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

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 Hf 6 O 4 (OH) 8 (RCO 2 ) 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 Hf 6 O 4 (OH) 4 (RCO 2 ) 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.