FLUORINATED SILICON-NITRIDE FILM FOR THE BOTTOM ANTIREFLECTIVE LAYER IN QUARTER MICRON OPTICAL LITHOGRAPHY

Fluorinated silicon nitride thin film as a bottom antireflective layer (BARL) material, being suitable for line-patterning in 0.25 mu m KrF excimer laser (248 nm) lithography, has been studied by film fabricati on/characterization and computer simulation, Three-dimensional reflect ance simulation process suggests that the 0% reflectance between photo resist (PR) and BARL can be achieved by selecting proper combinations of film optical properties such as refractive index (n), extinction co efficient (k) and thickness (d). For the PR/300 Angstrom BARL/c-Si or PR/300 Angstrom BARL/W-Si structure at a wavelength of 248 nm, the sim ulation process reveals that nearly 0% reflectance could be obtained w hen the n and k values of the film are 2.109 and 0.68 or 2.052 and 0.5 92 respectively. The fluorinated silicon nitride films prepared by ICP enhanced CVD have been evaluated with the variations of NF3 flow rate s under the two conditions of SiH4:N-2 = 2:15 and 3:20 (seem). The fil m n and k values at 248 nm vary in the ranges of 1.665-2.352 and 0.007 -0.695 respectively, depending on gas flow ratio. As it is very sensit ive to the film thickness, the reflectance could be reduced, using com poter simulation, to almost 0% by changing the film thickness. Further more, the ARL performance for 0.25 mu m line/space processed by the Kr F excimer laser stepper and the stripping ability/selectivity show thi s material to be a superior candidate for deep-UV microlithography app lications.