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：使用する前に、関連するすべての物質安全データシート（MSDS）を参照してください。この製造工程で使用される化学物質のいくつかは、急性毒性と発癌性です。ナノ材料は、そのバルク対応物に比べて付加的な危険性を有していてもよいです。工学的制御（ヒュームフード）と個人用保護具（安全眼鏡、手袋、クリーンルーム服）の使用を含む、機器、化学物質やナノ材料を扱うときに、すべての適切な安全対策を使用してください。 リソグラフィ1.アライメントマーカ定義<ol><li>いずれかのnまたはp型ドーピング片面研磨工業用グレードのSi（100）ウエハーから開始します。 </li><li>コー​​トポジ型フォトレジストの1.4ミクロンを有するウェーハ。コー​​ルドプレート、適切な速度（3,500 rpm）でスピンコーティングし、90秒間ソフトベークAのウエハを冷却し、フォトレジストの接着を促進するために130℃で90秒間のヘキサメチルジシラザン（HMDS）処理を行いますトン95℃。 </li><li>フォトリソグラフィマスクを用いて露光ツールは、アライメントマーカを露光、露光量120ミリジュール/ cm 2です。 </li><li>シングルパドル現像プロセスを実行します。抵抗硬化させるために、100℃で、開発者と90秒のハードベークを用いて60秒の開発に続いて90秒115℃の露光後ベークを実行します。 </li><li>レジスト中の開口部が正しい寸法である場合に検査するために顕微鏡を使用してください。 </li><li>塩素プラズマエッチングを使用して120nmでのSiをエッチングします。この厚さは、この作品で使用される露光ツールの自動アライメントシステムのための良好なコントラストを提供します。 20/40 SCCM O 2 / CF 4、5 40分の80 SCCMのCl 2 / HBrの続くエッチングトル、500分の60 Wプラテン/ ICP RFパワー、10秒の酸化画期的な、たとえば誘導結合プラズマ（ICP）を使用して、 、60ミリトール、500分の20 Wプラテン/ ICP RFパワーは、35秒Siをエッチングします。 </li><li> endpoで1キロワット、400 SCCMのO 2（フォトレジストを除去するために酸素プラズマストリッパーを使用してくださいint型の検出と2分のオーバーエッチング）。フォトレジストは、アセトンのような通常の溶媒、プラズマによって硬化されるように使用することができません。 </li><li>ウエハを清掃してください。まず、水の抵抗率は5MΩ（有機クリーン）であるまでDI水ですすぎ、続いて99％HNO 3に 10分のためにそれらを置きます。水の抵抗率は5MΩ（清浄な金属）であるまで、110℃で65％HNO 3で10分間ウエハーこのクリーン後、DI水でリンスしました。ウェーハを乾燥させるためにリンサ乾燥機を使用してください。 </li></ol> 2.底部金属と層間絶縁膜の堆積<ol><li>経由テストの底部金属層を堆積させるために、マグネトロンスパッタ法を使用してください。 Tiを500 nmで、TiNの50nmであり、100nmのチタンを：3つの金属層のスタックを堆積する必要があります。最初のTi層は、スタックの抵抗を低減することで、TiNがCNTの成長のための実際の支持層であり、SiO 2層12をエッチングする際に上部Tiはプラズマダメージに対してのTiNを保護することです</suP&gt;。 Tiを350℃の基板温度でアルゴンプラズマと純Tiターゲットを用いたスパッタリング行います。 TiNの反応性スパッタリングを再度350℃の基板温度で、ArとN 2の組み合わせを使用します。 </li><li>プラズマ強化化学蒸着（PECVD）を用いて、SiO 2からなる厚さ1μmの層を堆積させます。