Thin Film Deposition Process Research Articles

Density functional theory study on the full ALD process of silicon nitride thin film deposition via BDEAS or BTBAS and NH3.

A detailed reaction mechanism has been proposed for the full ALD cycle of Si3N4 deposition on the β-Si3N4(0001) surface using bis(diethylamino)silane (BDEAS) or bis(tertiarybutylamino)silane (BTBAS) as a Si precursor with NH3 acting as the nitrogen source. Potential energy landscapes were derived for all elementary steps in the proposed reaction network using a periodic slab surface model in the density functional approximation. Although the dissociative reactivity of BTBAS was slightly better than that of BDEAS, the thermal deposition process was still found to be an inherently high temperature process due to the high activation energies during the dissociative chemisorption of both precursors and the surface re-amination steps. These results underline the need to develop new precursors and alternative nitrogen sources when low temperature thermal silicon nitride films are targeted.

모듈레이티드 펄스 스퍼터링으로 상온 증착한 Indium-Tin-Oxide (ITO) 나노 박막

High power impulse magnetron sputtering (HIPIMS), also known as the technology is called peak power density in a short period, you can get high, so high ionization sputtering rate can make. Higher ionization of sputtered species to a variety of coating materials conventional in the field of improving the characteristics and self-assisted ion thin film deposition process, which contributes to a superior being. HIPIMS at the same power, but the deposition speed is slow in comparison with DC disadvantages. Since recently as a replacement for HIPIMS modulated pulse power (MPP) has been developed. This ionization rate of the sputtered species can increase the deposition rate is lowered and at the same time to overcome the problems to be reported. The differences between the MPP and the HIPIMS is a simple single pulse with a HIPIMS whereas, MPP is 3 ms in pulse length is adjustable, with the full set of multi-pulses within the pulse period and the pulse is applied can be micro advantages. In this experiment, <TEX>$In_2O_3$</TEX> : <TEX>$SnO_2$</TEX> composition ratio of 9 : 1 wt% target was used, Ar : <TEX>$O_2$</TEX> flow rate ratio is 4.8 to 13.0% of the rate of deposition was carried out at room temperature. Ar 40 sccm and the flow rate of <TEX>$O_2$</TEX> and then fixed 2 ~ 6 sccm was compared against that. The thickness of the thin film deposition is fixed at 60 nm, when the partial pressure of oxygen at 9.1%, the specific resistance value of <TEX>$4.565{\times}10^{-4}{\Omega}cm$</TEX>, transmittance 86.6%, mobility <TEX>$32.29cm^2/Vs$</TEX> to obtain the value.

Kinetic Monte Carlo simulation of low-pressure chemical vapor deposition of silicon nitride: Impact of gas flow rate and temperature on silicon cluster size and density

In the present study, the deposition process of SiNx thin films obtained by a low-pressure chemical vapor deposition technique with a mixture of disilane (Si2H6) and ammonia (NH3) was simulated by using the kinetic Monte Carlo method. A new pattern describing the distribution of ammonia molecules in the simulation matrix was proposed. The influences of the NH3/Si2H6 gas flow ratio and the deposition temperature on the obtained films structure in terms of silicon cluster size and density were analyzed. The simulation results indicate that an increase in the gas flow ratio leads to the deposition of amorphous silicon clusters characterized by small sizes. Nevertheless, an increase in the temperature values of the process provokes an enhancement in the silicon cluster size along with a decrease in their density.

Comparative and integrative study of Langmuir probe and optical emission spectroscopy in a variable magnetic field electron cyclotron resonance chemical vapor deposition process used for depositing hydrogenated amorphous silicon thin films

