Characterization of Negative-Tone Molecular Resist for EUV and EB Lithography

In order to enable design of a negative-tone polyphenol resist using polarity-change reaction, five resist compounds (3M6C-MBSA-BLs) with different number of a functional group of γ-hydroxycarboxyl acid were prepared and evaluated by EB lithography. The resist using a mono-protected compound (3M6C-MBSA-BL1a) showed 40-nm hp resolution at an improved dose of 52 μC/cm2 probably due to removal of a non-protected polyphenol while the sensitivity of the resist using a compound of protected ratio of 1.1 on average with distribution of different protected ratio was 72 μC/cm2. A di-protected polyphenol was synthesized by a new synthetic route of 3-steps reaction, which is well-suited for mass production of the molecular resist compounds. The resist using di-protected compound (3M6C-MBSA-BL2b) showed 40-nm hp resolution at a dose of 40 μC/cm2, which was faster than that of mono-protected resist. Fundamental EUV lithographic evaluation of the resist using 3M6C-MBSA-BL2b by an EUV open frame exposure tool (EUVES-7000) gave its estimated optimum sensitivity of 7 mJ/cm2 and a proof of fine development behavior without any swelling.