Non-volatile memory devices based on Ge nanocrystals

The article presents the fabrication and characterization of NV (non-volatile) memory devices based on SiO2/Ge/SiO2 trilayer structures on Si wafers. The trilayer structures were obtained by using the magnetron sputtering method for the deposition of gate SiO2 and intermediate Ge layers and the rapid thermal oxidation for the growth of tunnel SiO2 layer. Rapid thermal annealing was performed for obtaining Ge nanocrystals embedded in the SiO2 gate oxide, as charge-storage elements. Two NV cross bar memory structures based on two cell sizes of 300x300 and 100x100m(2) were manufactured. Capacity-voltage curves were measured on the memory devices, at different frequencies in the 1kHz-10MHz range at room temperature (RT) for evidencing the hysteresis loops and for showing that the devices keep memory in time at these frequencies. We have obtained capacity-voltage hysteresis curves with large memory window up to 2V. We demonstrate that the trilayer structure SiO2/Ge/SiO2/on Si with Ge NCs embedded in the SiO2 gate oxide is suitable for NV memory applications having a large number of cells.