Immersion microlithography at 193 nm with a Talbot prism interferometer

Abstract

A Talbot interference immersion lithography system that uses a compact prism is presented. The use of a compact prism allows the formation of a fluid layer between the optics and the image plane, enhancing the resolution. The reduced dimensions of the system alleviate coherence requirements placed on the source, allowing the use of a compact ArF excimer laser. Photoresist patterns with a half-pitch of 45 nm were formed at an effective NA of 1.05. In addition, a variable-NA immersion interference system was used to achieve an effective NA of 1.25. The smallest half-pitch of the photoresist pattern produced with this system was 38 nm.

DUV Interferometry for Micro and Nanopatterned Surfaces

“…On the experimental point of view, one of the difficulties for interferometry in the DUV range is due to the low coherence of available DUV lasers. As an example, typical coherence of ArF lasers is limited to a few hundreds of microns, which justifies efforts to develop specific experimental setup for short wavelengths (Figure 1 (Bourov et al, 2004), b) Lloyd setup (Raub & Brueck, 2003) and c) achromatic holographic configuration (Yen et al, 1992) Holographic grating formation has been proposed (Askins et al, 1992;Archambault et al, 1993). However, in all cases, it has been necessary to increase the spatial coherence and decrease the spectral emission band width of excimer lasers, which considerably increase the laser system complexity and demonstrations have been mostly done with 248 nm lasers.…”

“…However, in all cases, it has been necessary to increase the spatial coherence and decrease the spectral emission band width of excimer lasers, which considerably increase the laser system complexity and demonstrations have been mostly done with 248 nm lasers. -Several systems based on Compact size Talbot prism have been developed to fit with the different excimer wavelengths (193 nm, 248 nm), with periods down to 90 nm (Bourov et al, 2004). The reduced dimensions of the system are compatible with coherence requirements linked to excimer lasers and such configuration is compatible with immersion.…”

Experimental measurement of photoresist modulation curves

“…It has been implemented for printing on wafers, 4 and used in conjunction with immersion, 5 as well with water immersion and using ArF as the source. 6 This makes interferometric imaging an ideal solution for photoresist characterization, if the photoresist is intended for use in ArF immersion lithography.…”

Approaching the numerical aperture of water immersion lithography at 193-nm

“…A compact alternative to the Talbot interferometer is shown in the prism lens shown in Figure 3, which is also described in a paper by Bourov et al [5]. The lens is based on a fused silica prism with surfaces polished and coated to produce a magnification in the numerical aperture of a phase grating.…”