J. Semicond. > Volume 36 > Issue 12 > Article Number: 123006

Interface annealing characterization of Ti/Al/Au ohmic contacts to p-type 4H-SiC

Chao Han 1, , Yuming Zhang 1, , , Qingwen Song 1, 2, , Xiaoyan Tang 1, , Hui Guo 1, , Yimen Zhang 1, , Fei Yang 3, and Yingxi Niu 3,

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Abstract: Ti/Al/Au ohmic contacts to p-type 4H-SiC in terms of a different annealing time and Ti composition are reported. At 1050℃, proper increase in annealing time plays a critical role in the Schottky to ohmic contact conversion. With the optimized annealing time, the contact with a high Ti content yields a lower specific contact resistivity(ρc) of 6.4×10-5 Ω·cm2 compared with the low-Ti contact. The annealed surface morphology and phase resultants were examined by scanning electron microscopy(SEM) and X-ray diffraction(XRD), respectively. For the better ohmic contact, element distribution and chemical states were qualitatively identified by X-ray photoelectron spectroscopy(XPS) depth analysis. In particular, the presence of C and a Si-related phase was discussed and associated with the change in the surface status of the as-grown epilayer of 4H-SiC during annealing. The results reveal that the out-diffused C and Si atoms, with an approximate atomic ratio of 1:1 in the contact layer, can combine to form an amorphous Si-C state. The polycrystalline graphite instead of an unreacted C cluster in the whole alloyed structure and an extra nanosize graphite flake on the outermost surface of the annealed contact were confirmed by Raman spectroscopy.

Key words: 4H-SiCp-typeohmic contacttitaniumaluminumgold

Abstract: Ti/Al/Au ohmic contacts to p-type 4H-SiC in terms of a different annealing time and Ti composition are reported. At 1050℃, proper increase in annealing time plays a critical role in the Schottky to ohmic contact conversion. With the optimized annealing time, the contact with a high Ti content yields a lower specific contact resistivity(ρc) of 6.4×10-5 Ω·cm2 compared with the low-Ti contact. The annealed surface morphology and phase resultants were examined by scanning electron microscopy(SEM) and X-ray diffraction(XRD), respectively. For the better ohmic contact, element distribution and chemical states were qualitatively identified by X-ray photoelectron spectroscopy(XPS) depth analysis. In particular, the presence of C and a Si-related phase was discussed and associated with the change in the surface status of the as-grown epilayer of 4H-SiC during annealing. The results reveal that the out-diffused C and Si atoms, with an approximate atomic ratio of 1:1 in the contact layer, can combine to form an amorphous Si-C state. The polycrystalline graphite instead of an unreacted C cluster in the whole alloyed structure and an extra nanosize graphite flake on the outermost surface of the annealed contact were confirmed by Raman spectroscopy.

Key words: 4H-SiCp-typeohmic contacttitaniumaluminumgold



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Stoltz S E, Starnberg H I, Barsoum M W. Core level and valence band studies of layered Ti3SiC2 by high resolution photoelectron spectroscopy[J]. J Phys Chem Sol, 2003, 64(12): 2321.

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Lu H, Shen D H, Deng X F. Study of the Al/graphite interface[J]. Chin Phys B, 2001, 10(9): 832.

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Marinova T, Yakimova R, Krastev V. Interfacial reactions and ohmic contact formation in the Ni/Al-6H SiC system[J]. J Vac Sci Technol B, 1996, 14(5): 3252.

[30]

Veneroni A, Omarini F, Moscatelli D. Modeling of epitaxial silicon carbide deposition[J]. J Cryst Growth, 2005, 275(1/2): 295.

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Gao M, Tsukimoto S, Goss S H. Role of interface layers and localized states in TiAl-based ohmic contacts to p-type 4H-SiC[J]. J Electron Mater, 2007, 36(4): 277.

