Study on In-situ O2 Plasma Treatment at RPCVD of SiOC Thin Film using Styrene-Contained Precursor

Abstract

Study on In-situ O2 Plasma Treatment at RPCVD of SiOC Thin Film using Styrene-contained Precursor Eung-ju Kim Dept. of Nanoscale Semiconductor Engineering The Graduate School Hanyang University With the rapid miniaturization of semiconductor transistor devices, the issue of RC delay caused by parasitic capacitance has gained significant prominence. Consequently, there’s a growing demand for materials with low dielectric constants (low-k). Among the array of potential low-k materials, SiOC stands out. It possesses distinctive characteristics, such as generating less polarization due to the difference in electronegativity between the Si-C bond and the Si-O bond, which makes is k value lower than SiO2, the original applied low-k material. Additionally, it offers the potential to lower the k value through pore formation facilitated by the Si-CH3 terminated bond. However, it’s essential to note that excessive pore formation might compromise the mechanical and etching properties of the low-k thin film. Therefore, conducting further studies in this area is imperative, trying various precursors and processes. In this paper, study on depositing SiOC thin film was conducted using remote plasma chemical vapor deposition process that introduced in-situ plasma treatment. (Dimethyldimethoxysilane)2styrene ((MDMS)2Styrene) and CH4 plasma were used as the reactant, repectively, the process temperature was 550˚C, and oxygen was used for in-situ plasma treatment. The growth rate was same for both with and without the in-situ plasma treatment, indicating that the in-situ plasma treatment did not significantly affect the thin film growth itself. Auger electron spectroscopy results showed that the carbon content can be controlled in wide range according to the number of in-situ oxygen plasma treatments. X-ray photoelectron spectroscopy results confirmed that Si-C4 bonds can be newly formed, which does not exist in the original (MDMS)2Styrene bond structure. It was also confirmed that the Si-C bonds can be preserved while the ratio of Si-O bonds increased as the number of in-situ oxygen plasma treatments increased. As the in-situ plasma treatment proceeded, thin film density increased from 2.24 to 2.40g/cm3, and the refractive index increased from 1.33 to 1.49. Through this, it was possible to control the pores in the low- k thin film. At the same time, the dielectric constant increased as carbon content decreases, but it could be maintained below 3.9 due to the presence of Si-C bonds. Finally, it was shown that the leakage current could be improved down to 9.51×10-9A/cm2 at 1MV/cm, the breakdown voltage up to 9.4MV/cm, and the wet etch rate could be lowered from 78 to 19Å /min. Based on these results, we demonstrated the feasibility of simultaneously controlling carbon content while enhancing both electrical and etching properties, utilizing an in-situ O2 plasma treatment process and (MDMS)2Styrene in RPCVD process of SiOC.