Characteristics of organic-inorganic hybrid plasma polymer thin films for low-κ ILD applications

This study investigated the effects of plasma power and tetraethylorthosilane (TEOS) to cyclohexene ratios on low-κ organic-inorganic hybrid plasma polymer thin films deposited on silicon (100) substrates. These films were deposited using a plasma enhanced chemical vapor deposition (PECVD) method, in addition to the electrical and mechanical properties of the resulting composites. Cyclohexene and TEOS were used as organic and inorganic precursors, respectively, with hydrogen and argon as precursor bubbler gases. Furthermore, additional argon was used as a carrier gas. The as-grown polymerized thin films were analyzed using ellipsometry, Fourier-transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The ellipsometry results showed the thickness of the hybrid thin film, and the FT-IR spectra showed that the hybrid polymer thin films were completely fragmented and polymerized between cyclohexene and TEOS. AFM results showed that polymer films with a smooth surface could be grown under various deposition conditions, while TEM and XRD showed that the hybrid thin film was an amorphous plasma polymer thin film without porosity. In addition, current-voltage (C-V) curves were prepared to calculate the dielectric constants. Post-annealing was applied to investigate the thermal stability of hybrid plasma polymer thin films in the hardness, Young's modulus, thermal shrinkage, and the dielectric constant at 400 °C.     

Contact angle analysis of low-temperature cyclonic atmospheric pressure plasma modified polyethylene terephthalate

Polyethylene terephthalate (PET) films are modified by cyclonic atmospheric pressure plasma. The experimentally measured gas phase temperature was around 30 °C to 90 °C, indicating that this cyclonic atmospheric pressure plasma can treat polymers without unfavorable thermal effects. The surface properties of cyclonic atmospheric pressure plasma-treated PET films were examined by the static contact angle measurements. The influences of plasma conditions such as treatment time, plasma power, nozzle distance, and gas flow rate on the PET surface properties were studied. It was found that such cyclonic atmospheric pressure plasma is very effective in PET surface modification, the reduced water contact angle was observed from 74° to less than 37° with only 10 s plasma treatment. The chemical composition of the PET films was analyzed by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) was used to study the changes in PET surface feature of the polymer surfaces due to plasma treatment. The photoemission plasma species in the continuous cyclone atmospheric pressure plasma was identified by optical emission spectroscopy (OES). From OES analysis, the plasma modification efficiency can be attributed to the interaction of oxygen-based plasma species in the plasma with PET surface. In this study, it shows a novel way for large scale polymeric surface modification by continuous cyclone atmospheric pressure plasma processing.     

Ellipsometric study of nanostructured carbon films deposited by pulsed laser deposition

When depositing carbon films by plasma processes the resulting structure and bonding nature strongly depends on the plasma energy and background gas pressure. To produce different energy plasma, glassy carbon targets were ablated by laser pulses of different excimer lasers: KrF (248 nm) and ArF (193 nm). To modify plume characteristics argon atmosphere was applied. The laser plume was directed onto Si substrates, where the films were grown. To evaluate ellipsometric measurements first a combination of the Tauc-Lorentz oscillator and the Sellmeier formula (TL/S) was applied. Effective Medium Approximation models were also used to investigate film properties. Applying argon pressures above 10 Pa the deposits became nanostructured as indicated by high resolution scanning electron microscopy. Above ~ 100 and ~ 20 Pa films could not be deposited by KrF and ArF laser, respectively. Our ellipsometric investigations showed, that with increasing pressure the maximal refractive index of both series decreased, while the optical band gap starts with a decrease, but shows a non monotonous course. Correlation between the size of the nanostructures, bonding structure, which was followed by Raman spectroscopy and optical properties were also investigated.     

Effects of argon and oxygen addition to the CH4-H2 feed gas on diamond synthesis by microwave plasma enhanced chemical vapor deposition

In order to investigate the effects of argon and oxygen on diamond synthesis, the behaviors of diamond deposition using microwave plasma chemical vapor deposition method have been studied by varying the concentrations of argon and oxygen in the methane-hydrogen gas mixture. Diamond films were deposited on silicon wafer under the conditions of substrate temperatures: 1073 1173 K, total reaction pressure: 5333 Pa (40 Torr), methane concentrations: 0.5 5.0%, and they were characterized by scanning electron microscopy, Raman spectroscopy and optical emission spectroscopy. The deposition rates of diamond films were enhanced by adding argon into the methane-hydrogen system, but nondiamond carbon phases in the films also increased. It resulted from the increase of hydrocarbon radicals in the plasma. As oxygen was added, the quality of deposited diamond films was improved due to the decrease of C₂ radicals and increase of OH radicals in the plasma. Simultaneous addition of 0.3% oxygen and 20% argon has been able to effectively suppress the formation of nondiamond carbon components and increase the deposition rate of diamond films. It appears that the ionized argon (Ar⁺) and excited argon atoms (Ar*) may activate the various chemical species and promote the reactions between the gas phase species and oxygen in the plasma.     

