Controlling Properties of Micro-crystalline Diamond Films using Oxygen in a Hot Filament Chemical Vapour Deposition System (original) (raw)
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Journal of Manufacturing Technology Management
Microcrystalline diamond (MCD) films were deposited using a conventional hotfilament chemical vapor deposition (HFCVD) system on 4" N-type Si (100) substrates at 30 mbar and 2800 watt for 20 hours. The methane and hydrogen gas flows were 3 sccm and 300 sccm, respectively while the oxygen flow was varied from 0.01 sccm to 0.04 sccm corresponding to 0.2% to 0.8% of methane. The films obtained were characterized using x-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) for their structure, quality and morphology, respectively. The resistivity was calculated by van der Pauw technique, current and voltage were measured using semiconductor device analyzer. It was found that growth rate and grain size increased gradually for higher concentrations of oxygen and resistivity decreased continuously whilst surface morphology varied significantly with the addition of O 2 . The enhanced growth rate was correlated with the enhanced atomic hydrogen as well as O 2 /C 2 ratio with increasing oxygen concentration and the drop in resistivity was correlated with a rise in the local defects caused by the addition of oxygen to the CVD chamber. Low resistivity polycrystalline diamond films with larger grain size can be achieved by adding very small amount of O 2 while keeping other parameters constant. These low resistivity diamond films can be used for various electronic applications and as substrates for cells cultivation. It can also be used for bio applications such as biosensors or tissue engineering.
Thin Solid Films, 1999
The effect of incorporating oxygen and nitrogen into the feed gases on the texture and surface morphology of diamond ®lm synthesized by hot ®lament chemical vapor deposition (HFCVD) is investigated. The reactant gas composition is determined by the gas¯ow rates. At a constant¯ow rate of hydrogen (33 sccm) and methane (0.68 sccm), the oxygen and nitrogen were varied in the O/(O 1 C) ratio from 0.05 to 0.43 and in the N/(N 1 C) ratio from 0.15 to 0.60. The ®lms were grown under a constant pressure (20 Torr) and a constant substrate temperature (8008C). Clearly nitrogen in the reactant gases has a distinct tendency to promote the k100l texture and the corresponding {100} morphology, whereas oxygen promotes the development of k111l texture and {111} morphology. According to the Wulff theorem (G d 100 =d 111 g 100 =g 111) and the evolutionary selection of crystallites and the surface con®gurations of diamond, the results reveal that during growth nitrogen plays a critical role in activating the C D ±H surface site and consequently increases the surface free energy g 111 , of the {111} surface. In contrast, oxygen activates the C D vH 2 surface site and increases the surface free energy g 100 , of the{100} surface. These results indicate that the texture and the surface morphology of polycrystalline diamond ®lm can be completely controlled by the reactant gas composition.
Effect of oxygen on growth and properties of diamond thin film deposited at low surface temperature
Journal of vacuum science & technology, 2008
Polycrystalline diamond thin films are grown on a p-type Si ͑100͒ single crystal substrate at a low surface deposition temperature of 455°C using a microwave plasma enhanced chemical vapor deposition process in an Ar-rich Ar/ H 2 / CH 4 plasma containing different oxygen levels from 0% to 0.75%. The surface deposition temperatures are measured and monitored by an IR thermometer capable of working in a plasma environment without any interference from the plasma emissions. The lower surface deposition temperature at high microwave power of 1300 W and higher gas pressure of 95 torr is achieved by active cooling of the substrate from the backside using a specially designed cooling stage. An enhanced growth rate from 0.19 to 0.63 m / h is observed with varying oxygen from 0% to 0.75% in the plasma. Diamond grain size also increased from 0.69 m for the sample with no oxygen to 1.74 m for the sample with 0.75% oxygen. The diamond films are characterized using x-ray diffraction, environmental scanning electron microscopy field emission gun, Raman spectroscopy, and x-ray photoelectron spectroscopy. The enhanced growth rate is correlated with the enhanced atomic hydrogen to C 2 ratio with increasing oxygen concentration in the plasma, which is measured by an in situ optical emission spectroscopy.
Bulletin of Materials Science, 2014
Polycrystalline diamond thin films with outgrowing diamond (OGD) grains were deposited onto silicon wafers using a hydrocarbon gas (CH 4) highly diluted with H 2 at low pressure in a hot filament chemical vapour deposition (HFCVD) reactor with a range of gas flow rates. X-ray diffraction (XRD) and SEM showed polycrystalline diamond structure with a random orientation. Polycrystalline diamond films with various textures were grown and (111) facets were dominant with sharp grain boundaries. Outgrowth was observed in flowerish character at high gas flow rates. Isolated single crystals with little openings appeared at various stages at low gas flow rates. Thus, changing gas flow rates had a beneficial influence on the grain size, growth rate and electrical resistivity. CVD diamond films gave an excellent performance for medium film thickness with relatively low electrical resistivity and making them potentially useful in many industrial applications.
