Investigations on phosphosilicate glass by using IR, AFM and cluster model calculation

Many applications of phosphosilicate glass (PSG) in microtechnology and in micro-machining, require the control of phosphorous content. This study is based mainly on optical spectroscopy and quantum calculations. It focuses on P=O bond formation and the corresponding changes of the chemical oxide structure. The characterisation of CVD thin films deposited on c-Si has been related to the dependence between the partial pressure of PH₃ and the incorporated content of phosphorous in PSG films by means of IR spectroscopy. AFM indicated spongeous structure formation for aged samples, as a result of water absorption which leads to hydrolysis of P=O and O-SiO₃ bonds. The cluster model approach based on the LCAO Hartree Fock theory was used to calculate the vibration modes for the proposed surrounding of P=O and O-P-O groups by using specific atomic cluster models. This contribution deals with some links between the chemical structures of the nearest environment of phosphorous atoms in PSG films and the features shown by IR spectra.