Ion implantation for silicon device manufacturing: A vacuum perspective

Ion implantation systems rely on a diverse vacuum environment to accomplish the goals of doping of Si materials for formation of electronic devices. Failure to manage the gas flows and contaminants in this complex vacuum system can lead to severe penalties for integrated circuit processing. Examples of vacuum control issues in ion sources, beam transport, dosimetry, wafer charging, and contamination are discussed. Contamination issues involve a mix of ion and vapor transport of dopants and metals, charge exchange and molecular breakup collisions, and particle generation associated with electrode arcing. Additional factors in good vacuum design include operation of contamination-free, rapid-cycle loadlocks and safety issues, such as management of potentially explosive gas mixtures during regeneration of cryopumps.