一种考虑温度时间-空间分布的解析互连延时模型

本文从热扩散方程出发,得到了互连温度时间-空间分布的解析表达式.考虑互连温度对互连电阻和Elmore延时的影响,同时提出了一种用以分析互连时间-空间温度分布效应对互连延时影响的等效内阻模型.基于所提出的模型,详细地分析了互连长度、输入信号频率和功率对互连延时的影响.所提出的互连温度分布和延时解析模型可以应用于深亚微米温度相关的互连性能分析中.     

两相邻耦合RLC互连的串扰估计

本文建立了一种考虑电感耦合效应的两相邻耦合互连模型,基于传输函数直接截断的方法给出了其互连串扰的解析表达式.讨论了该解析公式在局部互连和全局互连两种情况下的应用,其结果相对于HSPICE的误差小于10%.它可以用于考虑串扰效应的版图优化.     

基于45 nm技术的ULSI互连结构的温度模拟

应用自行建立的准二维简化模型，计算了三种基于45nm节点技术的ULSI九层低介电常数介质互连结构的温度升高。与ANSYS的分析对比表明，简化模型误差为7．7％。三种互连结构中，结构Ⅲ设计具有最佳的散热能力，不仅工作时绝对温升小，而且随衬底温度和介质导热系数的温升加大也小；结构Ⅰ的散热能力良好，结构Ⅲ最差。对三种互连结构的尺寸分析表明，层间介质的厚度对互连系统的温升影响大，必须在电学模拟和温度模拟完成后找到一个最佳厚度值，以保证既有好的散热条件，又有利于减小RC延迟。互连结构的温升随电介质导热系数的减小呈二阶指数升高，特别当介质导热系数小于0．1W／℃·m时，互连结构设计将会成为器件温升和系统可靠性的关键所在，引入新技术或许势在必行。     

用于空间光互连的850 nm VCSEL 4×4阵列的热场模拟

作为空间光互连系统的发射部分,垂直腔表面发射激光器(VCSEL)阵列的热特性直接影响到光互连系统的稳定性。建立了850nm VCSEL 4×4阵列的热场数学模型,并利用有限差分法求解热传导和热扩散方程,得出了在VCSEL单元工作电流为10mA时阵列的热场分布:VCSEL单元有源层温度约为50℃;整个阵列的温度仅为38.65℃。依据此结果制作了850nm 4×4光互连模块,其每通道稳定传输速率达到1Gbit/s。     

多个短脉冲辐照下光学元件的温升分布

从傅里叶热传导方程出发,推导了在多个幅度、间隔不等的短脉冲辐照下,无源光学元件温升三维分布的含有时间的解析表达式,针对具有周期性的重复脉冲照射的情况进行了具体的计算分析,讨论了入射脉冲数目、脉冲间隔及脉冲通量密度等与光学元件的温升分布的关系,并估计了温升引起的光波相位畸变。     

中红外2 μm Tm∶YLF激光热效应分析

基于2 μm Tm∶YLF激光器的实际工作条件建立了各向异性激光晶体的稳态热模型,通过解析法得到了Tm晶体内温度场分布的解析表达式;模拟并分析了泵浦功率、光斑半径、晶体端面尺寸对Tm晶体内温度场分布的影响。最终得到了在不同条件下晶体内部温度分布,结果表明：掺杂浓度的增加加剧了晶体的温升,增加了晶体热畸变不均匀性,产生更明显的热效应;而晶体长度的适度增加降低了晶体的温升,缓解了晶体热畸变不均匀性,削弱了晶体的热效应。所得结论可以为LD抽运Tm∶YLF激光器的腔型及散热系统设计提供理论支持。     

脉冲激光表面强化数值模拟及热物性参量影响

建立了包含脉冲激光束时空分布、依赖于温度的材料参量、组织演化历史以及多次相变特征在内的脉冲激光表面强化三维有限元模型。针对常热物性和变热物性并考虑相变潜热两种情况，温度场及其演化分别得到了解析解和通用有限元软件的验证，强化区层深和宽度得到了实验验证。研究了材料热物性对强化区的影响，得到了一定范围内强化区层深随材料热物性参量的变化规律，即：热传导系数不变时，强化区层深随热扩散率的增加而增加；比热容不变时，强化区层深随热扩散率的增加而减小；热扩散率一定时，强化区层深随热传导系数和比热容的增加而降低。以球铁、共析钢和巾碳钢为例，分析了两种确定材料热物性常数方法，即一定温度范围内的平均值法和选取奥氏体化温度附近参量方法的可行性，研究表明平均值法可以得到较好的结果。     