Room temperature deposition and properties of ZnO:Al thin films by nonreactive DC magnetron sputtering

Transparent and conductive ZnO:Al (AZO) thin films were prepared at room temperature by nonreactive DC magnetron sputtering from ceramic ZnO:Al targets. The effects of Al doping level and argon gas pressure on microstructure, growth behavior, resistivity and transmittance of AZO thin films were investigated. The experimental results show that AZO thin films change from polycrystalline to preferred c-axis-orientation just at high argon gas pressure. The resistivity of AZO films first decreases with the increase of Al content under 3 wt%, then increases when the Al content is over 3 wt%. The argon gas pressure also effect on the resistivity of AZO thin films due to the change of dispersion related the grain and crystal boundary. When the argon gas pressure from 0.6 to 3.0 Pa, the resistivity of AZO films decreases to a lowest resistivity of 1.4 × 10⁻³ Ω cm when the argon gas pressure is 1.5 Pa, then increases gently. The Al content and argon gas pressure had a little influence on transmittance, and the average optical transmittances of AZO thin films were from 86% to 90%, but the absorption edge has a blue shift with the increase of doping level and argon gas pressure.     

Amorphous carbon nitrogenated films prepared by plasma immersion ion implantation and deposition

In this work, an investigation was conducted on amorphous hydrogenated-nitrogenated carbon films prepared by plasma immersion ion implantation and deposition. Glow discharge was excited by radiofrequency power (13.56 MHz, 40 W) whereas the substrate-holder was biased with 25 kV negative pulses. The films were deposited from benzene, nitrogen and argon mixtures. The proportion of nitrogen in the chamber feed (R_N) was varied against that of argon, while keeping the total pressure constant (1.3 Pa). From infrared reflectance-absorbance spectroscopy it was observed that the molecular structure of the benzene is not preserved in the film. Nitrogen was incorporated from the plasma while oxygen arose as a contaminant. X-ray photoelectron spectroscopy revealed that N/C and O/C atomic ratios change slightly with R_N. Water wettability decreased as the proportion of N in the gas phase increased while surface roughness underwent just small changes. Nanoindentation measurements showed that film deposition by means of ion bombardment was beneficial to the mechanical properties of the film-substrate interface. The intensity of the modifications correlates well with the degree of ion bombardment.     

Durability of nitrided fluorocarbon polymer films for nanoimprint lithography

Hydrophobic fluorocarbon polymer films have been used as anti-sticking and releasing coatings for templates in nano-imprint lithography, but have poor durability against repeated high pressure pressing processes. The addition of nitrogen into fluorocarbon-based gas plasma can provide nitrided fluorocarbon polymer films, as confirmed by Fourier-transform infrared spectroscopy. Fluorocarbon and nitrided fluorocarbon films have almost the same 110.0° contact angle with water drops. The nitrided fluorocarbon films are harder and significantly enhance durability as anti-sticking layers. Durability enhancement has been confirmed by fabricating replicas with silicon templates using nitrided fluorocarbon anti-sticking layers.     

溅射气氛对氟碳疏水薄膜表面结构及性能的影响

以聚四氟乙烯(PTFE)为靶材,用射频磁控溅射方法在玻璃衬底上制备了氟碳高分子薄膜,并对其结构和表面性能进行了研究.由XPS的结果可知,构成薄膜的大分子由-CF-、-CF2-和-CF3等组分组成.随着氩气压强的增加,缺氟基团-C-增加,而-CF2-、-CF3等富氟基团以及F/C均减少;随着氮气偏压的增加,-CF-、-CF2-和-CF3以及F/C和N/C增加.同时探讨了溅射气氛对薄膜表面形貌、疏水性能及表面能的影响.     

