THE SIMULTANEOUS GFAAS DETERMINATION OF VARIOUS ELEMENTS AT ULTRATRACE LEVELS IN ULTRAPURE ACIDS AND PHOTORESIST STRIPPER SOLUTIONS

Simultaneous graphite furnace AAS has proven to be a very effective an d reliable technique for the ultratrace determination of Al, Ca, Cu, F e, K, Na, Ni, Mn, Pb, and Zn in liquid reagents used in the semiconduc tor industry. The detection limits obtained for concentrated acids suc h as HCl 30% (m/v), HNO3 65% (m/v), and HF 40% (m/v), for H2O2 30% (m/ v) and several bath solutions such as diluted choline, tensides and fo r organic and inorganic photoresists, are below 1 mu g/kg. The detecti on limits for real samples do not exclusively depend upon the standard deviation of the photometer, i.e., the shot noise of the instrument, but for some elements they are directly determined by the reproducibil ity of the blank value. Up to six elements can be measured simultaneou sly, except for the alkaline elements Na and K, which for instrumental reasons have to be measured sequentially. Spike recoveries for all sa mples are within the 90-113% range. Chemical interferences were only e xperienced with hydrofluoric and hydrochloric acid. However, these can significantly be decreased by using a mixture of 10% hydrogen in argo n as the internal gas during the pyrolysis step of the furnace program . Despite the corrosive sample matrix, the analytical stability and tu be life generally exceed 300 tube firings.