Antenna Rule Checks in Savage

Introduction

Antenna rules is a common name for rules that check ratios of amounts of material in two layers from the same node. They are used to limit the damage of the thin gate oxide during the manufacturing process because of charge accumulation on interconnect layers (metal, polysilicon) on certain fabrication steps.

The name comes from the fact that metal can act as an antenna attracting ions and thus picking up charge during the fabrication process on steps such as plasma etching or ion implantation. This happens when a floating connect layer already connected to gate areas is being fabricated. As a result, the accumulated charge can overstress the thin gate oxide. This leads to the degradation of dielectric breakdown reliability of the device, resulting in degraded performance or even total failure of the device. Antenna effect gets worse in modern technologies, when gate size and thin oxide thickness decrease and at the same time the relative interconnect length increases.