Nanowires are widely used as highly sensitive sensors for electrical detection of biological and chemical species. Modifying the band structure of strained-Si metal-oxide-semiconductor field-effect transistors by applying the in-plane tensile strain reportedly improves electron and hole mobility. The oxidation-induced Ge condensation increases the Ge fraction in a SiGe-on-insulator (SGOI) and substantially increases hole mobility. However, oxidation increases the number of surface states, resulting in hole mobility degradation. In this work, 3-aminopropyltrimethoxysilane (APTMS) was used as a biochemical reagent. The hydroxyl molecule on the oxide surface was replaced by the methoxy groups of the APTMS molecule. We proposed a surface plasma treatment to improve the electrical properties of SiGe nanowires. Fluorine plasma treatment can result in enhanced rates of thermal oxidation and speed up the formation of a self-passivation oxide layer. Like a capping oxide layer, the self-passivation oxide layer reduces the rate of follow-up oxidation. Preoxidation treatment also improved the sensitivity of SiGe nanowires because the Si-F binding was held at a more stable interface state compared to bare nanowire on the SiGe surface. Additionally, the sensitivity can be further improved by either the N2 plasma posttreatment or the low-temperature postannealing due to the suppression of outdiffusion of Ge and F atoms from the SiGe nanowire surface. 1. Introduction One-dimensional (1D) nanostructures, such as Si nanowires and ZnO nanorods, have been demonstrated as good candidates for ultrasensitive, miniaturized molecule sensors in biological, chemical, and optical applications [1–7]. The physical properties of biosensor devices fabricated from silicon depend on biochemical/molecular sensitivity. Nanoscale semiconductor processes can be used to improve chemical detection sensitivity. A basic phenomenon associated with the planar semiconductor process that can be exploited in biological sensors is surface potential modification. An important feature of nanowires is their ultrahigh surface-to-volume ratio, which is essential for ultrasensitive detection of chemical or biomolecular species. Since the conductivity of nanowires depends on the surface charges around their surfaces, one way to improve the sensitivity of the nanowire sensor is to use various biomolecular coatings for detecting viruses, proteins, ions, and DNA [8–10]. Strained silicon MOSFETs can be used to increase their electron and hole mobility. To maximize hole mobility, the fraction x of Si1-xGex
References
[1]
Y. Cui, Q. Wei, H. Park, and C. M. Lieber, “Nanowire nanosensors for highly sensitive and selective detection of biological and chemical species,” Science, vol. 293, no. 5533, pp. 1289–1292, 2001.
[2]
G. Brambilla, F. Xu, and X. Feng, “Fabrication of optical fibre nanowires and their optical and mechanical characterisation,” Electronics Letters, vol. 42, no. 9, pp. 517–519, 2006.
[3]
Y. K. Mishra, V. S. K. Chakravadhanula, V. Hrkac et al., “Crystal growth behaviour in Au-ZnO nanocomposite under different annealing environments and photoswitchability,” Journal of Applied Physics, vol. 112, no. 6, Article ID 064308, 2012.
[4]
S. Jebril, H. Kuhlmann, S. Müller et al., “Epitactically interpenetrated high quality ZnO nanostructured junctions on microchips grown by the vapor-liquid-solid method,” Crystal Growth and Design, vol. 10, no. 7, pp. 2842–2846, 2010.
[5]
D. Gedamu, S. Jebril, A. Schuchardt et al., “Examples for the integration of self-organized nanowires for functional devices by a fracture approach,” Physica Status Solidi B: Basic Research, vol. 247, no. 10, pp. 2571–2580, 2010.
[6]
Y. K. Mishra, S. Kaps, A. Schuchardt et al., “Fabrication of macroscopically flexible and highly porous 3D semiconductor networks from interpenetrating nanostructures by a simple flame transport approach,” Particle and Particle Systems Characterization, vol. 30, pp. 775–783, 2013.
[7]
D. Gedamu, I. Paulowicz, S. Kaps et al., “Rapid fabrication technique for interpenetrated ZnO nanotetrapod networks for fast UV sensor,” Advanced Materials, vol. 26, pp. 1541–1550, 2014.
[8]
F. Patolsky, G. Zheng, O. Hayden, M. Lakadamyali, X. Zhuang, and C. M. Lieber, “Electrical detection of single viruses,” Proceedings of the National Academy of Sciences of the United States of America, vol. 101, no. 39, pp. 14017–14022, 2004.
[9]
Z. Li, Y. Chen, X. Li, T. I. Kamins, K. Nauka, and R. S. Williams, “Sequence-specific label-free DNA sensors based on silicon nanowires,” Nano Letters, vol. 4, no. 2, pp. 245–247, 2004.
[10]
Z. Gao, A. Agarwal, A. D. Trigg et al., “Silicon nanowire arrays for label-free detection of DNA,” Analytical Chemistry, vol. 79, no. 9, pp. 3291–3297, 2007.
[11]
T. Tezuka, N. Sugiyama, and S. Takagi, “Fabrication of strained Si on an ultrathin SiGe-on-insulator virtual substrate with a high-Ge fraction,” Applied Physics Letters, vol. 79, no. 12, pp. 1798–1800, 2001.
[12]
S. Balakumar, S. Peng, K. M. Hoe et al., “SiGeO layer formation mechanism at the SiGe/oxide interfaces during Ge condensation,” Applied Physics Letters, vol. 90, no. 3, Article ID 032111, 2007.
[13]
F. K. LeGoues, R. Rosenberg, T. Nguyen, F. Himpsel, and B. S. Meyerson, “Oxidation studies of SiGe,” Journal of Applied Physics, vol. 65, no. 4, pp. 1724–1728, 1989.
[14]
H. Yang, D. Wang, H. Nakashima et al., “Influence of top surface passivation on bottom-channel hole mobility of ultrathin SiGe- and Ge-on-insulator,” Applied Physics Letters, vol. 93, no. 7, Article ID 072104, 2008.
[15]
J. Robertson, “Band offsets of wide-band-gap oxides and implications for future electronic devices,” Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures, vol. 18, no. 3, pp. 1785–1791, 2000.
[16]
K. R. Olasupo and M. K. Hatalis, “Leakage current mechanism in sub-micron polysilicon thin-film transistors,” IEEE Transactions on Electron Devices, vol. 43, no. 8, pp. 1218–1223, 1996.
[17]
M. Morita, S. Aritome, M. Tsukude, and M. Hirose, “A new SiO2 growth by fluorine-enhanced thermal oxidation,” in Proceedings of the International Electron Devices Meeting (IEDM '84), vol. 30, 1984.
[18]
P. Mohanty, I. Yoon, T. Kang et al., “Simple vapor-phase synthesis of single-crystalline Ag nanowires and single-nanowire surface-enhanced raman scattering,” Journal of the American Chemical Society, vol. 129, no. 31, pp. 9576–9577, 2007.
[19]
C. Li, D. Zhang, S. Han, X. Liu, T. Tang, and C. Zhou, “Diameter-controlled growth of single-crystalline In2O3 nanowires and their electronic properties,” Advanced Materials, vol. 15, no. 2, pp. 143–146, 2003.
[20]
H. H. Solak, D. He, W. Li et al., “Exposure of 38 nm period grating patterns with extreme ultraviolet interferometric lithography,” Applied Physics Letters, vol. 75, no. 15, pp. 2328–2330, 1999.
[21]
R. Nemutudi, N. J. Curson, N. J. Appleyard, D. A. Ritchie, and G. A. C. Jones, “Modification of a shallow 2DEG by AFM lithography,” Microelectronic Engineering, vol. 57-58, pp. 967–973, 2001.
[22]
X.-M. Yan, S. Kwon, A. M. Centreras, J. Bokor, and G. A. Somorjal, “Fabrication of large number density platinum nanowire arrays by size reduction lithography and nanoimprint lithography,” Nano Letters, vol. 5, no. 4, pp. 745–748, 2005.
[23]
Y.-K. Choi, T.-J. King, and C. Hu, “A spacer patterning technology for nanoscale CMOS,” IEEE Transactions on Electron Devices, vol. 49, no. 3, pp. 436–441, 2002.
[24]
K.-M. Chang, J.-M. Kuo, W.-C. Chao et al., “The Ge enhance the sensitivity for bio-sensor,” in Proceedings of the 2nd IEEE International Nanoelectronics Conference (INEC '08), pp. 811–814, March 2008.
[25]
C.-H. Lai, K.-M. Chang, C.-F. Chen et al., “Sensitivity enhancement in SiGe-on-insulator nanowire biosensor fabricated by top surface passivation,” Micro and Nano Letters, vol. 7, no. 8, pp. 729–732, 2012.
[26]
C. C. Chen, H. C. Lin, C. Y. Chang et al., “Improved plasma charging immunity in ultra-thin gate oxide with fluorine and nitrogen implantation,” in Proceedings of the 5th International Symposium on Plasma Process-Induced Damage, pp. 121–124, May 2000.
[27]
M. L. Green, E. P. Gusev, R. Degraeve, and E. L. Garfunkel, “Ultrathin ( ？nm) and Si-O-N gate dielectric layers for silicon microelectronics: understanding the processing, structure, and physical and electrical limits,” Journal of Applied Physics, vol. 95, p. 2057, 2001.
