A void-free SiO2 interlayer dielectric film formation technology has been developed. This technology utilizes tetraethylorthosilicate [TEOS, Si(OC2H5)4]/ozone (O3) atmospheric pressure chemical vapor deposition (APCVD) SiO2 film gap-filling, and the TEOS-based dual frequency plasma enhanced vapor deposition (PECVD) SiO2 film as an underlayer of TEOS/O3 APCVD SiO2 film. This technology enables the formation of void-free SiO2 interlayer dielectric films without any pretreatment for the underlayer between aluminum wirings line and space of 600 and 600 nm, respectively. Single-frequency PECVD SiO2 films are also applied as an underlayer of TEOS/O3 APCVD SiO2 gap-filling. However, void-free gap-filling cannot be achieved, even using the single frequency PECVD SiO2 underlayer. To clarify the mechanism of the void-free gap-filling, the underlayer PECVD SiO2 film properties are investigated. The SiO2 film density at the Al wiring pattern's sidewall of the dual-frequency PECVD SiO2 films is equal to that at the pattern's bottom, while the density at the pattern's sidewall formed using single-frequency PECVD SiO2 films is lower than that at the pattern's bottom. The carbon concentration for the dual-frequency PECVD SiO2 films is lower than that for the single-frequency PECVD SiO2 films. The H2O and acetaldehyde (CH3CHO) detected from the dual-frequency PECVD SiO2 films due to the oxidation of the ethoxy group, is much more than that from the single-frequency PECVD SiO2 films. Based on the experimental results, the mechanism of void-free gap-filling of TEOS/O3 APCVD SiO2 films is considered to consist of three steps; (i) involving R ions (R, alkyl group) into the PECVD SiO2 films during film deposition, (ii) Si-OR bonds formation at the PECVD SiO2 films' surface, and (iii) oligomers flow at TEOS/O3 APCVD SiO2 film deposition. It is considered that the oligomers flow is promoted by the Si-OR bonds, resulting in the void-free gap-filling. The dual-frequency PECVD SiO2 films can improve the gap-filling of TEOS/O3 APCVD SiO2 films.
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