TRACE ELEMENTAL ANALYSIS OF TUNGSTEN

Glow discharge mass spectrometry (GDMS) has been used to provide trace elemental analysis of tungsten filaments used in ion implantation tec hnology. Results indicated very large potassium signals on all of the tungsten samples with levels from 310 to 710 ppm (parts per million). Aluminum levels reached as high as 38 ppm. Cr, Fe, and Ni were detecte d with levels ranging from 1.1 ppb (parts per billion) to 14 ppm. Most filaments had radioactive levels of Th not exceeding 1.1 ppm except f or one supplier which had a measured level of 26 ppm. Sodium levels va ried from 0.24 ppm to 17 ppm. GDMS results from used source filaments indicated that filament lifetimes can be drastically extended by provi ding tungsten liners in the plasma are chamber.