Cyclotron Resonance Plasma Chemical Vapor Research Articles

Elastic loading enhanced NH3 sensing for surface acoustic wave sensor with highly porous nitrogen doped diamond like carbon film

We proposed a surface acoustic wave (SAW) NH3 gas sensor based on nitrogen doped diamond like carbon (N-DLC) film. The N-DLC film, prepared using a microwave electron cyclotron resonance plasma chemical vapor deposition (ECR-PECVD) method, is highly porous and physically and chemically stable, and have active polar groups on its surface, which can selectively absorb polar NH3 gas molecules. These features of the film lead to the high sensitivity, low noise and excellent stability of the sensor. The sensor can achieve capabilities of in-situ monitoring NH3 in a concentration range from 100 ppb to 100 ppm with fast response (∼5 s) and recovery (∼29 s) at room temperature. The NH3 sensing mechanism is attributed to the decreased porosity of the N-DLC film caused by adsorbed NH3 molecules on its polar groups, which leads an increase of the elastic modulus of the film.

Characterization of (100)-Dominantly Oriented Poly-Si Thin Film Transistors Using Multi-Line Beam Continuous-Wave Laser Lateral Crystallization

(100)-dominantly oriented poly-Si film was realized by using multi-line beam (MLB) continuous-wave laser lateral crystallization (CLC) with overlapping. Si grains were developed along laser scanning direction with an average grain size of approximately 20 μm x 2 μm. The fabricated TFTs have high field effect mobility up to 1010 cm2/Vs. In this work, the device characteristics of the fabricated TFTs are investigated. Fabrication process of the poly-Si TFTs are as follows: A buffer SiO2 layer of 1 μm thickness was deposited on a quartz substrate by Plasma-Enhanced Chemical Vapor Deposition (PECVD). Sequentially, an amorphous Si (a-Si) film of 150 nm thickness and a cap SiO2 of 100 nm thickness were deposited by PECVD. The films were dehydrogenated by furnace annealing at 490 oC in N2 ambient for an hour before crystallization with MLB-CLC (wavelength: 532 nm, laser power: 6 W). The laser beams scanned the sample at a speed of 0.8 cm/s with an overlapping ratio of 83%. After the cap SiO2 layer was etched by buffered hydrofluoric acid (BHF) solution, the poly-Si active layer was patterned using lithography and dry etching (Cl2: 20 sccm, HBr: 20 sccm). Gate oxide SiO2 of 42 nm thickness was deposited by Electron cyclotron Resonance (ECR) Plasma Chemical Vapor Deposition (SiH4: 0.6 sccm, O2: 10 sccm, Ar: 40 sccm) and Mo gate electrode of 300 nm thickness was deposited by sputtering. Patterning gate electrodes was carried out by lithography and wet etching (H3PO4:HNO3:CH3COOH:H2O = 400:25:50:25), followed by self-aligned source and drain formation by As ion implantation (ion dose: 2 x 1015 cm-2, accelerating voltage: 66 kV) using the Mo gate as mask. Activation annealing treatment was performed at 550 oC in N2 ambient for 30 minutes. Before SiO2 insulator film of 600 nm was deposited by Atmospheric Pressure Chemical Vapor Deposition (APCVD), sacrificial SiO2 in source and drain region was etched by BHF. Contact hole was formed by lithography and BHF wet etching. Mo metal pad of 700 nm thickness was deposited by sputtering and patterned by lithography and wet etching. Finally, the sample was annealed at 400 oC in H2 ambient for 30 minutes. The highest temperature of the fabrication processes was 550 oC. The devices were designed with the width and length of channel of W = 10 µm and L = 10 µm, respectively. Figure 1 shows microphotograph of poly Si film and schematic of TFT designed mask. This result reveals that poly-Si film was periodic in 200 µm and the channels were fabricated parallel with scanning direction in 10 groups at different positions. In particular, TFTs of group 1 were fabricated along heavy-void regions and distance of two consecutive groups was 20 µm in perpendicular direction of laser scan. Figure 2 shows an EBSD mapping of the laser-crystallized poly-Si films. It was found that (100) Si crystal grains with an average size of 20 µm x 2 µm were formed. In this figure, crystal orientation of the poly-Si film was different from the middle to the side of the measured region. As result, characteristics of TFTs was relatively different in each group. Table I indicates average mobility, maximum mobility, and variation of TFTs in 10 groups. TFTs with ultrahigh electron field effect mobility (µFE ) of over 1000 cm2/Vs in a linear region was realized. A high average electron field effect mobility of 636 cm2/Vs and its low variation of 25% were achieved in group 7 in which (100) Si crystal grains were dominant. Figure 3 shows IDS-VGS characteristics of poly Si TFTs in group 7. A high off-leakage current and its high variation of 10-10 – 10-6 were observed owing to trap states in both the grain boundaries and crystal grains. Table I.Average mobility of TFTs and their variation in each group Group Average mobility (cm2/Vs) Maximum mobility (cm2/Vs) Standard deviation (cm2/Vs) 1 2 3 4 5 6 7 8 9 10 270 490 453 476 510 590 636 600 632 618 512 1010 780 717 697 873 971 940 973 808 114 264 131 148 79 167 159 194 183 118 Figure 1