KDP晶体中杂质缺陷吸收引起的温度场模型

在点源热脉冲传热模型的理论基础上,采用格林函数法建立了由于单个杂质缺陷吸收引起的温度场模型,得到了杂质附近温度场的解析表达式,分析了激光脉冲参数对温度场的影响情况,并在单个杂质吸收的理论基础上推导得到KDP晶体某一区域内含多个杂质吸收的模型。结果表明杂质吸收引起的温度变化与激光脉冲参数密切相关。当杂质间距离小于激光持续时间内产生的热扩散距离时,就会引起杂质间温度场的叠加,并且当杂质密度大到一定程度时,会使杂质团区域的温升加剧,导致晶体发生激光诱导损伤的可能性加大。     

由周期型强激光脉冲引起的光学元件的温度分布

在本文中,我们根据强激光脉冲的重复频率较低,脉宽窄的特点,把介质在一个周期中受辐照的温升分为辐照阶段和辐照后热扩散阶段处理。在充分考虑辐照脉冲的周期性特征后,得出了稳定周期运行的系统中光学元件上的温度分布。     

一种新型的全局互连结构及其加工方法

随着特征尺寸的缩小,互连成为制约集成电路性能提高和成本下降的主要因素.为了降低互连延迟,提出了一种全新的全局互连结构,即利用掩膜电镀和CMP技术形成三维的铜互连结构,再利用牺牲层技术将三维结构镂空,得到悬空的全局互连结构.该结构可大大地降低全局互连对延迟的影响.     

非晶硅薄膜晶体管的热阻模型

基于能量方程、热流方程和边界条件,推导出了非晶硅薄膜晶体管的沟道热阻模型。采用该模型可准确预估器件有源层内的平均温度。在沟道热阻模型的基础上,考虑器件间场氧化层和金属互联线的影响,建立了非晶硅薄膜晶体管的二维热阻模型。采用该模型可描述器件有源层内温度的横向分布,并快速预估沟道内的最高结温。最后,将模型预测结果与器件模拟仿真结果进行了对比,两者拟合良好。     

一种新型的集成电路金属连线温度分析解析模型

研究了金属连线上的焦耳热对连线温度的影响,进而提出了一种新型的集成电路多层金属连线上的温度模拟器(LTem).该模拟器采用一种相对简单的热学解析模型,详细考虑了通孔效应以及边缘效应对温度分布的影响.模拟结果表明,考虑了通孔效应以及边缘效应之后,金属连线上的温度分布情况有了较大程度上的降低,LTem可以得到更贴近实际情况的金属连线温度分布情况     

Thermally-aware modeling and performance evaluation for single-walled carbon nanotube-based interconnects for future high performance integrated circuits

Given the performance and reliability limits of conventional copper interconnects in the tens of nanometer regime, carbon-nanotube (CNT) based interconnects emerge as a potential reliable alternative for future high performance VLSI industry. In this paper, we present an accurate thermally-aware model for single-walled carbon-nanotube (SWCNT) based interconnects. Our thermally-aware model is an integration of temperature-dependent electrical parasitics model and thermal equivalent circuit that captures both self-heating and heat conduction phenomena. We verify the accuracy of our electro-thermal model against recently reported experimental measurements. By leveraging the presented electro-thermal model, we present a simulation platform to estimate the performance of SWCNT-based interconnects under different temperature conditions. Our thermally-aware model achieves improvement in the delay estimation accuracy of about 51.3% on average. Based on our simulation results, SWCNT-based interconnects offer more than 5×reduction in delay at dimensions of about 10-20 nm for 27- 127 °C temperature range.     

Prediction of net-length distribution for global interconnects in aheterogeneous system-on-a-chip

A system-on-a-chip (SoC) contains several pre-designed heterogeneous megacells that have been designed and routed optimally. In this paper a new stochastic net-length distribution for global interconnects in a nonhomogeneous SoC is derived using novel models for netlist, placement, and routing information. The netlist information is rigorously derived based on heterogeneous Rent's rule, the placement information is modeled by assuming a random placement of terminals for a given net in a bounding area, and the routing information is constructed based on a new model for minimum rectilinear Steiner tree construction (MRST). The combination of the three models gives a priori estimation of global net-length distribution in a heterogeneous SoC. Unlike previous models that empirically relate the average length of the global wires to the chip area, the new distribution provides a complete and accurate distribution of net-length for global interconnects. Through comparison with actual product data, it is shown that the new stochastic model successfully predicts the global net-length distribution of a heterogeneous system     

Structure Function Representation of Multidirectional Heat-Flows

The relation between the structure function of a one-port dynamic thermal network and the spatial distribution of thermal properties in a heat diffusion problem with applied boundary conditions is generalized from 1D heat flows to multidirectional heat flows. A strategy for exploiting this relation is derived which allows an accurate localization of defects and measurement of thermal properties in components and packages not only when the heat diffusion problem is 1D but also 3D.     

