Pulse number control of electrical resistance for multi-level storage based on phase change

Phase change nonvolatile memory devices composed of SeSbTe chalcogenide semiconductor thin film were fabricated. The resistivity of the SeSbTe system was investigated to apply to multi-level data storage. The chalcogenide semiconductor acts as a programmable resistor that has a large dynamic range. The resistance of the chalcogenide semiconductor can be set to intermediate resistances between the amorphous and crystalline states using electric pulses of a specified power, and it can be controlled by repetition of the electric pulses. The size of the memory cell used in this work is 200 nm thick with a contact area of 1 µm diameter. The resistance of the chalcogenide semiconductor gradually varies from 41 kΩ to 840 Ω within octal steps. The resistance of the chalcogenide semiconductor decreases with increasing number of applied pulses. The step-down characteristic of the resistance can be explained as the crystalline region of the active phase change region increases with increasing number of applied pulses. The extent of crystallization was also estimated by the overall resistivity of the active region of the memory cell.

[1]  S. Ovshinsky.  Optical Cognitive Information Processing – A New Field , 2004 .

[2]  D. Ielmini,et al.  Intrinsic Data Retention in Nanoscaled Phase-Change Memories—Part I: Monte Carlo Model for Crystallization and Percolation , 2006, IEEE Transactions on Electron Devices.

[3]  K. Nakayama,et al.  Submicron Nonvolatile Memory Cell Based on Reversible Phase Transition in Chalcogenide Glasses , 2000 .

[4]  D. Kumar,et al.  Investigation of compensation effect for isothermal crystallization in glassy Se80−xTe20Mx (M = Cd, Ge, Sb) alloys , 2005 .

[5]  S. Ovshinsky.  Reversible Electrical Switching Phenomena in Disordered Structures , 1968 .

[6]  Nonvolatile Memory Based on Phase Transition in Chalcogenide Thin Film , 1993 .

[7]  M. Hiramoto,et al.  Induction Time for Nucleation in Amorphous Silicon Films Prepared by Plasma CVD , 1988 .

[8]  R. Cahn,et al.  Glasses and amorphous materials , 1991 .

[9]  M. F. Kotkata,et al.  Amorphous-to-crystalline transitions in the system SxTexSe100−2x with x between 5 and 25 , 1985 .

[10]  D. Ielmini,et al.  Intrinsic Data Retention in Nanoscaled Phase-Change Memories—Part II: Statistical Analysis and Prediction of Failure Time , 2006, IEEE Transactions on Electron Devices.

[11]  Minoru Kumeda,et al.  Nonvolatile Memory Based on Phase Change in Se–Sb–Te Glass , 2003 .

[12]  Masakuni Suzuki,et al.  Nonvolatile Memory Based on Reversible Phase Transition Phenomena in Telluride Glasses , 1989 .

[13]  A. Pirovano,et al.  Analysis of phase distribution in phase-change nonvolatile memories , 2004, IEEE Electron Device Letters.

[14]  N. Yamada,et al.  Rapid‐phase transitions of GeTe‐Sb2Te3 pseudobinary amorphous thin films for an optical disk memory , 1991 .