Mechanical characterisation of Si–C–N thin films prepared by electron cyclotron resonance plasma chemical vapour deposition at low microwave power and low temperature

Si–C–N thin films with smooth surfaces were synthesised by electron cyclotron resonance plasma chemical vapour deposition at low microwave powers without heating silicon substrates. Mechanical properties of obtained films were examined by nanoindentation based on Oliver and Pharr method. High elastic recovery was observed. Hardness and reduced modulus show no clear relation with the elastic/plastic work calculated from load–displacement curves. The energy dissipation kept almost constant with respect to the variation of stiffness during loading and unloading process. This opens the possibility of potential industrial applications due to the insensitivity of the deposited films to external stress.

Mechanical and electrical properties of GeSb2Te4 film with external voltage applied

A GeSb2Te4 (GST) film was deposited by RF magnetron sputtering with microwave electron cyclotron resonance plasma chemical vapor deposition equipment. Mechanical and electrical properties together with the morphologies of the film were studied by a nanoindenter which was equipped with nano-electrical contact resistance (nano-ECR) tool and atomic force microscope (AFM). Results show that when no voltage applied between sample and indent tip during indenting, the pile-up phenomenon was observed, the hardness and elastic modulus increases with the load mainly due to the underestimate of the contact area; when external voltages of −7V, −8V, −9V, −10V were applied, the resistance of the film decreased with applied voltages in about four orders of magnitude, while the elastic modulus increased from 159GPa to 233GPa, this changing in mechanical and electrical properties demonstrated that phase change happen during intending, a shrinking region with radius of about 2.5μm was observed around the indentation when −8V applied. Furthermore, indent load can also promote the phase change at given negative voltage.

Surface plasmon resonance detection using amorphous carbon/Au multilayer structure

Surface plasmon resonance (SPR) can be used to detect the change in reflective index on a metal surface. In this report, we propose detection of the SPR can easily be applied to estimate the thickness of the amorphous carbon ( a-C:H) films. To detect changes in film thickness using SPR, devices with an a-C:H/Au structure were fabricated. The a-C:H films were deposited by electron cyclotron resonance plasma chemical vapor deposition (ECR-CVD) and sputtering, and the obtained film densities were 1.4 and 1.6 g/cm 3, respectively. By the deposition of an 11-nm thick a-C:H film on a Au layer by sputtering, the SPR angle changed from 44.90° to 47.05°. For a-C:H deposited by ECR-CVD, the SPR angle was shifted from 44.24° for Au without the a-C:H layer to 58.44° after deposition of 45 nm thick a-C:H film. In both systems of the SPR angle increased with increasing the film thickness. The rate at which the SPR angle shifted depended on the a-C:H film density. These results show that the thickness of an a-C:H film can be determined by the SPR angle shift on an a-C:H layer using a-C:H/Au device with an a-C:H film of the same density.

I-V characteristics of multi-walled carbon nanotubes synthesised using ECR-CVD

Multi-walled carbon nanotubes (MWCNTs) are synthesised at a temperature of 650°C and 700°C by electron cyclotron resonance plasma chemical vapour deposition (ECR-CVD). These MWCNTs have been grown on Si substrate using a thin film of Fe as a catalyst, which is coated by RF-sputtering. Acetylene is used as a source of carbon and plasma was created by argon gas. Ammonia is used to etch away amorphous carbon produced by plasma exposure. From the SEM image, it was observed that the length and diameter of MWCNTs varies from 70 nm to 150 nm and 35 nm to 40 nm respectively. The I-V characteristics have been performed by two-probe method under a vacuum of 10−3 torr at room temperature. On the basis of I-V characteristics, it is concluded that these CNTs show the semiconducting behaviour at all the temperatures.

