Low-temperature plasma-enhanced atomic layer deposition of HfO2/Al2O3 nanolaminate structure on Si

Abstract

HfO2/Al2O3 nanolaminate was deposited on a Si substrate by plasma-enhanced atomic layer deposition at 150 °C with in situ plasma treatment. Unilayer HfO2 and Al2O3 films were prepared for comparison. Films were treated by rapid thermal annealing at 870 °C in a nitrogen atmosphere for 30 s. Al atoms in the HfO2/Al2O3 nanolaminate diffuse into HfO2 layers during rapid thermal annealing, facilitating the formation of tetragonal HfO2. The HfO2/Al2O3 nanolaminate has an effective dielectric constant of 20.7, a breakdown electric field of 7.4 MV/cm, and leakage current of 2.3 × 10−5 mA/cm2 at a gate bias of Vg = −1 V. The valence band offset, conduction band offset, and the band gap of the film are 2.75, 1.96, and 5.83 eV, respectively.