UV irradiation effects on the bonding structure and electrical properties of ultra low-k SiOC(–H) thin films for 45 nm technology node

Low-dielectric-constant SiOC(–H) thin films were deposited on p-type Si(100) substrates using plasma enhanced chemical vapor deposition (PECVD) from vinyltrimethylsilane (VTMS; CH2 = CHSi(CH3)3) and oxygen gas as precursors. To improve the structural, mechanical and electrical characteristics, SiOC(–H) films deposited using PECVD were post-treated by ultraviolet (UV) irradiation for various time intervals. Carbon content of the SiOC(–H) films increased before 240 s of UV irradiation time. But carbon-bonded functional groups of the SiOC(–H) film, in case of 480 s UV irradiation time, is replaced with Si–O bond. Because the Si–CHn bond groups are broken due to UV irradiation, Therefore, the films are formed with Si–O bond rich in the Si–O–C(–H) structure. The lowest relative dielectric constant, leakage current density, the elastic modulus and the hardness of SiOC(–H) with 240 s of UV irradiation time were about 2.07, 2.1 × 10−7A/cm2, 43 GPa, and 3.68 GPa, respectively. The results indicate that the SiOC(–H) films exposed by UV irradiation improve the structural, mechanical, and electrical characteristics.