Microwave plasma enhanced CVD

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. 

Finally Chen et al. [213], using microwave plasma enhanced CVD, claim to have grown crystals larger than 10 pm, and propose that the incorporation of silicon from the substrate into the C-N structure promotes PC3N4 crystal growth. 

Several researchers [7] have grown vertically aligned carbon nanotubes using a microwave plasma-enhanced CVD system using a thin-film cobalt catalyst at 825 C. 

Grannen, K. J., Xiong, F., and Chang, R., The Growth of Silicon-Nitride Crystalline Films using Microwave Plasma-Enhanced CVD, J. Mater. Res., 9(9)12341-2348 (1994)... 

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. 

Radiofrequeney (RF)/mierowave radiation is a potential hazard that does not have good warning properties. Therefore, baseline data should be obtained for all routine operations with a potential for RF/mierowave radiation exposure above applieable standards, and baseline RF surveys of new equipment may be required. As a practical matter, a lower frequeney limit needs to be drawn to assess when baseline surveys are neeessary. Since the body is fairly transparent to RF frequencies in the kilohertz region, and standard RF/mierowave radiation meters have a lower limit of 300 or 500 kHz (depending on the meter), 500 kHz is sometimes used as a cutoff for the lower limit for thermal effeets. Most RF/microwave equipment used in semiconductor manufacturing operate at or above a frequency of 13.56 MHz. This equipment includes plasma etchers and ashers, sputtering units, mold pre-heaters, microwave ovens, and plasma enhanced CVD units. 

There are two main groups of CVD methods. One group has its origin in thermal CVD as mentioned earlier. Different means have been taken to enhance the CVD process hot filament (5), microwave plasma (6) (Fig. 1), electrical discharges developed as plasma jets, radio frequency plasma, and oxyacetylene flame (7). The basic gas composition is C and H, but ternary gas systems such as C——O (8), C—H—N, C—H—Ar, and C—H-metal have also been studied. Process parameters are as follows ... 

Figure 4. Uv-vis absorption spectra of the films collected (a) near the edge of the plasma, (b) inside the plasma produced by the microwave enhanced CVD method.

To lower the deposition temperature, CVD processes enhanced by plasma [48-58] and laser [55-58] have been investigated. Low-resistivity (< 40 pQ cm) TiN was deposited by Akahori et al. [59] using TiCL in an electron-cyclotron resonance (ECR) plasma process (Ts b = 540°C, microwave power = 2.8 kW). All films had stoichiometric composition with low chlorine concentrations of 0.16 at. % as determined by ICP-MS. This indicates that the nitridation reaction of TiCU is enhanced enormously by the ECR plasma. 

---