搭桥晶粒多晶硅薄膜晶体管栅交流电应力下的退化行为与退化机制研究

本文主要研究了搭桥晶粒(BG)多晶硅薄膜晶体管(TFT)在栅交流电应力下的退化行为和退化机制。在栅交流应力下,动态热载流子效应主导了器件的退化。器件退化只与栅脉冲下降沿有关。越快的下降沿带来越大的动态热载流子退化。比起普通多晶硅TFT,BG多晶硅TFT的热载流子退化大幅度减弱。通过选择性的掺杂注入BG线,沟道中形成的PN结在反向偏置时可以有效分担栅交流电应力带来的电压差,从而减弱动态热载子退化。辅以瞬态模拟结果,栅交流电应力下的退化机制被阐明。所有的测试结果都表明这种高性能高可靠性的BG多晶硅TFT在片上系统应用中具有很大的应用前景。     

LDD结构参数对多晶硅薄膜晶体管热载流子退化的影响

基于Tsuprem4和Medici模拟软件,研究了LDD结构对多晶硅薄膜晶体管热载流子退化的影响.计算结果表明当栅氧层厚度tox=0.07 μm时,碰撞离化产生率和热电子注入电流峰值将达到最大,扩展区掺杂浓度增加,使沟道中横向电场和碰撞离化产生率的峰值分布区域向着栅电极的方向移动,即在应力作用下,热载流子退化的区域向着栅电极的方向漂移.     

耗尽区调制对氢化MILC Poly-Si TFT热产生漏电的影响

研究了热载流子应力下耗尽区调制效应对氢化金属诱导横向结晶多晶硅薄膜晶体管热产生漏电的影响.从理论上论证了热载流子应力下氢化金属诱导横向结晶多晶硅薄膜晶体管热产生漏电中的耗尽区调制效应的存在.并利用正、反向测量模式,从实验上进一步确认这种效应对氢化金属诱导横向结晶多晶硅薄膜晶体管热产生漏电的影响.发现在热载流子应力下,正、反向测量模式时,氢化金属诱导横向结晶多晶硅薄膜晶体管热产生漏电均随应力时间的增加而减小.但由于漏极和源极附近沟道区的表面势受热空穴注入影响的程度不同,热载流子应力下,正、反向测量模式的热产生漏电减小程度不同.理解热载流子应力下耗尽区调制效应对氢化金属诱导横向结晶多晶硅薄膜晶体管热产生漏电的影响,有助于成功设计电路.     

超深亚微米LDD nMOSFET中的非幸运电子模型效应

通过对采用0.18μm CMOS工艺制造的两组不同沟道长度和栅氧厚度的LDD器件电应力退化实验发现,短沟薄栅氧LDD nMOSFET(Lg=0.18μm,Tox=3.2nm)在沟道热载流子(CHC)应力下的器件寿命比在漏雪崩热载流子(DAHC)应力下的器件寿命要短,这与通常认为的DAHC应力(最大衬底电流应力)下器件退化最严重的理论不一致.因此,这种热载流子应力导致的器件退化机理不能用幸运电子模型(LEM)的框架理论来解释.认为这种"非幸运电子模型效应"是由于最大碰撞电离区附近具有高能量的沟道热电子,在Si-SiO2界面产生界面陷阱(界面态)的区域,由Si-SiO2界面的栅和漏的重叠区移至沟道与LDD区的交界处以及更趋于沟道界面的运动引起的.     

超深亚微米LDD nMOSFET中的非幸运电子模型效应

通过对采用0.18μm CMOS工艺制造的两组不同沟道长度和栅氧厚度的LDD器件电应力退化实验发现，短沟薄栅氧LDD nMOSFET（Lg=0.18μm，Tox=3.2nm）在沟道热载流子(CHC)应力下的器件寿命比在漏雪崩热载流子（DAHC）应力下的器件寿命要短，这与通常认为的DAHC应力（最大衬底电流应力）下器件退化最严重的理论不一致．因此，这种热载流子应力导致的器件退化机理不能用幸运电子模型（LEM）的框架理论来解释．认为这种“非幸运电子模型效应”是由于最大碰撞电离区附近具有高能量的沟道热电子，在Si-SiO2界面产生界面陷阱(界面态)的区域，由Si-SiO2界面的栅和漏的重叠区移至沟道与LDD区的交界处以及更趋于沟道界面的运动引起的．     

一种用于提取LDD结构n-MOSFET热载流子应力下界面陷阱产生的改进方法

提出了一种新的基于电荷泵技术和直流电流法的改进方法,用于提取LDD n-MOSFET沟道区与漏区的界面陷阱产生.这种方法对于初始样品以及热载流子应力退化后的样品都适用.采用这种方法可以准确地确定界面陷阱在沟道区与漏区的产生,从而有利于更深入地研究LDD结构器件的退化机制.     

