Swift heavy ion-induced recrysallization of silicon-on-insulator (SOI) structures

Abstract

Buried Si 3N 4–Si interfaces and overlayer in silicon-on-insulator (SOI) structures were improved by irradiation with 100 MeV 107Ag after the synthesis of buried silicon nitride layers by high dose nitrogen ion-implantation. Auger electron spectroscopy (AES) depth profile analysis illustrates that the MeV heavy ions irradiation in the SOI structure, modifies the distribution of nitrogen that results in better stoichiometry of the buried silicon nitride layers and abrupt Si 3N 4–Si interfaces. Electron spin resonance (ESR) technique shows the improvement in the crystalline structure of the Si over layer. Current–voltage and high frequency capacitance–voltage ( C– V) characteristics were studied, and electrical breakdown measurements were performed on metal nitride silicon (MNS) structures fabricated after removing the Si over layer in the SOI structure. In the ion-beam irradiated SOI specimens, buried silicon nitride layer show a high breakdown field strength of 4.5–6.5 MV/cm as compared to that of 3.0–3.9 MV/cm in the unirradiated one. The C– V analysis of the MNS capacitors reveals that the buried Si 3N 4–Si substrate interface exhibits a better quality with reduced fixed insulator charge and interface state densities after the ion-beam irradiation. Mid-gap interface state density at the buried Si 3N 4–Si substrate interface was as low as 1.0×10 11 cm −2 V −2 after the ion-beam irradiation, which is comparable to that of silicon nitride films deposited on silicon (Si) by the conventional low pressure chemical vapor deposition technique. The role of MeV ion-beam irradiation in improving the properties of SOI structures has been discussed on the basis of various models.