多个硅通孔引起的热应力对迁移率和阻止区的影响

本文主要讨论了多个硅通孔引起的热应力对迁移率和阻止区的影响, 得到了器件沟道沿[100]方向时, 硅通孔之间的角度和间距对电子迁移率和阻止区的影响. 设定两种阻止区区域, 即迁移率变化分别为5%和10%的区域, 且主要考虑相邻TSV之间的区域. 仿真结果表明: 当硅通孔和X轴所成角度为π/4时, 电子迁移率变化和阻止区区域最小, 但是可布置器件区域不规则, 不易于布局. 随着间距的增加, 电子迁移率变化和阻止区区域逐渐增大, 趋向于单个TSV的情况; 当角度为0 时, 电子迁移率变化和阻止区区域变大, 可布置器件区域为硅通孔围成的中心小区域上, 形状比较规则, 便于布局. 而且随着间距的增加, 电子迁移率变化和阻止区区域越来越小, 趋向于单个硅通孔的情况.     

Local thermal conductivity of polycrystalline AlN ceramics measured by scanning thermal microscopy and complementary scanning electron microscopy techniques

The local thermal conductivity of polycrystalline aluminum nitride (AlN) ceramics is measured and imaged by using a scanning thermal microscope (SThM) and complementary scanning electron microscope (SEM) based techniques at room temperature. The quantitative thermal conductivity for the AlN sample is gained by using a SThM with a spatial resolution of sub-micrometer scale through using the 3ω method. A thermal conductivity of 308 W/m·K within grains corresponding to that of high-purity single crystal AlN is obtained. The slight differences in thermal conduction between the adjacent grains are found to result from crystallographic misorientations, as demonstrated in the electron backscattered diffraction. A much lower thermal conductivity at the grain boundary is due to impurities and defects enriched in these sites, as indicated by energy dispersive X-ray spectroscopy.     

An analytical model of thermal mechanical stress induced by through silicon via

We present an accurate through silicon via(TSV) thermal mechanical stress analytical model which is verified by using finite element method(FEM). The results show only a very small error. By using the proposed analytical model, we also study the impacts of the TSV radius size, the thickness, the material of Cu diffusion barrier, and liner on the stress. It is found that the liner can absorb the stress effectively induced by coefficient of thermal expansion mismatch. The stress decreases with the increase of liner thickness. Benzocyclobutene(BCB) as a liner material is better than Si O2. However,the Cu diffusion barrier has little effect on the stress. The stress with a smaller TSV has a smaller value. Based on the analytical model, we explore and validate the linear superposition principle of stress tensors and demonstrate the accuracy of this method against detailed FEM simulations. The analytic solutions of stress of two TSVs and three TSVs have high precision against the finite element result.     

考虑硅通孔的三维集成电路最高层温度模型

针对三维集成电路最高层芯片,引入硅通孔面积比例因子r,提出了考虑硅通孔的温度解析模型.Matlab分析表明,在芯片堆叠层数及芯片工作状态相同的情况下,考虑硅通孔之后的芯片温度比未考虑硅通孔时要低;r越大,芯片温度越低;当芯片堆叠层数较多且r较小时,温度随着r的减小急剧上升;对于8层的三维集成电路,硅通孔面积比例因子的最佳范围为0.5%~1%.     

Stress evaluation of Through-Silicon Vias using micro-infrared photoelasticity and finite element analysis

The Through-SiliconVias (TSV) is a key component of three dimensional electronic packaging. Obtaining its stresses is very important for evaluating its reliability. A micro-infrared photoelasticity system with a thermal loading function was built and applied to characterize the stresses of the TSV structure. Through testing it was found that the stress of each TSV is different even if their fabrication technology is exactly the same, that different TSVs obtain their stress free states at different elevated temperatures, and that their stress free states are maintained even when the temperature is further elevated. A finite element model was used to quantitatively determine the stresses of a TSV under different stress-free temperatures. Different virtual photoelasticity fringe patterns were then created based on the principle of photoelasticity and the simulated stresses. Comparing the virtual fringe patterns with the experimental pattern, an appropriate virtual photoelasticity fringe pattern and the corresponding stresses of TSV were determined     

