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.

Review of deep ultraviolet photodetector based on gallium oxide

Ultraviolet(UV) photodetectors(PDs) have drawn great attention in recent years due to their potential application in civil and military fields. Because of its ultrawide bandgap, low cost, strong radiation hardness, and high thermal and chemical stability with high visible-light transparency, Ga_2O_3 is regarded as the most promising candidate for UV detection.Furthermore, the bandgap of Ga_2O_3 is as high as 4.7–4.9 eV, directly corresponding to the solar-blind UV detection band with wavelength less than 280 nm. There is no need of doping in Ga_2O_3 to tune its bandgap, compared to AlGaN, MgZnO,etc, thereby avoiding alloy composition fluctuations and phase separation. At present, solar-blind Ga_2O_3 photodetectors based on single crystal or amorphous Ga_2O_3 are mainly focused on metal–semiconductor–metal and Schottky photodiodes.In this work, the recent achievements of Ga_2O_3 photodetectors are systematically reviewed. The characteristics and performances of different photodetector structures based on single crystal Ga_2O_3 and amorphous Ga_2O_3 thin film are analyzed and compared. Finally, the prospects of Ga_2O_3 UV photodetectors are forecast.

Thermal effect on endurance performance of 3-dimensional RRAM crossbar array

Three-dimensional（3D） crossbar array architecture is one of the leading candidates for future ultra-high density nonvolatile memory applications. To realize the technological potential, understanding the reliability mechanisms of the3 D RRAM array has become a field of intense research. In this work, the endurance performance of the 3D 1D1 R crossbar array under the thermal effect is investigated in terms of numerical simulation. It is revealed that the endurance performance of the 3D 1D1 R array would be seriously deteriorated under thermal effects as the feature size scales down to a relatively small value. A possible method to alleviate the thermal effects is provided and verified by numerical simulation.

Impact of O_(2)post oxidation annealing on the reliability of SiC/SiO_(2)MOS capacitors

The effects of dry O_(2)post oxidation annealing(POA)at different temperatures on SiC/SiO_(2)stacks are comparatively studied in this paper.The results show interface trap density(Dit)of SiC/SiO_(2)stacks,leakage current density(Jg),and time-dependent dielectric breakdown(TDDB)characteristics of the oxide,are affected by POA temperature and are closely correlated.Specifically,Dit,Jg,and inverse median lifetime of TDDB have the same trend against POA temperature,which is instructive for SiC/SiO_(2)interface quality improvement.Moreover,area dependence of TDDB characteristics for gate oxide on SiC shows different electrode areas lead to same slope of TDDB Weibull curves.

Investigation of time domain characteristics of negative capacitance FinFET by pulse-train approaches

The HfO2-based ferroelectric field effect transistors(FeFET)have been widely studied for their ability in breaking the Boltzmann limit and the potential to be applied to low-power circuits.This article systematically investigates the transient response of negative capacitance(NC)fin field-effect transistors(FinFETs)through two kinds of self-built test schemes.By comparing the results with those of conventional FinFETs,we experimentally demonstrate that the on-current of the NC FinFET is not degraded in the MHz frequency domain.Further test results in the higher frequency domain show that the on-state current of the prepared NC FinFET increases with the decreasing gate pulse width at pulse widths below 100 ns and is consistently greater(about 80%with NC NMOS)than the on-state current of the conventional transistor,indicating the great potential of the NC FET for future high-frequency applications.

Stress-induced leakage current characteristics of PMOS fabricated by a new multi-deposition multi-annealing technique with full gate last process

In the process of high-k films fabrication, a novel multi deposition multi annealing （MDMA） technique is introduced to replace simple post deposition annealing. The leakage current decreases with the increase of the post deposition annealing （PDA） times. The equivalent oxide thickness （EOT） decreases when the annealing time（s） change from 1 to 2. Furthermore, the characteristics of SILC （stress-induced leakage current） for an ultra-thin SiO2/HfO2 gate dielectric stack are studied systematically. The increase of the PDA time（s） from 1 to 2 can decrease the defect and defect generation rate in the HK layer. However, increasing the PDA times to 4 and 7 may introduce too much oxygen, therefore the type of oxygen vacancy changes.

Investigation on the passivation,band alignment,gate charge,and mobility degradation of the Ge MOSFET with a GeO/Al;O;gate stack by ozone oxidation

Ge has been an alternative channel material for the performance enhancement of complementary metal-oxide-semiconductor(CMOS)technology applications because of its high carrier mobility and superior compatibility with Si CMOS technology.The gate structure plays a key role on the electrical property.In this paper,the property of Ge MOSFET with Al_(2)O_(3)/GeO_(x)/Ge stack by ozone oxidation is reviewed.The GeO_(x)passivation mechanism by ozone oxidation and band align-ment of Al2O3/GeO_(x)/Ge stack is described.In addition,the charge distribution in the gate stack and remote Coulomb scatter-ing on carrier mobility is also presented.The surface passivation is mainly attributed to the high oxidation state of Ge.The en-ergy band alignment is well explained by the gap state theory.The charge distribution is quantitatively characterized and it is found that the gate charges make a great degradation on carrier mobility.These investigations help to provide an impressive un-derstanding and a possible instructive method to improve the performance of Ge devices.

