Boosting crystallization speed in ultrathin phase-change bridge memory device using Sb2Te3

Abstract

Ultrafast programming speed and superb data persistency are two contradictory characteristics that need to be reconciled in the development of non-volatile cache-type phase-change random access memory (PCRAM). Scaling down the dimension of PCRAM unit cell is expected to be a feasible approach to solve this issue. Here we employ a bridge-type device using a 4 nm-thick Sb2Te3 film to test this hypothesis. Thermal stability of the amorphous thin Sb2Te3 film is evidently enhanced with respect to the bulky ones. The phase-change bridge device also enables the fastest crystallization speed of 1 ns. Such swift crystallization should be mainly ascribed to the enhanced heterogeneous nucleation at interfaces. Yet the aggressive geometry shrinkage may induce severe retardation in crystal growth. Tuning these two crystallization kinetic factors needs to be considered in future design of ultrafast and persistent phase-change materials for high-density PCRAM application.