Carbon-doped silicon oxide (CDO) thin films with low dielectric constant (relative dielectric constant&nbsp;k&nbsp;≤ 4.0) have been widely used as inter-metal dielectric materials for advanced interconnect technology in semiconductor industry. In this study, the CDO thin films were deposited on various substrates such as n-type silicon (Si) (100), indium tin oxide coated polyethylene&nbsp;naphthalate (ITO/PEN), and soda lime glass, using the plasma enhanced chemical vapor deposition of tetrakis(trimethylsilyoxy)silane (TTMSS) precursor. The TTMSS precursor was comprised of a Si–O structure and a methyl functional group. Deposition parameters included plasma power, deposition temperature, distance between the substrate and the shower head, working pressure, and flow rate of TTMSS. The external energy source utilized by electrical energy with a radio frequency (RF) of 13.56 MHz was used for plasma generation and plasma powers varied in the range between 20 and 100 W. The deposition temperature was maintained at room temperature. The distance between the substrate and the shower head was 20 mm. A base pressure in a process chamber was obtained as 0.6 Pa and a desired working pressure was 26.7 Pa, obtained by the amount of introduced precursor gas. The flow rate of TTMSS precursor was determined by the control of argon (Ar) carrier gas which transported vaporized precursor from the bubbler to the chamber. The flow rate of Ar gas introduced to the precursor was 18 sccm. The deposition rates of the CDO films were calculated using their thicknesses determined from scanning electron microscopy (SEM) and varied depending on the type of substrates. Chemical structures including chemical bonds and chemical composition of the CDO films were analyzed by using FTIR (Fourier transformation infrared) spectroscopy and XPS (X-ray photoelectron spectroscopy). FTIR absorption peaks enabled the identification of the different bond structures in the films using “the fit multiple peak Gaussian” function. The chemical bonds related with hydrocarbon and Si–O were the main characteristics of the CDO films. The prominent peaks from the FTIR spectra included C–Hx&nbsp;stretching, Si–CH3&nbsp;bending,&nbsp;Si–O–Si stretching, and H–Si–O bending/Si–CH3&nbsp;stretching modes.&nbsp;The Si–O–Si band was attributed to asymmetric stretching modes comprised of cage, network, and silicon suboxide structures. The peak area ratios using C–Hx, Si–CH3, and&nbsp;Si–O–Si were used&nbsp;to qualify the CDO films depending on deposition conditions. XPS spectra composed of the O1s, C1s, and Si2p&nbsp;electron orbitals were used to quantitatively analyze the elemental composition of the CDO films. The growth mechanisms of CDO thin films were dependent on the substrate type. For the ITO/PEN substrate, the lack of Si atoms on the ITO surface made difficulty in forming initial Si-O bonds, resulting in insufficient Si–O–Si structure in the film. In comparison, the CDO films could grow easily on Si or glass substrates due to pre-existing Si–O bonds on their surface. The chemical structures of the CDO films strongly depended on deposition parameters and were expected to affect electrical and mechanical performances of the CDO films.

Chemical Structure Analysis of Carbon-Doped Silicon Oxide Thin Films by Plasma-Enhanced Chemical Vapor Deposition of Tetrakis(Trimethylsilyloxy)Silane Precursor

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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