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Scanning probe microscopy for advanced nanoelectronics

Nature Electronics volume 2, pages 221–229 (2019)Cite this article

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Abstract

As the size of electronic devices continues to shrink, characterization methods capable of precisely probing localized properties become increasingly important. Scanning probe microscopy techniques can examine local phenomena, and conductive atomic force microscopy can, in particular, study local electromechanical properties. Such techniques have already played a valuable role in the development of nanoelectronics, but their capabilities remain relatively limited compared with the probe stations typically used to examine electronic devices. Here, we discuss the potential of conductive atomic force microscopy in nanoelectronics. We explore possible characterization strategies, enhanced electronics for the technique and improved multiprobe approaches. We also propose a multiprobe scanning probe microscopy system that combines different types of probes and could allow multiple nanofabrication and characterization experiments to be carried out simultaneously and under vacuum conditions.

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Fig. 1: History of the CAFM.
Fig. 2: Four-dimensional electrical characterization with CAFM.
Fig. 3: Multiprobe scanning probe microscopy.
Fig. 4: MPC-SPM.

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References

  1. Moore, G. E. Progress in digital integrated electronics. In Technical Digest. IEEE Int. Electron Devices Meet. 11–13 (IEEE, 1975); https://doi.org/10.1109/N-SSC.2006.4804410

    Google Scholar 

  2. International Roadmap for Devices and Systems (IRDS, 2017); https://irds.ieee.org/roadmap-2017

  3. Allport, P. P. et al. FOXFET biased microstrip detectors. Nucl. Instrum. Methods Phys. Res. A 310, 155–159 (1991).

    Google Scholar 

  4. Xiang, J. et al. Ge/Si nanowire heterostructures as high-performance field-effect transistors. Nature 441, 489–493 (2006).

    Google Scholar 

  5. Lanza, M. et al. Recommended methods to study resistive switching devices. Adv. Electron. Mater. 1, 1800143 (2018).

    Google Scholar 

  6. Murrell, M. P. et al. Spatially resolved electrical measurements of SiO2 gate oxides using atomic force microscopy. Appl. Phys. Lett. 62, 786–788 (1993).

    Google Scholar 

  7. Capella, B. & Dietler, G. Force–distance curves by atomic force microscopy. Surf. Sci. Rep. 34, 1–104 (1999).

    Google Scholar 

  8. Pan, C., Shi., Y., Hui, F., Grustan-Gutierrez, E. & Lanza, M. in Conductive Atomic Force Microscopy: Application in Nanomaterials (ed. Lanza, M.) Ch. 1 (Wiley-VCH, 2017).

  9. Lewis, D., Ignatov, A., Krol, S., Dekhter, R. & Strinkovsky, A. in Conductive Atomic Force Microscopy: Application in Nanomaterials (ed. Lanza, M.) Ch. 13 (Wiley-VCH, 2017).

  10. Lanza, M. et al. Electrical resolution during conductive AFM measurements under different environmental conditions and contact forces. Rev. Sci. Instrum. 81, 106110 (2010).

    Google Scholar 

  11. Iglesias, V., Jing, X. & Lanza, M. in Conductive Atomic Force Microscopy: Application in Nanomaterials (ed. Lanza, M.) Ch. 10 (Wiley-VCH, 2017).

  12. Iglesias, V. et al. Correlation between the nanoscale electrical and morphological properties of crystallized hafnium oxide-based metal oxide semiconductor structures. Appl. Phys. Lett. 97, 262906 (2010).

    Google Scholar 

  13. Binnig, G. & Rohrer, H. Scanning tunneling microscopy. Surf. Sci. 126, 236–244 (1983).

    Google Scholar 

  14. Frammelsberger, W., Benstetter, G., Kiely, J. & Stamp, R. C-AFM-based thickness determination of thin and ultra-thin SiO2 films by use of different conductive-coated probe tips. Appl. Surf. Sci. 253, 3615–3626 (2007).

    Google Scholar 

  15. Pirrotta, O. Leakage current though the poly-crystalline HfO2: trap densities at the grains and grain boundaries. J. Appl. Phys. 114, 134503 (2013).

