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.

Precaución: Por favor consulte todas las fichas de datos de seguridad de materiales pertinentes (MSDS) antes de usar. Varios de los productos químicos utilizados en el proceso de fabricación son muy tóxico y cancerígeno. Los nanomateriales pueden tener riesgos adicionales en comparación con su contraparte mayor. Utilice todas las prácticas de seguridad adecuadas cuando se trabaja con equipos, productos químicos o los nanomateriales, incluyendo el uso de controles de ingeniería (campana extractora de gases) y el equipo de protección personal (gafas de seguridad, guantes, ropa de sala limpia). 1. Alineación Marker Definición de Litografía <ol><li> Comience con grado industrial pulido de una sola cara de Si (100) obleas con cualquiera n o de tipo p dopaje. </li><li> Escudo de la oblea con 1,4 micras de resina fotosensible positiva. Realizar una hexametildisilazano 90 sec tratamiento (HMDS) a 130 ° C para promover la adhesión de la resina fotosensible, seguido de enfriamiento de la oblea en un plato frío, spin-coating a la velocidad apropiada (3.500 rpm), y un 90 seg bake suave unat 95 ° C. </li><li> El uso de una máscara de fotolitografía y la herramienta de la exposición exponer los marcadores de alineación, la dosis de exposición 120 mJ / cm 2. </li><li> Realizar un único proceso de desarrollo charco. Realizar un 90 seg 115 ° C después de la exposición de pasteles, seguido de 60 segundos de desarrollo utilizando desarrollador y 90 seg dura hornee a 100 ° C para curar la resisten. </li><li> Utilice un microscopio para inspeccionar si las aberturas en la capa protectora son de las dimensiones correctas. </li><li> Etch 120 nm de Si mediante grabado por plasma de cloro. Este espesor da un buen contraste para los sistemas de alineación automática de la herramienta de exposición utilizada en este trabajo. Por ejemplo, usando un plasma inductivo acoplado (ICP): 20/40 sccm O 2 / CF 4, 5 mTorr, 60/500 W platina / potencia RF ICP, 10 seg grabado avance de óxido, seguido de 80/40 sccm Cl 2 / HBr , 60 mTorr, 20/500 W plato / potencia ICP RF, 35 seg Si etch. </li><li> Utilice un separador de plasma de oxígeno para eliminar el fotoprotector (1 kW, 400 sccm O 2 con endpoint detección y 2 min overetch). A medida que la resina fotosensible se cura por el plasma normal solvente como la acetona no puede ser utilizado. </li><li> Limpie las obleas. En primer lugar los puso durante 10 min en 99% HNO 3, seguido de un enjuague en agua DI hasta que la resistividad del agua es 5 mO (limpio orgánico). Después de esto limpia las obleas para 10 min en 65% HNO 3 a 110 ° C, seguido de un enjuague con agua DI hasta que la resistividad del agua es 5 mO (metal limpio). Use un secador de enjuagadora para secar las obleas. </li></ol> 2. metal de fondo y entre capas dieléctrica Deposición <ol><li> Utilice pulverización catódica con magnetrón para depositar la capa metálica inferior de la prueba a través de. Una pila de tres capas de metal necesita ser depositado: 500 nm de Ti, 50 nm de TiN, y 100 nm Ti. La primera capa de Ti es reducir la resistencia de la pila, el TiN es la capa de soporte real para el crecimiento CNT, y la parte superior Ti es proteger el TiN contra el daño de plasma cuando el grabado de la capa de SiO 2 12 </sup&gt;. Realizar Ti bombardeo iónico utilizando un objetivo de Ti puro con Ar-plasma a una temperatura del substrato de 350 ° C. Para TiN pulverización reactiva utilizar una combinación de Ar y N 2, de nuevo a 350 ° C la temperatura del sustrato. </li><li> Uso de deposición química de vapor mejorada con plasma (PECVD), depositar una gruesa capa de SiO 2 1 m. Aquí ortosilicato de tetraetilo (TEOS) se utiliza como precursor a una temperatura de platina de 350 ° C. <ol><li> Controlar el espesor de la capa de SiO 2 usando una herramienta