Low-k SiCOH Films Deposited with a Single Precursor 1,1,1,3,5,7,7,7 Octamethyl-3,5-Bis(trimethylsiloxy) Tetrasiloxane by Plasma Enhanced Chemical Vapor Deposition.

Abstract

Low-dielectric-constant SiCOH films were deposited by plasma-enhanced chemical vapor deposition using 1,1,1,3,5,7,7,7-octamethyl-3,5-bis(trimethylsiloxy)tetrasiloxane (OMBTSTS) as a single precursor, and the characteristics were investigated. The relative dielectric constant (k) of the SiCOH films declined gradually from 3.57 to 1.90 with decreasing plasma power. The film with the lowest k, deposited at the lowest power of 10 W, showed the lowest leakage current density, with adequate mechanical strength (hardness: 0.98 GPa and elastic modulus: 8.56 GPa) for application in multilevel semiconductor interconnects. The chemistry of the OMBTSTS films was characterized by Fourier transform infrared spectroscopy to study the relation between the chemical and dielectric properties. The dielectric properties, such as the k value and leakage current density, could be explained by a quantitative relation between the Si-O stretching bond and hydrocarbon-related bonds, such as CH₃ and Si-CH₃ bonds, with lower polarizability in the SiCOH film. The refractive index, which is directly linked to the density of the film, was also investigated by ellipsometry. We consider OMBTSTS a promising candidate as a single precursor for fabricating low-k SiCOH films in the plasma-enhanced chemical vapor deposition system.