Enhanced Detection of Copper Impurity in Silicon Wafer by Dynamic Secondary Ion Mass Spectrometry

A method by continuous electron bombardment of high purity SiO2 on a silicon wafer enables Cu-I(+) migration from the silicon bulk to the near surface where measurements were simultaneously carried out by dynamic secondary ion mass spectrometry (D-SIMS) depth profile. Negative charges from the electron bombardment were retained in the SiO2 layer and generated electron wind force and electrostatic force that significantly influenced the migration of Cu-I(+) to the surface region, where its density increased with the electron bombardment current density. The Cu-I(+) drift velocity was estimated empirically in this experiment to reach 18.3 cm/s. This method has enabled the detection of Cu by D-SIMS beyond its sensitivity limit. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3526095] All rights reserved.