[28]
T. Hanrath and B. A. Korgel, “Influence of surface states on electron transport through intrinsic Ge nanowires,” Journal of Physical Chemistry B, vol. 109, no. 12, pp. 5518–5524, 2005.
[29]
H. Yang, D. Wang, H. Nakashima et al., “Influence of top surface passivation on bottom-channel hole mobility of ultrathin SiGe- and Ge-on-insulator,” Applied Physics Letters, vol. 93, no. 7, Article ID 072104, 2008.
[30]
S. Zhang, E. R. Hemesath, D. E. Perea, E. Wijaya, J. L. Lensch-Falk, and L. J. Lauhon, “Relative influence of surface states and bulk impurities on the electrical properties of ge nanowires,” Nano Letters, vol. 9, no. 9, pp. 3268–3274, 2009.
[31]
P. Chowdhury, A. I. Chou, K. Kumar, C. Lin, and J. C. Lee, “Improvement of ultrathin gate oxide and oxynitride integrity using fluorine implantation technique,” Applied Physics Letters, vol. 70, no. 1, pp. 37–39, 1997.
[32]
S.-D. Wang, W.-H. Lo, and T.-F. Lei, “CF4 plasma treatment for fabricating high-performance and reliable solid-phase-crystallized poly-Si TFTs,” Journal of the Electrochemical Society, vol. 152, no. 9, pp. G703–G706, 2005.
[33]
G. Shang, P. W. Peacock, and J. Robertson, “Stability and band offsets of nitrogenated high-dielectric-constant gate oxides,” Applied Physics Letters, vol. 84, no. 1, pp. 106–108, 2004.
[34]
K. Tse and J. Robertson, “Defect passivation in HfO2 gate oxide by fluorine,” Applied Physics Letters, vol. 89, no. 14, Article ID 142914, 2006.
[35]
C. S. Lai, W. C. Wu, K. M. Fan, J. C. Wang, and S. J. Lin, “Effects of post CF4 plasma treatment on the HfO2 thin film,” Japanese Journal of Applied Physics 1: Regular Papers and Short Notes and Review Papers B, vol. 44, no. 4, pp. 2307–2310, 2005.
[36]
K. M. Chang, B. N. Chen, and S. M. Huang, “The effects of plasma treatment on the thermal stability of HfO2 thin films,” Applied Surface Science, vol. 254, no. 19, pp. 6116–6118, 2008.
[37]
M. L. Green, E. P. Gusev, R. Degraeve, and E. L. Garfunkel, “Ultrathin (<4？nm) SiO2 and Si-O-N gate dielectric layers for silicon microelectronics: understanding the processing, structure, and physical and electrical limits,” Journal of Applied Physics, vol. 90, no. 5, pp. 2057–2121, 2001.
[38]
T. Hori, Gate Dielectrics and MOS ULSIs: Principles, Technologies, and Applications, vol. 34, Springer, New York, NY, USA, 1997.
[39]
L. D. Thanh, P. Balk, L. D. Thanh, and P. Balk, “Elimination and generation of Si-SiO2 interface traps by low temperature hydrogen annealing,” Journal of The Electrochemical Society, vol. 135, p. 1797, 1998.
[40]
R. Perera, A. Ikeda, R. Hattori, and Y. Kuroki, “Anomalous leakage current in silicon oxynitride thin films grown by microwave excited nitrogen plasma nitridation,” in Proceedings of the 7th International Conference on Properties and Applications of Dielectric Materials, pp. 1084–1087, June 2003.
[41]
N. Sugiyama, T. Tezuka, T. Mizuno et al., “Temperature effects on Ge condensation by thermal oxidation of SiGe-on-insulator structures,” Journal of Applied Physics, vol. 95, no. 8, pp. 4007–4011, 2004.
[42]
S. Balakumar, T. Jun Wei, C. H. Tung et al., “Fabrication of high Ge content SiGe layer on Si by Ge condensation technique,” in Proceedings of the 13th International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA '06), pp. 301–305, July 2006.
[43]
S. Balakumar, C. S. Ong, C. H. Tung et al., “Effects of annealing and temperature on SGOI fabrication using Ge condensation,” in Proceedings of the 13th International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA '06), pp. 150–153, July 2006.
[44]
S.-P. Jeng, T.-P. Ma, R. Canteri, M. Anderle, and G. W. Rubloff, “Anomalous diffusion of fluorine in silicon,” Applied Physics Letters, vol. 61, no. 11, pp. 1310–1312, 1992.