Effect of Substrates on Film Hardness Measurements of Nanometer Thick Amorphous Carbon Films

Amorphous carbon film (a-C:H) applications, such as hard disks, require films with nanometer thicknesses. In an indentation test, the obtained hardness values of these films are affected by substrates. On the indentation tests, we studied the effect of substrate hardness on films less than 200 nm in thickness. a-C:H and Si doped a-C:H (a-C:Si:H) films were deposited by electron cyclotron resonance plasma chemical vapor deposition onto aluminum (Al) and silicon (Si) substrates. The film thicknesses were approximately 140 nm. The hardnesses of the a-C:H film and substrates were obtained using a high-resolution indentation tester (pico-dentor) with a Vickers tip whose depth resolution was 0.04 nm. Maximum indentation loads were varied from 0.01 to 0.5 mN. The Martens hardnesses of films on the Al and Si substrates were 600 and 7000 N/mm2, respectively. On the a-C:Si:H film deposited on the Al substrate, the hardnesses increased from 1600 to 3900 N/mm2 with decreasing indentation load. The hardnesses of the films deposited on the Si substrate decreased from 5300 to 3500 N/mm2 when the maximum indentation loads were reduced. The effect of the substrates increased with the maximum load increasing. From these findings, the actual hardness value was determined to be 3600 N/mm2. These results indicate that the high-resolution indentation test achieved hardness estimations for nanometer-thick films with certain hardnesses.

極薄ダイヤモンドライクカーボン（ＤＬＣ）膜のナノメータスケールの力学特性評価

Nanometer-scale mechanical properties of extremely thin DLC films deposited using filtered cathodic vacuum arc (FCVA) and electron cyclotron resonance plasma chemical vapor deposition (ECR-CVD) methods were evaluated. Auger electron spectroscopy (AES) revealed these DLC films' thickness and composition. Results showed that the obtained DLC films' thickness nearly corresponds to the set thickness. Nanoindentation hardness and nanowear resistance of the DLC films were investigated using atomic force microscopy (AFM). The nanoindentation hardness of 100-nm-thick DLC films deposited using FCVA and ECR-CVD were 57 GPa and 25 GPa, respectively, as evaluated at 40 μN load. The difference of nanoindentation curves of 5- and 2-nm-thick DLC films deposited using FCVA and ECR-CVD methods is only slightly detectable. It is difficult to evaluate the ultrathin DLC films' hardness using a nanoindentation test of several nanometers' thickness. In contrast, mechanical properties of the extremely thin DLC films can be clarified using nanowear testing with AFM. Wear depths of 100-, 5-, 2-nm-thick FCVA-DLC films are all less than 1 nm: extremely shallow. Especially, the wear depth of 100-nm-thick FCVA-DLC film is nearly 0.1 nm, even at 30 μN load. However, the wear depths of 100-, 5-, 2-nm-thick ECR-CVD-DLC films are greater than those of FCVA-DLC films. These results underscore the excellent wear resistance of extremely thin FCVA-DLC films.

Optical and mechanical properties of diamond like carbon films deposited by microwave ECR plasma CVD

Diamond like carbon (DLC) films were deposited on Si (111) substrates by microwave electron cyclotron resonance (ECR) plasma chemical vapour deposition (CVD) process using plasma of argon and methane gases. During deposition, a d.c. self-bias was applied to the substrates by application of 13·56 MHz rf power. DLC films deposited at three different bias voltages (−60 V, −100 V and −150 V) were characterized by FTIR, Raman spectroscopy and spectroscopic ellipsometry to study the variation in the bonding and optical properties of the deposited coatings with process parameters. The mechanical properties such as hardness and elastic modulus were measured by load depth sensing indentation technique. The DLC film deposited at −100 V bias exhibit high hardness (∼ 19 GPa), high elastic modulus (∼ 160 GPa) and high refractive index (∼ 2·16–2·26) as compared to films deposited at −60 V and −150 V substrate bias. This study clearly shows the significance of substrate bias in controlling the optical and mechanical properties of DLC films.

