High-Field Positive-Charge Generation and its Relation to Breakdown in a-SiO2

This paper reviews and discusses the issues of how electrically active defects are created in thermally grown SiO₂ during high-field stressing of MOS structures and their relation to dielectric breakdown. Positive charge, appearing in various electrical stress experiments, has been observed in early research. It is now clear that depending on the field strength, its duration, and oxide properties that positive charge, negative charge, fast interface states, slow states, amphoteric states, and creation of electron traps may all occur and furthermore they may be interrelated. The term “positive charge”, therefore, is somewhat misleading as it does not convey the whole meaning of the phenomena expected to occur in the oxide under high-field injection. To avoid more confusion, however, I will use it throughout in the loose sense of lumping all the defects together.