The influence of hydrogen and nitrogen on the formation of Si nanoclusters embedded in sub-stoichiometric silicon oxide layers

摘要

This work reports the study concerning the influence of the preparation conditions on the structure of silicon rich oxide (SRO) deposited by PECVD method by which the structural properties of the film are strictly related. In particular we investigated the role of reactant gases N_2O and SiH_4 on the total Si concentration, Si excess concentration, Si clustered concentration and size of nanoclusters formed by high annealing temperature. We payed particular attention on the role of the hydrogen and nitrogen during the Si agglomeration. The presence of hydrogen atoms on the as-deposited specimen, confirmed by the Si-H bonds peak on the FTIR analysis, has been directly correlated to the silicon excess concentration in the layer. The silicon, oxygen and nitrogen atomic density has been calculated from RBS analysis. These information were coupled to the ones obtained using methodology based on electron energy loss spectroscopy combined with energy filtered images, which allowed us to quantify the clustered silicon concentration in annealed sub-stoichiometric silicon oxide layers (SiO_x). We have verified that the nitrogen dissolved in the layer inhibits the Si excess clustering so that the efficiency of silicon agglomeration process decreases as the nitrogen content increases.