High-index materials for 193 nm immersion lithography

High index 193 nm immersion lithography: the beginning or the end of the road

“…In situ transmission was assessed periodically. After a total dose of 0.5x10 6 for the most recently grown material, batch 2, substantial absorbance "bleaching" was observed by 0.03/cm, base 10, as was mentioned above. We, thus, do not expect that LuAG laser durability will be an issue for using the material in production.…”

“…It should have a sufficiently high RI (n> 1.7 at 193 nm), sufficiently low absorption coefficient (<0.005/cm, base 10), and sufficiently low intrinsic birefringence (< 10 nm/cm). From extensive early materials studies, 6 the candidate material with the best chance of meeting such requirements is lutetium aluminum garnet, Lu 3 Al 5 O 12 . BaLiF, developed by Tokuyamar 7 , was also a potential candidate for a 1.55 NA optical system, but with only a moderate increase in RI up to 1.64 at 193nm (relative to quartz RI of 1.56), BaLiF lacked the extendibility to 1.70 NA commercialization.…”

Receding contact lines: From sliding drops to immersion lithography

“…This is a technique that is widely applied in semiconductor industry to achieve higher optical resolutions, and accordingly smaller dimensions [18,19]. The conventional Lithography method, which consists of the projection of light patterns through a lens on substrates, is improved by replacing the air between the lens and the substrate by a liquid with a higher refractive index (figure 1c).…”

High-Index Immersion Lithography

“…The intrinsic birefringence must be minimal to allow a correction to avoid introducing unacceptable aberrations in the final aerial image. The National Institute of Standards and Technology (NIST) has searched for high-index lens materials that meet the above requirements such as barium lithium fluoride (BaLiF 3 ) and LuAG (Burnett et al, 2006). BaLiF 3 developed by Tokuyama is available in various sizes with low absorbance (Nawata et al, 2007).…”