低能电子束照射集成电路芯片时的静态电容衬度分析

在研究低能电子束照射绝缘物时在二次电子返回特性的基础上,通过绝缘物表面照射微区和衬底之间的有效电容,获得了表面电位和二次电子信号电流在表面电荷积累过渡过程中随照射条件的变化关系,建立了电子束照射覆盖有绝缘膜的IC芯片时形成静态电容衬度的理论模型.从理论上分析了电子束照射条件和芯片内部形貌、材料参数对静态电容衬度的影响,解释了在扫描电镜实验中的最大衬度现象及其对应的最佳电子照射条件.     

具有埋层结构电介质样品扫描电镜二次电子特性

采用较为全面的考虑电子散射、俘获、输运和自洽场等过程的数值模型,阐明了具有埋层结构电介质样品的扫描电镜检测机理及二次电子电流的动态特性。模拟结果表明,被沟槽界面俘获的电荷会影响空间电场分布,从而影响二次电子特性。随着电子束照射,样品表面沿着深度方向的电场强度增强,更多的二次电子返回表面,从而产生图像衬度。图像衬度随电子束能量的变化呈现极大值,而随电子束电流的增大而增大,模拟结果与实验结果基本一致。     

绝缘膜负带电时的表面局部电场与二次电子返回特性

为分析IC多层版图扫描电镜(SEM)对准检测所利用的负带电成像原理,采用Mott弹性散射截面和修正的Bethe非弹性碰撞公式,对点照射入射电子在绝缘膜中的散射过程进行了Monte Carlo模拟,得到负带电绝缘物表面的局部电位分布.在此基础上计算了二次电子从表面出射后在局部场作用下的运动轨迹,获得了SEM像的二次电子信号电流.结果表明,在弱负带电条件下,照射点处表面电位越低,返回表面的二次电子就越多,对应的二次电子信号电流越弱.此结果与SEM实验中图像亮度随照射时间的变化规律相符.     

绝缘膜负带电时的表面局部电场与二次电子返回特性

为分析IC多层版图扫描电镜(SEM)对准检测所利用的负带电成像原理,采用Mott弹性散射截面和修正的Bethe非弹性碰撞公式,对点照射入射电子在绝缘膜中的散射过程进行了Monte Carlo模拟,得到负带电绝缘物表面的局部电位分布.在此基础上计算了二次电子从表面出射后在局部场作用下的运动轨迹,获得了SEM像的二次电子信号电流.结果表明,在弱负带电条件下,照射点处表面电位越低,返回表面的二次电子就越多,对应的二次电子信号电流越弱.此结果与SEM实验中图像亮度随照射时间的变化规律相符     

扫描电镜电压衬度法的应用

应用扫描电子显微镜电压衬度法观察分析半导体器件样品,对它进行失效分析或观察它的工作状态等,都有很明显的效果.电压衬度图象是在扫描电镜二次电子图象的基础上形成的,它通过对样品室中的半导体样品的某一部分施加电压,以便在样品的二次电子图象中的相应部位获得反差.由于所施加的电压会在样品表面形成一个小的局部电场,这个小电场对样品该部分的二次电子发射会起抑制作用,因此当电子束     

低能电子束照射电介质样品的二次电子特性

为阐明低能电子束照射下电介质样品的二次电子电流及产额的动态特性,将蒙特卡洛法和有限差分法相结合,建立了较为准确的电子散射、俘获、输运和自洽场等过程的数值计算模型;采用一个改进二次电子检测实验平台,准确测量了二次电子电流.模拟和实验结果表明,相对于电子束脉冲照射模式,电子束连续照射会导致二次电子产额明显降低.在连续照射模式下,随着电子束照射,二次电子电流和产额逐渐减小至一个稳定值.二次电子产额受入射电子束电流的影响较小,但随样品厚度的增大而增大.本文结果为提高扫描电镜成像质量、降低带电效应提供了理论指导,而且提供了依据二次电子特性研究样品参数的新思路.     

