Growth Rate Of Thin Films Research Articles

Epitaxial Mg 2SiO 4 thin films with a spinel structure grown on Si substrates

With a Mg target of purity of 99.95%, epitaxial Mg 2 SiO 4 thin films are grown on Si (1 0 0) substrates using RF magnetron sputtering at relatively high pressure (6–13 Pa) and high substrate temperature (700–780 °C). These Mg 2SiO 4 thin films are formed in a spinel structure with a lattice constant of 8.10 Å, and are cubic with four-fold symmetry. The spectra of X-ray photoelectronic spectroscopy (XPS) give a stoichiometric ratio of Mg : Si : O = 1.8 : 1 : 4 . The growth rate of thin film decreases as the growth time increases, the film thicknesses are 70 nm for a deposition time of 30 min, 120 nm for 1 h, and 160 nm for 2 h, respectively. Over an area of 5 μ m × 5 μ m , the root mean square (rms) roughness of Mg 2SiO 4 thin film is 11 nm. Such films can be of practical values in integrated circuits as buffer layers, etc. The details of the fabrication and characterization of these samples are discussed here.

Investigation of the effect of the total pressure and methane concentration on the growth rate and quality of diamond thin films grown by MPCVD

The influence of total gas pressure (50–125 Torr) and methane concentration (0.75%–10%) on diamond growth by microwave plasma chemical vapor deposition (MPCVD) was investigated. Within the regimes studied, the growth rate was proportional to the methane concentration in the source gas while it exhibited a super-linear dependence on total pressure. For a fixed methane concentration, characterization by Raman spectroscopy, scanning electron microscopy and X-ray diffraction indicated there was a minimum pressure required for the growth of large grain diamond, and conversely, for a fixed pressure, there was a maximum methane concentration that yielded diamond deposition. Higher pressures and higher carbon concentrations yielded diamond growth rates more than 10 times higher than achieved by the conventional low pressure MPCVD process.

Effects of substrate temperature on the microstructure and photoluminescence properties of ZnO thin films by atomic layer deposition

Atomic layer deposition (ALD) is a very promising deposition technique for ZnO thin films. However, there have been very few reports on ZnO grown by ALD. Effects of substrate temperature in both ALD and post annealing on the microstructure and PL properties of ZnO thin films were investigated using X-ray diffraction, photoluminescence, and scanning electron microscopy. The temperature window of ALD is found to be between <TEX>$130-180^{\circ}C$</TEX>. The growth rate of ZnO thin film increases as the substrate temperature increases in the temperature range except the temperature window. The crystal quality depends most strongly on the substrate temperature among all the growth parameters of ALD. The crystallinity of the film is improved by increasing the growth thine per ALD cycle or doing post-annealing treatment. The grain size of the film tends to increase and the grain shape tends to change from a worm-like longish shape to a round one as the annealing temperature increases from <TEX>$600^{\circ}C\;to\;1,000^{\circ}C$</TEX>.

High Growth Rate of Erbium Oxide Thin Films in Atomic Layer Deposition from (CpMe)3Er and Water Precursors

Organometallic tris(methylcyclopentadienyl)erbium and water were successfully exploited as precursors for the atomic layer deposition (ALD) of Er 2 O 3 thin films. Deposition studies were carried out in the temperature range 175-450 °C, where Si(100) and soda-lime glass were used as substrates. ALD-type growth mechanism could be verified at relatively low deposition temperatures of 250 °C and 300 °C, where a high growth rate (1.5 A per cycle) for an ALD process was obtained. The deposited Er 2 O 3 films were smooth and very uniform, and contained only low concentrations of carbon and hydrogen as impurities. The films were crystalline with the (111) orientation of the cubic phase dominating. The effective permittivity of the Er 2 O 3 /native SiO 2 insulator stack was approximately 10.

