Reactive Dc Magnetron Sputter Deposition Research Articles

Reactive DC magnetron sputter deposition and structural properties of NiO thin films

Reactive DC magnetron sputter deposition and structural properties of NiO thin films

Influence of particle and energy flux on stress and texture development in magnetron sputtered TiN films

The real-time stress evolution during reactive dc magnetron sputter deposition of TiN films in Ar+N2 plasma discharge was measured in situ using a multiple-beam optical stress sensor, while the film texture was determined ex situ using x-ray diffraction. The influence of atomic N/Ti flux and energy flux, previously quantified by combining plasma characterization and Monte Carlo simulations (2009 J. Phys. D: Appl. Phys. 42 053002), was investigated by varying either the N2 partial pressure at fixed total pressure, the total working pressure or the bias voltage applied to the substrate. The contribution of thermal stress was carefully taken into account from thermal probe measurements to evaluate the intrinsic (growth) stress from the measured film force data. A clear correlation between stress, film texture and energy flux is evidenced: while underdense (1 1 1)-textured TiN films with ‘V’-shaped columnar growth (zone T) are under tensile stress (up to +0.6 GPa), dense TiN films with zone II microstructure develop a (0 0 2) texture and large compressive stress (up to 3 GPa) when the energy flux is higher than ∼150 eV per incoming particle. However, it is shown that a positive or negative bias voltage, though increasing the energy flux, did not promote a (0 0 2) texture. It is concluded that compressive stress development and (0 0 2) preferential growth are both kinetically driven processes in magnetron sputtered TiN layers, but exhibit distinct dependence with the substrate fluxes.

The influence of non-uniform target poisoning on the energy distributions of atoms sputtered in a reactive dc magnetron discharge

The lateral variation of the energy distributions of sputtered Ti atoms has been investigated by energy resolved mass spectrometry during reactive dc magnetron sputter deposition of TiN from a Ti target in an argon/nitrogen gas mixture. The mass spectrometer was placed at the substrate position and scanned across the target surface of a 2 inch planar circular magnetron. The energy distribution of sputtered particles is influenced by their origin, showing significant differences between the center and the erosion zone of the target. The results are interpreted in terms of laterally different states of target poisoning, which results in a variation of the surface binding energy. The reactive gas target coverage as derived from the sputtered energy distributions is in reasonable agreement with predictions from model calculations.

Fabricating highly active mixed phase TiO 2 photocatalysts by reactive DC magnetron sputter deposition

Recent work points out the importance of the solid–solid interface in explaining the high photoactivity of mixed phase TiO 2 catalysts. The goal of this research is to probe the structural and functional relationships of the solid–solid interface created by the reactive DC magnetron sputtering of titanium dioxide. We show that sputter deposition provides excellent control of the phase and interface formation. We explored the effects of the process parameters of pressure, oxygen partial pressure, target power, substrate bias (RF), deposition incidence angle, and post annealing treatment on the structural and functional characteristics of the catalysts. We have successfully made pure and mixed phase TiO 2 films. These films were characterized with AFM, SEM, TEM, and XRD to determine surface morphology, phase distribution and phase content. The performance as photocatalytic surfaces was measured and compared (normalized for surface area) to mixed phase TiO 2 fabricated by other methods, including flame hydrolysis powders, and sol–gel deposited TiO 2 films. The sputtered mixed phase materials were far superior to the commercial standard (Degussa P25) and sol–gel TiO 2 as measured by the gas phase oxidation of the air pollutant acetaldehyde under UV illumination. These results demonstrate that reactive DC magnetron sputtering is a powerful tool for investigating the role of the solid–solid interface in influencing photocatalytic activity. In addition, our work illustrates the feasibility of reactive DC magnetron sputtering as a practical commercial technique for manufacturing highly active nanostructured TiO 2 photocatalysts.

Interface Formation and Electrical Properties of TiOxNy/HfO2/Si Structure

In this work, interface formation and electrical properties of the interface between TiOxNy and HfO2 for application of gate structure were investigated as a function of annealing temperature. HfO2 layers were formed at 500°C by the thermal oxidation of the sputter-deposited Hf layers on n-Si (001) and followed by reactive DC magnetron sputter deposition of TiOxNy layers at room temperature. Phase identification of TiOxNy layers before and after thermal annealing of TiOxNy(100 nm)/HfO2/Si by X-ray diffraction (XRD) indicates the formation of TiO1-zNz with the preferential orientations in (111), (200) and (220) directions. Depth profiling analysis of Ti, Si, Hf, N, and O element for TiOxNy(50 nm)/HfO2/Si structure by Auger electron spectroscopy (AES) shows the increased oxidation of TiOxNy layers at elevated annealing temperature, TA = 800°C. Investigation of the interfacial reaction of TiOxNy(5 nm)/HfO2 by depth profiling using X-ray photoelectron spectroscopy (XPS) shows the existence of mixture of TiO1-zNz and TiO2 (or TiO) phase and increased fraction of TiO2 phase and Hf–O bondings for the samples annealed at the elevated annealing temperature, TA = 800°C. Sheet resistance of TiOxNy/HfO2/Si systems measured by a four-point probe shows the initial decrease in RS values but the abrupt increase in RS values at TA = 800°C. The combined results indicate that TiOxNy layer acts as an effective diffusion barrier for Hf and O element in the HfO2 layer at the annealing temperature ≤700°C, but O and Hf diffused out of the HfO2 layers reacted with TiOxNy layers at the elevated annealing temperature of 800°C.