    Google Scholar 

  16. Lanza, M. et al. Trapped charge and stress induced leakage current (SILC) in tunnel SiO2 layers of de-processed MOS non-volatile memory devices observed at the nanoscale. Microelectron. Reliab. 49, 1188–1191 (2009).

    Google Scholar 

  17. Muensterman, R. et al. Correlation between growth kinetics and nanoscale resistive switching properties of SrTiO3 thin films. J. Appl. Phys. 108, 124504 (2010).

    Google Scholar 

  18. Kajewski, D. et al. Local conductivity of epitaxial Fe-doped SrTiO3 thin films. Phase Transit. 84, 5–6 (2011).

    Google Scholar 

  19. Gomez-Navarro, C. et al. Tuning the conductance of single-walled carbon nanotubes by ion irradiation in the Anderson localization regime. Nat. Mater. 4, 534–539 (2005).

    Google Scholar 

  20. Uppal, H. J. Breakdown and degradation of ultrathin Hf-based (HfO2)x(SiO2)1–x gate oxide films. J. Vac. Sci. Technol. B 27, 443–447 (2009).

    Google Scholar 

  21. Lanza, M. A review on resistive switching in high-k dielectrics: a nanoscale point of view using conductive atomic force microscope. Materials 7, 2155–2182 (2014).

    Google Scholar 

  22. Giannazzo, F., Sonde, S., Rimini, E. & Raineri, B. Lateral homogeneity of the electronic properties in pristine and ion-irradiated graphene probed by scanning capacitance spectroscopy. Nanoscale Res. Lett. 6, 109 (2011).

    Google Scholar 

  23. Wang, Z. L. & Song, J. H. Piezoelectric nanogenerators based on zinc oxide nanowire arrays. Science 312, 242–246 (2006).

    Google Scholar 

  24. Hung, S. C., Su, Y. K., Chang, S. J. & Chen, Y. H. Vertically aligned GaN nanotubes — fabrication and current image analysis. Microelectron. Eng. 83, 2441–2445 (2006).

    Google Scholar 

  25. Lv, Y., Cui, J., Jiang, Z. M. & Yang, X. J. Composition and conductance distributions of single GeSi quantum rings studied by conductive atomic force microscopy combined with selective chemical etching. Nanotechnology 24, 065702 (2013).

    Google Scholar 

  26. Shi, Y. et al. Electronic synapses made of layered two-dimensional materials. Nat. Electron. 1, 458–465 (2018).

    Google Scholar 

  27. Wen, Y. et al. Multilayer graphene-coated atomic force microscopy tips for molecular junctions. Adv. Mater. 24, 3482–3485 (2012).

    Google Scholar 

  28. Frederix, P. L. T. M. et al. Assessment of insulated conductive cantilevers for biology and electrochemistry. Nanotechnology 16, 997–1005 (2005).

    Google Scholar 

  29. Xiao, J. X. et al. Room temperature ferroelectricity of hybrid organic-inorganic perovskites with mixed iodine and bromine. J. Mater. Chem. A 6, 9665–9676 (2018).

    Google Scholar 

  30. Han, T. et al. Photo-electrochemical water splitting in silicon based photocathodes enhanced by plasmonic/catalytic nanostructures. Mater. Sci. Eng. B 225, 128–133 (2017).

    Google Scholar 

  31. Bhaskar, U. K. et al. A flexoelectric microelectromechanical system on silicon. Nat. Nanotechnol. 11, 263–266 (2016).

    Google Scholar 

  32. Pan, C. et al. Suppression of nanowire clustering in hybrid energy harvesters. J. Mater. Chem. C. 4, 3646–3653 (2014).

    Google Scholar 

  33. Song, X. et al. Enhanced piezoelectric effect at the edges of stepped molybdenum dissulfide nanosheets. Nanoscale 9, 6237–6245 (2017).

    Google Scholar 

  34. Ranjan, A. et al. Analysis of quantum conductance, read disturb and switching statistics in HfO2 RRAM using conductive AFM. Microelectron. Reliab. 64, 172–178 (2016).

