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. 2024 Dec 28;16(1):27.
doi: 10.3390/mi16010027.

Recovery Analysis of Sequentially Irradiated and NBT-Stressed VDMOS Transistors

Snežana Djorić-Veljković  1 , Emilija Živanović  2 , Vojkan Davidović  2 , Sandra Veljković  2 , Nikola Mitrović  2 , Goran Ristić  2 , Albena Paskaleva  3 , Dencho Spassov  3 , Danijel Danković  2
Affiliations

Recovery Analysis of Sequentially Irradiated and NBT-Stressed VDMOS Transistors

Snežana Djorić-Veljković et al. Micromachines (Basel). .

Abstract

This study investigates the effects of negative bias temperature (NBT) stress and irradiation on the threshold voltage (VT) of p-channel VDMOS transistors, focusing on degradation, recovery after each type of stress, and operational behavior under varying conditions. Shifts in VT (ΔVT) were analyzed under different stress orders, showing distinct influence mechanisms, including defects creation and their removal and electrochemical reactions. Recovery data after each type of stress indicated ongoing electrochemical processes, influencing subsequent stress responses. Although the ΔVT is not particularly pronounced during the recovery after irradiation, changes in subthreshold characteristics indicate the changes in defect densities that affect the behavior of the components during further application. Additionally, the findings show that the ΔVT during the NBT stress after irradiation (up to certain doses and conditions) remains relatively stable, but this is the result of a balance of competing mechanisms. A subthreshold characteristic analysis provided a further insight into the degradation dynamics. A particular attention was paid to analyzing ΔVT with a focus on predicting the lifetime. In practical applications, especially under pulsed operation, prior stresses altered the device's thermal and electrical performance. It was shown that self-heating effects were more pronounced in pre-stressed components, increasing the power dissipation and thermal instability. These insights additionally highlight the importance of understanding stress-induced degradation and recovery mechanisms for optimizing VDMOS transistor reliability in advanced electronic systems.

Keywords: NBTI stress; VDMOS; irradiation; recovery; reliability; self-heating.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Subthreshold (a) and above-threshold (b) transfer characteristics of n-channel power VDMOSFETs (of two different manufacturers—M1 and M2) during long-term recovery after applied irradiation.
Figure 2
Figure 2
Schematic representation of the steps involved in both parts of the experiment, during which the components were subjected to (a) NBT stress followed by irradiation and (b) irradiation followed by NBT stress.
Figure 3
Figure 3
Components’ transfer characteristic shifts induced by NBT stress followed by irradiation with a gate voltage of −10 V (a) up to 30 Gy and (b) up to 120 Gy, and transfer characteristics after the spontaneous recovery that tailed both stresses.
Figure 4
Figure 4
Components’ transfer characteristic shifts induced by irradiation with a gate voltage of −10 V (a) up to 30 Gy and (b) up to 120 Gy, followed by NBT stress, and transfer characteristics after the spontaneous recovery that tailed both stresses.
Figure 5
Figure 5
Threshold voltage shift through NBT stress followed by irradiation and during the spontaneous recovery that tailed both phases.
Figure 6
Figure 6
Threshold voltage shift through irradiation followed by NBT stress and during the spontaneous recovery that tailed both phases.
Figure 7
Figure 7
Threshold voltage shift through irradiation and the spontaneous recovery of fresh and previously NBT-stressed components.
Figure 8
Figure 8
Threshold voltage shift through NBT stress and the spontaneous recovery of fresh and previously irradiated components.
Figure 9
Figure 9
Schematic illustration of two parts—contributions to the increase and decrease in threshold voltage shift, which are caused by the mechanisms of activation of electrochemical reactions and annealing.
Figure 10
Figure 10
Changes in threshold voltage shift through NBT stress, after irradiation with no gate voltage applied up to four achieved doses (a) and lifetime prediction (b).
Figure 11
Figure 11
The temperature change of two stressed groups of components, NBT-RAD and RAD-NBT, with four different drain currents.
See this image and copyright information in PMC

References

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