apropiada, por ejemplo un reflectómetro o elipsómetro. </li></ol></li><li> Escudo de la oblea con 1,4 m de material fotorresistente positivo, comenzando con un tratamiento de 90 seg HMDS a 130 ° C, seguido de enfriamiento de la oblea en un plato frío, spin-coating a la velocidad apropiada (3.500 rpm), y un 90 seg suave hornear a 95 ° C. </li><li> El uso de una máscara de fotolitografía y la herramienta de la exposición, exponer el patrón deseado de aberturas, que será más tarde grabado en la SiO 2 to formar las vías, alineados a los marcadores de alineación, la dosis de exposición de 140 mJ / cm2. </li><li> Realizar un único proceso de desarrollo charco comenzando con un 90 seg 115 ° C después de la exposición de pasteles, seguido de 60 segundos de desarrollo utilizando desarrollador y 90 seg dura hornee a 100 ° C. </li><li> Utilice un microscopio para inspeccionar si las aberturas en la capa protectora son de las dimensiones correctas y si la superposición de los marcadores de alineación es correcta. </li><li> Plasma etch las aberturas de contacto en el SiO2. Por ejemplo, utilizar un grabador de plasma triodo con C 2 F 6 / CHF 3 36/144 sccm a 180 mTorr y 300 W de potencia de RF. Si es necesario, realizar pruebas de velocidad de grabado sobre una oblea de prueba, a fin de reducir al mínimo sobre el grabado al 5% -10% en el tiempo. Nota: Aunque el Ti es resistente al ataque químico reactivo en esta química de flúor, la exposición prolongada al plasma se traducirá en el grabado de la capa física Ti. Si la capa de TiN se expone al plasma esto tendrá un influen negativoce en el crecimiento de la CNT 12. No utilice grabado húmedo ya que esto dará lugar a demasiada ampliación de las aberturas, por lo que la metalización superior en la parte 4 problemático. </li><li> Retire la capa de Ti sacrificial mediante grabado húmedo en 0.55% HF durante 60 segundos. Después del ataque enjuagar las obleas con agua DI hasta que la resistividad del agua es 5 mO y utilizar un secador de enjuagadora para secar las obleas. Nota: El uso de un microscopio se puede comprobar si la capa de Ti está grabado, la capa de TiN tendrá un color dorado-marrón, mientras que el Ti es de color gris metálico. </li></ol> 3. Catalizador Deposición y Crecimiento CNT <ol><li> Se evapora 5 nm de Co utilizando un evaporador de haz de electrones. Bomba abajo hasta al menos 2x10 -6 Torr, y el calor de las obleas a 60 ° C utilizando lámparas de bajo vacío antes de depositar para eliminar cualquier película de agua. La foto-resistir usada para definir las aberturas de contacto se mantiene en la oblea para proporcionar auto-alineación del catalizador a las aberturas de contacto en el SiO2. </li><li> Eliminarla Co fuera de las aberturas de contacto por el despegue. Para Co se encontró que tetrahidrofurano (THF) da los mejores resultados de despegue y crecimiento a bajas temperaturas. N-metil-2-pirrolidona (NMP), que fue utilizado previamente para el despegue después de la evaporación Fe, se encontró que el daño una medida de la Co también por ejemplo para prevenir cualquier crecimiento de CNT alineados. Ponga la oblea durante 15 minutos en un baño de ultrasonidos con THF a 35 ° C. Enjuague con agua DI durante 5 min y secar con una pistola de spinner o nitrógeno. </li><li> Inspeccione la oblea bajo un microscopio y verificar resistir residuos. Si quedan residuos realizar un tratamiento más largo de ultrasonidos en THF, y opcionalmente usar un hisopo de algodón suave especial para fines de despegue para limpiar manualmente los residuos de distancia. </li><li> Realizar el crecimiento CNT mediante deposición química de vapor de baja presión (LPCVD). Utilice la siguiente receta: 8 min pre-recocido a 350 ° C con 700 sccm H 2 a 80 mbar, seguido por el crecimiento de CNT mediante la adición de 50 sccm C 2 H 2. A 350 ° C, 60min del