Study on thermal crosslinking reaction of o-naphthoquinone diazides and application to electrodeposition positive photoresist

The thermal reactions of o-naphthoquinone diazide (NQD) compounds as a mate rial for photoresists were studied in comparison with their photochemical r eactions. An NQD compound decomposed at around 140 degreesC and further rea cted in the presence of an alcohol in the solution to yield an indenecarbox ylic ester. The photochemical reaction of the NQD compound with alcohol als o provided the same ester in a solution, as expected. In a polymer matrix, the thermal reaction of a multifunctional NQD compound with a copolymer hav ing hydroxyl groups yielded sufficiently crosslinked structures at 140 degr eesC in 10 min. On the other hand, when the copolymer matrix containing the NQD compound was exposed to UV, and subsequently to heating (140 degreesC for 10 min), no crosslinked structure was obtained. Consequently, it was co nfirmed that the heating provides a large difference in solubility between unexposed and exposed areas, quite a useful feature from the viewpoint of e fficient development of photoimage. We have applied this finding to an elec trodeposition positive photoresist incorporating a post exposure bake (PEB) in resist processing. The FEB afforded a very wide process window in an al kaline developer. (C) 2001 Elsevier Science B.V. All rights reserved.