Phenolic molecular glasses as resists for next generation lithography

In this contribution, we describe our efforts to develop novel chemically amplified molecular glass (MG) photoresists based on bulky phenol structures. In contrast to conventional polymeric materials, MG resists possess distinct advantages, such as smaller molecular size and uniformity in composition. A number of compounds which possess rigid aromatic backbones were synthesized in our laboratories and evaluated for electron beam lithography. Herein, two new MG photoresists are discussed in terms of their physical and lithographic properties. In the first section, we introduce tert-butoxycarbonyl (t-Boc) protected 'Noria-Boc' photoresists as a promising candidate for next generation lithographic technique. Noria-Boc was synthesized through a condensation reaction between resorcinol and 1,5-pentanedial. After protection with di-tert-butyl dicarbonate [(t-Boc)₂O], the cyclic, bulky and amorphous material was characterized by a high glass transition temperature (T_g > 120 °C) and excellent film-forming properties. Post-exposure bake at 140 °C was necessary to ensure complete development of the exposed area and produced sub-100 nm lines. In the second part, we describe the synthesis and lithographic evaluation of partially t-Boc-protected bulky phenol 'CR1'. CR1 is also characterized by high glass transition temperature (T_g ≈ 130 °C) and good film-forming properties. Post-apply bake at 130 °C and post-exposure bake above 130 °C were necessary to ensure good contrast under deep UV (DUV) exposure conditions.