Ultralow dielectric constant SiCOH films by plasma enhanced chemical vapor deposition of decamethylcyclopentasiloxane and tetrakis(trimethylsilyloxy)silane precursors

Abstract

In semiconductor industry, SiCOH films with low dielectric constant (relative dielectric constant k ≤ 4.0) have been widely used as inter-metal dielectric (IMD) materials in the interconnects of semiconductor chips, to reduce a resistance-capacitance delay. In this study, copolymerized SiCOH films were deposited using the plasma enhanced chemical vapor deposition of decamethylcyclopentasiloxane (DMCPS) and tetrakis(trimethylsilyloxy)silane (TTMSS) precursors. The chemical structure and materials performances of the SiCOH films strongly depended on the flow rate ratios (FRRs) of DMCPS/TTMSS. The chemical bonds and compositions of the SiCOH films were investigated using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The peak area ratios of methyl groups (CH3)x (x=1,2,3) in the spectra varied with the FRRs, affecting the k values and mechanical strengths of the films. The SiCOH films with the FRR of 1.0 showed the elastic modulus of 8.27 GPa and hardness of 0.96 GPa, which are acceptable values for semiconductor devices manufacturing. Ultralow-k values below 2.5 were achieved, along with the leakage current density below 10−6 A•cm−2 at 1 MV•cm−1. The enhanced mechanical and electrical performance with the appropriate FRR of DMCPS/TTMSS suggest the possibility of applying the copolymerized SiCOH films as IMD materials.