Thin films of cobalt have been deposited by photo-assisted metal-organic chemical vapour deposition. Samples of thickness less than 60 nm, grown at 110 °C, exhibit inverse hysteresis when an external magnetic field is applied in a particular direction normal to the plane of the film. These films are a mixture of crystalline and, possibly, amorphous phases with a grain size of about 130 nm and a significant oxygen content throughout. The potential roles of the various physical characteristics, as well as that of the photolytic deposition process itself, in the origin of the inverse hysteresis are discussed, as is a possible self-limiting growth mechanism.

Advanced materials processing involves active control of fabrication and real-time monitoring of the final product. Sensors must be an integral part of the overall material processing system. ITN Energy Systems, Inc. and the Colorado School of Mines have developed a Parallel Detection, Spectroscopic Ellipsometer (PDSE) sensor for in-situ, real-time characterization and process control of multi-layered vapor deposited films. By measuring changes in the polarization state of reflecting light as a function of wavelength (250 to 5000 nm), the PDSE sensor determines the complex reflectance and/or the ellipsometric amplitude and phase. The PDSE provides cost-effective in-line sensing for film process control through detection of critical product variables that directly relate to film performance including: film thickness, optical excitation states, impurity concentrations, conductivity/resistance, intermixing at interfaces, microstructure, surface roughness, void fraction, defects, and grain size. The PDSE sensor is an optical probe with no moving parts that can measure the optical properties of thin films in as little as 3 msec with sensitivity to films less than a monolayer in thickness. We will use this PDSE system to provide real time process control of vapor deposited CuInGaSe2 (CIGS) films on a continuous flexible substrate. Initial results from CIGS films indicate that the PDSE has the sensitivity and accuracy to provide intelligent process control. The remaining challenge is to develop interpretive algorithms; the amount and quality of information required will determine their complexity. In addition, with the inception of in-situ, real-time monitoring, we hope to enable minimal data analysis approaches1 that provide extremely useful information with minimum interpretive algorithm development.

Long term control of the substrate temperature in production scale MOVPE reactors is the most significant issue effecting yields in highly temperature sensitive epitaxial growth processes. Recent advances in non-contact emissivity compensated pyrometry wafer temperature measurements have allowed the development of a novel multi-wafer (6×2”) rotating disc MOVPE reactor with real time substrate temperature control. With this system, the substrate temperature is a directly controlled process variable, in contrast to some conventional MOVPE systems which use thermocouples for process temperature control. In addition to controlling the absolute temperature of the substrates, the temperature uniformity across the substrates is also controlled by pyrometry. This provides for a uniform temperature (+/- 1.5 °C) across the substrates independent of the flow conditions within the reactor. Thermal uniformity is also automatically maintained during temperature ramping. The highly temperature sensitive quaternary InGaAsP is used as an epitaxial metric for this novel control system, to demonstrate the advantages of pyrometry controlled substrate temperature. These advantages include: excellent long term substrate temperature reproducibility; invariance of substrate temperature to substrate doping level; the ability to transfer processes from one type of wafer carrier or reactor to another with minimal adjustment.

Two major problems associated with Si-based MEMS devices are stiction and wear. Surface modifications are needed to reduce both adhesion and friction in micromechanical structures to solve these problems. In this paper, we will present a process used to selectively coat MEMS devices with tungsten using a CVD (Chemical Vapor Deposition) process. The selective W deposition process results in a very conformal coating and can potentially solve both stiction and wear problems confronting MEMS processing. The selective deposition of tungsten is accomplished through silicon reduction of WF6, which results in a self-limiting reaction. The selective deposition of W only on polysilicon surfaces prevents electrical shorts. Further, the self-limiting nature of this selective W deposition process ensures the consistency necessary for process control. Selective tungsten is deposited after the removal of the sacrificial oxides to minimize process integration problems. This tungsten coating adheres well and is hard and conducting, requirements for device performance. Furthermore, since the deposited tungsten infiltrates under adhered silicon parts and the volume of W deposited is less than the amount of Si consumed, it appears to be possible to release stuck parts that are contacted over small areas such as dimples. Results from tungsten deposition on MEMS structures with dimples will be presented. The effect of wet and vapor phase cleans prior to the deposition will be discussed along with other process details. The W coating improved wear by orders of magnitude compared to uncoated parts. Tungsten CVD is used in the integrated-circuit industry, which makes this approach manufacturable.

