Sputtering Gas Pressure Research Articles

The effect of nitrogen partial pressure on the bonding in sputtered CN x films: implications for formation of β-C 3N 4

An investigation of the bonding structure in carbon nitride films deposited by DC magnetron sputtering using a Penning-type opposed target system has been carried out. The changes in the valence band structure have been measured by XPS, UPS and EELS. The density of unpaired electrons has been measured by ESR. As the nitrogen partial pressure and the nitrogen content of the films is initially increased, the structure shows a greater degree of sp 2 bonding compared to the pure carbon samples. However, with further increases in the nitrogen partial pressure up to 100% of the sputtering gas pressure, which has very little effect on the nitrogen content of the films, the bonding becomes more sp 3-like in character and there is evidence for a reduction in the network terminating CN bonding. Under these circumstances the sp 3-like nature becomes comparable to or greater than that for un-nitrogenated films. These results point to the reasons why crystalline β-C 3N 4 material has been found in these films only with high nitrogen partial pressure even though the nitrogen content is not significantly enhanced in this situation.

Structural properties of slightly off-stoichiometric homoepitaxial SrTixO3−δ thin films

Ti-deficient SrTixO3−δ films, x<1, were grown on 〈100〉 oriented SrTiO3 single crystal substrates by radio frequency magnetron sputtering from stoichiometric targets. The Ti-deficiency was adjusted by the sputtering gas pressure. The Ti/Sr cation ratio, x, was determined by Rutherford backscattering and energy dispersive x-ray analysis in a scanning electron microscope. To obtain information on the Ti/O ratio, x-ray absorption spectroscopy was carried out as well. We investigated SrTixO3−δ films with x=0.98, 0.95, and 0.89. The epitaxial growth and lattice imperfections were characterized by x-ray diffraction, electron diffraction, and high resolution transmission electron microscopy. The films crystallized in a tetragonal structure with a maximum mosaic spread of about 0.1°. The c axis was oriented perpendicular to the substrate surface where the c-lattice parameter was increasing with decreasing x. For x>0.89, the Ti deficiency was primarily compensated by a change of the site occupation on the cation sublattices in combination with oxygen vacancies, i.e., the formation of SrTi and VO point defects, whereas for x<0.95 the intergrowth of homologs series of the Ruddlesden–Popper phases, Srn+1TinO3n+1, was observed. The dielectric properties of the films are briefly discussed in terms of (SrTiVO) defect complexes.

Improvement of Y 2O 3/Si interface for FeRAM application

We attempted to improve the dielectric properties of sputter deposited Y 2O 3 thin film on Si for the buffer layer of Ferroelectric Random Access Memory (FeRAM) application. Although the use of Xe as a sputtering gas was effective to improve the crystallinity of Y 2O 3 film on Si compared to that of the film deposited using Ar gas, oxygen deficiency in the film was enhanced by use of Xe gas. Increasing the total sputtering gas pressure was effective for improving the oxygen deficiency. The Y 2O 3 film sputtered at the total gas pressure of 20 mTorr has little positive charges and shows excellent dielectric properties as insulator. Effect of the substrate cleaning was also studied for decreasing the interface state density and the shift of flat band voltage.

Effect of deposition conditions on internal stresses and microstructure of reactively sputtered tungsten nitride films

A combined investigation of internal stress generation by in situ substrate curvature measurements during the growth of tungsten nitride (WN x ) thin films and of structural properties by ex situ X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electron energy-loss spectroscopy (EELS) is reported. It was found that the properties of the deposited films not only depended on the nitrogen partial pressure in Ar–N 2 gas mixtures but also on the total sputtering-gas pressure. The stress of the films was strongly related to their microstructure, which depended mainly on the incorporation of nitrogen in the films. Annealing of as-deposited films at 600°C or above resulted in crystallization of the amorphous phases, forming either a two-phase structure consisting of W 2N and b.c.c. W or a single-phase structure of W 2N, which was related to the initial nitrogen concentration ( C N) in the films. Cross-sectional TEM studies showed that an average column width for 150-nm-thick films near stoichiometry of W 2N was ∼15 nm, whereas the column grains were larger with decreasing C N. XPS results revealed that W 2N had an ionic bonding character, W δ+–N δ−. It was also found that once the W 2N phase was formed, the density, microstructure and bonding feature were similar and insensitive to the total sputtering-gas pressure used in this study.