ここにテトラエチルオルトシリケート（TEOS）は、350℃のプラテン温度で前駆体として使用されます。 <ol><li>適切なツールを使用してSiO 2層の厚さは、例えば、反射率計やエリプソメータを確認してください。 </li></ol></li><li>コー​​トコールドプレート、適切な速度（3,500 rpm）でスピンコーティング、およびソフト90秒でウエハの冷却に続いて130℃、90秒のHMDS処理を開始するポジ型フォトレジストの1.4ミクロン、ウエハ95℃で焼きます。 </li><li>フォトリソグラフィマスクおよび露光ツールを使用して、後にSiO 2トンにエッチングされる開口部の所望のパターンを露光Oアライメントマーカに整列ビアを形成し、露光量140ミリジュール/ cm 2です。 </li><li>開発者および100℃でハードベーク90秒を使用して、60秒の開発に続いて90秒間115℃の露光後ベーク、始まるシングルパドル現像プロセスを実行します。 </li><li>レジスト中の開口部が正しい寸法である場合とアライメントマーカにオーバーレイが正しいかどうかを検査するために顕微鏡を使用してください。 </li><li>プラズマは、SiO 2のコンタクト開口部をエッチングします。例えば、C 2 F 6とトライオードプラズマエッチャーを使用/ CHF 3 144分の36 SCCM 180ミリトール〜300 WのRF電力で。必要に応じて、時間の5％〜10％のオーバーエッチングを最小にするために、テストウェハ上にエッチング速度試験を行います。 注：Tiは、このフッ素化学の反応性エッチングに耐性があるが、プラズマへの長期暴露は、Ti層の物理的エッチングになります。 TiN層がプラズマにさらされている場合、これは負のinfluenを持っていますCNT 12の成長にCE。これが問題の部分4のトップメタライゼーションを作り、開口部のあ​​まり拡大につながるよう、ウェットエッチングを使用しないでください。 </li><li> 60秒間0.55％のHFでウェットエッチングにより犠牲Ti層を削除します。水の抵抗率までDI水でウェハをすすぐエッチングした後5MΩで、ウェーハを乾燥させるためにリンサ乾燥機を使用しています。 注：TiはメタリックグレイでありながらTi層をエッチングする場合には、確認することができる顕微鏡を使用して、TiN層は、金茶色を有することになります。 </li></ol> 3.触媒堆積とCNT成長<ol><li>電子ビーム蒸発器を用いてCoを5nmとを蒸発させます。少なくとも2×10 -6トールまでポンプダウンし、任意の水膜を除去するために堆積させる前に、真空下でランプを用いて60°Cにウエハを加熱します。フォトレジストのコンタクト開口部を定義するために使用さは、SiO 2のコンタクト開口に触媒の自己整合を提供するために、ウエハ上に維持されます。 </li><li>削除リフトオフによる接触開口部の外側のCo。 Coのためには、テトラヒドロフラン（THF）は、低温で最高のリフトオフの結果と成長を与えることが見出された。以前のFeを蒸発させた後、リフトオフのために使用したN -メチル-2-ピロリドン（NMP）は、損傷することが見出されました任意の配向CNTの成長を防止するために、共同あまりに程度。 35℃のTHFで超音波浴中で15分間ウェハを置きます。 5分間DI水ですすぎ、スピナー、窒素ガンを使用して乾燥させます。 </li><li>顕微鏡の下にウェハを検査し、レジスト残渣を確認してください。残留物が残っている場合、THF中の長い超音波処理を行い、必要に応じて手動で残基を払拭するために、リフトオフのために特別なソフト綿棒を使用しています。 </li><li>低圧化学蒸着（LPCVD）を用いて、CNTの成長を行います。 50 SCCMのC 2 H 2を追加することにより、CNTの成長に続いて80ミリバールで700 SCCMのH 2で350℃で8分間のプレアニーリング、次のレシピを使用してください。 