Photochemical proton generation mechanism from onium salts.
- 1 January 1990
- journal article
- Published by Technical Association of Photopolymers, Japan in Journal of Photopolymer Science and Technology
- Vol. 3 (3) , 249-258
- https://doi.org/10.2494/photopolymer.3.249
Abstract
A new mechanism which is simple and common for all opium salts were proposed on the photochemical proton generation process in resist systems, from the theoretical aspect based on quantum chemical calculations. The primary product generated from the photochemical reaction is an aryl cation Ar+, i.e., for aryldiazonium salts [Figs. 2 and 3]: (ArN2)+X-→Ar++N2+X-, for diaryliodonium salts: (Ar2I)+X-→Ar++ArI+X-, for triarylsulfonium salts [Table 1]: (Ar3S)+X-→Ar++Ar2S+X- where X- is SbF6-, AsF6-, PF6-, BF6-, CF3SO3-, etc. The secondary proton generation reactions are [Figs. 4, 5 and 6], Ar++H2O[ROH]→(ArOH2) +[(ArOHR)+] (ArOH2)+[(ArOHR)+]→ArOH[ArOR]+H+X- where H2O and ROH are a water molecule at the air interface and such protic species as novolak, poly(vinylphenol), poly(vinylalcohol), etc., respectively. Since the chemical amplification in resist systems originates from the photochemically generated acid H+X-, we can conclude from this research that the sensitivity of an onium salt as a photo-initiator is determined by the species of its anionic part X-. This conclusion is consistent with experiments where the sensitivity decreases in the order SbF6->PF6->BF6-.Keywords
This publication has 0 references indexed in Scilit: