非制冷红外探测器多孔硅绝热层的研究

以多孔硅作为绝热层材料,采用超高真空对靶磁控溅射镀膜法,在多孔硅样品表面和硅基底表面沉积氧化钒薄膜.实验采用电化学腐蚀法制备多孔硅,利用场致发射扫描电子显微镜观测了孔隙率为50%,60%,70%三个多孔硅样品的微观形貌.利用显微喇曼光谱法测量其热导率,分别为8.16,7.28和0.624W/mK;利用纳米压入仪测量氧化钒薄膜的显微硬度和杨氏模量,测得沉积在孔隙率为50%,60%,70%的多孔硅基底上氧化钒薄膜的显微硬度分别为1.917,0.928和0.13 GPa,杨氏模量分别为31.087,16.921和2.285 GPa,而沉积在单晶硅基底的氧化钒薄膜的显微硬度和杨氏模量分别为10.919 GPa和193.792 GPa,并分析了微观结构差异对多孔硅绝热性能和机械性能的影响,为非制冷红外探测器的工艺制作过程提供一定的热学力学参数.     

非制冷红外探测器多孔硅绝热层的研究

以多孔硅作为绝热层材料，采用超高真空对靶磁控溅射镀膜法，在多孔硅样品表面和硅基底表面沉积氧化钒薄膜。实验采用电化学腐蚀法制备多孔硅，利用场致发射扫描电子显微镜观测了孔隙率为50%，60%，70%三个多孔硅样品的微观形貌。利用显微喇曼光谱法测量其热导率，分别为8.16，7.28和0.624W/mK；利用纳米压入仪测量氧化钒薄膜的显微硬度和杨氏模量，测得沉积在孔隙率为50%，60%，70%的多孔硅基底上氧化钒薄膜的显微硬度分别为1.917，0.928和0.13GPa，杨氏模量分别为31.087，16.921和2.285GPa，而沉积在单晶硅基底的氧化钒薄膜的显微硬度和杨氏模量分别为10.919GPa和193.792GPa，并分析了微观结构差异对多孔硅绝热性能和机械性能的影响，为非制冷红外探测器的工艺制作过程提供一定的热学力学参数。     

室温相变氧化钒薄膜的制备及其CO2激光毁伤试验

军事目标的抗强激光毁伤是亟待解决的热点难点问题,利用氧化钒的相变特性进行激光防护是当前这一领域的热点之一。本文采用直流磁控溅射加后续热处理的方法在普通玻璃基底上制备了氧化钒薄膜,通过测量其电阻温度特性曲线来观测其相变特性,并利用功率为8.9 W、光斑直径为4.4 mm的二氧化碳连续激光分别照射用作基底的普通玻璃和制备的相变氧化钒薄膜样品进行激光毁伤试验。试验数据显示该薄膜的相变温度约为30°C,薄膜的双向光谱反射率在相变前后分别为13.48%和76.4%,用作基底的玻璃在激光照射7.5 s后破碎,而制备的薄膜样品在照射38 s后才破碎。这表明本文制备的室温相变氧化钒薄膜在相变后具有高反射特性,从而具有一定的抗强激光毁伤能力。     

多孔硅纵向孔隙率与残余应力分布的研究

利用电化学方法在p型重掺杂单晶硅(100)基体上制备了多孔硅薄膜,通过质量计算法得到多孔硅的孔隙率,并研究了多孔硅孔隙率随腐蚀深度变化的规律。利用显微拉曼光谱技术对多孔硅纵切面上的残余应力进行了测量,结果表明,多孔硅的孔隙率随腐蚀时间/深度的增加有先增加后减少的趋势;多孔硅纵向上存在拉伸残余应力,拉伸应力的分布与纵切面上孔隙率的分布成正比,先增大,再减小;到达多孔硅与基体硅的界面处时,拉伸应力减小为零,靠近硅一侧,转变为压应力;残余应力的最大值出现在临近多孔硅表面以下的区域。这主要与多孔硅制备过程中孔内HF酸浓度的降低和硅/电解液表面的电偶层有关。     