考虑硅通孔的三维集成电路热传输解析模型

基于不考虑硅通孔的N层叠芯片的一维热传输解析模型,提出了硅通孔的等效热模型,获得了考虑硅通孔的三维集成电路热传输解析模型,并采用Matlab软件验证分析了硅通孔对三维集成电路热管理的影响.分析结果表明,硅通孔能有效改善三维集成电路的散热,硅通孔的间距增大将使三维集成电路的温升变大. 关键词： 三维集成电路 热管理 硅通孔 等效热模型     

Microstructural analysis by scanning thermal microscopy of a nanocrystalline Fe surface induced by ultrasonic shot peening

Experiments were carried out using a scanning thermal microscope (SThM) to investigate the ultrafine-grained microstructures in the surface layer of a pure iron sample produced by ultrasonic shot peening. The analysis of thermal properties by SThM shows that the thermal conductivity strongly depends on the grain size of the microstructure. The different contrasts on the thermal conductivity images are used to estimate the thickness of the affected surface layer produced by ultrasonic shot peening. The results demonstrate that the SThM can be used as a powerful tool for the microstructural analysis of the ultrafine-grained surface layer.     

一种考虑硅通孔电阻-电容效应的三维互连线模型

硅通孔(TSV)是三维集成电路的一种主流技术.基于TSV寄生参数提取模型,对不同物理尺寸的TSV电阻-电容(RC)参数进行提取,采用Q3D仿真结果验证了模型精度.分析TSVRC效应对片上系统的性能及功耗影响,推导了插入缓冲器的三维互连线延时与功耗的解析模型.在45nm互补金属氧化物半导体工艺下,对不同规模的互连电路进行了比较分析.模拟结果显示,TSVRC效应导致互连延时平均增加10%,互连功耗密度平均提高21%;电路规模越小,TSV影响愈加显著.在三维片上系统前端设计中,包含TSV寄生参数的互连模型将有助于设计者更加精确地预测片上互连性能.     

Microthermal machining using scanning thermal microscopy

Microthermal machining using scanning thermal microscopy (SThM) has been performed on polymethylmethacrylate (PMMA) materials, which are a soft polymer and suitable for microthermal machining. The probe of the SThM is heated and used as a machining tool on the PMMA material. Adjustment of the resistance can control the probe’s temperature. To obtain good machining quality, the probe temperature must be continuously controlled. The temperature of the machined area of the sample’s surface must be higher than the melting point of the PMMA material. However, a lower machined quality occurs when the probe temperature is too high. Furthermore, the adhesive phenomenon is very apparent when the contact mode is used in SThM machining. The microthermal machining of PMMA materials using SThM in semi-contact mode at a probe temperature of 400 °C has the best results. The technique can be used to process a complicated pattern and applied for use of high-density data storage.     

Carrier density distribution in silicon nanowires investigated by scanning thermal microscopy and Kelvin probe force microscopy

The use of scanning thermal microscopy (SThM) and Kelvin probe force microscopy (KPFM) to investigate silicon nanowires (SiNWs) is presented. SThM allows imaging of temperature distribution at the nanoscale, while KPFM images the potential distribution with AFM-related ultra-high spatial resolution. Both techniques are therefore suitable for imaging the resistance distribution. We show results of experimental examination of dual channel n-type SiNWs with channel width of 100 nm, while the channel was open and current was flowing through the SiNW. To investigate the carrier distribution in the SiNWs we performed SThM and KPFM scans. The SThM results showed non-symmetrical temperature distribution along the SiNWs with temperature maximum shifted towards the contact of higher potential. These results corresponded to those expressed by the distribution of potential gradient along the SiNWs, obtained using the KPFM method. Consequently, non-uniform distribution of resistance was shown, being a result of non-uniform carrier density distribution in the structure and showing the pinch-off effect. Last but not least, the results were also compared with results of finite-element method modeling.     