Experimental investigations of semi-crystalline plasma polymerized poly(3-octyl thiophene)

Plasma polymerized thin film of conducting poly(3-octylthiophene) was deposited at room temperature by plasma enhanced chemical vapor deposition method using (3-octylthiophene) monomer as precursor. The radio frequency (RF: 13.56 MHz, power supply: 30 W) was applied at constant argon gas pressure for the formation of plasma. Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), X-ray diffractometry (XRD) and high resolution transmission electron microscopy (HRTEM) have been done for the as grown films. As reported in literature polythiophenes prepared by rf plasma polymerization are highly crosslinked and amorphous. However, in present investigations, well defined crystalline regions have been observed by HRTEM investigations and have been correlated with X-ray diffraction data. The observed crystallinity is attributed to controlling the parameters of the synthesis.     

Tailoring of the morphology and chemical composition of thin organosilane microwave plasma polymer layers on metal substrates

The growth of thin microwave organosilicon plasma polymers on model zinc surfaces was investigated as a function of the film thickness and the oxygen partial pressure during film deposition. The evolution of the topology of the film was studied by atomic force microscopy (AFM). The nano- and micro-roughness was investigated at the inner and the outer surfaces of the plasma polymers. A special etching procedure was developed to reveal the underside of the plasma polymer and thereby its inner surface. Rough films contained voids at the interface, which reduced the polymer/metal contact area. The increase in oxygen partial pressure led to a smoother film growth with a perfect imitation of the substrate topography at the interface. The chemical structure of the films was determined by infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). ToF-SIMS at the outer and the inner surface of the plasma polymers showed that the density of methylsilyl groups increases in the outer surface layer of the plasma polymer and depends on the oxygen partial pressure. The chemical composition of the films could be altered to pure SiO₂ without changing the morphology by using oxygen-plasma post-treatment. This was proved by means of IRRAS and AFM. Chemistry and topology of the films were correlated with the apparent water contact angle. It was found that a linear relationship exists between the nanoscopic roughness of the plasma polymer and the static contact angle of water. Superposition of a nanoscopic roughness of the metal surface and the nanoscopic roughness of methylsilyl-rich films led to ultra-hydrophobic films with water contact angles up to 160°.     

Hydrogenated amorphous carbon and carbon nitride films deposited at low pressure by plasma enhanced chemical vapor deposition

Hydrogenated amorphous carbon (a-C:H) films were deposited by plasma enhanced chemical vapor deposition from methane, argon diluted methane, and nitrogen diluted methane at 26.7 Pa with a 13.56 MHz RF power supply. In this pressure regime, multiple-scattering of carbon species within the plasma phase is expected during the transport to the substrates placed on both the driven and the earthed electrodes. These films were analyzed using UV-VIS optical transmittance, monochromatic ellipsometry, Raman spectroscopy and current-voltage measurements. From these results, the effect of the plasma conditions and the effective flux of the carbon species controlled by the input power through the negative self bias are found to be important in the deposition process. The growth conditions at the higher pressure regime are important to synthesize a-C:H films from low energetic carbon species, since it reduces the defect density and improves the quality of the films. Furthermore, the effect of nitrogen on the growth conditions of a-C:H:N films is observed.     

A ZnO/PET assembly study: Optimization and investigation of the interface region

Zinc oxide thin films are deposited on polyethylene terephthalate (PET) by r.f. magnetron sputtering process from a ceramic target in oxygen–argon plasmas. Structural studies show that the thin films are highly oriented along the (0 0 2) direction of the würtzite phase when the oxygen partial pressure is lower than 0.2 Pa. The crystallinity is accentuated when the oxygen partial pressure of the sputtering gas is increased from 0 to 0.02 Pa. The composition of the films determined by Rutherford backscattering spectrometry (RBS) varies in a wide range and it is necessary to add a few amount of oxygen in the plasma composition to establish the stoichiometry. The oxygen partial pressure is found to influence also the microstructure and consequently the density of the coatings.Various cold plasmas are used to treat the polymer surface before the deposition of zinc oxide films. Wettability measurements show an increase in the polar component of the PET surface free energy whatever the nature of the plasma used for the treatment. This increase is more obvious with the carbon dioxide plasma. XPS examinations of the CO₂ plasma treated PET surface in optimized conditions show a functionalisation of the polymer surface. The carbon dioxide plasma treatments of PET surface are found to enhance the peeling energy. The adhesion level depends also on the sputtering parameters, mainly the oxygen partial pressure and the r.f. power which influence the coating properties. The zinc oxide/PET interface is studied by XPS at the different stages of deposition and at various take-off angles. AFM observations show a regular growth of zinc oxide layers with smooth topographies on PET films. The different findings obtained from C1s, O1s, Zn2p3/2, Zn3p peaks and Auger Zn L₃M_4.5M_4.5 peak are corroborated and discussed. New chemical bonds between the polymer and the further coming zinc oxide thin layer are evidenced.     

