Time-resolved analysis of the set process in an electrical phase-change memory device

Abstract

An experimental investigation was carried out on the kinetic nature of the set process in a phase change memory device by combined analyses of set voltage wave forms and time-resolved low-field resistances. As it turned out, the progress of a set process may be measured in terms of three characteristic times in sequence i.e., threshold switching time tth, incubation time for crystallization tinc, and complete set time tset. These characteristic times are supposed to demarcate, in some measure, different stages of crystallization in the memory material during a set process. Each of these times has a strong dependence on input pulse voltage and particularly threshold switching time tth was found to have an exponentially decaying dependence. The latter may be related to the decreasing capacitance of an amorphous phase-change material with approaching threshold switching.

Minimum Voltage for Threshold Switching in Nanoscale Phase-Change Memory

“…[14][15][16][17][18][19] Compared to the vertical device architecture commonly employed in integrated memory devices, 3,8,20 planar devices 4,7,14-19 offer important advantages for fundamental studies. First, four-probe geometry can be easily realized in NW devices, enabling the disentanglement of metal-NW contact issues from the properties of the NW.…”

Physics of switching and memory effects in chalcogenide glassy semiconductors

“…In [67], the exponential voltage dependence of the delay time t d was observed for Ge 2 Sb 2 Te 4 films 90 nm thick (Fig. 24).…”

On the RESET-SET transition in Phase Change Memories

“…5. This suggests that τ is not related to the GST phase transition but rather depends on the electrical switching time and measurement set-up parasitic effects [8]. Thus, P SET can be used as a characteristic parameter of the SET operation once the pulse amplitude is fixed, while the energy E SET provided to the cell during the same operation linearly increases with PW:…”

“…From there, other results show that the progress of a SET process may be measured in terms of three characteristics times in sequence i.e., switching time t SW , incubation time for crystallization t INC , and complete SET time t SET . D.-H. Kang et al [8] demonstrated that switching time t S also depends on the applied voltage pulse, and S. Kim and H.-S. P. Wong [7] recently showed that there is a minimum SET voltage that is determined by material properties and independent on geometry, opening new studies on cell performance optimization and scaling.…”

“…GST characteristics concerning SET and RESET states are related to the kinetics of phase transition, particularly for the amorphous to crystalline one, which involves a wide variety of material related phenomena, thus representing an arena of important technical and scientific issues in understanding and developing optimized materials and structures for phase change memory devices [8].…”