Submicron Nonvolatile Memory Cell Based on Reversible Phase Transition in Chalcogenide Glasses

Electrically rewritable nonvolatile memories using chalcogenide semiconductors were studied. The memory cell size was changed from 0.3 to 1.5 µmφ using a focused ion beam. This material can be used for nonvolatile random access memory. Reversible phase transition between the amorphous and crystalline states, which is accompanied by a considerable change in electrical resistivity, is exploited to store bits of information. The currents for write/erase were decreased with reducing memory cell size. In the memory cell of 0.6 µmφ, more than 104 repetition cycles of the phase transition were attained by the electric pulses. The voltages for the crystallization and amorphization processes were 2 V and 2.2 V, respectively.