An investigation of instability and charge motion in metal-silicon oxide-silicon structures

The results of a detailed study of the charge motion and instability in thermally grown, undoped silicon dioxide films at high electric fields and elevated temperatures are presented. The transient behavior of the charge motion in the oxide is analyzed and a model proposed to explain the observations. It is shown that the instability consists of the motion of positively charged ions and that interface trapping effects play a significant role in determining the transient behavior. Detailed consideration is given to the nature of these trapping effects, and it is concluded that caution must be exercised in ascribing the activation energy measured for the instability to that for the true mobility of these ions in a "bulk" oxide. The effects of various ambient treatments on the instability are discussed, and conclusions are drawn concerning the physical and chemical nature of the observed instability.