Supratic Chakraborty

Evidence of swelling of SiO2 upon thermal annealing

Ultrathin SiO2 film was thermally grown on Si(001) substrate by dry oxidation and wet oxidation processes. The films were then subjected to thermal annealing (TA) at 1000 °C for 30 min. The structural characterization of the as-grown and the TA samples was carried out using the grazing incidence x-ray reflectivity technique. The analysis of the x-ray reflectivity data was carried out by using a model independent formalism based on the distorted wave Born approximation for obtaining the electron density profile (EDP) of the film as a function of depth. The EDP of both films show a decrease in the electron density as well as an increase in their thickness when the films are subjected to TA. It has also been observed that the total number of electrons is conserved in the oxide film after TA. Our analysis of the x-ray reflectivity data indicates that the SiO2 film swells and its interface with the substrate modifies upon TA.

Optimization of annealing temperature for high-κ-based gate oxides using differential scanning calorimetry

This study investigates the crystallization process for thin high-κ dielectric films and optimal annealing temperature range in the field of high-κ dielectric-based metal-oxide-semiconductor (MOS) technology. A differential scanning calorimetry (DSC) technique is employed to understand the thermal behavior of thin high-κ dielectric HfO2 films deposited on Si by radio frequency sputtering. The exothermic trends of the DSC signal and grazing incidence x-ray diffraction data indicate an amorphous-to-crystalline transition in the high-κ films at higher temperatures. The enthalpy-temperature variation indicates a glass temperature (Tg) at ∼590 °C, beyond which an amorphous to m-HfO2 crystalline transition takes place. Further, the Hf-silicate formation, observed in DSC measurements and corroborated by Fourier transformed infrared spectroscopy studies, indicates that the process of Hf-silicate formation begins at ∼717 °C. High-frequency capacitance–voltage (C–V) and current density–voltage (J–V) characteristics...

Effect of thermal annealing and oxygen partial pressure on the swelling of HfO2/SiO2/Si metal-oxide-semiconductor structure grown by rf sputtering: A synchrotron x-ray reflectivity study

As-grown and rapid thermal annealed thin HfO2 films, deposited on Si(100) substrate by reactive rf sputtering at various partial pressures of O2 and Ar, are studied by synchrotron x-ray reflectivity. The growth of interfacial layer (IL) of SiO2 is more or less linear with the decrease in oxygen partial pressure ( pO2) in the O2/Ar mixture. The thickest oxide is found to be grown at the minimum oxygen partial pressure ( pO2). It is observed that the IL swells upon annealing at higher temperature, and swelling is maximum for the sample grown in minimum pO2. The surface roughness and thickness of the HfO2 films decrease upon annealing indicating a denser film. The HfO2/Si interface roughness is also decreased upon annealing. Therefore, lower annealing temperature and higher pO2 is to be set to reduce the IL thickness and for higher dielectric constant and larger oxide capacitance. High frequency capacitance-voltage (C–V) measurement on the devices, annealed at higher temperature, further shows the necessity ...

Effect of excess hafnium on HfO2 crystallization temperature and leakage current behavior of HfO2/Si metal-oxide-semiconductor devices

This article reports the role of excess Hf on the crystallization temperature of thin HfO2 film and leakage current behavior of Hf-rich HfO2/Si metal-oxide-semiconductor (MOS) devices. The HfO2 thin-films deposited by the radio-frequency sputtering system with different Ar:O2 gas mixtures are studied by differential scanning calorimetry. The crystallization temperature of Hf-rich HfO2 film is found to be lower than that of the HfO2 film. The grazing incidence x-ray diffraction studies also confirm the above observation. X-ray photoelectron spectroscopy study further indicates the presence of excess Hf in the oxide film. Enhanced structural relaxation in the presence of excess Hf in HfO2 film releases energy, already stored within the film during deposition, which is responsible for lowering of crystallization temperature. The gate leakage current characteristics are deteriorated in the presence of excess Hf in the HfO2/Si MOS device.