crecimiento da más o menos 1 m de CNT. Si es necesario realizar una prueba de crecimiento para sintonizar la altura, que debe ser del mismo grosor que la capa de SiO 2. Enfriar el reactor y purgar el uso de N 2. </li><li> Utilice un microscopio electrónico de barrido para comprobar la altura de la CNT en el interior de las aberturas debajo de 45 ° de inclinación, o preparando una sección transversal. </li><li> Inspeccione las muestras usando la espectroscopia Raman para determinar la cristalinidad de la CNT 18. </li></ol> 4. Topside Metalización <ol><li> Utilice pulverización catódica para depositar el metal de la parte superior. Como Ti es un buen metal para hacer contacto con CNT 19, primero por pulverización catódica 100 nm de Ti, seguido de 2 micras de Al (1% Si) sin romper el vacío. </li><li> Escudo de la oblea con 3,1 micras de resina fotosensible positiva con mayor viscosidad, comenzando con un tratamiento de 90 seg HMDS a 130 ° C, seguido de enfriamiento de la oblea en un plato frío, spin-recubrimiento a 3000 rpm, y una cocción suave 90 seg a 95DO. </li><li> El uso de una máscara de fotolitografía y la herramienta de la exposición exponer el patrón de metal superior alineado con los marcadores de alineación, la dosis de exposición 420 mJ / cm 2, el enfoque de -1. </li><li> Realizar un único proceso de desarrollo charco. Esto comienza con un 90 seg 115 ° C después de la exposición de pasteles, seguido de 60 segundos de desarrollo utilizando desarrollador y 90 seg dura hornee a 100 ° C. </li><li> Utilice un microscopio para inspeccionar si las líneas en la capa protectora son de las dimensiones correctas y si la superposición de los marcadores es correcta. </li><li> Etch la pila de Ti / Al utilizar el grabado por plasma de cloro. Por ejemplo el uso de un plasma de acoplamiento inductivo: 30/40 sccm Cl 2 / HBr, 5 mTorr, 40/500 W de potencia de la platina / ICP RF con detección de punto final y 80% overetch usando 15/30 sccm Cl 2 / HBr. </li><li> Utilice un separador de plasma de oxígeno para eliminar el fotoprotector (1 kW, 400 sccm O 2 con detección de punto final y 2 min overetch). Si la cobertura de metal no está completa (es decir, hay agujeros alrededor de laCNT) utiliza un disolvente orgánico (por ejemplo, NMP) para eliminar la resina fotosensible con el fin de evitar daños en plasma a la CNT. </li><li> Limpie las obleas. Puesto les durante 10 min en 99% HNO 3, seguido de un enjuague con agua DI hasta que la resistividad del agua es 5 mO (limpio orgánico). Use un secador de enjuagadora para secar las obleas. </li></ol> 5. Mediciones <ol><li> Utilice un microscopio electrónico de barrido de acuerdo con las instrucciones del fabricante para comprobar la metalización parte superior de las obleas. Nota:. Si es necesario la oblea se puede escindir mecánicamente con el fin de comprobar la completa CNT a través utilizando una inclinación de la muestra de 90 °, lo que resulta en imágenes como se muestra en la Figura 3 ya que las muestras son eléctricamente conductores tienen que ser utilizados sin pasos de tratamiento adicionales y las muestras se pueden montar directamente en el SEM. En general, los voltajes de alta aceleración de 15 kV o 20 se pueden usar, pero si la capa de SiO 2 se está cargando demasiado esto puede ser reducido to 5 kV. </li><li> Realizar 4 puntos mediciones sonda IV utilizando una estación de sonda en combinación con un parámetro analizador de semiconductor como se describe en la Figura 1 y en Vollebregt et al. 16. Nota: Normalmente un barrido de tensión desde -0,5 a 0,5 V es suficiente, ya que la caída de potencial a través de una interconexión idealmente es pequeña. Mediante el uso de una configuración de sonda de 4 puntos la resistencia de contacto de las agujas de la sonda y las resistencias de alambre de la configuración se omiten. </li></ol>

