Scanning spreading resistance microscopy of defect engineered low dose SIMOX samples

Modification of SiO₂ precipitate formation by defect engineering of SIMOX (separation by implanted oxygen) process was studied using cross section scanning spreading resistance microscopy (SSRM). Firstly, open volume defects, nanocavities, have been introduced by He⁺ ion implantation in the region, where SiO₂ precipitates were subsequently formed. Secondly, dual (simultaneous) oxygen (O⁺) and silicon (Si⁺) implantation was used to modify SiO₂ reaction kinetics too. The results show that the He-induced nanocavities enhance the SiO₂ formation presumably releasing excess strain associated with Si oxidation, while the use of a dual O⁺/Si⁺ beam do not influence significantly the oxidation kinetics in the initial state of the SIMOX process in our samples. Overall, SSRM was shown to be a suitable method for observation of the early stage of buried oxide formation in Si, since it measures the local resistivity, the main functional parameter of a SIMOX structure.     

Scanning probe microscope analysis of microstructures in optically variable devices

The fine-scale features of optically variable devices (OVDs) fabricated in resist by electron beam lithography have been examined using scanning probe microscopy (SPM). These features have included patterns of gratings, micro-text and geometrical images. Scanning probe microscopy has provided information on the groove angle, depth of profile and spatial frequency of the features as determined by the details of processing of the image. The OVD patterns formed in EBR-9 and X-AR-P 7400 resists exhibited a more rounded profile with a lower side-wall angle than in ZEP-7000 and PMMA resists.     

Use of C-SAM acoustical microscopy in package evaluations and failure analysis

Acoustical microscopy is gaining wide acceptance in the microelectronic packaging community. C-mode scanning acoustical microscopy, C-SAM, is widely used in package evaluations and for failure analysis. This paper discusses several specific topics. These include: (1) popcorn cracking in SMDs; (2) an evaluation of solder die attach in power packages; (3) an instance of top of die delamination which resulted in electrical failures; and (4) moisture sensitivity of other surface mount power packages and how it resulted in ball bond degradation during a new product qualification.     

Spectroscopic photon emission microscopy: a unique tool for failure analysis of microelectronics devices

Photon emission microscopy (PEM) is a technique used commonly for failure analysis of microelectronics chips. This technique has it limitations: it can only be used to indicate the place of the failure. In most cases, this is not enough to allow a definition of the failure, i.e. to find out whether it is due to a gate oxide breakdown, a metal short, a junction spiking, etc. In this paper spectral PEM is discussed. It is shown that the spectrum of the light emitted by the failure may offer valuable information about the identity of the failure.     

半导体器件扫描电镜低电压成像技术应用

针对使用扫描电镜(SEM)进行半导体器件破坏性物理分析(DPA)和失效分析(FA)时,芯片表面不作喷镀处理的问题,提出了减小或消除电荷累积的试验方法。试验结果表明,正确应用SEM低电压技术,选择加速电压1.0 kV~2.0 kV、电子束斑2.0,结合积分技术,可在芯片表面不作喷镀处理,并满足国军标要求下,得到分辨率和性噪比均很好的图片。     

用于横向RESURF器件击穿电压优化的电荷分配模型

A new quite simple analytical model based on the charge allocating approach has been proposed to describe the breakdown property of the RESURF （reduced surface field） structure. It agrees well with the results of numerical simulation on predicting the breakdown voltage. Compared with the latest published analytical model, this model has a better accuracy according to the numerical simulation with simpler form. The optimal doping concentration （per unit area） of the epi-layer of the RESURF structures with different structure parameters has been calculated based on this model and the results show no significant discrepancy to the data gained by others. Additionally the physical mechanism of how the surface field is reduced is clearly illustrated by this model.     

