IFNE NRNU «MEPHI»:

K. D. Vanyukhin

R. V. Zakharchenko

N. I. Kargin

M. V. Pashcov

L. A. Seidman

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.

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