一种用于提取LDD结构n-MOSFET热载流子应力下界面陷阱产生的改进方法

提出了一种新的基于电荷泵技术和直流电流法的改进方法,用于提取LDDn MOSFET沟道区与漏区的界面陷阱产生.这种方法对于初始样品以及热载流子应力退化后的样品都适用.采用这种方法可以准确地确定界面陷阱在沟道区与漏区的产生,从而有利于更深入地研究LDD结构器件的退化机制.     

不同沟道长度对n沟MOSFET退化特性的影响

研究不同沟道长度n 沟道MOS场效应晶体管的热载流子效应对其退化特性的影响.实验结果表明,随着器件沟道长度的减小,其跨导退化明显加快,特别是当沟道长度小于1mm时更是如此.这些结果可以用热载流子注入后界面态密度增加来解释.     

Vg=Vd/2应力模式下宽度变窄对HALO-pMOSFETs退化的影响

讨论了最差应力模式下(Vg=Vd/2)宽沟和窄沟器件的退化特性.随着器件沟道宽度降低可以观察到宽度增强的器件退化.不同沟道宽度pMOSFETs的主要退化机制是界面态产生.沟道增强的器件退化是由于沟道宽度增强的碰撞电离率.通过分析电流拥挤效应,阈值电压随沟道宽度的变化,速度饱和区特征长度的变化和HALO结构串联阻抗这些可能原因,得出沟道宽度增强的热载流子退化是由宽度降低导致器件阈值电压和串联阻抗降低的共同作用引起的.     

搭桥晶粒多晶硅薄膜晶体管直流电应力下的退化行为与退化机制研究

研究了搭桥晶粒(BG)多晶硅薄膜晶体管(TFT)在直流电应力下的退化行为和退化机制。与普通多晶硅TFT相比,BG多晶硅TFT展现出更好的直流应力可靠性。主要体现在BG多晶硅TFT拥有更好的直流负偏压温度不稳定性(NBTI)可靠性,更好的直流自加热(SH)可靠性,更好的直流热载流子(HC)可靠性。有源沟道区的BG结构是上述直流应力可靠性提高的主要原因。更好的NBTI的可靠性主要源于沟道内的硼氢键的形成;更好的SH可靠性主要源于在沟道长度方向上更快的焦耳热扩散率;更好的HC可靠性主要源于漏端横向电场(Ex)的减弱。所有的测试结果都表明,这种高性能高可靠性的BG多晶硅TFT在片上系统中具有很大的应用前景。     

On the mechanism for interface trap generation in MOS transistorsdue to channel hot carrier stressing

The classical concept and theory suggest that the degradation of MOS transistors is caused by interface trap generation resulting from “hot carrier injection.” We report three new experiments that use the deuterium isotope effect to probe the mechanism for interface trap generation in n-MOS transistors in the presence of hot hole and electron injection. These experiments show clearly that hot carrier injection into the gate oxide exhibits essentially no isotope effect, whereas channel hot electrons at the interface exhibit a large isotope effect. This leads to the conclusion that channel hot electrons, not carriers injected into the gate oxide, are primarily responsible for interface trap generation for standard hot carrier stressing     

Numerical investigation of self-heating effects of oxide-confined vertical-cavity surface-emitting lasers

We present a comprehensive numerical model to simulate self-heating effects of oxide-confined vertical-cavity surface-emitting lasers (VCSELs) under continuous-wave operation. The model self-consistently accounts for the close interaction between optical, electrical, and thermal processes in VCSELs. In particular, hot carriers and nonequilibrium optical phonons in the quantum wells are modeled by solving a carrier energy balance equation and an optical phonon rate equation. Our numerical simulations reveal that they are responsible for aggravated thermal rollovers in VCSELs' L-I characteristics. Detailed comparisons are made and good agreement is obtained between simulations and experiments for the L-I-V and lasing wavelength characteristics of VCSELs with varying oxide aperture size. Various mechanisms that result in the L-I thermal rollover behavior are also investigated with the aid of simulations.     

Low-level gate current injections in flash memories initiated byminority carrier collection action of floating terminals

An unintentional channel hot carrier injection phenomenon is reported for flash memory cells. The injection occurs near the source metallurgical junction during electrical erase and is caused by subthreshold leakage current between source and floating drains. This mechanism is initiated by a minority carrier population (electrons) which is generated by impact ionization around the source junction and later collected by the floating drains. Subsequently, when the floating gate potential approaches threshold voltage, these collected electrons drift from the drain toward the source. When they reach the source junction depletion region, they experience carrier multiplications and some hot carriers are injected onto the floating gate. The injected carriers can be either hot holes or hot electrons depending on the magnitude of the floating gate potential. This mechanism affects the final threshold voltage distribution of flash memories, especially when the electric field across the tunnel oxide is low     

