Chemical Vapor Deposition Films Research Articles

Perfluorocompounds (PFCs) Abatement System Utilizing Fluorine Immobilized Adsorbent

In order to minimize contributions to global warming, it is important to develop a Perfluorocompounds (PFCs) abatement system that can remove PFCs effectively with low electric power. We have developed a new PFCs abatement system consisting mainly of a 2 MHz ICP plasma source and two CaO columns operated at low pressure. The CaO agent developed for this system has a specific surface area of 60-80 m2/g and a grain diameter of 2-6 mm, simultaneously. Reactive fluorinated compounds are immobilized in the CaO columns without a water scrubber to prevent the recombination of fluorocarbons. Stable compounds such as CF4 are decomposed by the 2 MHz ICP plasma before introducing in the second CaO column. When the emissions from a fluorocarbon film chemical vapor deposition process chamber were treated by this abatement system, PFCs removal efficiency and CO2 equivalent removal efficiency was 99.96% and 93.5%, respectively.

Effect of wire temperature on the microstructural evolution of Si films in hot-wire chemical vapor deposition for digital display and photovoltaic devices

The formation of crystalline phase in Si by hot-wire chemical vapor deposition (HWCVD) was investigated, focusing on the microstructural evolution as a function of hot-wire temperature. The microstructure of films deposited on a Si wafer was compared between hot-wire temperatures of 1590, 1670, and 1800 °C. A heavily twinned structure was observed at the wire temperature of 1670 °C, which resulted in the apparent intensity peak of (1 1 1) hexagonal-closed packed (HCP) crystalline Si from a typical face-centered cubic (FCC) crystalline Si structure in the X-ray diffraction analysis. The twin-related HCP crystalline phase was markedly diminished at 1800 °C and hardly observed at 1590 °C. The observed deposition behavior was approached by the effect of the wire temperature on the size of charged nanoparticles formed in the gas phase in the HWCVD process.

Effects of amino-terminated self-assembled monolayers on nucleation and growth of chemical vapor-deposited copper films

Copper films were grown on clean Si, SiO 2 and 3-amino-propyl-trimethoxy-silane (APTMS) self-assembled monolayers (SAMs)-modified SiO 2 substrates via chemical vapor deposition (CVD) and were examined using scanning electron microscopy, atomic force microscopy, and X-ray diffraction (XRD). Ordered APTMS-SAMs obtained from a 3 mM concentration solution were found to enhance adhesion of the films on the SiO 2 substrate surface. However, in 60 mM solution, APTMS layers tended to be multilayered and formed islands via self-polymerization. Copper nucleation on APTMS-SAMs modified substrate surfaces occurs more easily than on the clean Si and SiO 2 substrate surfaces. Enhanced copper CVD was ascribed to the interaction of Cu atoms with the N-containing terminal groups of APTMS-SAMs. The XRD analysis showed that the copper thin films deposited on the APTMS-modified SiO 2 substrates have a structure with (111) preferred orientation, which is known to have a good electromigration resistance.

On the mechanism of remote plasma-enhanced chemical vapor deposition of films

332 As we showed earlier [1], the remote plasmaenhanced chemical vapor deposition (RPE-CVD) process used for film fabrication makes it possible to preserve intact fragments of a precursor molecule that are required to synthesize the desired material. Despite close attention given by researchers to such processes, most works in this field deal with the study of the dependence of the properties of the film material on the synthesis conditions, while the mechanism of plasmaassisted activation of precursor molecules remains beyond the area of experimental interest [2–4].

SU‐GG‐T‐273: Suitability of Synthetic Diamond Films for Radiotherapy Dosimetry

Purpose: To investigate the suitability of synthetic diamond films as detectors for radiotherapy dosimetry. Method and Materials: A range of commercially available diamond films grown by chemical vapor deposition (CVD) have been studied using spectroscopic, microscopic and electrical characterization techniques, including Raman spectroscopy, optical, secondary electron, and atomic force microscopy. Diamond detectors incorporating Perspex have been fabricated in order to examine various response characteristics, especially transient behavior and priming effects, due to material defects, interface phenomena, etc. Initial dosimetric characterization was performed using a 6 MV photon beam from a Varian 600C linac. Measurements were achieved using a 2570/1 Farmer Dosimeter and a Keithley 6430 SourceMeter. EGSnrc code was used to model simple device structures to assess performance issues that may impede proper measurements e.g. sources of fluence perturbation, absorbed dose distribution, and charge collection efficiency. Results: I–V measurements of polycrystalline diamond films with Ag contacts tested under a ±210 V bias sweep exhibited nonlinear behavior as expected. High leakage currents were a problem for some detectors. Resistivity measurements at 100 V from one manufacturer of films spanned from 1011 to 1012 Ω⋅cm. Dependence on fluence and fluence rates between 50 – 250 MU/min was observed. However, angular dependence appeared to be negligible. Overshoot was also seen during initial exposure, as well as the well‐known priming effect as the signal evolved over time. EGSnrc models have illustrated how electrode thickness alters the dose delivered to the sensitive volume. Conclusion: Experiments will continue to explore the response phenomena of CVD diamond films to evaluate their suitability as detectors for medical applications. The films studied thus far have exhibited typical behavior as seen in previous literature. A thorough characterization of a variety of CVD films and their consequential responses is underway in order to mitigate or ideally eliminate inherent shortcomings.