X-ray reflectivity studies on DLC films deposited by microwave ECR CVD: Effect of substrate bias

Diamond like carbon (DLC) films were deposited at room temperature on Si (111) substrates by microwave electron cyclotron resonance (ECR) plasma chemical vapor deposition (CVD) process using plasma of methane diluted with argon gas. During deposition, dc self bias (− 25 V to − 200 V) on substrate was varied by application of RF power to the substrate. The influence of substrate bias on density of the deposited films was studied by X-ray reflectivity (XRR). The results from these measurements are further correlated with the results from UV and visible Raman spectroscopy. DLC film is modeled as a structure having three different layers such as low density surface, bulk and interface with the substrate. This three-layer model is used to fit the measured XRR data to evaluate the surface, interface and interlayer roughness, thickness and density of these films. The surface roughness obtained from XRR is correlated with the results from Atomic Force Microscopy (AFM) measurements. The observed results are explained based on the subplantation model for DLC film growth.

Hydrogenated amorphous carbon nitride with controlled hydrogen density — Structural analysis and electric field emission property

Hydrogenated amorphous carbon nitride films that include presumably oxygen atoms were prepared by using the electron cyclotron resonance (ECR) plasma chemical vapor deposition (CVD) of mixed gases of He, BrCN, and H2O. By controlling the partial pressure of H2O, the relative number density of the hydrogen atoms was varied. The IR-band intensity analysis suggested that 7–22% of N atoms were incorporated into CN terminations bonding to the aromatic rings and that the NHy (y=1 or 2) or OH terminations formed hydrogen bonds. The films were coated onto Al-doped ZnO (ZnO:Al) single crystal whiskers to manufacture cold cathode devices. The I–V characteristics of the devices were the Fowler–Nordheim type, and the work functions were determined to be 4.7±0.4–1.9±0.1 eV being dependent negatively on the partial pressure of H2O.

Mechanical properties of diamond like carbon coatings prepared by microwave electron cyclotron resonance plasma chemical vapour deposition process

Diamond like carbon coatings were deposited on Si (111) substrates under the influence of dc bias developed on the substrates by application of 13.56 MHz rf, using fixed ratio of flow rates of argon and methane gases. The deposited coatings were characterized by Raman spectroscopy that confirms the presence of DLC in deposited coatings. FTIR characterization was done to investigate the C-H bonding in the coatings. Mechanical properties such as Young's modulus (E), hardness (H) and critical load (Lc) for coating delamination have been determined through use of nanoindentation and nanoscratch techniques. The effect of the substrate bias voltage on the mechanical properties of the deposited DLC films is studied. The results indicate that mechanical properties of DLC are sensitive to the bias applied to substrate and there is an optimum substrate bias voltage for deposition of the coatings with desirable properties.

Evolution of Structural Defects in SiOx Films Fabricated by Electron Cyclotron Resonance Plasma Chemical Vapour Deposition upon Annealing Treatment

We study the structural defects in the SiOx film prepared by electron cyclotron resonance plasma chemical vapour deposition and annealing recovery evolution. The photoluminescence property is observed in the as-deposited and annealed samples.[-SiO3]2− defects are the luminescence centres of the ultraviolet photoluminescence (PL) from the Fourier transform infrared spectroscopy and PL measurements. [-SiO3]2− is observed by positron annihilation spectroscopy, and this defect can make the S parameters increase. After 1000°C annealing, [-SiO3]2− defects still exist in the films.

Study on the electron cyclotron resonance plasma chemical vapor deposition of carbon nanotubes

In this paper, the carbon nanotubes growth on porous silicon substrates by electron cyclotron resonance plasma chemical vapor deposition (ECR-CVD) method are studied as the function of the flow ratio of CH 4/(H 2 + CH 4), the total pressure in vacuum chamber and the substrate temperature. The results showed that the flow ratio of CH 4/(H 2 + CH 4) and the total pressure are the key factors on the concentration of carbon radical in the chamber, which will influence the growth rate, the density and the orientation of carbon nanotubes. The outer diameters of carbon nanotubes could be controlled by changing the substrate temperatures, it was shown that the aligned carbon nanotubes cannot be formed at lower temperature.

Surface-Enhanced Raman Spectroscopy Using Self-Assembled Silver Nanoparticles on Silicon Nanotips

A new substrate for surface-enhanced Raman spectroscopy has been developed in the form of silicon nanotips, by electron cyclotron resonance plasma chemical vapor deposition, with apex diameters of ∼2 nm, lengths of 1000 nm, and densities of 1011/cm2. The surface areas of the nanotips are ∼150 m2cm-3, comparable with the best-quality porous silicon. Ion-beam-sputtered silver self-assembles on these substrates as nanoparticles of 4−10 nm diameter and these metallic nanoparticles act as surface enhancement centers for Raman spectroscopy. Standard molecules such as Rhodamine 6G and trans-1,2-bis(4-pyridyl)ethylene (BPE) of concentrations in the range of 10-6 to 10-10 M have been studied on these substrates and enhancements in the range of 106 to 108 were observed. These dry etched substrates, unlike those conventionally prepared by wet chemistry, are compatible with silicon device technology and are remarkably stable and reproducible.

