Optimizing low-k SiCOH films deposited by PECVD with a novel C6H16OSi precursor: Impact of oxygen/carbon ratio on film properties

Abstract

The advancement of ultra-large-scale integration (ULSI) technology has significantly improved semiconductor performance through the miniaturization of chip feature sizes. However, this scaling has led to increased resistance-capacitance (RC) delays in back end of line (BEOL) processes. To mitigate these issues, the semiconductor industry has transitioned from silicon dioxide (SiO₂) to low-k dielectric materials such as organosilicate glass (SiCOH). This study investigates the deposition of SiCOH films using plasma-enhanced chemical vapor deposition (PECVD) with a novel precursor, C₆H₁₆OSi, focusing on the impact of the oxygen/carbon (O/C) ratio on film properties. Fourier-transform infrared (FT-IR) spectroscopy confirms the presence of various hydrocarbon and organosilicon bonds including C–H_x (3100–2800 cm⁻¹), Si–CH₃ (1260 cm⁻¹), and Si(CH₃)_x (775, 805, 845 cm⁻¹) as well as the Si–O–Si asymmetric stretching band at 1250–950 cm⁻¹. Systematic deconvolution of these peaks reveals how increasing O/C shifts the balance between siloxane suboxide, network, and cage structures, alongside changes in Si–(CH₃)_x and C–H_x contributions. X-ray photoelectron spectroscopy (XPS) analysis corroborates these trends, showing that increased O₂ flow enhances the deposition rate and lowers the refractive index. Mechanical tests further indicate that hardness and elastic modulus follow similar tendencies. Computational simulations further demonstrate that higher carbon content leads to the formation of CH₃ bonds, which increase free volume, reduce density, and lower the dielectric constant. These findings highlight the potential of this novel precursor to produce SiCOH films with enhanced electrical, mechanical, and thermal properties for next-generation BEOL applications.