Gamma-ray-irradiation effects on the leakage current and reliability of sputtered TiO2 gate oxide in metal–oxide–semiconductor capacitors

Abstract

The leakage current and reliability characteristics of γ-ray-irradiated sputtered titanium dioxide (TiO2) thin films have been systematically investigated. Analytical results revealed that the inferior polycrystallinity and the larger leakage current of the anatase structure of unirradiated TiO2 thin film could be effectively improved by raising the irradiation dose at low γ-ray doses [≦10 kGy(TiO2)]. However, any higher dose [>10 kGy(TiO2)] causes undesirable deterioration of the film crystallinity, yielding an increased leakage current. The optimal dose of γ-rays [10 kGy(TiO2) in this work] not only provides a proper energy transfer to the TiO2 film, but also reduces the oxygen deficiency and/or Si-diffusion contamination, resulting in a superior crystallinity, and thus causing the reduced leakage current. The excellent agreement between the E model (thermochemical-breakdown model) and the time-dependent-dielectric-breakdown data suggested strongly that the best long-term reliability of metal–oxide–semiconductor capacitors with the TiO2 gate oxide treated by 10 kGy(TiO2) of γ rays was due to the superior crystallinity and the smaller hole trap density at the TiO2/Si interface, resulting in an increased activation energy, thus reducing the occurrence of breakdown.

The influence of irradiation on the microhardness and photoluminescence of SiO2

“…Wang et al [5] demonstrated that, after gamma irradiation at low doses (≤10 4 Gy), the oxygen deficiency decreases and radiation-enhanced crystallization occurs at the TiO 2 -SiO-Si interface. This leads to a decrease in the number of hole-type traps and a high thermal activation of the current.…”

“…Demidov et al [4] showed that specific radiation actions can result in a decrease in the thickness of the SiO 2 transition defect layer and in a considerable reduction of the microdefect density at the interface. Wang et al [5] found that, at low gamma radiation doses ( ≤ 10 6 R or 10 4 Gy), the leakage current through the TiO 2 -SiO-Si interface decreases with an increase in the dose.…”

“…Metal-oxide-semiconductor field-effect transistors, metal oxide capacitors, and solar cells involve thin oxide layers, as a rule, composed of SiO 2 , whose mechanical strength and electrical insulation characteristics are close to a limit [1][2][3][4][5][6]. Oxide layers can appear to be most sensitive to radiation that has an effect on devices intended for the investigation of the interplanetary space; on instruments used in communication, metrology, navigation, satellite observations, and nuclear power plants; and on high-energy particle detectors.…”

Physics and Modeling of Radiation Effects in Advanced CMOS Technology Nodes

“…To some extent this is related to the fact that the pre-irradiation performance of these dielectrics is in many cases not optimized yet. For a not too high total dose irradiation can have a beneficial impact on the properties of the dielectric layer resulting in a reduction of the leakage current [27] or interface trap concentration [28]. Al 2 O 3 /SiO x N y stacks have a good radiation resistance up to 10 Mrad(SiO 2 ) in case that proper annealing steps are used, pointing out the promising potential of these high-k dielectrics [28].…”

Atomic Layer Deposition of TiO2using Titanium Isopropoxide and H2O: Operational Principle of Equipment and Parameter Setting

“…TiO 2 is a material that has been widely investigated for use in diverse applications such as photocatalysts [1], optical coatings [2], and high permittivity dielectric layers for gate oxides [3]. In addition, TiO 2 is used for applications such as dynamic random access memory (DRAM) [4,5] and ferroelectric random access memory (FeRAM) [6].…”