Properties of low-k copper barrier SiOCH film deposited by PECVD using hexamethyldisiloxane and N2O

We have successfully developed the barrier SiOCH film for copper thermal diffusion by plasma-enhanced chemical vapor deposition (PECVD) using hexamethyldisiloxane (HMDSO) and nitrous oxide (N2O). We attempted to lower the k value and the leakage current by adding oxygen into the barrier silicon carbide (SiC) film. The film can protect Cu thermal diffusion at 450degreesC for 4 h in nitrogen (N-2). The k value is lower than that for PECVD silicon nitride (SiN) and SiC films, and is almost the same as that of PECVD silicon dioxide (SiO2) film; it is in the low range of 4.08-4.30. The leakage current is as low as the value of PECVD SiN film, 10(-9) to 10(-10) A/cm(2) at 1 MV/cm. The diffusion mechanism was studied compared with oxygen radical, oxygen ion, and water vapor. The diffusions are controlled by the size of the diffusion species, the average pore diameter, and the density of the SiOCH film. The barrier ability for Cu thermal diffusion is caused by the average pore size smaller than 0.51 nm and film density larger than 2.06 g/cm(3). The desorption of ammonium (NH3+) ions from SiOCH film, which is known as the cause of the poisoned via hole, is very low. (C) 2003 The Electrochemical Society.