Showing papers on "Snapback published in 1982"

Analysis of Breakdown Phenomena in MOSFET's

Abstract: An accurate two-dimensional self-consistent numerical model for MOS transistors which is able to predict avalanche behavior is presented. This model aims at a more principal understanding of the physical processes which arise from the avalanche effect and which eventually lead to breakdown. The system of the fundamental semiconductor equations with several generation/recombination mechanisms is solved. To improve the description of the ionization process, correction terms are introduced which account for the fact that the gate induced field does not cause ionization. Holes which are generated in the pinch-off region by impact ionization cause a bulk current; the voltage drop at the parasitic bulk resistance initiates an internal feedback mechanism. Thus a negative resistance branch of the drain current characteristic can arise. However, at high current levels, introduced by a high gate bias and/or a short channel, this snap-back effect is often counterbalanced by strong recombination. Snapback voltage can be estimated with this model.

Characteristics of short-channel MOSFETs in the breakdown regime

Abstract: When a short-channel MOSFET is driven into the avalanche-induced breakdown region, the drain current increases rapidly and shows a snapback characteristic. Both the substrate current and the current collected by a nearby reverse-biased pn junction also increase with increasing drain current in this region of operation. All of these effects are associated with minority-carrier injection from the source junction into the substrate. A model for the drain I-V characteristics in the snapback region is proposed. Also presented is a related model incorporating conductivity modulation that predicts linear relationships between the substrate and the remote-junction collection currents and the drain current in this region of operation. Experimental results agree well with the models.

A Snapback Evaluation Technique for Synthetic Lines

Abstract: : A technique is proposed for quantifying the amount of energy released when synthetic lines fail and recoil, called snapback. Ten synthetic line material/construction combinations are investigated by bending the line around a 1 in. diameter pin fixture and loading until failure occurs at the pin. High-speed photography is used to calculate the velocity of the line at failure and the attending kinetic energy. Three parameters are proposed to quantify snapback; (a) the Storage Energy Potential is a measure of how much energy a line stores as load is applied to it, (b) Snapback Energy Potential is a measure of the kinetic energy that the line possesses after failure occurs and the line recoils, and (c) the Energy Release Ratio indicates the proportion of stored energy that becomes kinetic energy after the line parts. In addition to discussing the evaluation technique, the various lines tested are compared to determine if some materials or constructions have a lower potential to snapback. The failure mechanism (i.e., the sequence of yarn failures that culminate in complete failure) of each line construction is observed using high-speed photography to determine if lines with a cascading failure mechanism (i.e., failure over a relatively long period of time) have lower snapback potential. The path that a line follows during snapback is also observed. Lines snap back directly toward the fixed end if the failure occurs in clear line. If a line retracts around the curved surface as a bollard, significant lateral velocity is imparted to the line and it sweeps a wide area.