This paper develops the simple and accurate two-dimensional analytical models for new asymmetric double-gate fully depleted strained-Si MOSFET. The models mainly include the analytical equations of the surface potential, surface electric field and threshold voltage, which are derived by solving two dimensional Poisson equation in strained-Si layer. The models are verified by numerical simulation. Besides offering the physical insight into device physics in the model, the new structure also provides the basic designing guidance for further immunity of short channel effect and draininduced barrier-lowering of CMOS-based devices in nanometre scale.
To reduce the self-heating effect of strained Si grown on relaxed SiGe-on-insulator（SGOI） n-type metal-oxide-semiconductor field-effect transistors（nMOSFETs）,this paper proposes a novel device called double step buried oxide（BOX） SGOI,investigates its electrical and thermal characteristics,and analyzes the effect of self-heating on its electrical parameters.During the simulation of the device,a low field mobility model for strained Si MOSFETs is established and reduced thermal conductivity resulting from phonon boundary scattering is considered.A comparative study of SGOI nMOSFETs with different BOX thicknesses under channel and different channel strains has been performed.By reducing moderately the BOX thickness under the channel,the channel temperature caused by the self-heating effect can be effectively reduced.Moreover,mobility degradation,off state current and a short-channel effect such as drain induced barrier lowering can be well suppressed.Therefore,SGOI MOSFETs with a thinner BOX under the channel can improve the overall performance and long-term reliability efficiently.
Based on the exact resultant solution of two-dimensional Poisson＇s equation, the novel two-dimensional models, which include surface potential, threshold voltage, subthreshold current and subthreshold swing, have been developed for gate stack symmetrical double-gate strained-Si MOSFETs. The models are verified by numerical simulation. Besides offering the physical insight into device physics, the model provides the basic designing guidance of further immunity of short channel effect of complementary metal-oxide-semiconductor （CMOS）-based device in a nanoscale regime.
Based on the exact resultant solution of two-dimensional Poisson＇s equation in strained Si and Si1-xCex layer, a simple and accurate two-dimensional.analytical model including surface channel potential, surface channel electric field, threshold voltage and subthreshold swing for fully depleted gate stack strained Si on silicon-germanium-on-insulator （SGOI） MOSFETs has been developed. The results show that this novel structure can suppress the short channel effects （SCE）, the drain-induced barrier-lowering （DIBL） and improve the subthreshold performance in nanoelectronics application. The model is verified by numerical simulation. The model provides the basic designing guidance of gate stack strained Si on SGOI MOSFETs.
HfO2 films are deposited by atomic layer deposition（ALD） using tetrakis ethylmethylamino hafnium（TEMAH） as the hafnium precursor,while O3 or H2O is used as the oxygen precursor.After annealing at 500℃ in nitrogen,the thickness of Ge oxide＇s interfacial layer decreases,and the presence of GeO is observed at the H2 O-based HfO2 interface due to GeO volatilization,while it is not observed for the O3-based HfO2.The difference is attributed to the residue hydroxyl groups or H2 O molecules in H2 O-based HfO2 hydrolyzing GeO2 and forming GeO,whereas GeO is only formed by the typical reaction mechanism between GeO2 and the Ge substrate for O3-based HfO2 after annealing.The volatilization of GeO deteriorates the characteristics of the high-κ films after annealing,which has effects on the variation of valence band offset and the C-V characteristics of HfO2 /Ge after annealing.The results are confirmed by X-ray photoelectron spectroscopy（XPS） and electrical measurements.
The photo-carrier density in the depletion region of the GaN-based p-i-n ultraviolet(UV) detector is calculated by solving the photo-carrier continuity equation,and the photo-carrier screening electric field is calculated according to Poisson's equation.Using the numerical calculation method,a novel model of photo-carrier screening effect is presented.Then the influence of photo-carrier screening effect on the distribution of photo-carrier density in the depletion region of p-i-n detector is discussed.The influence of incident power,bias voltage and carrier life time on the photo-carrier screening effect is also analyzed.It is concluded that the influence of photo-carrier screening effect on the performance of GaN-based p-i-n UV detector is non-monotone,the maximum of carrier drift velocity and the minimum of response time can be realized by adjusting the applied voltage.Besides,the incident light duration has strong impact on the photo-carrier screening effect.
GAO Bo,LIU HongXia,KUANG QianWei,ZHOU Wen & CAO Lei School of Microelectronics,Xidian University,Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices,Xi’an 710071,China
After constructing a stress and strain model, the valence bands of in-plane biaxial tensile strained Si is calculated by k·p method. In the paper we calculate the accurate anisotropy valance bands and the splitting energy between light and heavy hole bands. The results show that the valance bands are highly distorted, and the anisotropy is more obvious. To obtain the density of states （DOS） effective mass, which is a very important parameter for device modeling, a DOS effective mass model of biaxial tensile strained Si is constructed based on the valance band calculation. This model can be directly used in the device model of metal-oxide semiconductor field effect transistor （MOSFET）. It also a provides valuable reference for biaxial tensile strained silicon MOSFET design.
A low-voltage triggering silicon-controlled rectifier（LVTSCR）,for its high efficiency and low parasitic parameters,has many advantages in ESD protection,especially in ultra-deep sub-micron（UDSM） IC and high frequency applications.In this paper,the impact factors of the snapback characteristics of a LVTSCR and the configuring modes are analyzed and evaluated in detail.These parameters include anode series resistance,gate voltage,structure and size of devices.In addition,a double-trench LVTSCR is presented that can increase the hold-on voltage effectively and offers easy adjustment.Also,its snapback characteristics can obey the ESD design window rule very well.The strategy of ESD protection in a RFIC using a LVTSCR is discussed at the end of the paper.
On the basis of the exact resultant solution of two dimensional Poisson’s equations,a new accurate two-dimensional analytical model comprising surface channel potentials,a surface channel electric field and a threshold voltage for fully depleted asymmetrical dual material gate double-gate strained-Si MOSFETs is successfully developed. The model shows its validity by good agreement with the simulated results from a two-dimensional numerical simulator.Besides offering a physical insight into device physics,the model provides basic design guidance for fully depleted asymmetrical dual material gate double-gate strained-Si MOSFETs.
For the first time,a simple and accurate two-dimensional analytical model for the surface potential variation along the channel in fully depleted dual-material gate strained-Si-on-insulator（DMG SSOI） MOSFETs is developed.We investigate the improved short channel effect（SCE）,hot carrier effect（HCE）,drain-induced barrier-lowering（DIBL） and carrier transport efficiency for the novel structure MOSFET.The analytical model takes into account the effects of different metal gate lengths,work functions,the drain bias and Ge mole fraction in the relaxed SiGe buffer.The surface potential in the channel region exhibits a step potential,which can suppress SCE,HCE and DIBL.Also,strained-Si and SOI structure can improve the carrier transport efficiency,with strained-Si being particularly effective.Further, the threshold voltage model correctly predicts a＂rollup＂in threshold voltage with decreasing channel length ratios or Ge mole fraction in the relaxed SiGe buffer.The validity of the two-dimensional analytical model is verified using numerical simulations.
