We have developed a silicon oxi-carbide and nitride (SiOCNH) barrier film to protect against copper (Cu) thermal diffusion by plasma-enhanced chemical vapor deposition (PECVD) using hexamethyldisiloxane, nitrous oxide (N2O), and ammonia (NH3) gases. We tried to enhance the Cu barrier property and etching selectivity for low dielectric constant (low-k) film by adding nitrogen (N) into the barrier silicon oxicarbide (SiOCH) film. The film protects against Cu thermal diffusion at 450degreesC for 4 h in N-2. The k value is lower than that for PECVD silicon nitride (SiN) and silicon carbide (SiC) films, but is slightly larger than that of PECVD SiOCH film; it is in the range of 4.17 to 5.21. The leakage current is as low as the value of PECVD SiN film; it is in the range of 10(-9) to 10(-10) A/cm(2) at 1 MV/cm. This value decreases with increasing NH3 flow rate. However, Cu thermal diffusion increased with increasing NH3 flow rate. The diffusion depth is less than 20 nm. The diffusion behavior can be explained by the result that diffusion is controlled by the small pore size, high density, and small compressive stress in SiOCNH film. The average pore size is smaller than 0.49 nm, which is generally smaller than that of SiOCH film deposited using N2O gas. The film density is greater than 2.14 g/cm(3), which is larger than that of SiOCH film. The etching selectivity to silicon oxide deposited by PECVD using tetraethoxysilane (PECVD tetraethylorthosiloxane, TEOS SiO2) film is similar to15. The dynamic hardness is almost the same as the value of quartz and is 2.0 to 2.5 times larger than the value of PECVD TEOS SiO2 film. The Young's modulus was similar to2.0 and 2.5 times larger than the values of quartz and PECVD TEOS SiO2 film, respectively. The adhesion strength on Cu is the same as that of PECVD SiOCH film and slightly smaller than that of PECVD SiN film. The desorption of ammonium (NH3+) ions from SiOCNH film, which is known as the cause of poisoned via-holes, is very low. (C) 2003 The Electrochemical Society.