Film Deposition Parameters Research Articles

Domain structure of TbFe magnetostrictive films by MFM

TbFe thin films with giant magnetostriction were deposited by DC magnetron sputtering onto Si(100) substrate at different sputtering parameters, including substrate temperatures (Ts, 20-420/spl deg/C), sputtering power (35-100 W) and sputtering time (5-30 min). The samples were amorphous as characterized by XRD. Effect of sputtering parameters on domain structure, as explored by magnetic force microscopy (MFM), was focused. The films prepared under different sputtering parameters showed different domain patterns, such as maze or/and spotty (bubble) ones. The easy axis either in-plane or out-of-plane is affected by film-deposition parameters, specifically the film thickness. The wall energy (L/spl gamma/) increases with him thickness, leading to looser bubble domains while the magnetic anisotropy constant (K/sub u/) decreases with increasing substrate temperature.

Fluorinated amorphous carbon films for low permittivity interlevel dielectrics

The need to substitute SiO2 with low dielectric constant (κ) materials increases with each complementary metal–oxide–semiconductor process generation as interconnect RC delay, crosstalk, and power dissipation play an ever larger role in high-performance integrated circuits. Fluorinated amorphous carbon films (a-C:F,H) with low-κ properties (κ∼2.0–2.4) deposited by plasma-assisted chemical vapor deposition (CVD) techniques provide several advantages including low temperature processing, good gap fill capabilities, minimal moisture absorption, and simple implementation. Several deposition techniques have been examined, including high-density plasma and parallel-plate plasma-assisted CVD. In each case, it is possible to deposit a-C:F,H films with widely varying properties, such as κ and thermal stability. This has led to a good deal of confusion as to what is required to produce useful material. Results from many different sources are examined to develop a coherent picture of the relationships between deposition techniques, microstructural features, and macroscopic properties, and to summarize the scientific and technical challenges that remain for a-C:F,H implementation. The relationships between film deposition parameters such as applied substrate bias and film properties are presented in the discussion. In addition, x-ray photoelectron spectroscopy and network constraint theory are used to develop connections between microstructural and macroscopic properties, as well as to show how deposition parameters can be used to create a predictive model. This will demonstrate what process parameters are important in film formation. Finally, efforts to incorporate this material into integrated circuits, as well as measurements of the reliability and performance will be reviewed.

Optimization of hardness by the control of microwave power in TiN thin film deposited by electron cyclotron resonance assisted sputtering in a nitrogen plasma

Research has been conducted to investigate ways to make thinner, yet more cohesive TiN films. Plasma vapor deposition techniques were used in conjunction with electron cyclotron resonance to deposit TiN films on substrates of Inconel 718 (nickel-based superalloy). Previous parts of this investigation have focused on the relationship between process (i.e., film deposition) parameters, film microstructure, and film mechanical properties. The final part of this study extends the research focus to discuss what effect a change in the power setting of the microwave plasma has on the resulting Meyer hardness of the TiN-coated sample. The crystal orientation and texture of these films are also discussed. Optimum hardness of greater than 46 GPa was found at low microwave power of 200 W and a substrate bias of −100 V. Lowering microwave power to 200 W more than doubled the number of (111)-oriented grains. Substrate bias of −100 V or greater resulted in a greater than twofold decrease in (200)-oriented grains.

Characterization and enhanced properties of plasma immersion ion processed diamond-like carbon films

The formation and properties of diamond-like carbon (DLC) films prepared on silicon substrates at room temperature, using C2H2–Ar plasma immersion ion processing, are investigated with respect to film deposition parameters. Decreases in the reactive gas-flow ratios of C2H2 to Ar(FC2H2/FAr) or the gas pressure were found to decrease the hydrogen content, increase the density and hardness, and improve the surface finish of the DLC films, all of which led to enhanced tribological properties. Decreasing the friction coefficient requires increasing the hardness of the film and smoothing its surface, whereas increasing the wear resistance correlates with reducing both the hydrogen content and residual stress in DLC films. High hardness and optimum tribological properties were reached as the growth of DLC films was subjected to low-energy ion impingement, which was induced by a −150 V pulsed bias from the C2H2–Ar plasma produced at low reactive gas pressures with low FC2H2/FAr ratios.

