Rinse additives for line edge roughness control in 193 nm lithography

Abstract

Resist technologies that will enable next-generation lithography (NGL) such as extreme ultraviolet lithography (EUV) will require tighter control of critical dimension (CD) with appropriate reduction of line edge roughness (LER) of resist features to levels that seem unrealizable today. Given the delicate balance existing between LER, resolution and sensitivity that is associated with photoresist patterning, alternative processing methodologies that can address such parameters individually are required. In this work, a post-processing method designed to control LER is proposed based on the ability of an additive-containing rinse to condition the surface of photoresist patterns. Organic salts added to the final rinse used to quench the development process are found to be particularly effective towards this end. LER reduction up to 15% was observed for a broad range of 193 nm resist systems, while preserving the integrity of the pattern profiles. The dependence of LER reduction on additive concentration was investigated and the limited improvement observed was explained based on the tendency of the additive to self-aggregate. Finally, the advantage of including an additive in the rinse step instead of using an additive-containing developer is discussed in terms of critical dimension bias and overall image integrity control.