Modeling growth rate of HfO2 thin films grown by metal–organic molecular beam epitaxy

HfO2 dielectric layers were grown on the p-type Si (100) substrate by metal–organic molecular beam epitaxy (MOMBE). Hafnium-tetra-butoxide, Hf(O·t-C4H9)4 was used as a Hf precursor and Argon gas was used as a carrier gas. The thickness of the HfO2 film and intermediate SiO2 layer were measured by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The properties of the HfO2 layers were evaluated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high frequency (HF) capacitance–voltage (C–V) measurement, and current–voltage (I–V) measurement. C–V and I–V measurements have shown that HfO2 layer grown by MOMBE has a high dielectric constant (k) of 20–22 and a low-level of leakage current density. The growth rate is affected by various process variables such as substrate temperature, bubbler temperature, Ar and O2 gas flows and growth time. Since the ratio of O2 and Ar gas flows are closely correlated, the effect of variations in O2/Ar flow ratio on growth rate is also investigated using statistical modeling methodology.

Properties of CdS thin films grown by CBD as a function of thiourea concentration

Abstract This paper reports a study of the growth rate and optical properties of CdS thin films prepared by the chemical bath deposition technique. For the deposition an aqueous solution of cadmium chloride, ammonium chloride, ammonium hydroxide and thiourea were used, the films were deposited on conducting glass (SnO2: F). The growth kinetics is relatively fast when the quantity of thiourea is increased in the deposition solution and higher value of band gap is obtained ( E g = 2.44 eV ). The films show good transmittance in the visible region.

First-principles analysis of precursor-surface reaction pathways relevant to plasma deposition of silicon thin films

Passivation of silicon dangling bonds and abstraction of hydrogen by growth precursors are among the fundamental atomic-scale processes that determine the growth of hydrogenated amorphous silicon thin films during plasma-enhanced chemical vapor deposition from SiH/sub 4//H/sub 2/ containing discharges. Using results of first-principles density functional theory calculations, combined with images of planar intersections of the three-dimensional valence electron density distribution, we determine the optimized reaction pathways and energetics of dangling bond passivation and hydrogen abstraction reactions. Both reactions are found to be barrierless and exothermic in accordance with the experimentally observed temperature-independent growth rate of amorphous Si thin films.

Combined ab initio quantum chemistry and computational fluid dynamics calculations for prediction of gallium nitride growth

Computational fluid dynamics (CFD) is used in the semiconductor industry for the analysis and design of chemical vapor deposition reactors. One critical input needed for prediction of epitaxial thin film growth rates and uniformity is the chemistry occurring in the gas phase and at the surface. Traditionally, simplified chemistry derived from experimental observations has been used for this purpose. With the advent of modern high-speed computational techniques, it is now possible to formulate detailed reaction mechanisms using ab initio methods. Such detailed reaction mechanisms, comprising mostly of elementary reactions, have the advantage that they require little or no calibration. This paper presents a methodology in which the density functional theory, in combination with rate theories, was used to determine the reaction pathways and rates in the gas phase as well as at the surface for gallium nitride growth from tri-methyl gallium and ammonia. The reaction mechanisms were then used as input to a multi-dimensional CFD code enabling accurate prediction of growth rates. Validation studies were performed for four different laboratory-scale reactors, and one commercial reactor. In each case, the predictions agreed reasonably well with the experimental data indicating the universality of the reaction mechanisms.

Interelectrode space effect on power dissipation and silicon oxide thin film growth from TEOS/O2 discharges

The effect of the electrode gap on the electrical properties of TEOS/O2 discharges and on the growth rate of silicon oxide thin film was investigated. The experiments were performed using two excitation frequencies (13.56 MHz and 27.12 MHz) and at conditions that lead to deposition of films with a high inorganic character. Higher electrode gaps were always followed by an increase of the power consumption and the deposition rate. An additional enhancement was found with an increase of frequency from 13.56 to 27.12 MHz, indicating that a combination of high electrode gaps and frequencies are necessary for the fast deposition of inorganic SiO2 thin films from TEOS/O2 discharges.

