A study of the memory characteristics of multilayer structures with varying compositions of the LAO charge trap

Charge trap flash (CTF) memory devices are candidates to replace NAND flash devices. In this study, Si multilayer structures with lanthanum aluminum oxide 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 operations and to minimize charge transport through the blocking oxide layer. The thickness of SiO₂ as a tunnel oxide layer was 40 Å. The thicknesses of the oxide layers were determined by high resolution transmission electron microscopy (HRTEM) and all samples showed amorphous structures. The composition of the charge trapping lanthanum aluminum oxide were analyzed using X-ray photoelectron spectroscopy (XPS). From C-V measurements, a maximum memory window of 3.48 V was observed when the flow rate ratio was La: Al = 3: 3. The memory properties were affected by the band structure, trap energy level/density, and dielectric constant of the charge trap layer. In the reliability cycling tests, all samples maintained their initial memory window over 10⁴ cycles.