Evaluation of citric acid added cleaning solution for removal of metallic contaminants on Si wafer surface

We have investigated cleaning solutions based on citric acid (CA) to remove metallic contaminants from the silicon wafer surface. Silicon wafers were intentionally contaminated with Fe, Ca, Zn, Na, Al and Cu standard solution by spin coating method and cleaned in various CA-added cleaning solutions. The concentration of metallic contaminants on the silicon wafer surface be fore and after cleaning was analyzed by vapor phase decomposition/inductive ly coupled plasma-mass spectrometry (VPD/ICP-MS). And the surface micro-rou ghness was also measured by atomic force microscopy (AFM) to evaluate the e ffect of cleaning solutions. It was found that acidic CA/H2O solution has t he ability to remove metallic contaminants from silicon surfaces. Fe, Ca, Z n and Na on silicon surface were decreased from the order of 10(12) atoms/c m(2) to the order of 10(9) atoms/cm(2) even at low CA concentration, low te mperature of CA solution and with short immersion time. CA was also effecti ve in alkali cleaning solution. Fe, Ca, Zn, Na and Cu were reduced down to the order of 10(9) atoms/cm(2) in CA added with Nh(4)OH/H2O2/H2O solution w ithout degradation of surface micro-roughness.