SIMS has inherent difficulties with quantification because of the so called “matrix effect”. Many factors contribute to the matrix effect, e.g. differing concentration of oxygen, sputtering rate differences in the hetero-layers, etc. In the case of MOS(metal-oxide-semiconductor) structures, the oxide layer gives rise to a large matrix effect. It is thus very difficult to use SIMS to evaluate the relationship between the electrical properties of the LSI devices and the impurity profiles present in such systems.

So we have been studying laser post-ionization SNMS, which consists of TOF-SIMS apparatus and excimer laser, in order to quantify the impurity profiles around SiO2/Si interface. Depth profiles of implanted Cu with 1×1015 atoms/cm2 in SiO2(100 nm)/Si system taken by Monte-Carlo simulation ,SIMS and laser post-ionization SNMS are shown in Fig.l. In this implantation condition the Cu+:Cu2+:Cu3+ percentage ratios of the charge distributions were 44:42:14. Fig. 1(a) shows the theoretical depth profiles expetted from this implantation condition by Monte-Cairo simulation.