Optical gap of fluorinated amorphous carbon films prepared by electron cyclotron resonance trifluromethane and benzene plasmas

The optical gap of fluorinated amorphous carbon (a-C:F) films, which were prepared by electron cyclotron resonance plasma chemical vapor deposition using trifluromethane (CHF 3) and benzene (C 6H 6) as the source gases, is investigated. The optical gap E g of the a-C:F films, which were deposited at input microwave power of 140–700 W, pressure of 0.1–1.0 Pa and CHF 3/C 6H 6 flow ratio of 1:1–10:1, is in the range of 1.76–3.98 eV and is dependent on the amount of fluorine and CC bonding in the films. The optical gap E g increases with raising the amount of fluorine but decreases as the amount of CC bonding increased. This is because of the decrease in the amount of π bonding formed by CC and the increase in that of σ bonding formed by CF. As a result, the density of state near band edgy reduces and the optical gap becomes wide.

Self assembled gold and silver nanoparticulates on silicon nanotips as surface enhanced Raman active substrates

AbstractSilicon nanotips, grown via electron cyclotron resonance plasma chemical vapour deposition, with apex diameters of ∼2nm and lengths of 1000 nm and densities of 1011/cm2 were used as a new substrate for surface enhanced Raman spectroscopy. Ion beam sputtered gold and silver self assemble on these substrates as nanoparticulates of 4–10 nm diameter and these metallic nanoparticulates assist in the surface enhancement of Raman signals of analytes. Molecules such as Rhodamine 6G and bis-Pyridyl ethylene of varied concentrations, in the range of 10-6-10-10 M, has been studied on these substrates and enhancements in the range of 106-108 were observed.

Effect of dilution gas on SiCN films growth using methylamine

Methylamine (CH 3NH 2) was employed with SiH 4 to deposit amorphous silicon carbon nitride films due to its easy dissociation as well as containing both carbon and nitrogen elements. The effect of dilution gas, such as H 2, N 2, Ar and He on the film growth was studied in electron cyclotron resonance plasma chemical vapor deposition (CVD) reactor. At a microwave power of 250 W and a substrate temperature of 700 °C, ternary silicon carbon nitride film has been successfully deposited using He as dilution gas. However, only binary silicon nitride films were formed using dilution gases of Ar, N 2 and H 2 but otherwise similar conditions. Characterization of the films using FTIR, XPS and optical emission study of the plasma were employed to study the growth process. Possible explanations and discussion for the growth behaviors of the dilution gases are presented.

The Structure and I-V Property of a-C:F Thin Film

Fluorinated amorphous carbon (a-C:F) thin film has been deposited by microwave electron cyclotron resonance plasma chemical vapor deposition (ECR-CVD) using C6H6 and CHF3 as source gases. The result of x-ray photoelectron spectroscopy (XPS) shows that the main bonds in the film as-deposited are C-C, C-F and CF2. The measurement of postive I-V property indicates that the conductance of the film presents Omic characteristic at a lower electric field, and follows Schotty emission at a higher electric field.

Bonding characterization and nano-indentation study of the amorphous SiC xN y films with and without hydrogen incorporation

The hardness and effective modulus of hydrogen-containing and hydrogen-free amorphous SiC x N y films were studied by nano-indentation. Amorphous SiC x N y films with and without hydrogen were deposited by electron cyclotron resonance plasma chemical vapor deposition (ECR-CVD) using a SiH 4–CH 3NH 2–N 2–H 2 gas mixture and hydrogen-free ion-beam sputtering deposition (IBSD), respectively. Fourier-transform infrared spectroscopy (FTIR) studies were used to investigate the bonding states of the SiC x N y materials. SiH, CH and NH bonds were detected by FTIR in ECR-CVD, but not in IBSD, films. The incorporation of hydrogen led to a reduction in both the hardness and modulus of the amorphous SiC x N y films. From nano-indentation measurements, the hardness and effective modulus of the IBSD coated, hydrogen-free amorphous SiC x N y films were 27–30 and 211–258 GPa, respectively. The corresponding values for the ECR-CVD coated, hydrogen-containing amorphous SiC x N y were 22–26 and 115–144 GPa, respectively.