DETERMINATION OF CA, CU, FE, K, NA, AND SI IN POLYIMIDES FOR MICROELECTRONICS BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY INVOLVING SAMPLE DISSOLUTION IN ORGANIC-SOLVENTS

A method for the direct determination of the problem trace impurities of Ca, Cu, Fe, K, and Na as well as of Si in solutions of polyimides in organic solvents by electrothermal atomic absorption spectrometry is described. The suitability of different solvents and the influence of matrix residues accumulating in the atomizer on the characteristic mass and the tube lifetime were examined. For all elements excluding Si, no chemical modification was necessary, and depending on the applied sample size, the tube lifetime varied between 400 and 800 atomization cycles. For the elements Ca, Cu, Fe, K, Na, and Si, detection limits of 0.5, 2, 5, 2, and 25 ng . g(-1), respectively, were obtained, these being by a factor of 5 (for Fe)-1200 (for Ca) lower than those obtained by the digestion method, Comparison of the results by the proposed method with neutron activation analysis and four other methods proved that satisfactory accuracy was achieved.