Deposition Rate Measurements Research Articles

Plasma etching of Hf-based high-k thin films. Part III. Modeling the reaction mechanisms

A generalized etch rate model was formulated to describe metal oxide etching in complex plasma chemistries, based on the understanding gained from detailed plasma characterization and experimental investigation into the metal oxide etching mechanisms. Using a surface site balance-based approach, the correct etch rate dependencies on neutral-to-ion flux ratio, ion energy, competing deposition and etching reaction pathways, and film properties were successfully incorporated into the model. The applicability of the model was assessed by fitting to experimental etch rate data in both Cl2 and BCl3 chemistries. Plasma gas phase analysis as well as etch and deposition rate measurements were used to calculate initial values and appropriate ranges for model parameter variation. Physically meaningful parameter values were extracted from the modeling fitting to the experimental data, thereby demonstrating the applicability of this model in assessing the plasma etching of other complex materials systems.

<I>In~situ</I> Kinetics Study in Chemical Vapor Deposition of Pyrocarbon from Propylene

The deposition kinetics of pyrocarbon by chemical vapor deposition(CVD)from propylene was investigated by in situ measurements of deposition rates which were measured by Magnetic Sus- pension Balance TG system.The gas phase products that collected by a liquid nitrogen cold trap were analyzed by GC-MS.The apparent activation energy is(201.9±0.6)kJ/mol in the range from 850℃to 1100℃,where dilution ratio a is 4,total pressure is 6kPa and the flow rate of propylene is 20sccm,and the deposition kinetics is controlled by homogenous reactions.The main products of gas phase are single ring aromatic hydrocarbons and polycyclic aromatic hydrocarbons(PAHs)at high and low tempera- tures,respectively.Through the investigation of dependence of propylene partial pressure(0.3-6.5kPa) on deposition rate in 900℃and 1000℃,it can be concluded that the decomposition of propylene is a first order reaction.Related to both of the effective reaction time and the flow rate of propylene,the maximum of the deposition rate is found at residence time of 0.6s.

Deposition of Plasma‐Polymerized 1‐Cyanoisoquinoline Thin Films and Their Dielectric Properties

AbstractA novel plasma‐polymerized 1‐cyanoisoquinoline (PPCIQ) thin film of desired thickness was prepared by plasma polymerization under different glow discharge conditions. The effect of the discharge power on the chemical structure, surface composition and morphology of the PPCIQ thin films were investigated by Fourier Transform Infrared (FTIR) Spectroscopy, X‐ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and deposition rate measurements. A high retention of the aromatic ring structure of the starting monomer in the deposited plasma films is obtained at a low discharge power of 15 W. The plasma‐synthesized films are homogeneous and quite suitable for the measurement of dielectric properties. The dielectric measurements show that a low dielectric constant of 2.62 has been obtained for the PPCIQ thin films for the first time.magnified image

The physical reason for the apparently low deposition rate during high-power pulsed magnetron sputtering

In high-power pulsed magnetron sputtering, a large power density is applied giving rise to a high degree of ionization. From an application point of view, the major drawback of this technology is the considerably lower deposition rate as compared to DC magnetron sputtering. Using transport-of-ions-in-matter simulations, we show that the apparently low deposition rate can be understood based on the non-linear energy dependence of the sputtering yields. Our calculations are consistent with deposition-rate measurements on Cu films as well as with published deposition-rate data for Ti [Konstantinidis S, Dauchot JP, Ganciu M, Ricard A, Hecq M. J Appl Phys 2006;99:013307].

Transient depletion of source gases during materials processing: a case study on the plasma deposition of microcrystalline silicon

Transient depletion of source gases can play an important role in materials processing, particularly during the initial phase of thin film synthesis in which nucleation takes place and the interface is formed. In this paper, we present a zero-order analytical model that allows an estimation of the magnitude and timescale of transient depletion. The model is based on a lumped particle balance for a processing region and reactor volume that are coupled via a directive feed gas flow and diffusive transport. To illustrate the model, an experimental case study is presented on transient depletion during the parallel plate radio-frequency SiH4+H2 plasma deposition of microcrystalline silicon for solar cells. The SiH4 steady-state depletion was experimentally determined by mass spectrometry, deposition rate and optical emission spectroscopy measurements. The transient depletion of the SiH4 was monitored by time-resolved optical emission spectroscopy measurements. Model and experiment are in good agreement. The implications for materials processing and thin film synthesis, as well as methods to control transient depletion, are discussed.

