PVD Process Flow

A schematic view of a web coater is shown in Fig. 8.5. The reel of film to be coated is placed in the upper part of the vacuum chamber, known as the winding chamber and, by means of suitable pumps, this chamber is evacuated to approximately 1 x 10-3 mbar. The winding chamber is separated from the lower part of the vacuum chamber, known as the evaporation chamber, by a differential pumping stage. 

In some machines the film is not passed over a cooling drum, but is directly transported over the slot and metallized ( free-span metallization). This increases the efficiency of the evaporation sources and prevents the formation of creases initiated by the cooling drum [6]. The thermal load of the film also changes. On the one hand it increases, because there is no cooling by the drum on the other hand it decreases, because there is also no heat reflection from the drum and the distance between evaporator and substrate can be increased. Whether the heat load increases or decreases depends very much on the configuration of the machine. For equal evaporator-substrate distances the thermal load, and thus the density of the metal structure, increases with free-span metallization (Fig. 8.6). 

Each of the evaporators is electrically heated by use of a high current, some 100 A, which is fed at a low alternating potential of approximately 10 V. This is achieved by using high-current transformers with a thyristor-controlled primary current. Layer thickness monitors, positioned over the width of the web at the same dis- 

The Metallization Cycle A typical metallization cycle comprises the following 

Loading of the nonmetallized reel into the winding chamber 

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Figure 1.3 Physical Vapor Deposition (PVD) Processing Flow Chart...

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