350℃で、60成長の分はおよそ1ミクロンのCNTを与えます。必要に応じて調整するために、SiO 2層と同じ厚さであるべき高さを、テストの成長を行います。原子炉を冷却し、N 2を用いてパージします。 </li><li> 45°傾斜の下、または断面を調製することによって、開口部内部のCNTの高さを確認するために、走査型電子顕微鏡を使用してください。 </li><li> CNT 18の結晶化度を決定するために、ラマン分光法を用いてサンプルを検査します。 </li></ol> 4.トップサイドメタライゼーション<ol><li>上部金属を堆積させるために、マグネトロンスパッタリングを使用してください。 Tiは、CNT 19を接触させるための良い金属であるため、第1の真空を破ることなく、アル（1％のSi）の2ミクロン続いTiを100nmとし、スパッタ。 </li><li>より高い粘度のポジ型フォトレジストの3.1ミクロンでコートウェハを、コールドプレート、3000 rpmでスピンコートし、90秒間ソフトベークにウエハの冷却に続いて130℃、90秒のHMDS処理で始まります95°C。 </li><li>ミリジュール/ cm 2で、フォトリソグラフィマスクおよび露光ツールがアライメントマーカに合わせ上部金属パターンが露出-1フォーカス露光量420使っ。 </li><li>シングルパドル現像プロセスを実行します。これは、100℃で、開発者と90秒のハードベークを用いて60秒現像し、90秒間115℃の露光後ベークを開始します。 </li><li>レジスト中の行が正しい寸法である場合や、マーカーのオーバーレイが正しいかどうかを検査するために顕微鏡を使用してください。 </li><li>塩素プラズマエッチングを用いたTi / Alの積層体をエッチングします。 30/40 SCCMのCl 2 / HBrを、5ミリトール、終点検出および15/30 SCCMのCl 2 / HBrのを使用して、オーバーエッチ80％と500分の40 Wプラテン/ ICP RFパワー：誘導結合プラズマを用いて、例えば。 </li><li>フォトレジスト（1キロワット、終点検出、2分間のオーバーエッチングと400のSCCM O 2）を除去するために、酸素プラズマストリッパーを使用してください。金属被覆が完了していない場合（ すなわち、周りのピンホールが存在しますCNT）CNTに対するプラズマ損傷を防止するために、フォトレジストを除去するために、有機溶媒（ 例えば、NMP）を使用します。 </li><li>ウエハを清掃してください。水の抵抗率は5MΩ（有機クリーン）であるまでDI水ですすぎ、続いて99％HNO 3に 10分のためにそれらを置きます。ウェーハを乾燥させるためにリンサ乾燥機を使用してください。 </li></ol> 5.測定<ol><li>ウェハの上部メタライゼーションをチェックするために、製造業者の指示に従って、走査型電子顕微鏡を使用してください。 必要なウェーハを機械的に、図3に示すように、画像が得られ、90度のサンプルの傾きを使用してを介して完全なCNTをチェックするために切断することができる場合、サンプルは導電性であるように、追加の処理工程を使用する必要がなく、：注意サンプルは、直接SEMに装着することができます。一般的に、15または20キロボルトの高い加速電圧を使用することができるが、SiO 2層は、これは、Tを小さくすることができるあまりまで充電された場合5 kVのO。 </li><li> 図1及びVollebregt らに記載されるように、半導体パラメータアナライザと組み合わせてプローブステーションを用いて、4点探針IV測定を行う。16。 注意：相互接続の上に電位降下が理想的に小さいとして通常-0.5から0.5 Vの電圧掃引は、十分です。 4点プローブの設定を使用して、プローブ針とセットアップの配線抵抗の接触抵抗は省略しています。 </li></ol>

