Do not always blame the photons: Relationships between deprotection blur, line-edge roughness, and shot noise in extreme ultraviolet photoresists

Abstract

A corner rounding metric has been used to determine the deprotection blur of Rohm and Haas XP 5435, XP 5271, and XP 5496 extreme ultraviolet (EUV) photoresists as base wt % is varied, an experimental open platform photoresist (EH27) as base wt % is varied, and TOK EUVR P1123 and FUJI 1195 photoresists as postexposure bake temperature is varied. In the XP 5435, XP 5271, XP 5496, and EH27 resist platforms, a six times increase in base wt % reduces the size of successfully patterned 1:1 lines by over 10nm and lowers intrinsic line-edge roughness (LER) by over 2.5nm without changing deprotection blur. In TOK EUVR P1123 photoresist, lowering the PEB temperature from 100to80°C reduces measured deprotection blur (using the corner metric) from 30to20nm and reduces the LER of 50nm 1:1 lines from 4.8to4.3nm. These data are used to drive a lengthy discussion about the relationships between deprotection blur, LER, and shot noise in EUV photoresists. The authors provide two separate conclusions: (1) shot noise is probably not the dominant mechanism causing the 3–4nm EUV LER floor that has been observed over the past several years; (2) chemical contrast contributes to LER whenever deprotection blur is large relative to the printed half-pitch.