Deposition and characterization of smooth ultra-nanocrystalline diamond film in CH4/H2/Ar by microwave plasma chemical vapor deposition

The smooth ultra-nanocrystalline diamond (UNCD) films were prepared by microwave plasma chemical vapor deposition (MWCVD) using argon-rich CH₄/H₂/Ar plasmas with varying argon concentration from 96% to 98% and negative bias voltage from 0 to −150 V. The influences of argon concentration and negative bias voltage on the microstructure, morphology and phase composition of the deposited UNCD films are investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), atom force microscopy (AFM), and visible and UV Raman spectroscopy. It was found that the introduction of argon in the plasma caused the grain size and surface roughness decrease. The RMS surface roughness of 9.6 nm (10 micron square area) and grain size of about 5.7 nm of smooth UNCD films were achieved on Si(100) substrate. Detailed experimental results and mechanisms for UNCD film deposition in argon-based plasma are discussed. The deposited highly smooth UNCD film is also expected to be applicable in medical implants, surface acoustic wave (SAW) devices and micro-electromechanical systems (MEMS).     

Development of amorphous carbon protective coatings on poly(vinyl)chloride

The great versatility of polymers has promoted their application in a series of ordinary situations. The development of specific devices from polymers, however, requires modifications to fit specific stipulations. In this work the surface properties of thin films grown onto polyvinylchloride (PVC) were investigated. Hydrogenated amorphous carbon films were deposited onto commercial PVC plates from acetylene and argon plasmas excited by radiofrequency (13.56 MHz, 70 W) power. The proportion of acetylene in the gas feed was varied against that of argon, keeping the total pressure constant at 2.5 Pa. Deposition time was 1800 s. Film elemental composition was analyzed by X-ray photoelectron spectroscopy, XPS. Water contact angle measurements were performed using the sessile drop technique. The root mean squared roughness was derived from 50 × 50 µm² surface topographic images, acquired by scanning probe microscopy. Nanoindentation and pin-on-disk techniques were employed on the determination of film hardness and sliding wear, respectively. Oxidation resistance was obtained through the etching rate of the samples in oxygen radiofrequency (1.3 Pa, 50 W) plasmas. From XPS analysis it was detected oxygen and nitrogen contamination in all the samples. It was also found that sp³/sp² ratio depends on the proportion of argon in the plasma. At lower argon concentrations, hardness, wear and oxidation resistances were all improved with respect to the uncoated PVC. In such conditions, the surface wettability is low indicating a moderate receptivity to water. This combination of properties, ascribed to a balance between the ion bombardment and deposition processes, is suitable for materials exposed to rigorous weathering conditions.     

Structural and morphological investigations on DC-magnetron-sputtered nickel films deposited on Si (100)

Pure nickel thin films were deposited on Si (100) substrates under different conditions of sputtering using direct current magnetron sputtering from a nickel metal target. The different deposition parameters employed for this study are target power, argon gas pressure, substrate temperature and substrate-bias voltage. The films exhibited high density of void boundaries with reduction in <111> texture deposited under high argon gas pressures. At argon gas pressure of 5 mTorr and target power of 300 W, Ni deposition rate was ~40 nm/min. In addition, coalescence of grains accompanied with increase in the film texture was observed at high DC power. Ni films undergo morphological transition from continuous, dense void boundaries to microstructure free from voids as the substrate-bias voltage was increased from −10 to −90 V. Furthermore, as the substrate temperature was increased, the films revealed strong <111> fiber texture accompanied with near-equiaxed grain structure. Ni films deposited at 770 K showed the layer-by-layer film formation which lead to dense, continuous microstructure with increase in the grain size.     

