Parallel plate reactors

The radio-frequency glow-discharge method [30-34] has been the most used method in the study of a-C H films. In this chapter, it is referred to as RFPECVD (radio frequency plasma enhanced chemical vapor deposition). Film deposition by RFPECVD is usually performed in a parallel-plate reactor, as shown in Figure 1. The plasma discharge is established between an RF-powered electrode and the other one, which is maintained at ground potential. The hydrocarbon gas or vapor is fed at a controlled flow to the reactor, which is previously evacuated to background pressures below lO"" Torr. The RF power is fed to the substrate electrode... 

Ng, S.P. (2007) Visible-light-assisted photocatalytic degradation of gaseous formaldehyde by parallel-plate reactor coated with Cr ion-implanted Ti02 thin film. Solar Energy Materials and Solar Cells, 91, 54-61. 

In electrochemical reactors, the externally imposed velocity is often low. Therefore, natural convection can exert a substantial influence. As an example, let us consider a vertical parallel plate reactor in which the electrodes are separated by a distance d and let us assume that the electrodes are sufficiently distant from the reactor inlet for the forced laminar flow to be fully developed. Since the reaction occurs only at the electrodes, the concentration profile begins to develop at the leading edges of the electrodes. The thickness of the concentration boundary layer along the length of the electrode is assumed to be much smaller than the distance d between the plates, a condition that is usually satisfied in practice. 

Silicon wafers were oxygen plasma-cleaned in a parallel plate reactor at 400 W power, 300 mTorr pressure for 5 min. The gas flow was set to 100 seem total,... 

Planar or Parallel-Plate Reactor. Because very-large-scale integration (VLSI) demands nearly vertical etch profiles, planar or parallel-plate... 

Parallel-plate reactor Dissociation of CH4 for amorphous carbon Well mixed Mean electron density energy distribution measured with Langmuir probe 82... 

The initial conditions are at t = 0, T = To, andp = 0. The parameter n characterizes the dimensions of the volume for a parallel plate reactor n = 0 for a cylindrical reactor n = 1 and for a spherical reactor n = 2. In these equations, x is a space coordinate A. is the coefficient of thermal conductivity r is the characteristic size of the reactor k is the heat transfer coefficient and To is the initial temperature of the initial medium. 

The two reactors just described are parallel plate reactors. However, they are also cold wall reactors. In other words, the electrode holding the wafers is hot, but all other surfaces exposed to the plasma are cold, or at least not heated. This is done to minimize the deposition on other surfaces so that down time for cleaning can be kept as short as possible. 

Figure 15 Hot-wall, parallel-plate reactor for plasma-enhanced CVD. (Courtesy of Pacific Western Systems, Inc.)...

Silicon nitride films produced by this technique proved to be comparable to those created in parallel-plate reactors in terms of stoichiometry and hydrogen content, as evidenced by the data presented in Figures 17 and 18. 

If we restrict our attention to one set of chemical precursors (SiH4, NH3, N2), we have available more detailed data describing the quality of PECVD silicon nitride thin films as a function of the several operating parameters.3 Experiments were carried out in a parallel-plate reactor placed in a horizontal hot tube system where the wafer was placed on the grounded electrode. 

Finally, we will consider PECVD silicon oxynitrides, and their unique characteristics. When oxygen is added to a PECVD nitride film, there are indications that it may improve its crack resistance as a final passivation layer.13 Also, there may be advantages in terms of its electrical characteristics as an interlayer dielectric. Therefore, the nature of films grown when N20 is added to a SiH4, NH3 and He gas mixture in a high frequency (13.56 MHz), cold-wall, parallel-plate reactor have been studied. 

Consider the parallel-plate reactor system shown in Figure 1. It is assumed that the system is operating under... 

Catalyst Monolith. The previous discussion in this chapter focused primarily on chemical reactions taking place in packed-bed reactors. However, when a gaseous feedstream contains significant amoimts of particulate matter, dust tends to clog the catalyst bed. To process feedstreams of this type, parallel-plate reactors (monoliths) are commonly used. Figure 11-11 shows a schematic diagram of a monolith reactor. The reacting gas mixture flows between the parallel plates, and the reaction takes place on the smface of the plates. 

The importance of high rates of mass transport for a clean and efficient electrosynthesis using a filter press reactor has been stressed, and the effect of inclusion of a platic mesh turbulence promoter considered [56]. A multipurpose filterpress cell for continuous electrolysis of organic compounds has been described [57], and a mathematical model of the startup of a continuous parallel-plate reactor has been published [58]. 

The Kolbe electrolysis of acetate to ethane and carbon dioxide was modeled for a parallel-plate reactor. Three zones were considered in the model a turbulent bulk region, and a thin diffusion layer at each electrode [184b]. The same authors describe the electrolysis of gaseous acetic acid in a polymer electrolyte membrane (PEM) reactor. Platinized... 

One approach which can be taken for PECVD is the parallel plate reactor (see figure 8.4). The plasma can be created by either an RF or a DC discharge. When pure WF6 is used only etching of tungsten will occur according to the gas phase reaction ... 

Figure 8,4. Schematic representation of a parallel plate reactor.

Nevertheless, despite the fact that no quantitative predictions can yet be made with regard to reactor scale-up, it is of interest to consider some possible implications in the simplest case of a parallel plate reactor in which the field is considered to be perfectly uniform. Furthermore, if it is assumed that solid surfaces play no part in the chemical processes and that the reaction rates are only dependent upon the reduced field (E/p), then for a reactor having an electrode spacing d and operating at a voltage V and pressure p,... 

Figure 8. Design parameters for single-compartment parallel plate reactor (membrane chlor-alkali cell) with slow gas evolution in two dimensions.

FIGURE 18 11 Transient potential and current distributions within a parallel plate reactor in the presence of a double layer (a) Distribution of the potential near the surface of a spherical catalyst pellet at short times (b) Distribution of the transient current density near the surface of a spherical catalyst pellet. 

Application to capacitively-coupled reactors Figure 24a shows the electron temperature distribution in an argon discharge sustained in a one-dimensional parallel plate reactor of the kind shown in Fig. 7. The temperature peaks near the plasma-sheath interface, where the product of the current and electric field (Eq. 31) is highest, and steep gradients develop in that region. Electrons which diffuse towards the electrode during the sheath potential minimum (around r = 0.25 at left electrode, see also Fig. 

Figure 4-84. General sehematie of RF-ICP parallel plate reactor.

As was shown in Fig. 2.2, the primary current distribution is only uniform when all points on the electrode surface are strictly equivalent and the current density is low. This is possible only with two reactor designs, a parallel-plate reactor having... 

Figure 2.9 Current distributions for a parallel-plate reactor with fully developed laminar flow (a) primary current distribution, (b) secondary current distribution and (c) limiting tertiary current distribution.

RIE equipment is usually parallel plate reactors in which both plasma and DC bias voltage are... 

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