MOS interface states: overview and physicochemical perspective

The metal-oxide-semiconductor transistor has become the dominant device for very large-scale integrated circuits. The performance and reliability of an MOS device are heavily influenced by the quality and properties of the interface between the oxide and the Si region directly beneath. Inherent, process-related, and operationally and environmentally generated interface states or traps are exceedingly harmful or disabling when present. Although controlled successfully by semiempirical design, fabrication and operational regimens, ever-smaller device size-approaching the scale in which a single trap can be important-makes further extension of knowledge on the basic physical and chemical aspects of interface states essential for confident technological progress. In addition, Si/SiO₂ interface states continue to merit research in their own right. This paper briefly highlights selected topics from past and present interface-state research and describes some essential physical and chemical properties.