Modelling of thermal conductance during microthermal machining with scanning thermal microscope using an inverse methodology

In this study, a general methodology for determining the thermal conductance between the probe tip and the workpiece during microthermal machining using Scanning Thermal Microscopy (SThM) has been proposed. The processing system was considered as an inverse heat conduction problem with an unknown thermal conductance. Temperature dependence for the material properties and thermal conductance in the analysis of heat conduction is taken into account. The conjugate gradient method is used to solve the inverse problem. Furthermore, this methodology can also be applied to estimate the thermal contact conductance in other transient heat conduction problems, like metal casting process, injection molding process, and electronic circuit systems.     

用扫描热显微镜测量微小区域热导性质的探讨

随着高新技术的迅速发展,许多研究对象已进入亚微米和纳米范畴。在对这些对象的热性能和热可靠性的研究中,亚微米尺度的热物性测量已成为关键技术之一。例如：在微电子、微电子机械系统（MEMS）领域中,已使用纳米量级厚度的材质和做出纳米尺度线宽的器件。在材料科学、生物学、医学和化学等许多领域,高空间分辨率下的热物性测量也具有重要意义。本文经过实验;初步用扫描热显微镜判定了微小区域材料热导性质的差别,并从理论上探讨了用该仪器测量微小区域热导性质的方法原理。     

Reduction of signal reflection along through silicon via channel in high-speed three-dimensional integration circuit

The through silicon via （TSV） technology has proven to be the critical enabler to realize a three-dimensional （3D） gigscale system with higher performance but shorter interconnect length. However, the received digital signal after trans- mission through a TSV channel, composed of redistribution layers （RDLs）, TSVs, and bumps, is degraded at a high data-rate due to the non-idealities of the channel. We propose the Chebyshev multisection transformers to reduce the signal reflec- tion of TSV channel when operating frequency goes up to 20 GHz, by which signal reflection coefficient （$11） and signal transmission coefficient （$21） are improved remarkably by 150% and 73.3%, respectively. Both the time delay and power dissipation are also reduced by 4% and 13.3%, respectively. The resistance-inductance-conductance-capacitance （RLGC） elements of the TSV channel are iterated from scattering （S）-parameters, and the proposed method of weakening the signal reflection is verified using high frequency simulator structure （HFSS） simulation software by Ansoft.     

纳晶铜晶粒尺寸对热导率的影响

用热压烧结法制备得到纳晶铜块体. 用激光法测定了不同温度下制备得到的纳晶铜块体的热导率, 并建立卡皮查热阻模型对样品热导率进行模拟. 通过对比, 模拟结果与实验数据基本一致. 随着热压烧结温度的升高, 纳晶铜晶粒尺寸也随之增大. 在900和700 ℃其热导率分别达到了最大和最小值且所对应的热导率分别为200.63和233.37 W·m^-1·K^-1, 各占粗晶铜块体热导率的53.4%和60.6%. 验证了纳晶铜热导率在一定的晶粒尺寸范围内具有尺寸效应, 随着晶粒尺寸的减小, 热导率逐渐减小.     

Scanning near field thermal microscopy on a micromachined thin membrane

A resistive probe based scanning thermal microscope (SThM) has been used to perform complementary near field thermal measurements on the surface of a thin semiconductor membrane. This thin structure is part of a micromachined thermal rf power sensor and includes an integrated resistive heater used as an absorbing element for the input power. The resulting 2D surface temperature distribution and the 2D thermal wave propagation characteristic were determined. Considering the thermal wave behaviour at near field conditions, the local thermal conductivity of the thin membrane and the surrounding bulk material was investigated by usage of the 3ω-method.     

