Novel developers for positive tone EUV photoresists

While much work has been done in the design of photo resist for EUV lithography, these materials have typically been optimized for so called "standard developer" i.e., 2.38% tetra methyl ammonium hydroxide. However we felt that it would be reasonable to consider specifically the developer as opposed to the resist design. Indeed it has been suggested that the polarity and cation size in developer are important positive tone resist performance. It is our hypothesis that a base that could wet and penetrate faster into partially deprotected resist could result in a faster photo speed, and thus make more process margin available for resist design; for example a slower system incorporating higher quencher loadings. Additionally, we sought to probe the effects of solvent polarity with varying amounts of non-aqueous solvent additive. By reorganization of the nascent solvent shell with the non aqueous additives, we sought to perturb the development kinetics and thus change the resist's performance envelope by accelerating photo speed and potentially increasing contrast. This approach has been applied to non chemically amplified resist to good effect. In the three positive tones EUV and a 193nm photo resist was evaluated with the prototype developers we found that the performance was profoundly impacted by these two probes (i.e. solvent polarity and cation hydrophobicity).