Phase Change Random Access Memory [PRAM] is one of the candidate for next generation memory due to its non-volitality, high speed, high density and compatibility with Si-based semiconductor process. Ge2Sb2Te5 [GST] thin film , an active layer in this device, is utilized because it has the well-known property of rapid crystallization without phase separation in erasable compact discs industry.
We investigated the difference of the character of the GST thin film with various sputtering methods. 100nm thick GST films were prepared with DC magnetron sputtering and RF magnetron sputtering for this experiment. XRF, XRD,SEM and four point probe measurement are used to analyze the electrical properties of these films.
As for the composition of the DC sputtered GST films, Te was insufficient from target composition, while the composition of RF sputtered GST films were almost same as target composition. The RF sputtered GST films were composed of hcp by 400°C annealing. On the other hand, the DC sputtered films were mixed-phase of fcc and hcp. The resistivity of DC Sputtered GST films was higher than RF sputtered film cause of poor crystallinity. The uniformity of RF sputtered film was better than DC sputtered film.