BREAKDOWN MECHANISM IN BURIED SILICON-OXIDE FILMS

Charge injection leading to catastrophic breakdown has been used to st udy the dielectric properties of the buried oxide layer in silicon imp lanted with high-energy oxygen ions. Current versus gate bias, current versus time, and capacitance versus gate bias were used to characteri ze, at various temperatures, MOS metal-oxide-semiconductor capacitors with areas in the 1 X 10(-4)-1 X 10(-2) cm2 range fabricated with comm ercially available single- or triple-implant separation by implanted o xygen silicon wafers. The data show that injected charge accumulates i n the buried oxide at donorlike oxide traps ultimately leading to cata strophic breakdown. Both Poole-Frenkel and Fowler-Nordheim conduction, as well as impact-ionization mechanisms, have been identified in the oxide. The charge and field to breakdown in the best buried oxides are , respectively, near 1 C cm-2 and 10 MV cm-1, similar to the thermally grown oxide parameters. Cumulative distributions of these parameters measured over a large number of capacitors show that the frequency of breakdown events caused by extrinsic defects is scaled with the capaci tor area. Intrinsic and extrinsic defect distributions are broader tha n with thermally grown oxides.