ИСТИНА

Ion-assisted plasma treatment plays an important part in the pattering of nanoporous low k SiOCH films developed for advanced interconnects of ULSI devices. Etching of low-k materials is normally carried out in fluorocarbon plasma reactors with low-energy ions of noble gases, including argon and helium. As it was shown experimentally, under the noble gas ion irradiation certain OSG films may undergo the substantial modification of their structure resulting in the densification, or the appearance of a continuous solid layer on the surface. The formation of this layer, which caused pores sealing and prevented the penetration of solvent (toluene), was confirmed by ellipsometric porosimetry measurements and by the method of X-ray reflectivity. The densification was observed for SiOCH films with small pores (less than 1.5 nm) whereas for materials with larger pores these effects were absent. Earlier we used the molecular dynamics method to study the effects of low-energy (200 eV) Ar ion irradiation on morphological analogs of low-k films based on crystal silicon. The aim of this work is to simulate sputtering of nanoporous Si- and SiO2-based structures with the same porosity and pore radius by 200 eV He and Ar ions at normal incidence and to reveal mechanisms of structural changes in nanoporous materials of different composition caused by ions of different noble gases.