Scanning probe microscopy has yielded extraordinary advances in our ability to characterize surfaces at the atomic scale. These advances are paralleled by improvements in computational methods and platforms that now yield realistically complex multi-scale models of deposition processes. Combining these developments, it might now be possible to sense the dynamic state of an atomic surface, consulting with models to analyze the path of a deposition process. This real-time information might allow us to tweak the growing materials towards particularly unique and desirable final configurations. What we are largely missing are sensors that can monitor atomic scale evolution without, themselves, compromising the commercial deposition process. In a manufacturing environment, sensors cannot shadow the deposition process or contaminate the material. They cannot add significantly to the complexity of the deposition tool nor require that tool's extensive redesign. Importantly (at least over the long term) the sensors cannot even require us, that is, highly trained (and paid) individuals to operate and interpret their data!

The vapor-phase synthesis of polycrystalline ZnSe nanoparticles is reported. The particles were grown at room temperature and at a pressure of 125 torr in a counterflow jet reactor and were collected by impact on a Si watler. The precursors used in this study were vapors of (CH3)2Zn:[N(C2H5)3)]2 and H2Se gas diluted in hydrogen. These precursors have been used in the past for Metalorganic Vapor Phase Epitaxy (MOVPE) of ZnSe thin films. The particles were characterized by Transmission Electron Microscopy (TEM). electron diffraction. and Raman spectroscopy. The reactor was operated in a continuous, steady-state mode using a gas delivery system that is typical flor MOVPII systems.

Fluctuation microscopy experiments have shown that the as-deposited structure of amorphous silicon thin films is paracrystalline. A paracrystal consists of small (< 3 nm in diameter) topologically crystalline grains separated by a disordered matrix. Here we consider the thermodynamics of paracrystalline silicon as a function of the grain size and the temperature. We offer a simple model that qualitatively explains the observed metastability of the ordered structure at low temperature (300 K), the relaxation towards a more disordered structure at intermediate temperatures (600 K), and the recrystallization at high temperatures (1000 K).

Thin films of titania have been grown by photo-assisted MOCVD which are amorphous and relatively strain free, with high refractive index, low optical loss and structural features all less than 100 nm in size. The stoichiometry is very close to TiO2 and the impurity content is negligible except for a small amount of calcium, thought to have been leached from the glass substrate. The optimum deposition conditions were found to involve a deposition temperature of around 200 °C, a cell pressure of 5.6 torr and the introduction of nitrous oxide, decomposed by UV irradiation to give oxygen free radicals which acted as an oxidant.

Many experimental results were reported of CVD diamond synthesis with so called flow systems, which need introduction of source gas and evacuation of reactant gas. For few years, we had been concentrated of development completely closed diamond synthesizing system aimed for microgravity experiments. Recently we started the new method with graphite as a carbon source. With this method, completely closed system is successfully performed. Graphite rods are used as solid carbon source and at the same time as thermal energy source. Silicon (100) wafer was used for substrates. Hydrogen gas was introduced into the reaction chamber with the suitable initial pressure. and controlled with Joule heating. The deposits were identified with SEM and Raman spectrometry. We tried to synthesize diamond on Si substrate under the conditions of forward bias where the substrate is held at a positive potential relative to the graphite rod. And also we tried the experiment under the reverse bias.

In this paper we describe the response of a Kinetic Monte Carlo model to time-varying growth conditions. We vary temperature and partial pressure sinusoidally and identify behavior typical of low-dimensional nonlinear systems. In particular, the frequency content of the roughness response is sensitive to the presence of steps in the surface.

