Thermal desorption spectroscopy of PTFE dielectric films deposited on silicon wafers

Fluoropolymers are receiving considerable attention for use as integrated circuit dielectric materials. There is considerable confusion regarding the thermal stability of these materials. It is desirable to discuss thermal stability in terms of the outgassing properties of thin films deposited onto silicon wafers, since this is a key indicator of the fitness for use of a given dielectric film technology. In this paper we discuss the various types of fluoropolymer films and review previously published data on their thermal stability. Two such fluoropolymers, polytetrafluoroethylene (PTFE) and a copolymer of tetrafluoroethylene and 2,2-bistrifluoromethy-1-4,5-difluoro-1,3-dioxole (TFE-PDD), have been previously proposed for use as integrated circuit dielectrics. Thermal Desorption Spectroscopy results for thin films of these two polymers are presented. These results show that PTFE has much lower outgassing than does TFE-PDD.