Large Area Depositions of Si/SiC Quantum Well Films for Thermoelectric Generator Applications

ABSTRACTRecent development in thermoelectric conversion, especially in the area of quantum well (QW) thin film materials, have demonstrated the potential to achieve the high efficiency and power density to fabricate future power supplies. In this study, we develop the large area QW films of N-type Si/SiC integrated with P-type B4C/B9C, which can be used as thermoelectric devices for waste heat recovery. The approach is to fabricate thick large area film stacks (up to 11 μm) deposited by sputter deposition technique on 6” n-type (100) silicon substrates, which might be proven to be a suitable method for potentially manufacturing large area thermoelectric devices in a cost effective manner. These more basic studies are being carried out to better understand variables such as film thickness, deposition rate and other important parameters of these ∼10 nm films. The resulting as deposited and annealed multilayer stacks were characterized in terms of thin film uniformity, thickness, growth rate, composition, and thermoelectric performance, by Spectroreflectometry, atomic force microscopy (AFM), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), X-ray reflectivity (XRR), and electrical measurements. Issues, which could cause film stack degradation, such as interface layer formation, film delamination, and crack formation lowering the device performance will be presented and correlated to device efficiency.

Atmospheric pressure MOCVD of TiO 2 thin films using various reactive gas mixtures

TiO 2 thin films were deposited under atmospheric pressure by chemical vapor deposition using metal organic precursors (AP-MOCVD) in the temperature range 350–700 °C on Si(100) and stainless steel substrates. Titanium tetraisopropoxide (TTIP) was used as metal source. The influence on the growth process of an oxidant co-reagent (O 2 and H 2O) has been investigated. TTIP mole fraction and the substrate temperature are the major parameters which permit a good control of the morphology, the microstructure, the composition and the growth rate of these functional oxide thin films. Addition of O 2 in the input gas phase does not change significantly the main features of the layers. By contrast, TTIP/H 2O gas mixtures exhibit a higher reactivity leading to the deposition of TiO 2 at lower temperature and with a higher growth rate. For instance, the deposition rate at 450 °C is approximately 440 and 90 nm/min with and without H 2O vapor, respectively. Single-phased (anatase or rutile) and bi-phased coatings with a controlled composition can be deposited depending on the temperature and the TTIP mole fraction.

Preparation of Strontium Bismuth Tantalate Thin Film by Liquid-Delivery Metalorganic Chemical Vapor Deposition

ABSTRACTThin films of BiOX, SrXTaYO, and SrXBiYTaZO (SBT) were deposited by liquid-delivery metalorganic chemical vapor deposition (MOCVD). The substrate temperature and the deposition pressure were varied from 300 to 600°C and from 0.35 to 7 mbar, respectively. Triallylbismuth (Bi-1), triphenylbismuth (Bi-2) or alkyl bismuth (Bi-3) and strontium bis-pentaethoxy-methoxyethoxy tantalate (Sr-Ta) were used as Bi precursors and as Sr-Ta precursor, respectively. X-ray photoelectron spectroscopy (XPS), ellipsometry, and scanning electron microscopy (SEM) were carried out to characterize the film properties.The growth rates of the MOCVD of BiOX and SrXTaYO were compared to the growth rate of SBT to obtain information about mutual interaction between the precursors. The growth rate of bismuth oxide thin films deposited from Bi-1 and Bi-2 was low (∼10 nm/h at 0.35 mbar). The growth rate of strontium tantalate films was higher (up to 50 nm/h) and depended strongly on the temperature. Eight times higher (∼400 nm/h) growth rates of BiOX and SBT films were observed for the Bi-3 precursor. The deposition rate of the SBT films was quite similar to the rate of the bismuth oxide. However, the deposition rate of SBT was always lower than the deposition rate of the single Bi precursors. The growth rate significantly depended on the deposition pressure. A decrease of the deposition pressure in the reactor chamber reduced the deposition rate of BiOX, SrXTaYO, and SBT, but on the other hand, it improved the uniformity of the film thickness over the entire 150 mm wafer surface.The XPS measurements showed a deficit of bismuth in the SBT films even though the concentration of the Bi-1 or Bi-2 precursor was several times higher compared to the Sr-Ta precursor. This problem disappeared when Bi-3 source was used.