An electron cyclotron resonance chemical vapor deposition (ECR-CVD) system applied in a hydrogenated amorphous silicon (a-Si:H) thin-film deposition process was diagnosed in-situ by using optical emission spectroscopy (OES) and a Langmuir probe. The optical actinometry technique was used to obtain the ratio of species concentration to the concentration of a trace gas (Ar). The electron temperature (Teoes) was estimated according to the spectrum intensity ratio of Hβ to Hα or that of Si* to SiH*, and the two estimation approaches were evaluated by comparing the results (TeLP) of Langmuir probe measurement. The probe surface contaminants (a-Si:H) produced during in-situ measurement created errors in the measurement of parameters such as the electron temperature and density (Ne). The results indicated that, when a-Si:H was coated on the probe at thicknesses less than 150nm, the errors were negligible. OES and Langmuir probe measurement were integrated and used to determine the dependence of the processing pressure and resonance magnetic field configuration on the properties of an a-Si:H film grown using ECR-CVD. When the process pressure was increased, the Ne, Teoes and TeLP decreased; moreover, the Fourier-transform infrared spectroscopy results indicated that structure factor (R*) increased, and both the photosensitivity and hydrogen content (CH) decreased. An analysis conducted using OES and Langmuir probe measurement revealed, that the decreased concentration of the H radical reduced the passivation effect, and surface diffusion decreased. Furthermore, the gas partial pressure exerted a substantial influence on OES measurement. The volatility of the Ar spectrum intensity equaled the product of the volatility of Ne and TeLP when the partial pressure effect is eliminated. Regarding the resonance magnetic field, the effects of plasma resonance position on film characteristics were substantial. The Ne decreased greatly when the distance between quartz and the resonance zone was increased.

Uncertainty analysis and robust optimization of multiscale process systems with application to epitaxial thin film growth

Multiscale modeling of materials growth involves inherently coupled processes that span over a wide range of time and length scales. As a common practice, a multiscale model is adopted to simulate the thin film deposition process that augments Partial Differential Equations (PDEs), describing the macro-scale phenomena, with a high-order lattice-based kinetic Monte Carlo (KMC) simulator, which aims to capture thin film microstructure. Although such a model is a fair representation of the system, the evolution of thin film encompasses processes that are subject to model parameter uncertainty that can significantly affect the control and optimization objectives of this process, e.g. film׳s roughness and thickness. Thus, to provide a robust and more realistic strategy, it is crucial to perform an uncertainty analysis for this process. This work explores a systematic framework to analyze model parameter uncertainty for robust control and optimization of multiscale models. Such an analysis is extremely challenging due to (i) the lack of a closed formulation between the process optimization objective (i.e. film thickness) and the model parameters and (ii) the computational costs incurred to model the fine-scale events, typically performed using KMC simulation. To tackle these challenges, Power Series Expansion (PSE) is employed to analyze model uncertainty propagation. The PSE-based method for uncertainty analysis is more computationally efficient in comparison to the traditional Monte Carlo approach. The distributional uncertainty in rates of microscopic events is characterized by series expansions of the uncertain parameters. The fitted distributions to the rate of events at a given confidence level are employed to estimate upper and lower bounds on the desired outputs (e.g. film roughness). The computational efficiency of the approach is achieved by employing multiple reduced-order lattices in the KMC simulator. The potential application of the proposed method is illustrated through an optimization problem that aims to specify the robust optimal substrate temperature profile that maximizes the endpoint thin film thickness in the presence of uncertainty.

A fast method for the calculation of electron number density and temperature in laser-induced breakdown spectroscopy plasmas using artificial neural networks

A fast and precise method for the determination of electron temperature and electron number density in laser-induced plasmas is presented. The method is based on the use of a simple artificial neural network (ANN), trained on a suitable set of laser-induced breakdown spectroscopy spectra. The training procedure is quite fast; once the ANN is set, the determination of plasma temperature and electron number density is almost instantaneous, allowing the possibility of measuring these parameters, with good precision, in real time. A direct application of this new method could be the characterization of plasmas generated during pulsed laser deposition process of thin films and nanoparticles generation. The plasma electronic parameters will help to tune the energies involved in the stoichiometry and crystallization control of those nanostructured materials. As an example, the characteristics of the plasma induced by a Nd:YAG laser on a pure titanium target are determined, at different laser fluences.

Preparation and characteristics of vanadium oxide thin films by controlling the sputtering voltage

Influence of sputtering voltage on the deposition process and characteristics of vanadium oxide thin films prepared by reactive DC magnetron sputtering is investigated. The target surface cleaning is controlled by adjusting the sputtering voltage. During the sputtering process, the sputtering voltage increases faster with larger O2 gas flow rate. The sputtering voltage is easy to be stable with larger sputtering voltage. The measured sputtering voltage is correlated to the ion induced secondary electron emission (ISEE) coefficient of the target material. The ISEE coefficient of the oxidized vanadium target surface is lower than the ISEE coefficient of the vanadium metal. The semiconductor to metal (S–M) phase transition temperature decreases with the sputtering voltage, leading to the lower the corresponding temperature of the maximum temperature coefficient of resistance (TCR). By this way, O/V ratio, R, and TCR of VOx films can be controlled by adjusting the sputtering voltage.

