Applications of surface analytical techniques for metals reduction in ion implantation

Quadrupole and magnetic sector SIMS, total reflection X-ray fluorescence spectrometry (TXRF), vapor phase decomposition with both inductively coupled plasma mass spectrometry (VPD-ICPMS) and graphite furnace atomic absorption spectrometry (VPD-GPAAS) are used and compared in the evaluation of common metallic contaminants such as Al, Fe, Cr, Mo, W, Cu and Na in ion implanters. These analytical techniques are applied to test the effectiveness of Si coated acceleration tubes and discs, as well as other protective measures such as graphite shielding and component redesign that are required to meet future metals contamination requirements, such as total added Al of less than 100 ppm of implant and total added heavy metals less than 10 ppm. This paper also discusses the effect of particulate contamination, both from the implanter and the post implant handling and measurement, on the various analytical techniques, manufacturing SPC procedures employed in the plasma spray Si coating process, and the SPC control procedure required of our SIMS vendors and on the implanters themselves. Employing these controls and analytical techniques, examples are provided as to how an effective program was executed on the Varian VIISion series of implanters to reduce the total added Al to as low as 23 ppm of implant and heavy metals to about 10 ppm. In these studies, time and species dependent effects are observed and are explained in terms of short-term chemical and multi-step sputtering mechanisms