Nonlinear electro-thermal modeling and field-simulation of OLEDs for lighting applications II: Luminosity and failure analysis

In recent years great effort has been put into development of lighting purpose Organic Light Emitting Diodes (OLEDs) worldwide. Among many concerns of developers is heat-removal from the thin film structure of the active layers of OLEDs which are typically realized on low thermal conductivity substrates such as glass or polymer foils. The other issue is to provide the OLEDs with transparent, yet high electrical conductivity electric power supply structure, therefore metallic shunting grids are added to the layer stack of OLEDs. These two major issues necessitate self-consistent electro-thermal simulation of large area OLEDs in which the temperature dependent I–V characteristics of the light emitting polymer layers are also considered. Our first article discussed the details of the algorithmic fundamentals of our nonlinear electro-thermal field solver. This second paper presents the new, temperature dependent radiance and luminance distribution map calculation extension of the algorithm. Using this feature the inhomogeneity of large area OLEDs in free convection environment can be estimated; such calculations for glass-based research OLED samples are also presented. Because of the operational degradation of the OLED, non-emissive “dark” spots can appear. Cause of these spots can be e.g. manufacturing problem, damage of the surface protection, etc. Electro-thermal and luminance simulation of this failure type is demonstrated and is compared with measured results. Thermal runaway as the possible physical phenomenon behind the appearances of dark spots is proved by simulations.     

A charge allocating model for the breakdown voltage calculation and optimization of the lateral RESURF devices

A new quite simple analytical model based on the charge allocating approach has been proposed to describe the breakdown property of the RESURF (reduced surface field) structure. It agrees well with the results of numerical simulation on predicting the breakdown voltage. Compared with the latest published analytical model, this model has a better accuracy according to the numerical simulation with simpler form. The optimal doping concentration (per unit area) of the epi-layer of the RESURF structures with different structure parameters has been calculated based on this model and the results show no significant discrepancy to the data gained by others. Additionally the physical mechanism of how the surface field is reduced is clearly illustrated by this model.     

A novel analytical model of the vertical breakdown voltage on impurity concentration in top silicon layer for SOI high voltage devices

A novel analytical model of the vertical breakdown voltage (V_{B , V} ) on impurity concentration (N_d ) in top silicon layer for silicon on insulator high voltage devices is first presented in this article. Based on an effective ionisation rate considering the multiplication of threshold energy ε_T in the electron, a new formula of silicon critical electric field E_{S , C} on N_d is derived by solving a 2D Poisson equation, which increases with the increase in N_d especially at higher impurity concentration, and reaches up to 68.8?V/µm with N_d  = 1 × 10¹⁷?cm^?3 and 157.2?V/µm with N_d  = 1 × 10¹⁸?cm^?3 from the conventional about 30?V/µm, respectively. A new physical concept of critical energy ε_B is introduced to explain the mechanism of variable high E_{S , C} with heavy impurity concentration. From the E_{S , C} , the expression of V_{B , V} is obtained, which is improved with the increasing N_d due to the enhanced E_{S , C}. V_{B , V} with a dielectric buried layer thickness (t_I ) of 2?µm increases from 428?V of 1 × 10¹⁷?cm^?3 to 951?V of 1 × 10¹⁸?cm^?3. The dependence of N_d and top silicon layer thickness (t_S ) for an optimised device is discussed. 2D simulations and some experimental results are in good agreement with the analytical results.     

The role of failure analysis in establishing design rules for reliable plastic products

Plastic products can fail in a large variety of modes because of errors in the design, processing and application. The designer must take into account these errors in order to prevent these errors rather than notice them.Without having knowledge of the complex mechanical behaviour of plastics and the structure related properties, adequate design of reliable products is impossible. The designer must also be aware of the specific failure modes, failure causes and failure mechanisms and he can achieve this by failure analysis. Important information from analyses of failed products is the handling of users in ways not foreseen by him. A classification of failed plastic products based on failure causes and failure mechanisms is presented and should be used in carrying out Failure Modes and Effects Analysis.     

Location of current carrying failure sites in integrated circuits by magnetic force microscopy at large probe-to-sample separation

In integrated circuit failure analysis excessive current flow is often used to indicate the presence of faulty devices. By imaging the magnetic field produced by current flowing in integrated circuit conductors, these faulty devices can be located. Fault location by magnetic field imaging can be problematic as the devices are often buried under several layers of dielectrics and conductors that are up to several microns thick. In this paper we present a new technique for fault location based on magnetic force imaging of the magnetic field. By subtracting magnetic force images acquired at different probe-to-sample distances, the effects due to background, and probe geometry can be eliminated. We demonstrate that this method is capable of locating current carrying failure sites in model circuits with sub-micrometer uncertainty. We show how the technique can be used to map current paths in the presence of interfering currents on power supply and ground lines.     

