Novel deep UV photoresist with thermally crosslinkable photoacid generator
2001
The present authors have studied a novel system of deep UV photoresist based on thermally crosslinkable photoacid generators(TCL-PAG), which have two or three crosslinking groups on the same molecule that can be crosslinked to a binder resin of chemically modified poly (p-hydroxystyrene), referred to as PHST hereinafter, in the stage of prebaking via the reaction of their phenolic hydroxyl groups on the polymer chain with the crosslinking groups of TCL-PAG. Upon exposure and subsequent PEB, the crosslinkage with acetal structures is cleaved by photogenerated acids to give an unprotected phenol resin, alcohol and acetaldehyde. We investigated some structural effects on resolution, photospeed, line edge roughness and other functional properties of the resulting resists with different size of the protecting groups in a combination with different types of PAGs and bases added. KrF steppers of Nikon (NA:0.45) and ASML(NA:0.7) were used in the lithographic test with binary test masks. Various types of partially protected PHST derivatives were synthesized with different protecting groups to control the dissolution rate and the activation energy of the base resins. The resist pattern quality can be enhanced by using our new PAG system based on the thermal crosslinking mechanism. A combination of the acetal and carbonate protecting groups onto the PHS base resin with the TCL-PAG can also enhance the resist performance so that a minimum resolution of 130 nm with KrF exposure could be obtained.
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