Name: fabrication of low temperature carbon nanotube vertical interconnects compatible with semiconductor technology
Uploaded: 2015-12-07T13:00:00.000+00:00
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Description: Watch this Scientific Journal Video about Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology at JoVE.com

Part of the work has been performed in the project JEMSiP_3D, which is funded by the Public Authorities in France, Germany, Hungary, The Netherlands, Norway and Sweden, as well as by the ENIAC Joint Undertaking. The authors would like to thank the Dimes Technology Centre staff for processing support.

注意:使用前请咨询所有相关的材料安全数据表（MSDS）。几个在该制造工艺中使用的化学品是剧毒和致癌性。相比，他们的大部分对手纳米材料可能有额外的危险。用设备，化学品或纳米材料工作时，包括利用工程控制（通风柜）和个人防护装备（防护眼镜，手套，无尘服）的请使用一切适当的安全措施。 1.对准标记定义为光刻<ol><li>开始与单面抛光的工业级硅（100）晶片与n或p型掺杂。 </li><li>外套与正性光刻胶的1.4微米的晶片。在130℃下进行90秒的六甲基二硅氮烷（HMDS）处理，以促进光致抗蚀剂，接着在晶片上的冷板，旋涂以适当的速度（3500转）的冷却的粘接性，和一个90秒的软烘烤一牛逼95℃。 </li><li>使用光刻掩模和曝光工具暴露对准标记，曝光量为120mJ / cm 2以下。 </li><li>执行一个水坑的发展过程。执行90秒115℃曝光后烘烤，接着60秒显影用显影剂和90秒的硬烘烤，在100℃以固化该抗蚀剂。 </li><li>用显微镜检查，如果在抗蚀剂中的开口是正确的尺寸。 </li><li>蚀刻用Si氯等离子体蚀刻的120纳米。该厚度提供了良好的对比度在这项工作中所用的曝光工具的自动对准系统。例如使用感应耦合等离子体（ICP）:40分之20SCCM 的 O 2 / CF 4，5毫乇，五百分之六十〇 W¯¯压板/ ICP RF功率，10秒氧化物突破蚀刻，接着四十零分之八十SCCM Cl 2中/ HBr的，60毫托，五百分之二十〇W¯¯压板/ ICP的射频功率，35秒硅蚀刻。 </li><li>使用氧等离子体汽提塔，除去光致抗蚀剂（1千瓦，400 SCCM O 2与endpoINT探测和2分钟过腐蚀）。作为光致抗蚀剂是由像丙酮等离子体正常溶剂固化，不能使用。 </li><li>清洁晶圆。首先把它们用于在99％HNO 3，接着漂洗在去离子水中10分钟，直到水的电阻率是5兆欧（有机清洁）。在此之后清洗晶片在110℃下在65％HNO 3 10分钟，随后用DI水漂洗直到水的电阻率是5兆欧（金属清洁）。使用冲洗器干燥器来干燥的晶片。 </li></ol> 2.底部金属和层间电介质沉积<ol><li>使用磁控溅射沉积经由测试的底部金属层。一叠三个金属层需要被沉积:500纳米的Ti，TiN的为50nm，和100nm的钛。第一Ti层是降低堆栈的电阻，使TiN是实际的支撑层为碳纳米管的生长，并且顶Ti为防止等离子体损伤使TiN蚀刻SiO 2层12时</suP&gt;。执行使用纯Ti靶，用Ar等离子体，在350℃的基板温度的Ti溅射。对于TiN的反应性溅射的Ar使用和 N 2的组合，再次在350℃衬底温度下进行。 </li><li>使用等离子体增强化学汽相沉积（PECVD），沉积1微米厚的层的 SiO 2。这里原硅酸四乙酯（TEOS）用作前体在350℃的台板温度。 <ol><li>检查SiO 2层的使用适当的工具的厚度，例如是反射或椭圆仪。 </li></ol></li><li>外套晶片与1.4微米阳性光致抗蚀剂的，从一个90秒的HMDS处理在130℃，接着在晶片上的冷板，旋涂以适当的速度（3500转）冷却，并以90秒的软烘烤在95℃下。 </li><li>使用光刻掩模和曝光工具，露出开口的所需图案，这将在后面蚀刻到SiO 2的吨Ó形成通孔，对准到对准标记，曝光量140毫焦/厘米2。 </li><li>执行开始以90秒115℃的后曝光烘烤的单个水坑开发过程，接着60秒显影用显影剂和90秒的硬烘烤，在100℃。 </li><li>用显微镜检查，如果在抗蚀剂中的开口是正确的尺寸和如果叠加到对准标记是正确的。 </li><li>等离子体蚀刻接触开口中的 SiO 2。例如，使用三极管等离子刻蚀机与C 2 F 6 /瑞郎3一百四十四分之三十六SCCM在180毫托和300瓦的射频功率。如果需要的话，进行一个测试晶片上的蚀刻速率试验，以最小化过蚀刻至5％-10％的时间。 注意:虽然在Ti是耐在此氟化学反应蚀刻，长时间暴露于等离子体，将导致在Ti层的物理蚀刻。如果TiN层暴露于等离子体，这将有负面influen铈对碳纳米管12的生长。不使用湿法蚀刻，因为这将导致在开口过多加宽，使得顶部金属部分4有问题的。 </li><li>在0.55％的HF去除牺牲Ti层通过湿法蚀刻进行60秒。蚀刻冲洗用DI水晶片直到水电阻率之后是5兆欧并使用冲洗器干燥器来干燥的晶片。 注意:使用显微镜它能如果在Ti层被蚀刻进行检查，在TiN层将具有金棕色颜色，而Ti为金属灰色。 </li></ol> 3.催化剂沉积和碳纳米管的生长<ol><li>蒸发Co的5纳米使用电子束蒸发器。抽空直到至少2×10 -6乇 ，以及沉积，以除去任何水膜前加热下使用真空灯晶片至60℃。光致抗蚀剂用于限定接触开口被保持在晶片上，以提供在所述的 SiO 2的催化剂，以接触开口的自对准。 </li><li>删除接触开口外联合通过剥离。钴发现四氢呋喃（THF），得到最好的剥离结果和生长在低温下。N-甲基 -2-吡咯烷酮（NMP），这是以前用于铁蒸发后剥离，发现损坏联合太这样的程度，以防止任何对准的碳纳米管的生长。把该晶片15分钟，在超声浴用THF在35℃。冲洗DI水5分钟，干燥用旋转器或氮气枪。 </li><li>检查显微镜下的晶圆检查光刻胶残渣。如果残留物留执行THF更长的超声处理，并选择使用一种特殊的柔软的棉拭子剥离目的而手动擦去残留物。 </li><li>采用低压化学气相沉积（LPCVD）进行碳纳米管的生长。通过加入50sccm的C 2 H 2 8分钟的预退火，在350℃用700标准立方厘米的 H 2在80毫巴，随后碳纳米管的生长:使用以下配方。在350℃，60增长的分给了大约1微米的碳纳米管。如有必要，执行测试的生长来调节高度，这应该是相同的厚度与SiO 2层。冷却反应器，并清除，使用N 2。 </li><li>使用扫描电子显微镜，或通过制备的横截面，以检查CNT的高度的开口内下45°倾斜。 </li><li>检查使用拉曼光谱，以确定在CNT 18的结晶性的样品。 </li></ol> 4.顶边金属化<ol><li>使用磁控溅射沉积顶部金属。如Ti是一个良好的金属用于接触碳纳米管19， ​​第一溅射100nm的钛，接着为2μm的Al（1％的Si）的不破坏真空。 </li><li>外套与3.1微米阳性光致抗蚀剂具有更高的粘度，从一个90秒的HMDS处理在130℃，接着在晶片上的冷板，旋涂以3000rpm的冷却，并以90秒的软烘烤在晶片95C。 </li><li>使用光刻掩模和曝光工具暴露对准到对准标记的顶部金属图案，曝光量420毫焦/厘米2，-1焦点。 </li><li>执行一个水坑的发展过程。这开始于一个90秒115℃曝光后烘烤，接着使用显影剂和90秒的硬烘烤，在100℃下60秒显影。 </li><li>用显微镜检查，如果在抗蚀剂的线是正确的尺寸和如果叠加到标记是正确的。 </li><li>蚀刻使用氯离子腐蚀的钛/铝堆栈。例如使用感应耦合等离子体:40分之30SCCM Cl 2中/ HBr的，5毫乇，五百分之四十零W¯¯滚筒/ ICP RF功率与终点探测和80％过蚀刻使用15/30 SCCM Cl 2中/ HBr的。 </li><li>使用氧等离子体汽提塔，除去光致抗蚀剂（1千瓦，400 SCCM O 2与端点检测和2分钟过腐蚀）。如果金属覆盖面不完整（ 即每年大约有针孔CNT）使用有机溶剂（如NMP）中，除去光致抗蚀以防止等离子体损坏碳纳米管。 </li><li>清洁晶圆。把它们用于在99％HNO 3，随后用DI水漂洗10分钟，直到水的电阻率是5兆欧（有机清洁）。使用冲洗器干燥器来干燥的晶片。 </li></ol> 5.测量<ol><li>使用根据制造商的说明用扫描电子显微镜来检查晶片的顶部金属化。 注意:如果必要的晶片可以机械地切割，以便通过使用90°的样品倾斜，从而导致在图像进行检查的完整的CNT，如图3由于样品是导电的，必须使用没有额外的处理步骤和该样品可以直接安装到扫描电镜。通常，可以使用的15或20千伏高电压的加速，但是，如果SiO 2层被充电了太多这可以减小吨O 5千伏。 </li><li>执行4点使用与半导体参数分析仪的组合的探针站，如图1和 Vollebregt 等人 16所述探头IV测量。 注意:通常从-0.5到0.5伏的电压扫描就足够了，如通过一个互连的电势降的理想是小的。通过使用4点探针设置探针接触针，并将设置的配线电阻的接触电阻被省略。 </li></ol>

