Characterization of low dielectric constant plasma polymer films deposited by plasma-enhanced chemical vapor deposition using decamethyl-cyclopentasiloxane and cyclohexane as the precursors

We investigated the properties of plasma polymer films deposited by plasma-enhanced chemical vapor deposition using a mixture of decamethyl-cyclopentasiloxane $(C10H30O5Si5)$ and cyclohexane $(C6H12)$ as the precursors, which we refer to as plasma polymerized decamethyl-cyclopentasiloxane: cyclohexane (PPDMCPSO:CHex) films. The relative dielectric constants, $k$⁠, of the plasma polymer films were correlated with the Fourier transform infrared absorption peaks of the C–Hx, $Si–CH3$⁠, and Si–O related groups. As the amount of the $CHx$ species in the as-deposited plasma polymer films increased, the $k$ value and the leakage current density of the thin films decreased. The subsequent annealing of the PPDMCPSO:CHex film at $400°C$ for $1h$ further reduced the $k$ value to as low as $k=2.05$⁠. This annealed PPDMCPSO:CHex thin film showed a leakage current density of the order of $4×10−7A∕cm2$ at $1MV∕cm$ and a breakdown field of $6.5MV∕cm$⁠. Through the bias-temperature stress test, it was estimated that the PPDMCPSO:CHex film with a $k$ value of 2.05 would retain its insulating properties for ten years at $167°C$ under an electrical field of $1MV∕cm$⁠, when it is presented as a layer adjacent to $Cu∕TaN(10nm)$⁠.