High-refractive-index fluids (HIFs) are being considered to replace water as the immersion fluid in
next generation 193nm immersion scanner. We have demonstrated the attractive optical properties for our HIF
candidates, HIL-001, HIL-203 and HIL-204. Especially, HIL-203 and HIL-204 have higher transmittance
compared to water. In this paper, we describe our latest results on the comparative evaluations including
photo-degradation behavior and lens contamination phenomenon in a flow system. For laser induced fluid
degradation behavior, it was shown the higher initial transmittance resulted in the higher laser durability.
However, the complicated phenomenon was observed for the lens contamination test. That is, HIL-204 with
higher initial transmittance showed higher lens contamination rate than HIL-203. From several analyses, the
complicated behaviors among HILs were speculated to be caused by the different nature of photo-degraded
impurities. In order to control the fluid transmittance change and suppress the lens contamination during
exposure, the refining process was definitely necessary for HIL reuse system. Based on the refining mechanism
and the refining material design, we have developed an appropriate refinement unit named Refine B. This
approach provided us with the result that Refine B could control the change of fluid transmittance and suppress
the lens contamination rate.
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 3rd 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 3rd 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.
ArF immersion lithography using a high-refractive-index fluid (HIF) is considered to be a promising candidate for the 32nm node or below. At SPIE 2005 we introduced a new immersion fluid, JSR HIL-1, which has a refractive index and transmittance of 1.64 and >98%/mm (193.4nm, 23 oC), respectively. With HIL-1 immersion and a two beam interferometric exposure tool, hp32nm L/S imaging has been demonstrated. In this paper, we will report another novel immersion fluid, HIL-2, which has a transmittance of >99%/mm, which is almost as high as that of water, and a refractive index of 1.65 (193.4nm, 23 oC). Furthermore, an ArF laser irradiation study has shown that the degree of photodecomposition for both HIL-1 and HIL-2 is small enough for immersion lithography application. A "fluid puddle" defect study confirmed that HILs have less tendency to form immersion-specific photoresist defects and the refractive indices of HILs were found constant under laser irradiation. Batch-to-batch variation in refractive index during manufacture of HILs was not observed. By refining prism designs, hp30nm L/S patterns have also been successfully imaged with two interferometric exposure tools and HIL immersion.
This paper describes the material characteristics for KrF-immersion lithography with a high refractive index fluid. We have obtained promising results in soaking experiments involving KrF lithography without topcoat film. Although water is currently used as the immersion fluid in 193nm lithography, providing suitable refractive index (n=1.44@193nm and n=1.37@248nm) and transmittance (>99%/mm), it is found to have leaching issues when used with KrF resist. On the other hand, our high refractive index fluid (JSR-HIL-001), which was developed for ArF immersion purposes, satisfies the following requirements: HIL-001 has indicated promising characteristics as a 248nm-immmersion fluid. The refractive index is 1.54@248nm and the transmittance is >99%/mm. In this paper the physical and chemical properties of HIL-001 for KrF-immersion fluid application are discussed in detail.
ArF immersion lithography is considered as the most promising next generation technology which enables to a 45 nm node device manufacturing and below. Not only depth of focus enlargement, immersion lithography enables to use hyper numerical aperture (NA) larger than 1.0 and achieve higher resolution capability. For 193nm lithography, water is an ideal immersion fluid, providing suitable refractive index and transmission properties. Furthermore the higher refractive index fluid is expected to provide a potential extension of optical lithography to the 32 nm node. This paper describes the material design for immersion lithography with high refractive index fluid. We have developed promising high refractive index fluids which satisfy the requirement for immersion fluid by screening wide variety of organic compounds. The physical and chemical properties of this high refractive index fluid are discussed in detail. Also the topcoat material which has good matching with high refractive index fluid is developed. While this topcoat material is soluble into aqueous TMAH developer, it does not dissolve into water or high refractive index fluid and gives suitable contact angle for immersion scan exposure. Immersion exposure experiments using high refractive index fluid with and w/o topcoat material was carried out and its lithographic performance is presented in this paper.