High refractive index material design for ArF immersion lithography

High-refractive-index fluids (HIFs) are being considered to replace water as the immersion fluid in next generation 193nm immersion scanner. At SPIE 2006, we have demonstrated the attractive optical properties and good imaging performance for our HIF candidates, HIL-001 and HIL-002. In this paper, we will describe our latest results on the remaining issues for the practical application of HIF candidates, as well as introduce 3 rd generation fluids for the further extension of ArF immersion lithography. In order to improve the fluid transparency, we have tried two approaches. One is the improvement of transparency for HIL-001 based on a refining technology and the other is to develop a novel HIF candidate by using computational chemistry, which is named HIL-203. By passing through a suitable refining unit, HIL-001 can reach a transmittance of >99%/mm, which is as high as water. This new purification method can be applied to an on-site reuse system. It was also found that the refining unit was very effective to eliminate the impurities coming from the photo-degradation of HIL, chemical substances contamination under the air exposure, and leaching of resist components such as photo-acid generator or quencher. We have developed a new fluid for 3 rd generation immersion fluids. It had a higher refractive index than that of HIL-001 or HIL-203; however, it still falls short of our target value. Additionally, by using a novel design concept, we have developed a top-coat with high refractive index for HIL immersion lithography, which gave an appropriate contact angle for scanning exposure.