C. Papadas

Temperature dependence of the Fowler–Nordheim current in metal‐oxide‐degenerate semiconductor structures

A comprehensive study of the temperature dependence of the Fowler–Nordheim (F–N) tunnel emission in a metal‐oxide‐semiconductor structure is conducted both theoretically and experimentally. The theoretical variations with temperature of the F–N emission is analyzed both for metallic and degenerate semiconductor cathode materials. The influence of the electron concentration of a degenerate semiconductor on the amplitude of the F–N current is demonstrated. A new analytical formula for the F–N current temperature dependence is derived from the exact expressions using the Sommerfeld expansion. This new analytical approximation proves to be much more efficient than the previous analytical formula developed by Good and Muller [Field Emission, Handbuch der Physik, Vol. 21 (Springer, Berlin, 1956)] and may be very useful for F–N current computer‐aided‐design‐oriented numerical simulation. The experimental study of the F–N current in MOS capacitors clearly demonstrates the strong impact of temperature on the F–N e...

Modeling of the intrinsic retention characteristics of FLOTOX EEPROM cells under elevated temperature conditions

A model for the intrinsic retention characteristics of FLOTOX EEPROM cells is presented, which is based on the temperature dependence of the Fowler-Nordheim emission current. This model which has been successfully tested on single-poly-FLOTOX EEPROM cells, enables the device lifetime to be calculated for given memory operating conditions, instead of being extrapolated as is usually done. The sensitivity of the retention characteristics to several technological parameters is also investigated. It is expected that this intrinsic retention model (with minor modifications) will also be applicable to FLASH EEPROM cells. >

Dielectric reliability in deep-submicron technologies: From thin to ultrathin oxides

Abstract This paper focuses on the dielectric reliability in the thin and ultrathin oxide regime. The wear-out mechanisms and the breakdown phenomena related to the Si SiO 2 system are considered within the 12nm-5nm oxide thickness range. The degeneration evolution with respect to the oxide thickness and the consequences of the mechanisms involved in the various failure modes which limit the dielectric reliability are discussed.

On the charge build-up mechanisms in gate dielectrics

Abstract The variation of the bulk oxide charge build-up characteristics of gate dielectrics after different Fowler-Nordheim stress conditions are investigated. It is proved that none of the degradation mechanism known so far are capable of explaining the evolution of the bulk oxide degradation features after high field electrical stress. Instead, it is shown that the degradation process can be attributed to a universal charge build-up empirical law. Besides, a new and simple method for analyzing the so-called “turn-over” phenomenon in MOS structures is proposed. The method enables the monitoring of the whole Si band gap, at room temperature and without any assumption concerning the nature of the interface traps (donor-or acceptor-like). Finally, comparison between SiO 2 and nitridated oxides in N 2 O ambient is conducted in terms of volume/interface trapping properties.

Generalized trapping kinetic model for the oxide degradation after Fowler–Nordheim uniform gate stress

The practicality of modeling the power law degradation observed in thin dielectrics after Fowler–Nordheim stress has been demonstrated on the basis of a generalized trapping approach with appropriate trap cross-section and density profiles. A detailed mathematical analysis of the negative bulk oxide charge kinetics has been established using incomplete Gamma and generalized hypergeometric functions, after assuming exponentially varying trap cross-section and density profiles throughout the oxide. These spatial distributions could be due to the structural nature of the oxide after growth. Moreover, the asymmetry of the charge distribution centroid for negative and positive gate bias stress has been satisfactorily interpreted by neglecting the trapping in the tunneling region near the cathode. Overall this generalized kinetic trapping model provides very good fitting of the variation of the trapped oxide charge with the injection dose for oxide thicknesses between 5.5 and 10 nm. The evolution of the charge ...

Electric field dependence of TDDB activation energy in ultrathin oxides

A study of the electric field dependence of the TDDB activation energy is presented for 12 nm down to 4.7 nm thin oxides. It is shown that the TDDB activation energy depends linearly on the stress electric field and that this behavior depends strongly on the oxide thickness. Moreover, a relationship between the TDDB activation energy attenuation per WV/cm and the oxide thickness has been found. As will be demonstrated, these results are of great importance for the rigorous estimation of the oxide lifetime of both present and future technologies.

On the oxide thickness extraction in deep-submicron technologies

Thickness measurement of ultrathin oxides is more and more difficult due to the oxide thickness scale down following the supply voltage decrease in deep-submicron technologies. This paper discusses the drawbacks of the already existing extraction methods and proposes an original approach which has various advantages. This extraction procedure, based on the plot 1/C vs 1/(V/sub G/-V/sub FB/) obtained by classical C-V measurements, can be easily implemented and provides more accurate oxide thickness results.

New method for the extraction of the coupling ratios in FLOTOX EEPROM cells

A method for the extraction of the control gate and drain coupling ratios directly from FLOTOX EEPROM cells is proposed. The method is based on the dependence of the high state threshold voltage on the hold time of the write pulses. The principal advantages of the technique are its accuracy, simplicity, and rapidity, the fact that the so-called dummy cell is not required, and the fact that the coupling ratios obtained correspond to effective values which characterize the actual memory cell operation. >

UNIFIED MODEL FOR BREAKDOWN IN THIN AND ULTRATHIN GATE OXIDES (12-5 NM)

A unified model explaining the wear-out and the breakdown of thin and ultrathin films of silicon dioxide when subjected to electrical stressing is proposed. The suggested breakdown model is based on the ability of charge trapped inside the dielectric to increase locally the effective dielectric permittivity (e) of the material by increasing the polarization locally. The impact of this local perturbation to the macroscopic characteristics of the oxide is investigated. Breakdown is correlated with the existence of a fixed amount of trapped charge inside the oxide. Moreover, the dependence of this bulk oxide trapped charge at breakdown with respect to the oxide thickness has been justified by the suggested mechanism and has been found to have excellent agreement with the experimental data.

Temperature dependence of charge build-up mechanisms and breakdown phenomena in thin oxides under Fowler-Nordheim injection

Abstract The trapping properties of thin oxide layers during Fowler-Nordheim electron injection have been investigated as a function of temperature in the range 258–423 K. It is found that the bulk oxide trapped charge at breakdown is almost temperature independent, whereas the charge to breakdown varies by more than one order of magnitude. Therefore the bulk oxide trapped charge at breakdown appears as being the key wear out parameter which describes in a better way the oxide quality than the usual charge to breakdown. In addition, the activation energy of the charge to breakdown (around 0.14 eV) and that of the trapping efficiency (around 0.05 eV) have been quantitatively correlated through a generic degradation power law which governs the charge build-up mechanism in the bulk of the oxide layer during Fowler-Nordheim electron injection.