Electron Cyclotron Resonance Plasma Chemical Vapor Deposition 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.

Regulating the uniformity of DLC films in ECR plasma with negative substrate biasing

Diamond-like carbon (DLC) films were deposited by electron cyclotron resonance plasma-chemical vapor deposition (ECR-CVD) at different substrate bias potential (Us = −200 and −800 V). The mechanical properties and microstructure uniformity of the DLC films deposited at different positions (the distance between substrate and ECR plasma source, Decr-s) were studied. The results showed that the ionization of acetylene (C2H2) at different positions decreased with the increase of Decr-s at substrate bias potential Us = −200 V. The plasma distribution was non-uniform, so the mechanical properties and structure of the DLC films varied a lot with the change of deposition position. At substrate bias potential Us = −800 V, an additional self-sustained discharge around the substrate could be generated during ECR plasma discharge, then the ionization of C2H2 and the plasma distribution uniformity at different positions were found to be improved. The uniformity of mechanical properties and structure of DLC films could be improved due to enhanced ionization of C2H2 in front of the substrate at high values of the negative substrate bias (Us = −800 V).

Magnetic properties of Co-N films deposited by ECR nitrogen/argon plasma with DC negative-biased Co target

By introducing DC negative-biased Co target in the Electron Cyclotron Resonance (ECR) nitrogen/argon plasma, the Co-N films containing Co4N phase were synthesized on Si(100) substrate. Effects of processing parameters on magnetic properties of the films are investigated. It is found that magnetic properties of Co-N films vary with N2/Ar flow ratio, substrate temperature, and target biasing voltage. The saturation magnetization Ms decreased by increasing the N2/Ar gas flow ratio or decreasing target biasing voltage, while the coercive field Hc increased, which is ascribed to the variation of relative concentration for N or Co active species in plasma vapor. The magnetic properties present complex dependency with growth temperature, which is related to the atom mobility on the substrate affected by the growth temperature. This study exhibits a potential of ECR plasma chemical vapor deposition to synthesize the interstitial compounds and tune magnetic properties of films.

Formation and Characterization of Strained Si1-XGex Films Epitaxially Grown on Si(100) by Low-Energy ECR Ar Plasma CVD without Substrate Heating

For quantum-effect nano heterostructures of group IV semiconductors, formation and characterization of Si1-xGex films epitaxially grown on Si(100) by using low-energy electron-cyclotron-resonance (ECR) Ar plasma chemical vapor deposition (CVD) without substrate heating were investigated. Epitaxial Si0.50Ge0.50 films with smooth surface can be obtained on Si(100), where the thickness is almost proportional to deposition time and an incubation period is scarcely observed. For a 12 nm-thick epitaxial Si0.50Ge0.50 film on Si(100), its lattice constant in the direction perpendicular to the interface shows that the lattice is highly strained compared to a case of strain-relaxed Si0.50Ge0.50. This indicates that our ECR plasma CVD process has a potential to achieve highly strained heterostructures with suppressed strain relaxation and thermal interdiffusion at the heterointerface which are necessary for quantum-effect devices.

Diagnostics of downstream microwave electron cyclotron resonance (ECR) plasma

Diagnostics of downstream plasma generated in a microwave ECR plasma chemical vapour deposition (CVD) facility (a 2.45 GHz, 1.5 KW) is done using a Langmuir probe. The probe is inserted near the substrate location (640 mm away from main ECR zone). The objective is to see the extent of uniformity in the plasma parameters of generated plasma near the substrate location. For this purpose I-V probe characteristics were recorded at four different operating pressures for four different power levels for each pressure to cover the operating range of parameters that are used during thin film deposition. Data was analysed to obtain the radial electron energy distribution function (EEDF) and radial variation of plasma parameters such as electron number density (ne), average electron energy (<E>), and plasma potential (Vp). Ion number density (ni) was also estimated by Orbital Motion Limited Theory (OML) using a Graphical User Interface (GUI) developed for this purpose and compared with ne calculated from electron energy distribution function (EEDF). The results obtained by the different methods are compared and observed differences are explained.

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.

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.