    Google Scholar 

  35. Benstetter, G., Hofer, A., Liu, D., Frammelsberger, W. & Lanza, M. in Conductive Atomic Force Microscopy: Application in Nanomaterials (ed. Lanza, M.) Ch. 3 (Wiley-VCH, 2017).

  36. Krause, O. in Conductive Atomic Force Microscopy: Application in Nanomaterials (ed. Lanza, M.) Ch. 2 (Wiley-VCH, 2017).

  37. Khun, N. W. Scratch-induced wear behavior of aluminum alloy under dry and wet conditions. J. Mechatron. 3, 301–306 (2016).

    Google Scholar 

  38. Simultaneous Electrical and Mechanical Property Mapping at the Nanoscale with PeakForce TUNA Application Note 132 (Bruker, 2011); https://www.bruker.com/products/surface-and-dimensional-analysis/atomic-force-microscopes/modes/modes/nanoelectrical-modes/pf-tuna.html

  39. Pacheco, L. & Martinez, N. F. in Conductive Atomic Force Microscopy: Application in Nanomaterials (ed. Lanza, M.) Ch. 12 (Wiley-VCH, 2017).

  40. Shi, Y. et al. In situ demonstration of the link between mechanical strength and resistive switching in resistive random-access memories. Adv. Electron. Mater. 1, 1400058 (2015).

    Google Scholar 

  41. Kim, K. S. et al. Large-scale pattern growth of graphene films for stretchable transparent electrodes. Nature 457, 706–710 (2009).

    Google Scholar 

  42. Yao, J. et al. Highly transparent nonvolatile resistive memory devices from silicon oxide and graphene. Nat. Commun. 3, 1101 (2012).

    Google Scholar 

  43. Pan, C. et al. Coexistence of grain-boundaries-assisted bipolar and threshold resistive switching in multilayer hexagonal boron nitride. Adv. Funct. Mater. 27, 1604711 (2017).

    Google Scholar 

  44. Hui, F. et al. Graphene and related materials for resistive random access memories. Adv. Electron. Mater. 3, 1600195 (2017).

    Google Scholar 

  45. Miao, F. et al. Anatomy of a nanoscale conduction channel reveals the mechanism of a high-performance memristor. Adv. Mater. 23, 5633–5640 (2001).

    Google Scholar 

  46. SuperFlat AFM. Kleindiek Nanotechnik https://www.nanotechnik.com/sf-afm.html (2019).

  47. Wen, C. et al. In situ observation of current generation in ZnO nanowire based nanogenerators using a CAFM integrated into an SEM. ACS Appl. Mater. Interfaces 11, 15183–15188 (2019).

    Google Scholar 

  48. Celano, U. Metrology and Physical Mechanisms in New Generation Ionic Devices (Springer Theses, Springer, 2016)

  49. Garcia, R., Knoll, A. W. & Riedo, E. Advanced scanning probe lithography. Nat. Nanotechnol. 9, 577–587 (2014).

    Google Scholar 

  50. Liu, D., Benstetter, G. & Frammelsberger, W. The effect of the surface layer of tetrahedral amorphous carbon films on their tribological and electron emission properties investigated by atomic force microscopy. Appl. Phys. Lett. 82, 3898 (2003).

    Google Scholar 

  51. Celano, U. et al. Conductive-AFM tomography for 3D filament observation in resistive switching devices. In 2013 IEEE Int. Electron Devices Meet. 21.6.1–21.6.4 (IEEE, 2013); https://doi.org/10.1109/IEDM.2013.6724679

  52. Chen, S. et al. On the limits of scalpel AFM for the three dimensional electrical characterization of nanomaterials. Adv. Funct. Mater. 28, 1802266 (2018).

    Google Scholar 

  53. Hammock, S. M. 3D c-AFM Imaging of Conductive Filaments in HfO 2 Resistive Switching Devices (Texas A&M University Libraries, 2017).

  54. Buckwell, M., Montesi, L., Hudziak, S., Mehonic, A. & Kenyon, A. J. Conductance tomography of conductive filaments in intrinsic silicon-rich silica RRAM. Nanoscale 7, 18030–18035 (2015).

