Impact of Hot Carrier Aging on Random Telegraph Noise and Within a Device Fluctuation

For nanometer MOSFETs, charging and discharging a single trap induces random telegraph noise (RTN). When there are more than a few traps, RTN signal becomes complex and appears as within a device fluctuation (WDF). RTN/WDF causes jitters in switch timing and is a major challenge to low power circuits. In addition to RTN/WDF, devices also age. The interaction between RTN/WDF and aging is of importance and not fully understood. Some researchers reported aging increasing RTN/WDF, while others showed RTN/WDF being hardly affected by aging. The objective of this work is to investigate the impact of hot carrier aging (HCA) on the RTN/WDF of nMOSFETs. For devices of average RTN/WDF, it is found that the effect of HCA is generally modest. For devices of abnormally high RTN/WDF, however, for the first time, we report HCA reducing RTN/WDF substantially (>50%). This reduction originates from either a change of current distribution or defect losses

NBTI-Generated Defects in Nanoscaled Devices: Fast Characterization Methodology and Modeling

Negative bias temperature instability (NBTI)-generated defects (GDs) have been widely observed and known to play an important role in device’s lifetime. However, its characterization and modeling in nanoscaled devices is a challenge due to their stochastic nature. The objective of this paper is to develop a fast and accurate technique for characterizing the statistical properties of NBTI aging, which can be completed in one day and thus reduce test time significantly. The fast speed comes from replacing the conventional constant voltage stress by the voltage step stress (VSS), while the accuracy comes from capturing the GDs without recovery. The key advances are twofold: first, we demonstrate that this VSS-GD technique is applicable for nanoscaled devices; second, we verify the 15 accuracy of the statistical model based on the parameters extracted from this technique against independently measured data. The proposed method provides an effective solution for GD evaluation, as required when qualifying a CMOS process

Impact of Hot Carrier Aging on Random Telegraph Noise and Within a Device Fluctuation

For nanometer MOSFETs, charging and discharging a single trap induces random telegraph noise (RTN). When there are more than a few traps, RTN signal becomes complex and appears as within a device fluctuation (WDF). RTN/WDF causes jitters in switch timing and is a major challenge to low power circuits. In addition to RTN/WDF, devices also age. The interaction between RTN/WDF and aging is of importance and not fully understood. Some researchers reported aging increasing RTN/WDF, while others showed RTN/WDF being hardly affected by aging. The objective of this work is to investigate the impact of hot carrier aging (HCA) on the RTN/WDF of nMOSFETs. For devices of average RTN/WDF, it is found that the effect of HCA is generally modest. For devices of abnormally high RTN/WDF, however, for the first time, we report HCA reducing RTN/WDF substantially (>50%). This reduction originates from either a change of current distribution or defect losses

An assessment of RTN-induced threshold voltage jitter

Power consumption is a key issue especially for the edge devices/units in an IoT system. Lowering operation voltage is an effective way to reduce power. As the overdrive voltage, Vg-Vth, becomes smaller, the device is more vulnerable to threshold voltage jitters. One source for the jitter is Random Telegraph Noises (RTN), which cause a fluctuation in both drain current, ΔId, and threshold voltage, ΔVth. Early works on RTN were focused on measuring ΔId and then evaluate ΔVth from ΔId/gm, where gm is transconductance. The accuracy of ΔVth obtained in this way is not known. The objective of this work is to assess its accuracy by comparing it with the ΔVth directly measured from pulse Id-Vg. It will be shown that the correlation between these two is poor, so that ΔVth must not be evaluated from ΔId/gm. This is caused by the device-specific localized current distribution near the threshold

Reliable time exponents for long term prediction of negative bias temperature instability by extrapolation

To predict the negative bias temperature instability (NBTI) towards the end of pMOSFETs’ 10 years lifetime, power-law based extrapolation is the industrial standard method. The prediction accuracy crucially depends on the accuracy of time exponents, n. The n reported by early work spreads in a wide range and varies with measurement conditions, which can lead to unacceptable errors when extrapolated to 10 years. The objective of this work is to find how to make the n extraction independent of measurement conditions. After removing the contribution from as-grown hole traps (AHT), a new method is proposed to capture the generated defects (GD) in their entirety. The n extracted by this method is around 0.2 and insensitive to measurement conditions for the four fabrication processes we tested. The model based on this method is verified by comparing its prediction with measurements. Under AC operation, the model predicts that GD can contribute to ~90% of NBTI at 10 years

INTERACTION BETWEEN RANDOM TELEGRAPH NOISE AND HOT CARRIER AGEING

As downscaling reaches nanometer scale, Hot Carrier Ageing (HCA) and Random Telegraphy Noise (RTN) are two important sources of device instability. Early works typically investigate them separately and treat them as independent phenomena. In reality, however, they occur simultaneously in a device and their interaction is not fully understood. In this work, we study the impact of HCA on RTN amplitude. It is found that for devices of average RTN, HCA only has a limited effect on RTN. For devices of abnormally high RTN, however, HCA can substantially reduce the RTN. The underlying physical mechanism is explored