磁控溅射功率对光学氧化钒薄膜结构和性能的影响

采用射频磁控溅射法制备氧化钒(VOx)薄膜,研究溅射功率对氧化钒薄膜结构、光学及力学性能的影响。利用表面轮廓仪、X射线衍射仪、原子力显微镜、分光光度计、椭偏仪及纳米压痕仪分析在不同溅射功率下制备的氧化钒薄膜的沉积速率、物相结构、表面形貌、紫外-近红外光透射率、折射率、吸光度以及硬度和弹性模量。结果表明,各功率参数下沉积的氧化钒薄膜的光透射率基本都大于80%,属于弱吸收透明膜。随溅射功率的增大,薄膜的沉积速率、硬度和可见光范围内的折射率都单调增大,而表面粗糙度则出现先增大后减小的变化。溅射功率对薄膜的晶体结构也有一定的影响。     

高调制度光致相变特性氧化钒薄膜太赫兹时域频谱研究

基于太赫兹(THz)时域频谱技术研究了飞秒激光激发下氧化钒纳米薄膜的光致绝缘体-金属相变特性。利用直流磁控溅射法在不同条件下制备了一系列蓝宝石基底上的氧化钒薄膜,通过测量薄膜发生光致相变后太赫兹波的透射率来评估成膜质量,得出在溅射时间60min不变的情况下,退火时间和退火温度分别为60s和560℃时可以得到性能非常良好的氧化钒薄膜。在上述最佳条件下制备的氧化钒薄膜的相变深度可达80%。利用薄膜近似计算了太赫兹波段氧化钒薄膜在光致相变过程中电导率的变化,计算结果表明电导率实部在103Ω-1·cm-1量级,并基于Drude模型得到了金属态氧化钒薄膜的复介电常数以及复折射率。在绝缘衬底上制备的具有明显阈值激发功率且相变深度大的氧化钒薄膜将在太赫兹调制器件中有重要应用。     

HfO2-SiO2混合膜力学性能

利用离子辅助电子束双源共蒸发工艺方法,制备了SiO2掺杂含量分别为0、13%、20%、30%、40%和100%的六组HfO2-SiO2混合膜。采用纳米压痕法测量了不同组分混合膜的杨氏模量和硬度,并研究了混合膜杨氏模量和硬度随SiO2含量增长的变化规律。结果显示,随着SiO2含量增加,混合膜杨氏模量和硬度均减小,双组分复合材料并联模型可以较好地拟合杨氏模量随混合膜SiO2含量变化关系。为了解释混合膜力学性能随SiO2含量变化规律,对混合膜进行了XRD测试,研究了混合膜微观结构与杨氏模量和硬度的关系,发现结晶对硬度影响显著,对杨氏模量影响较小;用Zygo干涉仪测量了样品的面形,获得了薄膜残余应力随SiO2含量的变化规律,表明SiO2掺杂能减小HfO2薄膜压应力。     

选区激光熔化成形多孔铝合金的显微组织及微观力学性能研究

选区激光熔化(SLM)技术是一种典型的快速成形技术,使用高能激光束熔化金属粉末,逐层堆积,直接成形复杂高性能金属零部件。为了对SLM成形多孔铝合金的性能进行研究,利用扫描电子显微镜、能量色散X射线荧光光谱、纳米压痕等测试手段分析了多孔铝合金的表面形貌、孔隙率、显微组织、相组成及微观力学性能。结果表明,激光功率为130 W时,孔隙率达到最大,多孔合金的显微组织细化,晶粒尺度达到纳米级别;激光功率变化对多孔铝合金的纳米硬度影响较大,但对弹性模量的影响不明显,其中α-Al相的弹性模量约为65 GPa,α-Al+Si共晶组织相的弹性模量约为85 GPa。     

