Performance Degradation Analysis and Hot-Carrier Injection Impact on the Lifetime Prediction of Voltage Control Oscillator

This paper analyzes the root cause of performance degradation and the impact of hot-carrier injection (HCI) on the lifetime prediction of an LC voltage-controlled oscillator (LC-VCO). Observed from both constant voltage stress and ramped voltage stress tests, it is shown that the dominant degradation mechanism shifts from a negative bias temperature instability to an HCI due to the accelerated aging condition. Furthermore, simulations show that a frequency increase of degraded VCO is mainly attributed to the degradation in the pMOSFET of a cross-couple pair, while the degradations in the pMOSFET and nMOSFET have relatively the same impact on the startup voltage shift. Compared with the frequency change, the degradation of the startup voltage of an LC-VCO is less sensitive to device width. Based on the observed results, methodologies to optimize the reliability tests and mitigate the frequency shift of LC-VCO are proposed.