High Quality Growth of SiO₂ at 80° C by Electron Cyclotron Resonance (ECR) for Thin Film Transistors

Abstract

Silicon dioxide (SiO₂) films have been deposited at 80°C in an Electron Cyclotron Resonance (ECR) plasma reactor from a gas phase combination of He, O₂ and SiH₄. The ECR configuration provides a highly ionised plasma (∼10¹⁶ m⁻³) with low ion energies (∼10eV) that gives efficient dehydrogenation of the growing material whilst minimizing defect creation. The physical characterisation of the material gives a refractive index of 1.46, 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 10¹⁴Ωcm, an average breakdown strength of 5 MV/cm, and fixed charge and interface state densities of 10¹¹ cm⁻² and 10¹² eV⁻¹cm⁻² respectively. This has been achieved using a O₂:SiH₄ flow ratio ≍ 2:1.