The effect of thickness on texture of Ge₂Sb₂Te₅ phase-change films

Phase-change random access memory (PCRAM) has the advantages of nonvolatile, good scalability, high speed, low power, long life and compatibility with standard complementary metal oxide semiconductor (CMOS) process. The key material in PCRAM is phase-change material, which can greatly affect the performance of PCRAM device. Ge₂Sb₂Te₅ (GST) is the most mature phase-change material and has been studied most widely at present. In this paper, GST films with thickness of 500 nm, 100 nm, 50 nm and 20 nm were studied by scanning electron microscope (SEM)–electron backscattering diffraction (EBSD) technique. According to the experiments, it is found that the crystal grain size has a tendency to grow larger and the GST film has a more obvious < 0001 > texture as its thickness decreases. During this process, surface energy plays an increasingly important role with the decrease in GST film thickness. Finally, (0001) plane with the highest work function and lowest surface energy leads to visible Z < 0001 > texture corresponding to film thickness. These results of regularity are helpful as the semiconductor industry today has the need for PCRAM devices with higher density and smaller size.