Correlations among sputter pressure, thickness, and coercivity in Al/Co/Cu magnetic thin films sputtering

We demonstrate the effect of sputter gas pressure and film thickness, d, on the coercivity of Co in Al/Co/Cu sputterdeposited on Si(001). Increased sputter gas pressure produces increased rms roughness and increased O content in our films. The deposited Co thickness at which the onset of ferromagnetism is first observed, dc, increases with sputter gas pressure. Above this thickness,d > dc, the coercivity increases with increasing Co thickness. For film thickness d ≫ dc, the coercivity is thickness independent. We show that coercivity is directly controllable at technologically relevant thicknesses by regulating sputter-deposition parameters.

Giant magnetostriction of TbFe monolayers with improved field-induced sensitivity

Giant magnetostriction, (GMS), reported until now in thin films using rare earth-transition metal RM/sub 2/ (R=Tb, Sm, and M=Fe, Co) compounds, presents in most cases an isotropic or quasi-isotropic magnetoelastic (ME) behavior. A large change of the ME coefficient b under the lowest possible external field is required in order to improve the sensitivity of these materials which are interesting for their application in microelectromechanical systems (MEMS). The present paper shows the possibility of improving strongly both the ME coefficient and sensitivity. Optimized ME properties are correlated with the sputtering parameters such as the RF power P/sub rf/ and the sputtering gas pressure P/sub Ar/. The magnetostriction increases with P/sub rf/ up to very large saturation values not observed until now in TbFe films (/spl Delta/l/l=1300 ppm or b/sup /spl gamma/,2/=50 MPa at 20 kOe) due to a structural change from amorphous at low P/sub rf/ to crystallized phase at a high P/sub rf/ as confirmed from XRD. When a bias magnetic field H/sub d/ is applied on the film during deposition a strong change is seen in the structural, elastic, magnetic and ME properties, H/sub d/ keeps the amorphous phase even at high P/sub rf/ which induces a reduction of the ME "linewidth" but an increase of the GMS sensitivity.

In-Plane Texturing in Sputtered Films

Films consisting of Mo, Cr, and Ta have all been found to display well-defined biaxial textures when grown under certain conditions. A well-defined out-of-plane texture evolves within the first ~ 100 nm of the film, followed by the evolution of a preferred crystallographic orientation in the plane of the film. These effect were studied using X-ray pole figure analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), transmission electron diffraction (TED), and high resolution grazing incidence X-ray scattering (GIXS). It has been found that in-plane texture evolves only when there is, on average, oblique adatom flux incident onto the substrate. Further, the type of out-of-plane texture can be controlled by altering the deposition conditions. Parameters including cathode-to-substrate distance, deposition rate, average angle of adatom incidence, and sputter gas pressure, have been shown to determine the type out-of-plane texture, as well as the rate of in-plane texture evolution. The studies conducted have shown that it is possible to create and control biaxially textured films and multilayers made of a variety of materials. A recent model which describes this phenomena is discussed.

Residual stress, microstructure, and structure of tungsten thin films deposited by magnetron sputtering

