A 0.24μm PRAM Cell Technology Using N-Doped GeSbTe Films(Phase Change RAM)(<Special Section>New Era of Nonvolatile Memories)

概要

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We have integrated a phase change random access memory (PRAM), completely based on 0.24μm-CMOS technologies using nitrogen doped GeSbTe films. The Ge_2Sb_2Te_5(GST) thin films are well known to play a critical role in writing current of PRAM. Through device simulation, we found that high-resistive GST is indispensable to minimize the writing current of PRAM. For the first time, we found the resistivity of GST film can be controlled with nitrogen doping. Doping nitrogen to GST film successfully reduced writing current. A 0.24μm PRAM using N-doped GST films were demonstrated with writing pulse of 0.8mA-50ns for RESET and 0.4mA-100ns for SET. Also, the cell endurance has been enhanced with grain growth suppression effect of dopant nitrogen. Endurance performance of fully integrated PRAM using N-doped GST shows no fail bit up to 2E9 cycles. Allowing 1% failures, extrapolation to 85℃ indicates retention time of 2 years. All the results show that PRAM is one of the most promising candidates in the market for the next generation memories.
社団法人電子情報通信学会の論文
2004-10-01