Resonance Microwave Plasma Chemical Vapor Research Articles

AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MISHEMTs) using plasma deposited BN as gate dielectric

AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MISHEMTs) were fabricated on Si substrates with a 10 nm boron nitride (BN) layer as a gate dielectric deposited by electron cyclotron resonance microwave plasma chemical vapor deposition. The material characterization of the BN/GaN interface was investigated by X-ray photoelectric spectroscopy (XPS) and UV photoelectron spectroscopy. The BN bandgap from the B1s XPS energy loss is ∼5 eV consistent with sp2 bonding. The MISHEMTs exhibit a low off-state current of 1 × 10−8 mA/mm, a high on/off current ratio of 109, a threshold voltage of −2.76 V, a maximum transconductance of 32 mS/mm at a gate voltage of −2.1 V and a drain voltage of 1 V, a subthreshold swing of 69.1 mV/dec, and an on-resistance of 12.75 Ω·mm. The interface state density (Dit) is estimated to be less than 8.49 × 1011 cm−2 eV−1. Gate leakage current mechanisms were investigated by temperature-dependent current–voltage measurements from 300 K to 500 K. The maximum breakdown electric field is no less than 8.4 MV/cm. Poole–Frenkel emission and Fowler–Nordheim tunneling are indicated as the dominant mechanisms of the gate leakage through the BN gate dielectric at low and high electric fields, respectively.

Cutting performance of cubic boron nitride-coated tools in dry turning of hardened ductile iron

A novel cubic boron nitride (cBN)-coated silicon nitride(Si3N4) cutting tool was fabricated via the diamond interlayers by electron cyclotron resonance (ECR) microwave plasma chemical vapor deposition (MPCVD) technique. The cutting performance of cBN-coated tools was evaluated by dry turning of hardened ductile iron in comparison with the commercially available titanium aluminum nitride (TiAlN)-coated tools. The effects of cutting parameters on the cutting force and cutting temperature were studied. The results showed that the cutting forces increased with the increase of depth of cut but decreased with the increase of cutting speed, while the cutting temperature increased with the increase of cutting speed. Compared to the TiAlN-coated tools under identical turning conditions, the cBN-coated tools had lower cutting force and cutting temperature, and smaller tool wear. The cBN-coated tools delivered excellent cutting performance and prolonged tool life. Furthermore, the wear patterns and wear mechanisms of cBN-coated tools were investigated. It was found that the dominant wear patterns were crater wear on rake face and flank wear land, and the wear mechanisms were demonstrated to be abrasion wear and diffusion wear. The cutting experiments verified that the cBN-coated tools had attractive potentials in the applications for dry turning of refractory metals and hardened ferrous materials.

In situ photoelectron spectroscopic characterization of c-BN films deposited via plasma enhanced chemical vapor deposition employing fluorine chemistry

Cubic boron nitride (c-BN) was deposited on silicon substrates using electron cyclotron resonance microwave plasma chemical vapor deposition (ECR MPCVD) employing Ar–He–N2–H2–BF3 gas precursors at 780°C. In situ X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM) measurements indicated that c-BN nucleated and grew on a hexagonal boron nitride (h-BN) layer that initially formed on the substrate. The minimum and maximum bias applied to the sample that yielded c-BN growth was investigated by in situ XPS. Rutherford backscattering spectrometry (RBS), elastic recoil detection (ERD), and XPS were employed to determine the chemical composition of the produced films, while XPS and in situ ultraviolet photoelectron spectroscopy (UPS) were employed to investigate the electronic structure of film surfaces. The bandgap of the c-BN films was estimated to be 6.2±0.2eV from XPS measurements. In situ UPS measurements indicated that as-deposited c-BN films exhibited a negative electron affinity (NEA). The surface continued to exhibit an NEA after H2 plasma treatment performed at 650°C and annealing at 780°C. Analysis of surface bonding using a surface dipole model suggests that H-terminated N surface sites could be responsible for the observed NEA character.