Growth of Nitrogen-Incorporated Diamond Films Using Hot-Filament Chemical Vapor Deposition Technique
Advanced Science Letters, 2013
Micro-and nanocrystalline diamond (MNCD) films were deposited on silicon substrates by hot-filament chemical vapor deposition (HF-CVD) at chamber pressure of 22.5 torr for 20 hours. The total mass flow rate was 300 sccm (3 Vol.% CH 4 , while the nitrogen gas flow rate was varied from 0.04 to 0.64 sccm corresponding to 0.8 to 12.8% of H 2 + CH 4 mixture. The resulting films were characterized by X-Ray Diffraction (XRD), Raman Spectra, Scanning Electron Microscope (SEM) and four point probe van der Pauw method to analyze and measure the structure, quality, morphology and resistivity of the deposited films, respectively. Results show that the grain size increases at low concentration of nitrogen, while it decreases for high concentration of nitrogen and the fact is probably the formation of atomic nitrogen N o near filament surface and its inward diffusion on the surface of growing film. Resistivity decreases continuously due to formation of C H bonds in a trans-polyacetylene structure along with diamond film, which leads to change surface morphology. By increasing nitrogen content enhance distortion along [111] direction of the resulting films.
This paper focuses on reporting systematic studies on the effect of the precursor gas chemistry ratio between hydrogen/methane (H 2 /CH 4) and argon (Ar) to tailor control of the grain size, morphology and roughness of large area diamond films. Films ranging from a microcrystalline diamond structure (MCD 1–3 μm grain size) all the way to an ultrananocrystalline diamond (UNCD 3–7 nm grain size) structure were grown over 100 mm diameter areas, as a pathway for scaling diamond film growth processes by Hot Filament Chemical Vapor Deposition (HFCVD) to large areas (≥150 mm in diameter). H 2-rich/CH 4 chemistry was used to synthesize the MCD films, while Ar-rich/CH 4 /H 2 chemistry was used to grow the UNCD films. The synthesis of the diamond films using the HFCVD process indicates that the Ar content is critical to achieve the characteristic UNCD film structure with roughness , chemical bonding and thickness uniformity in the range of 5% across large areas. The ratio of Ar/H 2 in the range 70/30 sccm to 90/10 sccm, all with 2 sccm of CH 4 gas, yields films with grain size from 10–50 nm for nanocrystalline diamond (NCD) films to 3–7 nm for the UNCD films, respectively. The extremely smooth UNCD films (~3–5 nm rms) are achieved using Ar (90 sccm)/H 2 (10 sccm)/CH 4 (2 sccm) gas flows.
Effect of hydrogen on the properties of polycrystalline diamond thin films
Surface and Coatings Technology, 1994
Microwave plasma-assisted chemical vapor deposition has been used to grow undoped and doped diamond on molybdenum and silicon substrates. Current-voltage (1-V) characteristics, secondary electron emission and depth profiles for various elements by secondary ion mass spectrometry of diamond films have been measured before and after annealing in nitrogen gas at 425 •C. We have analyzed the films for morphology and chemical nature by scanning electron microscopy and Raman spectroscopy respectively. Hydrogen present in the as-deposited diamond films resulted in a decrease in the electrical resistivity and an increase in secondary electron yield. Furthermore, we have observed an increase in resistivity and decrease in yield on annealing. Comparison of these results is presented in this paper. 81
Chemical Vapor Deposition of Diamond Films in Hot Filament Reactor
Crystal Research and Technology, 2001
Diamond films of different quality have been synthesized by hot filament chemical vapor deposition (HF CVD) methods from a mixture of hydrogen and hydrocarbon gases. Thin polycrystalline films deposited on silicon substrate were studied using Raman spectroscopy, scanning electron microscopy (SEM) and electron paramagnetic resonance (EPR) technique. Nonuniform distribution of substrate temperatures yields to growth of diamond films in a variety of ways and affects on various types of carbon structures and different kind of defects. The Raman peak shifts to wave number higher than 1332 cm -1 what corresponds to a compressive stress in the range of -0.49 to -1.87 GPa. Two EPR centres with g = 2.003 and ∆H pp equal to 0.65 and 1.2 mT originate from carbon dangling bonds in diamond and in non-diamond phase, respectively.
Technology of polycrystalline diamond thin films for microsystems applications
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2005
Large area and uniform polycrystalline diamond ͑poly-C͒ thin films, with a thickness of approximately 1 m, were grown and patterned on 4 in. oxidized Si wafers using IC compatible processes for microsystems applications. Uniform and reproducible seeding with a density of 2 ϫ 10 10 /cm 2 was achieved by spinning diamond powder loaded water on 4 in. wafers. Gas mixture of 1.5% methane in hydrogen was used in MPCVD system for diamond film growth with optimized pressure and microwave power. Thickness variation of less than 20% was achieved on the 4 in. area using 43 Torr pressure and 2.8 kW microwave power. Electron cyclotron resonance ͑ECR͒-assisted microwave plasma reactive ion etch was carried out using SF 6 /O 2 / Ar gases to pattern the diamond films with an etch rate around 80 nm/ min and less than 10% variation in etch rate over a 4 in. area.
High-temperature electrical behavior of nanocrystalline and microcrystalline diamond films
Chemical vapor deposition of diamond has opened up new applications in microelectronics, microelectromechanical systems (MEMS), and coating technologies. This paper compares and contrasts the high-temperature electrical behavior of microcrystalline versus nanocrystalline diamond films. Through-thickness current–voltage characteristics between room temperature and 823 K are presented for a series of films synthesized with different gas phase concentrations of nitrogen and argon. One set of samples was characterized by measurements between room temperature and 823 K and a second set by two-step thermal cycling from room temperature to 573 and 823 K. It was found that with increasing nitrogen concentration (up to 0.1% N 2), the resistivity slightly increased followed by a decrease at higher concentrations. Activation energies and barrier heights were in general lower for the more defective films. These results in conjunction with material characterization indicated that more defective diamond films were synthesized at higher nitrogen concentrations in the gas phase.