Molecular resists for advanced lithography - design, synthesis, characterization, and simulation

Many problems exist in current photoresist designs that will limit their ability to obtain the performance required for future generations of IC devices. The biggest challenge is the inability to simultaneously optimize resolution, line edge roughness (LER), and sensitivity; this is known as the RLS trade-off. Even within the RLS trade-off, LER cannot be made as small as desired. The only way to escape the RLS tradeoff, or at least to improve it, appears to be development of completely new resist designs and resist material systems. That is the primary goal and focus of this thesis.;In order to probe the effects of changes in resist formulation and processing on RLS, a mesoscale kinetic Monte Carlo simulation of resists was developed and results and insights from that model are discussed in several chapters. Likewise, in order to better understand the effect of metrology on our understanding of the final resist relief image, a detailed SEM simulator was developed that allows for the probing of how LER is determined. Although several simulations were developed, much of the thesis is focused on the design, synthesis, and characterization of novel molecular resists. Several important structure-property relations were developed for the prediction of glass transition temperature (Tg) and to predict the solubility of a resist molecular in standard aqueous base developer. A study of the effect of structure on the photoacid generation behavior of non-ionic PAGs under high energy exposures such as e-beam and EUV provided useful insight on prediction of acid generation efficiency in these systems. The effect of the solubilizing mechanism in these molecular resists was also studied and important information regarding what approaches to avoid and which approaches work best was obtained.;A large amount of work was done on negative tone molecular resists that appear to provide an improvement to many of the problems such as pattern collapse and diffusion control while maintaining excellent resolution and good sensitivity. This family of resists has had a large effect on the outlook of negative tone resist for future patterning generations. Another completely new family of molecular resists was also developed based on using a single molecular species which consists of a molecular glass core compound that contains all of the functional groups required to act as a CAR including PAG functional groups, base solubilizing groups blocked by acid labile protecting groups, and a sulfonic acid anion that is directly attached to the molecular glass core. This approach, referred to as single component molecular resists, should completely eliminate inhomogeneity in the as-cast resist film. Along with these, several additional types of novel molecular resists were developed. Non-chemically amplified molecular resist were developed that leverage the dissolution properties of molecular resists to produce what appears to be a record low dose-to-clear for non-CARs. An additional family of molecular resists that thermally cross-link before exposure and are cleaved back to small molecules was also investigated with the idea of improving pattern collapse and potentially reducing photoacid diffusion. This resist family also allowed the comparison between development in organic solvent and aqueous base.