FN应力下超薄栅N-MOSFET失效的统计特征及寿命预测

通过对不同氧化层厚度的N-MOSFET在各种条件下加速寿命实验的研究,发现栅电压漂移符合Weibull分布.Weibull分布统计分析表明,5.0、7.0和9.0nm器件在27和105C下本征失效的形状因子相同,即本征失效的失效机制在高低温度下相同.非本征失效的比例随温度升高而增大.在此基础上得出平均寿命(t50)与加速电场E成指数关系,进而提出了器件的寿命预测方法.此方法可预测超薄栅N-MOSFET在FN应力下的寿命.     

GaN HEMT器件寿命预测方法及理论研究

GaN HEMT器件以其优良的性能被广泛使用于各种领域的电子设备中。由于其经常被使用于高频、高温和高辐射的环境中,过高的环境应力会加速器件的损伤。当损伤达到一定程度时,就会引起器件失效,甚至导致整个系统失效。因此外加应力下GaN HEMT器件寿命成为了当前研究的热点。本文基于不同机构对GaN HEMT器件的三温度直流测试结果,运用多元线性回归法和图估计法对GaN HEMT器件在正常使用温度下的寿命进行预测。预测结果表明,GaN HEMT器件在正常使用时,器件沟道温度为150℃的情况下,中位寿命大于107小时;在累积失效概率达23%时,3.6mm栅宽器件与1.25mm栅宽器件的正常工作时间均为5.04×105小时,累积失效概率在23%以上时,1.25mm栅宽器件的寿命明显较3.6mm栅宽器件长。     

Weibull分布下基于MAM的白光OLED寿命预测

为了得到白光有机发光二极管(OLED)寿命信息,降低试验成本,开展了三组恒定电流应力加速寿命试验。采用Weibull函数描述其寿命分布,基于图分析法(MAM)和MATLAB绘制的Weibull概率双坐标纸,描点作图并估计形状参数和尺度参数,实现了白光OLED的寿命预测。数值结果表明,白光OLED样品在各加速应力下失效机理保持不变,加速模型满足逆幂定律,精确计算的加速参数使得OLED寿命快速估算成为可能。     

Si IGBT和SiC MOSFET分立器件封装可靠性对比

为了明确SiC金属-氧化物-半导体场效应晶体管(MOSFET)与Si绝缘栅双极型晶体管(IGBT)寿命差异的原因，在相同结温条件下对上述两种分立器件进行功率循环试验。试验结果表明，SiC MOSFET的寿命大于Si IGBT的寿命。若将两组试验负载电流等效一致，则SiC MOSFET的寿命约为Si IGBT的1/4。为了揭示寿命差异的根本原因，即失效机理的探究，建立了两种器件电-热-力多物理场有限元模型并在功率循环试验条件下进行仿真，结果表明造成寿命差异的原因是Si、SiC材料与铝材料之间的热膨胀系数差异不同，导致器件在功率循环中受到循环热应力时产生的塑性应变不同。研究结果为提高SiC MOSFET的寿命提供了理论参考。     

中功率微波砷化镓场效应晶体管可靠性研究

对WC55中功率微波砷化镓场效应晶体管进行的高温固定偏置加速寿命试验研究表明:该器件在70℃环境温度下的MTTF达7.3×10~5小时以上,已接近国外类似器件的可靠性水平;同时还揭示出器件早期失效模式有栅源烧毁、饱和漏电流下降及栅-源击穿电压降低等三种.根据加速寿命试验结果,提出了器件通过室温250小时LTPD为20%的工作寿命试验和500小时LTPD为15%的工作寿命试验的两种最佳筛选条件.室温工作寿命试验结果证明所提出的筛选条件是合理的.     

SiC MOSFET单粒子漏电退化的影响因素

高压功率器件是未来航天器进一步发展的关键,对SiC金属-氧化物-半导体场效应晶体管(MOSFET)等高压大功率器件的抗辐射研究亟待突破。在不同偏置条件下对器件的单粒子效应(SEE)进行实验,结果表明,SiC MOSFET单粒子漏电退化效应与漏源电压、离子注量以及反向栅源电压呈正相关。为进一步研究SiC MOSFET单粒子效应机理,结合实验数据进行TCAD仿真,发现器件发生单粒子效应时存在两种失效模式,第一种失效模式与Si基MOSFET类似,而第二种失效模式与SiC器件的特有结构密切相关,容易形成更高的分布电压,导致栅氧化层烧毁失效。该结果为抗辐照加固器件的研究提供了理论支撑。     

基于加速因子不变原则的失效机理一致性检验

针对加速试验中产品的失效机理是否发生改变的问题,基于加速因子不变原则,研究了工程上应用较为广泛的Weibull寿命分布失效机理一致性的检验方法.将Weibull分布转化为I型极值分布,进而研究极值分布尺度参数的统计检验方法,并采用尺度参数的Ansari-Bradley方法进行检验.结合Arrhenius加速模型,基于最小二乘法估计、回归系数的性质构造t统计量,实现对加速因子与分布参数的统计检验,判别失效机理发生改变的应力.仿真模型验证了所提检验方法的有效性.     

NMOS管热载流子衰退效应评价模型及寿命预测方法研究

热载流子是器件可靠性研究的热点之一.特别对于亚微米器件,热载流子失效是器件失效的一个最主要方面.通过对这种失效机理及其失效模型的研究,为设计和工艺提供帮助,从而有效降低由热载流子引起的电路失效,提高电路可靠性.本文主要针对几种典型工艺的栅氧厚度(例如:Tox分别为150 (A)、200 (A)、250 (A))的NMOSFET进行加速应力实验,提取寿命模型的相关参数,估算这些器件在正常工作条件下的寿命值,对亚微米工艺器件寿命进行快速评价.     

GaN HEMT微波功率管直流和射频加速寿命试验

分别选用南京电子器件研究所研制的1.25mm栅宽GaN HEMT和12mm栅宽GaN功率管,对小栅宽器件进行三温直流加速寿命试验,评估其直流工作可靠性,试验结果表明该器件在125℃沟道温度条件下工作的失效率为1.86×10-9/h;对大栅宽器件进行脉冲射频加速寿命试验,评估其射频工作可靠性,试验结果表明该器件在125℃沟道温度条件下工作的失效率小于1.02×10-7/h。     

高压LDMOS准饱和效应研究

借助于SILVACO TCAD仿真工具,研究了高压LDMOS电流准饱和效应(Quasi-saturation effect)的形成原因。通过分析不同栅极电压下漂移区的耗尽情况以及沟道与漂移区电势、电场和载流子漂移速度的分布变化,认为当栅压较低时,LDMOS的本征MOSFET工作在饱和区,栅压对源漏电流的钳制明显,此时沟道载流子速度饱和;而在大栅压下,随着沟道导电能力的增加以及漂移区两端承载的电压的增大,本征MOSFET两端压降迅速降低,器件不能稳定地工作在饱和区而进入线性工作区,此时沟道中的载流子速度不饱和。LDMOS器件的源漏电流的增大主要受漂移区影响,栅压逐渐失去对器件电流的控制,此时增大栅压LDMOS器件的源漏电流变化很少,形成源漏电流的准饱和效应。最后,从器件工作过程对电流与栅压的关系进行了理论分析,并从理论结果对电流准饱和效应进行了深入分析。     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

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正Communications—VLSI Researches and industries of telecommunications have been growing rapidly in the last 20 years and will keep their high growing pace in the next decade.The involved researches and developments cover mobile communications,highway and last-mile broadband communication,domain specific communications,and emerging D2D M2M communications.Radio communication steps into its