Optimization of DUV Negative Resists for 0.15 .MU.m Lithography.

Abstract

Recent performance improvements of a negative tone chemically amplified DUV resist consisting of a hydroxystyrene based copolymer, a melamine crosslinker, a photoacid generator (PAG) and certain amine additives are described. The general trends of formulation and process changes on the lithographic performance were investigated using a response surface method. PAG concentration variations and optimization of the prebake conditions allowed for the elimination of microbridgmg in the subquarter micron region. The pattern profiles were improved by the optimization of the polymer properties and the selection of a specific amine/ammonium hydroxide combination. The effects of certain polymer properties and of individual amine components are discussed in more detail and a correlation with their structures is given based on dissolution rate measurements. The optimized resist material has a resolution potential below 0.15 µm (NA = 0.55) combined with a large depth of focus (> 1.0 µm @ 0.15 µm iso lines), acceptable iso-dense bias, and small sensitivity towards changes in the post exposure bake conditions.

The link between nanoscale feature development in a negative resist and the Hansen solubility sphere

“…In addition, as χ decreases, there appear to be more “bridges” at comparable line widths (Figure 5, red circles). These bridges are often a sign of swelling19 but authors also attributed it to redeposition of polymer material diffusing out of the cross‐linked matrix redepositing during the rinsing and drying process 20. Line quality can be improved by exposing with a different write strategy (Fig.…”