Electrical and optical analyses of trapping phenomenon with temperature dependence of organic device

Carrier mechanism in actual organic devices is not simple, owing to the dielectric nature of active organic semiconductor layers, the complexity of the organic device interface, carrier trapping effects by stress biasing, and others. By coupling the conventional electrical measurement, e.g., current–voltage, capacitance–voltage and capacitance-frequency measurements, with optical charge modulation spectroscopy (CMS) measurement, we studied the hysteresis behavior and the temperature dependence of indium tin oxide/polyimide/6,13-Bis(triisopropylsilylethynyl)pentacene(TIPS-pentacene)/Au diodes to understand the effect of carrier trapping caused by injected carriers. The coupled electrical and optical measurements were very helpful to clarify carrier injection that was followed by carrier trapping in the diode, in terms of hysteresis behavior. CMS measurement was used to observe energetic states of carriers in TIPS-pentacene double-layer diode. Finally, the carrier mechanism in organic diodes was discussed by analyzing the diodes as a Maxwell-Wagner effect element.     

Demonstration of a hot‐carrier photovoltaic cell

We demonstrate a new hot‐carrier photovoltaic cell based on the resonant tunnelling of hot electrons from a narrow‐band‐gap semiconductor to a wider‐band‐gap semiconductor. Hot electrons are photogenerated at a variety of wavelengths in a GaAs absorber followed by resonant tunnelling through a double‐barrier quantum well into an AlGaAs collector, forming an energy‐selective interface in the centre of the device. We show theoretically the presence of a tunnel current from the absorber to the collector under illumination, offering a method to extract carriers from a hot‐electron distribution at zero bias. We experimentally demonstrate a hot‐carrier photovoltaic cell based on this concept. Two features of its measured current–voltage characteristic, namely the peak to valley current ratio and the current peak voltage, are shown to vary with the wavelength of illumination in a way that clearly demonstrates hot‐carrier extraction. Copyright © 2013 John Wiley & Sons, Ltd.     

Degradation of double-gate polycrystalline silicon TFTs due to hot carrier stress

Degradation phenomena due to hot carrier stress conditions were investigated in double-gate polysilicon thin film transistors fabricated by sequential lateral solidification (SLS). We varied the hot carrier stress conditions at the front gate channel by applying various voltages at the back-gate. Thus, we investigated the device electrical performance under such stress regimes. As a conclusion, we demonstrate that severe degradation phenomena may occur at the back polysilicon interface depending on the back-gate voltage during stress. The nature of these phenomena becomes evident when the back-gate bias is such that the back interface is coupled or decoupled from the front gate electrical characteristics.     

Nonlinear gain coefficients in semiconductor lasers: effects ofcarrier heating

Nonlinear gain coefficients due to the effects of carrier heating are derived from the rate equations of carrier energy transfer in semiconductor lasers. We find that, in the modulation responses of semiconductor lasers, stimulated recombination heating will affect the resonant frequency and damping rate in a same form as the effects of spectral hole burning, while free carrier absorption heating will only affect the damping rate. The effects of injection heating and nonstimulated recombination heating are also discussed. The carrier energy relaxation time is calculated from first principles by considering the interactions between carriers and polar optical phonons, deformation potential optical phonons, deformation potential acoustic phonons, piezoelectric acoustic phonons. At the same time, the hot phonon effects associated with the optical phonons are evaluated because their negligible group velocity and finite decay time. We show that the carrier-polar longitudinal optical phonon interaction is the major channel of carrier energy relaxation processes for both electron and holes. We also point out the importance of the longitudinal optical phonon lifetime in evaluating the carrier energy relaxation time. Neglecting the finite decay time of longitudinal optical phonons will significantly underestimate the carrier energy relaxation time, this not only contradicts the experimental results but also severely underestimates the nonlinear gain coefficients due to carrier heating. The effects of spectral hole burning, stimulated recombination heating, and free carrier absorption heating on limiting the modulation bandwidth in semiconductor lasers are also discussed     

Pulsed stress reliability investigations of schottky diodes and HBTS

Experimental results from stressing Schottky diodes and HBTS employing TLP (Transmission Line Pulses) with 100ns duration time and ESD pulses following the Human Body Model are compared. Based on optical and electrical characterisation the same failure mechanisms seem to occur indicating the strong degree of relationship between these two methods. Device failures are explained by thermally activated interface and bulk reactions, field enhanced material transport and hot charge carrier effects.     

新型槽栅nMOSFET热载流子效应的模拟研究

应用二维器件仿真程序 PISCES- ,对槽栅结构和平面结构器件的特性进行了模拟比较 ,讨论了槽栅结构 MOSFET的沟道电场特征及其对热载流子效应的影响。槽栅结构对抑制短沟道效应和抗热载流子效应是十分有利的 ,而此种结构对热载流子的敏感 ,使器件的亚阈值特性、输出特性变化较大