Compositional and optoelectronic properties of CIS and CIGS thin films formed by electrodeposition

CuInSe 2 (CIS) and Cu(In,Ga)Se 2 (CIGS) thin films were prepared by electrodeposition and processing. The influence of film deposition parameters such as bath composition, pH, deposition potential and material purity on film properties was studied. The structural, morphological, compositional and opto-electronic properties of electrodeposited and selenized CIS and CIGS thin films were characterized using various techniques. As-deposited as well as selenized films exhibited a compact or a granular morphology depending on the composition. The film stoichiometry was improved after selenization at 550°C in a tubular furnace. The films are formed with a mixed phase composition of CuInSe 2 and CuIn 2Se 3.5 ternary phases.

Effect of deposition parameters on the CPP-GMR of NiMnSb-based spin-valve structures

We present measurements of current perpendicular magnetoresistance of NiMnSb/Cu/NiMnSb spin-valve structures based upon the predicted half-metallic (100% spin polarized) ferromagnetic alloy NiMnSb. The observed effect of 5–10% is much smaller than the complete spin-valve effect expected from a 100% spin-polarized system. The dependence of the magnetoresistance on film thickness and deposition parameters are explored to understand the factors limiting giant magnetoresistance in these structures.

Real-time monitoring of structure and stress evolution of boron films grown on Si(100) by ultrahigh vacuum chemical vapor deposition

The morphology and biaxial stress of amorphous boron films grown on silicon at 630 °C have been determined in situ and in real time using energy dispersive x-ray reflectivity and multiple-beam optical stress sensor techniques. The capability to determine the morphology and stress of light-element thin films in situ and in real time provides a unique opportunity to optimize the parameters of thin film deposition under chemical vapor deposition conditions.

Fast ICCD imaging of KrF excimer laser induced titanium plasma plumes for silicon metallization

Pulsed laser deposition (PLD) is applied to grow titanium thin films on silicon substrates for wafer metallization. Dynamics of plasma during the thin film deposition is investigated by fast intensified charge coupled detector (ICCD) time integrated photography. Plasma images at different gate delays after laser irradiation are taken to study plasma size, distribution, expansion and interaction with the substrates. Plume flying and expansion speeds in the directions normal and parallel to target surface are calculated. Fast ICCD imaging shows that the plasma starts to fly and expand at speeds as high as 10 6 cm/s and reduces gradually to zero with gate delay. The dependence of plume size and speeds on laser fluence, gate delay, target-to-substrate distance and chamber pressure is analyzed to optimize processing parameters for the thin film deposition.

Ba1−xSrxTiO3 Thin Film Sputter-Growth Processes and Electrical Property Relationships for High Frequency Devices

AbstractPrecise control of Ba1−xSrxTiO3 (BST) film composition is critical for the production of high-quality BST thin films. Specifically, it is known that nonstoichiometry greatly affects the electrical properties of BST film capacitors. We are investigating the compositionmicrostructure- electrical property relationships of polycrystalline BST films produced by magnetron sputter-deposition using a single target with a Ba/Sr ratio of 50/50 and a (Ba+Sr)/Ti ratio of 1.0. It was determined that the (Ba+Sr)/Ti ratios of these BST films could be adjusted from 0.73 to 0.98 by changing the total (Ar+O2) process pressure, while the O2/Ar ratio did not strongly affect the metal ion composition. The crystalline quality as well as the measured dielectric constant, dielectric tunability, and electrical breakdown voltage of BST films have been found to be strongly dependent on the composition of the BST films, especially the (Ba+Sr)/Ti ratio. We discuss the impact of BST film composition control, through film deposition and process parameters, on the electrical properties of BST capacitors for high frequency devices.

