1,721,176 research outputs found
RECOVERY OF SILC IN ULTRA-THIN GATE OXIDES BY LOW FIELD ELECTRON INJECTION
No full textIn this work we have shown that SILC in thin oxides can be effectively reduced at room temperature by performing low field current injection. By increasing the amount of injected charge, SILC continuously decreases and no saturation steady state level is reached. We attribute this decrease to the passivation of the oxide weak spots by electron trapping in those defects mediating SILC. This poses some questions on the true meaning of DC SILC, on the corresponding methods of measurements, and on its impact on the device lifetime
Wear-out and breakdown of ultra-thin gate oxides after irradiation
No full textThe enhancement of gate leakage current after exposure to ionising radiation is generally believed to be the major challenge for devices and circuits operating in harsh radiation environments. How ultra-thin gate oxides subjected to heavy ion irradiation react to a subsequent electrical stress performed at low voltages has been investigated. Even in devices exhibiting small (or even negligible) enhancement of the leakage current, the time-to-breakdown is substantially reduced in comparison with unirradiated samples due to the onset of a soft or hard breakdown, in contrast with previous results found on thicker oxides
Degradation Dynamics of Ultrathin Gate Oxides Subjected to Electrical Stress
No full textThe sigmoidal behavior exhibited by the current-time characteristics of constant voltage-stressed metal-oxide-semiconductor (MOS) capacitors with ultrathin oxides is ascribed to a self-constrained increase of the leakage sites population that assist the conduction process between the electrodes. To mathematically describe this dynamical process we consider a classical model of population growth theories such as the Verhulst differential equation. The role that might play the background tunneling current in the evolutionary trajectory of the breakdown event is also discussed
Ionising Radiation Effects on Ultra-Thin Gate oxide MOS
No full textINVITED PAPER
We have briefly reviewed the most important degradation mechanisms affecting ultra-thin gate oxides after exposure to ionizing irradiation. The increase of the gate leakage current seems the most crucial issue for device lifetime, especially for non-volatile memory and dynamic logic. The build-up of positive charge in the oxide and the subsequent threshold voltage shift, which was the major concern for thicker oxide, are no longer appreciable in today’s devices due to the reduced oxide thickness permitting a fast recombination of trapped holes with electrons from interfaces. Among the leakage currents affecting thin oxides we have considered here the Radiation Induced Leakage Current (RILC) and the Radiation Soft Breakdown (RSB). RILC is observed after irradiation with a low Linear Energy Transfer (LET) radiation source and comes from a trap-assisted tunneling of electrons mediated by the neutral traps produced by irradiation. RILC depends on the applied bias during irradiation and the maximum is measured when devices are biased in flat band. Contrarily to RILC, RSB is observed after irradiation with high LET ions and derives from the formation of several conductive paths across the oxide corresponding to the ion hits. RSB conduction is explained by the theory of the Quantum Point Contact as also proposed for the electrically induced Soft breakdown. Finally, we present some preliminary results, which indicate that although the direct effects of irradiation (in terms of gate leakage current increase) are small for oxide thinner than 3nm, it is possible that these devices may experience an accelerated wear-out and/or breakdown after subsequent electrical stress relative to a fresh (not irradiated) device
New Issues in Radiation Effects on Semiconductor Devices
No full textWe have briefly reviewed the most important degradation mechanisms affecting ultra-thin gate oxides after exposure to ionizing irradiation. The increase of the gate leakage current seems the most crucial issue for device lifetime, especially for non-volatile memory and dynamic logic. The build-up of positive charge in the oxide and the subsequent threshold voltage shift, which was the major concern for thicker oxide, are no longer appreciable in today’s devices due to the reduced oxide thickness permitting a fast recombination of trapped holes with electrons from interfaces. Among the leakage currents affecting thin oxides we have considered here the Radiation Induced Leakage Current (RILC) and the Radiation Soft Breakdown (RSB). RILC is observed after irradiation with a low Linear Energy Transfer (LET) radiation source and comes from a trap-assisted tunneling of electrons mediated by the neutral traps produced by irradiation. RILC depends on the applied bias during irradiation and the maximum is measured when devices are biased in flat band. Contrarily to RILC, RSB is observed after irradiation with high LET ions and derives from the formation of several conductive paths across the oxide corresponding to the ion hits. Finally, we present some preliminary results, which indicate that although the direct effects of irradiation (in terms of gate leakage current increase) are small for oxide thinner than 3nm, it is possible that these devices may experience an accelerated wear-out and/or breakdown after subsequent electrical stress relative to a fresh (not irradiated) device
IONIZING RADIATION EFFECTS ON ULTRA-THIN OXIDE MOS STRUCTURES
No full textWe have briefly reviewed the most important degradation mechanisms affecting ultra-thin gate oxides after exposure to ionizing irradiation. The increase of the gate leakage current seems the most crucial issue for device lifetime, especially for non-volatile memory and dynamic logic. The build-up of positive charge in the oxide and the subsequent threshold voltage shift, which was the major concern for thicker oxide, are no longer appreciable in today's devices due to the reduced oxide thickness permitting a fast recombination of trapped holes with electrons from interfaces. Among the leakage currents affecting thin oxides we have considered here the Radiation Induced Leakage Current (RILC) and the Radiation Soft Breakdown (RSB). RILC is observed after irradiation with a low Linear Energy Transfer (LET) radiation source and comes from a trap-assisted tunneling of electrons mediated by the neutral traps produced by irradiation. RILC depends on the applied bias during irradiation and the maximum is measured when devices are biased in flat band. Contrarily to RILC, RSB is observed after irradiation with high LET ions and derives from the formation of several conductive paths across the oxide corresponding to the ion hits. RSB conduction is explained by the theory of the Quantum Point Contact as also proposed for the electrically induced Soft breakdown. Finally, we present some preliminary results, which indicate that although the direct effects of irradiation (in terms of gate leakage current increase) are small for oxide thinner than 3nm, it is possible that these devices may experience an accelerated wear-out and/or breakdown after subsequent electrical stress relative to a fresh (not irradiated) device
Stress Induced Leakage Current under pulsed voltage stress
No full textIn this work we have investigated the behaviour of ultra thin gate oxide subjected to pulsed voltage stress. The results have been compared with similar those obtained under constant voltage stress condition. Stress Induced Leakage Current (SILC) has been studied as a function of the total dose of injected charge and the pulse frequency. A further comparison has been done between SILC and Radiation Induce Leakage Current when either pulsed or constant bias voltage has been applied during irradiation
Stress Induced Leakage Current and Radiation Induced Leakage Current in MOS devices with ultra-thin gate oxide
No full textContemporary Metal Oxide Semiconductor (MOS) FETs are fabricated by using deep-submicron technologies where the oxide thickness is lower than tox=10 nm. In these devices leakage current across the oxide at low oxide fields (3 MV/cm2<Eox<6 MV/cm2) can increase after electrical or radiation stresses. This leakage is known as stress induced leakage current (SILC) or radiation induced leakage current (RILC). In this contribution we show that both SILC and RILC have similar conduction mechanisms identifiable in electron assisted tunnelling through oxide neutral traps
Logistic model for leakage current in electrical stressed ultra-thin oxides
No full textIt is shown that the leakage current flowing through an ultra-thin gate oxide in a metal-oxide-semiconductor structure subjected to a constant voltage stress can be described by a Verhulst-type logistic model. An exponential growth at the outset is followed by a saturation in the conduction characteristic, which indicates that, after a rapid expansion, the damaged area reaches an upper bound. This sigmoidal behaviour is interpreted as a self-constrained growth of the leakage site population
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