Increase in oxide hole trap density associated with nitrogen incorporation at the SiO2/SiC interface

Abstract

Nitrogen incorporation at the SiO2/SiC interface via high temperature nitric oxide annealing leads to the passivation of electrically active interface defects, yielding improved inversion mobility in the semiconductor. However, we find that such nitrided oxides can possess a larger density of hole traps than as-grown oxides, which is detrimental to the reliability of devices (e.g., can lead to large threshold voltage instabilities and to accelerated failure). Three different charge injection techniques are used to characterize this phenomenon in metal–oxide–semiconductor structures: x-ray irradiation, internal photoemission and Fowler–Nordheim tunneling. Some nitrogen-based atomic configurations that could act as hole traps in nitrided SiO2 are discussed based on first-principles density functional calculations.

Tailoring Oxide/Silicon Carbide Interfaces: NO Annealing and Beyond

“…Adapted from Refs. [103,104] region of the oxide. Since we have shown that more nitrogen would increase the mobility even further, other nitridation methods could maximize its density while confining it to the interface boundary.…”

“…This can be of concern even for n-channel transistors to which a negative gate bias can be applied to ensure that it is OFF in its idle state. Several methods have been used to accelerate hole exposure of the gate oxide such as x-ray irradiation [52], Fowler-Nordheim tunneling, and internal photoemission [104]. Figs.…”

“…Unlike hydrogen, nitrogen can reduce the energy of most of these atomic configurations by substituting for threefold-coordinated carbons or by inserting short suboxide bonds [90,130]. While it can suppress acceptor levels close to the 4H-SiC conduction band edge, the donor nature of nitrogen and its 5 valence electrons can then yield states close to, or even within, the semiconductor valence band [104]. If the resulting atomic configurations are located on the oxide side of the interface, they can therefore act as stable hole traps.…”

Spatial Localization of Carrier Traps in 4H-SiC MOSFET Devices Using Thermally Stimulated Current

“…1 from TSC curves measured at V rev = À100 V were N t,1 = 2. 25 ). The three TSC peak groups varied differently with bias.…”

“…24 Rozen et al have attributed the higher density of hole traps in NO-annealed oxides to the increased nitrogen incorporation at sites near the interface. 25 …”