Oxide Charge Detrapping Research Articles

Static and Dynamic Oxide-Trapped- Charge-Induced Variability in Nanoscale CMOS Circuits

The inter-device mismatch and intra-device temporal instability in the nanoscale CMOS circuits is examined from a unified point of view as a static and dynamic parts of the variability con-cerned with stochastic oxide charge trapping and de-trapping. This approach has been benchmarked on the recent evidence of the radiation-induced increase of inter-transistor mismatch in 60 nm ICs. A possible reliability limitation in ultrascale circuits concerned with the single or a few charged defect instability is pointed out and estimated.

Role of positive trapped charge in stress-induced leakage current for flash EEPROM devices

The transient behavior of hot hole (HH) stress-induced leakage current (SILC) in tunnel oxides is investigated. The dominant SILC mechanism is positive oxide charge-assisted tunneling (PCAT). The transient effect of SILC is attributed to positive oxide charge detrapping and thus the reduction of PCAT current. A correlation between SILC and stress-induced substrate current is observed. Our study shows that both SILC and stress-induced substrate current have power law time-dependence t/sup -n/ with the power factor n about 0.7 and 1, respectively. Numerical analysis for PCAT current incorporating a trapped charge caused Coulombic potential in the tunneling barrier is performed to evaluate the time- and field-dependence of SILC and the substrate current. Based on our model, the evolution of threshold voltage shift with read-disturb time in a flash EEPROM cell is derived. Finally, the dependence of SILC on oxide thickness is explored. As oxide thickness reduces from 100 /spl Aring/ to 53 /spl Aring/, the dominant SILC mechanism is found to change from PCAT to neutral trap-assisted tunneling (TAT).

Investigation of oxide charge trapping and detrapping in a MOSFET by using a GIDL current technique

We proposed a new measurement technique to investigate oxide charge trapping and detrapping in a hot carrier stressed n-MOSFET by measuring a GIDL current transient. This measurement technique is based on the concept that in a MOSFET the Si surface field and thus GIDL current vary with oxide trapped charge. By monitoring the temporal evolution of GIDL current, the oxide charge trapping/detrapping characteristics can be obtained. An analytical model accounting for the time-dependence of an oxide charge detrapping induced GIDL current transient was derived. A specially designed measurement consisting of oxide trap creation, oxide trap filling with electrons or holes and oxide charge detrapping was performed. Two hot carrier stress methods, channel hot electron injection and band-to-band tunneling induced hot hole injection, were employed in this work. Both electron detrapping and hole detrapping induced GIDL current transients mere observed in the same device. The time-dependence of the transients indicates that oxide charge detrapping is mainly achieved via field enhanced tunneling. In addition, we used this technique to characterize oxide trap growth in the two hot carrier stress conditions. The result reveals that the hot hole stress is about 10/sup 4/ times more efficient in trap generation than the hot electron stress in terms of injected charge.

Characterization of various stress-induced oxide traps in MOSFET's by using a subthreshold transient current technique

An oxide trap characterization technique by measuring a subthreshold current transient is developed. This technique consists of two alternating phases, an oxide charge detrapping phase and a subthreshold current measurement phase. An analytical model relating a subthreshold current transient to oxide charge tunnel detrapping is derived. By taking advantage of a large difference between interface trap and oxide trap time-constants, this transient technique allows the characterization of oxide traps separately in the presence of interface traps. Oxide traps created by three different stress methods, channel Fowler-Nordheim (F-N) stress, hot electron stress and hot hole stress, are characterized. By varying the gate bias in the detrapping phase and the drain bias in the measurement phase, the field dependence of oxide charge detrapping and the spatial distribution of oxide traps in the channel direction can be obtained. Our results show that 1) the subthreshold current transient follows a power-law time-dependence at a small charge detrapping field, 2) while the hot hole stress generated oxide traps have a largest density, their spatial distribution in the channel is narrowest as compared to the other two stresses, and 3) the hot hole stress created oxide charges exhibit a shortest effective detrapping time-constant.

Field and temperature effects on oxide charge detrapping in a metal–oxide–semiconductor field effect transistor by measuring a subthreshold current transient

A technique to characterize oxide charge detrapping in a Fowler–Nordheim stressed n-metal–oxide–semiconductor field effect transistor is proposed. This technique consists of two alternating phases, an oxide charge detrapping phase and a subthreshold current measurement phase. An analytical model relating a subthreshold current transient to oxide charge density and detrapping time constants was derived. By varying the gate bias in the detrapping phase and the ambient temperature, the field and temperature dependences of oxide charge detrapping can be obtained from the subthreshold current transients measured.