Growth of Tetragonal Zirconia Coatings by Reactive Sputter Deposition

Zirconia coatings were produced by reactive dc magnetron sputter deposition, using a system with multiple sputter sources and a biased substrate stage. Tetragonal zirconia with either a random orientation or a highly (111) preferred orientation was formed by applying a substrate bias. Coating grown with no substrate bias had the equilibrium monoclinic structure. X‐ray diffraction and transmission electron microscopy analyses revealed that bias sputtering could effectively decrease crystalline size in the as‐deposited coating, which resulted in room‐temperature stabilization of the tetragonal phase. The fraction of tetragonal phase, the desired phase for transformation‐toughening behavior, was strongly dependent on the substrate bias and post‐deposition annealing temperature.

Enhanced quality of epitaxial AlN thin films on 6H–SiC by ultra-high-vacuum ion-assisted reactive dc magnetron sputter deposition

Epitaxial AlN thin films have been grown on 6H–SiC substrates by ultra-high-vacuum (UHV) ion-assisted reactive dc magnetron sputtering. The low-energy ion-assisted growth (Ei=17–27 eV) results in an increasing surface mobility, promoting domain-boundary annihilation and epitaxial growth. Domain widths increased from 42 to 135 nm and strained-layer epitaxy was observed in this energy range. For Ei>52 eV, an amorphous interfacial layer of AlN was formed on the SiC, which inhibited epitaxial growth. Using UHV condition and very pure nitrogen sputtering gas yielded reduced impurity levels in the films (O: 3.5×1018 cm−3). Analysis techniques used in this study are in situ reflection high-energy electron diffraction, secondary-ion-mass spectroscopy, atomic-force microscopy, x-ray diffraction, and cross-section high-resolution electron microscopy.

Thermal stability of nonstoichiometric silicon nitride films made by reactive dc magnetron sputter deposition

Silicon nitride Si 100N x films were made by reactive dc magnetron sputtering in the composition range between 0≤ x≤133 (Si 100N 133⇔Si 3N 4). Electrical conduction and optical transmission of the films were measured before and after annealing. X-ray diffraction, RBS, Raman and FTIR spectroscopy were used to identify the structural and compositional changes in the films. The variation of the electrical resistivity upon annealing can be explained by the number of dangling bonds, by oxidation of the film's surface, and by the formation of crystalline silicon in the films above about 800°C. The change of film properties upon annealing depends on the sputtering conditions.

High rate reactive dc magnetron sputter deposition of Al2O3 films

Aluminum oxide films were produced by reactive dc magnetron sputtering of Al in Ar+O2. The composition of the films was characterized by Rutherford backscattering measurements. Stoichiometric films possessed excellent optical properties with a refractive index of ∼1.6 for visible and near-infrared light. It was possible to produce stoichiometric films while keeping the target in the metallic mode of operation; the resulting deposition rate was 23 nm min−1, as compared to 0.95 nm min−1 for films grown from an oxidized target. An O/Al arrival rate ratio exceeding ∼17 was required for stoichiometric films to be grown at room temperature. The success of the present high-rate deposition strategy hinges on the use of a suitable deposition system geometry — including a large target-to-substrate distance and a small target size — and on the use of sufficient Ar pressure. Monte Carlo simulations are presented; they can be reconciled with our empirical data.

Epitaxial Aluminum Nitride Film on Silicon(111) Grown by Reactive DC Magnetron Sputter Deposition

An Auger electron spectrum of an aluminum nitride thin film is presented. The film was prepared by reactive dc magnetron sputter deposition onto a silicon wafer substrate. The film was grown epitaxially on the Si(111) substrate. The film was also characterized using electron probe microanalysis, x-ray diffraction, and transmission electron microscopy.

Silicon epitaxy at 230 °C by reactive dc magnetron sputtering and its in situ ellipsometry monitoring

We report epitaxial growth of silicon on Si(100) at 230 °C by reactive dc magnetron sputter deposition. Growth is monitored with in situ multiwavelength ellipsometry to determine the film microstructure. Film crystallinity depends on the partial pressure of hydrogen during deposition, and the best film is obtained with 2 mTorr H2. The films are found to have a bulk density deficit of a few percent and a low-density layer at the film-substrate interface. The microstructure is confirmed by transmission electron microscopy measurements. Infrared absorption and thermal hydrogen evolution measurements indicate that a large amount of molecular hydrogen is present at the substrate interface. We discuss the possible roles of hydrogen and particle bombardment in promoting epitaxial growth.

Hydrogenation induced changes in band states in a-Si:H

We have determined the valence and conduction band density of states (DOS) in a-Si:H by fitting the dielectric spectra measured by spectroscopic ellipsometry. The films are grown by reactive dc magnetron sputter deposition. We find that hydrogenation reduces the states near the valence band edge, and increases those deeper in the valence band. In addition, SiH anti-bonding states are observed about 1.5 eV above the conduction band edge. These changes are systematic with hydrogen content in the film.

The Structures of Tantalum Pentoxide Film Formed by Reactive DC Magnetron Sputter-Deposition of Ta

ABSTRACTTantalum pentoxide (Ta2O5) films are candidates for application as storage capacitors in high density memory cells and as gate insulators in MOS devices because of their large dielectric constant. Thin Ta2O5 films deposited by reactive DC magnetron sputtering of a pure Ta target using an argon/oxygen mixture have been characterized using TEM, glancing angle X-ray diffraction and RBS. The films are amorphous in the as-deposited condition but crystallize after high temperature (> 600 °C) annealing. Numerous pores and significant grain boundary grooving were observed in the crystallized film. A high level (∼2 at. %) of argon was detected in both as-deposited and annealed films formed by Ar/O2 sputtering. The effects of sputtering and annealing conditions on the structure of the films were investigated.