Evaluation of DyScO(x) as an alternative blocking dielectric in TANOS memories with Si(3)N(4) or Si-rich SiN charge trapping layers

Dysprosium scandate DyScO(x) with a kappa value of similar to 20 has been investigated as blocking dielectric in charge trapping memory capacitors. DyScO(x) 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 SiO(2) is used as tunnel oxide and TaN is used as metal gate. Memory capacitors with Al(2)O(3) as blocking layer with similar equivalent oxide thickness (EOT) to DyScO(x) are also characterized as benchmarks. DyScO(x) thermal stability on both Si(3)N(4) 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 Al(2)O(3) are observed for DyScO(x), whereas erase still needs to be improved. Some variations in the electrical performance are found between the DyScO(x)-based stacks with different charge trapping layer and have been discussed. Scaling the total stack EOT by reducing DyScO(x) 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 DyScO(x) as blocking dielectric are the dielectric quality and leakage current.