Nonvolatile Memory Based on Phase Transition in Chalcogenide Thin Film

Electrically erasable nonvolatile memories based on the reversible amorphous-crystalline phase transition were studied. In the appropriate set- and reset-conditions, more than 105 repetition cycles of write/erase were attained in the memory devices composed of As-Sb-Te films. Deterioration of memory devices was caused by the phase separation due to the segregation of crystallites in the active region in the memory cells and in the peripheral area around the active region. The phase separation in the peripheral area around the active region still occurred even in the memory devices using well-designed materials. Deterioration phenomena can be greatly suppressed by the reduction of the device geometry.