    Google Scholar 

  55. Luria, J. et al. Charge transport in CdTe solar cells revealed by conductive tomographic atomic force microscopy. Nat. Energy 1, 16150 (2016).

    Google Scholar 

  56. Porti, M., Aguilera, L., Blasco, X., Nafria, M. & Aymerich, X. Reliability of SiO2 and high-k gate insulators: a nanoscale study with conductive atomic force microscopy. Microelectron. Eng. 84, 501–505 (2007).

    Google Scholar 

  57. Ranjan, A. et al. CAFM based spectroscopy of stress-induced defects in HfO2 with experimental evidence of the clustering model and metastable vacancy defect state. In 2016 IEEE Int. Reliability Phys. Symp. 7A-4-1–7A-4-7 (IEEE, 2016); https://doi.org/10.1109/IRPS.2016.7574576

  58. Jiang, L. et al. Dielectric breakdown in chemical vapor deposited hexagonal boron nitride. ACS Appl. Mater. Interfaces 9, 39758–39770 (2017).

    Google Scholar 

  59. Wu, Y. L., Lin, J. J., Chang, S. H. & Huang, C. Y. The degradation of thin silicon dioxide films subjected to pulse voltage stresses at nanoscale. ECS Trans. 28, 339–343 (2010).

    Google Scholar 

  60. Foissac, R., Blonkowski, S. & Kogelschatz, M. Nanoscale characterization of high-K/IL gate stack TDDB distributions after high-field prestress pulses. IEEE Trans. Device Mater. Reliab. 15, 298–307 (2015).

    Google Scholar 

  61. Lau, C. N., Stewart, D. R., Williams, S. & Bockrath, M. Direct observation of nanoscale switching centers in metal/molecule/ metal structures. Nano Lett. 4, 569–572 (2004).

    Google Scholar 

  62. Miao, F. et al. Anatomy of a nanoscale conduction channel reveals the mechanism of a high-performance memristor. Adv. Mater. 23, 5633–5640 (2011).

    Google Scholar 

  63. Park NX-Hivac: high vacuum atomic force microscope. Park Systems https://www.parksystems.com/index.php/products/small-sample-afm/park-nx-hivac (2019).

  64. Products. PrimeNano https://primenanoinc.com/products.html (2018).

  65. LT Nanoprobe. Scienta Omicron https://www.scientaomicron.com/en/products/lt-nanoprobe/1399 (2019).

  66. Higuchi, S., Kubo, O., Kuramochi, H., Aono, M. & Nakayama, T. A quadruple-scanning-probe force microscope for electrical property measurements of microscopic materials. Nanotechnology 22, 285205 (2011).

    Google Scholar 

  67. Klein, A. E., Janunts, N., Tunnermann, A. & Pertscch, T. Investigation of mechanical interactions between the tips of two scanning near-field optical microscopes. Appl. Phys. B 108, 737–741 (2012).

    Google Scholar 

  68. Nakayama, T. et al. Development and application of multiple-probe scanning probe microscopes. Adv. Mater. 24, 1675–1692 (2012).

    Google Scholar 

  69. Takahashi, M., Ko, H., Ushiki, T. & Iwata, F. Interactive nano manipulator based on an atomic force microscope for scanning electron microscopy. In Proc. 2011 International Symposium on Micro-NanoMechatronics and Human Science 495–500 (IEEE, 2011); https://doi.org/10.1109/MHS.2011.6102241

  70. Erlbacher, T., Yanev, V., Rommel, M., Bauer, A. J. & Frey, L. Gate oxide reliability at the nanoscale evaluated by combining conductive atomic force microscopy and constant voltage stress. J. Vac. Sci. Technol. B 29, 01AB08 (2011).

    Google Scholar 

  71. Matey, J. R. & Blanc, J. Scanning capacitance microscopy. J. Appl. Phys. 57, 1437 (1985).

    Google Scholar 

  72. Xu, J., Xu, J., Zhang, P., Li, W. & Chen, K. Nanoscale quantification of charge injection and transportation process in Si-nanocrystal based sandwiched structure. Nanoscale 5, 9971–9977 (2013).