低能电子束照射电介质样品的二次电子特性简

 为阐明低能电子束照射下电介质样品的二次电子电流及产额的动态特性,将蒙特卡洛法和有限差分法相结合,建立了较为准确的电子散射、俘获、输运和自洽场等过程的数值计算模型;采用一个改进二次电子检测实验平台,准确测量了二次电子电流.模拟和实验结果表明,相对于电子束脉冲照射模式,电子束连续照射会导致二次电子产额明显降低.在连续照射模式下,随着电子束照射,二次电子电流和产额逐渐减小至一个稳定值.二次电子产额受入射电子束电流的影响较小,但随样品厚度的增大而增大.本文结果为提高扫描电镜成像质量、降低带电效应提供了理论指导,而且提供了依据二次电子特性研究样品参数的新思路.     

动态电子束探针检测技术在亚微米和深亚微米IC失效分析中的应用研究

对扫描电子显微镜静态/动态/电容耦合电压衬度像、电子束感生电流像、电阻衬度像在亚微米和深亚微米超大规模集成电路中的成像方法和成像特点进行了研究,对各种分析技术在失效分析中的应用进行了深入的探讨,为电子束探针检测技术在亚微米和深亚微米集成电路故障定位和失效机理分析中的应用提供了理论基础和实践依据.     

高分辨二次电子像中的成份衬度

高分辨二次电子像中的成份衬度徐军陈文雄张会珍（北京大学电镜实验室，北京１００８７１）在传统的扫描电子显微学的概念中，二次电子像中包含的是形貌衬度，而背散射电子像中包含的是成份衬度。但实际上二次电子的产额是和样品的成份有关的，不过样品表面极易玷污，样品...     

Pt/C催化剂颗粒体系SEM成像的计算机模拟

Pt纳米颗粒/C基底体系是典型的纳米催化剂应用体系,本文采用蒙特卡罗方法模拟了该体系的扫描电子显微镜成像。给出了不同尺度的Pt纳米颗粒在C基底中不同深度下二次电子和背散射电子成像的衬度。计算结果显示：(1)在PI／C衬度的形成中,材料的原子序数衬度而不是形貌衬度起了主要作用：(2)只有分布在C基底表面或者表面以下很浅深度内(大约三倍颗粒直径)的Pt颗粒才可以在二次电子信号中被观察到,而背散射信号中则可以观察到更深的Pt颗粒(大约五倍颗粒直径);(3)当颗粒尺度小于几十纳米时。其二次电子信号衬度与通常微米尺度的情形有很大不同,最亮处位于颗粒的中央而不是边缘,且随着颗粒尺度的降低。二次电子产额绝对值也相应降低。     

Quantitative analysis of static capacitance contrast in scanning electron microscopy

A one-dimensional model is proposed for analysing static capacitance contrast (SCC) in scanning electron microscopy. For the large-scale integrated specimen covered by an insulating thin film, the imaging signal is calculated considering the redistribution of secondary electrons (SEs) and the charging process of the equivalent effective capacitance between the irradiation point and substrate. The calculated SCC as a function of the irradiation charge density is in good agreement with the experimental SCC. It is confirmed that the SCC arises from the redistribution of SEs and the difference in the effective capacitance of irradiation points under the condition of positive charging.     

Directed assembly of nano-particles with the help of charge patterns created with scanning electron microscope

Directed assembly of nano-particles by charged patterns on an insulator surface is a method that has been applied before, but the creation of the charged patterns was a time consuming process in previous work. Here a scanning electron microscope (SEM) is used to speed up the charging process. The main challenges do not lie in focusing the electron beam but in storing the charge in the insulator in a highly localized way. The present paper shows the first promising results of directing nano-particles to predefined charge patterns on insulators, where the charge is created with a finely focused electron beam. The nano-particles (palladium) are created in an Ar atmosphere with a glowing wire generator (GWG). A narrow size interval of charged particles is selected by a mobility analyzer. From gas suspension they are deposited onto the charge patterns.     

Model of the behavior of MOS structures under ionizing irradiation

A quantitative model describing the behavior of MOS structures under ionizing irradiation is developed. The model is based on the capture of holes by hydrogen-containing traps. Some traps are charged and thus form a positive space charge in the insulator. The other traps decay to release positive hydrogen ions. These ions migrate in the insulator electric field to the insulator-semiconductor interface, where they depassivate surface states. The charging of surface states both under irradiation and during measurement of the threshold voltage is taken into account.     

