The present paper discusses theory, design and properties of bottom anti-reflective coatings (BARCs) for deep UV and i- line applications. All BARCs are interference devices, and as such their optical constants are optimal only for certain combinations of thickness and the real and imaginary parts of the refractive index. Maps of the optimality conditions in the parameter space will be provided. The design of BARCs for various exposure wavelengths involves choosing the right dye molecules capable of highly absorbing at the particular wavelengths and optimizing the etch rates of the resulting film sand fine tuning the formations for best lithographic performance. At an exposure wavelength of 365 nm, dye compounds such as amino aromatic or azo type compounds can be used, for 248 nm it is necessary to use fused rings such as anthracene to have sufficient absorption, and in the case of 193 nm exposures simple benzene or phenolic compounds exhibit the required d absorbance. Since the dye molecules are invariably aromatic or fused rings, it is necessary to balance the absorption property versus the etch rate by incorporating non-aromatic moieties. Further, the BARC formulations need to be free from intermixing, formation of foot or undercut in order to obtain fine resist patterns. Our development efforts on BARCs have led to the AZ EXP ArF, KrF and BARLi series of BARCs designed for 193, 248 and 365 nm wavelength exposures, respectively. Lithographic data of some of these products will also be presented with the emphasis on the AZ EXP ArF-1 material designed for 193 nm exposure.