Low temperature growth of diamond films by microwave plasma chemical vapor deposition using CH4 +CO2 gas mixtures

Chen, Chia–Fu; Chen, Sheng–Hsiung; Ko, Hsien-Wen; Hsu, Sung Po

doi:10.1016/0925-9635(94)90200-3

Cited by 29 publications

(6 citation statements)

References 18 publications

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“…The Bachmann diagram provides a very convenient overview of the C/H/O gas mixing ratios required for successful diamond chemical vapor deposition (CVD). Most CVD diamonds are currently grown from C/H (typically CH 4 /H 2 ) gas mixtures, , but early studies explored a range of C/H/O source gas mixtures, from the perspectives of the gas phase chemistry and composition (as deduced by optical emission spectroscopy (OES) and/or mass spectrometry) and of the growth rate and quality of the resulting diamond. − These early studies demonstrated that successful diamond growth was restricted to compositions very close to the H–CO tie line in Figure and suggested that C/H/O plasmas offered a route to growing diamond at lower substrate temperatures ( T sub ) than with the traditional C/H gas mixtures. Mollart and Lewis reported a comprehensive study of microwave (MW) activated CH 4 /CO 2 and C 2 H 4 /CO 2 mixtures (with and without additional H 2 ), which demonstrated formation of high quality polycrystalline diamond films at commercially viable growth rates.…”

Section: Introductionmentioning

confidence: 99%

Exploring the Plasma Chemistry in Microwave Chemical Vapor Deposition of Diamond from C/H/O Gas Mixtures

Kelly¹,

Richley²,

Western³

et al. 2012

J. Phys. Chem. A

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Microwave (MW)-activated CH(4)/CO(2)/H(2) gas mixtures operating under conditions relevant to diamond chemical vapor deposition (i.e., X(C/Σ) = X(elem)(C)/(X(elem)(C) + X(elem)(O)) ≈ 0.5, H(2) mole fraction = 0.3, pressure, p = 150 Torr, and input power, P = 1 kW) have been explored in detail by a combination of spatially resolved absorption measurements (of CH, C(2)(a), and OH radicals and H(n = 2) atoms) within the hot plasma region and companion 2-dimensional modeling of the plasma. CO and H(2) are identified as the dominant species in the plasma core. The lower thermal conductivity of such a mixture (cf. the H(2)-rich plasmas used in most diamond chemical vapor deposition) accounts for the finding that CH(4)/CO(2)/H(2) plasmas can yield similar maximal gas temperatures and diamond growth rates at lower input powers than traditional CH(4)/H(2) plasmas. The plasma chemistry and composition is seen to switch upon changing from oxygen-rich (X(C/Σ) < 0.5) to carbon-rich (X(C/Σ) > 0.5) source gas mixtures and, by comparing CH(4)/CO(2)/H(2) (X(C/Σ) = 0.5) and CO/H(2) plasmas, to be sensitive to the choice of source gas (by virtue of the different prevailing gas activation mechanisms), in contrast to C/H process gas mixtures. CH(3) radicals are identified as the most abundant C(1)H(x) [x = 0-3] species near the growing diamond surface within the process window for successful diamond growth (X(C/Σ) ≈ 0.5-0.54) identified by Bachmann et al. (Diamond Relat. Mater.1991, 1, 1). This, and the findings of similar maximal gas temperatures (T(gas) ~2800-3000 K) and H atom mole fractions (X(H)~5-10%) to those found in MW-activated C/H plasmas, points to the prevalence of similar CH(3) radical based diamond growth mechanisms in both C/H and C/H/O plasmas.

