Analysis of recoverable and permanent components of threshold voltage shift in NBT stressed p-channel power VDMOSFET

Abstract

In this study we investigate the dynamic recovery effects in IRF9520 commercial p-channel power vertical double diffused metal–oxide semiconductor field-effect transistors (VDMOSFETs) subjected to negative bias temperature (NBT) stressing under the particular pulsed bias. Particular values of the pulsed stress voltage frequency and duty cycle are chosen in order to analyze the recoverable and permanent components of stress-induced threshold voltage shift in detail. The results are discussed in terms of the mechanisms responsible for buildup of oxide charge and interface traps. The partial recovery during the low level of pulsed gate voltage is ascribed to the removal of recoverable component of degradation, i.e., to passivation/neutralization of shallow oxide traps that are not transformed into the deeper traps (permanent component). Considering the value of characteristic time constant associated with complete removal of the recoverable component of degradation, it is shown that by selecting an appropriate combination of the frequency and duty cycle, the threshold voltage shifts induced under the pulsed negative bias temperature stress conditions can be significantly reduced, which may be utilized for improving the device lifetime in real application circuits.

NBT stress and radiation related degradation and underlying mechanisms in power VDMOSFETs

“…NBT stress-induced threshold voltage instabilities in commercial power VDMOSFETs, as well as the implications of related degradation on device lifetime have been extensively investigated in our research in the last decade [27,[42][43][44]. Although in many experiments devices have been subjected to various NBT stress (static or pulsed) and annealing conditions [9,23,25,45,46,[48][49][50][51][52], in this section a part of results obtained during static NBT stress and annealing is presented, with attention to insight into the NBTI as a result of sequential NBT stress and bias annealing steps.…”

Effects of consecutive irradiation and bias temperature stress in p-channel power vertical double-diffused metal oxide semiconductor transistors

“…It should be emphasized that the presented results obtained during NBT stressing of power VDMOSFETs represent mostly permanent (non recoverable) component and perhaps only the slowest part of the recoverable component of NBT stress induced degradation. 6,36) Namely, due to delay time for measurement we generally refrain ourselves from discussing the quickly recoverable component of degradation and only consider cummulative data, mostly related to the permanent component and slow component of degradation that does not recover so quickly.…”

“…8(c)-11(c)] might be in conjunction with diffusion of hydrogen molecules from the areas of high concentrations in oxide toward lower concentrations near the interface. The hydrogen molecules can be cracked not only at charged O 3 ¸Si + oxide traps by the reverse reaction (6), but also at O 3 ¸Si + • Si¸O 3 by the reaction:…”

“…Hence, these defects have been in the focus of investigation more than 40 years. [3][4][5][6][7][8][9][10][11][12][13][14] Numerous methods used in the study of SiO 2 and SiO 2 -Si interface nature and their characterization can be roughly divided into two categories: the methods implemented on the MOS capacitor structure and the methods implemented on the complex MOS electron devices. These methods are mostly based on electrical techniques and they generally yield the results related to the energy distribution of defects in the oxide and at the interface, thus allowing the prediction of the defect nature and modelling of their behavior.…”