Switching Characterization and Failure Analysis of In₂Se₃ Based Phase Change Memory

Stoichiometric In 2 Se 3 films were deposited at room temperature. X-ray diffractometry (XRD) and field-emission scanning electron microscopy (FE-SEM) showed that the as-deposited films were amorphous and had very smooth surface morphology while the films annealed at 250°C or higher temperatures were crystalline and had a rough surface. A cross-point-type phase change memory device with a Mo/In 2 Se 3 /Mo layered structure was fabricated. Static mode (or DC mode) and pulsed mode switching tests were successfully carried out on these cross-point-type devices. In the DC mode test, the as-grown amorphous In 2 Se 3 resistor showed very high resistance in the low-voltage region. However, when it reached the threshold voltage, the electrical resistance of the device was markedly reduced due to the formation of an electrically conducting path (or a crystallized path). Pulsed mode switching performed on a phase change memory device with 0.7-µm-diameter contact hole showed that the resetting (amorphization) and setting (crystallization) of the device were achieved with a 70 ns pulse and a 1 µs pulse, respectively. After repeated switching, most of devices were stuck in the set state and could no longer be switched to the reset state. Cross-sectional SEM of these failed devices showed agglomerated voids near the interface between the In 2 Se 3 resistor and Mo electrode, which may be responsible for the stuck-set failure of the devices.