THE DEPOSITION EQUIPMENT

The deposition equipment is composed of two chambers (Figure 8.49). One is a main chamber (for deposition) and the other a sample chamber. The base pressure of the main chamber is kept in UHV (at about... 

This can only be determined after the fixturing design has been selected and the number of parts to be processed at one time has been determined. For example, the metallization of CDs with aluminum was originally done in a batch process where hundreds of molded discs were coated in one run in a large vacuum vessel with several hours cycle time. Now the CDs are coated one-at-a-time with a cycle time of less than three seconds. This was accomplished by integrating the molding equipment and the deposition equipment so that the discs are not exposed to the air between processes and outgassing problems are avoided. 

In view of the very large number of parameters that influence the kinetics of the reactions and the characteristics of the depositions, equipments are generally complex in order to control the uniformity of temperature in the reactor, the partial pressures of the precursors and the gas flows. There are two types of reactors. The first are cold wall reactors for which only the substrates are heated directly they limit the volume where the reactions take place and avoid the formation of depositions on the walls. On the other hand, in the hot-wall reactors, the reactions between the gas species take place in the entire environment of the parts to be treated. 

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