Application of ICP-MS for incoming chemical quality control in wafer fabrication

In this paper, application of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) in the monitoring of chemicals used in wafer fabrication as a first line of defense against wafer scrap, low yield and reliability issue was discussed. Two case studies of chemicals, 36%HCl and NH
4
OH, which were detected to be out of control limit (OOC) during regular monitoring were presented. Systematic problem-solving approach using fish bone diagram was engaged to identify the root causes of the two OOC cases. The root causes of the two OOC cases were identified to be due to the environmental condition for the HCl, and the corrosion of the valves in the central supply system for NH4OH.