AVS 57th International Symposium & Exhibition
    Plasma Science and Technology Tuesday Sessions
       Session PS1-TuA

Paper PS1-TuA2
Mechanism of Modification in Si-O-Si Structure in Porous SiOCH Low-k Films by H2/N2 Plasmas

Tuesday, October 19, 2010, 2:20 pm, Room Aztec

Session: Advanced BEOL/Interconnect Etching II
Presenter: H. Yamamoto, Nagoya University, Japan
Authors: H. Yamamoto, Nagoya University, Japan
K. Takeda, Nagoya University, Japan
K. Ishikawa, Nagoya University, Japan
H. Kondo, Nagoya University, Japan
M. Sekine, Nagoya University, Japan
M. Hori, Nagoya University, Japan
T. Imamura, Toshiba Corporation, Japan
H. Hayashi, Toshiba Corporation, Japan
I. Sakai, Toshiba Corporation, Japan
T. Ohiwa, Toshiba Corporation, Japan
Correspondent: Click to Email
Introduction of porous low-dielectric-constant (low-k) materials such as porous (p-) SiOCH film, to the interlayer dielectric is important for improving performances of ULSI devices. The trench sidewall in the p-SiOCH film is known to suffer serious damage during the plasma processes. The in-situ evaluation is crucial for the clarification of damage generation mechanism because the damaged films are easily modified during air exposure. In this work, we have investigated the impact of ions, radicals and light from H2/N2 plasma and subsequent air exposure on Si-O-Si bond structure in the film using in-situ Fourier transform infrared reflection absorption spectroscopy. A 75-nm-thick p-SiOCH film was coated on 150-nm-thick Tungsten film deposited on Si substrate. A Si plate or an MgF2 window which transmits light (greater than 115 nm in wavelength) was set 1 mm above or just on the film during the plasma exposure. Samples were placed on the lower electrode in a VHF-CCP etcher with (a) no plate for evaluating the interaction of ions, radicals, and light, (b) Si plate for evaluating the impact of radicals, (c) MgF2 window for evaluating the effect of light and radicals, and (d) MgF2 window with no space for evaluating the light effect. To investigate the Si-O-Si bond modification in the films, IR absorption signal in 985-1250 cm-1 were decomposed to three bands with peaks at 1035, 1065, and 1149 cm-1, which correspond to the linear, network and cage structures, respectively. The change in the three peak area ratios were investigated after H2/N2 plasma and air exposures. The peak area ratio of the linear structure decreased and the ratio of network and cage structure increased after the H2/N2 plasma exposure in all samples. The ratio of linear structure decreased and the ratio of cage structure increased after the air exposure in all samples. In the case of sample (a), that was exposed to ions, radicals, and radiation, the amount of change in Si-O-Si structure was relatively smaller than the amount of decrease in Si-CH3 bond. It was confirmed that a portion of Si-O-Si linear structure in the SiOCH film changed to network and cage structure with decrease in Si-CH3 bond during the H2/N2 plasma exposure. Si-NH2 bonds and dangling bonds formed by the plasma exposure reacted with water in the atmosphere and the Si-O-Si structure was modified with Si-OH bonds formation. Ion bombardment made the top surface shrink and the densified layer inhibited moisture uptake into the film during air exposure. This work was supported by Grant-in-Aid for Scientific Research (21・10187).