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The authors have nothing to disclose.

图1显示制造在这项工作中的结构的示意图，并且其被用于4点探针测量。作为电位通过探针携带没有电流测量，准确的电位降（Vħ-V L），在中央CNT束及其触点的金属可以被测量。更大直径的CNT束被用于接触从接触垫的底TiN层，以减少用于当前迫使探头的总电阻并最大化在中央CNT束中的电势降。 如从图2可以看出，在CNT被成功地生...

铜和钨，这是目前用于国家的最先进的非常大规模集成电路（VLSI）技术的互连金属，正在接近的可靠性和电导率1项自己的体能极限。而向下缩放晶体管通常可以提高它们的性能，但实际上增加了电阻和互连的电流密度。这导致互连支配在延迟和功耗2方面的集成电路（IC）的性能。 碳纳米管（CNT）被建议作为替代的Cu和W的金属化，特别是对垂直互连（通孔），为的CNT可以很容易地被生长垂直3。碳纳米管已被证明具有优良的电可靠性，允许高达1000倍更高的电流密度比铜4。此外，CNT不会从表面和晶界散射受到影响，这是增加第r铜esistivity在纳米尺度5。最后，碳纳米管已经被证明是优良的热导体 6，其中所用的热管理在VLSI芯片帮助。 对于碳纳米管在VLSI技术成功的集成是很重要的，对于碳纳米管的生长过程是用半导体制造兼容。这要求使用的材料和这被认为是兼容和可扩展的，以大规模的制造设备的CNT（&lt;400℃）的低温生长。虽然CNT测试过孔许多实例已被证明在文献中7,8,9,10,11,12,13,14，大多数这些使用铁作为催化剂，它被认为是在集成电路中的污染物的制造15。此外，在许多这些作品中使用的生长温度高于400℃的上限要高得多。优选的CNT甚至应种植在350℃以下，为了让拥有现代化的低κ电介质或灵活的集成基材。 在这里，我们提出了一个可扩展的方法生长碳纳米管在温度低至350℃下使用钴作为催化剂 16。该方法是用于制造不同电结构由垂直对准的CNT的集成电路，从互连和电极，以超级电容器和场致发射装置的兴趣。钴催化剂金属通常用在集成电路制造为硅化物的17的制造中，而氮化钛是一种经常用于阻挡材料7。此外，我们证明了制造CNT的测试孔，而只能使用从标准的半导体制造技术的过程。由此，CNT测试过孔被制造，检查通过扫描电子显微镜（SEM）和拉曼光谱，并且电特征。