Broadband antireflection and light extraction enhancement in fluorescent SiC with nanodome structures.

We demonstrate a time-efficient and low-cost approach to fabricate Si3N4 coated nanodome structures in fluorescent SiC. Nanosphere lithography is used as the nanopatterning method and SiC nanodome structures with Si3N4 coating are formed via dry etching and thin film deposition process. By using this method, a significant broadband surface antireflection and a considerable omnidirectional luminescence enhancement are obtained. The experimental observations are then supported by numerical simulations. It is believed that our fabrication method will be well suitable for large-scale production in the future.

Low-Pressure Plasma Reactor with a Cylindrical Electrode for Eco-friendly Processing in the Semiconductor Industry

Thin film deposition processes emit large amounts of NF3 and by-product particles, which are of great concerns in the semiconductor industry, from the environmental and economic points of view. With an objective to overcome these concerns, plasmas are generated from a cylindrical reactor placed before a vacuum pump. The discharge stability is evaluated by monitoring the changes in the plasma images with the pressure. By using a particle sampler and a particle trap, the size and quantity of the by-product particles are compared during plasma-on and plasma-off. The effects of adding O2 and H2O to the by-products of the NF3 abatement process are investigated by analyzing the spectra obtained with a Fourier transform infrared spectroscopy. Further, the H2O flow rate is optimized for the highest destruction and removal efficiency of NF3. Finally, the applicability of our device to the after-treatment equipment is discussed.

Protective multilayer packaging for long-term implantable medical devices

State of the art packaging for implantable devices uses metal or glass housings that are reliable but limited from a miniaturisation viewpoint as well as cost-intensive. We suggest a hermetic and biocompatible thin film packaging based on alternating organic/inorganic coatings for further miniaturisation of smart implantable MEMS devices that can be applied for long-term implantation. The combination of high intrinsic molecular density silicon oxide (SiOx) and pinhole-free and stress releasing poly-para-xylylene (parylene-C) thin films creates a new composite material, which is optimal for hermetic and biocompatible packaging. A novel single-chamber thin film deposition process was developed for the fabrication of SiOx/parylene thin film multilayer structures, using a modified chemical vapour deposition (CVD) process. According to permeation and conformity aspects, the inorganic layer is the crucial layer of the coating. Permeation measurements the highly ceramic SiOx material revealed a low helium gas permeation and a non-critical cracking thickness up to 300nm. The morphology of the multilayer structure was analysed by scanning electron microscopy; an algorithm for defining ideal layer conformity was established and no local thickness deficiencies of deposited SiOx layers could be observed. To evaluate the corrosion protection, an adapted calcium mirror test based on water droplet permeation was developed, and the water permeation of conventional parylene-C layers (4.5μm) was compared to multilayer stacks composed of 3 SiOx interlayers (4.7μm).In this paper, it could be shown that by tailoring the thickness ratio between the involved layers, the percolative pathway and thereby, the permeation for direct water exposure could be considerably reduced compared to conventional parylene-C single layers with the same thickness.

Self-assembling and self-limiting monolayer deposition

Effects of spatial ordering of molecules on surfaces are commonly utilized to deposit ultra-thin films with a thickness of a few nm. In this review paper, several methods are discussed, that are distinguished from other thin film deposition processes by exactly these effects that lead to self-assembling and self-limiting layer growth and eventually to coatings with unique and fascinating properties and applications in micro-electronics, optics, chemistry, or biology. Traditional methods for the formation of self-assembled films of ordered organic molecules, such as the Langmuir-Blodgett technique along with thermal atomic layer deposition (ALD) of inorganic molecules are evaluated. The overview is complemented by more recent developments for the deposition of organic or hybrid films by molecular layer deposition. Particular attention is given to plasma assisted techniques, either as a preparative, supplementary step or as inherent part of the deposition as in plasma enhanced ALD or plasma assisted, repeated grafting deposition. The different methods are compared and their film formation mechanisms along with their advantages are presented from the perspective of a plasma scientist. The paper contains lists of established film compounds and a collection of the relevant literature is provided for further reading.

