Trap Generation Process Research Articles

Oxygen vacancy defect engineering using atomic layer deposited HfAlOx in multi-layered gate stack

This work evaluates the defects in high quality atomic layer deposited (ALD) HfAlOx with extremely low Al (<3% Al/(Al + Hf)) incorporation in the Hf based high-k dielectrics. The defect activation energy estimated by the high temperature current voltage measurement shows that the charged oxygen vacancies, V+/V2+, are the primary source of defects in these dielectrics. When Al is added in HfO2, the V+ type defects with a defect activation energy of Ea ∼ 0.2 eV modify to V2+ type to Ea ∼ 0.1 eV with reference to the Si conduction band. When devices were stressed in the gate injection mode for 1000 s, more V+ type defects are generated and Ea reverts back to ∼0.2 eV. Since Al has a less number of valence electrons than do Hf, the change in the co-ordination number due to Al incorporation seems to contribute to the defect level modifications. Additionally, the stress induced leakage current behavior observed at 20 °C and at 125 °C demonstrates that the addition of Al in HfO2 contributed to suppressed trap generation process. This further supports the defect engineering model as reduced flat-band voltage shifts were observed at 20 °C and at 125 °C.

Series resistance effect on time zero dielectrics breakdown characteristics of MOSCAP with ultra-thin EOT high-k/metal gate stacks**Project supported by the National High Technology Research and Development Program (863 Program) of China (No. SS2015AA010601), the National Natural Science Foundation of China (Nos. 61176091, 61306129), and the Opening Project of the Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics,

The time zero dielectric breakdown characteristics of MOSCAP with ultra-thin EOT high-k metal gate stacks are studied. The TZDB results show an abnormal area dependence due to the series resistance effect. The series resistance components extracted from the Fowler–Nordheim tunneling relation are attributed to the spreading resistance due to the asymmetry electrodes. Based on a series model to eliminate the series resistance effect, an area acceleration dependence is obtained by correcting the TZDB results. The area dependence follows Poisson area scaling rules, which indicates that the mechanism of TZDB is the same as TDDB and could be considered as a trap generation process.

Extended Mie-Grüneisen molecular model for time dependent dielectric breakdown in silica detailing the critical roles of O–SiO3 tetragonal bonding, stretched bonds, hole capture, and hydrogen release

An extended Mie-Grüneisen molecular model is presented, which describes a bond-breakage process for O–SiO3 tetragonal molecules in silica and the trap-generation process that occurs during time dependent dielectric breakdown (TDDB) testing. This quantitative molecular model correctly describes important physics routinely reported for silica TDDB testing: the generation of E′ centers, a breakdown strength of Ebd∼15MV∕cm, an effective dipole-moment range of peff=7–13eÅ, and a zero-field activation energy range for bond breakage of ΔHo*=1−2eV. The bond-breakage/trap-generation mechanism is shown to occur when the Si ion transitions from its primary energy minimum (with fourfold coordination) to a secondary saddle point (with threefold coordination). The molecular model also shows clearly that current induced hole capture and hydrogen release can play critically important roles in the TDDB process.

The role of localized states in the degradation of thin gate oxides

A model is proposed to address the effects of oxide electric field and anode bias, as well as the role of hydrogen, in the trap generation process. The oxide wear-out phenomenon is considered as a multi-step process initiated by the capture of injected electrons by localized states in SiO 2. The captured electrons significantly weaken the corresponding Si–O bond, which becomes unstable with respect to the applied electric field and temperature. The hydrogen present in the oxide (due to the anode hydrogen release process) prevents restoration of the broken bonds and leads to the generation of neutral E′ centers. The model describes the charge-to-breakdown dependence on the electron energy, electric field, temperature, and oxide thickness.

A model for gate oxide wear out based on electron capture by localized states

A model is proposed which addresses the effects of the oxide electric field and anode bias as well as the role of hydrogen in the trap generation process. The oxide wear-out phenomenon is considered as a multistep process initiated by the capture of injected electrons by localized states in SiO2. The captured electron significantly weakens the corresponding Si–O bond, which becomes unstable with respect to the applied electric field and temperature. The hydrogen presented in the oxide (due to anode hydrogen release process) prevents restoration of the broken bond that leads to the generation of a neutral E′ center. The model describes the charge-to-breakdown dependence on the electron fluence and energy, electric field, temperature, and oxide thickness.