Postdeposition reduction of noble metal doped ZnO films

Insulating ZnO (wurtzite phase) films containing 1% to 2% Pt, Au, Pd, Ga, or Al dopants have been deposited onto silica, silicon, and aluminum substrates under oxidizing conditions. Substantial enhancement in film conductivity is promoted by postdeposition reduction in hydrogen above a critical temperature or by room temperature cathodic reduction in an electrochemical cell. Film reduction requires the presence of atomic hydrogen, formed at the film surface either by dissociative adsorption of gaseous H2 or its electrochemical generation from a buffered aqueous solution. As deposited and reduced films have been characterized using x-ray photoemission spectroscopy, Raman spectroscopy, optical transmission measurements, spectroscopic ellipsometry, voltammetry, chronopotentiometry, and four-point conductivity measurements. Results indicate that film deposition parameters and postdeposition reduction alter the oxidation states of both the zinc and the resident dopant cations. The zinc reduction reaction appears to be quasireversible while the reduced noble metal dopants in the films are not prone to reoxidation. These results may have implications for enhancing stability of the optical response and electrical conductivity exhibited by these films.

Influence of film deposition parameters on the field emission properties of diamond-like carbon films

Abstract Considerable interest exists in the use of carbon-based materials as the active phase in field emission devices for flat panel displays and vacuum electronics, in view of the observation that efficient field emission can take place in fields as low as 0.2 V μm−1. Diamond has often been the focus of study since the material is generally very well characterised. Diamond-like carbon (DLC) is, however, possibly a more interesting candidate for practical devices since it is cheaply produced over large areas. Variation in the nature of DLC films is much greater than is the case for diamond, and understanding how the field emission characteristics relate to the film properties is a key issue. In this work, we therefore investigate field emission from DLC films and study the relationship between emission properties and film deposition parameters. DLC films were deposited on p-type and n-type Si substrates from CH4/Ar and CH4/N2 plasmas created by a pulsed mid-frequency symmetrical discharge operated at a few Torr. Film thicknesses in the range of 0.05–1.5 μm were explored with optical band gaps ranging from 0.8 to 2.4 eV. The field emission properties of such films were found to vary markedly with the film characteristics, with turn-on fields as low as 1 V μm−1 being observed in some instances. The mechanisms that influence the field emission characteristics of the films are discussed.

Dc Magnetron Reactive Sputtering of Low Stress Ain Piezoelectric Thin Films for Mems Application

AbstractMany MEMS devices require piezoelectric excitation and readout to actuate and sense motion of mechanical structures. Aluminum nitride is advantageous for MEMS fabrication because it is compatible with silicon integrated circuit foundry impurity contamination requirements, can be deposited at low temperatures, provides a high piezoelectric coefficient, and is easily patterned using conventional photolithographic techniques. In this work, AIN thin films were deposited on silicon substrates for use in a MEMS silicon membrane ultrasonic resonator. The ultrasonic resonator is configured as a gravimetric sensing device for chemical detection. Issues of concern with regard to device performance and yield include the maximization of the electromechanical coupling constant (k2), film stress control, and film uniformity; these issues were addressed through a central composite design set of experiments to resolve the film property responses as a function of the deposition parameters. Film characterization was conducted with x-ray diffraction, spectroscopic ellipsometry, and surface profilometry. Optimization of film deposition parameters improved sensor performance and enabled further device miniaturization with the use of thinner films.

