Bottom antireflective coatings for ArF KrF and i-line applications: a comparison of theory design and lithographic aspects

摘要

Abstract: The present paper discusses theory, design andproperties of bottom anti-reflective coatings (BARCs)for deep UV and i- line applications. All BARCs areinterference devices, and as such their opticalconstants are optimal only for certain combinations ofthickness and the real and imaginary parts of therefractive index. Maps of the optimality conditions inthe parameter space will be provided. The design ofBARCs for various exposure wavelengths involveschoosing the right dye molecules capable of highlyabsorbing at the particular wavelengths and optimizingthe etch rates of the resulting film sand fine tuningthe formations for best lithographic performance. At anexposure wavelength of 365 nm, dye compounds such asamino aromatic or azo type compounds can be used, for248 nm it is necessary to use fused rings such asanthracene to have sufficient absorption, and in thecase of 193 nm exposures simple benzene or phenoliccompounds exhibit the required d absorbance. Since thedye molecules are invariably aromatic or fused rings,it is necessary to balance the absorption propertyversus the etch rate by incorporating non-aromaticmoieties. Further, the BARC formulations need to befree from intermixing, formation of foot or undercut inorder to obtain fine resist patterns. Our developmentefforts on BARCs have led to the AZ EXP ArF, KrF andBARLi series of BARCs designed for 193, 248 and 365 nmwavelength exposures, respectively. Lithographic dataof some of these products will also be presented withthe emphasis on the AZ EXP ArF-1 material designed for193 nm exposure. !8