Atomic layer deposition of zirconium silicate films using zirconium tetrachloride and tetra-n-butyl orthosilicate

Atomic layer chemical vapor deposition of zirconium silicate films with a precursor combination of ZrCl4 and tetra-n-butyl orthosilicate (TBOS) was studied for high dielectric gate insulators. The effect of deposition conditions, such as deposition temperature, pulse time for purge and precursor injection on the deposition rate per cycle, and composition of the film were studied. At 400 °C, the growth rate saturated to 1.35 Å/cycle above 500 sccm of the argon purge flow rate. The growth rate, composition ratio ((Zr/Zr+Si)), and impurity contents (carbon and chlorine) saturated with the increase of the injection time of ZrCl4 and TBOS and decreased with the increased deposition temperature from 300 to 500 °C. The growth rate, composition ratio, carbon, and chlorine contents of the Zr silicate thin films deposited at 500 °C were 1.05 Å/cycle, 0.23, 1.1 at. %, and 2.1 at. %, respectively. It appeared that by using only zirconium chloride and silicon alkoxide sources, the content of carbon and chlorine impurities could not be lowered below 1%. It was also found that the incorporation rate of metal from halide source was lower than alkoxide source.

Study on the growth of CVD diamond thin films by in situ reflectivity measurement

Study on the growth of CVD diamond thin films by in situ reflectivity measurement was reported. SEM pictures show that the time dependent reflectivity is related to the evolution of the surface morphology. According to the principle of multiple beam interference, we present in this work a mathematical model to interpret laser reflectance interference on the surface of the growing diamond films. Using this model, a reflectivity curve was fitted. The optical refractive index, the surface roughness and the growth rate of the polycrystalline diamond thin films were determined from the fitted results in real time. Therefore, this is a useful method to study the growth of CVD diamond thin films.

YBa2Cu3O7 Thin Films Deposited by MOCVD Vertical Reactor with a Flow Guide

The effect of a flow guide in a vertical MOCVD reactor on the deposition uniformity and growth rate of thin YBCO films has been studied. Without the flow guide the growth rates are low, have a poor uniformity and the film composition is not stoichiometric. The growth rate of the films grown using a reactor with the flow guide was approximately twice that without the flow guide. Using this flow guide the growth rates were 0.4–0.7 μm/h for growth temperatures varying between 600 and 750 °C, and the crystalline quality as well as the surface morphology of YBCO films on MgO substrates is improved. For films grown at temperatures above 650 °C the composition of Y:Ba:Cu is 1:2:3, as confirmed by EDAX spectra. Films deposited without and with the flow guide at 700 °C have critical temperatures around 85 and 88 K, respectively. The reduction in ΔwTc (Tc,zero—Tc,onset) also shows an improvement of the superconducting properties of YBCO thin films deposited with a flow guide.

YBa2Cu3O7?? Thin Films Deposited by MOCVD Vertical Reactor with a Flow Guide

The effect of a flow guide in a vertical MOCVD reactor on the deposition uniformity and growth rate of thin YBCO films has been studied. Without the flow guide the growth rates are low, have a poor uniformity and the film composition is not stoichiometric. The growth rate of the films grown using a reactor with the flow guide was approximately twice that without the flow guide. Using this flow guide the growth rates were 0.4–0.7 μm/h for growth temperatures varying between 600 and 750 °C, and the crystalline quality as well as the surface morphology of YBCO films on MgO substrates is improved. For films grown at temperatures above 650 °C the composition of Y:Ba:Cu is 1:2:3, as confirmed by EDAX spectra. Films deposited without and with the flow guide at 700 °C have critical temperatures around 85 and 88 K, respectively. The reduction in ΔwTc (Tc,zero—Tc,onset) also shows an improvement of the superconducting properties of YBCO thin films deposited with a flow guide.