    Google Scholar 

  73. Shi, L. & Majumdar, A. Scanning thermal microscopy of carbon nanotubes using batch-fabricated probes. Appl. Phys. Lett. 77, 4295–4297 (2000).

    Google Scholar 

  74. Gu, Y. et al. Near-field scanning photocurrent microscopy of a nanowire photodetector. Appl. Phys. Lett. 87, 04311 (2005).

    Google Scholar 

  75. Lai, K., Kundhikanjana, W., Kelly, M. & Shen, Z. X. Modeling and characterization of a cantilever-based near-field scanning microwave impedance microscope. Rev. Sci. Instrum. 79, 063703 (2008).

    Google Scholar 

  76. Aoki, N., Cunha, C. R., Akis, R., Ferry, D. K. & Ochiai, Y. Imaging of integer quantum Hall edge state in a quantum point contact via scanning gate microscopy. Phys. Rev. B 72, 155327 (2005).

    Google Scholar 

  77. Yeshua, T. et al. Micrometer to 15 nm printing of metallic inks with fountain pen nanolithography. Small 14, 1702324 (2017).

    Google Scholar 

  78. Piner, R. D., Zhu, J., Xu, F., Hong, S. & Mirkin, C. A. “Dip-pen” nanolithography. Science 283, 661–663 (1999).

    Google Scholar 

  79. Ribeiro-Palau, R. et al. Twistable electronics with dynamically rotatable heterostructures. Science 361, 690–693 (2018).

    Google Scholar 

  80. Sellier, H. et al. On the imaging of electron transport in semiconductor quantum structures by scanning-gate microscopy: successes and limitations. Semicond. Sci. Technol. 26, 064008 (2011).

    Google Scholar 

  81. Snow, E. S. & Campbell, P. M. Fabrication of Si nanostructures with an atomic force microscope. Appl. Phys. Lett. 64, 1932–1934 (1994).

    Google Scholar 

  82. Kado, H. & Tohda, T. Nanometer-scale recording on chalcogenide films with an atomic force microscope. Appl. Phys. Lett. 66, 2961–2962 (1995).

    Google Scholar 

  83. Houze, F., Meyer, R., Schneegans, O. & Boyer, L. Imaging the local electrical properties of metal surfaces by atomic force microscopy with conducting probes. Appl. Phys. Lett. 69, 1975–1977 (1996).

    Google Scholar 

  84. Sugimura, H. & Nakagiri, N. AFM lithography in constant current mode. Nanotechnology 8, A15–A18 (1997).

    Google Scholar 

  85. Lantz, M. A., O’Shea, S. J. & Welland, M. E. Characterization of tips for conducting atomic force microscopy in ultrahigh vacuum. Rev. Sci. Instrum. 69, 1757–1764 (1998).

    Google Scholar 

  86. Durkan, C., Welland, M. E., Chu, D. P. & Migliorato, P. Probing domains at the nanometer scale in piezoelectric thin films. Phys. Rev. B 60, 16198–16204 (1999).

    Google Scholar 

  87. Landau, S. A. et al. Scanning probe microscopy — a tool for the investigation of high-k materials. Appl. Surf. Sci. 157, 387–392 (2000).

    Google Scholar 

  88. Cai, L., Tabata, H. & Kawai, T. Probing electrical properties of oriented DNA by conducting atomic force microscopy. Nanotechnology 12, 211–216 (2001).

    Google Scholar 

  89. Bietsch, A. & Michel, B. Size and grain-boundary effects of a gold nanowire measured by conducting atomic force microscopy. Appl. Phys. Lett. 80, 3346–3348 (2002).

    Google Scholar 

  90. Hayakawa, J. et al. Current-driven switching of exchange biased spin-valve giant magnetoresistive nanopillars using a conducting nanoprobe. J. Appl. Phys. 96, 3440 (2004).

    Google Scholar 

  91. Masuda, H., Takeuchi, M. & Takahashi, T. Local photocurrent detection on InAs wires by conductive AFM. Ultramicroscopy 105, 137–142 (2005).