Study of Amorphous Carbon Nitride Films Aiming at White Light Emitting Devices

The possibility for white light emitting devices using carbon nitride (CNx) thin films has been studied. Microwave electron cyclotron resonance (ECR)–plasma chemical vapor deposition (CVD) and RF-sputtering apparatuses have been used for the formation of CNx thin films. In both cases, CH4 was used as the source or sub-source of carbon in order to investigate the effect of hydrogenated carbon nitride for luminescence. The cathodoluminescence (CL) measurement of the film grown by ECR–plasma CVD method showed three peaks of red, green, and blue (R/G/B). The photoluminescence (PL) measurement of the film grown by RF-sputtering also showed the red peak, which could not be observed in the film without hydrogen. Together with the X-ray photoelectron spectroscopy (XPS) analysis data, we concluded that the red peak originates from the level relating to H atom and blue peak from C–N bonds.

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.

Epitaxial growth of highly strained Si on relaxed Ge/Si(1 0 0) using ECR plasma CVD without substrate heating

By using electron-cyclotron resonance (ECR) plasma chemical vapour deposition (CVD), epitaxial growth of highly strained Si on 84%-relaxed Ge/Si(1 0 0) without substrate heating has been investigated. For a Si thickness of 1.7 nm, the deposited surface is atomically flat, and the strain (ratio of change in the lattice constant to strain-free lattice constant) is about 4%. This value indicates that the strained Si lattice is matched to the relaxed Ge lattice. Furthermore, it is found that the heterostructure of strained Si/Ge is thermally stable up to 600 °C.

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.

Evaluation of fracture toughness of ultra-thin amorphous carbon coatings deposited by different deposition techniques

The successful performance and reliability of thin coatings is often limited by their mechanical properties. Generally, harder coatings are more brittle and easily damaged by shock loads in practical applications. A necessary criterion for evaluating brittleness of thin coatings is to measure fracture toughness of the coatings. In this paper, the nanoindentation fracture of ultra-thin (100 nm thick) amorphous carbon coatings on Si substrate deposited by filtered cathodic arc (FCA), direct ion beam (IB), electron-cyclotron resonance plasma chemical vapor deposition (ECR-CVD), and sputter (SP) deposition processes was studied using a cube corner indenter. Based on the analysis of the energy release in cracking, the fracture toughness of the coatings was calculated. It is found that among the coatings tested, the FCA coating has the highest fracture toughness, followed by the ECR-CVD, IB, and SP coatings. The higher deposition kinetic energy, plasma density and electron temperature are believed to be responsible for the higher fracture toughness values for the FCA and ECR-CVD coatings.

Crystalline SiCN: a hard material rivals to cubic BN

Growth and mechanical properties of SiCN materials prepared by microwave plasma enhanced chemical vapor deposition (CVD) as well as electron cyclotron resonance plasma CVD are reported. Large (several tens of microns), well-faceted ternary SiCN crystals were grown by microwave plasma-enhanced chemical vapor deposition, whereas amorphous SiCN films were deposited by ECR-CVD. The ternary crystalline compound (C; Si)xNy exhibits a hexagonal structure and consists of a network wherein the Si and C are substitutional elements. While the N content of the crystalline compound is about 50 at.%, the extent of Si substitution varies and can be as low as 10 at.%. The amorphous SiCN films contain only about 30 at.% N. Nano-indentation studies were employed to investigate the mechanical properties of the SiCN materials. From the load versus displacement curves, we estimated the hardness and the effective modulus of the SiCN crystals to be around 30 and 321.7 GPa, respectively. The corresponding values for the amorphous SiCN were around 22 and 164.4 GPa, respectively. These values are well above most reported values for CN films.