Failure analysis method by using different wavelengths lasers and its application

We succeeded in an accurate detection for failure locations on a silicon semiconductor device (hereafter called “IC”) by applying the failure analysis method in which two kinds of laser beams having different wavelengths are simultaneously irradiated on a surface of IC. Short wavelength laser beam (λ=1083nm) causes potential changes in an internal circuit of IC due to generating many electron-hole pairs in the semiconductor. On the other hand, long wavelength laser beam (λ=1360 run) causes an easy operation of parasitic bipolar elements due to increasing temperature of IC by irradiation heat. By combining these effects of two laser beams, the accurate detection of latch-up locations on internal circuits of IC (has been recognized to be difficult up to now) has come possible.     

大功率AlInGaP红光LED的电子束辐照效应

通过实验研究和蒙特卡罗模拟方法,针对大功率AlInGaP红光LED开展了电子束辐照效应方面的研究。运用CASINO程序详细分析了电子束在LED芯片中的射程和能量损失分布,利用电子束辐照设备研究并总结了大功率AlInGaP红光LED在不同能量和剂量的电子束辐照条件下的光通量和光功率的变化表现为剂量效应。结果表明:在带电粒子辐照过程中,入射粒子与材料内部原子会发生弹性碰撞及电离作用,在AlInGaP材料内部引发结构缺陷形成色心。     

Analysis of thermal impedance for conventional and beam lead IC chips

The thermal impedance of conventional and beam lead IC packages is evaluated from the partial differential equations, which govern the temperature and heat flow within the chip and substrate, and transmission line analogy. The mounting and the geometry dependance of the thermal impedance for various heat sink and chip sizes are presented for both beam lead and conventional IC packages. The variation of thermal impedance with the number of leads and the various Ceramic sizes is shown for the beam lead IC chip.The lumped and the distributed heat sources have been considered for the different mounting structures.     

Neutron irradiation of insulated gate field effect transistors

Insulated gate field effect transistors and polysilicon-gated capacitors were irradiated with fast (10 keV <E < 2 MeV) neutrons. As expected, damage to the bulk silicon was detected as a degradation in the minority carrier lifetime. Optically assisted electron injection was employed for the first time to examine neutral electron trap and fixed positive charge generation in the gate insulator of the devices. While fixed positive charge densities of ≤6 x 10¹⁰ cm⁻² were detected, little or no neutral electron trap generation was observed. The small density of coulombic defects observed in the insulator could be accounted for fully by the known flux of gamma rays associated with the neutron irradiation process. This indicates that fast neutrons passing through a thin gate oxide do not produce significant amounts of damage in the oxide. Somewhat surprisingly, it was found that 1.5 keV X-rays created similar lifetime degradation effects in the bulk silicon, as did fast neutrons, even though this photon energy is not believed to be capable of producing bulk damage in the form of atom displacement in either the semiconductor or the insulator. The minority carrier lifetime of the silicon could be restored to initial values following either neutron or x-ray exposure by annealing in H₂ for 30 min at 400° C.     

The charge accumulation in an insulator and the states at interfaces of silicon-on-insulator structures as a result of irradiation with electrons and gamma-ray photons

The accumulation of charge in an insulator and the states at interfaces in silicon-on-insulator structures irradiated with 2.5-MeV electrons and 662-keV gamma-ray photons were studied. It was found that an additional positive charge appears in the buried insulator of the structures as a result of irradiation. The concentration of hole traps generated by radiation in the oxide is higher at the boundary with substrate than at the bonding interface between a split-off silicon layer and oxide. It is shown that the presence of even a weak built-in field in the structures (F?5×10³ V/cm) gives rise to efficient separation of charge carriers. There is no generation of additional states at the Si/SiO₂ interfaces in the silicon-on-insulator structures for both irradiation types, although this generation is observed in the initial thermal oxide.     

基于BCD工艺的充电控制芯片设计

提出一种蓄电池充电控制芯片的设计,具有恒流、恒压、过压、浮充等多种不同充电模式,可以在外部微处理器的支持下针对不同种类电池和应用场合的需要实现电池的高效优化充电。讨论并给出了芯片的系统组成及主要电路的设计,在1.5μm 50 V BCD(Bipolar-CMOS-DMOS)工艺下予以实现。测试结果表明芯片工作正常,电路功能及芯片预期的主要功能已成功实现。