Gas Flow Rate Ratio Research Articles

The Performance of the Gate Electrode Using Co Thin Films Selectively Deposited on SAMs Patterns for a-Si TFT

AbstractSelective deposition of Co thin films has been developed to produce Co pattern for TFT gate electrode on glass. We have been carried out by the selective growth of Co films with combination of micro-contact printing and metal organic chemical vapor deposition (MOCVD) at low temperature below 100°C. In the first step octadecyltrichlorosilane(OTS) layer with polydimethylsiloxane(PDMS) stamps was pre-patterned on glass. The patterned OTS area created a hydrophobic surface on glass which can prohibit nucleation and growth of Co films. In the second step a MOCVD Co selective deposition examined the difference of incubation time between OTS coated glass and pure glass.We optimized Co selective deposition through working pressure, deposition temperature, and gas flow rate ratio. Root mean square (rms) of Co films deposited on glass is 2nm enough to use gate electrode.OTS pattern was decomposed by UV treatment in the range of 280 and 350nm and then trilayer(n+Si/a-Si/SiNx) was continuously created on the sample which was selectively organized Co gate electrode on glass. We fabricated thin film transistor (TFT) of inverse staggered type using selectively deposited Co gate pattern. Reflectance was used to evaluate incubation time for Co deposition time and AFM was employed to confirm selectivity of Co thin film. The subthreshold slope and on/off current ratio was 0.88 V/decade and 6x106, respectively. The electron field-effect mobility at saturation was 0.35 cm2/Vs for Vd = 9V.

Growth of high quality Ge epitaxial layer on Si(100) substrate using ultra thin Si0.5Ge0.5 buffer

ABSTRACTMethods for forming Ge epitaxial layer on Si (100) substrate have been vigorously sought due to potential applications of such structure as a virtual substrate for III-V devices on Si. Various methods were proposed to realize low threading dislocation density and smooth surface. To date, such methods involve more than one of thick (micrometer order) SiGe buffer growth process, high temperature annealing steps and CMP process, which could compromise reliability and suitability for production.In this study, we report feasibility of a thin (in the order of 10nm) SiGe buffer layer to realize pure Ge epitaxial layer with good crystalinity, low threading dislocation density, and smooth surface without high temperature annealing steps and CMP process.As a result, we achieved shorter time for growth of practical thickness of crystalline Ge on Si (100) substrate, and also get the high quality Ge epitaxial layer which has low threading dislocation density with very smooth surface.Ge epitaxial layer and underlying thin SixGe1−x buffer layer were grown on Si (100) substrate using a cold wall UHV-CVD system. Source gases of Si and Ge were Si2H6 and GeH4, respectively. No carrier gas was used for this process. SiGe buffer layer was grown on Si(100) substrate at 450 – 520˚C. Two-step growth process was employed to grow Ge epitaxial layer on the buffer layer. Ge seed layer was grown at a low temperature (350–400˚C), followed by Ge thick layer growth at a high temperature (550–650˚C). XRD, TEM, EPD, and AFM were used for characterization of Ge epitaxial layer.Optimization of growth temperature and source gas flow rate ratio enabled to obtain an effective buffer layer thinner than 10nm. The thin buffer layer realizes process time shortening, which is within 10min, and the smooth surface is realized without crosshatch structure. The buffer thickness is 1/160 to 1/1000 than that of previously known methods using thick SiGe buffer layers. Thin SiGe buffer also enabled process time shortening for Ge seed layer growth as two-dimensional Ge layer was formed faster on the thin SiGe buffer layer than on Si. XRD of the Ge seed layer showed 97% relaxation as grown and fully relaxed at 550˚C. The threading dislocation density of the top Ge layer was estimated below 1E7counts/cm2 by TEM and EPD.The misfit dislocations oriented along [110] at the interface between the SiGe buffer layer and the Ge layer and the distances are 9.5nm constantly in cross-sectional TEM image. We are checking the surface roughness of the Ge epitaxial layer by using AFM.

