LCVD system, flow rate

Accordingly, the deposition rate, or the deposition characteristic in general, cannot be dealt with as a sole function of the monomer or operational parameters such as flow rate and discharge power. This aspect is recognized as the system-dependent nature of LCVD. 

Because powder formation depends on the polymer deposition portion of the polymerization-deposition mechanisms of LCVD, its dependence on operational parameters such as the flow rate and system pressure is not necessarily the same in... 

Although the change in system pressure from that of monomer flow to that of flow under plasma conditions depends on many factors, the relationship expressed by Eq. (12.1) still holds for the LCVD system, but the flow rate to be used in the... 

Thus, in a flow system, LCVD is visualized as a process that changes the flow rate of gas. 

The continuous operation of LCVD could be controlled, in principle, by the strict controls of the flow rate, the system pressure, and the discharge power. The addition of a residual gas analyzer in each pumping system is advantageous in detecting abnormality in gas flow, occurrence of leakage, etc. The addition of more sophisticated diagnostic devices, such as an optical emission spectrometer, in-line XPS, etc., is often counterproductive because the stability of performance and the maintenance requirement cycle of these devices do not match those for the continuous mode operation of LCVD. The information obtainable by these devices... 

These data clearly show that the size of reactor is an important factor to be considered in dealing with data obtained by a reactor. The change of reactor size influences the overall performance of LCVD of a monomer, and consequently the description of operating conditions such as flow rate, system pressure, and discharge wattage cannot be used in a generic sense, unless the size factor of reactor, domain of plasma polymerization, and the relative position of the substrate with respect to the core of luminous gas phase and/or to the tip of glow could be identified. These data show the complicated system-dependent nature of LCVD, particularly that a monomer does not produce a polymer and that the externally operative parameters, such as W, p, and F, are not the actual parameters that control LCVD. 

An LCVD system is somewhat similar to a gas flame in which the combustion rate and the gas flow rate establish a steady-state flame. In an LCVD system, the monomer flow rate and the polymer formation rate establish a steady-state polymer-forming luminous gas phase. This situation is expressed schematically in Figure 20.17, where (a) indicates the diffusional transport of the energy-carrying... 

The unit of normalized deposition rate is m, and normalized deposition rate decreases with the total surface on which deposition occurs. This aspect can be conceived as loading factor of luminous chemical vapor deposition (LCVD). Mass balance in a reactor (flow system) can be established as... 

In flow system LCVD, the system pressure is continuously adjusted by controlling the opening of a throttle valve connected to the pumping system. Because of fragmentation of the original monomer in the plasma state, the composition of the gas phase changes on the inception of the plasma. The increase in the total number of gas molecules is compensated by the increased pumping rate in a flow system, and... 

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