环扫电镜表征影响因素及芯片失效分析应用

对环境扫描电镜(ESEM)表征影响因素进行试验研究,根据半导体芯片的结构,进行成像参数优化,试验结果表明较为适合的优化参数为:腔室气压40Pa~80Pa,加速电压10kV~20kV.研究了裙散效应对能谱分析的影响,结果表明非分析区域元素含量与离能谱分析点的距离呈幂函数衰减,应证了文献报道的理论计算,对于能谱分析排除干扰元素有一定的参考意义.针对破坏性物理分析(DPA)试验中发现的塑封器件腐蚀缺陷,利用ESEM在优化参数下进行机理分析,结果表明玻璃钝化层裂纹是导致铝金属条被腐蚀的原因,而玻璃钝化层裂纹是由于器件材料性质不匹配,在热载荷条件下产生热应力而引起.这种表层缺陷极有可能因为镀膜而被掩盖,因此,利用ESEM检测半导体器件具有一定的必要性.     

具有法拉第屏蔽罩的射频LDMOS功率晶体管漏源击穿电压模型

本文基于静电势的抛物线近似,通过求解p-外延层和n-漂移区的二维泊松方程,建立了具有法拉第屏蔽罩的射频LDMOS功率晶体管漏源击穿电压解析模型。分析了器件参数对击穿电压的影响。与已发表模型相比,本文模型增加了p-外延层掺杂浓度对击穿电压的影响。通过模型计算结果与数值仿真以及测试结果的比较,验证了模型的有效性。并根据所得模型分析了怎样合理选择器件参数以同时优化器件性能指标,如击穿电压、导通电阻和反馈电容。     

An analytical model for punch-through limited breakdown voltage of planar junction with multiple floating field limiting rings

An appropriate model for punch-through (PT) limited breakdown voltage of a planar junction is presented for the first time as a function of the normalized epitaxial layer thickness and the critical depletion width of the cylindrical junction at breakdown in non-PT case. The results are applied to the planar junction structure with a single ring, taking into account three different breakdown modes. The problem of the multiple ring structure is solved using the equivalent ring method, which allows determination of the PT limited breakdown voltage and optimized ring spacings for the structure. Comparisons with two-dimensional device simulations using MEDICI show a good agreement.     

透射电镜微观组织图像处理定量分析系统设计

本文基于LabVIEW的图像处理与可视化编程分析模块,建立微观形貌目标测量和微观组织定量分析系统,以拓展软件功能和提高测试分析效率.对于方形和圆形微孔组织形貌像进行灰度变换,对阈值分割图像进行边缘检测和轮廓提取,利用卡钳测量模块对方格尺寸和圆孔直径进行测量并与标准值进行比对,测量误差均在允许误差范围内,证明图像处理与分...     

Interfacial reaction and failure mode analysis of the solder joints for flip-chip LED on ENIG and Cu-OSP surface finishes

The interfacial reactions and failure modes of the solder joints for flip-chip light emitting diode (LED) on electroless nickel/immersion gold (ENIG) and Cu with organic solderability preservatives (Cu-OSP) surface finishes were investigated in this study. The experimental results demonstrate that the interfacial reactions in the Au/Sn–Ag–Cu(SAC)/ENIG and Au/SAC/Cu systems are different but the failure mechanisms of the two types of solder joints are similar during the shear test. For the Au/SAC/ENIG system, the Au layer on the surface finish of the diodes dissolved into the molten solder and transformed into a continuous (Au, Ni)Sn₄ IMC layer at the diode/solder interface during reflow and the interfacial IMC at the solder/ENIG interface is dendritic Ni₃Sn₄ IMC grains which are surrounded by (Au, Ni)Sn₄. For the Au/SAC/Cu system, however, no IMC layers can be observed at the diode/solder interface. The interfacial IMC at the solder/Cu interface is (Cu, Au)₆Sn₅ and a Cu₃Sn IMC layer at the (Cu, Au)₆Sn₅/Cu interface. Tiny (Au, Cu)Sn₄ IMC grains distribute in the solder layer and surround the (Cu, Au)₆Sn₅ grains. For the two types of systems, the primary failure mode for the cathode is due to the broken of the Si-based insulation layer which led to a high residue stress and poor connection between the Si-based layer and the solder layer. Meanwhile, the failure of the solder joint for the anode is mainly because of the failure of the solder layer under the conductive via. The crack generally forms at this area and then propagated along the diode or the diode/solder interface.     

