Properties of Low-k Cu Barrier SiOCNH Film Deposited by Plasma-Enhanced Chemical Vapor Deposition using Hexamethyldisiloxane and Ammonia Gases

Abstract

We developed SiOCNH films that act as a barrier to copper (Cu) thermal diffusion by plasma-enhanced chemical vapor deposition (PE-CVD) using hexamethyldisiloxane (HMDSO) and ammonia (NH3) gases. The k value is in the range of 3.87 to 5.48, which is lower than that of PE-CVD silicon nitride (SiN) and slightly larger than that of PE-CVD SiOCH. The leakage current is on the order of 10-9 to 10-10 A/cm2 at 1 MV/cm2, as low as the value of PE-CVD SiN film. The film can prevent Cu thermal diffusion at 450°C for 4 h in N2 ambient. The Cu thermal diffusion depth is less than 10 nm at a NH3 flow rate larger than 50 cc/min. The barrier ability of the SiOCNH film deposited using HMDSO and NH3 gases against Cu thermal diffusion is due to the average pore size being smaller than 0.52 nm, which is slightly larger than that of a CuO molecule, and the film density being larger than 1.83 g/cm3.