Design of a tri-layer bottom anti-reflective coating for KrF, ArF and F2 lithographies

We report a novel tri-layer bottom antireflective coating (BARC) design based on hexamethyldisiloxane (HMDSO) films working simultaneously at 157, 193 and 248 nm wavelengths. The required optical constant for each layer can be tuned by varying the gas flow rate ratio of oxygen to HMDSO in an electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) process. The swing effect in the resist is experimentally shown to be reduced significantly by adding this tri-layer BARC structure.

Design of a tri-layer bottom anti-reflective coating for KrF, ArF and F 2 lithographies

We report a novel tri-layer bottom antireflective coating (BARC) design based on hexamethyldisiloxane (HMDSO) films working simultaneously at 157, 193 and 248 nm wavelengths. The required optical constant for each layer can be tuned by varying the gas flow rate ratio of oxygen to HMDSO in an electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) process. The swing effect in the resist is experimentally shown to be reduced significantly by adding this tri-layer BARC structure.

A New Method for the Rapid Determination of Volatile Organic Compound Breakthrough Times for a Sorbent at Concentrations Relevant to Indoor Air Quality

The use of sorbents has been proposed to remove volatile organic compounds (VOCs) present in ambient air at concentrations in the parts-per-billion (ppb) range, which is typical of indoor air quality applications. Sorbent materials, such as granular activated carbon and molecular sieves, are used to remove VOCs from gas streams in industrial applications, where VOC concentrations are typically in the parts-per-million range. A method for evaluating the VOC removal performance of sorbent materials using toluene concentrations in the ppb range is described. Breakthrough times for toluene at concentrations from 2 to 7500 ppb are presented for a hydrophobic molecular sieve at 25% relative humidity. By increasing the ratio of challenge gas flow rate to the mass of the sorbent bed and decreasing both the mass of sorbent in the bed and the sorbent particle size, this method reduces the required experimental times by a factor of up to several hundred compared with the proposed American Society of Heating, Refrigerating, and Air-Conditioning Engineers method, ASHRAE 145P, making sorbent performance evaluation for ppb-range VOC removal more convenient. The method can be applied to screen sorbent materials for application in the removal of VOCs from indoor air.

XPS study of fluorinated diamond-like carbon films prepared by reactive magnetron sputtering

Fluorinated diamond_like carbon(F_DLC) films were prepared by radio frequency(RF) reactive magnetron sputtering with trifluoromethane (CHF3) and argon as source gases, and pure graphite as a targ et. The influence of source gas flow rate ratio on the film bonding configuration, sp2/sp3 hybrid ratios and optical band gap were investigated by Raman, Infrared transmission spectra, UV_visible spectra and XPS spectra. The results show that F-DLC films with high fluorine content, wide optical band gap and ultra-low diel ectric constant can be prepared by RF reactive magnetron sputtering technique in low input RF power (60W), high pressure (2.0Pa) and proper sour ce gas flow ratio (Ar/CHF3=2∶1).

Preparation of transparent conductive thin films by facing targets sputtering system

ZnO:Al thin films were deposited on the glass substrate by Facing Targets Sputtering apparatus with ZnO:Al (2 wt.%) and Zn targets. The influences of the ratio of gas flow rate [O 2/(Ar+O 2)] and substrate temperature have been investigated on the properties. The resistivity and optical transmittance of ZnO:Al thin films were under 1×10 −4 Ω cm and over 80%, respectively. Also, resistivity was increased with increasing of substrate temperature.