TiO2 thin films were deposited by metal-organic chemical vapor deposition (MOCVD) method using titanium tetraisopropoxide(TTIP). A drastic change in structural aspect and its property occurred when the deposition temperature increased above 400°C. Deposition kinetics was proved to transit from reaction controlled regime into diffusion controlled regime above about 400°C in Arrehnius plot. In X-ray diffraction (XRD)and infrared reflectance spectra, it was observed that the crystallinity was decreased significantly around 400°C. The surface microstructure has changed explicitly from dense structure with larger grains to porous one with smaller grains observed by scanning electron microscopy and transmission electron microscopy. Electrical resistance of the films jumped by 2 orders of magnitude, which is measured by the 4-point probe method. The refractive index calculated by Swanepoel's method has decreased from 2.45 to 2.28 at 630nm. The porous microstructure of films deposited at above 400°C was thought to be responsible for the significant decrease in electrical conductivity and refractive index of the films.

There is a great deal of interest in thin film deposition techniques which can achieve good crystal quality at low substrate temperatures. Pulsed laser deposition (PLD), well-known as a reliable technique for fabrication of high critical temperature superconductor thin films, has a number of characteristics which may make it suitable for such applications. In particular, PLD is characterized by a relatively large average species energy, which can be controlled by the laser fluence at the target. This paper describes the growth of silicon on silicon films using PLD over substrate temperatures between 500 and 700 °C, and in-situ characterization using reflection high-energy electron diffraction (RHEED). Transmission electron microscopy confirms the growth of single crystal oriented films, and atomic force microscopy indicates smooth films with an rms surface roughness of less than 2 Å

For purpose of enhancement of mechanical properties, Al/Al2O3 films, with thickness A in the nanometric scale, were deposited on silicon substrate by reactive rf sputtering, at substrate temperatures Ts ranging from −90°C to 600°C. The characterisation (FEG-SEM, AFM, SIMS, XRR) has shown that Al/Al2O3 films are granular and rough, in correlation with the behavior of single alumnium films. The minimal roughness values are obtained at low Ts (−90°C and 25°C). The Λ = 20 rim-films are real multilayers, as confirmed by SIMS and XRR. Nevertheless, the multilayering character, i.e. the existence of multilayers, decreases when Ts increases. At low Ts, the relevant parameter to explain the weakness of stratification of Al/Al2O3 films is the roughness of layers, while at high Ts, the chemical interdiffusion clearly dominates, resulting in a no periodic structure at Ts = 600°C.

Erbium hydride thin films are grown onto polished, a-axis α Al2O3 (sapphire) substrates by reactive ion beam sputtering and analyzed to determine composition, phase and microstructure. Erbium is sputtered while maintaining a H2 partial pressure of 1.4 ×10−4 Torr. Growth is conducted at several substrate temperatures between 30 and 500°C. Rutherford backscattering spectrometry (RBS) and elastic recoil detection analyses after deposition show that the H/Er areal density ratio is approximately 3:1 for growth temperatures of 30, 150 and 275°C, while for growth above ∼430 °C, the ratio of hydrogen to metal is closer to 2:1. However, x-ray diffraction shows that all films have a cubic metal sublattice structure corresponding to that of ErH2. RBS and Auger electron spectroscopy confirm that sputtered erbium hydride thin films are relatively free of impurities.

Thin films can be deposited with atomic layer control using sequential surface reactions. The atomic layer deposition (ALD) of compound and single-element films can be accomplished using the appropriate surface chemistry. This paper reviews the ALD of dielectric alumina (Al2O3) films and conducting tungsten (W) films. The Al2O3 films are deposited on submicron BN particles and the surface chemistry is monitored using Fourier transform infrared (FTIR) spectroscopy. Additional transmission electron microscopy (TEM) studies investigated the conformality of the Al2O3 growth on the BN particles. FTIR investigations of the surface chemistry during W ALD are performed on nanometer-sized Si02 particles. Additional in situ spectroscopy ellipsometry studies of W ALD on Si(100) established the W ALD growth rates. Al2O3 and W ALD both illustrate the potential of ALD to obtain conformal and atomic layer controlled thin film growth using sequential surface reactions.