Modeling the Past Atmospheric Deposition of Mercury Using Natural Archives

Historical records of mercury (Hg) accumulation in lake sediments and peat bogs are often used to estimate human impacts on the biogeochemical cycling of mercury. On the basis of studies of lake sediments, modern atmospheric mercury deposition rates are estimated to have increased by a factor of 3-5 compared to background values: i.e., from about 3-3.5 microg Hg m(-2) yr(-1) to 10-20 microg Hg m(-2) yr(-1). However, recent studies of the historical mercury record in peat bogs suggest significantly higher increases (9-400 fold, median 40x), i.e., from about 0.6-1.7 microg Hg m(-2) yr(-1) to 8-184 microg Hg m(-2) yr(-1). We compared published data of background and modern mercury accumulation rates derived from globally distributed lake sediments and peat bogs and discuss reasons for the differences observed in absolute values and in the relative increase in the industrial age. Direct measurements of modern wet mercury deposition rates in remote areas are presently about 1-4 microg m(-2) yr(-1), but were possibly as high as 20 microg Hg m(-2) yr(-1) during the 1980s. These values are closer to the estimates of past deposition determined from lake sediments, which suggests that modern mercury accumulation rates derived from peat bogs tend to overestimate deposition. We suggest that smearing of 210Pb in the uppermost peat sections contributes to an underestimation of peat ages, which is the most important reason for the overestimation of mercury accumulation rates in many bogs. The lower background mercury accumulation rates in peat as compared to lake sediments we believe is the result of nonquantitative retention and loss of mercury during peat diagenesis. As many processes controlling time-resolved mercury accumulation in mires are still poorly understood, lake sediments appear to be the more reliable archive for estimating historical mercury accumulation rates.

Pulsed laser ablation and deposition of complex oxides

The pulsed laser ablation and deposition (PLD) processes of SrTiO3 were studied as a model system for developing a technique for the growth of structurally bulk-equivalent epitaxial thin films of typical complex oxides. Deposition rate vs. laser fluence measurements showed that there is a second critical fluence value above the ablation threshold. Below the critical value, both the ablation and deposition rates are linear functions of the fluence and independent of the ablation spot area. Above the critical value, the deposition rate per unit ablation area depends strongly on the ablation spot area. Homoepitaxial SrTiO3 films possessed the exact bulk lattice constant value only when the films were grown at the critical fluence, whereas larger lattice constants were obtained if the fluence was either higher or lower. Composition analysis revealed that the enlargement of the lattice constant was related to cationic unbalance. This critical laser fluence is essential for the growth of bulk-equivalent epitaxial films, and therefore accurate measurement of laser energy and ablation area is vital for reproducible film growth.

Measurements of dry deposition rates of 212Pb from aerosols on various natural and artificial surfaces

The dry deposition rates on various grass fields and two forests have been measured by the use of 212Pb (T1/2 = 10.6 hours). The deposition rate on grass fields (average: 7 mm·s−1) roughly depends on the logarithms of the heights or densities of the grasses. The dry deposition rates on a broadleaved forest (Lithocarpus edulis) and a coniferous forest (Cryptomeria Japonica) were also measured. The highest (ave. 26 mm·s−1) was on the forest of C. Japonica because of the dense and adhesive surfaces of the leaves.

