A comparative study of the electron trapping and thermal detrapping in SiO2 prepared by plasma and thermal oxidation

Abstract

Preparation of silicon dioxide (SiO2) thin films by plasma anodization is a promising low temperature (≤600 °C) silicon oxidation technique. This paper investigates the electron trapping and thermal detrapping properties of the plasma grown oxide and compares them with those of the conventional thermal oxide. The avalanche electron injection measurement shows that the electron trapping in the plasma oxide is more severe. The two electron capture cross sections detected in the plasma oxide are of the order of 10−15 and 10−17 cm2, respectively. The former is absent in the thermal oxide and is a feature of oxides prepared at low temperature. The latter is also found in thermal oxide, but its chemical nature is different. Both of them are located near SiO2/silicon interface, indicating that they are related to the intermediate layer. The electron detrapping process in the plasma oxide is different from that in the thermal oxide and has a linear dependence on the logarithmic time. The detrapping is thermally activated with an activation energy of 0.63–0.75 eV. The above traps in plasma oxide can be removed by a high temperature (e.g., 960 °C) post-oxidation annealing (POA) in an inert ambient. After such a POA, the electron trapping in plasma oxide is similar to that in thermal oxides. Some speculation on the trap formation processes is included.