Properties of Low-k Copper Barrier SiOCH Film Deposited by PECVD Using Hexamethyldisiloxane and N2O

1. Properties of Low-k Copper Barrier SiOCH Film Depositedby PECVD Using Hexamethyldisiloxane and N2O Tomomi Ishimaru, Yoshimi Shioya, Hiroshi Ikakura, Mamoru Nozawa, Shoji Ohgawara, Toshiyuki Ohdaira, Ryochi Suzuki, and Kazuo Maeda Journal of The Electrochemical Society (2003)

2. Introduction To decrease RC delay time, interconnection resistance and interlayer capacitance has been reduced by using low-k dielectric instead of conventional tetraethoxysilane (TEOS) SiO2 film deposited by plasma-enhanced chemical vapor deposition (PECVD). However, Cu interconnection has several disadvantages for application to the process technology. For example, Cu film is easily oxidized, and Cu atoms or ions easily diffuse into the low-k interlayer dielectrics by thermal annealing or electric field. Therefore, it is necessary to prevent Cu diffusion by using a barrier film deposited between the Cu interconnection and low-k film. For this purpose, SiN film deposited by PECVD has been used as a Cu barrier film. The PECVD SiN film has low leakage current, which makes it superior as a barrier film. We have successfully developed the barrier SiOCH film for copper thermal diffusion by PECVD using hexamethlydisiloxane (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 450oC for 4h in nitrogen (N2).

3. Experimental The Cu barrier SiOCH film for copper thermal diffusion by PECVD using HMDSO and N2O gases. The flow rate of HMDSO was 50 cm3/min, and the flow rate of N2O was changed from 0 to 800 cm3/min. The deposition pressure was 1 Torr, the deposition temperature was 375oC at 1 Torr, and the bias power of 380 kHz was 150W. The film was characterized by the following methods. [[ ellipsometer : thickness, refractive index FTIR (Fourier transform infrared spectroscopy), RBS (Rutherford backscattering spectroscopy), HFS (hydrogen forward scattering spectroscopy), AES (Auger electron spectroscopy) : chemical bonding, composition, density TDS (thermal desorption spectroscopy), APIMS (atmospheric pressure ionization mass spectroscopy) : thermal stability of the barrier PALS (positronium annihilation lifetime spectroscopy) : pore size, pore distribution ]] Cu diffusion properties were studied by the current-voltage (I-V) method and SIMS (secondary ion mass spectroscopy)

4. Result and Discussion