Impact of copper and aluminum power metallization on the negative bias temperature instability

Abstract

Investigations on degradation mechanisms have great importance regarding device reliability. Deeper understanding of the NBTI is one of the crucial issues for MOSFET manufacturing. This also includes studying possible consequences of individual steps during fabrication on the device performance. The present work shows that a back end of line process like metallization can have a strong impact on oxide reliability. Investigations on devices with copper and aluminum power metallization are performed and compared. Results indicate different properties at the oxide - semiconductor interface, which cause different levels of degradation through NBTI after application of a certain stress. Devices with aluminum metallization are affected by more severe degradation than devices with copper, especially concerning defects with long emission time constants.