Assessment of reliability impact on GHz processors with moderate overdrive

Moderate overdrive of the supply voltage rather reduces total powers at high temperatures, which enables GHz design overcoming thermal runaway. We have examined the way in which reliability issues such as negative bias temperature instability (NBTI) and hot carrier injection (HCI) affect the product performance. 1) The high temperature and voltage acceleration test on 45nm products has revealed that NBTI variations have small impacts on the amount of the voltage guard-band which is set at the product testing to prevent the wear-out failures in advance. 2) The increase in the voltage guard-band by using moderate overdrive is small enough compared to the amount of moderate overdrive voltage. 3) The HCI AC-to-DC ratio is expected to increase as the process scaling proceeds, making the HCI less influential. These aspects enable low-power and reliable GHz design utilizing moderate overdrive.