AC powered reactive magnetron deposition of indium tin oxide (ITO) films from a metallic target

Transparent highly conductive indium tin oxide (ITO) films for low cost applications were deposited by a reactive dual magnetron sputter process using metallic targets. The magnetrons were equipped with rectangular (130 × 400 mm 2) In:Sn targets (90 wt.% In/10 wt.% Sn). A sine wave power supply was used at a frequency of about 70 kHz. All experiments were done in the transition mode at a constant argon flow of 40 sccm and an oxygen flow varied between 35 and 70 sccm. The total pressure was kept constant at 0.4 Pa. The films were deposited onto silicon and float glass substrates which were either moved in an oscillatory manner (dynamic deposition) or fixed in front of the targets (static mode) during deposition. A dynamic deposition rate of about 100 nm × m/min was obtained at an average power of 2 kW/cathode. The film thickness was adjusted to 500 nm. At an optimised Ar/O 2 gas flow ratio of 0.6 we found an electrical resistivity as low as 1.2 × 10 − 3 Ω cm. The refractive index of these films was about 2.05 indicating a dense film structure, while the optical absorption of k = 10 − 2 qualifies these ITO films for many low cost applications. Moreover, the film structure and texture were investigated by XRD methods. Applying a static deposition we have achieved a lower electrical resistivity with a minimum value of 6 × 10 − 4 Ω cm. In this case, the resistivity and the transparency, respectively, were not constant over the substrate but depend on the lateral position in front of the target. To explain this inhomogeneity we have performed spatially resolved deposition rate and Langmuir probe measurements and related their results to film structure and properties. In order to improve the film properties at dynamic deposition the growth conditions have to be homogenised at all substrate positions.

Investigation of Ash Deposition Rates for a Suite of Biomass Fuels and Fuel Blends

This investigation details the effects of the fuel constituents through systematic experimental and theoretical analysis of a suite of fuels with widely varying inorganic contents and compositions. The experiments were carried out in the multifuel flow reactor (MFR) at Brigham Young University. Fuels included straw, grain screenings, sawdust, sunflower shells, sugar beat pulp, and shea nutshells. Out of the six major fuels, two base fuels (straw and grain screenings) were mixed with the other four fuels in 1:1 ratio by weight. The data from a series of experiments quantitatively illustrated the effects of fuel properties and fuel interactions on ash deposition rate. In the deposition rate measurement investigation, the predicted results from a simple model of ash deposition assuming “no interactions” between fuels were compared with the measured results to demonstrate the fuel interactions. A significant decrease in ash deposition rate was observed for fuels blends in comparison with that of pure fuels (straw and grain screening). The decrease in deposition rate was attributed to the fuel interactions.

Influences of carbon content and power density on the uniformity of PECVD grown a-Si 1−x:C x:H thin films

Large area electronics require large size thin films whose eventual inhomogeneities arise as a problem. Hydrogenated amorphous silicon carbide thin films (a-Si 1− x C x :H) for four different source gas mixtures at two power densities were deposited by plasma enhanced chemical vapor deposition (PECVD) technique. The degree of film homogeneity was investigated through measurements of deposition rate, refractive index and optical energy gap along the radial direction of bottom electrode. Both ellipsometer at various incident angles and optical transmittance at normal incidence were used in mutual control as diagnosing tools. It seems there is a critical power density beyond which inhomogeneities of the deposited films along the radial direction of the electrode are unavoidable.

RF power and SiO xC yH z deposition efficiency in TEOS/O 2 discharges for the corrosion protection of magnesium alloys

The effect of the applied voltage of 27.12 MHz TEOS/O 2/He discharges on the deposition process of SiO x C y H z thin films over rough as-cast Mg alloys was investigated by applying plasma diagnostics, surface characterization techniques and electrochemical impedance spectroscopy. The process efficiency in terms of power usage and deposition rate was calculated from plasma electrical and deposition rate measurements and was found to follow an inverse relation to the applied voltage, while saturating at higher voltages. Films with good substrate step coverage and free of cracks and structure failures were deposited at intermediate applied voltages and total power dissipation. As a consequence, the corrosion resistance of the films was optimized at the same conditions, indicating that in the case of no special pre-treatment of the Mg substrates, the corrosion performance is mainly determined by the SiO x C y H z adhesion to the substrate rather than the chemical composition of the films.

