증착온도에 따라 형성된 SiOC(-H) 박막의 저유전율 특성 연구

Abstract

The SiOC(-H) thin films with low dielectric constant were deposited on p-type Si(100) substrates by using a transformer coupled plasma chemical vapor deposition (TCPCVD) system with a mixture of dimethoxydimethylsilane (DMDMS : Si(OCH3)2(CH3)2) and oxygen precursors. The SiOC(-H) film become oxygen rich, like SiO2, as we increase the substrate temperature, chemical properties and electric properties of the SiOC(-H) were changed. So the influence of substrate temperature on the properties of the SiOC(-H) films was investigated. The deposition rate and refractive index were analyzed using FESEM and ellipsometer, respectively. The chemical and structural nature of these films was characterized by using FTIR and XPS. The electric properties of the SiOC(-H) films were investigated by using MIS structure. As the substrate temperature increases, the apparent activation energy of such thermally inactivated process is found to be 0.041 eV and 0.078 eV, for the films deposited at substrate temperature from RT to 100 ℃ and 200 ℃ to 400 ℃, respectively. Si-O-C peak is constant but Si-O-Si peak is increased in the FTIR spectra, dipole moment was increased slightly and the dielectric constant of SiOC(-H) film increased from 2.22 to 2.51 and the refractive index is increased from 1.37 to 1.46. But deposition rate was decreased from 71 nm/min to 42 nm/min, the carbon content was decreased from 9.2 % to 5.7 %, and bonding angles to O-Si-C and Si-O-Si, and dipolar polarizability decreases slightly. The constituent chemical bonding configurations of the SiOC(-H) thin films were obtained from the deconvoluted FTIR data. When the substrate temperature increased from the RT to 400 ℃, the Si-O-C(-H) film's ring link mode and Si-O-Si asymmetric stretching mode increased while that of open and cage link modes were decreased. At higher deposition temperature (400 ℃), the Si-CHn groups easily broken due to the higher activation energy and thus SiOx bonds dominate in the SiOC(-H) films. The diploar polarizabilities were calculated for the films deposited at various substrate temperature and it was found to be decreased from F/m2 to F/m2 for the films deposited at RT and 400 ℃, respectively. Thus, the SiOC(-H) films bonding configuration strongly dependent on the substrate temperature and these changes in the film resulted in the enhancement of the dielectric constant and the refractive index as the decrease of nano-pore density and dipolar polarizability. The leakage current density of electric properties is decreased to as the substrate temperature increases from RT to 400 ℃. This value is comparable to the Cu/low-k interconnect applications in integrated circuits technology. The atomic concentrations of each elements (Si, C and O) present in the SiOC(-H) thin films were deduced from the XPS data as 27.7, 26.1 and 46.2 % and 26.8, 23.0, and 50.2 % for the films deposited at RT and 400 ℃, respectively. This result clearly demonstrates that the more number of oxygen atoms replace the carbon atoms in the SiOC(-H) films at the elevated substrate temperature due to weaker Si-CH3 bond broken easily than that of Si-O bonds and released in the form of the C-Ox gas.