Ion-induced electrical breakdown in metal-insulator-silicon capacitors

Abstract

Metal-insulator-silicon self-healing capacitors were constructed with thin insulators of either thermal oxide, plasma-enhanced chemical vapor deposition (PECVD) oxide, low-pressure chemical vapor deposition (LPCVD) nitride, PECVD nitride, bilayers of oxide-nitride, or PECVD oxynitrides. Studies were made of the dependence of the ion-induced electrical field breakdown (RIB) on substrate temperature, ion mass, ion energy, and film thickness. For all of the dielectrics, the ion-induced threshold electric field, ET, at breakdown is dependent only upon the coulombic energy loss due to the incident ion for films greater than 70-nm thickness. For decreasing film thickness, both the intrinsic breakdown field and the RIB ET show increasing electric field values. The RIB ET is inversely proportional to the square root of the charge density created by the incident ion. A phenomenological model which agrees with experimental results is developed to explain the observations. The model indicates that the ion-induced breakdown occurs within the bulk of the thin film and is not sensitive to the interface or to the type of conduction mechanism preceding the ion-induced breakdown. With the use of nitride films or oxynitride films, the specific ionization limit is lowered to less than 6 MeV cm2/mg, compared to the previous limit of 14 MeV cm2/mg for oxide films.