Preparation of Ge 2 Sb 2 Te 5 Thin Film for Phase Change Random Access Memory by Magnetron Sputtering on Small Hole Patterns

Phase Change Random Access Memory [PRAM] is one of the candidates for next generation memory due to its non-volatility, high speed, high density and compatibility with Si-based semiconductor process. Ge 2 Sb 2 Te 5 [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. In order to integrate PRAM to beyond 512Mbit, a high writing current and degradation of cell transition at small cell size become a problem. To resolve these problem, Confined Cell structure PRAM was suggested. However, it was difficult to fill GST layer in a small hole with a conventional sputtering tool because a big overhang occurred. In this work, we prepared GST films on the small hole patterned wafer by a new concept sputtering tool which designed developed a new concept sputtering tool. The structure of GST film was observed with cross section SEM and the film composition was measured with XRF. It was observed an overhang was suppressed and a GST film was filled in a small hole with a new concept tool. In addition, the uniformity of the GST film composition was good at less than 1% in 200mm φ substrate.