Spectroscopic characterization of processing-induced property changes in doped ZnO films

The optical response and electronic conductivity of neat and trivalent cation doped ZnO films are dependent upon film deposition parameters and subsequent post-deposition processing. As-deposited films which show high resistivity can be made conducting through gas phase reduction with hydrogen at elevated temperatures or by electrochemical reduction at room temperature using both aqueous and non-aqueous solvents. Resistive sputter and solution deposited films which exhibit c-axis or random crystallite orientation respectively, become conducting after these treatments and show increased infrared reflectivity owing to free carrier absorption. Raman measurements are used to confirm the wurtzite crystalline phase and dopant incorporation into the lattice. Optical properties of selected films are determined from transmission and spectroscopic ellipsometry measurements using models parameterized with previously determined microstructural information. Based upon the electrochemical results, a mechanism is proposed to describe the reduction process which requires the generation of atomic hydrogen as a reducing species.

Electrode supported solid oxide fuel cells: Electrolyte films prepared by DC magnetron sputtering

An electrode supported fuel cell concept with DC magnetron sputtered electrolyte films on the fuel electrode has been demonstrated. NiO/yttria-zirconia substrates with porosity up to 32% were used for depositing thin films (5–16 μm) of yttria stabilised zirconia (YSZ) electrolyte. By controlling film deposition parameters and surface porosity of the substrate, and by careful annealing of deposited films, highly dense and impervious films of YSZ have been produced. The annealed electrolyte films as well as cross-sections of half cells before and after reduction of NiO in hydrogen atmosphere have been carefully characterised by scanning electron microscopy. X-ray diffraction studies indicate the presence of a single cubic phase in the annealed film. The conductivity has been measured by impedance spectroscopy. Complete fuel cells have been prepared and evaluated in the temperature range of 700–800 °C. Their current-voltage characteristics have been determined with a current interruption technique. Early results on small cells have shown power densities in the vicinity of 600 mW cm −2 for air/H 2 (2–3% H 2O) at 800 °C, 440 mW cm −2 at 750 °C and 210 mW cm −2 at 700 °C. The preparation of dense and impervious electrolyte films on 50 mm × 50 mm anode supports has been successfully demonstrated.

Micromagnetic analysis of magnetization reversal in CoPt alloy films

We have studied the magnetization reversal processes in polycrystalline CoPt magneto-optic recording alloys with perpendicular magnetic anisotropy. Thin films of composition with total thicknesses in the range 5 nm to 30 nm were investigated with Kerr contrast imaging. Depending on the film deposition parameters we find domain wall motion or domain nucleation dominated processes. Numerical simulations of the magnetization reversal processes were carried out within a two-dimensional array model of interacting mesoscopic single domain particles. Including dipolar fields and domain wall contributions, we find that the demagnetizing fields dominate the reversal mechanisms and strongly affect the shape of the hysteresis loops. Additional microstructural analysis reveals that the typical grain sizes of the (111) textured polycrystalline alloy films are of the order of about 20 nm which coincides with the typical cell size representing a single domain particle in the micromagnetic numerical simulations.

Depth profiling of thin film heterostructure materials by secondary ion mass spectrometry

Thin film heterostructure ZnSe, GalnP, and SiGe/Fe have been depth profiled using secondary mass ion spectrometry with both a magnetic sector and a quadrupole mass filter. Semiconductors with wide direct bandgaps like ZnSe (2.67 eV) emit blue light, InGaP/GaAs can be used for lasers, and high speed Si 1− x Ge x Si heterojunction bipolar transistors (HBTs) could be used for many applications. Nevertheless, detailed understanding is needed of the relationships between film deposition parameters and the resulting physical and chemical properties of the semiconductors. This is primarily because the thin film heterostructures are, in most cases, poorly characterized. In this work, characterization of depth profiling using secondary mass ion spectrometry based on both magnetic sector and quadruple mass filters is critically evaluated. The advantages and disadvantages of each technique are discussed together with possible problems in data interpretation due to artifacts.