Optical Society of America’s 2013 Topical Meeting on Optical Interference Coatings: Introduction by the Feature Editors

This Applied Optics feature issue is dedicated to the 12th topical meeting on Optical Interference Coatings held on 16–21 June 2013 in Whistler, British Columbia, Canada. The conference, taking place in a three-year rotation with conferences in Europe and Asia, is a focal point for global technical interchange in the field of optical interference coatings and provides premier opportunities for people in the field to present their new advances in research and development. Papers presented at the conference cover a broad range of topics, from thin film deposition processes, designs and modeling, materials, and metrologies to a wide array of thin film applications.

In situXRD investigation of Cu2ZnSnSe4thin film growth by thermal co-evaporation

The deposition of a Cu2ZnSnSe4 (CZTSe) thin film with a multi-stage co-evaporation process is investigated with time-resolved in situ X-ray diffraction (in situ XRD). For the experiment a novel setup intended for in situ analysis of thin film deposition processes was used. The in situ data confirm the former observation that CZTSe growth is delayed with deposition of only Cu2−xSe and ZnSe in the initial process stage and provide new insight into the evolution of the appearing phases. In Zn-rich deposition conditions, ZnSe deposited at the beginning may not be consumed by the growing CZTSe but remain as an unreacted layer at the interface to the Mo back contact. Cu2−xSe growth starts with the formation of a Cu rich phase, which is reduced to a Cu poor phase in the process. Furthermore, our results show that in situ XRD at elevated temperatures is able to distinguish between ZnSe and CZTSe and that it can be used for the detection of ZnSe as secondary phase.

Fabrication of CIS Absorber Layers with Different Thicknesses Using A Non-Vacuum Spray Coating Method.

In this study, a new thin-film deposition process, spray coating method (SPM), was investigated to deposit the high-densified CuInSe2 absorber layers. The spray coating method developed in this study was a non-vacuum process, based on dispersed nano-scale CuInSe2 precursor and could offer a simple, inexpensive, and alternative formation technology for CuInSe2 absorber layers. After spraying on Mo/glass substrates, the CuInSe2 thin films were annealed at 550 °C by changing the annealing time from 5 min to 30 min in a selenization furnace, using N2 as atmosphere. When the CuInSe2 thin films were annealed, without extra Se or H2Se gas used as the compensation source during the annealing process. The aim of this project was to investigate the influence of annealing time on the densification and crystallization of the CuInSe2 absorber layers to optimize the quality for cost effective solar cell production. The thickness of the CuInSe2 absorber layers could be controlled as the volume of used dispersed CuInSe2-isopropyl alcohol solution was controlled. In this work, X-ray diffraction patterns, field emission scanning electron microscopy, and Hall parameter measurements were performed in order to verify the quality of the CuInSe2 absorber layers obtained by the Spray Coating Method.

Effect of titanium ion energy on surface structure during the amorphous titanium dioxide film deposition

In this paper, we investigate the influences of the surface structure formation mechanism and the film properties on the incident titanium ion energy in the amorphous TiO2 thin film deposition process. The results show that the surface roughness of the film is reduced by increasing the energy of the incident titanium ions, and then the optical scattering loss of the film surface will decrease. It is also found that when the incident ion energy is increased, the film growth pattern changes from the “island-like” growth to the “layer-like” growth, and the surface diffusion coefficient of ions near the incident point is also significantly increased, which is conducive to the formation of more smooth film surface.

成膜の基礎

Thin films have recently emerged as one of the most important building blocks of nanotechnology and are often prepared under vacuum conditions. For efficient production of high-quality thin films, it is important to understand the impact of the vacuum on each stage of the thin film deposition processes, including decomposition of the starting material, transport of its vapor, and deposition. This article discusses the general key aspects of the thin film deposition process from the viewpoint of vacuum science and technology.

