Quantitative TLP Waveform Analysis for GGNmosts

Abstract

A method to extract internal physical quantities from transmission line pulse (TLP) waveforms of grounded gate nMOS electro-static discharge protections is presented. The extraction method is based on two time-constants that appear in the transient voltage waveforms that are part of any TLP result. The first time-constant relates the measured current to the amount of internally stored charge. The second time-constant is related to the life time of internally stored holes via the lateral diffusion of holes that takes place during current ramp-up. From these two extracted time-constants, a complete set of internal quantities including the amount of stored charge, hole lateral diffusion velocity, and the ratio between the internal hole- and electron current, can be calculated from a single TLP pulse. As a result, trends and correlations in the internal quantities can be shown explicitly. This paper shows a strongly increasing hole-to electron current ratio with increasing peak current density during ramp-up. The extraction method is validated using 3D-TCAD and formal mathematical treatment. Developing the theoretical background to this internal parameter extraction method has led to new physical insights. The most prominent of these is a theoretical relation between the peak current density during current ramp-up and the hole life time.