A HFIPS-based Polymer Approach for 157 nm Single Layer Photoresist

Resist materials for 157 nm lithography is believed to be one of the key technology for producing patterns below 70 nm. Many different types of fluorine-containing polymer platforms have been energetically pursued by a number of researchers, and some of them appear to be promising in giving a high transparency that has been the essential challenge in realizing this technology. One of the polymer platforms that the authors believe useful for 157 nm is the polymer having hexafluoroisopropanolstyrene (HFIPS) monomer unit in their backbones. The lithographic potential of the HFIPS-based polymer system was demonstrated with the fact that a prototype resist from this system was able to print a 75 nm line and space 1:1 pairs with an attenuated PSM under 0.60 NA stepper exposure. The paper will also discuss etch resistance of the HFIPS-based polymer system. It is generally thought that etch rate of resist films are mainly affected by their polymer compositions or structures but there are few reported on the influence of the other components in resist formulation. The authors found that the concentration of PAG and quencher influenced both etch rate and resist surface roughness after the etch in this materials system, which implied there are some more room for further etch resistance improvement.