Degradation and Breakdown of Gate Oxides in VLSI Devices

Abstract

A model for the degradation and breakdown of thin gate oxide films is presented. During electrical stresses, a small fraction of the energy of the tunnel electrons that is dissipated in the oxide is converted into the creation of electron traps. When a critical density of traps is achieved, a fast runaway process leads the oxide to break down and its insulating properties are irreversively lost. It is demonstrated that the total charge injected to breakdown depends on the applied current in accordance with recently published results. The quasi‐linear log (time‐to‐breakdown) versus log (current density) plot experimentally obtained for VLSI oxides (tox ≈ 100 Å) is correctly predicted.

Time Dependent Dielectric Breakdown Measurements on RPECVD and Thermal Oxides

“…These values are comparable to the values found by Dumin et al 4 For the statistical analysis of the wearout phenomena, we use the technique of Sune et aI. [45][46][47][48] Up to now this model has been applied only to the highest quality thermal oxides, both from university and industrial sources. In this paper, we apply the theory to an RPECVD oxide created by an alternate fabrication method.…”

“…The generation of the traps is treated with Poisson statistics. [45][46][47][48] The use of this statistical approach is valid if (i) the number of cells is very large, (it) the generation of any trap is unconnected with the generation of any other trap, and (iii) the average trap number in any cell across the entire oxide is <<1. 52 We assume that neutral sites that do not change charge state do not contribute to wearout.…”

Failure physics of ultra-thin SiO2gate oxides near their scaling limit

“…generation of defects during stress. Neutral electron traps, interface states, hole traps and slow states are generated during stress [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Even though there is disagreement about the physics of the generation of those defects, there is a general consensus in considering that their build-up finally triggers the breakdown.…”

“…On one side, we have the so-called thermo-chemical model of McPherson and co-workers, who consider that the generation of defects is driven by the electric field and the stress time [12]. On the other side, there is the electron energy dissipation model, which requires the injection of carriers through the oxide [13][14][15][16][17][18][19][20][21][22][23][24]. In our opinion, the McPherson approach [12] has had a certain success because it gives a physical basis to the E model for lifetime extrapolation, while the energy dissipation model provides a natural basis for the 1/E model under some circumstances.…”