Effect of negatively charged species on the growth behavior of silicon films in hot wire chemical vapor deposition

The deposition behavior of silicon in hot wire chemical vapor deposition was investigated, focusing on the generation of negatively charged species in the gas phase using a gas mixture of 20% SiH 4 and 80% H 2 at a 450 °C substrate temperature under a working pressure of 66.7 Pa. A negative current of 6–21 µA/cm 2 was measured on the substrate at all processing conditions, and its absolute value increased with increasing wire temperature in the range of 1400 °C–1900 °C. The surface roughness of the films deposited on the silicon wafers increased with increasing wire temperature in the range of 1510 °C–1800 °C. The film growth rate on the positively biased substrates (+ 100 V, + 200 V) was higher than that on the neutral (0 V) and negatively biased substrates (− 100 V, − 200 V, − 300 V). These results indicate that the negatively charged species are generated in the gas phase and contribute to deposition. The surface roughness evolved during deposition was attributed to the electrostatic interaction between these negatively charged species and the negatively charged growing surface.

Thermal-Hydrogen Promoted Selective Desorption and Enhanced Mobility of Adsorbed Radicals in Silicon Film Growth

Car-Parrinello simulations and static density-functional theory calculations reveal how hydrogen promotes growth of epitaxial, ordered Si films in plasma-enhanced chemical vapor deposition at low-temperature conditions where the exposed Si(001)-(2x1) surface is fully hydrogenated. Thermal H atoms, indeed, are shown to selectively etch adsorbed silyl back to the gas phase or to form adsorbed species which can be easily incorporated into the crystal down to T approximately 200 degrees C and start diffusing around T approximately 300 degrees C. Our results are well consistent with earlier experiments.

Controlling the quality of nanocrystalline silicon made by hot-wire chemical vapor deposition by using a reverse H2 profiling technique

Hydrogen profiling, i.e., decreasing the H2 dilution during deposition, is a well-known technique to maintain a proper crystalline ratio of the nanocrystalline (nc-Si:H) absorber layers of plasma-enhanced chemical vapor-deposited (PECVD) thin film solar cells. With this technique a large increase in the energy conversion efficiency is obtained. Compared to PECVD, the unique characteristics of hot-wire CVD (HWCVD), such as the catalytic reactions, the absence of ion bombardment, the substrate heating by the filaments and filament aging effects, necessitate a different strategy for material and device optimization. We report in this paper the results of using a reverse H2 profiling technique, i.e., increasing the H2 dilution of silane instead of decreasing it, to improve the quality of HWCVD intrinsic nc-Si:H and the performance of this material in single junction n-i-p cells. Thus far, the efficiency of nc-Si:H n-i-p cells made on a stainless steel substrate with an Ag/ZnO textured back reflector has been improved to 8.5%, and the efficiency of triple junction solar cells with a structure of proto-Si:H(HWCVD) top cell/proto-SiGe:H (PECVD) middle cell/nc-Si:H (HWCVD, with reverse H2 profiling) bottom cell has reached 10.9%. These efficiency values show the viability of n-i-p cells comprising HWCVD nanocrystalline i-layers.

Atomic Layer Deposition of Silicon Oxide Thin Films by Alternating Exposures to Si[sub 2]Cl[sub 6] and O[sub 3

We report the process for the atomic layer deposition (ALD) of silicon dioxide thin films on a silicon wafer by alternating exposures to Si 2 Cl 6 and O 3 . The deposition was governed by a self-limiting ALD reaction at 403-453°C, and the growth rate at 453°C was saturated at 0.32 nm/cycle for Si 2 Cl 6 exposures over 1 X 10 8 L. However, at 471°C or higher temperatures, the thermal decomposition of Si 2 Cl 6 and the oxidation of Si by O 3 dominated the deposition, resulting in high growth rates and Si-rich films. The ALD films exhibited excellent electrical properties that were equivalent to those of low-pressure chemical vapor deposition films.