Textural and microstructural transformation of Cu damascene interconnects after annealing

Influence of annealing on the textural and microstructural transformation of Cu interconnects having various line widths is investigated. Two types of annealing steps have been considered here: room temperature over 6 months and 200°C for 10 min. The texture was determined by x-ray diffraction (XRD) of various cross-sectional profiles after electropolishing, and the surface, microstructure, and grain boundary character distribution (GBCD) of Cu interconnects were characterized using electron backscattered diffraction (EBSD) techniques. In order to analyze a relationship between the stress distribution and textural evolution in the samples, microstresses were calculated with decreasing line widths at 200°C using finite element modeling (FEM). In this investigation, it was found that the inhomogeneity of stress distribution in Cu interconnects is an important factor, which is necessary for understanding textural transformation after annealing. A new interpretation of textural evolution in damascene interconnects lines after annealing is suggested, based on the state of stress and the growth mechanisms of Cu electrodeposits.     

Thermal mapping of interconnects subjected to brief electricalstresses

The failure of metal interconnects subjected to brief electrical-current pulses is a reliability concern for the integrated circuits industry, especially in connection with electrostatic discharge (ESD). Since the magnitude and spatial distribution of the temperature rise during pulsing events strongly influence these failures, the development of suitable thermometry techniques is needed to understand the failure. This work reports scanning laser-reflectance thermometry with a novel calibration procedure, which captures transient temperature distributions along interconnects subjected to sub-microsecond current pulses. The temperature distribution is strongly affected by corners and contact pads and by the pulse duration     

Thermal microscopy and heat generation in electronic devices

This paper reports our progress on the development of thermal microscopy for studying heat generation in electronic devices and interconnects. The resolution of the scanning thermal microscope has been improved from about 500 nm achieved by the first wire thermocouple probes to about 25 nm for the more recent thin-film thermocouple probes. These have been used to measure the temperature distribution and hot spots of single transistors, short circuits in transistors created by electrostatic discharge failures, as well as novel devices such as vertical-cavity surface emitting lasers and magnetoresistive reading heads. Recently, a new technique called scanning Joule expansion microscopy has been developed to measure the temperature distribution of electrically heated samples with about 10 nm spatial resolution. The advantage of this technique is that it does not require fabrication of temperature-sensing probes and can use commercially-available cantilever probes that are employed in atomic force microscopes.     

脉冲激光制备ZnO薄膜烧蚀过程中的温度演化

为了研究脉冲激光烧蚀氧化锌靶材的整个过程,给出脉冲激光作用块状靶材的烧蚀模型.从包含热源项的导热方程出发,利用适当的动态边界条件,详细研究了靶材在熔融前的温度分布规律.结果表明,靶材熔融前,在固定位置,温度随时间推移而升高,且距离靶面越近,变化率越大.在同一时刻不同位置,温度随着热扩散距离增加而下降;并采用精确解与积分近似法相结合的方案,给出熔融后固液两相的温度分布与时间和位置的变化关系.液相的温度梯度随扩散距离增加而下降,在距烧蚀面0.5μm之内,温度梯度很大;在0.5μm后面的部分,温度变化就很缓慢;固相的温度变化较为复杂.     

Reliability aspects of copper metallization and interconnect technology for power devices

The introduction of thick copper metallization and topside interconnects as well as a superior die attach technology is improving the performance and reliability of IGBT power transistor technologies significantly.The much higher specific heat capacity and higher thermal conductivity increases the short circuit capability of IGBTs, which is especially important for inverters for drives applications. This opens the potential to further optimize the electrical performance of IGBTs for higher energy efficiency.The change in metallization requires the introduction of a reliable barrier against copper diffusion and copper silicide formation. This requires the development of an efficient test method and reliability assessment according to a robustness validation approach.In addition, the new metallization enables interconnects with copper bond wires, which yield, together with an improved die attach technology, a major improvement in the power cycling capability.