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Abstract

A protection structure for integrated circuits with an n-channel MOS field-effect transistor has a more stable bipolar state, with the change to the bipolar state occurring fast. Below the drain region and the drain contact region an n-type resistor region doped more lightly than the drain region and the drain contact region is formed to provide the electrically conductive connection between the drain region and the drain contact region. When a positive voltage pulse is applied to the drain contact region, the n-channel MOS transistor will go into a bipolar operating state upon reaching the drain-source or drain-substrate breakdown voltage. The conductor paths are typically connected to ground. The n-well forms a series resistor between the drain region and the drain contact region of the respective transistor. It also forms a pn junction between the drain region and the channel, the collector pn junction, which extends deep into the substrate. Because of the series resistance of this n-well, during the change to the bipolar state, contractions of the current occurring at the pn junction are prevented. In the bipolar state, the transistor can absorb more power than with conventional arrangements. By connecting two or more transistors in parallel, the current is distributed even further, so that the power can be absorbed by both transistors, since the dissipation is distributed over an even larger area.

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