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Abstract: ZrO x N y thin films have been prepared by radio frequency magnetron sputtering at various substrate temperatures. The effect of substrate temperature on structural, optical properties and energy-band alignments of as-deposited ZrO x N y thin films are investigated. Atomic force microscopy results indicate the decreased root-mean-square (rms) values with substrate temperature. Fourier transform infrared spectroscopy spectra indicate that an interfacial layer has been formed between Si substrate and ZrO x N y thin films during deposition. X-ray photoelectron spectroscopy and spectroscopy ellipsometry (SE) results indicate the increased nitrogen incorporation in ZrO x N y thin films and therefore, the decreased optical band gap (E g) values as a result of the increased valence-band maximum and lowered conduction-band minimum. [Copyright &y& Elsevier]

Abstract: High-k HfO x N y thin films with different nitrogen-incorporation content have been fabricated on Si (100) substrate by means of radio-frequency reactive sputtering method. Analyses from X-ray diffraction (XRD) and atomic force microscopic have indicated that the increase of the crystallization temperature of HfO2 thin films and the decrease of the roughness root-mean-square value of HfO2 thin films due to the incorporation of nitrogen. Based on a parameterized Tauc–Lorentz (TL) dispersion model, the optical properties of the HfO x N y thin films related to different nitrogen-incorporation content are systematically investigated by spectroscopic ellipsometer. Increase in the refractive index and the extinction coefficient and reduction in band gap with increase of nitrogen-incorporation content are discussed in detail. [Copyright &y& Elsevier]

Abstract: Hafnium oxynitride (HfO x N y ) gate dielectric has been deposited on Si (100) by means of radio frequency (rf) reactive sputtering using directly a HfO2 target in N2/Ar ambient. The thermal stability and microstructural characteristics for the HfO x N y films have been investigated. XPS results confirmed that nitrogen was successfully incorporated into the HfO2 films. XRD analyses showed that the HfO x N y films remain amorphous after 800°C annealing in N2 ambient. Meanwhile the HfO x N y films can also effectively suppress oxygen diffusion during high temperature annealing and prevent interface layer from forming between HfO x N y films and Si substrates. AFM measurements demonstrated that surface roughness of the HfO x N y films increase slightly as compared to those pure HfO2 films after post deposition annealing. By virtue of building reasonable model structure, the optical properties of the HfO x N y films have been discussed in detail. [Copyright &y& Elsevier]

X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and work-function measurements have been used to investigate the Y/SiO2/Si(1 0 0) interfaces in situ as a function of annealing temperature. The results show that yttrium is very reactive with SiO2 and can react with SiO2 to form Y silicate and Y2O3 even at room temperature. Annealing leads to the continual growth of the Y silicate. Two distinctive reaction mechanisms are suggested for the annealing processes below and above 600 K. The reaction between metallic yttrium and SiO2 dominates the annealing processes below 600 K, while at annealing temperatures above 600 K, a reaction between the new-formed Y2O3 and SiO2 becomes dominant. No Y silicide is formed during Y deposition and subsequent annealing processes. UPS valence-band spectra indicate the silicate layer is formed at the top surface. After 1050 K annealing, a Y-silicate/SiO2/Si structure free of Y2O3 is finally formed. [Copyright &y& Elsevier]

Abstract: Hf1−x Si x O y is an attractive candidate material for high-k dielectrics. We report in this work the deposition of ultra-thin Hf1−x Si x O y films (0.1≤ x ≥0.6) on silicon substrate at 450°C by UV-photo-induced chemical vapour deposition (UV-CVD) using 222nm excimer lamps. Silicon(IV) and hafnium(IV) organic compounds were used as the precursors. Films from around 5 to 40nm in thickness with refractive indices from 1.782 to 1.870 were grown. The deposition rate was found to be of 6nm/min at a temperature of 450°C. The physical, interfacial and electrical properties of hafnium silicate (Hf1−x Si x O y ) thin films were investigated by using X-ray photoelectron spectroscopy, ellipsometry, FT-IR, C–V and I–V measurements. XRD showed that they were basically amorphous, while Fourier transform infrared spectroscopy (FT-IR), clearly revealed Hf–O–Si absorption in the photo-CVD deposited Hf1−x Si x O y films. Surface and interfacial properties were analysed by TEM and XPS. It is found that carbon content in the films deposited by UV-CVD is very low and it also decreases with increasing Si/(Si+Hf) ratio, as low as about 1at.% at the Si/(Si+Hf) ratio of 60at.%. [Copyright &y& Elsevier]

Abstract: High-k gate dielectric HfO2 thin films have been deposited on Si(100) by using plasma oxidation of sputtered metallic Hf thin films. The optical and electrical properties in relation to postdeposition annealing temperatures are investigated by spectroscopic ellipsometry (SE) and capacitance–voltage (C–V) characteristics in detail. X-ray diffraction (XRD) measurement shows that the as-deposited HfO2 films are basically amorphous. Based on a parameterized Tauc–Lorentz dispersion mode, excellent agreement has been found between the experimental and the simulated spectra, and the optical constants of the as-deposited and annealed films related to the annealing temperature are systematically extracted. Increases in the refractive index n and extinction coefficient k, with increasing annealing temperature are observed due to the formation of more closely packed thin films and the enhancement of scattering effect in the targeted HfO2 film. Change of the complex dielectric function and reduction of optical band gap with an increase in annealing temperature are discussed. The extracted direct band gap related to the structure varies from 5.77, 5.65, and 5.56eV for the as-deposited and annealed thin films at 700 and 800°C, respectively. It has been found from the C–V measurement the decrease of accumulation capacitance values upon annealing, which can be contributed to the growth of the interfacial layer with lower dielectric constant upon postannealing. The flat-band voltage shifts negatively due to positive charge generated during postannealing. [Copyright &y& Elsevier]

Abstract: High-k HfO2–Al2O3 composite gate dielectric thin films on Si(100) have been deposited by means of magnetron sputtering. The microstructure and interfacial characteristics of the HfO2–Al2O3 films have been investigated by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and spectroscopic ellipsometry (SE). Analysis by XRD has confirmed that an amorphous structure of the HfO2–Al2O3 composite films is maintained up to an annealing temperature of 800°C, which is much higher than that of pure HfO2 thin films. FTIR characterization indicates that the growth of the interfacial SiO2 layer is effectively suppressed when the annealing temperature is as low as 800°C, which is also confirmed by spectroscopy ellipsometry measurement. These results clearly show that the crystallization temperature of the nanolaminate HfO2–Al2O3 composite films has been increased compared to pure HfO2 films. Al2O3 as a passivation barrier for HfO2 high-k dielectrics prevents oxygen diffusion and the interfacial layer growth effectively. [Copyright &y& Elsevier]