High-field and current-induced positive charge in thermal SiO2 layers

Abstract

The generation of a bulk positive charge in SiO2 layers of silicon gate metal-oxide-silicon (MOS) devices, under the conditions of high-field and charge injection is studied. The time dependence of the positive charge and its spatial distribution as a function of the oxide thickness and electric field are all consistent with an impact ionization-recombination model which takes into account both the spatial and the field dependence of the ionization probability. The nature of the ionization, either band-to-band, or traps ionization, is still unknown. Bulk positive charge of the same nature is also formed in Al gate oxides. Nevertheless, it was not always observed in previous works since a much larger Si-SiO2 interfacial positive charge is also generated in these samples.

Physico-chemical processes in metal–oxide–semiconductor transistors with thick gate oxide during high electric field stress

“…It should be considered two cases: (1) thin oxide (t ox 6 10 nm) and (2) thick oxide (t ox > 10 nm). In the former case, 2 Regardless of the gate voltage sign, the tunnelling of the electrons to the oxide conduction band, from the substrate or gate, will be considered. the hot electrons, tunnelling into oxide conduction band, pass the gate oxide without collisions, since their travel distance is small and, consequently, the probability for the collision with the electrons in the covalent oxide bonds is low [10,21].…”

“…A complete study of the mechanisms responsible for defect creation in metal-oxide-semiconductor field-effect transistors (MOSFETs) during the high electric field stress (HEFS), (a very important stress type [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]) has been pursued. The idea is to give a complete analysis of the physicochemical processes in the gate oxide (SiO 2 ) and at the gate oxide/substrate (SiO 2 /Si) interface during HEFS, since it could not been found in the literature.…”

Generation of positive and negative charges under Fowler–Nordheim injection and breakdown

“…Hironori Ushizaka a) NTT Telecommunications Energy Laboratories, 3 Characteristics shifts and time to breakdown of metal-oxide-semiconductor devices due to the Fowler-Nordheim current were investigated. The characteristics shifts were changed by holes and electrons generated in the gate oxides.…”

“…In the case of gate oxide thickness greater than 70 nm, electrons injected into the gate oxide by the FN process cause impact ionization, and positive charges are generated. 3 At gate oxide thicknesses below 30 nm, in addition to the positive charges, negative charges appear, especially when the gate electric field is below 9 MV/cm. 4,5 As a result of early research, it was considered that the positive and negative charges generated by the FN injection contributed to the breakdown of the gate oxide.…”

Behavior of SiO2 Under High Electric Field/Current Stress Conditions

“…2, 5, 6 For each trapping mechanism the density of trapped charge is given by (3). The time constant, T is related to the trap cross-section as given by (4). …”