显微拉曼光谱法对多孔硅热导率的研究

多孔硅优良的热学性能使其成为MEMS领域新兴的热绝缘材料。文中采用一种简便且无损的多孔硅热导率测量技术——显微拉曼光谱技术对电化学腐蚀法制备的不同孔隙率和厚度的多孔硅试样热导率进行了测量,结果表明在多孔硅的拉曼谱峰位置与其温度间存在线性对应关系。在所有样品中,厚度为110μm空隙率为65%的多孔硅显示出最好的绝热性能,其热导率为0.624W/mK。且随多孔硅孔隙率和厚度的减小,其热导率有迅速增加的趋势(厚度和孔隙率为9μm和40%时,其热导率升至25.32W/mK)。     

ZnS/PS复合体系的白光发射

用电化学方法制备了一定孔隙率的多孔硅(PS)样品,然后用脉冲激光沉积(PLD)法以多孔硅为衬底生长一层ZnS薄膜.ZnS的带隙较宽,对可见光是透明的,用适当波长的光激发,PS发射的橙红光可以透过ZnS薄膜,与ZnS的蓝绿光相叠加,得到了可见光区较宽的光致发光带,呈现较强的白光发射.用X射线衍射仪(XRD)和扫描电子显微镜(SEM)表征了ZnS薄膜的结构性质.结果表明,沉积的ZnS薄膜结晶质量较差,薄膜表面起伏不平,这是由于衬底PS的表面不平整所致.     

H2 carrier gas dependence of Young's modulus and hardness of chemical vapor deposited polycrystalline 3C-SiC thin films

This paper presents the mechanical properties of poly (polycrystalline) 3C-SiC thin films according to 0%, 7%, and 10% carrier gas (H₂) concentrations using nano-indentation. When H₂ concentration was 10%, it has been proved that the mechanical properties, Young's modulus, and hardness of poly 3C-SiC films are the best of them. In the case of 10% H₂ concentration, Young's Modulus and hardness were obtained as 367 and 36 GPa, respectively. The surface roughness according to H₂ concentrations was investigated by AFM (atomic force microscope). When H₂ concentration was 10%, the roughness of 3C-SiC thins was 9.92 nm, which is also the best of them. Therefore, in order to apply poly 3C-SiC thin films to MEMS (micro-electromechanical system) applications, H₂ concentration's rate should increase to obtain better mechanical properties and surface roughness.     

热处理对双离子束溅射SiO2薄膜力学及热力学特性的影响

光学薄膜的力学及热力学特性决定了光学系统性能的优劣。采用双离子束溅射的方法在硅110和肖特石英Q1基底上制备了SiO2薄膜,并对制备的膜层进行退火处理。系统研究了热处理前后SiO2薄膜的力学及热力学特性。研究结果表明,750℃退火条件下SiO2薄膜的弹性模量（Er）增加到72 GPa,膜层硬度增加到10 GPa。镀完后未经退火处理的SiO2薄膜表现为压应力,但是应力值在退火温度达到450℃以上时急剧降低,说明热处理有助于改善SiO2薄膜内应力。经退火处理的SiO2薄膜泊松比（vf）为0.18左右。退火前后SiO2薄膜的杨氏模量（Ef）都要比石英块体材料大,并且750℃退火膜层杨氏模量增加了50 GPa以上。550℃退火的SiO2薄膜热膨胀系数（f）从6.7810-7℃-1降到最小值5.2210-7℃-1。     

Morphological Control of Nanoporous Films by the Use of Functionalized Cyclodextrins as Porogens

Porous cyclic silsesquioxane (CSSQ) thin films containing nanopores (～ 2 nm) with low dielectric constant (k < 2.2), have been prepared by using various kinds of cyclodextrin (CD) derivatives as porogenic materials. The pore structure, including average pore size and interconnectivity, can be controlled by changing the functional groups of the cyclodextrin derivatives. The pore structure is found to be strongly related to the affinity of the functional groups between CD molecules. The electrical and mechanical properties of the porous thin films were monitored in order to determine the relationship between the pore structure and film properties. The mechanical properties of porous low‐k thin films (total porosity ～ 30 %) prepared with CD derivatives are found to be correlated with the pore interconnection length. The longer the deduced interconnection length in the thin film, the worse the mechanical properties (such as hardness and modulus) of the thin film, even though the porogen‐induced pore diameters are very small (～ 2 nm).     