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The authors have nothing to disclose.

La figura 1 muestra una visión esquemática de la estructura fabricada en este trabajo, y que se utilizó para las mediciones de la sonda de 4 puntos. A medida que el potencial se mide a través de sondas que llevan ninguna corriente, la caída de potencial exacta (V H -V L) sobre el haz de CNT central y sus contactos a que el metal se puede medir. Mayor diámetro haces de CNT se utilizan para ponerse en contacto con la capa de TiN parte inferior de las almohadillas de contacto, a...

El cobre y tungsteno, los metales que se utilizan actualmente para las interconexiones en tecnología de última generación, muy gran escala de integración (VLSI), se están acercando a sus límites físicos en cuanto a fiabilidad y la conductividad eléctrica 1. Mientras que los transistores de baja escala general mejora su rendimiento, en realidad, aumenta la resistencia y la densidad de corriente de las interconexiones. Esto dio lugar a las interconexiones que dominan el funcionamiento del circuito integrado (IC) en términos de retardo y consumo de energía 2. Los nanotubos de carbono (CNT) se han sugerido como alternativa para Cu y W metalización, especialmente para las interconexiones verticales (Vias) como CNT fácilmente pueden sido cultivados vertical 3. CNT han demostrado tener una excelente fiabilidad eléctrica, lo que permite un máximo de 1.000 veces mayor densidad de corriente de Cu 4. Por otra parte, la CNT no sufren de la superficie y el grano límite de dispersión, que es cada vez mayor la resistivity de Cu en la escala nanométrica 5. Finalmente, CNT han demostrado ser excelentes conductores térmicos 6, que pueden ayudar en la gestión térmica en los chips VLSI. Para la integración exitosa de CNT en la tecnología VLSI es importante que los procesos de crecimiento de la CNT se hace compatible con la fabricación de semiconductores. Esto requiere que el crecimiento de la CNT (&lt;400 ° C) el uso de materiales y equipos que se consideran compatibles y escalable para la fabricación a gran escala de baja temperatura. Aunque muchos ejemplos de vías de prueba de la CNT se han demostrado en la literatura 7,8,9,10,11,12,13,14, la mayoría de ellos utilizan Fe como catalizador que es considerado como un contaminante en el IC de fabricación 15. Además, la temperatura de crecimiento utilizado en muchos de estos trabajos es mucho mayor que el límite superior de 400 ° C. Preferiblemente CNT aún se cultiva por debajo de 350 ° C, con el fin de permitir la integración con dieléctricos de bajo kappa modernos o flexiblessustratos. Aquí presentamos un método escalable para el crecimiento de CNT a temperaturas tan bajas como 350 ° C utilizando como catalizador Co 16. Este método es de interés para la fabricación de diferentes estructuras eléctricos que consisten en alineada verticalmente CNT en circuitos integrados, que van desde interconexión y los electrodos de supercondensadores y dispositivos de emisión de campo. El metal catalizador de Co se utiliza a menudo en la fabricación de IC para la fabricación de siliciuro de 17, mientras que el estaño es un material de barrera utilizado a menudo 7. Por otra parte, se demuestra un proceso para la fabricación de vías de prueba de la CNT, mientras que sólo el uso de técnicas de fabricación de semiconductores estándar. Con esto, vias de prueba CNT se fabrican, inspeccionados por microscopía electrónica de barrido (SEM) y la espectroscopia Raman, y eléctricamente caracterizado.