激光诱导击穿光谱结合GA-BP-ANN检测炉渣中

以激光诱导击穿光谱技术为基础,通过击穿炉渣中等离子体来获取炉渣光谱图,将遗传算法与BP神经网络进行结合,通过遗传算法对神经网络的权值和阈值进行优化建立基于遗传神经网络模型,对炉渣元素光谱图中的Ca元素含量进行定量检测,测得5种Ca元素#1、#2、#3、#4、#5的质量分数为29.4 %、40.37 %、37.13 %、43.88 %、38.68 %,并计算检验样本相对误差分别为4.7 %、5.2 %、5.8 %、4.1 %、3.3 %,相对误差均在6 %以下,检测精度明显优于BP-ANN方法和光谱分析中常用的自由定标法,表明基于遗传神经网络对炉渣进行定量分析具有更好的检测效果。     

适用SAW器件的ZnO/Ti/Si薄膜制备及缺陷分析

在Si(100)衬底和Ti/Si(100)衬底上分别制备了ZnO薄膜,探讨了Ti缓冲层对ZnO薄膜结构和缺陷的影响,利用X射线衍射(XRD)测试了ZnO薄膜的晶体结构及择优取向,利用原子力显微镜(AFM)观察ZnO薄膜的表面粗糙度(RMS),利用光致发光(PL)光谱检测了ZnO薄膜的缺陷,利用四探针法测试了ZnO薄膜的电阻率。结果表明,在Ti/Si(100)衬底上、衬底温度350℃的条件下,制备的ZnO薄膜表面光滑、缺陷少、电阻率高且具有高C轴取向。本文这一工作对于压电薄膜缺陷分析及高性能ZnO的声表面波(SAW)器件研制有重要意义。     

The correlation of the electrical properties with electron irradiation and constant voltage stress for MIS devices based on high-k double layer (HfTiSiO:N and HfTiO:N) dielectrics

This paper describes the influence of e-beam irradiation and constant voltage stress on the electrical characteristics of metal-insulator-semiconductor structures, with double layer high-k dielectric stacks containing HfTiSiO:N and HfTiO:N ultra-thin (1 and 2 nm) films. The changes in the electrical properties were caused by charge trapping phenomena which is similar for e-beam irradiation and voltage stress cases. The current flow mechanism was analyzed on the basis of pre-breakdown, soft-breakdown and post-breakdown current-voltage (J-V) experiments. Based on α-V analysis (α=d[ln(J)]/d[ln(V)]) of the J-V characteristics, a non-ideal Schottky diode-like current mechanism with different parameters in various ranges of J-V characteristics is established, which limits the current flow in these structures independent of irradiation dose or magnitude of applied voltage during stress.     

Queuing analysis of cooperative GBN-ARQ in wireless networks with peers contending for a common helper

This paper presents a new queuing model for performance analysis of go-back-N automatic repeat request (GBN-ARQ) protocol in cooperative wireless networks. In the model, cooperative medium access control (CoopMAC) protocol and dynamic radio link adaptation are taken into consideration. We analyze the probability distribution of the total delay witnessed by packets at the source side. Multi-rate transmissions are considered for all links with link adaptation. An enhanced Markov model is introduced in our model, which encompasses the following aspects: CoopMAC protocol at the MAC sub-layer; GBN-ARQ protocol at the logical link control sub-layer and the transmission using decode-and-forward cooperative diversity at the physical layer. The stochastic process of random feedback delay because of peers contending for a common helper is analyzed. The queuing system is modeled as a GI/M/1 Markov chain to acquire statistics of the exact queue length and the total delay. We analyze the effects of Doppler frequency shift and packet arrival rate on the total delay. The analysis is validated by simulation.