Void-Free Trench-Filling by Electroless Copper Deposition Using the Combination of Accelerating and Inhibiting Additives

Electroless copper deposition was performed on submicrometer-trench patterned substrates with a bath containing 8-hydroxy-7-iodo-5-quinoline sulfonic acid (HIQSA) as an accelerating additive and polyethylene glycol (PEG) as an inhibiting additive. Void-free copper filling of trenches was achieved by the addition of both HIQSA and PEG at specific concentrations. Copper deposition rate measurements revealed that HIQSA accelerated the deposition only when it was added together with a very low concentration of PEG. The void-free filling is considered to have resulted from the significant acceleration brought about by HIQSA at the trench bottom, where the concentration of PEG is low.

Plasma-assisted co-evaporation of β-indium sulfide thin films

Abstract This paper describes the development of plasma-assisted co-evaporation (PACE) for the formation of β -In 2 S 3 thin films. Indium was supplied by conventional thermal evaporation, while the chalcogen gas precursor (H 2 S) was activated using an inductively coupled plasma (ICP) source. Using a combination of optical emission spectroscopy and mass spectrometry it was shown that the ICP effectively dissociated H 2 S, producing atomic sulfur. Transport modeling was used to quantify the flux distributions of the co-evaporated metal and the plasma-generated species impinging the substrate. Model predictions were validated by measurements of deposition rate and film properties. Substantial improvements in both materials utilization and substrate temperature reduction were realized with respect to conventional co-evaporation. β -In 2 S 3 was formed as low as 100 °C and it was observed that quality was a strong function of S/In ratio. The grain size decreased and the optical band gap increased as the substrate temperature was reduced.

Influence of substrate temperature on the deposition and structural properties of μc-Si: H thin films fabricated with VHF-PECVD

With in situ optical emission spectroscopy (OES) diagnosis on VHF-generated H2+SiH4 plasmas, and with the measurements of deposition rate and structure of μc-Si: H thin films fabricated with VHF-PECVD technique at different substracte temperature, influence of substrate temperature on the deposition of μc-Si: H thin film and on its structural properties have been investigated. The results show that with the increase of substrate temperature, the crystalline volume fraction Xc and average grain size d are enhanced monotonously, but the deposition rate increases firstly and then decreases. The optimized substrate temperature for (μc-Si: H thin films deposition under our current growth system is about 210 °C, at which deposition rate 0.8 nm/s of μc-Si: H thin film with Xc∼60% and d∼9 nm can be obtained.

The Role of Oxygen Dissociation in Plasma Enhanced Chemical Vapor Deposition of Zinc Oxide from Oxygen and Diethyl Zinc

The influence of electron impact dissociation of oxygen on neutral chemistry was studied for plasma-enhanced chemical vapor deposition (PECVD) of zinc oxide using oxygen and diethyl zinc. Electron conditions in the reactor were estimated based on simulations of well-known Ar-O2 plasmas, while the majority of the thermal chemistry was abstracted from the combustion literature. A rudimentary model of film growth was developed using the rate of oxygen dissociation as the lone adjustable parameter.n Model results were compared directly with experimental measurements of deposition rates and neutral species densities for a wide range of conditions. Good quantitative agreement between experiments and model were observed as a function of composition and rf power. The system is highly sensitive to the electron impact dissociation of oxygen, which creates the radical pool that drives the majority of the chemistry. The approach detailed here provides a framework for the development of models of oxide PECVD derived from other metalorganic precursors.

