Intrinsic Thermomechanical Properties of Freestanding TEOS-SiO2 Thin Films Depending on Thickness

Abstract

This study focuses on characterizing the intrinsic tensile and thermal expansion properties of silicon dioxide (SiO₂) thin films deposited through plasma-enhanced chemical vapor deposition (PECVD) using tetraethoxysilane (TEOS) as a precursor. PECVD TEOS-SiO₂ thin films have garnered significant attention as interlayer dielectric materials due to their exceptional step coverage, chemical stability, and low-temperature deposition process. However, the intrinsic mechanical properties of TEOS-SiO₂ thin films, including elongation at break, tensile strength, and coefficient of thermal expansion (CTE), have not been widely reported due to the challenges posed by the presence of the substrate. In this study, the TEOS-SiO₂ thin film was delaminated from the substrate by selectively etching the naturally formed copper oxide layer between the copper and TEOS-SiO₂ layers. Uniaxial tensile test and CTE measurement were performed using a liquid-assisted freestanding TEOS-SiO₂ film. Remarkably, upon increasing the thickness of the TEOS-SiO₂ film from 200 to 320 nm, significant changes were observed in tensile and thermal expansion properties. As the thickness of the TEOS-SiO₂ film increases, the modulus and elongation increase and the CTE decreases.