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 O(2) and Ar addition causes large sidewall damage. O(2)-added etch condition, as well as the O(2) ash process, produces oxygen radicals, which extract CH(3) groups from porous low-k films. On the other hand, Ar plasma does not efficiently extract CH(3) groups differently from O(2) plasma, but it changes the bonding states of CH(3) groups and causes H(2)O 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.