Low-Damage Damascene Patterning Using Porous Inorganic Low-Dielectric-Constant Materials

The degradation of porous low-dielectric-constant (low-k) materials, such as porous methyl silsesquioxane (MSQ) and porous chemical-vapor-deposited SiOCH films, by damascene etch and ash processes has been investigated. The influence of etch damage becomes relatively stronger as ash damage improves. The etch damage to porous low-k dielectric is found particularly at the sidewall of the isolated lines. By investigating the influence of etch conditions on the damage, it is found that O2 and Ar addition causes large sidewall damage. O2-added etch condition, as well as the O2 ash process, produces oxygen radicals, which extract CH3 groups from porous low-k films. On the other hand, Ar plasma does not efficiently extract CH3 groups differently from O2 plasma, but it changes the bonding states of CH3 groups and causes H2O adsorption. This change in film characteristics increases dielectric constant. Finally, we successfully achieved low-damage dual damascene patterning using a porous SiOCH material whose dielectric constant is 2.2.