<table><tbody><tr><td>Si (100) wafer 4&quot;</td><td>International Wafer Service</td><td></td><td>Resisitivity: 2-5 m&amp;Omega;-cm, thickness: 525 &amp;micro;m&amp;nbsp;</td></tr><tr><td>Ti-sputter target (99.995% purity)</td><td>Praxair</td><td></td><td></td></tr><tr><td>Al (1% Si)-sputter target (99.999% purity)</td><td>Praxair</td><td></td><td></td></tr><tr><td>Co (99.95% purity)</td><td>Kurt J. Lesker</td><td></td><td></td></tr><tr><td>SPR3012 positive photoresist</td><td>Dow Electronic Materials</td><td></td><td></td></tr><tr><td>MF-322 developer</td><td>Dow Electronic Materials</td><td></td><td></td></tr><tr><td>HNO&lt;sub&gt;3&lt;/sub&gt; (99.9%)</td><td>KMG Ultra Pure Chemicals</td><td></td><td></td></tr><tr><td>HNO&lt;sub&gt;3&lt;/sub&gt; (69.5%)</td><td>KMG Ultra Pure Chemicals</td><td></td><td></td></tr><tr><td>HF 0.55%</td><td>Honeywell</td><td></td><td></td></tr><tr><td>Tetrahydrofuran</td><td>JT Baker</td><td></td><td></td></tr><tr><td>Acetone</td><td>Sigma-Aldrich</td><td></td><td></td></tr><tr><td>ECI3027 positive photoresist</td><td>AZ</td><td></td><td></td></tr><tr><td>Tetraethyl orthosilicate (TEOS)</td><td>Praxair</td><td></td><td></td></tr><tr><td>N&lt;sub&gt;2&lt;/sub&gt; (99.9990%)</td><td>Praxair</td><td></td><td></td></tr><tr><td>O&lt;sub&gt;2&lt;/sub&gt; (99.9999%)</td><td>Praxair</td><td></td><td></td></tr><tr><td>CF&lt;sub&gt;4&lt;/sub&gt; (99.9970%)</td><td>Praxair</td><td></td><td></td></tr><tr><td>Cl&lt;sub&gt;2&lt;/sub&gt; (99.9900%)</td><td>Praxair</td><td></td><td></td></tr><tr><td>HBr (99.9950%)</td><td>Praxair</td><td></td><td></td></tr><tr><td>Ar (99.9990%)</td><td>Praxair</td><td></td><td></td></tr><tr><td>C&lt;sub&gt;2&lt;/sub&gt;F&lt;sub&gt;6&lt;/sub&gt; (99.9990%)</td><td>Praxair</td><td></td><td></td></tr><tr><td>CHF&lt;sub&gt;3&lt;/sub&gt; (99.9950%)</td><td>Praxair</td><td></td><td></td></tr><tr><td>H&lt;sub&gt;2&lt;/sub&gt; (99.9950%)</td><td>Praxair</td><td></td><td></td></tr><tr><td>C&lt;sub&gt;2&lt;/sub&gt;H&lt;sub&gt;2&lt;/sub&gt; (99.6000%)</td><td>Praxair</td><td></td><td></td></tr><tr><td>EVG 120 coater/developer</td><td>EVG</td><td></td><td></td></tr><tr><td>ASML PAS5500/80 waferstepper</td><td>ASML</td><td></td><td></td></tr><tr><td>SPTS &amp;Omega;mega 201 plasma etcher</td><td>SPTS</td><td></td><td>Used for Si and metal etching</td></tr><tr><td>SPTS &amp;Sigma;igma sputter coater</td><td>SPTS</td><td></td><td></td></tr><tr><td>Novellus Concept One PECVD</td><td>LAM</td><td></td><td></td></tr><tr><td>Drytek 384T plasma etcher</td><td>LAM</td><td></td><td>Used for oxide etching</td></tr><tr><td>CHA Solution e-beam evaporator</td><td>CHA</td><td></td><td></td></tr><tr><td>AIXTRON BlackMagic Pro CVD tool</td><td>AIXTRON</td><td></td><td>Carbon nanotube growth</td></tr><tr><td>Philips XL50 scanning electron microscope</td><td>FEI</td><td></td><td></td></tr><tr><td>Tepla 300</td><td>PVA TePla</td><td></td><td>Resist plasma stripper</td></tr><tr><td>Avenger rinser dryer</td><td>Microporcess Technologies</td><td></td><td></td></tr><tr><td>Leitz MPV-SP reflecometer</td><td>Leitz</td><td></td><td></td></tr><tr><td>Renishaw inVia Raman spectroscope</td><td>Renishaw</td><td></td><td></td></tr><tr><td>Agilent 4156C parameter spectrum analyzer</td><td>Agilent</td><td></td><td></td></tr><tr><td>Cascade Microtech probe station</td><td>Cascade Microtech</td><td></td><td></td></tr></tbody></table>

fabrication of low temperature carbon nanotube vertical interconnects compatible with semiconductor technology

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive thin-films. Due to the low growth temperature, the process allows integration with modern low-&#954; dielectrics and some flexible substrates. The process is compatible with standard semiconductor fabrication, and a method for the fabrication of electrical 4-point probe test structures for vertical interconnect test structures is presented. Using scanning electron microscopy the morphology of the CNT bundles is investigated, which demonstrates vertical alignment of the CNT and can be used to tune the CNT growth time. With Raman spectroscopy the crystallinity of the CNT is investigated. It was found that the CNT have many defects, due to the low growth temperature. The electrical current-voltage measurements of the test vertical interconnects displays a linear response, indicating good ohmic contact was achieved between the CNT bundle and the top and bottom metal electrodes. The obtained resistivities of the CNT bundle are among the average values in the literature, while a record-low CNT growth temperature was used.

