Influence of thermal treatment of low dielectric constant SiOC(–H) films using MTES/O2 deposited by PECVD

Low dielectric constant SiOC(–H) films are deposited on p-type Si(100) substrates by plasma enhanced chemical vapor deposition (PECVD) using methyltriethoxysilane (MTES, C7H18O3Si) and oxygen gas as precursors. The SiOC(–H) films are deposited at room temperature, 100, 200, 300 and 400 8C and then annealed at 100, 200, 300 and 400 8C temperatures for 30 min in vacuum. The influence of deposition temperature and annealing on SiOC(–H) films are investigated. Film thickness and refractive index are measured by field emission scanning electron microscopy and ellipsometry, respectively. Chemical bonding characteristics of as-deposited and annealed films are investigated by Fourier transform infrared (FTIR) spectroscopy in the absorbance mode. As more carbon atoms are incorporated into the SiOC(–H) films, both film density and refractive index are decreased due to nano pore structure of the film. In the SiOC(–H) film, CH3 group as an end group is introduced into –O–Si–O– network, thereby reducing the density to decrease the dielectric constant thereof. The dielectric constant of SiOC(–H) film is evaluated by C–V measurements using metal–insulator–semiconductor (MIS), Al/SiOC(–H)/p-Si structure and it is found to be as low as 2.2 for annealed samples deposited at 400 8C.