Electrical Properties of Ultrathin SiO₂ Layer Deposited at 50 ∘C by Inductively Coupled Plasma-Enahnced Chemical Vapor Deposition

We found a strong correlation between the layer porosity and electrical properties of a SiO 2 layer deposited by inductively coupled plasma chemical vapor deposition. At 50 °C the SiO 2 layers have a double structure: a dense layer in contact with the substrate and a porous layer on top of it. The critical thickness at which voids appear depends on the deposition rate. Breakdown voltage and charge trapping performances of SiO 2 layers are very good if the thickness is below the critical value and deteriorate significantly in thicker, porous, layers. Layer porosity is absent when the sample is deposited at 250 °C.