New trends in PBII technology: industrial perspectives and limitations

The two general specifications required for plasma-based ion implantation a re low pressure large size plasmas and high voltage high current pulse gene rators. Due to the wide ion sheath expansion (up to a few tens of cm), larg e volumes of plasma are mandatory around the substrate. Multipolar discharg es, which produce a peripheral ionization facing the substrate and can be e asily scaled up, are well suited to PBII processing and begin to be widely used. However, hot filaments to sustain plasmas of reactive gases in multip olar magnetic held structures must be ruled out in favor of distributed ele ctron cyclotron resonance (DECR) plasma sources. In order to produce the hi gh voltage high current pulses necessary for PBII processing, generators us ing pulse transformers, where the voltage at the primary is provided by tra nsistor switches and where the energy is stored at a low voltage level, app ear particularly well-adapted to fulfill most of the PBII requirements in t erms of reliability, compactness, cost and safety. At the industrial level, a very great advantage of PELT over ion beam implantation lies in achievin g sequential processing in the same reactor, such as cleaning, etching and deposition prior to, during, or after the implantation process. As examples , thermochemical processing can be performed via PBII with or without exter nal independent heating. More generally, the combination of DECR plasmas an d magnetron discharges in the same reactor opens new possibilities for comp lex treatments such as PBII/CVD (chemical vapor deposition) in DECR plasmas or PBII/PVD (physical vapor deposition) in hybrid DECR-magnetron reactors. However, the transfer of processes from the laboratory to industry is main ly limited to very specific and low energy applications. In fact, mass prod uction using high voltage PBII processing requires production tools still u nder development. Due to huge secondary electron emission and sheath thickn ess above 100 kV pulse voltages, large Volume reactors (a few cubic meters) on one hand, high power pulse supplies (100 kV-1000 A/100 MW) on the other hand, are mandatory for the rise of PBII at the industrial scale. (C) 2001 Elsevier Science B.V. All rights reserved.