New Polymers with Acid Labile Crosslinked Units and their Performance in Deep-UV Photoresists

抄録

The concept of crosslinked polymers linked via an acid labile unit is extending the utility of acetal protected polyhydroxystyrene. These units, which are formed during a transacetalization reaction, are cleaved by the photogenerated acid in the exposed areas and remain in the unexposed areas. The large molecular weight difference between exposed and unexposed areas of the resist leads to improved resolution capability. The link between the polymer chains is introduced by an aliphatic bifunctional alcohol, bridged via acetal moieties to the phenolic moieties. The molecular weight distribution is proportional to the amount of the alcohol. The polymer structures were evaluated by nuclear resonance spectroscopy and gel permeation chromatography. Photoresist formulations based on these polymers have improved thermal stability of the patterns. In addition to good post exposure delay, these formulations show an excellent soft bake delay time behavior.