Physical and electrical properties of low temperature (≪100 °C) SiO₂ films deposited by electron cyclotron resonance plasmas

Silicon dioxide (SiO₂) films have been deposited at temperatures less than 100 °C in an electron cyclotron resonance (ECR) plasma reactor from a gas phase combination of O₂, SiH₄, and He. The ECR configuration provides a highly ionized plasma density with low ion energies that gives efficient dehydrogenation of the growing material while minimizing defect creation. The effects of the O₂/SiH₄ gas flow ratio and He gas flow rate, microwave power and gas pressure on the physical and electrical properties of the film are reported. The physical characterization of the material gives a refractive index of 1.45, an etch rate in buffered HF below 3 nm/s and a hydrogen content of less than 2 at. %. Electrical tests reveal a resistivity in excess of 10¹⁴ Ω cm, an average breakdown strength of 4 MV/cm, fixed charge and interface state densities of 10¹¹ cm^-2 and 10¹² eV^-1 cm^-2, respectively. This has been mainly achieved by using a O₂/SiH₄ gas flow ratio of about 2, while working in the low pressure regime below 5 mTorr and at moderate microwave powers of up to 1000 W. A strong correlation between the physiochemical and electrical properties of the deposited film was observed over the entire range of process parameters. © 2003 American Vacuum Society.