DETERMINATION OF SILICON IN PHOTORESIST B Y GRAPHITE-FURNACE AAS

The determination of silicon in positive type photoresist was studied using graphite-furnace Zeeman-type AAS by preconditioning the furnace with calcium. Calcium solution in 0.02 M HCl injected into the furnace before the sample injection enhanced silicon absorbance by 50%. The w avelength, band width and current of the silicon hollow cathode lamp w ere 251.6 nm, 0.4 nm and 10 mA, respectively. The solutions were injec ted into the furnace in the following order: calcium (drying at 120 de grees C and ashing to 550 degrees C), silicon standard solution (with standard addition method, drying at 120 degrees C), and diluted photor esist. The optimum furnace program determined for silicon consisted of drying for 10 s at 150 degrees C (ramp mode), first ashing for 15 s t o 850 degrees C (ramp mode), second ashing for 25 s to 1200 degrees C (ramp mode) atomizing for 10 s at 2800 degrees C (flash mode) and clea ning for 3 s at 3000 degrees C (step mode). The detection limit of sil icon by the in-furnace standard addition was found to be 0.02 ng and t he relative standard deviation for photoresist (n=5) was 5%.