Chemical gases sensing properties of diamond nanocone arrays formed by plasma etching

A uniform diamond nanocone array was formed by plasma etching of diamond film in a hot filament chemical vapor deposition (HFCVD) system. A surface amorphous carbon coating layer, which is formed during CH4/H2 plasma-etching process, was removed by Ar plasma in a reactive ion etching system. The hydrogenation of diamond nanocones was performed in H2 ambience by using the same HFCVD system. The air-diluted NH3 and NO2 gases sensing properties of the diamond cone arrays had been studied by using electric current versus measurement time characteristics at room temperature. The repeatable chemical sensing properties of the hydrogenated diamond cone array sensor are enhanced, in comparison with as-formed diamond film. Surface two-dimensional hole gas structure and greatly increased surface-to-volume ratio both play a key role for the excellent detection performance. As-formed diamond nanocone arrays show a promising prospect for applications as chemical sensor for both reducing (NH3) and oxidizing (NO2) gases.

Vapor Deposition of Ruthenium from an Amidinate Precursor

Atomic layer deposition (ALD) and pulsed chemical vapor deposition (CVD) were used to make ruthenium (Ru) thin films from a volatile Ru amidinate precursor, bis(-di-tert-butylacetamidinato)ruthenium(II) dicarbonyl. The CVD films were grown without any coreactant, while the ALD films used ammonia as a coreactant. The films are fine-grained polycrystalline ruthenium with high purity ( impurities). Ru grew as a continuous, electrically conductive, pinhole-free film on tungsten nitride (WN) films even for films as thin as . The resistivities of the films match those of pure sputtered ruthenium of the same thickness. Roughness is of the film thickness. The films are very conformal, with 80% step coverage over holes with high aspect ratios (40:1). This thermal process does not use any oxidant or plasma as a second reagent, thereby avoiding damage to sensitive substrates. The ALD growth rate can reach at a substrate temperature of .

Ultrafine Patterning of Nanocrystalline Diamond Films Grown by Microwave Plasma-Assisted Chemical Vapor Deposition

The growth of nanocrystalline diamond films having an appropriate surface smoothness for nanoscaled ultrafine patterning was investigated. The surface smoothness of polycrystalline diamond films was controlled by introducing nitrogen (N2) gas at concentrations ranging from 0 to 1.0% into the gas mixtures of methane (CH4) and hydrogen (H2) on microwave plasma-assisted chemical vapor deposition (MPCVD). The added 1.0% N2 with 10% CH4 in the gas phase yielded the desired diamond film with the smoothest surface among the conditions. An N-doped nanocrystalline diamond film was fabricated by nanoscaled ultrafine patterning by e-beam lithography followed by reactive ion etching (RIE). As a mask material in RIE, we found that a chemical vapor-deposited amorphous silicon nitride film is appropriate. A mixture consisting of oxygen and a small amount of tetrafluoro carbon was used as the etching gas. We succeeded in achieving a minimum line width of 100 nm in the N-doped nanocrystalline diamond film with our fabrication process.

Protection of organic light-emitting diodes over 50 000 hours by Cat-CVD SiN x/SiO xN y stacked thin films

Silicon oxynitride (SiO x N y ) films have been formed by adding proper amount of oxygen gas to usual forming condition of silicon nitride (SiN x ) films in catalytic chemical vapor deposition (Cat-CVD) method. The composition and refractive index of the film can be systematically controlled by changing oxygen flow rate. Organic light-emitting diodes (OLEDs) covered with SiN x /SiO x N y stacked films have been completely protected from damage due to oxygen and moisture and their initial emission intensity is maintained over 1000 hours under 60 °C and 90% RH, which is equivalent to 50 000 hours in normal temperature and humidity conditions.

The influence of boron concentrations on structural properties in disorder silicon films

In this work we present a detailed structural of a series of B-doped hydrogenated microcrystalline silicon (μc-Si:H) films deposited by plasma-enhanced chemical vapor deposition (PECVD) and B-doped polycrystalline silicon (poly-Si) films produced by step-by-step laser crystallization process from amorphous silicon. The influence of doping on the structural properties and structural changes during the sequential crystallization processes were monitored by Raman spectroscopy. Unlike μc-Si:H films, that consist of a two-phase mixture of amorphous and ordered Si, partially crystallized sample shows a stratified structure with polycrystalline silicon layer at the top of an amorphous layer. With increasing doping concentration the LO-TO phonon line in poly-Si shift to smaller wave numbers and broadens asymmetrically. The results are discussed in terms of resonant interaction between optical phonons and direct intraband transitions known as a Fano resonance. In μc-Si:H films, on the other hand, the Fano effect is not observed. The increase of doping in μc-Si:H films suppressed the crystalline volume fraction, which leads to an amorphization in the film structure. The structural variation in both μc-Si:H and poly-Si films leads to a change in hydrogen bonding configuration.

