Electrical characterization of thin Al 2O 3 films grown by atomic layer deposition on silicon and various metal substrates

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Al 2O 3 films with thicknesses ranging from 30 to 3540 Å were grown in a viscous flow reactor using atomic layer deposition (ALD) with trimethylaluminum and water as the reactants. Growth temperatures ranged from 125 to 425 °C. The Al 2O 3 ALD films were deposited successfully on a variety of substrates including Au, Co, Cr, Cu, Mo, Ni, NiFe, NiMn, Pt, PtMn, Si, stainless steel, W, and ZnO. Electrical properties were characterized by current–voltage and capacitance–voltage measurements using a mercury probe. These measurements focused mainly on Al 2O 3 ALD films deposited on n-type Si(1 0 0) and on Mo-coated Si(1 0 0) substrates. Excellent insulating properties were observed for nearly all of the Al 2O 3 films. For a typical Al 2O 3 ALD film with a 120 Å thickness, leakage currents of <1 nA/cm 2 were observed at an applied electric field of 2 MV/cm. Fowler–Nordheim tunneling was observed at high electric fields and dielectric breakdown occurred only at ⩾5 MV/cm. Dielectric constants of k∼7.6 were measured for thick Al 2O 3 ALD films. The measured dielectric constant decreased with decreasing Al 2O 3 film thickness and suggested the presence of a thin interfacial oxide layer. For Al 2O 3 ALD films grown on n-type Si(1 0 0), capacitance measurements were consistent with an interfacial layer with a SiO 2 equivalent oxide thickness of 11 Å. Spectroscopic ellipsometry investigations also were in agreement with a SiO 2 interfacial layer with a 13 Å thickness.