Microwave Plasma-Assisted CVD

Research on MW PACVD began from the pioneering work of Kamo et The MW PACVD (Tables 1 and 2) is, aside from the HFCVD, the most frequently used method for diamond growth and also the most extensively studied process. The intensive use of the MW PACVD is prompted by the following factors  

The stability and reproducibility of microwave non-iso-thermal plasmas, allowing continuous deposition for tens or hundreds of hours 

The high energy efficiency (high plasma density and low sheath potentials) 

The increased availability of 1-2 kW microwave (wave-guided) power supplies and applicators 

In spite of some ofthe advantages ofthe MW PACVD over other CVD methods, notably its stability, the deposition rates currently achievable in the 

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Stiegler, J., Lang, T., Nygard-Ferguson, M., Von Kaenel, Y. and Blank, E. (1996), Low temperature limits of diamond film growth by microwave plasma-assisted CVD. Diam. Relat. Mater., 5(3-5) 226-230. 

Microwave plasma-assisted CVD No external heating required... 

Figure 5. CVD diamond cfystals. (a) Faceted dendrites of flame CVD grown dianiond, (b) hexagonal platelet etysfai with fully developed three-dimensional facets grown from 1 vol. / Oj -1 vo .% CHa Hi at 30-40 totr and 850 C substrate temperature using microwave plasma assisted CVD, the hexagonal platelet is -2.5 pm in maximum linear dimMision.l (Reproduced wiih permission.)...

GE reported the discovery of natural semiconducting diamond in 1952 [31]. Presently, hot filament CVD and microwave plasma assisted CVD (MPACVD) produce polycrystalline or diamond carbon (DLC) films at 1-10 pm/h on a variety of substrates. However, true epitaxial growth presently is not routinely achievable at this time. Diamond substrates also are not readily available making large area lattice matched depositions a problem. Typieal substrates are Si, sapphire and even copper. Boron is an effective p-type dopant, but there is no successful n-type dopant, although As, Li, O, P and Sb have been tried. 

H. a. Samra, R. J. Hong, and X. Jiang, The preparation of diamond/tungsten-carbide composite films by microwave plasma-assisted CVD, Chem. Vap. Deposition, 13 (1), 17-20 (2007). 

In the 1950s to 1980s, two main techniques were developed for the synthesis of artificial diamond (a) high-pressure/high-temperature synthesis that yielded artificial diamond gems [18], and (b) chemical vapor deposition (CVD) [19] that made possible the synthesis of diamond in thin-film form on various substrates. Different CVD techniques have been adopted in the synthesis of diamond thin films. Three main CVD techniques include hot-filament CVD [20], plasma-assisted CVD [21], and combustion CVD [22]. There are many types of plasma-assisted CVD techniques according to the energy sources, such as the microwave plasma-assisted CVD (also... 

This Chapter will focus on the hot-filament and microwave plasma-assisted CVD techniques, which are the most commonly employed methods to grow diamond thin films and were used for most of the experiments described in this book. The major... 

Amaral M, Mohasseb F, Oliveira F J, BenedicF, SilvaR F, GicquelA, NanocrystaUine diamond coating of silicon nitride ceramics by microwave plasma-assisted CVD , Thin Solid Films, 2005, 482(1-2), 232-236... 

A large class of coordination compounds, metal chelates, is represented in relation to microwave treatment by a relatively small number of reported data, mainly p-diketonates. Thus, volatile copper) II) acetylacetonate was used for the preparation of copper thin films in Ar — H2 atmosphere at ambient temperature by microwave plasma-enhanced chemical vapor deposition (CVD) [735a]. The formed pure copper films with a resistance of 2 3 pS2 cm were deposited on Si substrates. It is noted that oxygen atoms were never detected in the deposited material since Cu — O intramolecular bonds are totally broken by microwave plasma-assisted decomposition of the copper complex. Another acetylacetonate, Zr(acac)4, was prepared from its hydrate Zr(acac)4 10H2O by microwave dehydration of the latter [726]. It is shown [704] that microwave treatment is an effective dehydration technique for various compounds and materials. Use of microwave irradiation in the synthesis of some transition metal phthalocyanines is reported in Sec. 5.1.1. Their relatives - porphyrins - were also obtained in this way [735b]. 

Figure 1.3 clearly demonstrates the luminous gas phase created under the influence of microwave energy coupled to the acetylene (gas) contained in the bottle. This luminous gas phase has been traditionally described in terms such as low-pressure plasma, low-temperature plasma, nonequilibrium plasma, glow discharge plasma, and so forth. The process that utilizes such a luminous vapor phase has been described as plasma polymerization, plasma-assisted CVD (PACVD), plasma-enhanced CVD (PECVD), plasma CVD (PCVD), and so forth. 

More recent efforts involving nitrogen ion beam assisted deposition [203, 206, 211], hot filament CVD with or without rf plasma [204, 205, 209], or microwave plasma enhanced CVD [213, 214], with bias assistance [207, 208, 212] were able to produce thin films containing C3N4, some with the PC3N4 structure and some with the cubic or a-structure. 

In the plasma-assisted technique, diamond growth involves various forms of plasma-assisted CVD processes with carbon-containing species mixed in low concentrations with hydrogen. The main types of plasmas used are (a) the DC plasma, (b) the RF plasma, (c) the microwave plasma, (d) the electron cyclotron resonance microwave plasma, and (e) the high-pressure plasma. The role of the plasma is to generate atomic hydrogen and to produce the appropriate carbon precursors for the growth of diamond. 

As noted above, amorphous carbon films can be produced from carbon-containing gas phases (physical vapour deposition, PVD). They can also be produced from hydrocarbon-containing gases (chemical vapour deposition, CVD), Both PVD and CVD processes can be thermally-activated or can be plasma- and/or electric field-assisted processes (e.g., microwave assisted CVD and ion beam deposition). As a consequence a wide range of processes have been developed to form amorphous carbon films and a correspondingly complex nomenclature has evolved [70, 71],... 

In the case of microwave-assisted CVD, the microwave energy from the generator is directed to and focused within a quartz cavity, producing a spherically shaped, glow-discharge plasma directly above the substrate. The substrate can either be positioned outside of (few mm) or immersed within the intense discharge... 

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