A spin-dependent recombination study of radiation-induced P/sub b1/ centers at the [001] Si/SiO/sub 2/ interface

The generation of interface defects at the Si/SiO/sub 2/ boundary is an important aspect of radiation damage in MOS devices. The observations of several independent groups over the last twenty years have demonstrated that Si/SiO/sub 2/ interface silicon dangling bond defects called P/sub b/ centers dominate the interface trap generation process. In the technologically important [001] Si/SiO/sub 2/ system, two P/sub b/ variants may appear. One variant, the P/sub b0/ center, generally dominates radiation and hot carrier damage; however, a less well studied variant, called P/sub b1/, may play a significant secondary role. The electronic properties of the P/sub b1/ centers are quite controversial. Early work by Gerardi et al. indicated quite strongly that the P/sub b1/ centers, like the other P/sub b/ family members, have two levels in the Si bandgap. Several recent publications by Stesmans and Afanas'ev argue that P/sub b1/ centers do not have any levels in the Si bandgap. We present spin-dependent recombination (SDR) measurements which demonstrate that P/sub b1/ centers have levels around the middle of the Si bandgap. Our SDR results strongly suggest that the P/sub b1/ center electron correlation energy is significantly smaller than that of P/sub b0/. Our results may help explain some apparently contradictory studies involving the energy distribution of radiation induced interface states. We also discuss possible relevance of these results to the precision of oxide charge measurements based on the shifts in capacitance versus voltage curves for the Fermi energy at midgap.

Reversible and irreversible interface trap centres generated at high electric fields in MOS structures

In this work, we present results of the study of interface trap generation processes at the Si–SiO2 interface in MOSFET structures caused by high oxide field stress. Changes in areal density and energy distribution in the Si band gap of the interface traps were monitored using the II-level conventional charge pumping technique. The generated interface traps were divided into two types: reversible and irreversible in relation to their discharge by low field electron injection. A broad presentation of changes in density and energy distribution of the interface traps was included. The threshold value of oxide field for interface trap generation was obtained.

A physically based predictive model of Si/SiO2 interface trap generation resulting from the presence of holes in the SiO2

A physically based model is developed which explains apparently unrelated aspects of the Si/SiO2 interface trap generation process; the predictions of the model are in at least semiquantitative agreement with observations previously reported in the literature. The model involves interactions between molecular hydrogen and trivalent silicon dangling bond defects in the oxide (E′ centers) and at the Si/SiO2 interface (Pb centers). Our model is primarily directed at interface trap generation caused by ionizing radiation and by hot hole injection phenomena observed in short channel transistors.

Oxide and interface degradation resulting from substrate hot-hole injection in metal-oxide-semiconductor field-effect transistors at 295 and 77 K

Substrate hot-hole injection (SHI) induced hole trapping and interface trap generation have been characterized at 295 and 77 K. At both temperatures, the trapping is independent of the injection conditions in the silicon, and is fairly insensitive to the oxide field. Initial trapping efficiencies are about 2.5 times higher at 77 K. The experiments show that essentially the same traps are being filled at the two temperatures, and that the increase in trapping efficiency can be attributed to a larger effective cross section of the traps at 77 K. Hot-hole induced interface trap generation is observed to be independent of the injection conditions in the silicon, and to decrease with increasing oxide field magnitude. More interface traps are generated at 77 K for the same injected fluence. This is in contrast to the characteristics of irradiation-induced interface trap generation. The presence of holes at the Si-SiO2 interface is the key factor in the direct interface trap generation process acting during hot-hole injection. Following low-temperature SHI, an additional temperature-activated generation mechanism, attributed to the migration of H+, is observed in isochronal anneal experiments. This delayed mechanism is identical to the one that accounts for most of the irradiation-induced interface trap generation.