Increasing the deposition rate of oxide films by increasing the plasma reactivity

One of the major problems of reactive sputtering is the dramatically deposition rate decrease when the target surface is poisoned. For decades, numerous papers have been published in order to solve this problem using the same basic idea: prepare a compound film while the target remains non-poisoned. In this work, we propose an original way to reach this goal. From previous results, we have shown that the substrate oxidation occurs mainly by the reactive gas atomic species. In order to favour this reaction we have increased the plasma reactivity by a RF coil located between the DC magnetron target and the substrate. We have studied three reactive systems: Sn–Ar/O2, Ti–Ar/O2 and Ag–Ar/O2. For each of these systems, we have estimated the RF coil influence on the chemical behavior of both the discharge and the films. The discharge is characterized by mass spectrometry measurements whereas the films' compositions are obtained by XPS. Increasing the RF coil power, we observe an increase of the oxygen concentration in the films for the same introduced pO2. On the other hand, the target metal-compound transition, observed on the deposition rate measurements, is not influenced by the amplification. So, using the RF coil, the fully oxidized films is reached at lower reactive gas flow and consequently at higher deposition rate.

High pressure regime of plasma enhanced deposition of microcrystalline silicon

An investigation of the effect of the total gas pressure on the deposition of microcrystalline thin films form highly diluted silane in hydrogen discharges was carried out at two different frequencies. The study was performed in conditions of constant power dissipation and constant silane partial pressure in the discharge while using a series of plasma diagnostics as electrical, optical, mass spectrometric, and in situ deposition rate measurements together with a simulator of the gas phase and the surface chemistry of SiH4∕H2 discharges. The results show that both the electron density and energy are affected by the change of the total pressure and the frequency. This in turn influences the rate of high energy electron–SiH4 dissociative processes and the total SiH4 consumption, which are favored by the frequency increase for most of the pressures. Furthermore, frequency was found to have the weakest effect on the deposition rate that was enhanced at 27.12MHz only for the lowest pressure of 1Torr. On the other hand, the increase of pressure from 1to10Torr has led to an optimum of the deposition rate recorded at 2.5Torr for both frequencies. This maximum is achieved when the rate of SiH4 dissociation to free radical is rather high; the flux of species is not significantly hindered by the increase of pressure and the secondary gas phase reactions of SiH4 act mainly as an additional source of film precursors.

Scaling behavior of microwave reactors and discharge size for diamond deposition

Several microwave reactors of various sizes were studied to quantify the size scaling behavior of microwave plasma-assisted CVD (PACVD) diamond deposition. All the systems studied were microwave resonant cavity based systems using predominantly hydrogen based discharges. The input variables considered include the microwave frequency (2.45 GHz and 915 MHz), the microwave power level, and the discharge chamber size (5–28 cm diameter). The substrate sizes for the various reactors studied ranged from 2.5 cm diameter substrates for the small reactor size to 15 cm diameter substrates for the large reactor size. The variables quantified in the diamond deposition process and reactor included the microwave discharge power density, discharge size, discharge gas temperature, as well as, measurements of diamond deposition area and rate. The discharge power density versus pressure and discharge size is quantified by experimental measurements and numerical modeling. Results show that as the discharge size increases the discharge power density decreases significantly at a given pressure.

Powder preparation for 0.5 Pb(Ni 1/3Nb 2/3)O 3–0.15 PbZrO 3–0.35PbTiO 3 thick films by the aerosol deposition method

Powders of 0.5Pb(Ni 1/3Nb 2/3)O 3–0.15PbZrO 3–0.35PbTiO 3(PNN/PZT) composition that were calcined at 850, 900, and 950 °C were deposited as a thick film on a stainless-steel SUS304 substrate using an aerosol deposition method (ADM) at room temperature. A film with single perovskite phase was obtained only in the case of using the raw powder calcined at 950 °C. The measured deposition rate of ADM was as high as 1 μm/min for a film of 10×10 mm 2 area. The film annealed at 600 °C was formed by polycrystallites with 83-nm average diameter, but transmission electron microscope observation revealed that amorphous phase and fine polycrystallites formed the as-deposited film. The best electric properties were obtained for the deposited film using the raw material powders calcined at 950 °C. The obtained values are: remnant polarization (Pr), 18 μC/cm 2; coercive field ( E c), 65 kV/cm; dielectric constant ( ε r ), 750 at 1 kHz; and dielectric loss (tan δ ), 0.04 at 1 kHz.