A 0.24 µm PRAM Cell Technology Using N-Doped GeSbTe Films

Hideki HORII  Jeong Hee PARK  Ji Hye YI  Bong Jin KUH  Yong Ho HA  

IEICE TRANSACTIONS on Electronics   Vol.E87-C   No.10   pp.1673-1678
Publication Date: 2004/10/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on New Era of Nonvolatile Memories)
Category: Phase Change RAM
PRAM,  phase change,  GeSbTe,  CMOS,  memory,  N-doped,  chalcogenide,  

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We have integrated a phase change random access memory (PRAM), completely based on 0.24 µm-CMOS technologies using nitrogen doped GeSbTe films. The Ge2Sb2Te5 (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 0.24 µm PRAM using N-doped GST films were demonstrated with writing pulse of 0.8 mA-50 ns for RESET and 0.4 mA-100 ns 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.