Optical superlattices—a strategy for designing phase-shift masks for photolithography at 248 and 193 nm: Application to AlN/CrN

Abstract

This letter illustrates with AlN/CrN multilayers that optical superlattices, comprised of multilayers of a uv transmitting dielectric layer and a metallic layer, offer a systematic approach to design and fabricate partially transmitting, phase-shift masks for photolithography. From the measured optical constants of sputtered AlN/CrN multilayers, it was found that films had-phase shift and tunable optical transmission between 5% and 15% at 365, 248, and 193 nm. We compared the optical properties of sputtered AlN/CrN multilayers to ''ideal'' superlattices, calculated from the measured optical properties of individual thick CrN and AlN layers, and to compositionally equivalent psuedobinary alloys of (AlN) 1Ϫx (CrN) x. Although optical properties for all three systems were nearly the same, which is attractive because it implies wide process lattitude, we found systematic differences that were attributed to their individual structures. A phase shift mask with 6% transmission at 365 nm was fabricated with a 1650-Å-thick (25 Å AlNϩ25 Å CrN) multilayer film.

Immersion Lithography: Photomask and Wafer-Level Materials

“…We developed multilayer films of AlN with TiN (optical superlattices) produced by sequential multilayer ion beam deposition, in which the bilayer thickness was kept to less than λ/20 (i.e., less than 10 nm). These films were thus optically homogeneous and behaved optically as uniform films, even though the AlN and TiN amounts in each bilayer were the variables used to produce optical tunability (57). This material family produced APSMs with transmissions from 6% to 20% with a 180 • phase shift for both 248 and 193 nm (58).…”

Theoretical calculation of half-metallic ferromagnetism in Al1-xVxN compound

“…Aluminum nitride (AlN) normally crystallizes in the wurtzite structure (Beloufa et al, 2009). This material has recently attracted the attention of researchers due to their excellent properties, has been widely used in: design Light-Emitting Diodes (LEDs) and Laser Diodes (LDs) (Taniyasu and Kasu, 2008), in electronic packaging material and applied to optical disk as well as lithographic photo masks (Jonnard et al, 2004;Carcia et al, 1996;Carcia et al, 1997). Due to its stability, high temperature, considerable thermal conductivity, low thermal expansion and high resistance to gases and chemicals (Beheshtian et al, 2012) has been used in many electronic devices which must work in high temperature, high power, and corrosive ambients.…”

TiSi-nitride attenuating phase-shift photomask for 193-nm lithography

“…At these shorter wavelengths, however, only a few usable materials exist with band gaps greater than 6 eV. 5,6 In addition to this limiting feature, these materials also need to satisfy 11 lithographic properties: phase-shift, transmission and reflection at the lithographic wavelength, inspectability, etch selectivity to quartz and resist, chemical durability, radiation durability, film adhesion to quartz, and low film stress.…”