Photoemission studies of very thin (

Abstract

The “ITRS Roadmap” suggests the necessity of working out the processing methods allowing formation of ultrathin dielectric layers with higher values of the dielectric permittivity than for silicon dioxide. The silicon oxynitride layers (SiOxNy) seem to be the most natural compromise. But still none of high temperature methods used for its formation can be seriously considered as final solution for future ULSI-CMOS ICs production due to the inevitable formation of nitride monolayers just at the silicon–insulator interface. The main scope of this investigation is to check if this is true.The oxynitride layers were produced by PECVD method. The process has already been optimised in order to allow repeatable and reliable formation of ultrathin layers (<10nm). These layers were investigated by photoelectron spectroscopy (PES) using variable excitation energy. This results in a variable escape depth of the photo electrons and thus the depth structure of the sample can be concluded. Due to the combination of chemical information and depth information this method is a unique tool for investigating the hidden nitride layers. In this work, we present a comparing study of oxynitride layers with different oxygen-to-nitrogen ratios and different post-deposition annealing temperatures investigated by the above described method. It will be shown that the main difference between certain preparation conditions is the SiO2− and the nitride-content and that nitride and oxynitride is distributed nearly homogeneously.