    Google Scholar 

  92. Szot, K., Speier, W., Bihlmayer, G. & Waser, A. R. Switching the electrical resistance of individual dislocations in single-crystalline SrTiO3. Nat. Mater. 5, 312–320 (2006).

    Google Scholar 

  93. Sire, C., Blonkowski, S., Gordon, M. J. & Baron, T. Statistics of electrical breakdown field in HfO2 and SiO2 films from millimeter to nanometer length scales. Appl. Phys. Lett. 91, 242905 (2007).

    Google Scholar 

  94. Cen, C. et al. Nanoscale control of an interfacial metal–insulator transition at room temperature. Nat. Mater. 7, 298–302 (2008).

    Google Scholar 

  95. Ramesha, G. G. & Sampath, S. Electrochemical reduction of oriented graphene oxide films: an in situ Raman spectroelectrochemical study. J. Phys. Chem. C. 113, 7985–7989 (2009).

    Google Scholar 

  96. Zhu, J., Lu, L. & Zeng, K. Nanoscale mapping of lithium-ion diffusion in a cathode within an all-solid-state lithium-ion battery by advanced scanning probe microscopy techniques. ACS Nano 7, 1666–1675 (2013).

    Google Scholar 

  97. Celano, U. et al. Three-dimensional observation of the conductive filament in nanoscaled resistive memory devices. Nano Lett. 14, 2401–2406 (2014).

    Google Scholar 

  98. Li, J. J. et al. Microscopic investigation of grain boundaries in organolead halide perovskite solar cells. ACS Appl. Mater. Interfaces 7, 28518–28523 (2015).

    Google Scholar 

  99. Drogeler, M. et al. Spin lifetimes exceeding 12 ns in graphene nonlocal spin valve devices. Nano Lett. 16, 3533–3539 (2016).

    Google Scholar 

  100. Liu, X. et al. Scanning probe nanopatterning and layer-by-layer thinning of black phosphorus. Adv. Mater. 29, 1604121 (2017).

    Google Scholar 

  101. Okino, H. et al. In situ resistance measurements of epitaxial cobalt silicide nanowires on Si(110). Appl. Phys. Lett. 86, 233108 (2015).

    Google Scholar 

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Acknowledgements

This work has been supported by the Young 1000 Global Talent Recruitment Program of the Ministry of Education of China, the Ministry of Science and Technology of China (grant no. BRICS2018-211-2DNEURO), the National Natural Science Foundation of China (grants no. 61502326, 41550110223, 11661131002, 61874075), the Jiangsu Government (grant no. BK20150343), the Ministry of Finance of China (grant no. SX21400213) and the Young 973 National Program of the Chinese Ministry of Science and Technology (grant no. 2015CB932700). The Collaborative Innovation Center of Suzhou Nano Science and Technology, the Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, the Priority Academic Program Development of Jiangsu Higher Education Institutions, and the 111 Project from the State Administration of Foreign Experts Affairs are also acknowledged. F.H. acknowledges support from the Technion-Guangdong Fellowship. D. Lewis and R. Dechter from Nanonics, T. Yang from Park Systems, L. Pacheco from Concept Scientific Instruments, O. Krause from Nano World and W. Frammelsberger from Deggendorf Institute of Technology are acknowledged for helpful discussions. X. Jing (Soochow University) and E. Sahagún (Scixel) are acknowledged for support with figure preparation.

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  1. Institute of Functional Nano and Soft Materials, Collaborative Innovation Center of Suzhou Nanoscience and Technology, Soochow University, Suzhou, China

    Fei Hui & Mario Lanza

  2. Materials Science and Engineering Department, Technion — Israel Institute of Technology, Haifa, Israel

    Fei Hui

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F.H. and M.L discussed the project, carried out the literature research, wrote the manuscript and prepared the figures.

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Correspondence to Mario Lanza.

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Supplementary Table 1

Ideal features of a single-tip CAFM for characterization of nanoelectronics.

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Hui, F., Lanza, M. Scanning probe microscopy for advanced nanoelectronics. Nat Electron 2, 221–229 (2019). https://doi.org/10.1038/s41928-019-0264-8

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