Optimization of Fabrication Parameters for Ge-Based Laminated Polarizer

Ge laminated polarizers (Ge-LAMIPOLs) consist of Ge/SiO2 multilayers which are designed to absorb the TE mode of the light wave at 850 nm wavelength. Such Ge-LAMIPOLs facilitate the miniaturization of optical components, but they usually break during the fabrication processes because of their low mechanical strength. This problem is solved by insertion of Si binding layers at Ge and SiO2 interfaces. Further improvement is also achieved by reduction of the internal stresses in SiO2 layers, using the hydrogenation technique. The optical properties of the Ge-LAMIPOLs can be optimized by adjustment of the film deposition parameters. As the result, 250-µm-thick Ge/Si-LAMIPOLs with 54.0 dB extinction ratio and 0.37 dB insertion loss are successfully fabricated.

Measurement of Residual Stress In TiO2 Sol-Gel Thin Films Using Raman Spectroscopy

AbstractThe deposition of thin films can result in residual stresses that affect film properties such as optical properties, phase stability, chemical durability, and film adhesion. There are many components to the total residual stress measured in a film. These include interfacial stress, volume changes associated with phase transitions, film thickness, and film microstructure. For sol-gel films, some contributors to residual stress can be controlled by such variables as the precursor chemistry and gelation time or heat-treatment following deposition. Measurements of the state of stress during crystallization or as a function of processing conditions and sol-gel chemistry allows optimization of film deposition parameters that promote minimal residual stress. We have constructed a three-dimensional surface in Raman shift-pressure-temperature space from spectroscopic measurements on single crystal anatase at high pressure and temperature. Location of the Raman shift of the two Eg modes of anatase on this surface the state of stress (pressure) and temperature of the film can be determined. For materials with large Raman scattering cross-sections, such as anatase, time-resolved crystallization experiments on films as thin as 100 nm are possible. Using this technique, the evolution of the state of stress during isothermal thermal and laser-induced crystallization processes can be monitored in real time and compared to the residual stress upon cooling.

Chemical vapour deposition and characterization of smooth {100}-faceted diamond films

Smooth {100}-faceted diamond films have been prepared by microwave-assisted chemical vapour deposition from CH 4H 2 mixtures. Growth has been controlled by in-situ laser interferometry. Under appropriate growth conditions, the films show a fibre texture with the 〈100〉 fibre axis normal to the substrate. The surface is completely formed by well-aligned coplanar {100} facets. The structure and morphology of these films have been characterized by X-ray diffraction, ion channelling and angle-resolved optical scattering measurements. Fibre textures with an angular spread of the 〈100〉 directions as narrow as 1° have been observed. The coplanar {100} facets form an optically smooth surface, exhibiting pronounced specular reflection. The dependence of the texture formation and surface morphology on film thickness and deposition parameters, including substrate temperature and gas composition, has been studied. For lower than optimum growth temperatures the surface becomes rough as {111} facets develop in addition to the (still coplanar) {100} facets. For higher than optimum growth temperatures the size of the {100} facets increases and the texture axis tilts away from 〈100〉. By varying the gas composition, any texture axis between 〈100〉 and 〈110〉 can be established. Computer based growth simulations have been performed on the basis of evolutionary selection of specific crystallite orientations. It is shown that a growth parameter α = 3 1 2 V 100 V 111 , i.e. the ratio of the growth rates on {100} and {111} faces, determines the structure and morphology of the films. A novel two-step growth process based on the control of α permits the independent optimization of texture axis and surface morphology, offering the possibility to obtain smooth faceted diamond films for arbitrary film thickness.

NRA and RBS analyses of silicon, aluminium and iron nitride thin films

Abstract Silicon nitride, aluminium nitride and iron nitride thin films grown by reactive sputtering on Si and polyimide substrates at various deposition conditions were analysed by nuclear reaction analysis ( 14 N(p , γ), 14 N(d, p) , 14 N(d , α), 14 N (α, α) and 27 Al(p , γ)) and Rutherford backscattering spectrometry. The results obtained with these analytical techniques were compared and correlations among film properties and deposition parameters were found.