Materials for phase-change memory with elevated temperature stability

Abstract

Thermal stability is one of the key issues in phase-change memory. We try to tackle it by developing new compositions based on Ga-Te-Sb system. Thermal stability is exemplified using Ga 18 Te 12 Sb 70 which shows crystallization-temperature (T x ) 248 C and activation energy of non-isothermal crystallization 5.9 eV. Films were isothermally soaked at 5 $ 30 C below T x to estimate the failure-time when electrical resistance dropped to a half of the original. Arrhenius plot attained using logarithm failure-time versus reciprocal temperature were extrapolated to the temperature corresponding to 10-year failure (T 10y ) as 183 C. Pre-crystallization structure upon heating to 2 $ 5 C below T x reflects stable amorphous phase of the alloy up to at least 240 C. Memory-cells made of Ga 18 Te 12 Sb 70 can be set-reset at 20 $ 500 ns with electrical currents around 66% those of our Ge 2 Sb 2 Te 5 cells. We suggest that compositions Ga 18-25 Te 8-12 Sb 67-70 are optimal to ensure T x > 240 C, T 10y > 180 C and with low operation-currents. V C 2012 American Institute of Physics.

Superlattice-like SnSb4/Ga3Sb7 thin films for ultrafast switching phase-change memory application

“…The nucleation is not predominant, but grains grow gradually from the nuclei [14]. As is known, the nucleation needs much more time than grain growth [18]. Therefore, the crystallization will begin from rich Sb nuclei and the interfaces between different phase-change layers.…”

“…The crystallization fraction v is assumed to be proportional to resistance change. The crystallization fraction v at any given time can be redrawn and normalized by [18,19]:…”

High speed and low power consumption of superlattice-like Ge/Sb70Se30 thin films for phase change memory application

“…Figure 2b shows the Kissinger's plots of ln[(dT/dt)/T c 2 ] versus 1/T c curve for the GST, SbSe, [Ge(8 nm)/SbSe(5 nm)] 8 , [Ge(16 nm)/SbSe(5 nm)] 5 thin films. The activation energy E a for each film was calculated from the slope of the straight line in the corresponding Kissinger's plot [15]. The E a of SLL [Ge(8 nm)/SbSe(5 nm)] 8 and [Ge(16 nm)/ SbSe(5 nm)] 5 films were 2.93 and 3.84 eV, respectively, which were both larger than that of GST (2.43 eV) and SbSe (2.85 eV).…”

Alx(Sn2Se3)1−x phase change films for high-temperature data retention and fast transition speed application

“…The crystallization temperature increases with increasing of heating rate because there is insufficient time for crystallization. The activation energy for crystallization is calculated from a Kissinger plot [20]:…”

“…In this work, we assume the crystallization fraction v is proportional to resistance change and the curves in Fig. 1 can be redrawn and normalized [18,20]. The crystallization fraction v at any given time is determined by [22]:…”