An All-In-One Silicon Odometer for Separately Monitoring HCI, BTI, and TDDB

We present an on-chip reliability monitor capable of separating the aging effects of hot carrier injection (HCI), bias temperature instability (BTI), and time-dependent dielectric breakdown (TDDB) with high frequency resolution. This task is accomplished with a pair of modified ring oscillators (ROSCs) which are representative of standard CMOS circuits. We use a ¿backdrive¿ concept, in which one ROSC drives the voltage transitions in both structures during stress, such that the driving oscillator ages due to both BTI and HCI, while the other suffers from only BTI. In addition, long term or high voltage experiments facilitate TDDB measurements in both oscillators. Sub-¿s measurements are controlled by on-chip logic in order to avoid excessive unwanted BTI recovery during stress interruptions. Sub-ps frequency resolution is achieved during these short measurements using a beat frequency detection system, and we automate the experiments through a simple digital interface. Measurement results are presented from a 65 nm test chip over a range of stress conditions.