Highly hydroxylated hafnium clusters are accessible to high resolution EUV photoresists under small energy doses

Yu-Fang Tseng; Pin-Chia Liao; Po-Hsiung Chen; Tsai-Sheng Gau; Burn-Jeng Lin; Po-Wen Chiu; Jui-Hsiung Liu

doi:10.1039/d3na00508a

Highly hydroxylated hafnium clusters are accessible to high resolution EUV photoresists under small energy doses

Nanoscale Adv. 2023 Nov 10;6(1):197-208. doi: 10.1039/d3na00508a. eCollection 2023 Dec 19.

Authors

Yu-Fang Tseng¹, Pin-Chia Liao¹, Po-Hsiung Chen^{2

3}, Tsai-Sheng Gau^{2

3}, Burn-Jeng Lin^{2

3}, Po-Wen Chiu^{2

3}, Jui-Hsiung Liu¹

Affiliations

¹ Department of Chemistry, National Tsing Hua University Hsinchu 30013 Taiwan rsliu@mx.nthu.edu.tw.
² TSMC-NTHU Joint Research Center, National Tsing Hua University Hsinchu 30013 Taiwan.
³ College of Semiconductor Research, National Tsing Hua University Hsinchu 30013 Taiwan.

Abstract

This work reports the success in accessing high-resolution negative-tone EUV photoresists without radical chain growth in the aggregation mechanism. The synthesis of a highly hydroxylated Hf₆O₄(OH)₈(RCO₂)₈ cluster 3 (R = s-butyl or s-Bu) is described; its EUV performance enables high resolution patterns HP = 18 nm under only 30 mJ cm^-2. This photoresist also achieves high resolution patterns for e-beam lithography. Our new photoresist design to increase hydroxide substitutions of carboxylate ligands in the Hf₆O₄(OH)₄(RCO₂)₁₂ clusters improves the EUV resolution and also greatly reduces EUV doses. Mechanistic analysis indicates that EUV light not only enables photolytic decomposition of carboxylate ligands, but also enhances the Hf-OH dehydration. One additional advantage of cluster 3 is a very small loss of film thickness (ca. 13%) after the EUV pattern development.