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The authors have nothing to disclose.

図1は、本研究で作製した構造の概略図を表示し、これは、4点プローブ測定のために使用しました。電位は電流を運ぶないプローブにより測定されるように、中央のCNT束と金属との接点上に正確な電位降下（V H -V L）を測定することができます。より大きい直径のCNT束は、現在の強制プローブの全体の抵抗を低減し、中央のCNT束上に電位降下を最大にするために?...

銅とタングステンは、現在最先端の超大規模集積回路（VLSI）技術における相互接続のために使用される金属は、信頼性と電気伝導度1の面で彼らの物理的な限界に近づいています。ダウンスケーリングトランジスタは、一般的にそのパフォーマンスを改善するが、実際の抵抗及び配線の電流密度を増加させます。これは、遅延と電力消費2の観点の集積回路（IC）の性能を支配する相互接続をもたらしました。 CNTが簡単に縦3栽培されてできるようにカーボンナノチューブ（CNT）は、特に垂直相互接続（ビア）のために、CuとWメタライゼーションのための代替として提案されています。 CNTは、Cu 4よりも最大1,000倍高い電流密度を可能にする、優れた電気的信頼性を有することが示されています。また、CNTは、表面及び結晶粒界散乱を受けない、これは、rが増加していますナノメートルスケール5でのCuのesistivity。最後に、CNTは、VLSIチップの熱管理するのを助けることができる優れた熱伝導体6、であることが示されています。 VLSI技術におけるCNTの統合を成功のためには、CNTの成長プロセスは半導体製造と互換性がなされることが重要です。これは、材料及び大規模製造に適合し、かつスケーラブルであると考えられる装置を用いてCNT（&lt;400℃）での低温成長を必要とします。 CNT試験ビアの多くの例が文献7,8,9,10,11,12,13,14で実証されているが、これらのほとんどは、IC内の汚染物質15を製造すると考えられる触媒として鉄を使用します。また、これらの研究の多くで使用される成長温度は、400°Cの上限値よりもはるかに高いです。好ましくは、CNTはあっても、現代の低κ誘電体やフレキシブルとの統合を可能にするために、350℃以下で成長する必要があります基板。 ここでは、 触媒 16としてのCoを使用して350℃程度の低温でCNTを成長させるためのスケーラブルな方法を提示します。この方法は、相互接続と電極のスーパーキャパシタおよび電界放出素子までの集積回路に垂直配向CNTからなる別の電気構造を製造するために重要です。 TiNをしばしば使用するバリヤ材 7である間のCo触媒金属は、多くの場合、シリサイドの17の製造のためのIC製造で使用されます。また、私たちは、標準的な半導体製造の技術を使用しながら、CNT試験ビアを製造するためのプロセスを示します。これにより、CNT試験ビアは、製造される電子顕微鏡（SEM）及びラマン分光法を走査することによって検査され、電気的特徴。

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			<td style="width:188px;">Company</td>
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			<td style="width:291px;">Comments/Description</td>
		</tr>
		<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>
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			<td height="21" style="height:21px;width:307px;">Chemicals</td>
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			<td>Comments/Description</td>
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		<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>
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		<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>
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		<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>
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		<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>
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		<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>
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		<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>
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			<td height="21" style="height:21px;width:307px;">Equipment</td>
			<td style="width:188px;">Company</td>
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			<td>Comments/Description</td>
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			<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>
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		<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>
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		<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.

この研究で使用した測定構造の設計は 、図1に見ることができる。プローブ、ワイヤ抵抗が回避されるように、CNT束の抵抗と金属CNTの接触抵抗の測定を正確に判定することができるような構造を採用することにより。束の抵抗は、CNT束の品質および濃度の尺度です。異なる長さの接触抵抗の束を決定するために測定すべきです。 45°の傾斜で金属...

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.

半導体技術との互換性低温カーボンナノチューブ垂直相互接続の作製

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 ビュー.  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.

ビデオ: 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.

製造、ち密化、および3Dカーボンナノチューブの微細構造のレプリカ成形

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

工学

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.

カーボンナノチューブアレイの濡れ特性をチューニングするための処置をアニーリングドライ酸化と真空

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.

コルク栓のように金ナノ粒子と窒素ドープカーボンナノチューブカップの合成と機能化

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.

書き込みおよび酸化物ナノ構造の低温特性評価

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.

レイヤ半導体ナノ構造のための集束イオンビーム技術と電気的評価を使用したオーミックコンタクト製作

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.

新規材料の低温磁気伝導測定のための高度な実験方法

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.

低圧走査型電子顕微鏡を用いたカーボンナノチューブの森の精密フライス

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.

によってナノ構造イットリア安定化ジルコニア（YSZ）足場の高温製作<em&gt;その場での</em&gt;カーボンテンプレート化キセロゲル

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.

3Dカーボンマイクロエレクトロメカニカルシステム（C-MEMS）の製作

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.

誘電泳動の流れ支援: 高性能低温硬化型ナノワイヤ デバイス作製のための低コストの方法

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