Apparatus for current ballasting esd sensitive devices

Abstract

A current ballasting circuit for an ESD protection device couples nonintersecting conductive strips between a common contact pad and the contact electrodes of the ESD protection device. The connecting strips form respective electrically isolated ballasting resistors between the external contact pad and the contact electrodes of the ESD device. In addition, lateral resistances are formed between the contact strips which enhance the operation of the multiple ballasting resistors. The conductive strips may be made from metal, polysilicon or by a vertically meandering series connection of polysilicon layers, metal layers and interconnecting vias. The lateral resistance between the parallel conductive paths may be enhanced by segmenting both the drain and source electrodes. In one example, the gate electrode of an MOS ESD device extends locally between each pair of strips to segment the drain and source regions. The lateral resistance between the conductive strips is further enhanced by defining an additional gate electrode, having a portion that is parallel to the gate electrode of the ESD device and further portions that extend between the conductive strips. Multiple ESD devices may be connected in parallel to provide additional paths for shunting ESD current.