Crystal growth rate in ultrathin films of poly(ethylene oxide)

AbstractMany dynamical properties of polymers, including segmental relaxation and chain diffusion, exhibit anomalies in thin‐film samples. We extend the studies of thin‐film dynamics to the case of semicrystalline polymers and present a study of the crystal growth rate for thin films of poly(ethylene oxide). We used optical microscopy and quartz crystal microbalance techniques to characterize the kinetics of crystallization for films with thicknesses from 40 to 1000 nm for a range of temperatures near the melting point. A remarkable slowing down of the crystal growth is observed at all temperatures studied for films with a thickness of less than ∼100 nm. The results can be used to suggest reductions of the mobility of chains at the crystal/amorphous interface. © 2001 John Wiley &amp; Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2615–2621, 2001

Time-resolved plasma diagnostics for a better understanding of the improvement of pulsed MWPACVD of diamond

The deposition of diamond layers from CH4-H2 microwavedischarge operating in pulsed mode has been achieved. It has been shownthat the variation of the time parameters of the process (frequency andduty cycle) leads to noticeable modifications of the deposited layers.From plasma diagnostic measurements, the change in plasma composition hasbeen determined and correlated with the quality and growth rate of thediamond thin films. Particular attention has been paid to theconcentration of H-atoms, CH and C2 radicals and their evolution duringthe discharge regime and the afterglow. Indeed, these species are wellknown either as agents for graphite etching (H), or diamond precursors(CHx imaged by CH) or graphite precursors (C2Hx imaged by C2).Optimum values of the power pulse repetition rate (500 Hz) and duty cycle(50%) have been found which are correlated with the variation of therelative concentrations of H, CH and C2 with time, especially duringthe afterglow. It has been shown that these optimum conditions correspondto a minimization of C2 in the afterglow while H and CH concentrationsremain high enough to continue the diamond deposition process after thepower is switched off.

Plasma Diagnostics and the Evolution of a Novel Titanium Nitride Deposition Process

ABSTRACTMeasurement of the ion energy distributions (IED's) of N2+ ions produced in an inductively coupled plasma (ICP) source revealed that adding argon to the nitrogen gas before excitation in the source increased the nitrogen ion current. Adding helium resulted in an increase of the most probable ion energy, and a higher-energy component of the N2+ IED at about 20 eV. Preliminary calculations of the electron energy distributions (EED's) correlate well to the IED's for both inert gas additions. Experiments were performed to determine the effect of these modified energy distributions of the reactive species on titanium nitride thin film growth rates, microstructure and mechanical properties. Deposition experiments were conducted using the ICP source and an unbalanced magnetron with a titanium cathode. Results showed that the argon inert gas addition resulted in increased deposition rate and reduced 3-D features. Film roughness was decreased to 1.61 nm from 2.05 nm when helium was mixed with the nitrogen. Mixing both argon and helium with the nitrogen yielded combined effects of deposition rate increase, reduced 3-D features and increased smoothness. The inert gas additions increased hardness of the TiN films from 17.3 GPa to 21.1 GPa with the argon addition and to 25.0 GPa with the helium addition

PH Effect on the Deposition of CdS on ZnO and SnO2:F Substrates by CBD Method

CdS thin films were deposited on ZnO and SnO2:F substrates by the Chemical Bath Deposition (CBD) method, varying the solution's pH between 9 and 11. The samples were characterized through transmittance and AFM measurements. It was found that the transmittance and the morphological properties as well as the growth rate of the CdS thin films are significantly affected by the solutions' pH. Good results were obtained using pH values between 9 and 10.