自加热式铜蒸气激光器的热气体透镜研究

本文分析了自加热式铜蒸气激光器放电管内的热气体透镜效应,并指出不同的铜蒸气激光器在稳定工作时可能等效为正透镜,也可能等效为负透镜。在实验部分,本文给出了热气体透镜焦距与输入功率、缓冲气体压强的关系,描绘了热气体透镜从负透镜变化到正透镜的动态过程。     

SmCo7纳米晶合金晶粒组织热稳定性的热力学分析与计算机模拟

推导出了单相纳米晶合金的晶界过剩体积与晶粒尺寸之间的定量关系, 建立了纳米晶合金的晶界热力学性质随温度和晶粒尺寸发生变化的确定性函数. 针对SmCo₇纳米晶合金, 通过纳米晶界热力学函数计算和分析, 研究了单相纳米晶合金的晶粒组织热稳定性. 研究表明, 当纳米晶合金的晶粒尺寸小于对应于体系中晶界自由能最大值的临界晶粒尺寸时, 纳米晶组织处于相对稳定的热力学状态; 当纳米晶粒尺寸达到和超过临界尺寸时, 纳米晶组织将发生热力学失稳, 导致不连续的快速晶粒长大. 利用纳米晶合金热力学理论与元胞自动机算法相耦合的模型对SmCo₇纳米晶合金在升温过程中的晶粒长大行为进行了计算机模拟, 模拟结果与纳米晶合金热力学模型的计算预测结果一致, 由此证实了关于纳米晶合金晶粒组织热稳定性的研究结论. 关键词： 纳米晶合金热力学 7纳米晶合金')" href="#">SmCo₇纳米晶合金 热稳定性 计算机模拟     

Calibration of a scanning Joule expansion microscope (SJEM)

Scanning thermal microscopy (SThM) is a scanning probe technique based on atomic force microscopy (AFM) enabling high-resolution topographical imaging together with visualization of the temperature distribution in the studied sample. For the thermal mapping, rather expensive, micro-fabricated cantilevers with integrated thermocouples have to be used. The spatial resolution is typically limited to 100 nm. Scanning Joule expansion microscopy (SJEM) uses an alternative approach to detect the temperature of the sample with a regular silicon cantilever and lock-in detection. By monitoring the thermal expansion of the sample (due to Joule heating), the local temperature can be monitored. The resolution of SJEM is comparable to that of contact AFM, which is an order of magnitude better than for SThM. Our research involves implementing a SJEM for the study of heating phenomena in mesoscopic structures prepared by electron beam lithography and lift-off techniques. In particular, we calibrated our SJEM in order to make quantitative temperature maps of the studied samples.     

Heat transfer enhancement in MOSFET mounted on different FR4 substrates by thermal transient measurement

Miniaturization of electronic package leads to high heat density and heat accumulation in electronics device, resulting in short life time and premature failure of the device. Junction temperature and thermal resistance are the critical parameters that determine the thermal management and reliability in electronics cooling. Metal oxide field effect transistor (MOSFET) is an important semiconductor device for light emitting diode-integrated circuit (LED IC) driver application, and thermal management in MOSFET is a major challenge. In this study, investigations on thermal performance of MOSFET are performed for evaluating the junction temperature and thermal resistance. Suitable modifications in FR4 substrates are proposed by introducing thermal vias and copper layer coating to improve the thermal performance of MOSFET. Experiments are conducted using thermal transient tester (T3ster) at 2.0 A input current and ambient temperature varying from 25 ℃to 75 °C. The thermal parameters are measured for three proposed designs: FR4 with circular thermal vias, FR4 with single strip of copper layer and embedded vias, and FR4 with I-shaped copper layer, and compared with that of plain FR4 substrate. From the experimental results, FR4_I-shaped shows promising results by 33.71% reduction in junction temperature and 54.19% reduction in thermal resistance. For elevated temperature, the relative increases in junction temperature and thermal resistance are lower for FR4_I-shaped than those for other substrates considered. The introduction of thermal vias and copper layer plays a significant role in thermal performance.     

Effect of the shape and concentration of filler particles on the thermal expansion of polymer composites

The thermal expansion coefficient (TEC) of poly-2,6-dimethyl-1,4-phenylene oxide (PDPO) decreases upon the introductions of copper and aluminum powders or pieces of glass and carbon fibers into the compound. This effect is associated with the formation of boundary layers of the matrix around filler particles. Molecules in the boundary layers are “straightened” and packed parallel to the filler surface, which decreases the TEC. The concentration dependences of the TEC have a minimum, which is explained by partial destruction of the boundary layers, when the mean distance between the surfaces of filler particles becomes smaller than their triple diameter.