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			<td height="21" style="height:21px;width:307px;">Materials</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Si (100) wafer 4&#34;</td>
			<td style="width:188px;">International Wafer Service</td>
			<td style="width:119px;"></td>
			<td>Resisitivity: 2-5 m&#937;-cm, thickness: 525 &#181;m&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Ti-sputtertarget (99.995 % purity)</td>
			<td style="width:188px;">Praxair</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Al (1% Si)-sputtertarget (99.999 % purity)</td>
			<td style="width:188px;">Praxair</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Co (99.95 % purity)</td>
			<td style="width:188px;">Kurt J. Lesker</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Chemicals</td>
			<td style="width:188px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td>Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">SPR3012 positive photoresist</td>
			<td style="width:188px;">Dow Electronic Materials</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">MF-322 developer</td>
			<td style="width:188px;">Dow Electronic Materials</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">HNO3 (99.9 %)</td>
			<td style="width:188px;">KMG Ultra Pure Chemicals</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">HNO3 (69.5%)</td>
			<td style="width:188px;">KMG Ultra Pure Chemicals</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">HF 0.55%</td>
			<td style="width:188px;">Honeywell</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Tetrahydrofuran</td>
			<td style="width:188px;">JT Baker</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Acetone</td>
			<td style="width:188px;">Sigma-Aldrich</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">ECI3027 positive photoresist</td>
			<td style="width:188px;">AZ</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Tetraethyl orthosilicate (TEOS)</td>
			<td style="width:188px;">Praxair</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Gasses</td>
			<td style="width:188px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td>Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">N2 (99.9990%)</td>
			<td style="width:188px;">Praxair</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">O2 (99.9999%)</td>
			<td style="width:188px;">Praxair</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">CF4 (99.9970%)</td>
			<td style="width:188px;">Praxair</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">CL2 (99.9900%)</td>
			<td style="width:188px;">Praxair</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">HBr (99.9950%)</td>
			<td style="width:188px;">Praxair</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Ar (99.9990%)</td>
			<td style="width:188px;">Praxair</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">C2F6 (99.9990%)</td>
			<td style="width:188px;">Praxair</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">CHF3 (99.9950%)</td>
			<td style="width:188px;">Praxair</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">H2 (99.9950%)</td>
			<td style="width:188px;">Praxair</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">C2H2 (99.6000%)</td>
			<td style="width:188px;">Praxair</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Equipment</td>
			<td style="width:188px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td>Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">EVG 120 coater/developer</td>
			<td style="width:188px;">EVG</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">ASML PAS5500/80 waferstepper</td>
			<td style="width:188px;">ASML</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">SPTS &#937;mega 201 plasma etcher</td>
			<td style="width:188px;">SPTS</td>
			<td style="width:119px;"></td>
			<td>Used for Si and metal etching</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">SPTS &#931;igma sputter coater</td>
			<td style="width:188px;">SPTS</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Novellus Concept One PECVD</td>
			<td style="width:188px;">LAM</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Drytek 384T plasma etcher</td>
			<td style="width:188px;">LAM</td>
			<td style="width:119px;"></td>
			<td>Used for oxide etching</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">CHA Solution e-beam evaporator</td>
			<td style="width:188px;">CHA</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">AIXTRON BlackMagic Pro CVD tool</td>
			<td style="width:188px;">AIXTRON</td>
			<td style="width:119px;"></td>
			<td>Carbon nanotube growth</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Philips XL50 scanning electron microscope</td>
			<td style="width:188px;">FEI</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Tepla 300</td>
			<td style="width:188px;">PVA TePla</td>
			<td style="width:119px;"></td>
			<td>Resist plasma stripper</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Avenger rinser dryer</td>
			<td style="width:188px;">Microporcess Technologies</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Leitz MPV-SP reflecometer</td>
			<td style="width:188px;">Leitz</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Renishaw inVia Raman spectroscope</td>
			<td style="width:188px;">Renishaw</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Agilent 4156C parameter spectrum analyzer</td>
			<td style="width:188px;">Agilent</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:307px;">Cascade Microtech probe station</td>
			<td style="width:188px;">Cascade Microtech</td>
			<td style="width:119px;"></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.

El diseño de la estructura de medición utilizado en este trabajo se puede encontrar en la Figura 1. Mediante el empleo de una estructura tal, la medición de la resistencia haz CNT y las resistencias de contacto de metal-CNT puede determinarse con precisión, como sonda de alambre y resistencias se eluden. La resistencia del haz es una medida de la calidad y densidad del haz de CNT. Con el fin de determinar los haces de resistencia de contacto de diferentes longitudes se debe medir. <...

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.

Fabricación de Baja Temperatura de nanotubos de carbono Interconexiones verticales Compatible con la tecnología de semiconductores

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

Research

JoVE Journal

Engineering

7.6K vistas.  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.

Video: 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.

Fabricación, densificación, y la réplica de Moldeo por inyección de microestructuras 3D nanotubos de carbono

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

Investigación

Ingeniería

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.

La oxidación en seco y vacío Recocido Tratamientos para Ajuste las propiedades humectantes de conjuntos de nanotubos de carbono

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

Synthesis and Functionalization of Nitrogen-doped Carbon Nanotube Cups with Gold Nanoparticles as Cork Stoppers

Nitrogen-doped carbon nanotubes consist of many cup-shaped graphitic compartments termed as nitrogen-doped carbon nanotube cups (NCNCs). These as-synthesized graphitic nanocups from chemical vapor deposition (CVD) method were stacked in a head-to-tail fashion held only through noncovalent interactions. Individual NCNCs can be isolated out of their stacking structure through a series of chemical and physical separation processes. First, as-synthesized NCNCs were oxidized in a mixture of strong acids to introduce oxygen-containing defects on the graphitic walls. The oxidized NCNCs were then processed using high-intensity probe-tip sonication which effectively separated the stacked NCNCs into individual graphitic nanocups. Owing to their abundant oxygen and nitrogen surface functionalities, the resulted individual NCNCs are highly hydrophilic and can be effectively functionalized with gold nanoparticles (GNPs), which preferentially fit in the opening of the cups as cork stoppers. These graphitic nanocups corked with GNPs may find promising applications as nanoscale containers and drug carriers.

