Study on the determination of contamination by Cu particles on silicon wafer surfaces

Abstract

An analytical method of determining Cu contamination on Si wafer surfaces was studied. In order to make contaminated reference wafers, two forced contamination methods, i.e., particle deposition and spin coating, were used. For the former, mono-dispersed Cu particles in the submicron range were deposited on the Si wafer surface using a mono-dispersed particle generation system. The total Cu contamination level was calculated after the size of contaminated particles was measured by a surface particle inspection system and atomic force microscopy. Three mixed aqueous solutions, 1% (v/v) HF, 1% (v/v) HF + 3% (v/v) H₂O₂, 1% (v/v) HF + 3% (v/v) H₂O₂ + 5% (v/v) isopropyl alcohol (IPA), were tested for their efficiency in dissolving Cu particles by scanning the wafer surface. The recovery rate for each scanned solution was determined using a graphite furnace atomic absorption spectrometer (GFAAS) and a total X-ray fluorescence spectrometer (TR-XRF). The results of the GFAAS slightly differed from those of the TR-XRF. The scanning solution containing HF + H₂O₂ + IPA showed the highest recovery rate for both contamination methods.