Fabrication of NbTiN Tunnel Junctions for Superconducting Logic Circuits

超导逻辑电路 NbTiN 隧道结的制造

• 批准号: 11650313
• 负责人: MYOREN Hiroaki
• 金额: $ 2.24万
• 依托单位: Saitama University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11650313/
• 关键词: NbTiN; Superconducting Tunnel Junctions; Dc Magnetron Sputtering; Single Flux Quantum Logic Circuits; Superconducting Circuits; NAND Gate; NOR Gate; 直流マグネトロンスパッタ法; 原子間力顕微鏡; X線回折法

We prepared Nb_<1-x>Ti_xN (NbTiN) thin films by reactive do magnetron sputtering without intentional heating. Superconducting properties were strongly related to sputtering conditions. Lattice parameters of NbTiN films approached that of bulk NbTiN with decreasing the N_2 mole fraction in Ar and N_2 sputtering gas mixture. The film orientation was also strongly related with the sputtering conditions such as gas pressure. NbN thin films could grow epitaxially on MgO(100) substrates and showed very smooth surfaces. We found that smooth NbTiN films could be obtained on MgO(100) substrates with epitaxially grown NbN template layer. Superconducting critical temperature of NbTiN films were up to 14.5 K.We prepared AlN thin films for tunnel barriers and found that smooth AlN thin layers could be obtained by reactive dc magnetron sputtering with relatively small sputtering power of 50 W. Etching rate of AlN layers was decreased with increasing CF_4 gas pressure and AlN layer could behave as a etching stopping layer. We fabricated NbTiN/AlN/NbTiN tunnel structure and observed I-V curves with the superoonducting energy-gap structure.We successfully designed and fabricated single flux quantum (SFQ) NAND and NOR gates. We designed mask layouts of the gates assuming a 2.5 kA/cm^2 Nb/AlO_x/Nb junction process and optimized device parameters using an SFQ circuit-optimizing tool. Fabricated NAND and NOR gates had a critical margin more than ±20% for low-frequency operation. Bias margin for a fabricated NAND gate exceed ±25%.

采用反应磁控溅射法制备了Nb_<1-x>Ti_xN （NbTiN）薄膜。超导性能与溅射条件密切相关。在Ar和N_2溅射混合气体中，随着N_2摩尔分数的降低，NbTiN薄膜的晶格参数与体NbTiN接近。薄膜的取向也与溅射条件（如气体压力）密切相关。NbN薄膜可以在MgO（100）衬底上外延生长，表面非常光滑。我们发现外延生长NbN模板层可以在MgO（100）衬底上获得光滑的NbTiN薄膜。NbTiN薄膜的超导临界温度高达14.5 K。我们制备了用于隧道势垒的AlN薄膜，发现反应直流磁控溅射可以获得光滑的AlN薄膜，溅射功率相对较小，为50 W。随着CF_4气体压力的增加，AlN层的刻蚀速率降低，AlN层可以作为刻蚀停止层。我们制作了NbTiN/AlN/NbTiN隧道结构，并利用超导能隙结构观察了I-V曲线。我们成功地设计和制造了单通量量子（SFQ） NAND和NOR门。我们设计了假设2.5 kA/cm^2 Nb/AlO_x/Nb结工艺的栅极掩模布局，并使用SFQ电路优化工具优化了器件参数。制造的NAND和NOR门在低频工作时的临界裕度大于±20%。制造的NAND栅极的偏置余量超过±25%。

项目成果

NAND Gate for SFQ Logic Circuits

SFQ 逻辑电路的与非门

• 发表时间: 2000
• 期刊: IEICE Trans. Electron E83-C
• 作者: Myoren H.;Ono S.;Takeda S.
• 通讯作者: Takeda S.

Design of single-flux-quantum universal gates with a wide operating margin

具有较宽运行裕度的单通量量子通用门的设计

• 发表时间: 2003
• 期刊: Supercond.Sci.Technol. 16
• 作者: K.T.Liu;Y.K.Su;S.J.Chang;K.Onomitsu;Y.Horikoshi;Myoren H.et al.
• 通讯作者: Myoren H.et al.

Hiroaki Myoren, Seiichiro Ono, Susumu Takada: "Universal NAND Gate based on Single Flux Quntum Logic"Applied Superconductivity 1999. 167・2. 741-744 (2000)

Hiroaki Myoren、Seiichiro Ono、Susumu Takada：“基于单通量量子逻辑的通用 NAND 门”应用超导 1999. 741-744 (2000)

Universal NAND Gate based on Single Flux Quantum Logic

基于单通量量子逻辑的通用与非门

• 发表时间: 1999
• 期刊: Applied Superconductivity 167
• 作者: Myoren H.;Ono S.;Takada S.
• 通讯作者: Takada S.

Hiroaki Myoren,Seiichiro Ono and Susumu Takada: "Universal NAND Gate based on Single Flux Quntum Logic"Applied Superconductivity 1999. 167・2. 741-744 (2000)

Hiroaki Myoren、Seiichiro Ono 和 Susumu Takada：“基于单通量量子逻辑的通用 NAND 门”应用超导 1999. 167・2（2000）