Secondary patterning of UV imprint features by photolithography.
An acid-cleavable cross-linker (2,5-dimethyl-2,5-hexanediol dimethacrylate or DHDMA) was prepared and patterned with UV imprint lithography (UV-IL) to create cross-linked films that could be secondarily patterned in a subsequent photolithographic step. The thermal and acid-catalyzed decomposition of DHDMA films were measured with both attenuated total reflectance FTIR and ellipsometry, which showed that images could be formed in cross-linked films by exposure to 254 nm radiation in the presence of a polystyrene overcoat containing a photoacid generator (PAG). As a resist for imprint lithography, DHDMA could be patterned with feature sizes ranging from tens of micrometers to 120 nm, and in films with thicknesses from 2 m to 500 nm, whereas the second photolithographic step allowed the subsequent micrometer-sized patterning of these original features. The modular nature of this novel two-step patterning process allows the imprinting of DHDMA with functional comonomers such as p-acetoxystyrene, demonstrating the extension of this concept to additional chemistries and further tailoring of resist performance.