Microstructural and microtextural investigations of boron nitride deposited from BCl3–NH3–H2 gas mixtures

Abstract The structural, morphological and textural characteristics of BN coatings processed by CVD from (BCl 3 , NH 3 , H 2 ) gas mixtures, at low pressure ( P =1.3 kPa) and low temperature ( T =800 °C), with different Q NH3 / Q BCl3 gas flow rate ratios, have been investigated. Whereas the as-processed coatings are amorphous, a high degree of crystallisation can be achieved after a post-deposition heat treatment. The sole post-elaboration heat treatment does not allow the improvement of the crystallisation degree of the boron nitride. The presence of a small amount of oxygen, resulting from a simple exposure of the coating to a controlled atmosphere (temperature, moisture rate), is also necessary. For given temperature and pressure, a wide range of microstructures of the heat-treated BN coatings, from isotropic to anisotropic, can be observed by varying the Q NH3 / Q BCl3 ratio.

Simulation of an orifice scrubber performance based on Eulerian/Lagrangian method

A mathematical model based on Eulerian/Lagrangian method has been developed to predict particle collection efficiency from a gas stream in an orifice scrubber. This model takes into account Eulerian approach for particle dispersion, Lagrangian approach for droplet movement and particle-source-in-cell (PSI-CELL) model for calculating droplet concentration distribution. In order to compute fluid velocity profiles, the normal k− ε turbulent flow model with inclusion of body force due to drag force between fluid and droplets has been used. Experimental data of Taheri et al. [J. Air Pollut. Control Assoc. 23 (11) (1973) 963] have been used to test the results of the mathematical model. The results from the model are in good agreement with the experimental data. After validating the model the effect of operating parameters such as liquid to gas flow rate ratio, gas velocity at orifice opening, and particle diameter were obtained on the collection efficiency.

Effect of hydrogen remote plasma annealing on the characteristics of copper film

The effect of hydrogen remote plasma annealing on the characteristics of copper film such as resistivity, chemical composition and morphology was investigated. The hydrogen remote plasma enhanced the reflow of Cu and the preferential growth of Cu (111). With the increase of H 2 gas flow rate ratio {[H 2]/([H 2]+[N 2])}, plasma treatment time, and RF power, the resistivity of Cu film decreased due to the removal of impurity inside the film. The surface roughness decreased due to the smoothing of the surface, as the annealing time was increased up to 5 min but above that, the surface roughness increased because of agglomeration. The profile of Cu film in the trench opening became more conformal due to the enhanced reflow.

Qualitative modeling of silica plasma etching using neural network

An etching of silica thin film is qualitatively modeled by using a neural network. The process was characterized by a 23 full factorial experiment plus one center point, in which the experimental factors and ranges include 100–800 W radio-frequency source power, 100–400 W bias power and gas flow rate ratio CHF3/CF4. The gas flow rate ratio varied from 0.2 to 5.0. The backpropagation neural network (BPNN) was trained on nine experiments and tested on six experiments, not pertaining to the original training data. The prediction ability of the BPNN was optimized as a function of the training parameters. Prediction errors are 180 Å/min and 1.33, for the etch rate and anisotropy models, respectively. Physical etch mechanisms were estimated from the three-dimensional plots generated from the optimized models. Predicted response surfaces were consistent with experimentally measured etch data. The dc bias was correlated to the etch responses to evaluate its contribution. Both the source power (plasma density) and bias power (ion directionality) strongly affected the etch rate. The source power was the most influential factor for the etch rate. A conflicting effect between the source and bias powers was noticed with respect to the anisotropy. The dc bias played an important role in understanding or separating physical etch mechanisms.

Growth of stoichiometric (002) ZnO thin films on Si (001) substrate by using plasma enhanced chemical vapor deposition

ZnO thin films have been grown on Si(100) substrate by plasma enhanced chemical vapor deposition using a zinc organic source [Zn(C2H5)2] and carbon dioxide (CO2) gas mixture at 503 K. The dependence of ZnO thin film quality on the gas flow rate ratio of Zn(C2H5)2 to CO2 (GFRRZC) is studied by x-ray diffraction (XRD), optical absorption (OA) spectra, and photoluminescence (PL) spectra. An excitonic absorption peak is observed in the OA spectra, which closely depends on the GFRRZCs. The XRD spectra show that a c-axis-orientated wurtzite structure ZnO thin film with the full width at half maximum (FWHM) of 0.24° has been prepared. The PL spectra show a strong UV emission with a narrow FWHM of 105 meV at 3.289 eV with a weak deep-level defect emission around 2.5 eV, implying the formation of the stoichiometric ZnO thin films. The origin of the UV band is from the free exciton recombination testified by the temperature dependent PL spectra.

