Tunneling 1/ fγ noise in 5 nm HfO 2/2.1 nm SiO 2 gate stack n-MOSFETs

Abstract

Evidence is provided for excess tunneling 1/ f γ noise into trap states in a 5 nm HfO 2 layer deposited on 2.1 nm thermal SiO 2. As such, it is a nice illustration of the McWhorter type of flicker noise. The interaction of the HfO 2 traps with inversion layer carriers gives rise to an excess 1/ f γ component below 100 Hz typically, corresponding to a γ > 1. In contrast, the background 1 / f γ ′ noise of the SiO 2 layer is characterized by a γ′ < 1 and dominates the high-frequency part of the spectra. The excess fluctuations cause several peaks in the noise spectral density as a function of the gate bias or drain current. The fact that more than one “resonance” peak is found suggests tunneling to or from different discrete defect states or bands of energy levels.