Detection and characterization of silicon nanocrystals embedded in thin oxide layers

Silicon nanocrystals embedded in a thin oxide layer can be used as charge storage elements in nonvolatile memory devices. The structural characteristics of the nanocrystals and their position in the oxide determine the electrical properties of the devices. In this work, silicon nanocrystals have been formed by ultralow-energy implantation (0.65–2.0 keV) of silicon in a 10 nm thin thermally grown SiO2 film on Si (100) followed by a thermal treatment. A time of flight secondary ion mass spectrometry (TOF-SIMS) methodology has been developed to detect the presence of silicon nanocrystals and to characterize them. The methodology allows one to obtain relevant information, such as the bandwidth and tunneling distance of Si nanocrystals. Chemical information about the presence of impurities introduced into the SiO2 layer during implantation and annealing have also been obtained. The advantages and disadvantages of this technique, based on TOF-SIMS in comparison with transmission electron microscopy, are discussed as well.