The residual stress and structural properties of tungsten thin films prepared by magnetron sputtering as a function of sputtering-gas pressure are reported. The films were analyzed in situ by a cantilever beam technique, and ex situ by x-ray diffraction, cross-sectional transmission electron microscopy (TEM), x-ray photoelectron spectroscopy, electron energy-loss spectrometry, and energy-filtered electron diffraction. It is found that the residual stress, microstructure, and surface morphology are clearly correlated. The film stresses, determined in real time during the film formation, depend strongly on the argon pressure and change from highly compressive to highly tensile in a relatively narrow pressure range of 12–26 mTorr. For pressures exceeding ∼60 mTorr, the stress in the film is nearly zero. It is also found that the nonequilibrium A15 W structure is responsible for the observed tensile stress, whereas the stable bcc W or a mixture of bcc W and A15 W are in compression. Cross-sectional TEM evidence indicates that the compressively stressed films contain a dense microstructure without any columns, while the films having tensile stress have a very columnar microstructure. High sputtering-gas pressure conditions yield dendritic-like film growth, resulting in complete relaxation of the residual tensile stresses. Structural details of the A15 W and amorphous W phases were also investigated at the atomic level using energy-filtered electron diffraction with reduced radial distribution function G(r) analysis. By comparing the experimental and simulated G(r) distributions, the A15 W structure is determined to be composed of ordered and stacking faulted W3W structures and the amorphous W has a disordered structure of W3O. The effect of oxygen in stabilizing the A15 phase found is explained on the basis of structural and thermodynamic stability.

Properties of zirconium oxide thin films deposited by pulsed reactive magnetron sputtering

Abstract Zirconium oxide thin films were deposited by direct current (d.c.) reactive magnetron sputtering on glass slide, silicon wafer and stainless steel substrates. The thickness of the thin films was between 200 nm and 3 μm. The target power density controlled deposition process was used. The process parameters investigated were the target power, the sputtering gas pressure and the substrate bias voltage and their influence was studied on the film properties such as O/Zr ratio, density, nanohardness, intrinsic stress, crystallographic structure and surface roughness. The deposition rate increased as a function of the target power, the sputtering gas pressure and the substrate bias voltage. The nature of the residual stress changed from compressive to tensile as the sputtering gas pressure was increased. The nanohardness of the thin films increased with decreasing sputtering gas pressure and with increasing substrate bias voltage. The thin films were colourless and transparent when fully oxidised to monoclinic structure, black when rich in metal. These black substoichiometric thin films with the O/Zr ratio of 1.6 had a tetragonal structure. Black thin films represented low nanohardness and strongly increased surface roughness.

Deposition of aluminium oxide thin films by reactive magnetron sputtering

Aluminium oxide thin films were deposited by direct current (d.c.) reactive magnetron sputtering on glass-slide, silicon wafer, stainless-steel and polycarbonate substrates. The thicknesses of the films were between 200 nm and 3.0 μm. The deposition was controlled by the target voltage to obtain stoichiometric thin films with a high deposition rate. The deposition process was studied in terms of target power, I–U characteristics of the target, sputtering gas pressure and substrate bias voltage. The film properties of interest were O/Al ratio, density, nanohardness, intrinsic stress, crystallographic structure and surface roughness. The deposition rate obtained for stress-free and transparent aluminium oxide thin film was 215 nm min−1, 77% of the rate of metallic aluminium.

Surface defects and arc generation in reactive magnetron sputtering of aluminium oxide thin films

Arcing phenomena and defect density on the surface of aluminium oxide thin films have been investigated as a function of process parameters such as pulsing frequency, substrate bias voltage, target voltage and sputtering gas pressure. The thin films were deposited by direct current reactive magnetron sputtering techniques. The deposition of the thin films was controlled by target voltage. A pulsed power supply at low and medium frequency range (2–50 kHz) was used to improve the stability of the deposition process and to reduce the surface defect density. Target poisoning led to arcing and an unstable deposition process, which, in turn, resulted in defects on the surface of the thin films. Target poisoning was minimised by depositing the thin films at high target voltages at a pre-set target power density. Mainly microarcing during the deposition was observed. Strong arcing resulted in rough coating surfaces and metallic aluminium droplet contamination. The changes in the appearance of the thin films from transparent colourless to transparent opaque were observed.

