susceptible to plasma charging damage than SiO2 devices. For Ar-plasma, which was confirmed to induce a larger charging damage, both n- and p-channel MOSFETs with high-k gate stacks suffer from negative charge trapping, whereas for Cl-plasma confirmed to induce less damage, both n- and p-channel MOSFETs with high-k gate stacks suffer from positive charge trapping. The above-mentioned plasma-source-dependent charging damage was also compared on the basis of the results obtained by the plasma diagnostics. From the results of constant-current stress tests, the unique charging polarity observed for the high-k gate stack was attributed to the characteristic hole and electron trapping phenomena, in accordance with the injected stress current and stress time, implying the necessity of taking the intrinsic charge trapping process into consideration for accurate evaluations of charging damage on high-k gate dielectrics.