Effects of Low Temperature O_2 Treatment on the Electrical Properties of Amorphous LaAlO_3 Films Made by Atomic Layer Deposition

摘要

Amorphous LaAlO_3 films were deposited on hydrogen-terminated silicon substrates by atomic layer deposition (ALD) at 300 ℃. The precursors were lanthanum tris(N,N'-diisopropylformamidinate), trimethylaluminum (TMA) and water. Capacitance-voltage measurements made on ALD MoN/LaAlO_3/Si stacks showed humps especially at low frequencies. They were effectively removed by O_2 treatment at 300 ℃ without affecting the dielectric constant (k～15). The O_2 treatment can be carried out either after deposition of a LaAlC«3 film, or after each ALD cycle. The O_2 treatment also lowered the leakage current from 80 mA cm~(-2) to 1 mA cm~(-2) for EOT = 1.3 nm. This indicates that oxygen vacancies are the main defects in as-deposited LaAlO_3. Oxygen treated LaAlO_3 is one of the best candidates for future high-k dielectric material due to its low leakage, low defect density and abrupt interface with silicon.