The TiO2∕SiO2 gate dielectric stack on 4H‐SiC substrate has been studied as a high-κ gate dielectric for metal-oxide semiconductor devices. X-ray photoelectron spectroscopy confirmed the formation of stoichiometric TiO2 films. The leakage current through the stack layer was investigated and it has been shown to be a double conduction mechanism. At low fields, the current is governed by properties of the interfacial layer with a hopping like conduction mechanism, while at relatively high electric field, carriers are modulated by a trap assisted tunneling mechanism through traps located below the conduction band of TiO2. The current-voltage characteristics, time evolution of charge transport, and capacitance-voltage behaviors under constant voltage stressing suggest the composite effect of electron trapping and positive charge generation in the dielectric stack layer.

Leakage current and charge trapping behavior in TiO2/SiO2 high-kappa gate dielectric stack on 4H-SIC substrate

In the advancement of metal–oxide–semiconductor technology, Si-based semiconductor, with SiO2 as outstanding dielectric, has been dominating microelectronic industry for decades. However, the drastic down-scaling in ultra-large-scale integrated circuitry has made ultrathin SiO2 (~1.2 nm) unacceptable for many practical reasons. Introduction of ZrO2 as high-κ dielectrics replacing SiO2 is undeniably a potential yet formidable solution for the aforementioned problem. The objective of this review is to present the current knowledge of ZrO2 thin film as gate dielectric on Si, in terms of its material and electrical properties produced by various deposition techniques. One of the techniques being focused is thermal oxidation of sputtered Zr and the mechanisms of transforming the metal into oxide has been extensively reviewed.

ZrO2 thin films on Si substrate

Hafnium aluminate (HfAlO) and nitrided hafnium aluminate (HfAlON) dielectrics were sputter deposited on Si (100) substrate. The N2∕(N2+Ar) flow ratio was varied between 0 and 66.6% in order to vary the nitrogen concentration. The Hf/Al ratio was varied from 0.5 to 1. In situ x-ray photoelectron spectroscopy and electrical measurements were utilized to characterize the as-deposited HfAlO and HfAlON films. The thermal stability studies of the HfAlO and HfAlON thin films after a 1000 °C, 10 s argon rapid thermal anneal were performed using grazing incidence x-ray diffraction and backside secondary ion mass spectrometry. Suppression of crystallization and no detectible outdiffusion of hafnium and aluminum into the silicon substrate were seen for HfAlO and HfAlON thin films with a Hf/Al ratio of 0.5.

Effect of composition on the thermal stability of sputter deposited hafnium aluminate and nitrided hafnium aluminate dielectrics on Si (100)

Effects of N2 and NH3 remote plasma nitridation on the structural and electrical characteristics of the HfO2 gate dielectrics

HfO2 films were grown on SiO2∕4H-SiC and SiON∕4H-SiC layers by deposition of metallic Hf in an electron beam evaporation system followed by thermal oxidation. X-ray photoelectron spectroscopy confirmed the formation of stoichiometric HfO2 films. There is no evidence of formation of hafnium silicide or carbon pileup at the surface as well as at the interfacial layer. Electrical measurements show the presence of fewer trapped charges in the HfO2∕SiON gate dielectric stack compared to HfO2∕SiO2 stack with a comparable interface state density. The HfO2∕SiON stack layer improves leakage current characteristics with a higher breakdown field and has smaller flatband voltage shift under electrical stress, indicating improved reliability.

Effects of interface engineering for HfO2 gate dielectric stack on 4H-SiC

The interfacial characteristics of high-κ HfO2 on NH3- and N2O-plasma treated p-Si substrates have been investigated using high-resolution transmission electron microscopy (HRTEM), time-of-flight secondary ion mass spectroscopy (ToF-SIMS), and auger electron spectroscopy (AES). NH3- and N2O-plasma treated films show the formation of a nitrogen-rich Hf-silicate interfacial layer between the deposited HfO2 and Si substrates. The electrical characteristics have been studied using metal–oxide-semiconductor (MOS) structures. Interfacial nitrogen increases the capacitances by ∼33% for NH3 and ∼47% for N2O-treated Si as compared to the untreated surface. A dielectric constant of ∼26 for HfO2 film, ∼6.0 for Hf-silicate, ∼9.0 for NH3- and ∼11.0 for N2O-treated interfacial layers have been calculated from the accumulation capacitances of the MOS capacitors. The relatively higher dielectric constant, lower capacitance equivalent thickness (CET), lower leakage current and higher breakdown voltage for N2O-plasma treated film makes it attractive for scaled Si MOSFET applications.

Samik Pal

Papers

Effects of interfacial NH3/N2O-plasma treatment on the structural and electrical properties of ultra-thin HfO2 gate dielectrics on p-Si substrates