Double nitridation of crystalline ZrO2/Al2O3 buffer gate stack with high capacitance, low leakage and improved thermal stability

Abstract The gate dielectric stack composed of crystalline ZrO 2 and Al 2 O 3 buffer layer treated with double nitridation was developed to reduce the capacitance equivalent thickness (CET), leakage current density ( J g ), interfacial state density ( D it ), and enhance thermal stability as well. A high dielectric constant of the gate stack was provided by the crystalline ZrO 2 with tetragonal/cubic phase. The J g and D it were suppressed by the insertion of the Al 2 O 3 buffer layer treated with remote NH 3 plasma nitridation because of the deactivation of the oxygen vacancies and the well passivation of the Si dangling bonds. A further nitridation using remote N 2 plasma on ZrO 2 was carried out to reduce the CET and J g by the enhancement of the dielectric constant and the deactivation of the grain boundaries and oxygen vacancies. Accordingly, a low CET of 1.09 nm, J g of 3.43 × 10 −5 A/cm 2 , and D it of 3.35 × 10 11 cm −2 eV −1 were achieved in the crystalline ZrO 2 /Al 2 O 3 buffer gate stack treated with the double nitridation. The hysteresis was also minimized significantly by the post-deposition annealing at 800 °C, which is attributed to the enhanced thermal stability. The results indicate that the crystalline high- K dielectrics/buffer layer with double nitridation treatments is a promising gate stack structure beneficial to the sub-nanometer CET scaling in the future.