Microstructure and tribological properties of cubic boron nitride films on Si3N4 inserts via boron-doped diamond buffer layers

Cubic boron nitride (cBN) coatings were deposited on silicon nitride (Si3N4) cutting inserts through conductive boron-doped diamond (BDD) buffer layers in an electron cyclotron resonance microwave plasma chemical vapor deposition (ECR MPCVD) system. The adhesion and crystallinity of cBN coatings were systematically characterized, and the influence of doping level of BDD on the phase composition and microstructure of the cBN coatings were studied. The nano-indentation tests showed that the hardness and elastic modulus of the obtained cBN coatings were 78GPa and 732GPa, respectively. The tribological properties of the cBN coatings were evaluated by using a ball-on-disc tribometer with Si3N4 as the counterpart. The coefficient of the friction and the wear rate of the cBN coatings were estimated to be about 0.17 and 4.1×10−7mm3/Nm, respectively, which are remarkably lower than those of titanium aluminum nitride (TiAlN) coatings widely used in machining ferrous metal. The results suggest that cBN/BDD coated Si3N4 inserts may have great potentials for advanced materials machining.

The effect of nitrogen incorporation in DLC films deposited by ECR Microwave Plasma CVD

Diamond like carbon (DLC) and nitrogenated diamond like carbon (DLC:N) films have been deposited by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-MP CVD) on Si (1 1 0), steel and glass substrates, using CH4 and N2 as plasma source. The effect of nitrogen doping on the optical, electrical, structural and mechanical properties of films was investigated. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy results showed that sp2 bonded carbon phases increased while the sp3 bonded carbon phases decreased by nitrogen doping. Microhardness measurements showed a decrease in hardness (from 75 to 69 GPa) according to nitrogen incorporation. Average transmittance of all the films was over 90% and band gap energy (Eg) of the films decreased due to increasing nitrogen flow rate. The film morphology was studied using the atomic force microscopy (AFM). Electrical properties were characterized by Hall measurement. Undoped DLC was p-type with a conductivity of 9.81 × 10−6 (Ω cm)−1. DLC films became n-type by nitrogen doping. The best conductivity value for the nitrogen doped DLC films was found 2.77 × 10−5 (Ω cm)−1. PL spectra of DLC and DLC:N films showed three peaks at 405 nm (3.06 eV), 533 nm (2.32 eV) and 671 nm (1.84 eV).

Tribological study of boron nitride films

Boron nitride (BN) films with different cubic and hexagonal phase compositions were deposited on silicon substrates via diamond interlayers by magnetron sputtering and electron cyclotron resonance microwave plasma chemical vapor deposition. The tribological behaviors of the BN films were investigated systematically using a ball-on-disc tribometer with silicon nitride as the counterpart. Comparison studies were also performed on sintered cubic and hexagonal BN compacts. The influence of phase compositions and surface roughness of BN coatings on their tribological characteristics was studied. The cubic BN (cBN) films showed excellent wear resistance against silicon nitride. The wear rate of the cBN films was estimated to be about 1.0 × 10 − 7 mm 3/N m by measuring the cross-sectional area of the wear track after the sliding test over a distance of 12 km.

Effects of process parameters on the structure of hydrogenated amorphous carbon films processed by electron cyclotron resonance plasma enhanced chemical vapor deposition

Abstract The paper presents the investigation of the effect of the process parameters on the structure of hydrogenated amorphous carbon (a-C:H) films deposited on Si(100) substrate by electron cyclotron resonance microwave plasma chemical vapor deposition method (ECR-PCVD). The investigation is based on an orthogonal experimental design and analysis method. Both the carbon sp3/sp2 bonding ratio and hydrogen content are evaluated from the visible Raman spectra deconvolution. The statistical results indicate that the sp3/sp2 bonding ratio is mainly affected by microwave power, and it decreases as the microwave power increases. The hydrogen content in a-C:H films is mainly affected by the substrate bias voltage, and it decreases with increasing the bias voltage. The effect of other parameters on the structure of a-C:H films is relatively not significant, but is also discussed in the paper.

