**Author details**

Au wires on the 3D facet structure can be separated into four regions: flat bottom-surface, flat facet-surface, convex top facet-edge, and concave bottom facet-edge regions with resistances of *RB*, *RF*, *RTE*, and *RBE*, respectively, as shown in the inset of **Figure 15(b)**. The geometries of crystal grain boundaries in the polycrystalline Au wire may increase the electrical resistance [49]. The aggregation of crystal grain boundaries in the interconnect region, leading to the reduction in effective cross-sectional area, was attributed to the large *α* (≈30–180), i.e.,

We found that the conductivity passing through the interconnects is sensitive to the alignment of the facet-edges in the electric path, and the series configuration showed a 3–10-fold larger resistance than the parallel configuration, which originated from the increased resistivity across the facet-edges by a factor of �30–180, as calculated from the circuit model. This work provides a fundamental understanding of the impact of the 3D angular interconnects of a metal wire on electric transport and guidelines for the comprehensive investigation of the intrinsic interconnect transport properties on 3D structures, which is expected to produce critical

This chapter demonstrated the creation and evaluation of atomically ordered side-surfaces and inclined facet-surfaces in nanofabricated 3D Si architectures toward the realization of sequentially 3D integrated and stacked devices for More Moore [3]. Atomically flat and well-ordered 3D structured surfaces play an important role in creating high-performance films on arbitrarily oriented 3D surfaces, similar to films grown on ordinary planar substrates. We emphasized that electron diffraction techniques such as RHEED and LEED are convenient for evaluating atomically ordered 3D surfaces, while conventional SEM has no atomic resolution. The points for recognizing 3D surfaces in diffraction patterns were explained along the basic concept of diffraction in reciprocal space; the intersection of reciprocal lattice rods with an Ewald sphere led to diffraction spots on arcs, and the spots

By diffraction, we evaluated several systems with side- or facet-surfaces of Si 111 f g or 100 f g on Si 110 ð Þ or Si 001 ð Þ substrates, which were fabricated by lithography dry and wet etching processes, followed by annealing in vacuum. Metal deposition on the well-ordered 3D surfaces (followed by annealing) also produced well-ordered films of nanometer thickness fabricating with arbitrary orientations. This is one of the fundamental techniques for defect-free material construction on 3D architectures. The electrical conductivity of metal wires on atomically flat 3D facet-surfaces crossing facet-edges was also measured toward the design of nanoscale steric wiring. We consider that these techniques for creating and evaluating 3D surfaces are promising for the realization of future 3D architecture devices.

The authors appreciate Dr. Shohei Takemoto, Dr. Haoyu Yang, Prof. Hiroshi Daimon, and Prof. Hidekazu Tanaka for their contribution to these studies. We also thank Ms. Saeko Tonda, Ms. Michiko Sakuma, Mr. Shoichi Sakakihara, and Mr. Takeshi Ishibashi for their helpful support in the fabrication of 3D Si samples and Ms. Liliany N. Pamasi and Mr. Ken Maetani for their support in the diffraction measurement of Si samples. This work was partially supported by Adaptable and

*RB* = *RF*�*αRTE*,�*αRBE*.

**6. Conclusion**

benefits in the semiconductor industry.

*21st Century Surface Science - a Handbook*

elongate in the surface normal direction.

**Acknowledgements**

**106**

Azusa N. Hattori<sup>1</sup> and Ken Hattori<sup>2</sup> \*

1 Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan

2 Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Nara, Japan

\*Address all correspondence to: khattori@ms.naist.jp

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