Journals →  Materialy Elektronnoi Tekhniki →  2013 →  #3 →  Back

PHYSICAL CHARACTERISTICS AND THEIR STUDY
ArticleName Research of Structure and Surface Morphology of Two–Layer Contact Ti/Al Metallization
ArticleAuthor K. D. Vanyukhin, R. V. Zakharchenko, N. I. Kargin, M. V. Pashcov, L. A. Seidman
ArticleAuthorData

IFNE NRNU «MEPHI»:

K. D. Vanyukhin

R. V. Zakharchenko

N. I. Kargin

M. V. Pashcov

L. A. Seidman

Abstract

Ti/Al/Ni/Au metallization widely used in the technology of GaN base devices have a very important imperfection: rough surface. There are different opinions about the causes of this imperfection: balling−up of molten aluminum or the appearance intermetallic melt phases in the Au–Al system. To check the effect of the former cause, we have studied the formation of rough surface after annealing of Ti/Al metallization which is used as a basis of many metallization systems for GaN. The substrates were made from silicon wafers covered with Si3N4 films (0.15 microns). On these substrates we deposited the Ti(12 nm)/Al(135 nm) metallization system. After this deposition the substrates were annealed in nitrogen for 30 s at 850 оС. The as−annealed specimens were tested for metallization sheet resistivity, appearance and surface morphology. We have shown that during annealing of the Ti/Al metallization system, mutual diffusion of metals and active interaction with the formation of intermetallic phases occur. This makes the metallization system more resistant to following anneals, oxidation and chemical etching. After annealing the surface of the Ti/Al metallization system becomes gently matted. However, large hemispherical convex areas (as in the Ti/Al/Ni/Au metallization system) do not form. Thus, the hypothesis on the balling−up of molten aluminum on the surface of the Ti/Al metallization system has not been confirmed.

keywords Ohmic contacts, contact metallizations, GaN, titanium− aluminium metallization, electron beam deposition method, thermal annealing of metallization
References

1. Chaturvedi, N. Mechanism of ohmic contact formation in AlGaN/GaN high electron mobility transistors / N. Chaturvedi, U. Zeimer, J. Wurfl, G. Trankle // Semicond. Sci. Technol. − 2006. − V. 21, N 2. − P. 175—179.
2. Abhishek, Motayed Electrical, thermal, and microstructural characteristics of Ti/Al/Ti/Au multilayer Ohmic contacts to n−type GaN / Abhishek Motayed, Ravi Bathe, M. C. Wood, O. S. Diouf, R. D. Vispute, S. N. Mohammad. // J. Appl. Phys. − 2003. − V. 93, N 2. − P. 1087—1094.
3. Jacobs, B. Towards integrated AlGaN/GaN based X−band high−power amplifiers. Proefschrift / B. Jacobs. − Eindhoven : Technische Universiteit Eindhoven, 2004. − 204 p.
4. Vasil'ev, A. G. SVCh−pribory i ustroistva na shirokozonnyh poluprovodnikah / A. G. Vasil'ev, Yu. V. Kolkovskii, Yu. A. Koncevoi. − M. : Tehnosfera, 2011. − 416 p.
5. Roccaforte, F. Nanoscale carrier transport in Ti/Al/Ni/Au Ohmic contacts on AlGaN epilayers grown on Si(111) / F. Roccaforte, F. Iucolano, F. Giannazzo, A. Alberti, V. Raineri // Appl. Phys. Lett. − 2006. − V. 89. P. 022103 1−3.
6. Jacobs, B. Optimisation of the Ti/Al/Ni/Au ohmic contact on AlGaN/GaN FET structures. / B. Jacobs, M. C. J. C. M. Kramer, E. J. Geluk, F. Karouta // J. Cryst. Growth. − 2002. − V. 241. − P. 15—18.
7. Kuznecov, G. D. Omicheskie kontakty k GaN / G. D. Kuznecov, V. P. Sushkov, A. R. Kushkov, I. G. Ermoshin, B. A. Bilalov // Izv. vuzov. Materialy elektron. tehniki. − 2009. − N 3. − S. 4—13.
8. Luther, B. P. Investigation of the mechanism for Ohmic contact formation in Al and Ti/Al contacts to n−type GaN / B. P. Luther, S. E. Mohney, T. N. Jackson, M. Asif Khan, Q. Chen, J. W. Yang // Appl. Phys. Lett. − 1997. − V. 70, N 1. − P. 57—59.

9. Yan, Wei. Analysis of the ohmic contacts of Ti/Al/Ni/Au to AlGaN/GaN HEMTs by the multi−step annealing process / Yan Wei, Zhang Renping, Du Yandong, Han Weihua, Yang Fuhua // J. Semicond. − 2012. − V. 33, N 6. − P. 064005 1−6.
10. Xin, H. P. Optimization of AlGaN/GaN HEMT Ohmic contacts for improved surface morphology with low contact resistance. / H. P. Xin, S. Poust, W. Sutton, D. Li, D. Lam, I. Smorchkova, R. Sandhu, B. Heying, J. Uyeda, M. Barsky, M. Wojtowicz, R. Lai. − Portland (USA), 2010. − P. 149 1−4.
11. Xin, Kong. Role of Ti/Al relative thickness in the formation mechanism of Ti/Al/Ni/Au Ohmic contacts to AlGaN/GaN heterostructures / Xin Kong, Ke Wei, Guoguo Liu, Xinyu Liu // J. Phys. D: Appl. Phys. − 2012. − V. 45. − P. 265101 1−8.
12. Gasser, S. M. Reaction of aluminum−on−titanium bilayer with GaN: Influence of the Al : Ti atomic ratio / S. M. Gasser, E. Kolawa, M.−A. Nicolet // J. Electron. Mater. − 1999. − V. 28. − P. 949—954.
13. Tonkie plenki. Vzaimnaya diffuziya i reakcii / Pod red. Dzh. Pouta, K. Tu, Dzh. Meiera. − M. : Mir, 1982. − 576 s.
14. Dobos, L. Al and Ti/Al contacts on n−GaN / L. Dobos, B. Pecz, L. Toth, Zs. J. Horvath, Z. E. Horvath, E. Horvath, A. Toth, B. Beaumont, Z. Bougrioua // Vacuum. − 2010. − V. 84. − P. 228—230.
15. Klopotov, A. A. Sistema Ti—Al. Simmetriinye aspekty / A. A. Klopotov, M. G. Dement'eva, A. I. Dolidchik, N. O. Solonicina, E. V. Kozlov // Fundamental'nye problemy sovremennogo materialovedeniya. − Tomsk, 2006. − P. 112—120.
16. Liu, Q. Z. A review of the metal−GaN contact technology / Q. Z. Liu, S. S. Lau // Solid State Electron. − 1998. − V. 42, N 5. − P. 677—691.
17. Feng, Q. The improvement of ohmic contact of Ti/Al/Ni/Au to AlGaN/GaN HEMT by multi−step annealing method / Q. Feng, L. M. Li, Y. Hao, J. Y. Ni, J. C. Zhang // Solid−State Electronics. − 2009. − V. 53, N 9. − P. 955—958.

Language of full-text russian
Full content Buy
Back