A B S T R A C TThis article treats the recovery of hot-carrier degraded nMOSFETs by annealing in a nitrogen ambient. The recovery rate is investigated as a function of the annealing temperature, where the recovery for increasing temperatures is in agreement with the passivation processes. At the original post-metal anneal temperature of T = 400°C, the device's original performance is fully restored. Higher temperatures induce a permanent, unrecoverable change to the devices, manifested in a gradual V T shift. The recovery rate is found to be independent of both the transistor gate length and the cooling rate (quench, slow and stepped cooling) upon annealing. These findings are used to gain further understanding of the mechanisms behind the recovery of hot-carrier damage. The recovery rate exhibits Arrhenius behavior and the recovery data are consistent with Stesmans' recovery model.

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We investigate the operation of FETs with a high-K channel material, SrTiO 3 (K = 300). The transistors show lowleakage, high-capacitance operation with a sub-nm equivalent oxide thickness, in line with expectations. In depletion however, the gate-source capacitance appears to have an unusual 1/3power dependence on the device length and width. This awkward scaling behaviour is analyzed in detail in this paper and possible consequences for SrTiO 3 devices and related 2D-material transistors are discussed. It is argued to relate to the high-permittivity channel. This high permittivity is further experimentally shown to result in strong short-channel effects in 10-μm-long FETs, in spite of the highly scaled equivalent oxide thickness, when the operation temperature is lowered to 4.2 K.

Proefschrift ter verkrijging van de graad van doctor aan de Universiteit Twente, op gezag van de rector magnificus, prof. dr. ir. A. Veldkamp, volgens besluit van het College voor Promoties in het openbaar te verdedigen op donderdag 12 mei 2022 om 12.45 uur door Maurits Jelke de Jong geboren op 16 oktober 1990 te Heerenveen (Fr.) iv Dit proefschrift is goedgekeurd door: prof. dr. J. Schmitz (promotor) dr. ir. C. Salm

nMOSFETs have been degraded by hot-carrier injection and recovered by annealing in various ambients. Hydrogen will depassivate from the interface due to the hot-carriers, creating dangling bonds, which will cause a shift in the various parameters like the threshold voltage, the subthreshold swing and the interface defect density. This paper investigates how the various ambients (argon, hydrogen, hydrogen plasma and atomic hydrogen) influence the recovery rate of these parameters. Results are discussed in the framework of Stesmans' model for hydrogen passivation at the interface. Furthermore, the influence of a silicon nitride scratch protection layer on the recovery is investigated. These results can be used to enhance the recovery rate and achieve more recovery at a lower anneal temperature, which is important for delaying the accumulative effect of hotcarrier degradation and, as such, extending the device lifetime.