在这项工作中所用的测量结构的设计可以在图1中找到。通过采用这样的结构的碳纳米管束电阻和金属碳纳米管接触电阻的测量可以精确地确定，因为探针和导线电阻被规避。束的电阻为所述CNT束的质量和密度的测量。为了确定不同长度的接触电阻束应测量。 碳纳米管的典型SEM图像，在350℃生长用于从金属化之前的顶部取在45°倾斜60分钟，</stron...

Watch this Scientific Journal Video about Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology at JoVE.com

Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology

A method for the growth of low temperature vertically-aligned carbon nanotubes, and the subsequent fabrication of vertical interconnect electrical test structures using semiconductor fabrication is presented.

低温碳纳米管垂直互连的制作兼容半导体技术

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive ...

fabrication-low-temperature-carbon-nanotube-vertical-interconnects

Universidad de Cartagena UDEC

Research

JoVE Journal

Engineering

7.6K 次观看.  Delft University of Technology. A method for the growth of low temperature vertically-aligned carbon nanotubes, and the subsequent fabrication of vertical interconnect electrical test structures using semiconductor fabrication is presented.

视频: Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology

Fabrication, Densification, and Replica Molding of 3D Carbon Nanotube Microstructures

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques 1, 2, and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. 
Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT microstructures, significantly increases the packing density of CNTs. This process enables directed transformation of vertical CNT microstructures into straight, inclined, and twisted shapes, which have robust mechanical properties exceeding those of typical microfabrication polymers. This in turn enables formation of nanocomposite CNT master molds by capillary-driven infiltration of polymers. The replica structures exhibit the anisotropic nanoscale texture of the aligned CNTs, and can have walls with sub-micron thickness and aspect ratios exceeding 50:1. Integration of CNT microstructures in fabrication offers further opportunity to exploit the electrical and thermal properties of CNTs, and diverse capabilities for chemical and biochemical functionalization 3.

We present methods for fabrication of patterned microstructures of vertically aligned carbon nanotubes (CNTs), and their use as master molds for production of polymer microstructures with organized nanoscale surface texture. The CNT forests are densified by condensation of solvent onto the substrate, which significantly increases their packing density and enables self-directed formation of 3D shapes.

制备，致密，副本三维碳纳米管微结构成型

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip ...

科研

工程学

Fabricating Nanogaps by Nanoskiving

There are several methods of fabricating nanogaps with controlled spacings, but the precise control over the sub-nanometer spacing between two electrodes-and generating them in practical quantities-is still challenging. The preparation of nanogap electrodes using nanoskiving, which is a form of edge lithography, is a fast, simple and powerful technique. This method is an entirely mechanical process which does not include any photo- or electron-beam lithographic steps and does not require any special equipment or infrastructure such as clean rooms. Nanoskiving is used to fabricate electrically addressable nanogaps with control over all three dimensions; the smallest dimension of these structures is defined by the thickness of the sacrificial layer (Al or Ag) or self-assembled monolayers. These wires can be manually positioned by transporting them on drops of water and are directly electrically-addressable; no further lithography is required to connect them to an electrometer.

The fabrication of electrically addressable, high-aspect-ratio (> 1000:1) metal nanowires separated by gaps of single nanometers using either sacrificial layers of aluminum and silver or self-assembled monolayers as templates is described. These nanogap structures are fabricated without a clean room or any photo- or electron-beam lithographic processes by a form of edge lithography known as nanoskiving.

制造由Nanoskiving Nanogaps的

There are several methods of fabricating nanogaps with controlled spacings, but the precise control over the sub-nanometer spacing between two ...

化学

Dry Oxidation and Vacuum Annealing Treatments for Tuning the Wetting Properties of Carbon Nanotube Arrays

