Review of technology for 157-nm lithography

Abstract

This paper outlines the critical issues facing the implementation of 157-nm lithography as a sub-100-nm technology. The status of the present technology for mask materials, pellicles, optical materials, coatings, and resists is presented.

Nanolithography by elastomeric scattering mask: An application of photolithographic standing waves

“…To this end, we note that sidewall corrugations in literature have been observed with depths as shallow as ϳ11 nm. 7 In closing, we have demonstrated a lithographic technique that realizes ϳ80 nm features in photoresist from micron sized features on quartz masks. This has been achieved through the exploitation of a feature of photolithography that has until now been consistently targeted for elimination.…”

Nano‐ and Microstructuring of Polymers

“…New grades of modified fused silica have been developed showing weak absorption in this wavelength region, making possible the production of lithographic masks. Calcium fluoride meets also the requirements for implementing the optics for the illumination and projection systems [11]. More problematic is the use of EUV and X-ray lithography, due to the lack of transparent materials to generate the masks and the necessary optics for the lithographic process.…”

Light induced adsorption of Si nano-composites in LiF crystals at 157nm

“…In lithography, the development of EUV and VUV wet and dry technologies at 193 and 157 nm [13][14][15][16][17], still faces open issues. Si containing resists for bi-layer applications appear suitable especially at 193 nm [18][19][20][21][22], however out-gassing of resists at short lithographic wavelengths imposes serious problems for the optical system by contaminating it [14][15][16]. Regarding optical materials, the large value of the band gap and the sharp transmission cut-off edges of the fluoride dielectric crystals makes them ideal candidates to construct the components of the high-resolution optical system for lithographic VUV applications [17][18][19][20][21].…”

“…Si containing resists for bi-layer applications appear suitable especially at 193 nm [18][19][20][21][22], however out-gassing of resists at short lithographic wavelengths imposes serious problems for the optical system by contaminating it [14][15][16]. Regarding optical materials, the large value of the band gap and the sharp transmission cut-off edges of the fluoride dielectric crystals makes them ideal candidates to construct the components of the high-resolution optical system for lithographic VUV applications [17][18][19][20][21]. Up to now, the optics of the catadioptric projection system is made of wide band gap fluoride dielectric crystals such as CaF 2 [22][23][24].…”

“…Finally, the LiF crystal has the widest band gap [30] (larger than 11.80 eV for good quality material). Although it is softer, more sensitive to thermal shocks and to atmospheric moisture than CaF 2 it has been used as optical element for lithography at short VUV wavelengths (121 nm) and in space applications [8,18]. The LiF crystal could be grown easier from liquid melts at temperature of 840 8C, which is considerably lower than the melting temperature of CaF 2 at 1500 8C.…”