Preparation and characterization of DLC/SiO2/Al2O3 nanofiltration membrane

High quality ceramic thin films were fabricated by thin film deposition process in semiconductor field in order to fabricate high performance carbon/SiO 2 /Al 2 O3 membrane. α-Al 2 O 3 substrate was used as a supporting material. A severe thermal stress and rough surface for active ceramic top layer such as zeolite were observed. To overcome thermal stress, intermediate layer of SiO2 and diamond-like carbon (DLC) thin film were used. SiO 2 and DLC thin films on porous alumina support were deposited using plasma-enhanced chemical vapour deposition (PECVD). Homogeneous and smooth surfaces and interfaces of DLC/SiO 2 /Al 2 O 3 membrane were observed by FESEM. The phases of DLC and SiO 2 thin films were identified by X-ray diffraction pattern. Gas permeabilities of the nanofiltration membrane with DLC/SiO 2 /Al 2 O 3 were observed at various annealing temperatures. Mixed gas permeability of the membrane with 1 μm-thick SiO2 and 2 μm-thick DLC thin film annealed at 200 °C was ∼18 ccm at 1018 mb back pressure.

Growth and in situ high-pressure reflection high energy electron diffraction monitoring of oxide thin films

Interface and surface physics is an important sub-discipline within condensed matter physics in recent decades. Novel concepts like oxide-electronic device are prompted, and their performance and lifetime are highly dependent on the flatness and abruptness of the layer surfaces and interfaces. Reflection high-energy electron diffraction (RHEED), which is extremely sensitive to surface morphology, has proven to be a versatile technique for the growth study of oxide thin films. A differential pumping unit enables an implementation of RHEED to pulsed laser deposition (PLD) systems, ensuring an in situ monitoring of the film growth process in a conventional PLD working oxygen pressure up to 30 Pa. By optimizing the deposition conditions and analyzing the RHEED intensity oscillations, layer-by-layer growth mode can be attained. Thus atomic control of the film surface and unit-cell control of the film thickness become reality. This may lead to an advanced miniaturization in the oxide electronics, and more importantly the discovery of a range of emergent physical properties at the interfaces. Herein we will briefly introduce the principle of high-pressure RHEED and summarize our main results relevant to the effort toward this objective, including the growth and characterization of twinned La2/3Ca1/3MnO3 thin films and ReTiO3+δ/2 (Re = La, Nd; δ = 0 ∼ 1) A n B n O3n+2 structures, on YSZ-buffered ‘Silicon on Insulator’ and LaAlO3 substrates, respectively, as well as the study of the initial structure and growth dynamics of YBa2Cu3O7−δ thin films on SrTiO3 substrate. Presently we have realized in situ monitoring and growth mode control during oxide thin film deposition process.

Electrical and Mechanical Characteristics of Room Temperature Deposited Silicon Nitride Using Two Inner Parallel Cylindrical Coils Inductively Coupled Plasma Chemical Vapor Deposition

For investigating silicon nitride (SiN) thin film deposition process at room temperature without additional substrate heating, we studied inductively coupled plasma chemical vapor deposition with two inner parallel cylindrical coils which can activate the more radicals and charged species in the plasma. We investigated the influence of plasma RF power on the characteristics of room temperature deposited SiN films. Deposition rates, dielectric constant, refractive index, and stress of the films ranged from 4.5 nm/min to 8.3 nm/min, 8.4 to 10, 1.8 to 2.1, and 0.54 to 0.15, respectively. According to the FTIR measurements, the concentration of the Si--H and N--H bonds was decreased as the RF power increased, and the Si--H bonds tended to disappear at RF power over 500 W. This reduction in the hydrogen content was accompanied by the increases in the deposition rate and refractive index. It was confirmed that the breakdown field could be also maximized to 10 MV/cm.

Electrodeposition of CoPtMo magnetic films with incorporation of phosphorus

Electrodeposition as a kind of significant electrochemical technique was used to prepare CoPtMo magnetic materials on copper substrate from an alkaline electrolyte. The influence of hypophosphite addition on the deposition process, alloy content, microstructure and magnetic properties of CoPtMo thin films was studied. The films that were prepared from the electrolytes without hypophosphite exhibited an fcc structure, with higher Pt percentage but lower coercivity. The presence of hypophosphite shifted alloy deposition to more negative potentials, limited the platinum percentage, caused higher Co content and exhibited an hcp structure. It was found that much higher coercivity of CoPtMo(P) than that of CoPtMo was mainly due to the incorporation of P at the grain boundaries.