Metallic contamination in silicon processing

The yield and reliability of integrated circuits suffer significant impact due to metallic contaminations on silicon wafers. Alkali elements, particularly Na and K, introduce mobile charges in the silicon oxide layers. Alkaline earth metals such as Ca, Ba, and Sr cause the decrease of GOI, which affects CMOS performance. Other metals such as Fe, Cu, Ni, Cr, Co, Pt and Ir, dissolve in Si matrix and/or form silicides and, therefore, cause the p-n junction leakage. In this study, metallic contaminations were studied by a number of analytic techniques such as capacitance-voltage bias temperature stress (C-V/BTS), corona oxide characterization of semiconductor (COCOS) metrology, time-of-flight secondary ion mass spectrometry (TOF-SIMS), dynamic-SIMS (D-SIMS), vapour phase decomposition combined with inductively coupled plasma-mass spectrometry (VPD/ICP-MS), and VPD combined with total reflection X-ray fluorescence (VPD/TXRF) analysis, and surface photo-voltage (SPV). Na, K, Li, Ca, and Fe contaminations were found to originate from clean-room gloves.