Internal stress and elastic modulus measurements on micromachined3C-SiC thin films

Fabrication of epitaxial 3C-SiC microstructures by bulk micromachining of the underlying silicon substrate was investigated. Initial studies of the mechanical properties of epitaxial 3C-SiC films deposited on silicon were carried out on microstructures fabricated by bulk micromachining of the silicon substrate to evaluate the potential of these films for micromechanics. Residual stress and biaxial modulus of 3C-SiC films were measured by load-deflection measurements of suspended diaphragms. The film's residual stress was tensile with an average of 212 MPa, while the in-plane biaxial modulus averaged 441 GPa     

Ultralow Dielectric Constant Tetravinyltetramethylcyclotetrasiloxane Films Deposited by Initiated Chemical Vapor Deposition (iCVD)

Simultaneous improvement of mechanical properties and lowering of the dielectric constant occur when films grown from the cyclic monomer tetravinyltetramethylcyclotetrasiloxane (V4D4) via initiated chemical vapor deposition (iCVD) are thermally cured in air. Clear signatures from silsesquioxane cage structures in the annealed films appear in the Fourier transform IR (1140 cm^?1) and Raman (1117 cm^?1) spectra. The iCVD method consumes an order of magnitude lower power density than the traditional plasma‐enhanced CVD, thus preserving the precursor's delicate ring structure and organic substituents in the as‐deposited films. The high degree of structural retention in the as‐deposited film allows for the beneficial formation of intrinsically porous silsesquioxane cages upon annealing in air. Complete oxidation of the silicon creates ‘Q’ groups, which impart greater hardness and modulus to the films by increasing the average connectivity number of the film matrix beyond the percolation of rigidity. The removal of labile hydrocarbon moieties allows for the oxidation of the as‐deposited film while simultaneously inducing porosity. This combination of events avoids the typical trade‐off between improved mechanical properties and higher dielectric constants. Films annealed at 410 °C have a dielectric constant of 2.15, and a hardness and modulus of 0.78 and 5.4 GPa, respectively. The solvent‐less and low‐energy nature of iCVD make it attractive from an environmental safety and health perspective.     

Air-Gaps for High-Performance On-Chip Interconnect Part I: Improvement in Thermally Decomposable Template

The incorporation of air-cavities (i.e., air-gaps) as the intralevel dielectric in integrated circuits (ICs) can provide an ultralow-k solution, especially at the 32 nm technology node and beyond. Air-gaps can be created by the templating method using norbornene (NB)-based sacrificial polymers. However, it has been found that the hardness and modulus of the templating material is critical to achieving mechanical fidelity of the structure during processing. As a result, stiffer sacrificial polymers lead to higher yield. In this study, tetracyclododecene (TD)-based sacrificial polymers were investigated and compared with norbornene-based (NB)-based polymers. Nanoindentation experiments showed that thin films of TD-based sacrificial polymers were harder than NB-based sacrificial polymers. The effect of the modulus and hardness on the process repeatability was quantitatively evaluated by comparing the straightness of 50-nm-wide lines of TD- and NB-based sacrificial polymers. It was shown that the TD-based polymer structures were straighter and had better reproducibility than those of NB-based polymers due to an increase in hardness and modulus. The thermal decomposition properties of TD-based polymers were similar to their NB-based counterparts. Both TD- and NB-based polymers were thermally stable at 300°C and the decomposition residues were less than 1% of the original weight. The thickness of the residue (solid reaction byproducts) from thin TD films was as low as 2.1 nm (depending on the atmosphere quality) and the residue was hydrophobic.     