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Section: Introductionmentioning

confidence: 99%

Exploring the Plasma Chemistry in Microwave Chemical Vapor Deposition of Diamond from C/H/O Gas Mixtures

Kelly¹,

Richley²,

Western³

et al. 2012

J. Phys. Chem. A

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“…The present study extends this comparison to the case of C/H/O plasmas. These have been proposed − as a route to growing diamond at lower substrate temperatures ( T sub ) than with the traditional C/H gas mixtures (with or without some added Ar). The companion article presents the first quantitative diagnosis of the chemistry and composition of CH 4 /CO 2 /H 2 plasmas under conditions relevant to contemporary diamond CVD.…”

Section: Introductionmentioning

confidence: 99%

Optical Emission from Microwave Activated C/H/O Gas Mixtures for Diamond Chemical Vapor Deposition

Richley¹,

Kelly²,

Ashfold³

et al. 2012

J. Phys. Chem. A

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The spatial distributions and relative abundances of electronically excited H atoms, OH, CH, C(2) and C(3) radicals, and CO molecules in microwave (MW) activated CH(4)/CO(2)/H(2) and CO/H(2) gas mixtures operating under conditions appropriate for diamond growth by MW plasma enhanced chemical vapor deposition (CVD) have been investigated by optical emission spectroscopy (OES) as a function of process conditions (gas mixing ratio, incident MW power, and pressure) and rationalized by reference to extensive 2-dimensional plasma modeling. The OES measurements clearly reveal the switch in plasma chemistry and composition that occurs upon changing from oxygen-rich to carbon-rich source gas mixtures, complementing spatially resolved absorption measurements under identical plasma conditions (Kelly et al., companion article). Interpretation of OES data typically assumes that electron impact excitation (EIE) is the dominant route to forming the emitting species of interest. The present study identifies a number of factors that complicate the use of OES for monitoring C/H/O plasmas. The OH* emission from EIE of ground state OH(X) radicals can be enhanced by excitation energy transfer from metastable CO(a(3)Π) molecules. The CH* and C(2)* emissions can be boosted by chemiluminescent reactions between, for example, C(2)H radicals and O atoms, or C atoms and CH radicals. Additionally, the EIE efficiency of each of these radical species is sensitively dependent on any spatial mismatch between the regions of maximal radical and electron density, which itself is a sensitive function of elemental C/O ratio in the process gas mixture (particularly when close to 1:1, as required for diamond growth) and the H(2) mole fraction.

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“…The first strategy is related to variation and optimization of deposition parameters in standard CH 4 /H 2 gas mixture (pressure, power, gas ratio, etc.) and to changed plasma and surface chemistry by addition of various gases, mainly oxygen or oxygen containing gases (CO, CO 2 ), into the deposition process 6–8. The second strategy is based on the implementation of novel plasma deposition system such as surface‐wave plasmas or linear antennas microwave CVD systems, which are characterized by cold plasma due to larger distance of hot plasma region from the substrates 9.…”

Section: Introductionmentioning

confidence: 99%

Low temperature diamond growth by linear antenna plasma CVD over large area

Ižák

Babchenko

Varga

et al. 2012

Physica Status Solidi (b)

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233 343 184 Recently, there is a great effort to increase the deposition area and decrease the process temperature for diamond growth which will enlarge its applications including use of temperature sensitive substrates. In this work, we report on the large area (20 Â 30 cm 2 ) and low temperature (250 8C) polycrystalline diamond growth by pulsed linear antenna microwave plasma system. The influence of substrate temperature varied from 250 to 680 8C, as controlled by the table heater and/or by microwave power, is studied. It was found that the growth rate, film morphology and diamond to non-diamond phases (sp 3 /sp 2 carbon bonds) are influenced by the growth temperature, as confirmed by SEM and Raman measurements. The surface chemistry and growth processes were studied in terms of activation energies (E a ) calculated from Arrhenius plots. The activation energies of growth processes were very low (1.7 and 7.8 kcal mol À1 ) indicating an energetically favourable growth process from the CO 2 -CH 4 -H 2 gas mixture. In addition, from activation energies two different growth regimes were observed at low and high temperatures, indicating different growth mechanism.

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Low temperature growth of diamond films by microwave plasma chemical vapor deposition using CH4 +CO2 gas mixtures

Cited by 29 publications

References 18 publications

Exploring the Plasma Chemistry in Microwave Chemical Vapor Deposition of Diamond from C/H/O Gas Mixtures

Exploring the Plasma Chemistry in Microwave Chemical Vapor Deposition of Diamond from C/H/O Gas Mixtures

Optical Emission from Microwave Activated C/H/O Gas Mixtures for Diamond Chemical Vapor Deposition

Low temperature diamond growth by linear antenna plasma CVD over large area

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