[32]

Tsukimoto S, Ito K, Wang Z C. Growth and microstructure of epitaxial Ti3SiC2 contact layers on SiC[J]. Mater Trans, 2009, 50(5): 1071.

[33]

Andreev A N, Rastegaeva M G, E'abanin A I. High temperature Ti-Al-based ohmic contacts to p-6H-SiC[J]. International Semiconductor Conference, Sinaia, Romania, 1998.

[34]

Lu W, Mitchel W C, Collins W E. Ohmic contacts on p-type silicon carbide using carbon films[J]. US Patent, 2004.

[1]

Kimoto T. SiC technologies for future energy electronics[J]. Symposium on VLSI Technology, Honolulu, USA, 2010.

[2]

Wurfl I P, Krutsinger R, Torvik J T. 4H-SiC bipolar junction transistor with high current and power density[J]. Solid-State Electron, 2003, 47(2): 229.

[3]

Lee H, Domeij M, Zetterling C. Low-forward-voltage-drop 4H-SiC BJTs without base contact implantation[J]. IEEE Trans Electron Devices, 2008, 55(8): 1907.

[4]

Rumyantsev S L, Levinshtein M E, Shur M S. High current(1300 A) optical triggering of a 12 kV 4H-SiC thyristor[J]. Semicond Sci Technol, 2013, 28(4): 045016.

[5]

Laariedh F, Lazar M, Cremillieu P. The role of nickel and titanium in the formation of ohmic contacts on p-type 4H-SiC[J]. Semicond Sci Technol, 2013, 28(4): 045007.

[6]

Vivona M, Greco G, Franco S D. Comparative study of the current transport mechanisms in Ni2Si ohmic contacts on n-and p-type implanted 4H-SiC[J]. Mater Sci Forum, 2014, 778.

[7]

Lee S K, Zetterling C, Ostling M. Low resistivity ohmic contacts to silicon carbide for high temperature device applications[J]. Microelectron Eng, 2002, 60(1/2): 261.

[8]

Lu W, Mitchel W C, Crenshaw T. An investigation of Ti/Al/C composite films on p-type SiC[J]. MRS Spring Meeting, San Francisco, USA, 2003.

[9]

Roccaforte F, Frazzetto A, Greco G. Critical issues for interfaces to p-type SiC and GaN in power devices[J]. Appl Surf Sci, 2012, 258(21): 8324.

[10]

Thierry-Jebali N, Vo-Ha A, Carole D. Very low specific contact resistance measurements made on a highly p-type doped 4H-SiC layer selectively grown by vapor-liquid-solid transport[J]. Appl Phys Lett, 2013, 102(21): 212108.

[11]

Jennings M R, Fisher C A, Walker D. On the Ti3SiC2 metallic phase formation for robust p-type 4H-SiC ohmic contacts[J]. Mater Sci Forum, 2014, 778.

[12]

Johnson B J, Capano M A. Mechanism of ohmic behavior of Al/Ti contacts to p-type 4H-SiC after annealing[J]. J Appl Phys, 2004, 95(10): 5616.

[13]

Wang Z C, Tsukimoto S, Saito M. Ohmic contacts on silicon carbide:the first monolayer and its electronic effect[J]. Phys Rev B, 2009, 80(24): 245303.

[14]

Wang Z C, Saito M, Tsukimoto S. Terraces at ohmic contact in SiC electronics:structure and electronic states[J]. J Appl Phys, 2012, 111(11): 113717.

[15]

Kolaklieva L, Kakanakov R, Avramova I. Nanolayered Au/Ti/Al ohmic contacts to p-type SiC:electrical, morphological and chemical properties depending on the contact composition[J]. Mater Sci Forum, 2007, 556.

[16]

Laariedh F, Lazar M, Cremillieu P. Investigations on Ni-Ti-Al ohmic contacts obtained on p-type 4H-SiC[J]. Mater Sci Forum, 2012, 711: 169.

