Effectiveness of Dimethyl Carbonate and Dipivaloyl Methane Chemicals for Internal Repair of Plasma-Damaged Low-k Films

Abstract

We propose the use of methylating chemicals to repair plasma-damaged sites in low-k films. Dimethyl carbonate (DMC) and dipivaloyl methane (DPM) were selected as the methylating chemicals to supply methyl (CH3) groups into the bulk of damaged porous SiOCH films. The absorption of water into the damaged films was fully suppressed by the DMC repair treatment. The relative dielectric constant, which was increased from the value of 2.4 in the as-grown porous SiOCH film to 3.1 by plasma processes, recovered to 2.6 owing to the DMC treatment. In the case of the DPM repair treatment, the relative dielectric constant showed an almost full restoration from a value of 3.8 in the damaged film. To discuss the chemical reaction during the DMC repair treatments, SiO2 and the damaged porous SiOCH films subjected to the treatments were analyzed using time-of-flight secondary ion mass spectrometry and Fourier-transform infrared spectroscopy. The results can be explained using the model showing that the methyl and methoxy groups generated via the decomposition of DMC molecules react with silicon and oxygen sites in the films.