Control of crystal orientation of Ti thin films by sputtering

We developed a new sputter deposition technique called sputter beam deposition (SBD) in which both the kinetic energy and the distribution of incident angles of the deposition particles are controlled. In this study, Ti films with hcp structure were deposited by both SBD and conventional dc magnetron sputtering. The crystal orientation of the film depended considerably on the kinetic energy of the depositing atoms. Film with c-axis orientation was obtained when most of the depositing atoms had energy below 1 eV, whereas film with hcp (100) orientation was obtained when most of them had energy above 1 eV. The distribution of the incident angles in SBD depended little on the sputtering gas pressure and had a similar distribution to that observed at a low gas pressure. The film deposited by SBD had much smoother surface than the film deposited by conventional magnetron sputtering.

Thin film TiC/TaC thermocouples

TiC and TaC thin films were investigated, for the first time, for thin film thermocouple applications. Thin films of TaC and TiC were deposited on electronic grade alumina substrates using the r.f. sputter deposition technique. Sheet resistance of the thin films was measured using a four point probe. It was observed that the sheet resistance of the films depends critically on the deposition parameters such as substrate temperature during deposition, sputter gas pressure and r.f. power used. The deposition parameters were optimized to yield the lowest sheet resistance of the thin films at room temperature. The thermoemf of the deposited films was measured as a function of temperature in a vacuum using a home made device. It was observed that thin films of TaC and TiC yield fairly high and stable thermoemf throug hout the temperature range of stability. Under the optimized deposition conditions, thin film thermocouples were fabricated. The thermocouples were calibrated against temperature and the output was measured in vacuum (pressure <10−6 Torr). TiC/TaC thermocouples yield stable output up to 1350 K, temperatures above which breakdown occurs. The thermocouple output was theoretically estimated from the thermoemf measured, and compared. It was observed that these thermocouples yield reproducible output in the temperature range of stability and hold excellent potential for high temperature thin film temperature sensor applications in vacuum or inert atmospheres.

Properties of aluminium oxide thin films deposited by reactive magnetron sputtering

Amorphous aluminium oxide thin films were deposited by reactive direct current circular magnetron sputtering. The deposition process was controlled by target voltage while the target power was adjusted to a preset value by oxygen gas flow rate. This technique allows the control over the film stoichiometry and reduces the target poisoning. A pulsed power supply was used to minimise the arcing. Oxygen was injected in the vicinity of the substrate to improve the oxidation of aluminium. The thin film properties were studied in terms of the process parameters such as target voltage, sputtering gas pressure and substrate bias voltage. The film properties studied in detail were the nanohardness, elastic modulus, film roughness, crystallographic structure, intrinsic stress, O/Al ratio, density and surface defects caused by arcing. Depending on the process parameters used, amorphous aluminium oxide thin films deposited on different substrates had nanohardness between 12.6 and 20.6 GPa, elastic modulus between 177 and 219 GPa, residual stress between −249 and 242 MPa, O/Al ratios between 1.30 and 1.72, and density between 2.32 and 3.77 g/cm3. The roughness of the aluminium oxide thin film on Si was between 0.72 and 2.64 nm.

スパッタエッチングによる紙の微細な粗面化とその光学的利用 （第２報） 黒染色紙における濃色化とその表面微細構造の関係

Color of paper was deepened by sputtering and its extent varied with the sputtering conditions, especially sputtering energy and gas pressure. The general relation with the gas pressure and sputtering energy was as follows : Sputtering at the gas pressure of 10 Pa showed a maximum color deepening L* of -3 at a sputtering energy of 20 J/cm2. Sputtering at the gas pressure of 100 Pa showed a maximum color deepening L*of -1 at a sputtering energy of 70 J/cm2. Sputtering at gas pressure between 0.2 and 1 Pa caused high rate of color deepening to L* of -3 at a sputtering energy of 20 J/cm2and the sputtering over 20 J/cm2 gave further increase in color depth.These complex changes in color deepening with sputtering energy and gas pressure were interpreted as the combination of color deepening and anti-color deepening occurring concurrently by the sputtering. The former was caused by the microstructure i.e. dense forests of cones or numerous microcraters and their pre-structures, and the latter was caused by thermal degradation of fiber and dye and by etching of fiber surface layer which had an abundance of color dye.

