Damage free cryogenic etching of ultra low-k materials

Cryogenic etching was applied to porous organosilicate (OSG) films. Plasma-induced damage was reduced due to the protective effect of etch by-products condensed in pores of low-k materials. Almost no carbon depletion was observed when the wafer temperature is below a certain critical level. Most of experiments were carried out with SF₆ plasma. The addition of SiF₄/O₂ into the gas discharge allows a further reduction of plasma-induced damage by formation of a SiO_xF_y passivation layer.