RF thermal plasma CVD

Figure 2. Schematic diagram of various CVD techniques for diamond synthesis, (a) HFCVD (b) MW PACVD (c) ECR MW PACVD (d) DC PACVD (e) RF PACVD (0 DC thermal plasma CVD (g) RF thermal plasma CVD (h) flame (combustion) CVD.l (Reproduced with permission.)...

In spite of the poor energy efficiency and difficult process control in both the DC thermal plasma CVD and the RF thermal plasma CVD, the high growth rates achieved with these methods represent a milestone in diamond CVD technology. Within less than a decade, deposition rates have been... 

The low temperature synthesis of diamond films has been investigated in the substrate temperature range of 350-800°C in RF thermal plasma CVD, and diamond films of reasonable quality have been obtained at 550-600°C which are considerably lower than those generally considered as... 

Substrates are usually immersed in the plasmas in MW, DC and RF PACVD processes or separated from the plasmas in DC and RF thermal plasma CVD processes. A. substrate is generally placed 0.5-2 cm. fi-om the hot filament in the HFCVD, or fi om the flame burner nozzle in the combustion CVD, and up to 5 cm from the thermal plasma nozzle in the DC thermal plasma CVD.f " Report on distances greater than several centimeters has not been found in published literature, which may be attributable to... 

In further sections extensions or adaptations of the PECVD method will be presented, such as VHF PECVD [16], the chemical annealing or layer-by-layer technique [17], and modulation of the RF excitation frequency [18]. The HWCVD method [19] (the plasmaless method) will be described and compared with the PECVD methods. The last deposition method that is treated is expanding thermal plasma CVD (ETP CVD) [20, 21]. Other methods of deposition, such as remote-plasma CVD, and in particular electron cyclotron resonance CVD (ECR CVD), are not treated here, as to date these methods are difficult to scale up for industrial purposes. Details of these methods can be found in, e.g., Luft and Tsuo [6]. 

Saitoh, H., et al., Synthesis of C-BN Film by Thermally Activated RF Plasma CVD Method, Japan New Diamond Forum, pp. 57-59, New Diamond (1988)... 

Besides the MPCVD reactors, other CVD reactors are also used for diamond deposition. They are hot filament, DC plasma, radio-frequency (rf) plasma, thermal rf plasma, plasma jet, and combustion CVD reactors. In the following, hot filament and DC plasma CVD reactors will be described, because they have been used for oriented growth of diamond. 

CVD can also be classified using its activation methods. Thermal activated CVD processes are initiated only with the thermal energy of resistance heating, RF heating or by infrared radiation. They are widely used to manufacture the materials for high-temperature and hard-to-wear applications. In some cases enhanced CVD methods are employed, which includes plasma-enhanced CVD (PECVD), laser-induced CVD (LCVD), photo CVD (PCVD), catalysis-assisted CVD and so on. In a plasma-enhanced CVD process the plasma is used to activate the precursor gas, which significantly decreases the deposition temperature. 

Without the bias, formation of cBN (or hard BN) was reported with ECR plasma CVD (293), microwave plasma CVD (275,294), RF plasma CVD with a thermal activation filament (295), and reactive evaporation of B or H3BO3 in an NH3 discharge (296-298). The amount of cBN in an hBN or tBN matrix of these films appears to be snoaUer than that of the films made with bias control. Ion beam deposition from a borazine (B3N3H) plasma (299) or from ionized borazine (264,270,300) was also reported to produce a hard BN material. 

Chemical vapor deposition (CVD) is an atomistic surface modification process where a thin solid coating is deposited on an underlying heated substrate via a chemical reaction from the vapor or gas phase. The occurrence of this chemical reaction is an essential characteristic of the CVD method. The chemical reaction is generally activated thermally by resistance heat, RF, plasma and laser. Furthermore, the effects of the process variables such as temperature, pressure, flow rates, and input concentrations on these reactions must be understood. With proper selection of process parameters, the coating structure/properties such as hardness, toughness, elastic modulus, adhesion, thermal shock resistance and corrosion, wear and oxidation resistance can be controlled or tailored for a variety of applications. The optimum experimental parameters and the level to which... 

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. 

---