Thin film buckling as a method to explore the effect of reactive rinse treatments on the mechanical properties of resist thin films

As integrated circuit fabrication continues to advance towards the 32 nm node and below, it has become increasingly apparent that the use of ultrathin films and polymer features will be required. Though it has been widely accepted that the properties of polymers on the nanoscale can differ significantly from their bulk counterparts, the extent of such deviation is the subject of much debate and concern. Furthermore, most studies have focused on elucidating the differences in the thermal properties of micro- and nano-scale polymer films as determining the mechanical properties of ultrathin films can be somewhat cumbersome. In order to study the modulus of polymer thin films we have implemented a thin film buckling technique wherein a polymer film is floated onto a pre-strained PDMS substrate. Release of the strain, results in the buckling of the polymer film and provides the opportunity to accurately determine the modulus of polymer thin films with thicknesses down to 20 nm. This thin film buckling strategy was also used to probe the effect of thickness on the modulus of the ESCAP-1 thin films. Finally, a reactive rinse method was employed whereby the hydroxyl functional groups of the resist were cross-linked via a dicarboxylic acid using carbodiimide chemistry as a potential method to ultimately enhance lithographic patterning performance. The effect of the reactive rinse on the modulus of the ESCAP-1 thin films was analyzed and it was found that the application of the reactive rinse resulted in a clear increase in the modulus of the polymer films. Also, quartz crystal microbalance (QCM) supporting the confinement of the crosslinking agents to the surface will be discussed.