We discussed the synthesis of individual graphitic nanocups using a series of techniques including chemical vapor deposition, acid oxidation and probe-tip sonication. By citrate reduction of HAuCl4, the graphitic nanocups were effectively corked with gold nanoparticles due to the chemically reactive edges of the cups.

Síntesis y funcionalización de nitrógeno dopados Copas de nanotubos de carbono con nanopartículas de oro como tapones de corcho

Nitrogen-doped carbon  nanotubes consist of many cup-shaped graphitic compartments termed as  nitrogen-doped carbon nanotube cups (NCNCs).  These ...

Writing and Low-Temperature Characterization of Oxide Nanostructures

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions. Oxide interfaces exhibit a wide range of properties that can be controlled include conduction, piezoelectric behavior, ferromagnetism, superconductivity and nonlinear optical properties. Recently, methods for controlling these properties at extreme nanoscale dimensions have been discovered and developed. Here are described explicit step-by-step procedures for creating LaAlO3/SrTiO3 nanostructures using a reversible conductive atomic force microscopy technique. The processing steps for creating electrical contacts to the LaAlO3/SrTiO3 interface are first described. Conductive nanostructures are created by applying voltages to a conductive atomic force microscope tip and locally switching the LaAlO3/SrTiO3 interface to a conductive state. A versatile nanolithography toolkit has been developed expressly for the purpose of controlling the atomic force microscope (AFM) tip path and voltage. Then, these nanostructures are placed in a cryostat and transport measurements are performed. The procedures described here should be useful to others wishing to conduct research in oxide nanoelectronics.

Oxide nanostructures provide new opportunities for science and technology. The interfacial conductivity between LaAlO3 and SrTiO3 can be controlled with near-atomic precision using a conductive atomic force microscopy technique. The protocol for creating and measuring conductive nanostructures at LaAlO3/SrTiO3 interfaces is demonstrated.

La escritura y la caracterización de baja temperatura de óxido de Nanoestructuras

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions.  Oxide ...

Ohmic Contact Fabrication Using a Focused-ion Beam Technique and Electrical Characterization for Layer Semiconductor Nanostructures

Layer semiconductors with easily processed two-dimensional (2D) structures exhibit indirect-to-direct bandgap transitions and superior transistor performance, which suggest a new direction for the development of next-generation ultrathin and flexible photonic and electronic devices. Enhanced luminescence quantum efficiency has been widely observed in these atomically thin 2D crystals. However, dimension effects beyond quantum confinement thicknesses or even at the micrometer scale are not expected and have rarely been observed. In this study, molybdenum diselenide (MoSe2) layer crystals with a thickness range of 6-2,700 nm were fabricated as two- or four-terminal devices. Ohmic contact formation was successfully achieved by the focused-ion beam (FIB) deposition method using platinum (Pt) as a contact metal. Layer crystals with various thicknesses were prepared through simple mechanical exfoliation by using dicing tape. Current-voltage curve measurements were performed to determine the conductivity value of the layer nanocrystals. In addition, high-resolution transmission electron microscopy, selected-area electron diffractometry, and energy-dispersive X-ray spectroscopy were used to characterize the interface of the metal&#8211;semiconductor contact of the FIB-fabricated MoSe2 devices. After applying the approaches, the substantial thickness-dependent electrical conductivity in a wide thickness range for the MoSe2-layer semiconductor was observed. The conductivity increased by over two orders of magnitude from 4.6 to 1,500 &#937;&#8722;1 cm&#8722;1, with a decrease in the thickness from 2,700 to 6 nm. In addition, the temperature-dependent conductivity indicated that the thin MoSe2 multilayers exhibited considerably weak semiconducting behavior with activation energies of 3.5-8.5 meV, which are considerably smaller than those (36-38 meV) of the bulk. Probable surface-dominant transport properties and the presence of a high surface electron concentration in MoSe2 are proposed. Similar results can be obtained for other layer semiconductor materials such as MoS2 and WS2.

We describe the approaches for the device fabrication and electrical characterization of molybdenum diselenide (MoSe2) layer semiconductor nanostructures with different thicknesses. In addition, the fabrication of ohmic contacts for MoSe2-layer nanocrystals by the focused-ion beam deposition method using platinum (Pt) as a contact metal is described.

