Study on the Structural Stability and Charge Trapping Properties of High-k HfO_2 and HFO_2/Al_2O_3/HfO_2 Stacks

摘要

In this work, high-k dielectric stacks of HfO_2 and HfO_2/Al_2O_3/HfO_2 (HAH) were deposited on SiO_2/ Si substrates by atomic layer deposition as charge trapping layers in charge trapping devices. The structural stability and the charge trapping characteristics of such stacks were investigated using Metal-Alumina-Hafnia-Oxide-Silicon (MAHOS) structure. The surface roughness of HfO_2 was stable up to 11 nm with the insertion of 0.2 nm thick Al_2O_3. The effect of the thickness of the HAH stack and the thickness of intermediate Al_2O_3 on charge trapping characteristics were investigated for MAHOS structure under various gate bias pulse with duration of 100 ms. The threshold voltage shift after programming and erase showed that the memory window was increased with increasing bias on gate. However, the programming window was independent of the thickness of HAH charge trapping layers. When the thickness of Al_2O_3 insertion increased from 0.2 nm to 1 nm, the erase window was decreased without change in the programming window.