Methyl siloxane spin-on-glass (SOG) is a conventional gap-filling material. In accordance with the requirement of low permittivity, many of major SOG suppliers are developing new types of methyl siloxane SOGs.
The most interesting property of these SOGs is their permittivity, which we measured by making stack structures of Al-0.5%Cu / TEOS CVD SiO2 / SOG / n+ Si. We also studied I-V characteristics, refractive indices, FT-IR spectra, stress, and moisture resistance.
All of the SOGs showed small stress and fair moisture resistance. Leakage currents were less than 2.5E-10 A/cm2 for bias voltages up to 5V. Permittivities ranged from 2.9 to 3.6. We observed a correlation between permittivity and FT-IR spectral features associated with Si-O-Si bonds. Reducing the number density of Si-O-Si bonds may be an effective way to lower the permittivity of this class of SOGs