Adsorption mechanisms of fluorocarbon polymers at ultra low-k surfaces

We report ab initio investigations for the adsorption mechanisms of fluorocarbon polymers at ultra low-k (ULK) surfaces. As prototypical example we study a C2F4-molecule adsorbed at a passivated SiO2:CH3(001) surface. The calculated adsorption energies between 1.37 and 1.95 eV imply a chemisorption bonding mechanism. The detailed analysis of all investigated structures provides a simple rule to make a rough estimate of the stability of adsorbed fluorocarbon polymers. In addition, an adsorption pathway is proposed and used to suggest a possible adsorption mechanism, triggered by an electron transfer between the ULK surface and the C2F4 molecule.