Back stress model on electromigration lifetime prediction in short length copper interconnects

Abstract

The short length on the electromigration lifetime is a useful effect to increase current limits in advanced circuits. A way to increase current limit is to consider the Blech effect. The electromigration threshold due to belch effect in copper interconnect for 65nm and 45nm technology is reported in this study. The critical product (jL) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> was determined by varying the metal length and stress current density. The higher (jL) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> value is obtained for lower stress current, shorter metal lead and 65nm technology with higher hardness ILD. Finally, this critical product (jL) <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> as the accelerated EM length factor was used to predict the lifetime. It is shown that the lifetimes of short leads with less than 5 μm have at least 9.52 and 1.45 times higher than that of 250 μm metal lead for 65nm and 45nm technology, respectively.