In this article, we describe a simple method to reversibly tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays. Here, CNT arrays are defined as densely packed multi-walled carbon nanotubes oriented perpendicular to the growth substrate as a result of a growth process by the standard thermal chemical vapor deposition (CVD) technique.1,2 These CNT arrays are then exposed to vacuum annealing treatment to make them more hydrophobic or to dry oxidation treatment to render them more hydrophilic. The hydrophobic CNT arrays can be turned hydrophilic by exposing them to dry oxidation treatment, while the hydrophilic CNT arrays can be turned hydrophobic by exposing them to vacuum annealing treatment. Using a combination of both treatments, CNT arrays can be repeatedly switched between hydrophilic and hydrophobic.2 Therefore, such combination show a very high potential in many industrial and consumer applications, including drug delivery system and high power density supercapacitors.3-5
The key to vary the wettability of CNT arrays is to control the surface concentration of oxygen adsorbates. Basically oxygen adsorbates can be introduced by exposing the CNT arrays to any oxidation treatment. Here we use dry oxidation treatments, such as oxygen plasma and UV/ozone, to functionalize the surface of CNT with oxygenated functional groups. These oxygenated functional groups allow hydrogen bond between the surface of CNT and water molecules to form, rendering the CNT hydrophilic. To turn them hydrophobic, adsorbed oxygen must be removed from the surface of CNT. Here we employ vacuum annealing treatment to induce oxygen desorption process. CNT arrays with extremely low surface concentration of oxygen adsorbates exhibit a superhydrophobic behavior.

This article describes a simple method to fabricate vertically aligned carbon nanotube arrays by CVD and to subsequently tune their wetting properties by exposing them to vacuum annealing or dry oxidation treatment.

干式氧化及真空退火处理调整的润湿性能的碳纳米管阵列

In this article, we describe a simple method to reversibly  tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays.  Here, CNT ...

Ultrahigh Density Array of Vertically Aligned Small-molecular Organic Nanowires on Arbitrary Substrates

In recent years &pi;-conjugated organic semiconductors have emerged as the active material in a number of diverse applications including large-area, low-cost displays, photovoltaics, printable and flexible electronics and organic spin valves. Organics allow (a) low-cost, low-temperature processing and (b) molecular-level design of electronic, optical and spin transport characteristics. Such features are not readily available for mainstream inorganic semiconductors, which have enabled organics to carve a niche in the silicon-dominated electronics market. The first generation of organic-based devices has focused on thin film geometries, grown by physical vapor deposition or solution processing. However, it has been realized that organic nanostructures can be used to enhance performance of above-mentioned applications and significant effort has been invested in exploring methods for organic nanostructure fabrication.	
A particularly interesting class of organic nanostructures is the one in which vertically oriented organic nanowires, nanorods or nanotubes are organized in a well-regimented, high-density array. Such structures are highly versatile and are ideal morphological architectures for various applications such as chemical sensors, split-dipole nanoantennas, photovoltaic devices with radially heterostructured "core-shell" nanowires, and memory devices with a cross-point geometry. Such architecture is generally realized by a template-directed approach. In the past this method has been used to grow metal and inorganic semiconductor nanowire arrays. More recently &pi;-conjugated polymer nanowires have been grown within nanoporous templates. However, these approaches have had limited success in growing nanowires of technologically important &pi;-conjugated small molecular weight organics, such as tris-8-hydroxyquinoline aluminum (Alq3), rubrene and methanofullerenes, which are commonly used in diverse areas including organic displays, photovoltaics, thin film transistors and spintronics.	
Recently we have been able to address the above-mentioned issue by employing a novel "centrifugation-assisted" approach. This method therefore broadens the spectrum of organic materials that can be patterned in a vertically ordered nanowire array. Due to the technological importance of Alq3, rubrene and methanofullerenes, our method can be used to explore how the nanostructuring of these materials affects the performance of aforementioned organic devices. The purpose of this article is to describe the technical details of the above-mentioned protocol, demonstrate how this process can be extended to grow small-molecular organic nanowires on arbitrary substrates and finally, to discuss the critical steps, limitations, possible modifications, trouble-shooting and future applications.

We report a simple method for fabricating an ultrahigh density array of vertically ordered small-molecular organic nanowires. This method allows for synthesis of complex heterostructured hybrid nanowire geometries, which can be inexpensively grown on arbitrary substrates. These structures have potential applications in organic electronics, optoelectronics, chemical sensing, photovoltaics and spintronics.

超高密度垂直对齐的任意基质的小分子有机纳米线阵列

In  recent years &pi;-conjugated  organic semiconductors have emerged as the active material in a number of  diverse applications including large-area, ...

