Abatement of effluent species from ion implantation process

Ion implantation processes involve doping substrates with atomic or molecular species containing atoms belonging to the groups IIIA, IVA, or VA. Transferring those species to the wafer requires the use of gas or solid source materials that are fragmented and electrically charged in the ionization chamber. Most of those materials are toxic and/or corrosive giving rise to safety and environmental concerns for users. While the transition to SDSTM gas sources brings about significant safety improvements at the front end of the tool, abatement systems are necessary to control the emission of materials at the process exhaust sites. Such pollution control devices must be highly effective to remove hazardous acid and hydride gases below threshold level values (TLV) without impacting the implantation process. This paper describes the development of a customized dry scrubber to be installed directly at the exhaust of roughing and cryo-pumps of ion implanters. The design of the abatement device was based on extensive gas-phase characterization of effluent gases released from tools using SDS AsH₃, PH₃ , BF₃, and SiF₄ sources. These gas-phase analyses were performed in a quantitative, real time, continuous, on-line mode using a calibrated Fourier transform infrared (FT-IR) spectrometer. This work includes a description of important scrubber parameters, principles of operation, maintenance, and lifetime related issues