Óhmico Contacto Fabricación Usando una técnica enfocada-ion Beam y Eléctrica Caracterización de Nanoestructuras capa semiconductora

Layer semiconductors with easily processed two-dimensional (2D) structures exhibit indirect-to-direct bandgap transitions and superior transistor ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

Avanzados métodos experimentales para baja temperatura magnetotransporte Medición de Nuevos Materiales

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

Precision Milling of Carbon Nanotube Forests Using Low Pressure Scanning Electron Microscopy

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning electron microscope (ESEM) operating with a low pressure water vapor ambient. In this technique, a portion of the electron beam interacts with the water vapor in the vicinity of the CNT sample, dissociating the water molecules into hydroxyl radicals and other species by radiolysis. The remainder of the electron beam interacts with the CNT forest sample, making it susceptible to oxidation from the chemical products of radiolysis. This technique may be used to trim a selected region of an individual CNT, or it may be used to remove hundreds of cubic microns of material by adjusting ESEM parameters. The machining resolution is similar to the imaging resolution of the ESEM itself. The technique produces only small quantities of carbon residue along the boundaries of the cutting zone, with minimal effect on the native structural morphology of the CNT forest.

Low pressure scanning electron microscopy in a water vapor ambient is used to machine nanoscale to microscale features in carbon nanotube forests.

Fresado de precisión de nanotubos de carbono de los bosques El uso de baja presión de barrido Microscopía Electrónica

A nanoscale fabrication technique appropriate for milling carbon nanotube (CNT) forests is described. The technique utilizes an environmental scanning ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

Alta Fabrication Temperatura de-estabilizada con itria-óxido de circonio andamios nanoestructurados (YSZ) por<em&gt; In Situ</em&gt; carbono Templating xerogeles

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

Fabrication of 3D Carbon Microelectromechanical Systems (C-MEMS)

A wide range of carbon sources are available in nature, with a variety of micro-/nanostructure configurations. Here, a novel technique to fabricate long and hollow glassy carbon microfibers derived from human hairs is introduced. The long and hollow carbon structures were made by the pyrolysis of human hair at 900 &#176;C in a N2 atmosphere. The morphology and chemical composition of natural and pyrolyzed human hairs were investigated using scanning electron microscopy (SEM) and electron-dispersive X-ray spectroscopy (EDX), respectively, to estimate the physical and chemical changes due to pyrolysis. Raman spectroscopy was used to confirm the glassy nature of the carbon microstructures. Pyrolyzed hair carbon was introduced to modify screen-printed carbon electrodes ; the modified electrodes were then applied to the electrochemical sensing of dopamine and ascorbic acid. Sensing performance of the modified sensors was improved as compared to the unmodified sensors. To obtain the desired carbon structure design, carbon micro-/nanoelectromechanical system (C-MEMS/C-NEMS) technology was developed. The most common C-MEMS/C-NEMS fabrication process consists of two steps: (i) the patterning of a carbon-rich base material, such as a photosensitive polymer, using photolithography; and (ii) carbonization through the pyrolysis of the patterned polymer in an oxygen-free environment. The C-MEMS/NEMS process has been widely used to develop microelectronic devices for various applications, including in micro-batteries, supercapacitors, glucose sensors, gas sensors, fuel cells, and triboelectric nanogenerators. Here, recent developments of a high-aspect ratio solid and hollow carbon microstructures with SU8 photoresists are discussed. The structural shrinkage during pyrolysis was investigated using confocal microscopy and SEM. Raman spectroscopy was used to confirm the crystallinity of the structure, and the atomic percentage of the elements present in the material before and after pyrolysis was measured using EDX.

Fabrication of 3D Carbon Microelectromechanical Systems C-MEMS

Long and hollow glassy carbon microfibers were fabricated based on the pyrolysis of a natural product, human hair. The two fabrication steps of carbon microelectromechanical and carbon nanoelectromechanical systems, or C-MEMS and C-NEMS, are: (i) photolithography of a carbon-rich polymer precursor and (ii) pyrolysis of the patterned polymer precursor.

Fabricación de sistemas microelectromecánicos de carbono 3D (C-MEMS)

A wide range of carbon sources are available in nature, with a variety of micro-/nanostructure configurations. Here, a novel technique to fabricate long ...

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.

Asistida por flujo dielectroforesis: Un método de bajo costo para la fabricación de dispositivos de nanocable procesables en solución de alto rendimiento

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