Effective repair to ultra-low- k dielectric material ( k ∼2.0) by hexamethyldisilazane treatment

Abstract

O 2 plasma ashing is commonly used to remove photoresist. The effect of O2 plasma ashing on the porous organosilicate glass (CH3SiO1.5)n, one of the spin-on materials, is investigated. O2 plasma can oxidize the methyl groups in porous organosilicate glass (POSG), which leads to the formation of Si–OH groups. The hydrophilic Si–OH groups will induce moisture uptake so that electrical degradation will occur in POSG film. Pure hexamethyldisilazane (HMDS) vapor (100% HMDS) can react with the Si–OH groups in POSG film. It converts hydrophilic Si–OH groups into hydrophobic Si–O–Si(CH3)3 groups against moisture uptake. The leakage current density decreases by a factor of 2–3 and the dielectric constant decreases from 3.62 to 2.4 when O2 plasma-damaged POSG undergoes HMDS treatment at 80 °C for 15 min. Therefore, HMDS treatment is the effective technique to repair the electrical degradation to POSG film during photoresist stripping processing.