Crystallization kinetics of In40Se60 thin films for phase change random access memory (PRAM) applications
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Chalcogenide based semiconductors have attracted much attention recently due to their applications in solid state devices (SSD). Chalcogenide phase change memory is considered as a potential replacement of flash memory due to its high storage density and archival stability. Phase change non-volatile semiconductor memory technology is based on an electrically initiated, reversible rapid amorphous-to-crystalline phase change process in multicomponent chalcogenide alloy materials similar to those used in rewritable optical disks. In order to view the suitability of a material for PRAM applications, it is necessary to investigate the crystallization behaviour of the material concerned. In the present work, a systematic investigation of crystallization kinetics of In40Se60 alloy has been made. Thin films of In40Se60 alloy were prepared by thermal evaporation using Edward Auto 306 evaporation system. Electrical measurements at room temperature and upon annealing at different heating rates were done by four point probe method using Keithley 2400 source meter interfaced with computer using LabView software. The dependence of sheet resistance on temperature showed a sudden drop in resistance at a specific temperature corresponding to the transition temperature at which the alloy change from amorphous to crystalline. The transition temperature was also found to increase with the heating rates. From the heating rate dependence of peak crystallization temperature (Tp) the activation energy for crystallization was determined using the Kissinger analysis. The films were found to have an electrical contrast of about six orders of magnitude between the as-deposited and the annealed states, a good quality for PRAM applications. The activation energy was determined to be 0.538±0.063eV.