Close-coupled showerhead

The inherent advantages of OVPD can be exploited on an industrial scale when combined with close coupled showerhead (CCS) technology. With CCS the carrier... 

Fig. 9.2. Close-coupled showerhead technology for industrial-scale production of multiple layers and OVPD. OLED example deposited in a single OVPD module.

An important thermodynamic requirement for the homogeneous distribution of the organic gas phase in the close coupled showerhead is temperature uniformity, which also guarantees no unintended condensation of the organic material. Figure 9.3 depicts the temperature simulation of an Gen 2 OVPD showerhead suitable for substrate sizes of 400 mm x 400 mm. The showerhead is uniformly heated to 300 °C, whereas the chiller actively cools the substrate and the mask to 2 °C and to 3 °C, respectively, across the whole area. Both the mask and the substrate are in close contact and thereby actively cooled down across the whole area. 

Tab. 9.1. Intrinsic process characteristics of close coupled showerhead OVPD technology compared with conventional VTE.

As already described, the close coupled showerhead in OVPD enables homogeneous distribution of the organic gas phase and two-dimensional scalability (Table 9.1, no. 2) suitable for deposition on larger substrates. Conventional VTE operates with a point source, which is placed about the same distance from the substrate as the substrate diagonal to achieve the desired layer uniformity. This three-dimensional approach in VTE dramatically increases the equipment size and pump-down time to high vacuum, obviously limiting the scalability of VTE equipment. 

One strategy for the increase of the wafer area has been to increase the number of wafers in the reactor. Modem reactors today can carry 30x2 inch and 42x2 inch wafers for the CRIUS Close-Coupled-Showerhead (CCS) and Planetary Reactor types, respectively (see Fig. 1). 

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