Defect reduction by using a new rinse solution for 193-nm conventional and immersion lithography

Semiconductor manufacturing technology has progressed remarkably in recent years. This progress has been accompanied by demands to reduce the feature size used in photolithography processing, resulting in a reduction of the exposure wavelength from 248 nm (KrF laser) to 193 nm (ArF laser). ArF immersion lithography is now being actively researched and developed with the aim of implementing the 45-nm technology node. Chemically amplified (CA) resists have been introduced to cope with these reduced feature sizes, making it all the more important to reduce defects produced in the lithography process. In recent years, the behavior of defects in a CA resist has been clarified by studies involving various microprobe analysis techniques. Basically, it has been reported that water-soluble defects such as "satellites" and water-insoluble defects such as "resist residues" are generated by various factors. Furthermore, the reduction in pattern sizes has led to the identification of new types of resist-related defects such as "missing-hole" defects in contact-hole (C/H) patterns and "bridging" defects in line-and-space (L/S) patterns. Although the satellite, resist-residue, and missing-hole problems have been addressed by implementing new ideas such as extended rinse times, improved development recipes, and the introduction of post-development rinse stages and improved rinse recipes, it cannot be said that these measures are sufficient in terms of processing throughput or effectiveness. In this paper, we investigate the effect of adding chemical additives to the de-ionized water (DIW) rinse used in the development rinse process. Our studies confirm that these additives significantly reduce the quantity of minute defects generated on the wafer without degrading lithography performance, and thus help to improve process throughput. We also investigate the application of this method to immersion lithography, and confirm that this additive procedure also reduces the quantity of defects in immersion lithography processes.