Tumbler reactor

Characterization of this tumbler reactor was carried out via the deposition rate measurement of a plasma polymer film on silicon wafers under different conditions. In the longitudinal direction, the deposition rate decreases significantly when the plasma moves from the central plasma zone to the remote zone. With appropriate shielding, the decay in deposition rate in the longitudinal direction can be effectively reduced. By means of the stirring, a uniform distribution of the plasma deposition is achieved within the chamber. 

Figure 22.1 Glass bottle tumbler reactor with RF external electrodes.

In principle, the rotating speed could be raised so that a considerable portion of powders is in gas phase however, it causes difficulty in feeding monomer and establishing a uniform distribution of deposition rate along the axis of tube length. In other words, maintaining powders in the gas phase is not the prime purpose of the tumbler reactor. 

Since a relatively large volume reactor is employed, e.g., 200-500 liters for basketlike tumbler reactors, it is nearly mandatory to charge sufficient number of substrate, which makes experiments with small number of substrates difficult and inefficient. On the other hand, the total number of substrates that can be charged in the basketlike tumbler is restricted by other factors of a tumbler reactor. A smaller reactor by this principle is difficult, as will be made clear by the same reason described below. 

Figure 22.2 The loading factor of LCVD in a basket like tumbler reactor surface area in...

In order to create a luminous gas phase that can be utilized in a basketlike tumbler reactor for various monomers, it is necessary to increase the diameter of the center hot electrode to reduce the unbalance in electrode surfaces. The surface area of the center hot electrode and the surface area of the basket are the main issues in this situation because the basket is the primary counterelectrode and any other grounded surface does not play a role in this specific case. The increase of diameter of the center electrode reduces the extent of the unbalance but at the same time reduces the volume in which small-size substrates could be placed. Thus, there is a trade-off point between the electrode diameter and the utilizable basket volume. Roughly 40% of the basket diameter could be a reasonable diameter for the center electrode. 

Thus, a tumbler reactor with basket sample holder could be a very efficient and inexpensive means to apply plasma polymer coating to suitable small substrate. 

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