Evaluation of DyScOx as an alternative blocking dielectric in TANOS memories with Si3N4 or Si-rich SiN charge trapping layers

Dysprosium scandate DyScOx with a kappa value of similar to 20 has been investigated as blocking dielectric in charge trapping memory capacitors. DyScOx films with 28 and 18 nm thicknesses are deposited by atomic layer deposition on two different kinds of silicon nitride used as charge trapping layer, while SiO2 is used as tunnel oxide and TaN is used as metal gate. Memory capacitors with Al2O3 as blocking layer with similar equivalent oxide thickness (EOT) to DyScOx are also characterized as benchmarks. DyScOx thermal stability on both Si3N4 and Si-rich SiN at annealing temperatures up to 900 degrees C demonstrates the complementary metal-oxide semiconductor process compatibility of the oxide. Especially when deposited on Si-rich SiN, comparable program and slightly better retention performance with Al2O3 are observed for DyScOx, whereas erase still needs to be improved. Some variations in the electrical performance are found between the DyScOx-based stacks with different charge trapping layer and have been discussed. Scaling the total stack EOT by reducing DyScOx thickness from 28 to 18 nm allows a large program/erase window, but with the penalty of an increased charge loss during retention. Our results suggest that the key factors in further improvement of DyScOx as blocking dielectric are the dielectric quality and leakage current. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3533765]