Micro/nanomechanical and tribological characterization of ultrathin amorphous carbon coatings

Micro/nanomechanical and tribological characterization of ultrathin amorphous carbon coatings, deposited by filtered cathodic arc (FCA), direct ion beam (IB), electron cyclotron resonance plasma chemical vapor deposition (ECR-CVD), and sputter (SP) deposition processes on Si substrate have been conducted using a nanoindenter with a nanoscratch attachment and an accelerated ball-on-flat tribometer. Coating thicknesses of 20, 10, 5 nm and, for the first time, 3.5 nm coatings have been investigated. It was found the FCA coating exhibits the highest hardness and elastic modulus, followed by the ECR-CVD, IB, and SP coatings. In general, the thicker coatings exhibited better scratch/wear performance than the thinner coatings due to their better load-carrying capacity as compared to the thinner coatings. At 20 nm, the FCA and ECR-CVD coatings show the best scratch and wear resistance, while the IB and ECR-CVD coatings show the best scratch and wear resistance at 10 nm. Five nanometer thick coatings show reasonable scratch and wear resistance, while 3.5 nm thick coatings show extremely low load-carrying capacity and poor scratch and wear resistance. It appears that the 3.5 nm coatings studied are unfeasible for scratch and wear resistance applications as of now.

Micro/nanotribology of ultra-thin hard amorphous carbon coatings using atomic force/friction force microscopy

Microscale scratch and wear resistance tests using an atomic force microscope have been conducted on ultra-thin hard amorphous carbon coatings, often called diamond-like carbon (DLC) coatings, deposited using filtered cathodic arc (FCA), direct ion beam (IB), electron cyclotron resonance plasma chemical vapour deposition (ECR-CVD) and sputter (SP) deposition processes. Coating thicknesses of 20, 10, 5 nm and, for the first time, 3.5 nm coatings, have been investigated. The objectives of the study were to identify the thinnest coating that exhibits good wear-resistance, to identify deposition processes that produced superior coatings for wear-resistance and to understand failure mechanisms of such ultra-thin coatings during wear. It was found that, in general, the thicker coatings exhibited better scratch/wear performance than thinner coatings due to their better load-carrying capacity as compared to the thinner coatings. At 20 nm, ECR-CVD and FCA coatings showed the best wear resistance. At 10 nm, ECR-CVD was the best, while IB coating showed the best wear resistance at 5 nm. Five nanometer coatings showed reasonable wear resistance, while 3.5 nm coatings showed extremely low load-carrying capacity, poor wear resistance and evidence of early coating delamination. Although IB and ECR-CVD 3.5 nm coatings showed some amount of wear resistance at low loads, it appears that the 3.5 nm coatings studied are infeasible for wear-resistant applications as of now.

Numerical simulation of plasma flow downstream in an ECR plasma deposition apparatus

The plasma flow along the divergent magnetic field of an electron cyclotron resonance (ECR) plasma source has been simulated. We assume that ions undergo charge exchange and elastic scattering collisions with the neutral gas in the downstream region. An iterative scheme for solution of the Boltzmann equation and quasineutrality has been developed, based on a Monte Carlo description for ion dynamics and reasonable data in our experimental device. We studied the effects of the magnetic field configuration and neutral gas pressure on the plasma potential, density distribution along a divergent magnetic field, and the ion flux density and energy incident on a substrate. The numerical simulated results have been compared with the experimental data measured by using Langmuir probe in our ECR plasma chemical vapor deposition system.

Interface State Densities for SiNx: H on Cleaved GaAs and InP(110)

ABSTRACTSilicon nitride was deposited in-situ by electron-cyclotron resonance plasma chemical-vapour deposition (ECR-CVD) on (110) surfaces formed by cleaving GaAs and InP(100) substrates in an ultra-high vacuum processing system. Capacitors formed by depositing Al gates on the facet surfaces were analyzed by the high-low frequency capacitance-voltage (CV) technique. The minimum interface-state densities obtained for the cleaved GaAs (110) surfaces were 1–2 × 1012 eV−1cm−2. For cleaved InP facets the measured minimum interface state densities were a factor of two higher; however, they exhibited a smaller hysteresis in the CV characteristics and a smaller modulation in the surface potential. The interface state densities did not change significantly for the GaAs(110) facets if a Si interface control layer 0.8–2 nm thick was deposited prior to silicon nitride deposition; however, a larger effect was observed for the hysteresis and flatband voltage shift of the CV characteristics. The effect of annealing on the interfaces with Si was investigated and the performance compared with published results for GaAs(100) surfaces prepared by molecular-beam epitaxy.