Preparation of Ge2Sb2Te5 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. 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.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.