Stiff and Transparent Multilayer Thin Films Prepared Through Hydrogen‐Bonding Layer‐by‐Layer Assembly of Graphene and Polymer

Due to their exceptional orientation of 2D nanofillers, layer‐by‐layer (LbL) assembled polymer/graphene oxide thin films exhibit unmatched mechanical performance relative to any conventionally produced counterparts with similar composition. Unprecedented mechanical property improvement, by replacing graphene oxide with pristine graphene, is demonstrated in this work. Polyvinylpyrrolidone‐stabilized graphene platelets are alternately deposited with poly(acrylic acid) using hydrogen bonding assisted LbL assembly. Transmission electron microscopy imaging and the Halpin‐Tsai model are used to demonstrate, for the first time, that intact graphene can be processed from water to generate polymer nanocomposite thin films with simultaneous parallel‐alignment, high packing density, and exfoliation. A multilayer thin film with only 3.9 vol% of highly exfoliated, and structurally intact graphene, increases the elastic modulus (E) of a polymer multilayer thin film by 322% (from 1.41 to 4.81 GPa), while maintaining visible light transmittance of ≈90%. This is one of the greatest improvements in elastic modulus ever reported for a graphene‐filled polymer nanocomposite with a glassy (E > 1 GPa) matrix. The technique described here provides a powerful new tool to improve nanocomposite properties (mechanical, gas transport, etc.) that can be universally applied to a variety of polymer matrices and 2D nanoplatelets.     

Nanoindentation on SnAgCu lead-free solder joints and analysis

The lead-free SnAgCu (SAC) solder joint on copper pad with organic solderability preservative (Cu-OSP) and electroless nickel and immersion gold (ENIG) subjected to thermal testing leads to intermetallic growth. It causes corresponding reliability concerns at the interface. Nanoindentation characterization on SnAgCu solder alloy, intermetallic compounds (IMCs), and the substrates subjected to thermal aging is reported. The modulus and hardness of thin IMC layers were measured by nanoindentation continuous stiffness measurement (CSM) from planar IMC surface. When SAC/Ni(Au) solder joints were subject to thermal aging, the Young’s modulus of the NiCuSn IMC at the SAC/ENIG specimen changed from 207 GPa to 146 GPa with different aging times up to 500 h. The hardness decreased from 10.0 GPa to 7.3 GPa. For the SAC/Cu-OSP reaction couple, the Young’s modulus of Cu₆Sn₅ stayed constant at 97.0 GPa and hardness about 5.7 GPa. Electron-probe microanalysis (EPMA) was used to thermal aging. The creep effect on the measured result was analyzed when measuring SnAgCu solder; it was found that the indentation penetration, and thus the hardness, is loading rate dependent. With the proposed constant P/P experiment, a constant indentation strain rate h/h and hardness could be achieved. The log-log plot of indentation strain rate versus hardness for the data from the constant P/P experiments yields a slope of 7.52. With the optimized test method and CSM Technique, the Modulus of SAC387 solder alloy and all the layers in a solder joint were investigated.     

W/Al双层膜系的纳米压痕实验及有限元仿真

采用磁控溅射法在CAT.No.7101玻璃基底上沉积了W/Al双层金属膜,并对其进行纳米压痕实验。利用非线性有限元法对压痕过程进行仿真,分析了膜基体系的应力分布。结果表明:磁控溅射法制备的薄膜组织均匀、力学性能好。W/Al双层金属膜系中的W薄膜的弹性模量与硬度平均值分别为75.4335GPa、6.206GPa,其值与块状W材料的相应参数差别较大。仿真曲线与实验结果基本相符,能够反映出膜基体系的力学状态以及应力分布规律。