This paper reports the nitridation effects on 1/f noise in n-MOSFETs with MOCVD HfO 2 as gate dielectric. Nitridation of the gate oxides was carried out by using a post-deposition anneal (PDA) process in a N 2 or NH 3 ambient. Predominantly 1/f γ type noise is observed, with γ ~ 1. For non-nitrided interfaces, significant variation in noise was observed when different PDAs are employed. Among the studied PDAs, devices annealed with N 2 show the lowest input referred noise, close to ITRS specifications when compared to O 2 and NH 3 anneals. Decoupled plasma nitridation (DPN) with 7~9% N 2 content was employed for devices involving nitrided interfaces. Post-deposition anneals on such devices showed a suppressed effect as the input-referred noise was found to have similar values for the different conditions. The noise mechanism is also found to vary in devices with nitrided interface and no-PDA. A significant change in trap profile is noticed between nitrided and non-nitrided interfaces, which may be one of the causes for the differences observed. Lower trap densities are obtained from the trap profile for the non-nitrided no-anneal condition. Volume and interface trap densities, extracted from input-referred noise values, showed lowest values for a N 2 PDA anneal, while an O 2 anneal showed the highest values for non-nitrided devices. Devices with nitrided interfaces show similar value for all PDAs, with the values in-between the N 2 and the O 2 non-nitrided PDA.

The need for nitridation of Hf silicate is controversial. On one hand, it has not been proven that the nitridation is mandatory to have working devices and on the other hand, it is known to increase the charge density. In this paper, we present a detailed comprehensive study of the role and the need for nitridation of Hf-based silicates deposited by Atomic Layer Deposition (ALD). The results are based on a correlation of Fourier-Transformed Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), High-resolution Transmission Electron Microscopy (HR-TEM) and electrical measurements (gate leakage and mobility).It was observed that the phase segregation in gate dielectrics is not detrimental for the gate leakage density at room temperature. However, the leakage current is significantly increased at higher temperature. The incorporation of nitrogen was either done by NH 3 anneal (at 800C) or by Decoupled Plasma Nitridation (DPN -25.9kJ). While the DPN or NH 3 anneal prevent phase segregation for 50% Hf silicate, only the NH 3 anneal helps prevent the phase segregation of Hf-rich silicate. Furthermore, the NH 3 anneal increases the interfacial thickness, which produces a very low gate leakage with only 10% loss in mobility at high field. Interestingly, DPN followed by O 2 anneal leads to an advantageous phase segregation of the Hf-rich silicate by transforming the silicate in a HfO 2 /SiO 2 -like stack.As a conclusion, not only the phase segregation of the silicate does not always lead to shorted devices, but it can be beneficial in terms of mobility. However, the phase segregation seems to be responsible for an enlarged trap-assisted conduction mechanism at high temperature. But even if the 50% Hf silicates non-nitrided leads to working devices, the incorporation of nitrogen in the stack improves the Jg/CET trends and is therefore beneficial.