Fourier transform infrared spectroscopy study of molecular structure formation in thin films during hexamethyldisiloxane decomposition in low pressure rf discharge

Abstract

The growth of plasma deposited organic films in general is non-homogeneous, i.e. the films can consist of several layers: substrate–film interface and cross-linked bulk plasma polymer. The fourier transform infrared spectroscopy study shows evidence for a substrate–film interface layer that appears to be formed during a gas conversion in a discharge. The reflection–absorption spectroscopy and evanescent wave spectroscopy techniques have been used to analyse the evolution of molecular structure of the films growing in hexamethyldisiloxane (HMDSO) plasmas of a low pressure capacitive rf (13.56 MHz) discharge. The pulsed operation mode of the rf discharge was used in order to provide successive steps of the HMDSO plasma–chemical conversion into stable neutral products, which were monitored by mass spectrometry. The HMDSO conversion exerts influences on the film deposition resulting in a gradient in the molecular structure of the growing films. The comparison of the film growth on substrates at floating and rf self-bias potentials shows that ions control the deposition kinetics and influence the molecular structure of films.