Cathodic sputtering process

The sputtering process shown in Figure 19.1, utilizes the phenomena associated with a low-pressure gas discharge. The system comprises an anode and cathode generally the low-pressure chamber is earthed and forms an infinite area anode the small cathode surface is the target material from which gas ion-etching occurs, resulting in condensation of the material onto workpieces within the vacuum chamber. 

Fig. 5.8. Schematic diagram of the reactive dual magnetron sputter process using MF plasma excitation. ptot = 1CF3 — 10-2 mbar. Cathode length up to 3.75 m, power density up to 20Wcm-2, plasma excitation frequency 10-100 kHz...

Ohno, S., Sato, D., Kon, M., Song, P. K., Yoshikawa, M., Suzuki, K., Frach, P. and Shigesato, Y. (2003). Plasma emission control of reactive sputtering process in mid-frequency mode with dual cathodes to deposit photocatalytic Ti02 films. Thin Solid Films 445(2), 207-212. 

Kapton polyimide has been widely used in the electronic industry because of its low dielectric constant, good mechanical properties and high thermal stability. Many applications require good adhesion between Kapton polyimide film and metal. Various processes to improve adhesion of metal to Kapton polyimide have been reported in the literature. DeAngelo et al., (D describe a process to form metal oxides on the surface of polyimide to improve adhesion. Other efforts to improve adhesion of a metal layer involve roughening of the surface of polyimide substrate by methods such as cathodic sputtering (2), chemical attack (2., 1), and reactive ion etching (1,4). 

OLEDs are normally fabricated on a transparent substrate and therefore on top of a transparent anode. However, several potential applications, such as micro-displays integrated on a crystalline silicon chip or a totally transparent OLED array for a heads-up display, require a transparent top electrode. There has been some work published describing the development of transparent cathodes. The most obvious approach is to use a very thin metal layer, such as Mg Ag, overcoated with a transparent conductor, such a.s ITO [94]. This is not so trivial as it appears, since the cathode metal must survive the reactive sputtering process employed to deposit the ITO. Another approach uses no metal but rather a CuPc layer between the electron-transporting Alqs and the ITO [95]. It is suggested dial the oxidative environment during ITO deposition results in heavy n-type doping near the CuPc interface. 

From the area of polymer dielectrics, a sample is presented here using a commercially available and (from many microelectronic applications) well-known high-temperature polyimide. The deposition and the subsequent curing process have been described in Section 18.2.3, resulting in a 190 nm thick insulating film that showed a good chemical resistance towards diluted developer solution and acetone, so that the cathode-sputtered Au drain and source contacts can be structured as described in Section 18.2.1. The 30 nm thick pentacene layer is thermally evaporated at a deposition rate of about 0.1 nm/s and a process pressure of 1 x 10 mbar. 

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