Deposition Kinetics and Microstructural Evolution in Sputtered TA Films: a Real-Time/In-Situ Study

ABSTRACTTa films were grown using sputter gas (Ar) pressures ranging from 1.7 to 20 mTorr. This produced growth environments where incoming adatom kinetic energies ranged from over 100 eV to less than 1 eV. Film development was monitored in-situ using a x-ray diffraction set-up that allowed complete diffraction patterns to be rapidly collected without interrupting the growth process. Traditional x-ray diffraction methods, transmission electron microscopy (TEM), and transmission electron diffraction (TED) were used to examine film microstructure after growth. It was found that lower Ar pressures, which allow higher adatom kinetic energies, produced films that displayed significant grain growth, texturing, and a smooth surface morphology. Those films grown at increasingly higher Ar pressures displayed smaller grain sizes, less texturing, and increasingly porous microstructures. To further explore this effect, the Ar pressure was varied during deposition for several films. The in-situ probe allowed the effects of each pressure increment to be analyzed and compared with previous x-ray and microscopy results. It was found that the microstructure of any particular film layer depended more on the deposition conditions during its formation rather than the structure or crystallography of previous layers.

Surface discharge characteristics of MgO thin films prepared by RF reactive magnetron sputtering

Abstract This paper describes the surface glow-discharge effect of MgO thin films prepared by reactive radio-frequency planar magnetron sputtering on the dielectric layer of an alternating-current plasma display panel. By introducing an MgO coating on the dielectric the discharge voltage decreases sharply, although the thickness is only a few tens of Angstroms. The lowest discharge voltage is obtained for the sample prepared at a 30% O2 content in an O2+Ar gas mixture and at a sputtering gas pressure of about 5 mTorr. Moreover, high transparency (∼95%) is also obtained under the same experimental conditions. The samples prepared show more sputter-resistant properties than samples prepared by the electron-beam method and no cracks are observed on the surface after post-deposition annealing.

Effect of Sm Concentration and Ar Sputtering Gas Pressure on Magnetic Properties of SmCo/Cr Films

Effect of Sm Concentration and Ar Sputtering Gas Pressure on Magnetic Properties of SmCo/Cr Films

Nano-size magnetic crystallite formation in Co-Cr thin films for perpendicular recording media

In order to understand the formation of nano-size magnetic domains in Co/sub 76/Cr/sub 24/ thin films for ultra-high density perpendicular magnetic recording, film thickness and sputtering gas pressures were investigated using a facing target sputtering (FTS) apparatus. Investigations of these films showed thy were composed of highly oriented hcp crystallites with lower Cr content (C/sub Cr/) of isolated ferromagnetic areas uniformly distributed in the higher C/sub Cr/ host paramagnetic matrix. The diameter of the lower C/sub Cr/ areas in these films was between 3-5 nm. The perpendicular coercivity in the surface region was greater than 2400 Oe. Consequently, this film is considered to be a good candidate for perpendicular magnetic recording densities approaching 1000 Kfci (10 Gb/in/sup 2/).

Mechanism of composition change in sputter deposition of barium ferrite films with sputtering gas pressure

In this study, we used computer simulation to investigate changes in the composition of hexagonal barium ferrite films with sputtering gas pressure obtained by the sputter-deposition processes. The iron content in the film deposited by facing target sputtering increased as the sputtering gas pressure increased and reached a maximum value at a certain gas pressure. These changes in the film composition were explained as follows: sputtered particles scatter when they collide with sputtering gas atoms, and this scattering changes the ratio of the particles reaching the substrate. When the substrate was located to the side of the target, as in a facing target sputtering system, this scattering resulted in an increase in the amount of sputtered particles arriving at the substrate, although too much scattering caused the amount to decrease. When a magnetron sputtering system is used for the film preparation, this gas scattering leads to a decrease in the amount of sputtered particles arriving at the substrate which is located opposite the target. Since this gas scattering depends significantly on the atomic mass of the sputtered particles, the gas pressure dependence of the amount of iron atoms arriving differs considerably from that of the amount of barium atoms arriving. This difference leads to the changes in film composition.