Thin Solid Films, Vol.544, 107-111, 2013
Ga19Sb81 film for multi-level phase-change memory
We studied Ga19Sb81 film deposited on SiOx/Si(100) by RF co-sputtering using GaSb and Sb targets aiming for applications in multi-level phase-change memory. Crystallization temperature (T-x) is 228 degrees C-235 degrees C determined by electrical resistance versus temperature measurements at various heating rates. The dramatic resistance drop is attributed to increased carrier concentration based on Hall measurements. The films show p-type conduction behavior at all temperature regimes. The temperature for ten-year failure-time (T-10y) and the activation energy of crystallization (E-a) is 156 degrees C and 4.2 eV, respectively, as deduced using Arrhenius plots from as-deposited films. The two-step drop in resistance is attributed to the two-step phase formation as depicted by X-ray diffractometry. Density changes before and after crystallization is 5.3% (Ge2Sb2Te5: 9.5%) as analyzed by the X-ray reflectivity method. Memory switching is carried out by using test cells with a via hole size of 600 nm. Set and reset processes can be achieved by using pulse widths of 20-100 ns. The cycling test showed performance at least 10(4) set-reset times. Furthermore, two stable set states are routinely achieved by controlling set voltages. The two states can be operated at least 10(2) cycles steadily with resistance ratios similar to 5 and similar to 22 times, respectively. The two set states arise from the formation of two phases (Sb then GaSb) during set operations. (C) 2013 Elsevier B.V. All rights reserved.
Keywords:Multi-level memory;Phase-change memory;Crystallization temperature;X-ray reflectivity;Thermal stability