Density profiles and electrical properties of thermally grown oxide nanofilms on p-type 6H-SiC(0001)

Thermally grown silicon oxide films on p-type 6H–silicon carbide substrate under different oxidation and nitridation conditions have been characterized by x-ray reflectivity technique. An electron density profile obtained from the analysis of the x-ray reflectivity data shows that the thickness, density of the oxide film, and structure of the oxide-SiC interface strongly depend on the different growth conditions. In particular, the density of the oxide film for all samples other than that grown in NO is found to be much lower and also not fixed within. It is maximum at the interface and gradually decreases toward the top in all samples except for the sample grown in O2 followed by NO nitridation. For the latter, a very low density at the interface region has been observed. The sample grown in NO shows the best performance in capacitance–voltage characteristic and reliability studies suggesting that the bad performance of the oxide grown on the p-type SiC system as metal–oxide–semiconductor devices, is mai...

Influence of rapid thermal annealing on electrical performance and reliability of HfO2 based MOS device

The stability of dielectric properties of the thin film under high voltage stress and variation of electrical behavior with the rapid thermal annealing (RTA) of thin HfO2 dielectric film (∼ 7.5 nm) based MOS devices are studied by gate current – gate voltage (I-V), high frequency (HF) capacitance – voltage (C-V) characteristics. The device fabricated using high temperature annealed films shows better and stable performance under high voltage stress due the crystallization of the films.

Effect of N2O ratio on the crystallization temperature of ZrO2 film deposited on Si by reactive sputtering in Ar/O2/N2O plasma

The effect of nitrous oxide ratios in the Ar/ O2/ N2O plasma on the ZrO2 films deposited on Si using dc magnetron reactive system is studied by differential scanning calorimetry (DSC) where the Ar:O2 ratio is fixed at 4:1. Further, grazing angle x-ray reflectivity (GIXRR), grazing angle x-ray diffraction (GIXRD) and atomic force microscopy (AFM) techniques are also employed to characterize the films. The DSC study shows an anomalous variation of the glass temperature when the N2O ratio in the Ar/O2/N2O plasma changes from 0.25 to 2 with respect to the control ZrO2 sample deposited without N2O. An increase in glass temperature by ~70 °C is observed for the N2O ratio at 1. A further rise in N2O ratio results in the reduction of the glass temperature. The GIXRR study indicates that the thickness of the samples decreases with the increase in N2O ratios beyond 0.8. Further, increasing N2O ratio results in an increase in surface and interface roughness for the as-deposited samples. But both the roughnesses decrease upon annealing the samples above their respective crystallization temperatures. The AFM results also corroborates the observation. Moreover, the GIXRD study indicates the formation of Γ-Zr2ON2 along with the monoclinic and tetragonal ZrO2 at the highest ratio of N2O in the Ar:O2:N2O plasma.

Study of temperature dependent zirconium silicide phases in Zr/Si structure by differential scanning calorimetry

The differential scanning calorimetry (DSC) technique is employed to study the formation of different silicide compounds of Zr thin-film deposited on a 100 μm-thick Si (1 0 0) substrate by dc sputtering. A detailed analysis shows that silicide layers start growing at ~246 °C that changes to stable ZrSi2 at 627 °C via some compounds with different stoichiometric ratios of Zr and Si. It is further observed that oxygen starts reacting with Zr at ~540 °C but a stoichiometric ZrO2 film is formed after complete consumption of Zr metal at 857 °C. A further rise in temperature changes a part of ZrSi2 to Zr-Silicate. The synchrotron radiation-based grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy studies also corroborate the above findings. Atomic force microscopy is also carried out on the samples. It is evident from the observations that an intermixing and nucleation of Zr and Si occur at lower temperature prior to the formation of the interfacial silicate layer. Zr-Silicate formation takes place only at a higher temperature.

Oxidation kinetics of \hbox {ZrO}_2 films on Si by differential scanning calorimetry

Differential scanning calorimetry (DSC) technique is employed to study the growth kinetics of zirconium dioxide where oxidation of a 23 nm-thick Zr film, deposited on Si (100) substrate using dc sputtering system, is studied in O2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}