Characteristics of SiO<sub>2</sub> Film Grown by Atomic Layer Deposition as the Gate Insulator of Low-Temperature Polysilicon Thin-Film Transistors

SiO2 films were prepared by atomic layer deposition (ALD) technique, and their physical and electrical properties were characterized for being applied as a gate insulator of low-temperature polysilicon thin-film transistors. ALD SiO2 films were deposited at 350–400 oC using alternating exposures of SiH2Cl2 and O3/O2, and the characteristics of the deposited films were improved with increasing deposition temperature. The ALD films deposited at 400 oC exhibited integrity, surface roughness and leakage current better than those of the conventional plasma-enhanced chemical vapor deposition (PECVD) films.

Effect of pressure on nanocrystalline diamond films deposition by hot filament CVD technique from CH 4/H 2 gas mixture

The effect of pressure on the deposition of nanocrystalline diamond (NCD) films in a hot filament chemical vapor deposition (HFCVD) system was investigated employing a 1% CH 4 in H 2 gas mixture. With decreasing the growth pressure from 5.0 to 0.125 kPa, a gradual reduction of the diamond grain sizes from sub-micrometer to nanometer scale was observed, accompanied by the decline of surface roughness and the evolution of film cross-sectional morphologies changing from columnar to grainy structures. The pressure also exerted prominent influence on the film growth rate. At 2.8 kPa the growth rate featured a maximum, while decreasing to higher and lower pressures. Such pressure dependence of the diamond growth rate was suggested to result from two competing effects of pressure on the concentration of reactive species near the diamond growth surface. Further, the mechanism for the NCD film formation under low deposition pressures was discussed in light of the high secondary nucleation rate.

Maskless Plasma Etching of Diamond Cones: The Role of CH4 Gas and Enhanced Field Emission Property

Diamond cone arrays were formed by plasma etching of diamond films in a hot filament chemical vapor deposition (HFCVD) system. The role of CH4 in the formation of diamond cone arrays was investigated. It was found that addition of CH4 to H2 plasma could enhance the plasma intensity and hence the etching efficiency to improve the formation of diamond cones with high aspect ratio and controllable density. The microscopic measurement of the as-formed diamond cones shows that they have an inner core of polycrystalline structure and an outer layer of amorphous carbon. These as-formed diamond cones have exhibited field emission current density of 1 μA/cm2 at threshold field of 5 V/μm. For an applied field of 12 V/μm, the emission current density can rapidly reach as high as 560 μA/cm2. The property of high field electron emission is attributed to the high aspect ratio of as-formed diamond cones and the appropriate cone density as well as the outer amorphous carbon layer which acts as a pathway for electron-hopp...

Hydrogen Passivation of LPCVD Si3N4 ∕ SiO2 ∕ Si Stacks by Ammonia Plasma Treatment

The bonded hydrogen concentration in thermally annealed low-pressure chemical vapor deposition (LPCVD) films increases rapidly following exposure to ammonia plasma and saturates at a concentration determined by the thermal history of the films. Where the nitride layer is deposited on oxidized silicon samples, the introduction of hydrogen into the nitride film using ammonia plasma is effective at passivating the interface. The plasma treatment does not lead to the generation of a significant number of additional interface defects, shown by lifetime and electronic paramagnetic resonance measurements. Subsequent anneals in nitrogen further improve the interface passivation.

Crystal structure and band gap determination of HfO2 thin films

Valence electron energy loss spectroscopy (VEELS) and high resolution transmission electron microscopy (HRTEM) are performed on three different HfO2 thin films grown on Si (001) by chemical vapor deposition (CVD) or atomic layer deposition (ALD). For each sample the band gap (Eg) is determined by low-loss EELS analysis. The Eg values are then correlated with the crystal structure and the chemical properties of the films obtained by HRTEM images and VEELS line scans, respectively. They are discussed in comparison to both experimental and theoretical results published in literature. The HfO2 ALD film capped with poly-Si exhibits the largest band gap (Eg=5.9±0.5eV), as a consequence of its nanocrystallized orthorhombic structure. The large grains with a monoclinic structure formed in the HfO2 ALD film capped with Ge and the carbon contamination induced by the precursors in the HfO2 CVD film capped with Al2O3 are identified to be the main features responsible for lower band gap values (Eg=5.25±0.5 and 4.3±0.5eV respectively).

Sacrificial CVD film etch-back process for air-gap Cu interconnects

A novel sacrificial chemical vapor deposition film etch-back process for Cu air-gap interconnects was developed. The etched-back Cu surfaces were analyzed by X-ray photoelectron spectroscopy. The electrical characteristics and the stress induced voiding reliability were evaluated. The CF 4 etch-back process was found not to degrade interconnect reliability. A four-level dual damascene Cu interconnect structure was successfully fabricated, and its effective dielectric constant was 2.8, 32% lower than that of a conventionally fabricated one. In situ N 2 or Ar plasma treatments after etch-back were investigated to reduce the Cu degradation.