Effects of plasma-induced charging damage on random telegraph noise in metal-oxide-semiconductor field-effect transistors with SiO2 and high-k gate dielectrics

We clarified in this study how plasma-induced charging damage (PCD) affects the so-called "random telegraph noise (RTN)"-a principal concern in designing ultimately scaled large-scale integrated circuits (LSIs). Metal-oxide-semiconductor field-effect transistors (MOSFETs) with SiO2 and high-k gate dielectric were exposed to an inductively coupled plasma (ICP) with Ar gas. Drain current vs gate voltage (I-ds-V-g) characteristics were obtained before and after the ICP plasma exposure for the same device. Then, the time evolution of I-ds fluctuation defined as I-ds/mu(Ids) was measured, where mu Ids is the mean Ids. This value corresponds to an RTN feature, and RTN was obtained under various gate voltages (V-g) by a customized measurement technique. We focused on the statistical distribution width of (I-ds/mu(Ids)), d(I-ds/mu(Ids)), in order to clarify the effects of PCD on RTN. d(I-ds/mu(Ids)) was increased by PCD for both MOSFETs with the SiO2 and high-k gate dielectrics, suggesting that RTN can be used as a measure of PCD, i.e., a distribution width increase directly indicates the presence of PCD. The dependence of delta(I-ds/mu(Ids)) on the overdrive voltage V-g-V-th, where Vth is the threshold voltage, was investigated by the present technique. It was confirmed that delta(I-ds/mu(Ids)) increased with a decrease in the overdrive voltage for MOSFETs with the SiO2 and high-k gate dielectrics. The presence of created carrier trap sites with PCD was characterized by the time constants for carrier capture and emission. The threshold voltage shift (Delta V-th) induced by PCD was also evaluated and compared with the RTN change, to correlate the RTN increase with Delta V-th induced by PCD. Although the estimated time constants exhibited complex behaviors due to the nature of trap sites created by PCD, delta(I-ds/mu(Ids)) showed a straightforward tendency in accordance with the amount of PCD. These findings provide an in-depth understanding of plasma-induced RTN characteristic changes in future MOSFETs. (C) 2014 The Japan Society of Applied Physics