Memory characteristics of Al2O3/LaAlO3/SiO2 multilayer structures with tunnel oxide thickness variation

Charge trap flash (CTF) memory devices are candidates to replace NAND flash devices. In this study, Pt/Al2O3/LaAlO3/SiO2/Si multilayer structures with lanthanum aluminate charge traps were fabricated for nonvolatile memory device applications. An aluminum oxide film was used as a blocking oxide for low power consumption in the program/erase operation and to minimize charge transport through the blocking oxide layer. The thickness of SiO2 as tunnel oxide layer was varied from 30 to 50 a"<<. Thicknesses of oxide layers were confirmed by high resolution transmission electron microscopy (HRTEM) and all the samples showed amorphous structure. From the C-V measurement, a maximum memory window of 3.4 V was observed when tunnel oxide thickness was 40 a"<<. In the cycling test for reliability, the 30 a"<< tunnel oxide sample showed a relatively large memory window reduction by repeated program/erase operations due to the high electric field of similar to 10 MV/cm through tunnel oxide. The other samples showed less than 10% loss of memory window during 10(4) cycles.