Real-time evolution of trapped charge in a SiO2 layer: An electrostatic force microscopy study

Abstract

Time-dependent motion of localized electrons and holes trapped in a SiO2 layer is visualized with electrostatic force microscopy. Both negative and positive charges of up to ∼1010 e/cm2 are trapped at a SiO2–Si interface in ∼500-nm-diam area with a voltage stress between the tip and the sample. There is a higher probability for trapped charges to spread out in the plane direction than to de-trap toward the Si substrate. The dynamics is explained with diffusion and drift of the charges induced by Coulombic interaction.

Kelvin probe microscopy for reliability investigation of RF-MEMS capacitive switches

“…The contribution from surface migration, although cannot be overruled, seems to be of minor importance. Here it must be pointed out that the present works results are in relatively good agreement with the ones observed in 400 nm thermally gown Si 2 O [19], although there the surface charge migration was non negligible. In order to get a better insight on the charge decay mechanisms we fitted the stretched exponential law to experimental data.…”

“…Finally, the decay time constant, determined by fitting the stretched exponential law, was found to have a value of about 259±30sec and practically be independent of applied bias magnitude, which is the injection electric field. The obtained time constant values from LTO lie close to one, of about 380 sec in dry Si 2 O grown at 950°C, which has been determined by applying the stretched exponential law to the data in [19]. Moreover, the present work experimental results indicate that the discharge process is independent of the charging one.…”

Towards prognostics for electronics components

“…Steady-state methods include chronic over-voltage and over-current. Applying high gate voltages [13], setting gate voltage (V g ) to maximize drain current [14], and applying current overstress across the drain [15] have been shown to induce hot carrier and TBBD [9].…”

Degradation of RF MEMS capacitive switches

“…From what we have been able to find, quantified measurements of surface charge transport on a material most similar to our dielectric were done by Buh et al [66]. They do not use the same materials, but it does concern a silicon-based dielectric: their article reports a diffusion coefficient of holes on a SiO 2 surface of 0.00035 µm 2 /s.…”

“…These measurements were used to get an estimated diffusion coefficient between 0.003 and 0.010 µm 2 /s. Although not much data is available on charge diffusing on a silicon nitride dielectric, it seems a reasonable figure when comparing it to the results of [66]. Following the modeling methodology used in [59], we showed how ohmic self-drift results in the used diffusion equation.…”