Deposition of cubic boron nitride films on diamond-coated WC:Co inserts

Cubic boron nitride (cBN) thin films were deposited on diamond-coated tungsten carbide (WC) cutting inserts using electron cyclotron resonance (ECR) microwave plasma chemical vapor deposition (MPCVD). The effects of gas flow rate and substrate bias on the phase composition and structure of the BN films deposited on diamond surfaces were studied. It was revealed that both the cubic phase formation and the selective etching of hexagonal phase were controlled by modulating the hydrogen and boron trifluoride flow rate ratio. By the trial and error method the gas flow rate ratio and substrate bias voltage were optimized. Moreover the phase composition of the BN film was found to be affected by the thickness of diamond buffer layer and interrelated to the effective substrate bias. The hardness of the resulting cBN films reached the value of 70 GPa. In the synthesized coatings, the diamond beneath renders the best mechanical supporting capacity while the top cBN provides the superior chemical resistance and extreme hardness. The cBN/diamond bilayers deposited on WC inserts may serve as universal tool coatings for machining steels and other ferrous metals.

Deposition of a-C:H films on UHMWPE substrate and its wear-resistance

In prosthetic hip replacements, ultrahigh molecular weight polyethylene (UHMWPE) wear debris is identified as the main factor limiting the lifetime of the artificial joints. Especially UHMWPE debris from the joint can induce tissue reactions and bone resorption that may lead to the joint loosening. The diamond like carbon (DLC) film has attracted a great deal of interest in recent years mainly because of its excellent tribological property, biocompatibility and chemically inert property. In order to improve the wear-resistance of UHMWPE, a-C:H films were deposited on UHMWPE substrate by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-PECVD) technology. During deposition, the working gases were argon and acetylene, the microwave power was set to 800 W, the biased pulsed voltage was set to −200 V (frequency 15 kHz, duty ratio 20%), the pressure in vacuum chamber was set to 0.5 Pa, and the process time was 60 min. The films were analysed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, nano-indentation, anti-scratch and wear test. The results showed that a typical amorphous hydrogenated carbon (a-C:H) film was successfully deposited on UHMWPE with thickness up to 2 μm. The nano-hardness of the UHMWPE coated with a-C:H films, measured at an applied load of 200 μN, was increased from 10 MPa (untreated UHMWPE) to 139 MPa. The wear test was carried out using a ball (Ø 6 mm, SiC) on disk tribometer with an applied load of 1 N for 10000 cycles, and the results showed a reduction of worn cross-sectional area from 193 μm 2 of untreated UHMWPE to 26 μm 2 of DLC coated sample. In addition the influence of argon/acetylene gas flow ratio on the growth of a-C:H films was studied.

Characteristics of Co-filled carbon nanotubes

The Co-filled carbon nanotubes (CNTs) film was produced on silicon substrate by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-CVD). The effects of different plasma powers of 200, 300, 400 and 500 W, on the morphology, structure and electrical properties of the CNTs film, were studied. The results showed that the surface density of the vertical nanotubes decreased when the plasma power was higher than 200 W. When plasma power of 300 W was used, the ends of the metal-filled carbon nanotubes (MF-CNTs) became straighter and more uniform. The Co-filled CNTs grown at 300 and 400 W had a current discharge at the applied voltages of 30 and 40 V, respectively. In addition, the surface morphology and the structure of the CNTs film were examined using scanning electron microscopy (SEM) and high-resolution field emission gun transmission electron microscopy (TEM). Energy dispersive X-ray spectroscopy (EDXS) analyses were performed to identify the composition of the material inside the CNTs.

Nanomechanical characterization of amorphous hydrogenated carbon thin films

Amorphous hydrogenated carbon (a-C:H) thin films deposited on a silicon substrate under various mixtures of methane–hydrogen gas by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-MPCVD) was investigated. Microstructure, surface morphology and mechanical characterizations of the a-C:H films were analyzed using Raman spectroscopy, atomic force microscopy (AFM) and nanoindentation technique, respectively. The results indicated there was an increase of the hydrogen content, the ratio of the D-peak to the G-peak ( I D/ I G) increased but the surface roughness of the films was reduced. Both hardness and Young's modulus increased as the hydrogen content was increased. In addition, the contact stress–strain analysis is reported. The results confirmed that the mechanical properties of the amorphous hydrogenated carbon thin films improved using a higher H 2 content in the source gas.

