Random telegraph noise as a new measure of plasma-induced charging damage in MOSFETs

Abstract

Random telegraph noise (RTN) has been recently of great importance in designing ultimately scaled MOSFETs. We address in this paper how RTN characteristics are altered by plasma process-induced charging damage (PCD). MOSFETs with SiO₂ and high-k gate dielectric were prepared and exposed to an inductively coupled plasma (ICP) with Ar gas. From the time evolution of I_ds fluctuation defined as I_ds/μ_Ids, where μ_Ids is the mean I_ds, we comprehensively investigated the details of RTN features such as the statistical distribution of I_ds/μ_Ids, power spectral density, and the time constants for carrier capture and emission. It was found that the statistical distribution width of I_ds/μ_Ids, δ(I_ds/μ_Ids), increased by PCD for both MOSFETs with the SiO₂ and high-k gate dielectrics, suggesting that RTN characteristics can be used as a potential measure of PCD. These features were consistent with Δ V_th results. However, the slope in power spectral density and the time constants exhibited complicated behaviors owing to the nature of created traps by PCD. It is confirmed that PCD alters RTN characteristics, and that, in evaluating the amount of PCD, δ(I_ds/μ_Ids) should be used as a straightforward measure.