Electron-beam-induced freezing of a positive tone EUV resist for use in directed self-assembly applications

The commercialization of 32 nm lithography has been made possible by using double patterning, a technique that allows for an increased pattern density, potentially, through resist freezing and high precision pattern registration. Recent developments in directed self assembly (DSA) also uses resist freezing for stabilizing positive tone resists used in graphoepitaxy. We have developed a method of patterning an open source, positive tone EUV resist using electron beam lithography (EBL), and studied a novel way of freezing a positive tone EUV photoresists through electron beam induced crosslinking. Through metrological analysis, crosslinked pattern was observed to retain consistent critical dimensions (CD) and line-edge roughness (LER) after they were annealed at temperatures higher than the glass transition of the photoresist. This process has been used to freeze patterned EUV photoresists, which have been subsequently used for directed self assembly of PS-b-PMMA and has potential applications in double patterning in an LFLE scenario.