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

We found a strong correlation between the layer porosity and electrical properties of a SiO2 layer deposited by inductively coupled plasma chemical vapor deposition. At 50 °C the SiO2 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 SiO2 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.