Super-resolution fluorescence microscopy on E-beam resist film during electron beam exposure for mask patterning process

Abstract

The fabrication of highly qualified patterns for photomasks using an electron beam writer is one of the key methods to achieve the requirements for high-end semiconductor devices manufacturing. We demonstrate in-situ examination of morphology changes in the electron-beam resist using super-resolution single-molecule fluorescence microscopy. An integrated scanning electron and fluorescence microscope was used to apply different e-beam doses on a PMMA model resist doped with fluorophores. The experiment shows that the density of fluorophores decreases at accumulated e-beam doses, revealed by the increasing average distances between the neighboring fluorophores before and after the e-beam treatment. The observation coincides with the film thinning in the e-beam treated sample area under AFM. Combining the data from super-resolution microscopy and AFM, we could identify different e-beam impact that is associated with e-beam doses. Particularly, we could observe certain degree of resist degradation outside the exposed area when high doses are applied. The degradation might be correlated to effects such as resist outgassing. This proof-of-concept illustrates a faster alternative method to AFM for characterizing the resist's morphological changes during e-beam processes.

Keywords

• E-beam lithography
• Photomask
• Super resolution fluorescence microscopy
• E-beam resist