Novel material for nonvolatile ovonic unified memory (OUM)－Ag₁₁In₁₂Te₂₆Sb₅₁ phase change semiconductor

In this paper, Ag_11In_12Te_26Sb_51 phase change semiconductor films have been prepared by dc sputtering. The crystallization behaviour of amorphous Ag_11In_12Te_26Sb_51 thin films was investigated by using differential scanning calorimetry and x-ray diffraction. It was found that the crystallization temperature is about 483K and the melting temperature is 754.8K and the activation energy for crystallization, E_\rm a, is 2.07eV. The crystalline Ag_11In_12Te_26Sb_51 films were obtained using initializer. The initialization conditions have a great effect on the sheet resistance of Ag_11In_12Te_26Sb_51 films. We found that the effect of the initialization condition on the sheet resistance can be ascribed to the crystallinity of Ag_11In_12Te_26Sb_51 films. The sheet resistance of the amorphous (R_\rm amo) film is found to be larger than 1\times10^6\Omega and that of the crystalline (R_\rm cry) film lies in the range from about 10^3 to 10^4\Omega. So we have the ratio R_\rm amo/R_\rm cry=10^2\sim 10^3, which is sufficiently large for application in memory devices.