Manufacturing of Three-dimensionally Microstructured Nanocomposites through Microfluidic Infiltration

Microstructured composite beams reinforced with complex three-dimensionally (3D) patterned nanocomposite microfilaments are fabricated via nanocomposite in&#64257;ltration of 3D interconnected microfluidic networks. The manufacturing of the reinforced beams begins with the fabrication of microfluidic networks, which involves layer-by-layer deposition of fugitive ink filaments using a dispensing robot, filling the empty space between filaments using a low viscosity resin, curing the resin and finally removing the ink.&#160;Self-supported 3D structures with other geometries and many layers (e.g.&#160;a few hundreds layers) could be built using this method. The resulting tubular micro&#64258;uidic networks are then infiltrated with thermosetting nanocomposite suspensions containing nanofillers (e.g.&#160;single-walled carbon nanotubes), and subsequently cured. The infiltration is done by applying a pressure gradient between two ends of the empty network (either by applying a vacuum or vacuum-assisted microinjection). Prior to the infiltration, the nanocomposite suspensions are prepared by dispersing nanofillers into polymer matrices using ultrasonication and three-roll mixing methods. The nanocomposites (i.e.&#160;materials infiltrated) are then solidified under UV exposure/heat cure, resulting in a 3D-reinforced composite structure. The technique presented here enables the design of functional nanocomposite macroscopic products for microengineering applications such as actuators and sensors.

Three-dimensional (3D) microstructured composite beams are fabricated through the directed and localized infiltration of nanocomposites into 3D porous microfluidic networks. The flexibility of this manufacturing method enables the utilization of different thermosetting materials and nanofillers in order to achieve a variety of functional 3D reinforced nanocomposite macroscopic products.

通过微流体渗透制备三维微结构纳米复合材料的制造

Microstructured composite beams reinforced with complex three-dimensionally (3D) patterned nanocomposite microfilaments are fabricated via nanocomposite ...

Fabrication of Uniform Nanoscale Cavities via Silicon Direct Wafer Bonding

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned and bonded silicon wafers. Unlike confinements in porous materials often used for these types of experiments3, bonded wafers provide predesigned uniform spaces for confinement. The geometry of each cell is well known, which removes a large source of ambiguity in the interpretation of data.
Exceptionally flat, 5 cm diameter, 375 &#181;m thick Si wafers with about 1 &#181;m variation over the entire wafer can be obtained commercially (from Semiconductor Processing Company, for example). Thermal oxide is grown on the wafers to define the confinement dimension in the z-direction. A pattern is then etched in the oxide using lithographic techniques so as to create a desired enclosure upon bonding. A hole is drilled in one of the wafers (the top) to allow for the introduction of the liquid to be measured. The wafers are cleaned2 in RCA solutions and then put in a microclean chamber where they are rinsed with deionized water4. The wafers are bonded at RT and then annealed at ~1,100 &#176;C. This forms a strong and permanent bond. This process can be used to make uniform enclosures for measuring thermal and hydrodynamic properties of confined liquids from the nanometer to the micrometer scale.

A method for permanently bonding two silicon wafers so as to realize a uniform enclosure is described. This includes wafer preparation, cleaning, RT bonding, and annealing processes. The resulting bonded wafers (cells) have uniformity of enclosure ~1%1,2. The resulting geometry allows for measurements of confined liquids and gasses.

通过硅直接晶圆粘接制造均匀纳米级腔

Measurements of the heat capacity and superfluid fraction of confined 4He have been performed near the lambda transition using lithographically patterned ...

Fabrication of Carbon Nanotube High-Frequency Nanoelectronic Biosensor for Sensing in High Ionic Strength Solutions

The unique electronic properties and high surface-to-volume ratios of single-walled carbon nanotubes (SWNT) and semiconductor nanowires (NW) 1-4 make them good candidates for high sensitivity biosensors. When a charged molecule binds to such a sensor surface, it alters the carrier density5 in the sensor, resulting in changes in its DC conductance. However, in an ionic solution a charged surface also attracts counter-ions from the solution, forming an electrical double layer (EDL). This EDL effectively screens off the charge, and in physiologically relevant conditions ~100 millimolar (mM), the characteristic charge screening length (Debye length) is less than a nanometer (nm). Thus, in high ionic strength solutions, charge based (DC) detection is fundamentally impeded6-8.
We overcome charge screening effects by detecting molecular dipoles rather than charges at high frequency, by operating carbon nanotube field effect transistors as high frequency mixers9-11. At high frequencies, the AC drive force can no longer overcome the solution drag and the ions in solution do not have sufficient time to form the EDL. Further, frequency mixing technique allows us to operate at frequencies high enough to overcome ionic screening, and yet detect the sensing signals at lower frequencies11-12. Also, the high transconductance of SWNT transistors provides an internal gain for the sensing signal, which obviates the need for external signal amplifier.
Here, we describe the protocol to (a) fabricate SWNT transistors, (b) functionalize biomolecules to the nanotube13, (c) design and stamp a poly-dimethylsiloxane (PDMS) micro-fluidic chamber14 onto the device, and (d) carry out high frequency sensing in different ionic strength solutions11.

