Elucidation of Structure-Property Relationships in Polymers for Microelectronics Using Computer Simulation

摘要

The origin of the rather unique relationships between molecular structure and physical properties in polymers used for microelectrionics is often difficult to ascertain. These polymers often have rather unique structures designed to optimize properties in a number of disparate areas required by the microelectronics industry. Here we illustrate the utility of both a specific and general application of molecular-level simulation to elucidate the origin of such structure-property relationships. A series of simulations of poly(norbornene) synthesized for application as a photoresist were carried out to understand this polymer's anomalous dissolution behavior. While this polymer has desirable qualities including thermal stability and optical transparency at 193nm and 157nm wavelengths, it dissolves more rapidly with increasing molecular weight over a specific range of molecular weights. Molecular simulation results suggest that this anomalous dissolution behavior is a result of the unique conformation adopted by this polymer. Generic simulations on ultra-thin films were carried out to provide insight into the seemingly contradictory behavior observed in physical properties of these films. Experimental evidence indicates that the glass transition temperature (Tg) decreases with decreasing film thickness while the small-molecule diffusivity also decreases. While the decreasing diffusivity can be explained by the increased contribution of the high mobility of the free surface of the film, however this increased mobility cannot explain the observed decrease in diffusivity. Recent molecular-level simulations suggest a single mechanism to explain these disparate phenomena. An understanding of both these phenomena is important in the design of the next generation of photoresist polymers.