The Applicability of Fluorinated Silicon Nitride Film As Bottom Antireflective Layer In Deep Ultraviolet Lithography

This study describes the use of fluorinated silicon nitride film as a bottom antireflective layer (BARL) material suitable for line-patterning in quarter-micron KrF excimer laser lithography. For the structures of photoresist/BARL (300Å)/c-Si and photoresist/BARL (300 Å )/W-Si at a wavelength of 248nm, 0% reflectance could be achieved when the refractive index (n) and extinction coefficient (k) values of the film are 2.11 and 0.68 or 2.05 and 0.59, respectively. The fluorinated silicon nitride thin films on p-type (100) Si substrates obtained by inductively coupled plasma enhanced CVD have been evaluated with the variations of NF3 flow rates under the two conditions of SiH4:N2=2:15 and 3:20 (seem). The films optical constants and reflectance were investigated by spectroscopic ellipsometry combined with a reflectance simulation program. The film n and k values at 248nm vary in the ranges of 1.67~2.35 and 0.01~0.69, respectively, depending on gas flow ratio of SiH4:N2:NF3. Low reflectance of below 5% can be obtained from reflectance simulation for two deposition conditions with a BARL thickness of 300Å. In addition, the reflectance could be reduced to almost 0% by controlling film thickness. Finally, the antireflective layer performance was investigated using KrF excimer laser lithography.