Preparation and properties of Mg0.2Zn0.8O:Al UV transparent conducting thin films deposited by RF magnetron sputtering at room temperature with rapid annealing

Mg_0.2Zn_0.8O:Al UV transparent conducting thin films were deposited by RF magnetron sputtering at room temperature with a rapid annealing process. Effects of sputtering power, argon gas pressure and annealing temperature on structure, optical and electrical properties of Mg_0.2Zn_0.8O:Al films were investigated. The experimental results show that Mg_0.2Zn_0.8O:Al thin films exhibit high preferred c-axis-orientation. The sputtering power, argon gas pressure and annealing temperature all exert a strong influence on the electrical resistivity of Mg_0.2Zn_0.8O:Al thin films due to the variation of carrier concentration and mobility in films derived from the change of effective doping and crystallinity. The lowest electrical resistivity of Mg_0.2Zn_0.8O:Al thin films is 3.5 × 10⁻³ Ω·cm when the sputtering power is 200 W, the argon gas pressure is 2.0 Pa and the annealing temperature is above 500 °C. The transparent spectrum range of Mg_0.2Zn_0.8O:Al thin films extend to ultraviolet band and the optical transmittance is between 80 and 90%, but the sputtering power, argon gas pressure and annealing temperature all exert little influence on optical transmittance.     

Excitation temperature and electron number density behavior of atmospheric pressure D.C. argon plasma jet during spheroidization of nickel

The excitation temperature and electron number density of the atmospheric pressure D.C. argon plasma jet during spheroidization of nickel have been measured at 5 mm from the nozzle exit by optical emission spectroscopic technique. Emission spectra of the argon plasma, argon plasma with carrier gas and carrier gas with nickel powder were recorded in 400-450 nm wavelength interval. The effect of carrier gas and powder loading on the excitation temperature and electron number density of the plasma jet were determined using atomic Boltzmann plot method and stark broadening of the Ar I (430.010 nm) line respectively. The experiment was done at 6.5, 7.9, 11.4 and 12.1 kW input power levels. Argon was used as plasma gas and also carrier gas. Nickel powders in the size ranging from 40 to 100 μm were processed. On introduction of carrier gas and nickel powder loading, the excitation temperature and electron density of the jet were found to decrease. From the results, the degree of ionization of the plasma jet was calculated by using the measured excitation temperature and electron density values. The spheroidzed nickel powder was characterized by SEM, optical photographs and XRD.     

射频溅射工艺参数对AZO薄膜结构和性能的影响

采用射频磁控溅射法制备了掺铝氧化锌(AZO)薄膜,研究了衬底温度及溅射工作压强对沉积薄膜的晶体结构、表面形貌及电学性能的影响。结果显示,随衬底温度增加,薄膜的结晶结构发生显著变化,而溅射工作气压增加主要影响沉积薄膜(103)面与(002)面的相对强度。薄膜的表面形貌受温度影响严重,而气压对形貌的影响相对较小。衬底温度增加,薄膜的电阻率急剧降低,迁移率和载流子浓度都显著增加,而工作气压增加则导致电阻率先减小后增大。     

Comparative study on dry etching of polycrystalline diamond thin films

The reactive ion etching (RIE) technique was used to etch polycrystalline diamond thin films. In this study we investigate the influence of process parameters (total pressure, rf power, gas composition) of standard capacitively coupled plasma RIE system on the etching rate of diamond films. The surface morphology of etched diamond films was characterized by Scanning Electron Microscopy and the chemical composition of the etched film part was investigated by Raman Spectroscopy.We found that the gas composition had a crucial effect on the diamond film morphology. The use of CF₄ gas resulted in flatter surfaces and lateral-like etching, while the use of pure O₂ gas resulted in needle-like structures. Addition of argon to the reactant precursors increased the ion bombardment, which in turn increased the formation of non-diamond phases. Next, increasing the rf power from 100 to 500 W increased the etching rate from 5.4 to 8.6 μm/h. In contrast to this observation, the rise of process pressure from 80 to 150 mTorr lowered the etching rate from 5.6 down to 3.6 μm/h.     

Structural characteristics of phosphorus-doped C60 thin film prepared by radio frequency-plasma assisted thermal evaporation technique

Phosphorus doped C60 (P:C60) thin films were prepared by a radio frequency plasma assisted thermal evaporation technique using C60 powder as a carbon source and a mixture of argon and phosphine (PH3) gas as a dopant precursor. The effects of the plasma power on the structural characteristics of the as-prepared films were then studied using Raman spectroscopy, Auger electron spectroscopy (AES) and X-ray photo-electrons spectroscopy (XPS). XPS and Auger analysis indicated that the films were mainly composed of C and P and that the concentration of P was proportional to the plasma power. The Raman results implied that the doped films contained a more disordered carbon structure than the un-doped samples. The P:C60 films were then used as a coating layer for the Si anodes of lithium ion secondary batteries. The cyclic voltammetry (CV) analysis of the P:C60 coated Si electrodes demonstrated that the P:C60 coating layer might be used to improve the transport of Li-ions at the electrode/electrolyte interface.