Extreme ultraviolet (EUV) lithography is expected to replace current photolithographic methods because of its improved resolution. The atomic photon absorption cross section is a central factor that determines an optimal element around which to base photoresist chemistry, and tin is a strong absorber for EUV photons (~92eV). A series of organo-tin oxo compounds are currently being studied for this application. Although films made from tin-based resists can be patterned, the mechanism (including radiation chemistry) is not yet well studied or understood. Researchers do not yet fully understand how the film changes chemically as photons and electrons interact with the organo-tin oxo compounds. From our previous studies, it has been observed that extremely low energy electron (even below 5 eV) can trigger a chemical change that converts a soluble resist material into an insoluble one. Research at the Center for Sustainable Materials Chemistry (CSMC) has been using electron, EUV photon, x-ray and helium ion beams of a range of energies to study the sensitivity of these films. To check for the film structure and composition, AFM (Atomic-force microscopy), RBS (Rutherford Backscattering Spectrometry), XPS (X-ray Photoelectron Spectroscopy) and TPD (Temperature Programmed Desorption) are used to examine as-deposited, exposed, and developed films. Results point to the strong possibility that ligand chemistry is critical in determining post-exposure solubility. By comparing compounds with same structure but different metal cores and local chemistries, it is possible to determine which of the factors play the dominant role in the total photon absorption efficiency. Future studies will also involve calculations that can shed more light onto the microscopic mechanism of patterning, including energy loss (in the resist) of the photoelectrons generated by the EUV source.

Characterization of n-BuSnOOH: Solution precursor identity and film quality

253rd National Meeting (2017)

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