Design of cycloolefin maleic anhydride resist for ArF lithography

Recently reported ArF positive photoresists can be classified into three groups: derivative methacrylate copolymers (methacrylate resist), methacrylate copolymers functionalized with pendant alicyclic moieties (alicyclic resist), and cycloolefin-maleic anhydride copolymers (cycloolefin resist). Each system has its own advantages and drawbacks from the viewpoint of lithographic properties. Methacrylate resist has been used for the assessment of ArF lens performance. However, it is hard to apply them in real device process because of its low plasma-etch resistance. Previous studies have reported that alicyclic resists possess adequate etch resistance with the help of cyclic carbon units, however these resists show poor adhesion and seldom dissolve in 2.38% TMAH developer. The cycloolefin resists will be good candidate for addressing the trade-off between etch resistance and requisite material properties for lithographic performance because these resists, unlike methacrylate-based resists, contain large quantities of alicyclic structures directly in the polymer backbone and such properties as dissolution, adhesion can be readily controlled by incorporation of-COOH and -OH functional groups into cycloolefin structures. We have synthesized poly(2-hydroxylethyl 5-norbornene-2-carboxylate / t-butyl 5-norbornene-2-carboxylate / 5-norbornene-2-carboxylic acid / maleic anhydride; HNC / BNC / NC / MA) resists with a variety of functional groups and obtained lithographic performance using ArF stepper(0.6NA). In this paper, we will describe the basic idea for designing of the novel olefin resist and demonstrate lithographic capabilities, especially in terms of process window for 130nm feature. We believe that both off-axis illumination and bottom anti-reflective technologies should be applied in order to obtain wider process window.