Characterization of HfSiAlON/MoAlN PMOSFETs Fabricated by Using a Novel Gate-Last Process

We fabricate p-channel metal-oxide-semiconductor-field-effect-transistors(PMOSFETs)with a HfSiAlON/MoAlN gate stack using a novel and practical gate-last process.In the process,SiO_(2)/poly-Si is adopted as the dummy gate stack and replaced by an HfSiAlON/MoAlN gate stack after source/drain formation.Because of the high-k/metal-gate stack formation after the 1000℃source/drain ion-implant doping activation,the fabricated PMOSFET has good electrical characteristics.The device's saturation driving current is 2.71×10^(-4) A/μm(VGS=VDS=-1.5 V)and the off-state current is 2.78×10^(-9) A/μm.The subthreshold slope of 105 mV/dec(VDS=-1.5 V),drain induced barrier lowering of 80 mV/V and Vth of -0.3 V are obtained.The research indicates that the present PMOSFET could be a solution for high performance PMOSFET applications.

Multiple SiGe/Si layers epitaxy and SiGe selective etching for vertically stacked DRAM

Fifteen periods of Si/Si_(0.7)Ge_(0.3)multilayers(MLs)with various Si Ge thicknesses are grown on a 200 mm Si substrate using reduced pressure chemical vapor deposition(RPCVD).Several methods were utilized to characterize and analyze the ML structures.The high resolution transmission electron microscopy(HRTEM)results show that the ML structure with 20 nm Si_(0.7)Ge_(0.3)features the best crystal quality and no defects are observed.Stacked Si_(0.7)Ge_(0.3)ML structures etched by three different methods were carried out and compared,and the results show that they have different selectivities and morphologies.In this work,the fabrication process influences on Si/Si Ge MLs are studied and there are no significant effects on the Si layers,which are the channels in lateral gate all around field effect transistor(L-GAAFET)devices.For vertically-stacked dynamic random access memory(VS-DRAM),it is necessary to consider the dislocation caused by strain accumulation and stress release after the number of stacked layers exceeds the critical thickness.These results pave the way for the manufacture of high-performance multivertical-stacked Si nanowires,nanosheet L-GAAFETs,and DRAM devices.

AlGaN/GaN Based Diodes for Liquid Sensing

The characteristics of AlGaN/GaN Schottky diodes as polar liquid sensors are reported.Circular structures,with a gate metal diameter of 200μm,are designed and fabricated by using a optical lithography process.Ni/Au and Ti/Al/Ni/Au metals are used as the Schottky contact and the ohmic contact,respectively.The Schottky diodes exhibit large changes in reverse leakage current at a bias of?20 V in response to the surface exposed to various polar liquids,such as acetone and ethanol.The effective Schottky barrier height of the diodes is also changed with the polar liquids.The polar nature of the liquids leads to a change of surface charges,producing a change in surface potential at the semiconductor/liquid interface.The effect of the SiN_(x) passivation layer thickness on the liquid sensing is also discussed.The results demonstrate that the AlGaN/GaN heterostructures are promising for polar liquids,combustion gas,biological,and strain sensing applications.

Improved Operation Characteristics for Nonvolatile Charge-Trapping Memory Capacitors with High-κ Dielectrics and SiGe Epitaxial Substrates

A novel high-κ~ A1203/HfO2/AI203 nanolaminate charge trapping memory capacitor structure based on SiGe substrates with low interface densities is successfully fabricated and investigated. The memory capacitor exhibits excellent program-erasable characteristics. A large memory window of ~4 V, a small leakage current density of ~2 ×10-6 Acre-2 at a gate voltage of 7V, a high charge trapping density of 1.42 × 1013 cm-2 at a working vo]tage of 4-10 V and good retention characteristics are observed. Furthermore, the programming （△ VFB = 2.8 V at 10 V for 10μs） and erasing speeds （△VFB =-1.7 V at -10 V for 10μs） of the fabricated capacitor based on SiGe substrates are significantly improved as compared with counterparts reported earlier. It is concluded that the high-κ Al2O3/HfO2/Al2O3 nanolaminate charge trapping capacitor structure based on SiGe substrates is a promising candidate for future nano-scaled nonvolatile flash memory applications.

Large area graphene produced via the assistance of surface modification

We develop a novel and convenient method to prepare large area single-layer and multi-layer graphene through surface modification with oxygen plasma.The obtained large area single-layer graphene is dozens of microns wide in the lateral dimension and characterized by optical microscopy,atomic force microscopy.Raman spectroscopy show multilayer graphene has less disorder density than single-layer graphene.X-ray photoelectron spectroscopy（XPS） analysis shows that hydroxyl groups are formed on the HOPG surface during oxygen plasma pre-treatment.Hydrogen bonds develop between hydroxyl groups on HOPG surface and silanol groups on hydroxylated SiO_2/Si substrate,which facilitate the transfer process.This study may provide a potential approach to develop graphene-based devices by using the large area lithographic printing process.

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.