[17]

Nakatsuka O, Takei T, Koide Y. Low resistance TiAl ohmic contacts with multi-layered structure for p-type 4H-SiC[J]. Mater Trans, 2002, 43(7): 1684.

[18]

Mysliwiec M, Sochacki M, Kisiel R. TiAl-based ohmic contacts on p-type SiC[J]. 34th Int Spring Seminar on Electronics Technology, Košice, Slovakia, 2011.

[19]

Amy F, Chabal Y J. Interaction of H, O2, and H2O with 3C-SiC surfaces[J]. J Chem Phys, 2003, 119(12): 6023.

[20]

Ma G L, Zhang Y M, Zhang Y M. Study on the chemical states of the surface of SiC epilayer[J]. Chin Phys Soc, 2008, 57(7): 4119.

[21]

Vassilevski K, Zekentes K, Tsagaraki K. Phase formation at rapid thermal annealing of Al/Ti/Ni ohmic contacts on 4H-SiC[J]. Mater Sci Eng, 2001, 80(1-3): 370.

[22]

Vang H, Lazar M, Brosselard P. Ni-Al ohmic contact to p-type 4H-SiC[J]. Superlattice Microst, 2006, 40(4-6): 626.

[23]

Han Linchao, Shen Huajun, Liu Kean. Improved adhesion and interface ohmic contact on n-type 4H-SiC substrate by using Ni/Ti/Ni[J]. Journal of Semiconductors, 2014, 35(7): 072003.

[24]

Ferrari A C, Robertson J. Interpretation of Raman spectra of disordered and amorphous carbon[J]. Phys Rev B, 2000, 61(20): 14.

[25]

Lu W, Mitchel W C, Landis G. Catalytic graphitization and ohmic contact formation on 4H-SiC[J]. J Appl Phys, 2003, 93(9): 5397.

[26]

Lu W, Mitchel W C, Thorntong C A. Carbon structural transitions and ohmic contacts on 4H-SiC[J]. J Electron Mater, 2003, 32(5): 426.

[27]

Stoltz S E, Starnberg H I, Barsoum M W. Core level and valence band studies of layered Ti3SiC2 by high resolution photoelectron spectroscopy[J]. J Phys Chem Sol, 2003, 64(12): 2321.

[28]

Lu H, Shen D H, Deng X F. Study of the Al/graphite interface[J]. Chin Phys B, 2001, 10(9): 832.

[29]

Marinova T, Yakimova R, Krastev V. Interfacial reactions and ohmic contact formation in the Ni/Al-6H SiC system[J]. J Vac Sci Technol B, 1996, 14(5): 3252.

[30]

Veneroni A, Omarini F, Moscatelli D. Modeling of epitaxial silicon carbide deposition[J]. J Cryst Growth, 2005, 275(1/2): 295.

[31]

Gao M, Tsukimoto S, Goss S H. Role of interface layers and localized states in TiAl-based ohmic contacts to p-type 4H-SiC[J]. J Electron Mater, 2007, 36(4): 277.

[32]

Tsukimoto S, Ito K, Wang Z C. Growth and microstructure of epitaxial Ti3SiC2 contact layers on SiC[J]. Mater Trans, 2009, 50(5): 1071.

[33]

Andreev A N, Rastegaeva M G, E'abanin A I. High temperature Ti-Al-based ohmic contacts to p-6H-SiC[J]. International Semiconductor Conference, Sinaia, Romania, 1998.

[34]

Lu W, Mitchel W C, Collins W E. Ohmic contacts on p-type silicon carbide using carbon films[J]. US Patent, 2004.

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C Han, Y M Zhang, Q W Song, X Y Tang, H Guo, Y M Zhang, F Yang, Y X Niu. Interface annealing characterization of Ti/Al/Au ohmic contacts to p-type 4H-SiC[J]. J. Semicond., 2015, 36(12): 123006. doi: 10.1088/1674-4926/36/12/123006.

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Manuscript received: 28 April 2015 Manuscript revised: Online: Published: 01 December 2015

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