Ga19Sb81 film for multi-level phase-change memory

Abstract We studied Ga 19 Sb 81 film deposited on SiO x /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 °C–235 °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 °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% (Ge 2 Sb 2 Te 5 : 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 ~ 5 and ~ 22 times, respectively. The two set states arise from the formation of two phases (Sb then GaSb) during set operations.