Mecanismos de conducción a través del aislante de puerta en estructuras MOS (Metal-Oxido-Semiconductor)

Abstract

We have analyzed the different conduction modes through the gate insulator that canbe observed in Metal-0xide-Semiconductor (MOS) structures. Special emphasis is put onsilicon dioxide (SiO2)due to its implications for microelectronic technologies. Depending onthe voltage range and oxide thicknesses considered, SiO2 exhibits different behaviors thatrequire a particular study. When the oxide is very thin (<5-6nm), the tunneling current at large bias showsoscillations that can be interpreted, in terms of quantum mechanics, as a consequence of thewave function’s reflection at the oxide interfaces. We have proposed a semi-empirical modelthat captures the shape of the conduction characteristics in the whole bias range and for allthicknesses in which the phenomenon is observable. When an electrical stress is applied, the tunneling current at low voltages exhibits ananomalous increase that can be attributed to the appearance of bulk traps at the insulator. Thisconduction mechanism is referred to as SILC (stress-induced leakage current). For a thickeroxide (>10nm), it is also possible to detect a change in the oxide state of charge by means ofshifts of the capacity-voltage or current-voltage curves. We proposed a simple modificationto the well-known Fowler-Nordheim tunneling expression, which allows to explain suchbehavior. Finally, we present an improved model for conduction to deal with the breakdownmodes of ultra-thin oxides SOFT and HARD. The model is based on the physics ofmesoscopic conducting systems and the transmission properties of the so-called quantumpoint contacts. Until now, this is the only analytical model available that can successfullyexplain a number of experimental facts related to the phenomenon under study.

Date of Award	23 Aug 2002
Original language	Spanish
Awarding Institution	Facultad de Ingeniería, Universidad de Buenos Aires (FIUBA)
Supervisor	Adrian N. Faigon (Director)