Nanoindentation investigation of amorphous hydrogenated carbon thin films deposited by ECR-MPCVD

Nanomechanical properties of amorphous hydrogenated carbon thin films are performed by nanoindentation technique. The amorphous hydrogenated carbon films are produced on silicon substrate by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-MPCVD). The effect of negative bias voltage on amorphous hydrogenated carbon films is examined by Raman spectroscopy and the results showed that the intensity ratio of D-peak to G-peak ( I D/ I G) of amorphous hydrogenated carbon films at various bias voltages, increased as the bias voltage increased. The results also showed that Young’s modulus and hardness also increased as the bias voltage increased. In addition, Young’s modulus and hardness both decreased as the indentation depth increased.

Mechanical and Tribological Properties of Diamond-Like Carbon Films Deposited by Electron Cyclotron Resonance Microwave Plasma Chemical Vapor Deposition

Mechanical and tribological properties of diamond-like carbon (DLC) films deposited by electron cyclotron resonance microwave plasma chemical vapor deposition were analyzed by nanoindentation, nanoscratch and ball-on-disk sliding tests. As the results, hardness and residual stress which depended on the substrate bias voltage had combined effects on the scratch resistance of the films. In sliding friction tests, the transferred layer on the surface of the counterpart accounts for the decrease of friction coefficient with increasing sliding distance. Atomic force microscopic images of the DLC films and the counterpart Si3N4 ball surfaces indicate that the sliding friction process could be treated as a periodical scratching process with many indenters.

Effects of substrate bias on nanotribologyof a-C:H films deposited by ECR-MPCVD

Nanotribological characterization of amorphous hydrogenated carbon (a-C:H) films is performed by scanning probe microscopy. The a-C:H films are produced on silicon substrate by electron cyclotron resonance microwave plasma chemical vapor deposition. The influence of substrate bias voltage on nanotribological characteristics is investigated. Scanning probe nanotribological tests, including the nano-friction, nano-wear and nano-scratch, are carried out. Large quantitative variations in friction coefficient and wear depth are found for different substrate biases. Results indicate that higher bias is beneficial to wear and deposition rate, and produces a larger friction coefficient. It also shows that substrate bias plays an important role in the tribological characteristics of a-C:H films.

Effect of gradient a-SiCx interlayer on adhesion of DLC films

Diamond-like carbon films were prepared on radio-frequency (RF) biased substrates of silicon wafer and Corning 7059 glass at low temperature substrate by electron cyclotron resonance microwave plasma chemical vapor deposition using CH4–H2 and CH4–Ar as reactant gases. The effects of a-SiCx interlayer prepared by RF-PECVD on the adhesion and failure mode of DLC films were investigated. In CH4–H2 system with the a-SiCx interlayer and RF bias applied to −90 V, the adherence of DLC films was improved significantly and the critical load was increased from 2 N without RF bias to 80 N. The failure mode transferred from spalling failure at lower substrate bias to conformal cracking at higher substrate bias. In CH4–Ar system with a-SiCx interlayer, the critical load was increased to 20 N at RF bias −90 V and the spalling failure mode was revealed. Comparing the DLC films obtained in the two system coated with a-SiCx interlayer and RF bias applied to −90 V, the one deposited in CH4–H2 system exhibited less damage which demonstrates that the films obtained has a better adherence behavior.

Nanotribology of amorphous hydrogenated carbon films using scanning probe microscopy

Nanotribological characterization of amorphous hydrogenated carbon (a-C:H) films is performed by scanning probe microscopy. The a-C:H films are produced on silicon substrate by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-MPCVD). The influences of different percentages of hydrogen (H 2) and methane (CH 4) in the gas-discharge plasmas on the nanotribological characteristics are investigated. Scanning probe nanotribological tests, including the nano-friction, nano-wear and nano-scratch, are carried out. Large quantitative variations of the friction coefficient as well as the wear depth are found for different H 2 content percentages in source gas. The results indicate that a higher H 2 content in the source gas is beneficial to wear and scratch resistance, and produces a lower friction coefficient and that source gas H 2 content plays an important role in the tribological characteristics of diamond-like films.

