Dependence of short channel length on negative/positive bias temperature instability (NBTI/PBTI) for 3D FinFET devices

A comprehensive study of the negative and positive bias temperature instability(NBTI/PBTI)of 3D FinFET devices with different small channel lengths is presented.It is found while with the channel lengths shrinking from 100 nm to 30 nm,both the NBTI characteristics of p-FinFET and PBTI characteristics of n-FinFET turn better.Moreover,the channel length dependence on NBTI is more serious than that on PBTI.Through the analysis of the physical mechanism of BTI and the simulation of 3-D stress in the FinFET device,a physical mechanism of the channel length dependence on NBTI/PBTI is proposed.Both extra fluorine passivation in the corner of bulk oxide and stronger channel stress in p-FinFETs with shorter channel length causes less NBTI issue,while the extra nitrogen passivation in the corner of bulk oxide induces less PBTI degradation as the channel length decreasing for n-FinFETs.The mechanism well matches the experimental result and provides one helpful guide for the improvement of reliability issues in the advanced FinFET process.

Improvement of Operation Characteristics for MONOS Charge Trapping Flash Memory with SiGe Buried Channel

We propose and investigate a novel metal/SiO_2/Si_3N_4/SiO_2/SiGe charge trapping flash memory structure（named as MONOS）, utilizing Si Ge as the buried channel. The fabricated memory device demonstrates excellent programerasable characteristics attributed to the fact that more carriers are generated by the smaller bandgap of Si Ge during program/erase operations. A flat-band voltage shift 2.8 V can be obtained by programming at ＋11 V for 100 us. Meanwhile, the memory device exhibits a large memory window of ~7.17 V under ±12 V sweeping voltage, and a negligible charge loss of 18% after 104 s＇ retention. In addition, the leakage current density is lower than 2.52 × 10^（-7） A·cm^（-2） below a gate breakdown voltage of 12.5 V. Investigation of leakage current-voltage indicates that the Schottky emission is the predominant conduction mechanisms for leakage current. These desirable characteristics are ascribed to the higher trap density of the Si_3N_4 charge trapping layer and the better quality of the interface between the SiO_2 tunneling layer and the Si Ge buried channel. Therefore, the application of the Si Ge buried channel is very promising to construct 3 D charge trapping NAND flash devices with improved operation characteristics.

Improving interfacial and electrical properties of HfO_(2)/SiO_(2)/p-Si stacks with N_(2)-plasma-treated SiO_(2) interfacial layer

The effect of N_(2)-plasma-treated SiO_(2) interfacial layer on the interfacial and electrical characteristics of HfO_(2)/SiO_(2)/p-Si stacks grown by atomic layer deposition(ALD) was investigated.The microstructure and interfacial chemical bonding configuration of the HfO_(2)/SiO_(2)/Si stacks were also examined by high-resolution transmission electron microscopy(HRTEM) and X-ray photoelectron spectroscopy(XPS).Compared with the samples without N2-plasma treatment,it is found that the samples with N2-plasma treatment have less oxygen vacancy density for SiO_(2) interfacial layer and better HfO_(2)/SiO_(2) interface.In agreement with XPS analyses,electrical measurements of the samples with N2-plasma treatment show better interfacial quality,including lower interface-state density(Dit,9.3 × 1011 cm^(-2)·eV^(-1) near midgap) and lower oxidecharge density(Q_(ox),2.5 × 1012 cm^(-2)),than those of the samples without N_(2)-plasma treatment.Additionally,the samples with N_(2)-plasma treatment have better electrical performances,including higher saturation capacitance density(1.49 μF·cm^(-2)) and lower leakage current density(3.2 × 10^(-6) A·cm^(-2) at V_(g)=V_(fb)-1 V).Furthermore,constant voltage stress was applied on the gate electrode to investigate the reliability of these samples.It shows that the samples with N_(2)-plasma treatment have better electrical stability than the samples without N_(2)-plasma treatment.

Recent developments in nonferrous metals and related materials for biomedical applications in China:a review

Biomedical materials have received increasing attention in recent decades and have been used in medical applications to advance patient care,such as prosthetic implants,tissue repair and regeneration,drug delivery systems,pharmaceutical or biological therapy products,and sensitive diagnostic technologies.Among different types of biomedical materials,nonferrous metals and related materials(NMRMs)are important and attractive candidates.The updating of biomedical NMRMs and devices heavily relies on original research and applicationoriented innovation.Here,we provide recent research findings and succinct insights into the developments in NMRMs for biomedical applications in China,including the use of titanium,magnesium,copper,zinc,cobalt,zirconium,hafnium,niobium,rhenium,tantalum,tungsten,silver,gold,platinum,palladium,their alloys and compounds,rare earths,high-entropy alloys,and liquid metals.Finally,the literature review concludes with several possible directions of NMRMs for new and future developments in biomedical engineering.

X-ray irradiation-induced degradation in Hf_(0.5)Zr_(0.5)O_(2) fully depleted silicon-on-insulator n-type metal oxide semiconductor field-effect transistors

The n-type ultrathin fully depleted silicon-on-insulator(FDSOI) metal-oxide-semiconductor field-effect transistors(MOSFETs),with a Hf_(0.5)Zr_(0.5)O_(2) high dielectric permittivity(high-k) dielectric as gate insulator,were fabricated.The total ionizing dose effects were investigated,and an X-ray radiation dose up to 1500 krad(Si) was applied for both long-and short-channel devices.The short-channel devices(0.025-0.100 μm) exhibited less irradiation sensitivity compared with the long-channel devices(0.35-16 μm),leading to a 71% reduction in the irradiation-induced drain current growth and a 26% decrease in the shift of the threshold voltage.It was experimentally demonstrated that the OFF mode is the worst case among the three working conditions(OFF,ON and A110) for short-channel devices.Also,the determined effective electron mobility was enhanced by 38% after X-ray irradiation,attributed to the different compensations for charges triggered by radiation between the highk dielectric and buried oxide.By extracting the carrier mobility,gate length modulation,and source/drain(S/D)parasitic resistance,the degradation mechanism on X-ray irradiation was revealed.Finally,the split capacitance-voltage measurements were used to validate the analysis.