Reduction Substrate Alkaline Contamination by Utilizing Multi-Layer Bottom Antireflective Coating Structures in ArF Lithography

A new multilayer bottom antireflective coating (BARC) structure composed of TEOS oxide and silicon nitride film stacks is demonstrated for ArF lithography. The top TEOS oxide film is an NH3-contaminant-free material that can be used as an NH3 capping layer. After an oxygen plasma treatment, the multilayer structure is shown to have high thermal stability by thermal desorption spectrometry (TDS). The required optical constants of the bottom silicon nitride films can be tuned by varying the gas flow rate ratio of NH3 to SiH4 using a plasma-enhanced chemical vapor deposition process. The measured swing effect is found to be significantly reduced by adding a multilayer BARC on both silicon and aluminum film substrates. This BARC structure could also reduce the reflectance of various highly reflective substrates to less than 2%.

The photoluminescence of ZnO thin films grown on Si (1 0 0) substrate by plasma-enhanced chemical vapor deposition

High-quality ZnO thin films have been grown on a Si(1 0 0) substrate by plasma-enhanced chemical vapor deposition (PECVD) using a zinc organic source (Zn(C 2H 5) 2) and carbon dioxide (CO 2) gas mixtures at a temperature of 180°C. A strong free exciton emission with a weak defect-band emission in the visible region is observed. The characteristics of photoluminescence (PL) of ZnO, as well as the exciton absorption peak in the absorption spectra, are closely related to the gas flow rate ratio of Zn(C 2H 5) 2 to CO 2. Full-widths at half-maximum of the free exciton emission as narrow as 93.4 meV have been achieved. Based on the temperature dependence of the PL spectra from 83 to 383 K, the exciton binding energy and the transition energy of free excitons at 0 K were estimated to be 59.4 meV and 3.36 eV, respectively.

Comparison of the effects of deuterated SiN X films on GaN and GaAs rectifiers

Deuterated precursors (SiD 4, ND 3) were used for plasma enhanced chemical vapor deposition of thin SiN X passivation layers on both n-GaN and n-GaAs rectifiers. The two main plasma parameters that were found to degrade rectifier performance were gas flow rate ratio (SiD 4/ND 3) and plasma power. Larger increases in reverse breakdown voltage were observed for the GaN rectifiers compared to the GaAs diodes. The use of the deuterated precursors did not appear to reduce device degradation relative to conventional hydrogenated chemicals.

Tribological behaviour and microstructure of TiC xN (1− x) coatings deposited by filtered arc

A series of macroparticle-free TiN, TiC x N (1− x) and TiC coatings were deposited on 316 austenitic stainless steel using a titanium target in a filtered arc deposition system (FADS) and reactive mixtures of N 2 and/or CH 4 gases. The surface topography, chemical composition and microstructure of these coatings were characterised by optical microscopy (OM), atomic force microscopy (AFM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The microhardness has been measured and the adhesion of the coatings has been evaluated. Further, the wear and friction behaviour of the coatings were assessed under controlled test conditions in a pin-on-disc tribometer. The results show a significant increase in surface roughness, microhardness and wear resistance as the CH 4:N 2 gas flow rate ratio is increased. The composition of the coatings was strongly dependent on reactive gas flow rate during deposition. Surface particles were observed on high carbon content coatings and subsequently determined to be carbonaceous particles by using OM, AFM and EDS. At lowest load (10 N), all coatings exhibited low friction and wear. At loads of 15 and 25 N, the higher carbon content TiCN and TiC coatings showed a much lower friction and wear compared to TiN and low carbon TiCN.