Mechanical properties of DLC films prepared in acetylene and methane plasmas using electron cyclotron resonance microwave plasma chemical vapor deposition

Diamond-like carbon (DLC) films were deposited on silicon using methane and acetylene plasma induced by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-MPCVD). The mechanical properties of DLC films were characterized by micro-Raman system, atomic force microscope, tribometer, nano-indenter used for both hardness and nano-scratch test measurements. The mechanical properties of both DLC films, prepared in methane and acetylene plasmas, respectively, strongly depended on the kinetic energy of impinging particles. The deposition at −120 V substrate bias gave rise to DLC films with the best mechanical properties for both methane and acetylene plasmas. The hardness measurements with variable indentation depth showed the characteristic changes in hardness values implying elastic deformations of supporting substrates. The maximum hardness value of DLC M films was 20 GPa while that of DLC A films was 28 GPa. However, the hardness dropped when DLC films were prepared at substrate biases more negative than −120 V due to the thermal graphitization. The improvement in DLC properties usually provided the films with smaller hydrogen content and higher density of sp 3 bondings. These parameters were engineered through controlling the deposition parameters. Particularly, the bombardment of growing DLC films by energetic ions showed to be extremely important to yield films with lower internal stress.

Film thickness effects on mechanical and tribological properties of nitrogenated diamond-like carbon films

Nanoindentation, nanoscratch and ball-on-disk tests were used to determine the film thickness effect on the mechanical and tribological properties of nitrogenated diamond-like carbon (CN x ) films, which were deposited on Si (100) substrates by an electron cyclotron resonance microwave plasma chemical vapor deposition (ECR MP-CVD) system. Except for the film with a thickness of 20 nm, there existed peak values of hardness for all films thicker than 44 nm. When the thickness ranged from 44 to 235 nm, the peak values of hardness and the corresponding indentation depth increased along with increasing film thickness. The results of scratch resistance tests showed that the critical loads of the fracture were independent of thickness for thinner films, however, they increased rapidly with increasing thickness for thicker films. Ball-on-disk sliding tests indicated that the friction coefficient decreased with increasing thickness for thinner films, while there was no obvious thickness dependence of the friction coefficient for relatively thicker films. The formation of transferred layer and graphitization of the films during sliding resulted in the decrease of friction coefficients at early stages of sliding.

Growth characterization and properties of diamond-like carbon films by electron cyclotron resonance chemical vapor deposition

Diamond-like carbon (DLC) films were deposited on radio-frequency (RF) biased substrates at low temperature by electron cyclotron resonance microwave plasma chemical vapor deposition using CH 4-Ar as reactant gas. The effects of gas composition ratio, microwave power and RF bias on growth rate, structure and hardness of the films were investigated. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Vickers microhardness tests were used to determine the structural change and properties of the DLC films. By changing the microwave power, the growth rate shows a maximum value of 1.6 μm/h at 150 W. From Raman spectra of the films deposited at different microwave power and RF bias, the peaks centered at 1540±20 cm −1 for the deposited films, which was the characteristic peak of DLC coatings. By increasing the RF bias the CH n peaks in the FTIR spectra decreased because of hydrogen evolution. The film hardness increased with the increase in microwave power and RF bias. DLC films synthesized at a bias voltage of −(100–250) V and CH 4/Ar gas ratio of 2/7 exhibited extreme hardness of more than 3000 kg mm −2. The role of adding Ar in reactant gases on DLC deposition was also discussed.

Fracture resistance enhancement of diamond-like carbon/nitrogenated diamond-like carbon multilayer deposited by electron cyclotron resonance microwave plasma chemical vapor deposition

Diamond-like carbon (DLC), nitrogenated diamond-like carbon (CNx) and multilayered DLC/CNx films of 350 nm overall thickness were deposited on Si (100) substrates by using an electron cyclotron resonance microwave plasma chemical vapor deposition system. The deposited films were investigated for the fracture resistance using nanoindentation and nanoscratch methods in combination with scanning electron microscopy. In nanoindentation fracture tests, the film fracture was detected by the discontinuities in the load-displacement curves. The abrupt increase in the friction force between the tip and films during nanoscratch fracture tests was taken as a criterion for film fracture. Both the nanoindentation and nanoscratch fracture tests revealed that the DLC/CNx multilayer exhibited substantially higher critical load than that measured for either DLC or CNx films, though there was no obvious enhancement in the multilayer hardness and elastic modulus while the multilayer internal stress was between that of DLC and CNx. This study suggests that the fracture resistance of hard coatings can be improved by the design of a suitable multilayer structure.