Memory characteristics of Al2O3/La2O3/Al2O3 multi-layer films with various blocking and tunnel oxide thicknesses

In order to investigate charge trap characteristics with various thicknesses of blocking and tunnel oxide for application to non-volatile memory devices, we fabricated 5 and 15 nm Al2O3/5 nm La2O3/5 nm Al2O3 and 15 nm Al2O3/5 nm La2O3/5, 7.5, and 10 nm Al2O3 multi-stack films, respectively. The optimized structure was 15 nm Al2O3 blocking oxide/5 nm La2O3 trap layer/5 nm Al2O3 tunnel oxide film. The maximum memory window of this film of about 1.12 V was observed at 11 V for 10 ms in program mode and at −13 V for 100 ms in erase mode. At these program/erase conditions, the threshold voltage of the 15 nm Al2O3/5 nm La2O3/5 nm Al2O3 film did not change for up to about 104 cycles. Although the value of the memory window in this structure was not large, it is thought that a memory window of 1.12 V is acceptable in the flash memory devices due to a recently improved sense amplifier.