Growth of high quality ZnO thin films at low temperature on Si(100) substrates by plasma enhanced chemical vapor deposition

High quality ZnO thin films with a c-axis-orientated wurtize structure have been grown on a Si(100) substrate by plasma enhanced chemical vapor deposition using a zinc organic source [Zn(C2H5)2] and carbon dioxide (CO2) gas mixture at low temperature. The dependence of ZnO thin-film quality on the gas flow rate ratio of Zn(C2H5)2 to CO2 (GFRRZC) is studied by x-ray diffraction (XRD), optical transmission spectra (OTS), and photoluminescence spectra (PL). The optical properties show that the GFRRZC has an obvious effect on the band gap of ZnO films. The relationship between the quality of the ZnO thin films and the substrate temperatures is also studied by XRD and PL spectra. The XRD spectra show that the full width at half maximum (FWHM) of the diffraction peak at 34.42° of (0002) oriented ZnO is 0.25° at the optimized condition, indicating the formation of high quality ZnO films. The PL spectra show a strong excitonic emission at about 3.26 eV without the emission around 2.5 eV related to deep-level defects, implying the formation of the stoichiometric ZnO thin films. The smallest FWHM of the PL spectrum of a ZnO thin film is 111 meV at room temperature.

High quality ZnO thin films grown by plasma enhanced chemical vapor deposition

High quality ZnO thin films have been grown on a Si(100) substrate by plasma enhanced chemical vapor deposition using a zinc organic source [Zn(C2H5)2] and carbon dioxide (CO2) gas mixtures at the low temperature of 180 °C. The dependence of ZnO thin film quality on the gas flow rate ratio of Zn(C2H5)2 to CO2 (GFRRZC) is studied by using x-ray diffraction (XRD), optical absorption (OA) spectra, and cathodoluminescence (CL) spectra. High quality ZnO thin films with a c-axis-oriented wurtzite structure are obtained when the GFRRZC is 0.33. XRD shows that the full width at half maximum of (0002) ZnO located at 34.42° is about 0.2°. At room temperature, a pronounced free exciton absorption peak around 365 nm is clearly observed. Also, a strong free exciton emission without deep level defect emission is observed around 385 nm, and its temperature dependence is studied from the photoluminescence spectra. These observations indicate the formation of a high quality ZnO film. Additionally, nitridation of the Si surface caused by releasing NH3 plasma into the deposition chamber is an effective way to improve film quality.

Feasibility of utilizing hexamethyldisiloxane film as a bottom antireflective coating for 157 nm lithography

The feasibility of utilizing a bottom antireflective coating (BARC) layer composed of hexamethyldisiloxane (HMDSO) film for 157 nm lithography is studied. The vaporized liquid HMDSO is used as a coating material in a conventional electron cyclotron resonance-plasma enhanced chemical vapor deposition process. The required optical constants of suitable HMDSO films can easily be tuned by adjusting the gas flow rate ratio of O2 to HMDSO. The swing effect is experimentally shown to be reduced significantly on Si substrates by applying either a single layer BARC or a bilayer BARC. Additionally, the bilayer BARC is shown by simulation to be capable of providing larger thickness-controlled tolerances than a single layer BARC.

Capacitance-Voltage Characterization of LPCVD-Silicon Oxynitride Films

LPCVD-silicon oxynitride films with different compositions were deposited on n-Si(111) substrates by reacting dichlorosilane (SiH 2 Cl 2 ) with nitrous oxide (N 2 O) and ammonia (NH 3 ) at a temperature of 860 °C varying the gas flow rate ratio of N 2 O and NH 3 . The electrical properties of the SiO x N y films were studied by analysis of the 1 MHz capacitance-voltage characteristics of the metal-SiO x N y -silicon capacitors. It has been found that with increasing amount of N 2 O in the deposition ambient the concentration of the dielectric charges in the SiO x N y /Si structures goes through a minimum, while the interface trap density gradually decreases. The nature of the defects is discussed.