We describe the device fabrication and measurement protocol for carbon nanotube based high frequency biosensors. The high frequency sensing technique mitigates the fundamental ionic (Debye) screening effect and allows nanotube biosensor to be operated in high ionic strength solutions where conventional electronic biosensors fail. Our technology provides a unique platform for point-of-care (POC) electronic biosensors operating in physiologically relevant conditions.

制备碳纳米管高频纳电子生物传感器的传感高离子强度的解决方案

The unique electronic properties and high surface-to-volume ratios of single-walled carbon nanotubes (SWNT) and semiconductor nanowires (NW) 1-4 make them ...

生物工程

Flow-assisted Dielectrophoresis: A Low Cost Method for the Fabrication of High Performance Solution-processable Nanowire Devices

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of nanowires. DEP is used for nanowire analysis, characterization, and for solution-based fabrication of semiconducting devices. The method works by applying an alternating electric field between metallic electrodes. The nanowire formulation is then dropped onto the electrodes which are on an inclined surface to create a flow of the formulation using gravity. The nanowires then align along the gradient of the electric field and in the direction of the liquid flow. The frequency of the field can be adjusted to select nanowires with superior conductivity and lower trap density. 
In this work, flow-assisted DEP is used to create nanowire field effect transistors. Flow-assisted DEP has several advantages: it allows selection of nanowire electrical properties; control of nanowire length; placement of nanowires in specific areas; control of orientation of nanowires; and control of nanowire density in the device. 
The technique can be expanded to many other applications such as gas sensors and microwave switches. The technique is efficient, quick, reproducible, and it uses a minimal amount of dilute solution making it ideal for the testing of novel nanomaterials. Wafer scale assembly of nanowire devices can also be achieved using this technique, allowing large numbers of samples for testing and large-area electronic applications.

In this paper, flow assisted dielectrophoresis is demonstrated for the self-assembly of nanowire devices. The fabrication of a silicon nanowire field effect transistor is shown as an example.

流动辅助介: 一种低成本的制备高性能溶液可纳米线器件的方法

Flow-assisted dielectrophoresis (DEP) is an efficient self-assembly method for the controllable and reproducible positioning, alignment, and selection of ...

A Standard and Reliable Method to Fabricate Two-Dimensional Nanoelectronics

Two-dimensional (2D) materials have attracted huge attention due to their unique properties and potential applications. Since wafer scale synthesis of 2D materials is still in nascent stages, scientists cannot fully rely on traditional semiconductor techniques for related research. Delicate processes from locating the materials to electrode definition need to be well controlled. In this article, a universal fabrication protocol required in manufacturing nanoscale electronics, such as 2D quasi-heterojunction bipolar transistors (Q-HBT), and 2D back-gated transistors are demonstrated. This protocol includes the determination of material position, electron beam lithography (EBL), metal electrode definition, et al. A step by step narrative of the fabrication procedures for these devices are also presented. Furthermore, results show that each of the fabricated devices has achieved high performance with high repeatability. This work reveals a comprehensive description of process flow for preparing 2D nano-electronics, enables the research groups to access this information, and pave the way toward future electronics.

The article aims to introduce a standard and reliable fabrication procedure for the development of future low dimensional nanoelectronics.

制造二维电子学的标准可靠方法

Two-dimensional (2D) materials have attracted huge attention due to their unique properties and potential applications. Since wafer scale synthesis of 2D ...

Fabrication of Micro-Patterned Chip with Controlled Thickness for High-Throughput Cryogenic Electron Microscopy

A major limitation for the efficient and high-throughput structure analysis of biomolecules using cryogenic electron microscopy (cryo-EM) is the difficulty of preparing cryo-EM samples with controlled ice thickness at the nanoscale. The silicon (Si)-based chip, which has a regular array of micro-holes with graphene oxide (GO) window patterned on a thickness-controlled silicon nitride (SixNy) film, has been developed by applying microelectromechanical system (MEMS) techniques. UV photolithography, chemical vapor deposition, wet and dry etching of the thin film, and drop-casting of 2D nanosheet materials were used for mass-production of the micro-patterned chips with GO windows. The depth of the micro-holes is regulated to control the ice thickness on-demand, depending on the size of the specimen for cryo-EM analysis. The favorable affinity of GO toward biomolecules concentrates the biomolecules of interest within the micro-hole during cryo-EM sample preparation. The micro-patterned chip with GO windows enables high-throughput cryo-EM imaging of various biological molecules, as well as inorganic nanomaterials.

A newly developed micro-patterned chip with graphene oxide windows is fabricated by applying microelectromechanical system techniques, enabling efficient and high-throughput cryogenic electron microscopy imaging of various biomolecules and nanomaterials.