New magnetic field sensors and non-volatile magnetic random access memories can be built from giant magnetoresistive multilayers with nanoscale thickness. The performance of these devices is enhanced by decreasing the atomic scale interfacial roughness and interlayer mixing of the multilayers. During ion beam sputtering, inert gas neutrals with energies between 50 and 200 eV impact the growth surface. A molecular dynamics method has been used to study the effects of these impacts on the surface roughness and interlayer mixing of model nickel/copper multilayers. The results indicate that impacts with energy above 50 eV cause mixing due to the exchange of Ni atoms with Cu atoms in an underlying Cu crystal. The extent of the mixing increases with impact energy, but decreases as the number of the Ni monolayers above the Cu crystal increases. While Xe and Ar impacts have a similar mixing effect at low energies, heavier Xe ions/neutrals induce more significant mixing at high energies.

We have implemented coherent gradient sensing (CGS) to measure in situ, curvature and changes in curvature induced by temperature and O2 flow on thin film YBCO on MgO (001) substrates. CGS is a novel, real-time, full-field optical technique that provides a direct map of the components of the curvature tensor across the entire surface of the wafer. We have examined a well-characterized,700 nm thick YBCO film on a square 1”× 0.5mm MgO substrate with increasing temperature from 25 to 760°C and find the curvature increasing with temperature, although not always spatially uniform. By Stoney's equation, we relate the observed curvature to the thermal mismatch of the film and substrate where the maximum observed stress in orthogonal sample orientations is 1.2 and 1.4 GPa. For wafers under varying oxygen partial pressures, we observe dramatic local changes in the CGS interferograms, which we relate to the tetragonal to orthorhombic phase transformation YBCO exhibits as it cools in oxygen.

Using an optical reflectivity difference technique, we monitored the growth of multilayer Xe films on a commensurate monolayer of Xe on Ni(111), from 35 to 60K. A transition occurs near 40K, from rough growth at low temperature to quasi-layer-by-layer growth characterized by persistent oscillations in the reflectivity difference. We discuss this transition in terms of changes in the island formation process and the onset of second layer nucleation. The Xe sticking coefficient at 40K is obtained from the period of the oscillations in the reflectivity difference. We find that the sticking coefficient decreases with increasing fihn thickness at fixed Xe pressure.

CVD diamond is an enabling material for diverse applications. In recent years, multiscale modelling of CVD growth in conjunction with experimental studies of the deposition processes has made a substantial progress towards our understanding of the fundamental growth chemistry and material quality. Macroscopic gas phase simulations of the CVD reactor, the mesoscale kinetic Monte-Carlo (KMC) modelling of the crystal growth and nanoscale modelling of the surface chemistry are three main legs in the multiscale hierarchy. In the framework of this methodology we have performed first-principles quantum mechanical calculations of bonding and reaction kinetics of the elementary growth processes and provided critical input in the form of atomistic growth mechanisms and reaction rates for the mesoscale KMC modelling of CVD diamond growth. A key success was achieved by combining first-principles and Monte Carlo studies to elucidate (100) growth mechanisms that have perplexed the diamond growth community for many years.

We investigate the morphology of films produced by cluster deposition using Monte Carlo atomistic simulations. Thin films of aluminum are considered as an example. The deposition of small Al clusters containing up to 5 atoms is simulated. Compared with monomer beams, Al cluster deposition increases the density of 3D islands nucleated on the substrate and tends to equalize the growth rate of the different crystal facets. We discuss the smoothening of the surface when the 3D islands merge. We find that there is an optimal size of the deposited clusters that produces the smoothest film.